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M Paquet

Publications and source records attributed to M Paquet.

At least 19 recordsLinked to original sources
PubMed2004

[Factors predictive of uterine rupture after operative hysteroscopy].

OBJECTIVES: To identify factors predictive of uterine rupture after operative hysteroscopy. When these factors are present, to search for means to prevent a later uterine rupture. Lastly to specify criteria allowing extraction of the fetus before rupture. PATIENTS AND METHODS: Dramatic description of a case of uterine rupture, in a patient who presented a history of uterine perforation secondary to operative hysteroscopy and retrospective analysis of 12 similar observations reported in the literature. RESULTS: Two types of situations must be differentiated: uncomplicated hysteroscopic resection of a polyp or sub-mucous fibroid does not seem to modify the obstetrical outcome; metroplasty for uterine malformation, complex synechia resections, and uterine perforations using monopolar current section are high-risk situations predictive of uterine rupture during pregnancy. CONCLUSION: Uterine ruptures secondary to operative hysteroscopy are rare but serious. They can occur before onset of labor, and compromise vital maternofetal outcome. Risk factors can be identified, but nothing can prevent natural history towards uterine rupture during pregnancy. The obstetrician's vigilance in this context must be extreme searching for the least clinical sign in favor of a pre-rupture of the uterus. Furthermore, systematic caesarean is not justified.

Adult↗
PubMed2001

beta 1-adrenergic receptor association with the synaptic scaffolding protein membrane-associated guanylate kinase inverted-2 (MAGI-2). Differential regulation of receptor internalization by MAGI-2 and PSD-95.

The beta1-adrenergic receptor (beta1AR) is known to be localized to synapses and to modulate synaptic plasticity in many brain regions, but the molecular mechanisms determining beta1AR subcellular localization are not fully understood. Using overlay and pull-down techniques, we found that the beta1AR carboxyl terminus associates with MAGI-2 (membrane-associated guanylate kinase inverted-2), a protein also known as S-SCAM (synaptic scaffolding molecule). MAGI-2 is a multidomain scaffolding protein that contains nine potential protein-protein interaction modules, including 6 PDZ domains, 2 WW domains, and a guanylate kinase-like domain. The beta1AR carboxyl terminus binds with high affinity to the first PDZ domain of MAGI-2, with the last few amino acids of the beta1AR carboxyl terminus being the key determinants of the interaction. In cells, the association of full-length beta1AR with MAGI-2 occurs constitutively and is enhanced by agonist stimulation of the receptor, as assessed by both co-immunoprecipitation experiments and immunofluorescence co-localization studies. Agonist-induced internalization of the beta1AR is markedly increased by co-expression with MAGI-2. Strikingly, this result is the opposite of the effect of co-expression with PSD-95, a previously reported binding partner of the beta1AR. Further cellular experiments revealed that MAGI-2 has no effect on beta1AR oligomerization but does promote association of beta1AR with the cytoplasmic signaling protein beta-catenin, a known MAGI-2 binding partner. These data reveal that MAGI-2 is a specific beta1AR binding partner that modulates beta1AR function and facilitates the physical association of the beta1AR with intracellular proteins involved in signal transduction and synaptic regulation.

Activin Receptors, Type II↗
PubMed2001

Differential subcellular localization of mGluR1a and mGluR5 in the rat and monkey Substantia nigra.

Neurons in the rat substantia nigra (SN) are enriched in group I metabotropic glutamate receptor (mGluR) subtypes and respond to group I mGluR activation. To better understand the mechanisms by which mGluR1 and mGluR5 mediate these effects, the goal of this study was to elucidate the subsynaptic localization of these two receptor subtypes in the rat and monkey substantia nigra. At the light microscope level, neurons of the SN pars reticulata (SNr) displayed moderate to strong immunoreactivity for both mGluR1a and mGluR5 in rats and monkeys. However, mGluR1a labeling was much stronger in monkey than in rat SN pars compacta (SNc) neurons, whereas a moderate level of mGluR5 immunoreactivity was found in both species. At the electron microscope level, the immunoreactivity for both group I mGluR subtypes was primarily expressed postsynaptically, although light mGluR1a labeling was occasionally seen in axon terminals in the rat SNr. Immunogold studies revealed a striking difference in the subcellular distribution of mGluR1a and mGluR5 immunoreactivity in SNr and SNc neurons. Although the bulk of mGluR1a was attached to the plasma membrane, >80% of mGluR5 immunoreactivity was intracellular. Plasma membrane-bound immunoreactivity for group I mGluRs in both SNc and SNr neurons was mostly extrasynaptic or in the main body of symmetric, putative GABAergic synapses. On the other hand, asymmetric synapses either were nonimmunoreactive or displayed perisynaptic labeling. These data raise important questions about the trafficking, internalization, and potential functions of group I mGluRs at extrasynaptic sites or symmetric synapses in the substantia nigra.

