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Biomedical subjects

T Fournier

Publications and source records attributed to T Fournier.

At least 37 records · Page 2Linked to original sources
PubMed1997

EndothelinA receptors in human uterine leiomyomas.

OBJECTIVE: To determine if there are endothelin receptors on human uterine leiomyomas. METHODS: Samples of leiomyomas from eight patients were analyzed for [iodine (I)-125]endothelin-1 binding. Several subtype-selective ligands were used to determine the endothelin receptor population. RESULTS: Binding of [125I]endothelin-1 to uterine leiomyoma membranes was specific and saturable, with a mean +/- dissociation constant 85.5 +/- 8.4 pM. Competition binding studies showed that the order of potency was endothelin-1 > endothelin-3, which was consistent with the presence of the endothelinA receptor subtype. Binding of [125I]endothelin-1 was displaced by an endothelinA-selective antagonist, but not by sarafotoxin 6c, an endothelinB-selective agonist. An endothelins-selective ligand was not specifically bound to leiomyoma. CONCLUSION: These results indicate that only endothelinA receptors are present in human uterine leiomyomas. We speculate that endothelin-1 may act through these endothelinA receptors to influence the development or regulation of hypertrophy and proliferation of the human myometrium during pregnancy and in uterine disorders like leiomyomas.

Adult↗
PubMed1997

IL-1 beta inhibits ET-1 production by ATII cells in vitro: evidence for involvement of cyclooxygenase 2 pathway.

The aim of this study was to characterize the effect of alveolar macrophage (AM) secretory products on endothelin (ET)-1 production by rat alveolar type II (ATII) cells in primary culture. We quantified preproendothelin (ppET)-1 mRNA by Northern blot and ET-1 concentrations in cell supernatants by enzyme-linked immunosorbent assay. Conditioned medium (CM) from rat adherent AM decreased the ppET-1 mRNA levels in ATII cells and reduced ET-1 concentrations in cell culture supernatants. This effect was mediated by interleukin (IL)-1 beta as shown by pretreatment of CM with an anti-IL-1 beta neutralizing antiserum. IL-1 beta effect was dependent on protein synthesis, was partially prevented with indomethacin, and was totally prevented with dexamethasone. Specific inhibition of cyclooxygenase 2 activity completely reversed the effect of IL-1 beta. We conclude that rat AM inhibit ET-1 production by rat ATII cells in vitro through IL-1 beta secretion. The IL-1 beta-mediated inhibition is dependent on the cyclooxygenase 2 pathway. Downregulation of ET-1 production by activated AM could limit the intra-alveolar burden of this profibrogenic peptide and thus could prevent fibrosis development.

Animals↗
PubMed1996

Induction of diaphragmatic nitric oxide synthase after endotoxin administration in rats: role on diaphragmatic contractile dysfunction.

Nitric oxide (NO), a free radical that is negatively inotropic in the heart and skeletal muscle, is produced in large amounts during sepsis by an NO synthase inducible (iNOS) by LPS and/or cytokines. The aim of this study was to examine iNOS induction in the rat diaphragm after Escherichia Coli LPS inoculation (1.6 mg/kg i.p.), and its involvement in diaphragmatic contractile dysfunction. Inducible NOS protein and activity could be detected in the diaphragm as early as 6 h after LPS inoculation. 6 and 12 h after LPS, iNOS was expressed in inflammatory cells infiltrating the perivascular spaces of the diaphragm, whereas 12 and 24 h after LPS it was expressed in skeletal muscle fibers. Inducible NOS was also expressed in the left ventricular myocardium, whereas no expression was observed in the abdominal, intercostal, and peripheral skeletal muscles. Diaphragmatic force was significantly decreased 12 and 24 h after LPS. This decrease was prevented by inhibition of iNOS induction by dexamethasone or by inhibition of iNOS activity by N(G)-methyl-L-arginine. We conclude that iNOS was induced in the diaphragm after E. Coli LPS inoculation in rats, being involved in the decreased muscular force.

Abdominal Muscles↗
PubMed1995

Endothelin ETA receptors mediate human uterine smooth muscle contraction.

