Extracellular magnesium and anticonvulsant effects of valproate in young rat hippocampus

Extracellular field potential recordings were made in CA3 subfield of hippocampal slices from rats aged 11-22 days. In these experiments, we analyzed the effects induced by modifying [Mg2+] in the medium (1 or 2 mM) on (a) 4-aminopyridine (4-AP, 50 microM)-induced synchronous events (including ictal- and interictal-like epileptiform discharges as well as gamma-aminobutyric acid (GABA)-mediated potentials), and (b) the changes induced by the antiepileptic drug (AED) valproate (VPA 2 mM) on such activities. Changing [Mg2+] from 1 to 2 mM induced age-dependent effects consisting of reduction in rate of occurrence of ictal-like discharges at 11-13 days (55% reduction, p < 0.005) and 14-16 days (46% reduction, p < 0.025) postpartum. At any age, the rate of occurrence and the amplitude of the GABA-mediated synchronous potentials tended to decrease in 1 mM [Mg2+]. Similar effects were noted when changes in [Mg2+] were made during continuous application of the competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor DL-2-amino-5-phosphonovalerate (APV 50 microM). As previously reported, interictal and ictal discharges were blocked by addition of VPA to medium containing 2 mM [Mg2+]. Such an effect was not observed when [Mg2+] was decreased to 1 mM. In 1 mM, but not in 2 mM [Mg2+], VPA increased the amplitude of GABA-mediated synchronous potentials. Our results indicate that [Mg2+] plays a role in modulating occurrence of 4-AP-induced ictal activity and that it can influence the effects of VPA in this in vitro model of epileptogenesis.(ABSTRACT TRUNCATED AT 250 WORDS

Signalisation et implication de BMP-7 dans l'invasion cellulaire et la carcinogenèse colique

Nous avons démontré par RT-PCR, immunohistochimie, et en ELISA que BMP-7 et ses récepteurs sont présents dans des cryptes coliques histologiquement normales, les foci de cryptes aberrantes dans la sigmoïdite, les tumeurs colorectales humaines et plusieurs lignées de cellules cancéreuses coliques. Nous avons aussi démontré que BMP-7 est un facteur de dissémination inducteur du scattering et de l invasion cellulaire dans le collagène de type I. Le pouvoir invasif de BMP-7 est indépendant de SMAD4 et de l oncogène src, mais associé à l activation diffe rentielle et cyclique des GTPases (Rac1 et RhoA), de la tyrosine kinase FAK (phosphorylation de la tyr925 impliquée dans la signalisation invasive et l angiogenèse), et des MAPK/SAPK (JNK et ERK1/2). L ensemble de ces travaux suggère que BMP-7 se comporte comme un facteur de dissémination proinvasif, agissant par un mécanisme autocrine et paracrine au niveau des cellules cancéreuses du côlon et du stroma tumoral. Cette cytokine exerce donc des actions divergentes sur la progression des tumeurs coliques humaines, en s opposant aux processus inflammatoires transitoires (rôle bénéfique), mais en favorisant la néoplasie lors des étapes plus tardives associées à l acquisition du pouvoir invasif à la transition adénome- carcinome pendant la cancérogenèse (rôle péjoratif)PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Syndrome de Noonan et mutations du gène PTPN11 (corrélations génotype-phénotype)

