19 research outputs found
CARACTERISATION PHARMACOLOGIQUE ET FONCTIONNELLE DES RECEPTEURS DE L'UTP DANS L'OREILLE INTERNE DE VERTEBRES
No full textPARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF
PARA NOVAS COOPERAÇÕES ENTRE ESCOLAS E BIBLIOTECAS: RETORNO AOS OBJETIVOS E MISSÕES
No full textThis article aims to discuss the roles of the school and of the library, as well as the one of the cooperation between teachers and librarians, in the formation of readers. To this end, an overview of the recent history of public libraries and school libraries in France is presented. Furthermore, some academic research on reading developed by various areas of study is addressed. Finally, rather than highlighting the opposition and contradictory relationships between the library and the school, the author chooses to conclude by highlighting the potential of the partnership between the two of them.http://dx.doi.org/10.14572/nuances.v21i22.1620Este artigo tem como objetivo discutir os papéis da escola e da biblioteca, assim como o da cooperação entre professores e bibliotecários, na formação de leitores. Para tanto, parte-se de um breve panorama da história recente das bibliotecas públicas e das bibliotecas escolares na França. Em seguida, são retomadas algumas pesquisas acadêmicas sobre a leitura desenvolvidas por diversas áreas de estudo. Por fim, ao invés de destacar as oposições e relações contraditórias entre a biblioteca e a escola, o autor opta por concluir destacando as potencialidades da parceria entre as duas.http://dx.doi.org/10.14572/nuances.v21i22.162
Pharmacological characterization of ATP receptors in ampulla from frog semicircular canal
No full textPhosphoinositidase C activities sensitive to purine and pyrimidine nucleotides have been identified earlier in ampulla from Rana ridibunda semicircular canal. The aim of this study was to characterize the pharmacological properties of other P2receptors borne by this structure. A microassay was developed to measure the binding of [35S]adenosine 5′- O-(2-thiodiphosphate) ([35S]ADPβS) to a few ampullas microdissected from frog semicircular canals. When determined at 4°C in the absence of divalent cations, [35S]ADPβS binding was saturable with incubation time and reversible after elimination of free radioligand. The dissociation kinetics were biphasic and comprised a major component that was rapidly reversible and a minor component that dissociated slowly. [35S]ADPβS binding was competitively inhibited by unlabeled ADPβS with an apparent dissociation constant of 0.48 ± 0.09 μM and a Hill coefficient of 0.70 ± 0.06, and Scatchard analysis revealed a minor class of high-affinity binding sites (RT1= 52 ± 11 fmol [35S]ADPβS bound/ampulla and Kd1= 0.15 ± 0.04 μM) and a major class of low-affinity binding sites (RT2= 436 ± 79 fmol [35S]ADPβS bound/ampulla and Kd2= 2.0 ± 0.8 μM). The pattern of stereospecificity for recognition of unlabeled structural ATP analogs was ADPβS ≥ α,β-methyleneadenosine 5′-triphosphate = ADP = adenosine 5′- O-(3-thiotriphosphate) > ATP = diadenosine tetraphosphate = AMP > 2′- and 3′- O-(4-benzoylbenzoyl)-adenosine 5′-triphosphate ≥ 2-methylthioadenosine 5′-triphosphate > 2-desoxythymidine 5′-triphosphate = guanosine 5′-triphosphate = inosine-5′-triphosphate = xanthosine 5′-triphosphate = cytosine 5′-triphosphate = uridine 5′-triphosphate = uridine-5′-diphosphate, whereas cAMP and adenosine were devoid of activity. For antagonists, suramin revealed competitive inhibitor potencies, whereas reactive blue 2 and DIDS acted as pure noncompetitive inhibitors. Results suggest that the population of labeled receptors is heterogeneous and contains a low number of P2Y-like receptors and a large number of P2X-like receptors whose molecular subtypes and functions in endolymph homeostasis remain to be defined.</jats:p
UTP binding and phosphoinositidase C activation in ampulla from frog semicircular canal