Animals↗
PubMed2001

Ionotropic and metabotropic GABA and glutamate receptors in primate basal ganglia.

The functions of glutamate and GABA in the CNS are mediated by ionotropic and metabotropic, G protein-coupled, receptors. Both receptor families are widely expressed in basal ganglia structures in primates and nonprimates. The recent development of highly specific antibodies and/or cDNA probes allowed the better characterization of the cellular localization of various GABA and glutamate receptor subtypes in the primate basal ganglia. Furthermore, the use of high resolution immunogold techniques at the electron microscopic level led to major breakthroughs in our understanding of the subsynaptic and subcellular localization of these receptors in primates. In this review, we will provide a detailed account of the current knowledge of the localization of these receptors in the basal ganglia of humans and monkeys.

Animals↗
PubMed2000

Presynaptic NMDA receptor subunit immunoreactivity in GABAergic terminals in rat brain.

N-methyl-D-aspartate (NMDA) receptors are commonly found post-synaptically; they mediate fast excitatory neurotransmission in the central nervous system. In this study, we provide immunocytochemical data supporting the existence of presynaptic NMDA receptors in GABAergic terminals using polyclonal antisera raised against the C-terminus of the NMDAR1 subunit. At the light microscope level, rich plexuses of NMDAR1-positive varicose fibers were found in various nuclei in the basal forebrain (bed nucleus of stria terminalis, septum, parastrial nucleus, vascular organ of the lamina terminalis), thalamus (paraventricular nucleus, midline nuclei), and hypothalamus (parvocellular paraventricular nucleus, arcuate nucleus, preoptic nucleus, suprachiasmatic nucleus). In the brainstem, labeled fibers were much less abundant and were confined to the ventral tegmental area, periaqueductal gray, parabrachial nucleus, and locus coeruleus. At the electron microscope level, NMDAR1-immunoreactive terminals examined in the bed nucleus of stria terminalis, parvocellular paraventricular hypothalamic nucleus, and arcuate nucleus formed symmetric synapses, contained darkly stained large dense-core vesicles, and displayed gamma-aminobutyric acid (GABA) immunoreactivity. Terminals with similar ultrastructural features were found in the paraventricular thalamic nucleus. These findings demonstrate the existence of NMDAR1 subunit immunoreactivity in subsets of GABAergic terminals, which raises questions about the potential roles and mechanisms of activation of presynaptic NMDA heteroreceptors in the rat central nervous system. The pattern of distribution and ultrastructural features of these boutons suggest that they may arise from local GABAergic projections interconnecting a group of brain structures mediating stress responses and/or other endocrine, autonomic, and limbic functions.

Animals↗
PubMed2000

GABA(B) and group I metabotropic glutamate receptors in the striatopallidal complex in primates.

