(About: Miquel Missé, A la conquista del cuerpo equivocado, Editorial Egales)

Challenging the essentialist conception of transgendered people as “born in the wrong body,” Miquel Missé proposes a sociology of the body that emphasizes the burden of social norms.

Miquel Missé es un sociólogo español militante y una figura reco-nocida en el medio LGBT de Barcelona, en vista de su prolífica participación en los debates relativos a las personas transgénero. Su más reciente libro surge de un malestar: "siento la extraña sensación de que me han robado el cuerpo […] que nos lo han arrebatado a las personas trans en general" (p. 11). A partir del análisis de este malestar, el autor cuestiona el relato dominante sobre la identidad transgénero.

Ce travail s’intéresse à la population trans MtF latino-américaine issue des secteurs populaires. Le travail a pour objectifs de (1) connaître les normes de genre du milieu d’origine de cette population (2) comprendre le lien du milieu d’origine avec leur parcours dans l’identité trans (3) examiner les parcours migratoires et comprendre leur très forte inscription dans la prostitution. L’enquête de terrain a été réalisée principalement en France et en Espagne. Concernant le cheminement identitaire, la recherche montre le poids de la formation sociale du milieu d’origine, et particulièrement le poids des normes relatives au genre dans les milieux populaires (hétéronormativité, homophobie, sanction des masculinités déviantes). Cette imbrication classe/sexe situe les personnes dans la position sociale marginale et stigmatisée de la prostitution. L’article apporte un éclairage sur cet environnement, où l’imaginaire festif côtoie l’ordinaire des violences. L’expérience migratoire, très valorisée dans le pays d’origine, est examinée. Le type de liens tissés avec la famille, et les difficultés liées à l’isolement linguistique et à la solitude sont abordés.

In Arabidopsis suspension cells a rapid plasma membrane depolarization is triggered by abscisic acid (ABA). Activation of anion channels was shown to be a component leading to this ABA-induced plasma membrane depolarization. Using experiments employing combined voltage clamping, continuous measurement of extracellular pH, we examined whether plasma membrane H 1 -ATPases could also be involved in the depolarization. We found that ABA causes simultaneously cell depolarization and medium alkalinization, the second effect being abolished when ABA is added in the presence of H 1 pump inhibitors. Inhibition of the proton pump by ABA is thus a second component leading to the plasma membrane depolarization. The ABA-induced depolarization is therefore the result of two different processes: activation of anion channels and inhibition of H 1 -ATPases. These two processes are independent because impairing one did not suppress the depolarization. Both processes are however dependent on the [Ca 21 ] cyt increase induced by ABA since increase in [Ca 21 ] cyt enhanced anion channels and impaired H 1 -ATPases. ; fax 33-1-44-27-78-13.

In cirrhosis, in splanchnic arteries, endothelium-dependent relaxation may persist even if overactive nitric oxide synthase (NOS) and cyclooxygenase (COX) are inhibited. In normal arteries, a significant endothelium-dependent relaxation to acetylcholine persists after NOS/COX inhibition. This relaxation is caused by smooth muscle cell (SMC) membrane hyperpolarization, which is sensitive to a combination of the potassium channel blockers apamin and charybdotoxin, and is mediated by an endothelium-derived hyperpolarizing factor (EDHF). The aim of this study was to detect EDHF and evaluate its pathophysiologic role in isolated superior mesenteric arteries from cirrhotic rats. Arterial rings were obtained and exposed toNw -nitro-L-arginine (L-NNA, a NOS inhibitor) and indomethacin (a COX inhibitor). Acetylcholine-induced membrane potential responses and concentration-response curves to the relaxant of acetylcholine were obtained with and without apamin plus charybdotoxin. Acetylcholine-induced responses were measured in certain rings from endothelium-denuded arteries. Contractions caused by the α1 -adrenoceptor agonist phenylephrine were obtained in cirrhotic and normal rings with and without apamin and charybdotoxin. Significant acetylcholine-induced, endothelium-dependent, apamin- and charybdotoxin-sensitive, SMC membrane hyperpolarization and relaxation were found. An apamin- and charybdotoxin-sensitive hyporesponsiveness to the contractile action of phenylephrine was found in cirrhotic rings. In conclusion, in cirrhotic rats, in the superior mesenteric artery exposed to NOS/COX-inhibitors, an EDHF exists that may replace NOS/COX products to induce endothelium-dependent arterial relaxation.(Hepatology 2000;32:935-941.)