No full textPyrimidine nucleotide-sensitive phosphoinositidase C activity (PLC), previously identified in frog semicircular canal ampulla, was pharmacologically characterized. Binding of [3H]UTP and abilities of unlabeled nucleotide analogs to inhibit binding and to stimulate PLC in myo-[3H]inositol-loaded ampullas were determined. Specific [3H]UTP binding was competitively inhibited by UTP [apparent dissociation binding constant = 0.8 μM; Hill coefficient = 0.7]. Scatchard analysis revealed a minor class of high-affinity binding sites [45 fmol UTP bound/μg protein; dissociation constant ( KD1) = 0.4 μM] and a major class of moderate-affinity binding sites (365 fmol UTP bound/μg protein; KD2= 10 μM). The stereospecificity pattern for UTP analog recognition was UMP > UDP ≥ ADP = UTP = dTTP > adenosine 5′- O-(3-thiotriphosphate) = ATP = CTP = 2′-and 3′- O-4-(benzoylbenzoyl)-ATP (Bz-ATP) ≥ AMP ≥ 2-methylthio-ATP = α,β-methylene-ATP > uridine = diadenosine tetraphosphate (Ap4A); cAMP and adenosine were inactive. Antagonist recognition pattern was DIDS = pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS) = reactive blue 2 > suramin. The rank order of potencies for agonist-induced PLC activation was UDP ≥ UTP ≥ Ap4A ≥ UMP = Bz-ATP; uridine was inactive. UTP-stimulated PLC activity was inhibited by DIDS = reactive blue 2 = PPADS > suramin. These results suggest that the population of [3H]UTP-labeled binding sites is heterogeneous, with a low number of high-affinity UTP receptors whose function(s) need to be determined and a large number of moderate-affinity receptors triggering PLC activation.</jats:p
Purine and pyrimidine nucleotide-sensitive phospholipase A<sub>2</sub>in ampulla from frog semicircular canal
No full textThis study was attempted to characterize pharmacologically the P2Y receptors triggering phospholipase A2(PLA2) activation in ampulla from frog semicircular canal. A microassay was developed to screen the abilities of UTP analogs to stimulate [3H]arachidonic acid release by labeled ampullas. At 26°C UTP induced a dose-dependent and saturable increase of PLA2activity (apparent activation constant 1.3 ± 0.4 μM, Hill coefficient 0.9 ± 0.2, maximal stimulating factor 2.0 ± 0.1). The rank order of potency of agonists for PLA2activation was UTP ≥ UDP > adenosine 5′- O-(2-thiodiphosphate) = adenosine 5′- O-(3-thiotriphosphate) ≥ ATP = 2-methylthio-ATP ≥ ADP = diadenosine tetraphosphate ≥ α,β-methylene-ATP = CTP > 2′ and 3′- O-(4-benzoylbenzoyl)-ATP ≥ AMP = UMP >> uridine and adenosine. UTP- and 2-methylthio-ATP-induced PLA2activations were inhibited by U-73122, GF-109203X, and methyl arachidonyl fluorophosphate. Basal activity was stimulated by phorbol ester and epinephrine and reduced by vasotocin, isoproterenol, prostaglandin E2, cAMP, and forskolin. H-89 restored the cAMP- and forskolin-inhibited PLA2activities. Results indicate that P2Y receptor-mediated PLA2stimulation requires phopholipase C and protein kinase C activations and basal activity is inhibited by agonist-stimulated cAMP-dependent mechanisms.</jats:p
Vasopressin, ATP and catecholamines differentially control potassium secretion in inner ear cell line.
No full textInternational audienceA strict control of endolymph composition (high potassium, low sodium fluid) and volume is instrumental for a proper functioning of the inner ear. Alteration of endolymph homeostasis is proposed in the pathogenesis of Menière's disease. However, the mechanisms controlling endolymph secretion remain elusive. By using the vestibular EC5v cells, we provide evidence for the presence of vasopressin, catecholamine and purinergic signaling pathways, coupled to adenylate cyclase, phosphoinositidase C and Ca(2+) activation. We demonstrate that vasopressin and catecholamines stimulate while ATP inhibits apical potassium secretion by EC5v cells. These results open new interesting perspectives for the management of inner ear diseases
Structural requirements for activation of vasopressin-sensitive adenylate cyclase, hormone binding and antidiuretic actions: effect of highly potent analogs and competitive inhibitors. Mol Pharmacol
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