Receptors mediating endothelin-induced contraction of myometrium were investigated in the human uterus. Endothelin-1 and endothelin-3 (10 pM to 0.3 microM) caused concentration-dependent contraction of myometrial strips. Endothelin-1 was approximately ten times more potent than endothelin-3, with pD2 values of 8.24 and 7.20, respectively. By contrast, two endothelin ETB receptor selective agonist, BQ 3020 (N-acetyl-[Ala11,15]endothelin-1-(6-21) and sarafotoxin 6c (up to 0.3 microM), did not induce contraction of human myometrium. The endothelin ETA receptor selective antagonist, FR139317 (1-hexahydroazepino-CO-Leu-D-Trp(CH3)-D-(2-pyridyl)alanine) (0.1, 0.3 and 1 microM), competitively antagonized the endothelin-1-elicited contraction, with a pA2 value of 7.10, whereas another endothelin ETA receptor-selective blocking drug, BQ 123 [cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu)], behaved as a non-competitive antagonist. Pretreatment of myometrial strips with an endothelin ETB receptor selective antagonist, IRL 1038 ([Cys11-Cys15]endothelin-1-(11-21)), had no effect on contractions induced by endothelin-1. All these data indicate that only endothelin ETA receptors mediate endothelin-1-induced contractions of human myometrium.

Adult↗
PubMed1995

Divergence in macrophage insulin-like growth factor-I (IGF-I) synthesis induced by TNF-alpha and prostaglandin E2.

Increased synthesis of insulin-like growth factor I (IGF-I), a fibroblast growth factor, is induced in murine macrophages by TNF-alpha. TNF-alpha also induces macrophages to express cytocidal activity, but only during costimulation with IFNs. Since prostaglandin E2 (PGE2) is known to inhibit macrophage cytocidal activity, its possible reciprocal enhancement of IGF-I synthesis was examined. PGE2 or dibutyryl cyclic AMP (dbcAMP) stimulated the synthesis of IGF-I similarly to TNF-alpha in magnitude and time course. TNF-alpha did not increase IGF-I synthesis by first inducing PGE2 synthesis, because indomethacin was unable to block the effect of TNF-alpha. PGE2 did not stimulate IGF-I synthesis by first inducing TNF-alpha production, because 1) anti-TNF-alpha Ab did not block PGE2-induced IGF-I synthesis, and 2) PGE2 down-regulated TNF-alpha mRNA levels and did not affect levels of the cytokine in supernatants. Moreover, the difference in the induction of IGF-I was observed at the level of signal transduction, in that PGE2 and dbcAMP increased cAMP-dependent protein kinase (PKA) activity, whereas TNF-alpha stimulated the mitogen-activated protein (MAP) kinase pathway. Divergence between the two pathways was also noted in the regulation of IGF-I at the mRNA level, and an additive effect on IGF-I synthesis was observed when cells were incubated with the combination of TNF-alpha plus PGE2 or dbcAMP. Collectively, these data suggest that TNF-alpha and PGE2 stimulate IGF-I synthesis in macrophages by two separate pathways, and that PGE2 acts as a positive stimulus for IGF-I synthesis through a cyclic AMP/PKA pathway.

Animals↗
PubMed1995

Myosin heavy chain isoform expression in human myometrium: presence of an embryonic nonmuscle isoform in leiomyomas and in cultured cells.

We had previously found no myosin heavy chain (MHC) changes in expression during pregnancy in human myometrium. In the present work, we compared the MHC pattern of expression in normal human myometrium, pregnant and non-pregnant, to that in benign tumors of the uterine musculature and in cultured myometrial cells. We used a high-resolution gel electrophoretic system and monoclonal antibodies directed against smooth muscle and nonmuscle MHCs. Smooth muscle MHCs (SM1, 204 kDa, and SM2, 200 kDa, MHCs) and a nonmuscle MHC of 196 kDa (NM MHC) were detected in pregnant and nonpregnant human myometrium. Pregnant myometrium was found to differ from nonpregnant myometrium by its slightly lower content in NM MHC, whereas the ratio of SM1/SM2 was equivalent. In leiomyomas and in cultured cells grown from human myometrium explants, SM1, SM2, and NM MHCs were also expressed. In addition, a nonmuscle MHC of 198/200 kDa (SMemb MHC), which was present in a fetal human uterus but not in adult normal tissue, was observed in leiomyomas and in cultured cells. Expression of SM1 and SM2 MHCs was variable in the different leiomyomas studied. In cultured cells, SM1 and SM2 MHC content was low, but it was enhanced by suppression of serum after cell confluency. Present results confirm that pregnancy-associated smooth muscle cell hypertrophy is not accompanied by major changes in MHCs. In contrast, cell culturing and cell hyperplasia leading to leiomyoma formation induce substantial modifications in MHCs, including the occurrence of a second type of nonmuscle MHC.