Le syndrome de Noonan est une affection d origine génétique de transmission autosomique dominante, associant dysmorphie, retard de croissance, retard mental et syndrome polymalformatif dont l atteinte la plus classique est la sténose valvulaire pulmonaire. La fréquence estimée est de 1/2500 à 1/1000 naissances. PTPN11 est le gène majeur de la maladie, en cause chez environ 40% des patients. L objectif de ce travail a été l évaluation du rapport génotype-phénotype sur une grande série de patients et la comparaison avec les données de la littérature. Dans un premier temps une étude moléculaire a été réalisée afin de caractériser la fréquence et la localisation des mutations qui sont groupés au niveau de points chauds et responsables d un gain de fonction. Puis une analyse comparative des différents traits caractéristiques du syndrome de Noonan a été conduite entre le groupe des patients mutés et le groupe des patients non mutés. Cette étude a mis en évidence une corrélation positive entre la présence de mutation et certains signes (sténose valvulaire pulmonaire, communication inter-auriculaire, anomalie morphologique des oreilles, retard d âge osseux, cryptorchidie). D autres symptômes étaient par contre corrélés négativement à la présence de mutation (périmètre crânien, anomalies lymphatiques). Enfin une étude de la dysmorphie sur photographie a également été conduite et a démontré une fréquence plus importante de mutation chez les patients typiques. Cette étude a donc permis de mieux caractériser les corrélations entre le phénotype des patients et la présence de mutation du gène PTPN11Noonan syndrome is an autosomal dominant genetic disorder characterized by dysmorphic facial features, short stature, developmental delay and multiple malformations (most commonly pulmonic stenosis). Its prevalence has been estimated as 1/2500 to 1/1000 live births. PTPN11 is the major gene responsible of the disease and account for nearly 40% of the patients. The aim of this study was to assess genotype-phenotype relationships on a large cohort of patients with Noonan Syndrome and to make a review of former studies. First, a mutation analysis of PTPN11 was performed on the patients to characterize their frequency and repartition. Most of the mutational events occur in hot spots and are supposed to result in a gain of function. Then, we made a comparative analysis of the features of Noonan Syndrome between patients with mutation and without mutation. This study showed a positive correlation between some features and PTPN11 mutations (pulmonic stenosis, atrial septal defect, ear anomalies, bone age retardation, undescended testes). Other signs were negatively correlated with PTPN11 mutations (head circumference, lymphatic anomalies). Finally a study of dysmorphic features were performed on photographs and showed that typical patients had a higher frequency of mutations. This study has allowed to better characterize the association between phenotype of the patients and mutations on PTPN11PARIS12-CRETEIL BU Médecine (940282101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

On the synchronous activity induced by 4-aminopyridine in the CA3 subfield of juvenile rat hippocampus

1. Extracellular field potential and intracellular recordings were made in the CA3 subfield of hippocampal slices obtained from 10- to 24-day-old rats during perfusion with artificial cerebrospinal fluid (ACSF) containing the convulsant 4-aminopyridine (4-AP, 50 microM). 2. Three types of spontaneous, synchronous activity were recorded in the presence of 4-AP by employing extracellular microelectrodes positioned in the CA3 stratum (s.) radiatum: first, inter-ictal-like discharges that lasted 0.2-1.2 s and had an occurrence rate of 0.3-1.3 Hz; second, ictal-like events (duration: 3-40 s) that occurred at 4-38 x 10(-3) Hz; and third, large-amplitude (up to 8 mV) negative-going potentials that preceded the onset of the ictal-like events and thus appeared to initiate them. 3. None of these synchronous activities was consistently modified by addition of antagonists of the N-methyl-D-aspartate (NMDA) receptor to the ACSF. In contrast, the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 2-10 microM) reversibly blocked interictal- and ictallike discharges. The only synchronous, spontaneous activity recorded in this type of medium consisted of the negative-going potentials that were abolished by the GABAA receptor antagonists bicuculline methiodide (5-20 microM) or picrotoxin (50 microM). Hence they were mediated through the activation of the GABAA receptor. 4. Profile analysis of the 4-AP-induced synchronous activity revealed that the gamma-aminobutyric acid (GABA)-mediated field potential had maximal negative amplitude in s. lacunosum-moleculare, attained equipotentiality at the border between s. radiatum and s. pyramidale, and became positive-going in s. oriens. These findings indicated that the GABA-mediated field potential presumably represented a depolarization occurring in the dendrites of CA3 pyramidal cells. 5. This conclusion was supported by intracellular analysis of the 4-AP-induced activity. The GABA-mediated potential was reflected by a depolarization of the membrane of CA3 pyramidal cells that triggered a few variable-amplitude, fractionated spikes or fast action potentials. By contrast, the ictal-like discharge was associated with a prolonged depolarization during which repetitive bursts of action potentials occurred. Short-lasting depolarizations with bursts of action potentials occurred during each interictal-like discharge. 6. The GABA-mediated potential recorded intracellularly in the presence of CNQX consisted of a prolonged depolarization (up to 12 s) that was still capable of triggering a few fast action potentials and/or fractionated spikes.(ABSTRACT TRUNCATED AT 400 WORDS