On Membrane Motor Activity and Chloride Flux in the Outer Hair Cell: Lessons Learned from the Environmental Toxin Tributyltin

AbstractThe outer hair cell (OHC) underlies mammalian cochlea amplification, and its lateral membrane motor, prestin, which drives the cell's mechanical activity, is modulated by intracellular chloride ions. We have previously described a native nonselective conductance (GmetL) that influences OHC motor activity via Cl flux across the lateral membrane. Here we further investigate this conductance and use the environmental toxin tributyltin (TBT) to better understand Cl-prestin interactions. Capitalizing on measures of prestin-derived nonlinear capacitance to gauge Cl flux across the lateral membrane, we show that the Cl ionophore TBT, which affects neither the motor nor GmetL directly, is capable of augmenting the native flux of Cl in OHCs. These observations were confirmed using the chloride-sensitive dye MQAE. Furthermore, the compound's potent ability, at nanomolar concentrations, to equilibrate intra- and extracellular Cl concentrations is shown to surpass the effectiveness of GmetL in promoting Cl flux, and secure a quantitative analysis of Cl-prestin interactions in intact OHCs. Using malate as an anion replacement, we quantify chloride effects on the nonlinear charge density and operating voltage range of prestin. Our data additionally suggest that ototoxic effects of organotins can derive from their disruption of OHC Cl homeostasis, ultimately interfering with anionic modulation of the mammalian cochlear amplifier. Notably, this observation identifies a new environmental threat for marine mammals by TBT, which is known to accumulate in the food chain

A Two-Channel Patch-Clamp System on a Chip

The public emergency enactment, 1917. The quarantine and prevention of disease enactment, 1903

Intercellular communication in the supporting cells of the organ of Corti.

We have directly tested the concept that the supporting cells of the organ of Cortt are functionally coupled through gap junctions. In vitro and in viva preparations were evaluated. Electrical measurements clearly show that the cells are coupled ionically. Voltage drops measured in neighboring cells in response to intracellular current injections indicate that current spread decays rapidly. Despite the existence of electrical coupling, fluorescent dye injection studies revealed no dye spread into adjacent cells. other than a few instances which were clearly artifactual. However, it is possible that dye spread is very slow and that dye in adjacent cells is diluted below visual detectability. In any case. dye coupling is remarkably pcwr compared to other electrically coupled tissues. The role of coupling m the supporting cells may he nutritive, considering the avascular nature of Corti's organ

Um olhar caleidoscópico sobre as representações culturais de corpo

Esta dissertação trata das representações culturais de corpo, dentro do campo dos Estudos Culturais, em uma perspectiva pós-estruturalista que incorpora as contribuições de Michel Foucault acerca do discurso e da constituição do sujeito. O material empírico foi constituído a partir de uma pesquisa fundada em pressupostos etnográficos (observação-participante), realizada em uma sala de aula de ciêndas de um curso de supletivo de primeiro grau, noturno, voltado para o atendimento de trabalhadores/as metalúrgicos/as. A análise consistiu em problematizar alguns dos discursos que operaram na constituição dos corpos destes sujeitos, buscando dissecar/tornar visíveis as práticas de significação que os constituíram. O diário de campo cunhado durante minha estada junto a este grupo foi analisado com um texto (discurso), do qual extraí, como resultado das sucessivas operações que realizei a partir dos referenciais teóricos empregados, três eixos de análise. Eles dizem respeito às temáticas relacionadas a "corpo e gênero" (a beleza feminina como um modo de constituir a mulher, por dentro e por fora), a "corpo e 'raça'" (a supremacia branca que se encarna nos corpos/identidades negros/as) e a "corpo e trabalho" (visto a partir da repetição do movimento, do envelhecimento e da dor). Realizo, também, uma reflexão acerca das direções tomadas pelo trabalho ao longo de seu desenvolvimento e aponto as possíveis contribuições que ele pode oferecer para o estudo do corpo.This Essay refers to the cultural representations of the body in the fleld of Cultural Studies, in a post-structuralist perspective that includes Michel Foucault's contributions about the constitutions of the subject. The empiric material was developed throughout a research based on ethnographic presuppositions (observation - partidpant), which has taken place in a Science class of an elementary night course for steel workers (men and women). The analysis consisted of questioning some of the discourses that h ave intluenced in the constitution of these subjects, trying to make clear the signifying practices which have been part of them. The field diary made during the time I was studying this group was analyzed with a text (discourse) in which was a result of consecutive operations stemming from theoretical referentials used, three a~es of analysis. They have to do with the thematic referring to "body and gender" (the female beauty as a way of constituting the woman, inside and outside her), "body and race" (the white supremacy embodied in the bodies/negroes identities) and the "body and work" (from the point of view of movement repetition, aging and pain). I also reflect on the directions taken by the work over its development and point out possible contributions that it can offer to the study of the body

"A lighter black ... " Or of the discourses that fold themselves in the bodies producing what we are

Este artigo analisa representações culturais de corpo a partir da perspectiva dos Estudos Culturais. Tal campo de estudos possibilita o entendimento de que a educação se dá através de uma multiplicidade de espaços e produtos culturais, não se limitando à escola. O estudo aqui apresentado parte das observações realizadas em uma sala de aula de ciências de um curso supletivo para adultos/as trabalhadores/as metalúrgicos, para uma análise dos discursos (mídia, ciência, religião etc.) que vêm enfatizando a branquidade (a "raça branca") como a norma a ser seguida. O argumento principal é o de que as representações culturais hegemônicas (aqui, a de branquidade) apresentadas por estes diferentes discursos estão produzindo identidades negras dobradas à branquidade.This paper analyses cultural representations of body from the point of view of the Cultural Studies. Such perspective facilitates the understanding that the education is developed through a multiplicity of spaces and cultural products, not limited to the school. This study stems from the observations accomplished in a classromof Sciences of a course for adults/workers/steel workers, for an analysis of the discourses (media, science, religion etc.) that has been emphasizing the whiteness (the "white race") as the norm to be proceeded. The main argument is that the hegemonic cultural representations (here, the one of whiteness) presented by these different discourses are producing black identities folded to the whiteness

Stria Vascularis Dysfunction in a Mouse Model of Mitochondrial Hearing Loss

We recently described a transgenic mouse model of hearing loss induced by over-expression of the mitochondrial ribosomal RNA (rRNA) methyltransferase, TFB1M (Tg-TFB1M). These mice recapitulate maternally inherited deafness caused by the human A1555G mtDNA mutation, which results in increased methylation of the 12S rRNA in mitochondrial ribosomes and tissue-specific susceptibility to apoptosis. The present study aims to identify the specific cellular and tissue based pathologies underlying this form of deafness