HrpN, the hypersensitive response elicitor from Erwinia amylovora, stimulated K + outward rectifying currents in Arabidopsis thaliana suspension cells. It also decreased anion currents. These data demonstrate the ability of harpin to regulate different plasma membrane ion channels, putative components of signal transduction chains leading to defense responses and programmed cell death. ß

Nod factor [NodRm-IV(Ac,S)], isolated from the bacterium Rhizobium meliloti, induces a well-known depolarization in Medicago sativa (cv Sitel) root hairs. Analysis of this membrane response using the discontinuous single-electrode voltage-clamp technique (dSEVC) shows that anion channel, K+ channel and H+-ATPase pump currents are involved in young growing root hairs. The early Nod-factor-induced depolarization is due to increase of the inward ion current and inhibition of the H+ pump. It involved an instantaneous inward anion current (IIAC) and/or a time-dependent inward K+ current (IRKC). These two ion currents are then down-regulated while the H+ pump is stimulated, allowing long-term rectification of the membrane potential (Em). Our results support the idea that the regulation of inward current plays a primary role in the Nod-factor-induced electrical response, the nature of the ions carried by these currents depending on the activated anion and/or K+ channels at the plasma membrane.

Vacuoles were isolated from leaves of Kalanchoë daigremontiana Hamet et Perrier de la Bathie, and the ionic sensitivity of the vacuolar ATPase was studied in vacuole homogenates desalted on Sephadex G-25. The ATPase activity was dependent on the presence of divalent cations (Mg2+≥ Mn2+≥ Ca2+, Co2+; Zn2+ had no effect). Mg2+-dependent ATPase activity was stimulated by anions (Cl− > malate2+, HCO−3), with maximal stimulation at concentrations above 50 mM. Mg2+-Dependent activity was inhibited by NO−3 above 2 mM, but no saturation was observed up to 100 mM. No stimulation by K+ or Na+ was detected; stimulation by NH+4 was abolished by 0.01% (w/v) Triton X-100, suggesting that the NH+4 effect was due to the permeability of vacuolar membrane vesicles to NH3.Trans-tonoplast electrical potentials (Δψ) and intra-vacuolar pH were measured with glass microelectrodes and antimony covered glass micro-pH-electrodes, respectively. Free vacuofes isolated from Kalanchoë tubiflora (Harv.) Hamet were slightly positive with respect to the suspension medium. This Δψ was insensitive to the protonophore FCCP and depolarized by about 4 mV on addition of 50 mM KCl, still remaining about +5 mV. Upon addition of 7 mM Mg-ATP, vacuoles showed an FCCP-sensitive increase of Δψ from +9.2 ± 2.8 (13) to +17.8 ± 3.7 (12) mV [given as x̄± sd (n)] and an internal acidification from pH 5.4 ± 0.2 (11) to pH 4.3 ± 0.4 (12). Mg-ADP and ATP without Mg2+ had no effect on Δψ.It is concluded that the H4 pumping at the tonoplast is due to the functioning of the anion-sensitive vacuolar ATPase and that this is an essential part of the mechanism of nocturnal acid accumulation in CAM.