Glutamate and GABA neurotransmission is mediated through various types of ionotropic and metabotropic receptors. In this review, we summarise some of our recent findings on the subcellular and subsynaptic localisation of GABA(B) and group I metabotropic glutamate receptors in the striatopallidal complex of monkeys. Polyclonal antibodies that specifically recognise GABA(B)R1, mGluR1a and mGluR5 receptor subtypes were used for immunoperoxidase and pre-embedding immunogold techniques at the light and electron microscope levels. Both subtypes of group I mGluRs were expressed postsynaptically in striatal projection neurons and interneurons where they aggregate perisynaptically at asymmetric glutamatergic synapses and symmetric dopaminergic synaptic junctions. Moreover, they are also strongly expressed in the main body of symmetric synapses established by putative intrastriatal GABAergic terminals. In the globus pallidus, both receptor subtypes are found postsynaptically in the core of striatopallidal GABAergic synapses and perisynaptically at subthalamopallidal glutamatergic synapses. Finally, extrasynaptic labelling was commonly seen in the globus pallidus and the striatum. Moderate to intense GABA(B)R1 immunoreactivity was observed in the striatopallidal complex. At the electron microscope level, GABA(B)R1 immunostaining was commonly found in neuronal cell bodies and dendrites. Many striatal dendritic spines also displayed GABA(B)R1 immunoreactivity. Moreover, GABA(B)R1-immunoreactive axons and axon terminals were frequently encountered. In the striatum, GABA(B)R1-immunoreactive boutons resembled terminals of cortical origin, while in the globus pallidus, subthalamic-like terminals were labelled. Pre-embedding immunogold data showed that postsynaptic GABA(B)R1 receptors are concentrated at extrasynaptic sites on dendrites, spines and somata in the striatopallidal complex, perisynaptically at asymmetric synapses and in the main body of symmetric striatopallidal synapses in the GPe and GPi. Consistent with the immunoperoxidase data, immunoparticles were found in the presynaptic grid of asymmetric synapses established by cortical- and subthalamic-like glutamatergic terminals. These findings indicate that both GABA and glutamate metabotropic receptors are located to subserve various modulatory functions of the synaptic transmission in the primate striatopallidal complex. Furthermore, their pattern of localisation raises issues about their roles and mechanisms of activation in normal and pathological conditions. Because of their 'modulatory' functions, these receptors are ideal targets for chronic drug therapies in neurodegenerative diseases such as Parkinson's disease.

Animals↗
PubMed1999

Apparent dopamine D1 and D2 receptors in the weaver mutant mouse: receptor binding and coupling to adenylyl cyclase.

Weaver mutant mice have a selective degeneration of the nigrostriatal dopamine pathway arising between 7-21 days after birth. The goal of this study was to investigate the effects of this mutation on different parameters of the nigrostriatal and mesolimbic dopamine system: apparent D1 and D2 receptor binding sites as well as their signal transduction pathway. Using quantitative autoradiography of ligands for dopamine D1, D2 receptors and the dopamine uptake site, we found a significant loss in apparent D1 receptor binding sites throughout the neostriatum, significant increase of apparent D2 receptor binding in the dorsal aspect of the neostriatum, and almost complete loss of DA uptake sites in these regions of the weaver mouse. In contrast to the neostriatum, the density of dopamine receptors and uptake sites in the nucleus accumbens of the weaver mouse did not differ from controls. Despite alterations in the binding of apparent D1 and D2 receptors, there was no significant difference in either basal, DA stimulated or GTPgammaS stimulated cAMP production. These findings suggest the down-regulation of apparent D1 receptor binding sites reported in this model, probably does not reflect an important physiological mechanism through which these animals compensate for loss of dopamine innervation.

Adenylyl Cyclases↗
PubMed1998

Cocaine- and amphetamine-regulated transcript (CART) peptide immunoreactivity in myenteric plexus neurons of the rat ileum and co-localization with choline acetyltransferase.

Cocaine and amphetamine regulated transcript (CART) encodes a novel brain-enriched protein whose features are reminiscent of a neurotransmitter propeptide. We have now localized CART peptide(s) in the gastrointestinal tract by immunohistochemical methods. Polyclonal antisera raised to CART peptide 106-129 stained neuronal cell bodies and fibers in rat ileum myenteric plexus-longitudinal muscle tissue preparations. Electron microscopic analysis of thin sections showed immunopositive axon terminals in close apposition to CART-labelled and unlabelled neuronal cell bodies as well as to the longitudinal muscle. CART peptide-immunoreactive terminals contained numerous ovoid electron-lucent vesicles and a few dark-stained dense-core vesicles. Light microscopic double labelling studies revealed CART peptide immunoreactivity in a subpopulation of choline acetyltransferase (ChAT)-immunoreactive neurons. This combined light microscopic and ultrastructural examination of CART peptides in the gastrointestinal tract suggests a role of CART peptides as transmitters or neuromodulators in the peripheral nervous system.

Animals↗
PubMed1998

[Quality of data acceptable for perinatal epidemiology surveillance: assessment of the health certificate at birth and the national obstetrics medical file. Study in three Seine-Maritime maternal wards].

