1,721,290 research outputs found
Hydrochlorothiazide enhances the apical Cl- backflux in rabbit gallbladder epithelium : Radiochemical analysis
No full textHydrochlorothiazide(HCTZ) was shown to inhibit the transepithelial NaCl transport and the apical Na+-Cl– symport and to depolarize the apical membrane potential in the rabbit gallbladder epithelium. The depolarization was likely related to the opening of a Cl– conductance. To better understand whether an apical Cl– leak is involved in the mechanism of action of HCTZ, the transapical Cl– backflux was measured radiochemically by the washout technique. The gallbladder wall, pretreated with pronase on the serosal side to homogenize the subepithelium, was loaded with 36Cl– on the luminal side; mucosal and serosal 36Cl– effluxes (J m , J s ) were then measured every 2 min. The pretreatment with pronase did not alter the membrane potentials and the selectivity of the epithelium. Under control conditions and the tissue in steady-state, J m and J s time courses were each described by two exponential decays (A,B); the rate constants, k A and k B , were 0.71 ±0.03 and 0.16±0.01 min–1, respectively, and correspondingly the half-times (t 1 2A , t 1 2B ) were 1.01±0.05 and 5.00±0.44 min (n=10); these parameters were not significantly different for J m and J s time courses. J s was always greater than J m (J s /J m =2.02±0.22 and 1.43 ±0.17 for A and B decays). Under SCN– treatment in steady-state conditions, both J m and J s time courses were described by only one exponential decay, the component B being abolished. Moreover t 1 2A was similar to that predictable for the subepithelium. It follows that it is the component B which exits the epithelial compartment. Based on the intracellular specific activity and 36Cl– J m B at 0 min time of the washout experiment, the cell-lumen Cl– backflux in steady-state was calculated to be equal to about 2 mgrmol cm–2hr–1, in agreement with the value indirectly computable by other techniques. The experimental model was well responsive to different external challenges (increases in media osmolalities; luminal treatment with nystatin). HCTZ (2.5 · 10–4 m) largely increased 36Cl– J m B . The increase was abolished by luminal treatment with 10–4 m SITS, which not only brought back the efflux time courses to the ones observed under control conditions but even increased J s /J m of the cellular component, an indication of a reduced J m B . It is concluded that HCTZ opens an apical, SITS-sensitive Cl– leak, which contributes to dissipate the intracellular Cl– accumulation and to inhibit the NaCl transepithelial transport. Moreover, the drug is likely to reduce the basal electroneutral Cl– backflux supported by Na+-Cl– cotransport, in agreement with the inhibition of the cotransport itself
Sodium salt neutral entry at the apical membrane of the gallbladder epithelium: comparing different species
No full textUso di microparticelle su cui sono stati adsorbiti una proteina ed un anticorpo per preparare una composizione farmaceutica somministrabile per via intranasale
No full textUso di una microparticella polimerica, su cui sono stati previamente adsorbiti una proteina ed un anticorpo, per preparare una composizione farmaceutica somministrabile per via intranasal
Use of microparticles having a protein and an antibody adsorbed thereon for preparing a pharmaceutical composition for intranasal administration
No full textUse of a microparticle having a protein and an antibody adsorbed thereon for preparing a pharmaceutical composition for intranasal administratio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Endocytosis of polypeptides in the nasal respiratory mucosa of the rabbit
No full textThe nasal respiratory mucosa of the rabbit has a leaky epithelium actively transporting polypeptides by a specific transcytosis probably involved in sampling antigens. The transfer displays saturation kinetics and is abolished by metabolic inhibitors, actin filamet and microtubule disassemblers, inhibitors of vesicle fusion, and receptor recycling;it accepts polypeptide-covered but not uncovered nanoparticles
Hydrochlorothiazide action on the apical Cl−, Ca2+ and K+ conductances in rabbit gallbladder epithelium. Presence of an apamin-sensitive, Ca2+-activated K+ conductance
No full textIn the rabbit gallbladder epithelium, hydrochlorothiazide (HCTZ) was shown to inhibit the transepithelial NaCl transport and the apical Na(+)-Cl- symport, to depolarize the apical membrane potential and to enhance the cell-to-lumen Cl- backflux (radiochemically measured), this increase being SITS-sensitive. To better investigate the causes of the depolarization and the Cl- backflux increase, cells were punctured with conventional microelectrodes on the luminal side (incubation in bicarbonate-free saline at 27 degrees C) and the apical membrane potential (Vm) was studied either with prolonged single impalements or with a set of short multiple impalements. The maximal depolarization was of 3-4 mV and was reached with 2.5 x 10(-4) M HCTZ. It was significantly enhanced by reducing luminal Cl- concentration to 30 mM; it was abolished by SCN-, furosemide, SITS; it was insensitive to DPC. SITS converted the depolarization into a hyperpolarization of about 4 mV; this latter was apamin, nifedipine and verapamil sensitive. It was concluded that HCTZ concomitantly opens apical Cl- and (probably) Ca2+ conductances and, indirectly, a Ca(2+)-sensitive, apamin inhibitable K+ conductance: since the intracellular Cl- activity is maintained above the value predicted at the electrochemical equilibrium, the opening of the apical Cl- conductance depolarizes Vm and enhances Cl- backflux. In the presence of apamin or verapamil, to avoid the hyperpolarizing effects due to HCTZ, the depolarization elicited by this drug was fully developed (7-10 mV) and proved to be Ca2+ insensitive. On this basis and measuring the transepithelial resistance and the apical/basolateral resistance ratio, the Cl- conductance opened by HCTZ has been estimated and the Cl- backflux increase calculate: it proved to be in the order of that observed radiochemically. The importance of this Cl- leak to the lumen in the overall inhibition of the transepithelial NaCl transport by HCTZ has been evaluated
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