Actins↗
PubMed1995

Contractile proteins in human fetoplacental vessels.

OBJECTIVE: Our purpose was to compare the protein isoform composition of the contractile apparatus at different levels of the fetoplacental vessel musculature at term. STUDY DESIGN: Umbilical, chorionic, and stem villi vessel protein extracts were run on one- and two-dimensional gel electrophoresis; previously characterized human myometrium proteins were used as the smooth muscle proteins of reference. RESULTS: Fetoplacental vessel musculature exhibited a high actin/myosin ratio. The presence, in varying quantities, of myosin heavy chain and actin isoforms of smooth muscle type in the different vessels reflected their degree of differentiation. The presence of nonmuscle protein isoforms, particularly in stem villi vessels, indicated a certain degree of immaturity. CONCLUSIONS: The presence of smooth muscle contractile protein isoforms indicates that fetoplacental vessel musculature is highly differentiated. Regional modulation of fetoplacental blood flow could be, in part, the result of local differences in contractile apparatus protein composition.

Actins↗
PubMed1995

Characterization of type A endothelin receptors in cultured human myometrial cells.

The aim of the present study was to characterize endothelin (ET)-receptors in human myometrial cells in culture. 125I-labeled ET-1 binding to myometrial cells was specific and saturable, with a dissociation constant of 64.2 +/- 12.8 pM. Competition binding studies showed the following order of potency: ET-1 > ET-3, which is consistent with the presence of the ETA receptor subtype. FR-139317 and BQ-123, two ETA antagonists, both inhibited 125I-ET-1 binding. BQ-123 only elicited a partial inhibition. The fraction resistant to BQ-123 did not represent the ETB receptor subtype, since no specific 125I-ET-3 binding could be detected. ET-1 and ET-3 were found to stimulate [3H]inositol phosphate (IP) accumulation in cultured myometrial cells, with corresponding half-maximal effective concentration values of 0.26 +/- 0.04 and 87 +/- 17 nM, respectively. Both ETA antagonists inhibited ET-1-induced accumulation of [3H]IP. BQ-123 was only a partial inhibitor, whereas FR-139317 totally suppressed ET-1-stimulated production of [3H]IP. We conclude that human myometrial cells in culture exclusively possess ETA receptor subtypes coupled to phospholipase C.

Adult↗
PubMed1995

Involvement of endothelin receptor subtypes in human myometrial activity.

We investigated the contribution of endothelin (ET) ETA and ETB receptors to ET-induced contractions of human myometrium and their distribution in cultured myometrial cells. ET-1 was more potent than ET-3 in evoking concentration-dependent increases in smooth muscle tension. A selective ETB agonist, BQ 3020, was inactive in eliciting contractions. In myometrial cell membranes, no specific [125I]ET-3 binding was observed. Inhibition of [125I]ET-1 binding by unlabeled compounds showed the following order of potency: ET-1 = FR 139317 > ET-3 >> S6c. Furthermore, ET-1 increased inositol phosphate (IP) production in a dose-dependent manner. ET-1-induced IP accumulation was totally abolished by FR 139317 (an ETA-selective antagonist) but was not altered by IRL 1038 (an ETB-selective antagonist). These results indicate that only ETA receptors, which mediate ET-1-induced uterine contraction, are present in cultured myometrial cells.

Adult↗
PubMed1994

Separation and characterization of the main methylated nucleobases from nuclear, cytoplasmic and poly (A)+ RNA by high-performance liquid chromatography and mass spectrometry.

We were able to detect nine methylated nucleobases (3-methyluracil, 1-, 2-, 3- and 7-methylguanine, 1-, 2-, 3- and 6-methyladenine) in RNA from rat and calf liver, baker's yeast, Torula and Euglena cells by using reversed-phase high-performance liquid chromatography and thermospray mass spectrometry. Total cellular, nuclear, cytoplasmic and poly (A)+ RNA from rat liver showed marked methylation, mainly of 1- and 3- methylguanine, and 3- and 2-methyladenine. These bases were especially abundant in nuclear RNA and, to a lesser extent, in poly (A)+ RNA. In contrast, 7-methylguanine and 6-methyladenine were poorly represented in poly (A)+ RNA.

Animals↗
PubMed1994

Transcriptional regulation of rat alpha 1-acid glycoprotein gene by phenobarbital.