Protein kinase C (PKC) modulates the activity and phosphorylation of the catalytic α-subunit of sodium-potassium-adenosine triphosphatase (Na+/K+ ATPase) in normal arteries. Because PKC is altered in cirrhotic aortae, Na+/K+ ATPase may also be altered in these arteries. The aim of the present study was to investigate α-subunit activity and phosphorylation in aortae from normal and cirrhotic rats, under baseline conditions and during exposure to PKC modulators. α-Subunit activity was assessed by measuring the amount of 32P released by hydrolysis of [γ-32P]ATP in freshly isolated cell membranes (in the absence of PKC modulators only) and membrane depolarization caused by ouabain-induced α-subunit inhibition in isolated aortae (in the absence and presence of PKC modulators). α-Subunit phosphorylation was assessed by incorporation of 32P into α-subunits. Staurosporine, a PKC inhibitor, and phorbol 12,13-dibutyrate (PDBU), a PKC activator, were used. In addition, α-subunit expression was studied by Western blot analysis. In the absence of PKC modulators, the amount of 32P released by hydrolysis of [γ-32P]ATP and ouabain-induced membrane depolarization were significantly lower in cirrhotic than in normal aortae. Staurosporine suppressed ouabain-induced membrane depolarization in cirrhotic and normal arteries. Ouabain-induced membrane depolarization was similar in cirrhotic aortae exposed to PDBU and in normal arteries studied under baseline conditions. α-Subunit phosphorylation was significantly lower in cirrhotic than in normal aortae, in aortae under baseline conditions, and in arteries exposed to staurosporine. Phosphorylation of the α-subunit was similar in cirrhotic aortae exposed to PDBU and in normal arteries under baseline conditions. Western blot analysis showed that the amount of α-subunit did not significantly differ between cirrhotic and normal aortae. In conclusion, a decrease in baseline Na+/K+ ATPase α-subunit activity occurs in aortae from cirrhotic rats as a result of reduced basal PKC activity. This PKC-dependent decreased α-subunit activity may be caused by a reduction in PKC-induced α-subunit phosphorylation.

Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant development and especially with cell expansion. Here we report that two BRs, 28-homobrassinolide (HBL) and its direct precursor 28homocastasterone (HCS), promote cell expansion of Arabidopsis thaliana suspension cells. We also show that cell expansions induced by HBL and HCS are correlated with the amplitude of the plasma membrane hyperpolarization they elicited. HBL, which promoted the larger cell expansion, also provoked the larger hyperpolarization. We observed that membrane hyperpolarization and cell expansion were partially inhibited by the proton pump inhibitor erythrosin B, suggesting that proton pumps were not the only ion transport system modulated by the two BRs. We used a voltage clamp approach in order to find the other ion transport systems involved in the PM hyperpolarization elicited by HBL and HCS. Interestingly, while anion currents were inhibited by both HBL and HCS, outward rectifying K + currents were increased by HBL but inhibited by HCS. The different electrophysiological behavior shown by HBL and HCS indicates that small changes in the BR skeleton might be responsible for changes in bioactivity.

Root hairs are a primary site for nutrient absorption and for initiation of signalling processes linked to variations of the root environment:plant-microbe interactions or abiotic changes. In many of these cases, the earliest detectable response is the modification of plasma membrane transports, detected through alteration of the electrical membrane potential. In spite of this, root hairs have not been extensively used in electrophysiological research so far. Problems with cell shape and current coupling are often prohibitive for microelectrode voltage-clamp on intact root hairs. In the present study, these difficulties have been overcome and the ion channel currents are described for young root hairs from alfalfa seedlings (Medicago sativa cv Sitel). Electrophysiological and pharmacological studies indicated an inward rectifying K + time-dependent current. This current was sensitive to tetraethylammonium and Cs + (10 mM each). Two other currents never shown in root hairs were described: an outward rectifying time-dependent K + current, inhibited by tetraethylammonium and Cs + (10 mM each) allowing K + efflux under strong depolarizations and an instantaneous inward current identified as an anion current, inhibited by 4-acetamido-4'isothiocyanatostilbene-2,2'-disulfonic acid and anthracene-9-carboxylic acid (100 µM each). These results should contribute to the understanding of root hair development and of signalling processes in M. sativa root hairs. © 1999 Éditions scientifiques et médicales Elsevier SAS

Little is known about the early response of roots to desiccation. Young growing root hairs of Arabidopsis thaliana, Vigna unguiculata and Phaseolus vulgaris were used to study the early response of roots to desiccation since they behave like sensors that are able to perceive environmental signals. In control conditions, root hairs were polarized around −120 mV and displayed inward rectifying K+ currents. When submitted to short-term desiccation, root hairs stopped their tip growth and their membrane became depolarized. Under these conditions, the K+ influx carried by the inward rectifying K+ channels was not maintained and instead slow deactivating anion channels were recorded. The inhibition of K+ influx and the large anion efflux due to the activation of slow anion currents could participate in the inhibition of tip growth.