Data from several sources could be used for perinatal epidemiology surveillance aimed at an assessment of regional programs such as those proposed by the Superior Committee for Public Health. A retrospective study of 561 births was conducted in three maternity wards in the French Seine Maritime department in order to evaluate the reliability of two data sources: the national obstetrics medical file and the health certificate at birth. The delivery room records were used as the gold standard. The sensitivity of the obstetrics file was better than that of the health certificate. With the obstetrics file, it was possible to identify almost all the vaginal route interventions, almost all the premature births and all the cesareans. With the health certificate, 39-58% of the vaginal route interventions, 61% of the premature births and 61-72% of the cesareans performed in the three wards studied were identified. The quality of data in the obstetrics file appears to be better than that in the health certificate but only concerns 40% of births in the geographical area studied. Inversely, the health certificate is theoretically delivered for all births (actually delivered for 93%). Integrating these two information systems could be an optimum solution.

Bias↗
PubMed1997

Primary structure and expression of a naturally truncated human P2X ATP receptor subunit from brain and immune system.

A novel member of the ionotropic ATP receptor gene family has been identified in human brain. This 422 amino acid long P2X receptor subunit has 62% sequence identity with rat P2X5. Several characteristic motifs of ATP-gated channels are present in its primary structure, but this P2X5-related subunit displays a single transmembrane domain. Heterologous expression of chimeric subunits containing the C-terminal domain of rat P2X5 leads to the formation of desensitizing functional ATP-gated channels in Xenopus oocytes. The developmentally regulated mRNA, found in two splicing variant forms, is expressed at high levels in brain and immune system.

Adult↗
PubMed1997

AMPA and NMDA glutamate receptor subunits in midbrain dopaminergic neurons in the squirrel monkey: an immunohistochemical and in situ hybridization study.

The objective of the present study was to analyze the cellular and subcellular localization of ionotropic glutamate receptor subunits in midbrain dopaminergic neurons in the squirrel monkey. This was achieved by means of immunohistochemistry at light and electron microscopic levels and in situ hybridization histochemistry. Colocalization studies show that nearly all dopaminergic neurons in both the ventral and dorsal tiers of the substantia nigra compacta (SNc-v, SNc-d) and the ventral tegmental area (VTA) are immunoreactive for AMPA (GluR1, GluR2/3, and GluR4) and NMDAR1 receptor subunits, but not for NMDAR2A/B subunits. The immunoreactivity of the receptor subunits is associated mainly with perikarya and dendritic shafts. Apart from the intensity of immunolabeling for the GluR4 subunit, which is quite similar for the different groups of midbrain dopaminergic neurons, the overall intensity of immunostaining for the other subunits is higher in the SNc-v and SNc-d than in the VTA. In line with these observations, in situ hybridization shows that the average level of labeling for the GluR2 and NMDAR1 subunit mRNAs is significantly higher in the SNc-v than in the VTA, and for the NMDAR1 subunit, higher in the SNc-v than in the SNc-d. In contrast, no significant difference was found for the level of GluR1 mRNA labeling among the three groups of midbrain dopaminergic neurons. At the subcellular level in the SNc-v, AMPA (GluR1 and GluR2/3) and NMDAR1 receptor subunit immunoreactivity is preferentially associated with the postsynaptic densities of asymmetric synapses, but occasionally some immunoreactivity is found along nonsynaptic portions of plasma membranes of dendrites. A small number of preterminal axons, axon terminals, and glial cell processes are also immunoreactive. Our observations indicate that the different groups of midbrain dopaminergic neurons in primates exhibit a certain degree of heterogeneity with regard to the level of expression of some ionotropic glutamate receptor subunits. The widespread neuronal and glial localization of glutamate receptor subunits suggests that excitatory amino acids may act at different levels to control the basal activity and, possibly, to participate in the degeneration of midbrain dopaminergic neurons in Parkinson's disease.

Animals↗
PubMed1997

One-stage midline unifocalization and complete repair in infancy versus multiple-stage unifocalization followed by repair for complex heart disease with major aortopulmonary collaterals.

BACKGROUND: Patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries have traditionally required multiple unifocalization staging operations before undergoing complete repair. Recently, the feasibility of a single-stage unifocalization and repair was demonstrated by Hanley. In this report, we describe our experience with each approach. METHODS AND RESULTS: Since 1989, 11 of 12 patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries have undergone complete surgical correction. The first seven patients were subjected to staged bilateral unifocalizations, with repair being achieved in six (group I). The last five patients have undergone a single-stage midline unifocalization and repair via a sternotomy (group II). Four of these were infants (2 weeks to 9 months) and one was 13 years old. All patients in group I had tetralogy of Fallot, whereas in group II three patients had tetralogy of Fallot, one patient had double-outlet right ventricle, and one patient had complete atrioventricular canal and transposition. In group I, the median age at the first operation was 43 weeks. Complete repair was performed at a median age of 3.5 years, with a mean number of 3.3 operations required. In group II, only one operation was required to achieve complete repair at a median age of 28 weeks. The postoperative right ventricular/left ventricular pressure ratio was 0.49 in group I and 0.45 in group II. One intraoperative death and one late death occurred in group I and no early or late deaths in group II. Currently, four patients in group I and all five patients in group II are alive and well. CONCLUSIONS: Early intervention with both surgical approaches can lead to complete biventricular repair in most patients. Because the single-stage midline unifocalization and repair can achieve a completely repaired heart in infancy with one operation, it is currently our approach of choice.