Phenobarbital induces gene transcription of both cytochrome P450IIB (the barbiturate-inducible cytochrome P450 in mammals) and alpha 1-acid glycoprotein, one of the major acute-phase proteins in rats and humans. Analysis of the 5'-regulatory sequences of cytochrome P450IIB and alpha 1-acid glycoprotein genes in rats revealed the presence of a consensus sequence of 10 base pairs, termed the phenobarbital-responsive element or Barbie box, located in a region extending from positions -136 to -127 from the transcription start site of the alpha 1-acid glycoprotein gene. A 17-base pair oligonucleotide probe specific for alpha 1-acid glycoprotein and including the consensus sequence showed, in mobility shift assays, slight binding to liver nuclear protein from untreated animals. This binding was strongly and specifically increased with protein extracts from phenobarbital-treated rats. Transfection of rat primary hepatocytes with the pAGPcat construct induced basal expression of chloramphenicol acetyltransferase activity, which was increased by phenobarbital and dexamethasone treatment of cells. Induction of chloramphenicol acetyltransferase activity by phenobarbital was abolished when hepatocytes were transfected by constructs with a mutation or deletion of the Barbie box sequence. These results strongly suggest that the Barbie box sequence is involved in alpha 1-acid glycoprotein gene regulation by phenobarbital.

Animals↗
PubMed1994

Induction of rat alpha-1-acid glycoprotein by phenobarbital is independent of a general acute-phase response.

Phenobarbital (PB) induces transcription of the alpha 1-acid glycoprotein (AGP) gene, one of the major positive acute-phase proteins, the expression of which is controlled by a specific combination of glucocorticoids and cytokines. This raises questions as to the involvement of glucocorticoids and cytokine pathways in the PB-mediated effect on AGP gene expression. We found that the pattern of whole-serum proteins in PB-treated rats differed markedly from that observed during a typical acute inflammatory response (in turpentine-treated rats): levels of some positive acute-phase proteins (APP) increased slightly (alpha 1-acid glycoprotein, haptoglobin, hemopexin and T-kininogen), while levels of alpha 2 macroglobulin, the most sensitive marker of the acute-phase reaction, decreased. Among the negative APP, neither albumin nor prealbumin decreased while CBG increased. The cytokines involved in AGP gene regulation (mainly IL1, IL6 and TNF alpha) do not therefore seem to mediate the effect of PB on acute-phase protein expression. Glucocorticoid involvement is also ruled out by the observed enhancement of the effect of PB on AGP expression in adrenalectomized animals. Our results suggest that phenobarbital acts on AGP expression by a mechanism independent of the inflammatory pathway.

Acute-Phase Reaction↗
PubMed1994

Phenobarbital induction of alpha 1-acid glycoprotein in primary rat hepatocyte cultures.

The serum level of rat alpha 1-acid glycoprotein is significantly increased by treatment with phenobarbital, and in vivo studies have shown that phenobarbital seems to act mainly at the transcriptional level. To show the direct mediating effect of phenobarbital on alpha 1-acid glycoprotein gene expression, we investigated the ability of primary cultured rat hepatocytes to respond to in vitro phenobarbital administration. Phenobarbital increased both alpha 1 acid glycoprotein secretion and corresponding mRNA levels in primary rat hepatocytes cultured on matrigel. Used in combination with interleukin-1, interleukin-6 and dexamethasone, phenobarbital had an additive or synergistic effect on alpha 1-acid glycoprotein synthesis. These results show that (a) phenobarbital acts directly on hepatocytes by increasing alpha 1-acid glycoprotein gene expression and (b) this effect is mediated by a specific mechanism independent of pathways involved in alpha 1-acid glycoprotein induction by interleukin-1, interleukin-6 and glucocorticoids.

Animals↗
PubMed1994

Endothelin receptors: binding and phosphoinositide breakdown in human myometrium.