Erwinia amylovora is a necrogenic bacterium that causes fire blight of the Maloideae subfamily of Roseacae, such as apple and pear. It provokes necrosis in aerial parts of susceptible host plants and the typical hypersensitive reaction in non-host plants. The secreted harpin, HrpNea, is able by itself to induce an active cell death in non-host plants. Ion flux modulations were shown to be involved early in such processes but very few data are available on the plasma membrane ion channel activities responsible for the pathogen-induced ion fluxes. We show here that HrpNea induces cell death in non-host Arabidopsis thaliana suspension cells. We further show that two cystic fibrosis transmembrane conductance regulator modulators, glibenclamide and bromotetramisole, can regulate anion channel activities and HrpNea-induced cell death.

Background/Aims: In vivo studies have shown that arterial vasodilation induced by synthetic openers of ATP-sensitive K+ (KATP) channels is decreased in rats with cirrhosis. Since vasodilation induced by these substances is mediated by membrane potential hyperpolarization in arterial smooth muscle cells, membrane potential hyperpolarization in response to KATP channel openers may be altered in cirrhotic smooth muscle cells. The aim of the present study was to investigate the effects of KATP channel modulators (i.e. openers and blockers of these channels) on the membrane potential in smooth muscle cells in isolated aortae from cirrhotic and normal rats. The influence of endothelin-1 production by endothelial cells on smooth muscle cells membrane potential responses to KATP channel modulators was also studied.Methods: Cells were impaled in situ (in intact and endothelium-denuded aortae) with a microelectrode that was used to measure membrane potentials. KATP channel openers were diazoxide or cromakalim; blockers were glibenclamide or tolbutamide. Bosentan (a mixed endothelin receptor antagonist) and exogenous endothelin-1 were also used. Preproendothelin-1 mRNA was assayed in aortae by RNase protection assay. Aortic wall endothelin-1 concentration was measured by double antibody radioimmunoassay technique.Results: As expected, in smooth muscle cells in intact normal aortae, KATP channel openers induced membrane potential hyperpolarization and KATP channel blockers membrane potential depolarization. In smooth muscle cells in intact cirrhotic aortae, KATP channel openers and blockers did not significantly change the membrane potential. Endothelium removal or exposure of intact aortae to bosentan restored normal membrane potential responses to KATP channel modulators in cirrhotic smooth muscle cells and did not alter the effects of these substances in normal smooth muscle cells. In endothelium-denuded aortae, exposure to exogenous endothelin-1 suppressed membrane potential responses to KATP channel modulators. In intact aortae, the abundance of preproendothelin-1 mRNA and endothelin-1 did not significantly differ between normal and cirrhotic rats.Conclusions: KATP channel opener-induced membrane hyperpolarization and KATP channel blocker-elicited membrane depolarization are blunted in smooth muscle cells in intact cirrhotic aortae. This blunting is due to the activation of the endothelin-1 pathway in the aortic wall, downstream to the endothelial production of endothelin-1.

HIV-1 gp120/gp160 is known to disturb the activity of p56lck, protein kinase C (PKC) and Ca2+ homeostasis in T lymphocytes. We found that gp160 decreases the Kv1.3 current of Jurkat E6.1 cells probably by increasing the PKC-dependent phosphorylation of Kv channel protein after 5 days. This decrease is dose-dependent. In contrast, gp160 did not decrease the Kv1.3 current of the JCaM1.6 cell line, a p56lck-defective Jurkat cell line. This shows that p56lck was at the beginning of the events which induced the Kv1.3 current decrease. As a consequence of this decrease, Jurkat E6.1 cells were depolarized and exhibited a volume increase.