Aorta, Thoracic↗
PubMed1997

Identification in the rat neurotensin receptor of amino-acid residues critical for the binding of neurotensin.

In order to identify charged amino-acid residues of the cloned rat brain neurotensin (NT) receptor (NTR) that are critical for NT binding, we performed site-directed mutagenesis on the cDNA encoding this protein, followed by transient expression into mammalian COS-7 cells and in Xenopus laevis oocytes. Point substitutions of charged residues in the N-terminal part and in the 2nd and 3rd extracellular loop of the receptor either did not affect (125)I-Tyr3-NT binding or resulted in a decrease in binding affinity by a factor of 2-3. Mutations of amino acids Asp113 in the second transmembrane domain (TM) and of Arg149 or Asp150 in TM III yielded receptors that bound NT as efficiently as the native receptor. By contrast, replacement of the Asp139 residue in the 1st extracellular loop, or of Arg143 or Arg327-Arg328 residues at the top of TM III and in TM VI, respectively, completely abolished ligand binding. Confocal and EM immunocytochemical studies of the expression of these affected receptors, tagged with the C-terminal sequence of the vesicular stomatitis virus glycoprotein (VSV-G), indicated that this loss of binding was not due to altered receptor expression or to their improper insertion into the plasma membrane. When these mutated forms of neurotensin receptor were expressed into Xenopus oocytes, Asp139-Gly- and Arg143-Gly-modified receptors remained functional in spite of a lowered response to NT whereas the Arg327-Arg328 mutant form was totally insensitive to NT at concentrations up to 10 microM. In the case of the Arg327-Arg328 mutation, the observed insensibility to NT could be the result of a drastic conformational alteration of this mutant protein. By contrast, it would appear that Asp139 and Arg143 residues located in the first extracellular loop of the receptor may be directly involved in the interaction of the receptor with neurotensin.

Amino Acids↗
PubMed1997

Alterations in the turnover rate of dopamine D1 but not D2 receptors in the adult rat neostriatum after a neonatal dopamine denervation.

Adult rats that were treated with intracerebral ventricular injection of 6-hydroxydopamine (6-OHDA) as neonates exhibit a profound loss of nigrostriatal dopamine innervation in addition to a variety of other neurochemical and anatomical changes, including alterations in the number of neostriatal D1 and D2 receptor binding sites. In the present study, the turnover of neostriatal dopamine D1 and D2 receptors was measured in rats previously treated with 6-OHDA or ascorbic acid vehicle as neonates at various time intervals after peripheral N-ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinoline (EEDQ, 10 mg/kg) administration. Dopamine receptors were labelled with [3H]SCH23390 (D1) and [3H]raclopride (D2), while the degree of dopamine denervation was assessed by the measurement of neostriatal dopamine, homovanillic acid and dihydroxyphenylacetic acid content. Two days after acute EEDQ treatment, the maximal binding capacity (Bmax) of [3H]SCH23390 and [3H]raclopride binding was significantly decreased to 58 and 32% of control values, respectively, without any significant alteration in their equilibrium dissociation constants (Kd). A time-dependent increase in the density of [3H]SCH23390 and [3H]raclopride binding was observed in both treatment groups following a single dose of EEDQ. The rate of recovery of D1 receptors was significantly slower in the 6-OHDA-lesioned animals as compared to controls with a half-life of 103 compared to 53 h, respectively. No differences were observed in the rate of recovery of D2 receptors in these two treatment groups. These data are consistent with the findings of decreased expression of D1 receptors in neonatal 6-OHDA-lesioned rats owing to decreased receptor synthesis, and further suggest that in this model the up-regulation of D2 receptors is a result of a post-transcriptional mechanism, such as an increased rate of post-synthetic maturation.

Aging↗