Endothelin (ET) binding sites and phosphoinositide hydrolysis induced by ET peptides were studied in the nonpregnant human myometrium. Saturation binding experiments revealed that the proportion of [125I]ET-1 binding sites was 4-fold higher than that of [125I]ET-3 binding sites, whereas Kd values were not significantly different. In competition binding studies, unlabeled peptides displaced [125I]ET-1 binding with the following order of affinity ET-1 > sarafotoxin 6b > ET-3 >> sarafotoxin 6c, whereas very similar Ki values were obtained with the four peptides for the displacement of [125I]ET-3 binding. Approximately 75% of [125I]ET-1 binding sites exhibited high affinity to BQ 123 ([cyclo(D-Trp,D-Asp,L-Pro,D-Val,L-Leu)]), an ETA selective antagonist. ET-1 elicited a time-dependent accumulation of [3H]inositol phosphates in myometrial explants prelabeled with myo-[3H]inositol. All the peptides examined, ET-1, ET-3, sarafotoxin 6b and sarafotoxin 6c were able to induce phosphoinositide hydrolysis in a dose-dependent manner, ET-1 being more potent than ET-3 with corresponding EC50 values of 32 +/- 12 and 441 +/- 37 nM, respectively. Sarafotoxin 6c induced a moderate stimulation of inositol phosphates accumulation. ET-1- and ET-3-induced accumulation of [3H]inositol phosphates was (40-45%) inhibited in part by 100 microM BQ 123, whereas sarafotoxin 6c response was not affected by the ETA-antagonist. All these results indicate the presence of ETA and ETB receptors coupled to phospholipase C in human myometrium. Although ET-1 and ET-3 bind to both subtypes, sarafotoxin 6c only interacts with the ETB subtype.

Adult↗
PubMed1992

Evaluation of the hepatotoxicological effects of a drug in an in vivo/in vitro model.

Both in vivo and in vitro models have certain disadvantages for the study of the chronic hepatotoxicity of drugs. The aim of this work was to evaluate a new approach based on an in vivo/in vitro model. After chronic in vivo treatment of rats with Vincamine and Vindeburnol (an eburnamenine derivative which exhibits hepatotoxic properties in man) liver cells were isolated, and functional and metabolic disorders (metabolic utilization of fructose and protein biosynthesis) were studied to determine injury. The results showed no modification of blood parameters, but a direct relationship between the dose of Vindeburnol administered in vivo and the metabolic disorders observed in vitro, evidencing the high sensitivity and reliability of this model.

Animals↗
PubMed1992

Modifications of hepatic alpha-1-acid glycoprotein and albumin gene expression in rats treated with phenobarbital.

The serum level of alpha 1-acid glycoprotein (alpha 1-AGP) is significantly increased in various animal species by treatment with cytokines, glucocorticoids and phenobarbital. The mechanisms responsible for the cytokine-induced and glucocorticoid-induced increases are now well documented, but not so in the case of phenobarbital. The main purpose of this study was to assess whether phenobarbital acts on alpha 1-AGP synthesis in the liver at the transcriptional or translational level. Male Dark Agouti rats received 70 mg phenobarbital/kg daily for 7 days. The analysis of total hepatic RNA showed that a single injection of phenobarbital induced an 11-fold increase in phenobarbital-dependent cytochrome P450IIB mRNA, whereas seven injections of phenobarbital were required to induce a maximum 5.5-fold increase in alpha 1-AGP mRNA. Concurrently, the transcription rate of the alpha 1-AGP gene rose 3.5-fold. Hepatocytes isolated after the seventh injection of phenobarbital showed a threefold increased capacity to secrete alpha 1-AGP, corresponding to a 3.2-fold increased alpha 1-AGP mRNA content in the liver. In conditions in which its effect on the induction of alpha 1-AGP synthesis was maximum, phenobarbital caused a 30% reduction in liver albumin mRNA and in albumin secretion by isolated hepatocytes, resulting from a 60-70% reduction in the rate of transcription of the albumin gene measured in isolated nuclei. We conclude that the effect of phenobarbital on alpha 1-AGP and albumin gene expression occurs at the transcriptional rather than the translational level.

Albumins↗
PubMed1991

The effects of chronic ventromedial hypothalamic stimulation on weight gain in rats.

The effects of chronic stimulation of the ventromedial hypothalamus and adjacent structures on body weight, food intake, and epididymal fat pad weight were examined in normophagic rats. Three hours of intermittent low level electrical stimulation were delivered three times per week for four weeks; body weight and food intake were monitored for an additional ten days after stimulation trials had ceased. Animals receiving ventromedial hypothalamic stimulation had the shallowest growth curves while stimulation of other structures produced a rate of growth that fell between that of the ventromedial hypothalamic and the implanted control group. This pattern persisted during the poststimulation phase. Food intake, while initially depressed in the stimulated groups, began to approach control levels by the third week of stimulation. Efficiency of food utilization (weight gain/consumption) was significantly reduced during the first week of stimulation in the ventromedial hypothalamic stimulated group. Fat pad weight was slightly decreased in this group as well. These findings suggest that chronic stimulation of the ventromedial hypothalamus causes a persistent shift in metabolic rate that results in a long-term inhibition of weight gain.

Adipose Tissue↗