No description available.

No description available.

The auditory brainstem is comprised of a number of synapses specialized for the transmission of high-fidelity synaptic signals. Within the first three postnatal weeks, these pathways acquire the ability to process high-frequency signals without compromising timing information. However, little is known regarding developmental adaptations which confer this ability. Situated in the sound localization pathway, the calyx of Held-medial nucleus of the trapezoid body synapse provides an ideal model for investigating such adaptations as both the pre- and postsynaptic neurons are accessible to electrophysiological experimentation. Using this synapse, we have shown herein that the spatial coupling between voltage-gated calcium channels (VGCCs) and synaptic vesicles (SVs) tightens during development. Immature synapses use a loosely-coupled arrangement of many N- and P/Q-type VGCCs (“microdomain” modality) while mature synapses use a tightly-coupled arrangement of fewer P/Q-type VGCCs, to release SVs (“nanodomain” modality). As a consequence of this tightening, synaptic delay (SD) shortens. By fluorescence- and electron microscopy of SVs near active zones, we further identified the filamentous protein septin 5 as a molecular substrate, differentiating the two release modalities, which may act as a spatial barrier separating VGCCs and SVs in immature synapses. Finally, we have demonstrated that changes in release modality affect the nature of short-term plasticity observed at this synapse. Using trains of action potentials as presynaptic voltage-commands, we showed that, downstream of calcium influx, the microdomain modality promotes short-term facilitation in excitatory postsynaptic currents (IEPSC), and calcium-dependent decreases in SD, with these being absent in synapses employing the nanodomain modality. In contrast, we found that as a result of depletion of SVs, short-term depression of IEPSC dominates in synapses using the nanodomain modality, and correlates with calcium-dependent increases in SD. These findings imply that the type of release modality has a significant impact on the strength and timing of synaptic responses. The microdomain modality imparts greater dynamic range in timing and strength, but does so at the cost of efficiency and fidelity, while the nanodomain modality is a key accomplishment consolidating the high-fidelity abilities of this synapse.

The auditory brainstem is comprised of a number of synapses specialized for the transmission of high-fidelity synaptic signals. Within the first three postnatal weeks, these pathways acquire the ability to process high-frequency signals without compromising timing information. However, little is known regarding developmental adaptations which confer this ability. Situated in the sound localization pathway, the calyx of Held-medial nucleus of the trapezoid body synapse provides an ideal model for investigating such adaptations as both the pre- and postsynaptic neurons are accessible to electrophysiological experimentation. Using this synapse, we have shown herein that the spatial coupling between voltage-gated calcium channels (VGCCs) and synaptic vesicles (SVs) tightens during development. Immature synapses use a loosely-coupled arrangement of many N- and P/Q-type VGCCs (“microdomain” modality) while mature synapses use a tightly-coupled arrangement of fewer P/Q-type VGCCs, to release SVs (“nanodomain” modality). As a consequence of this tightening, synaptic delay (SD) shortens. By fluorescence- and electron microscopy of SVs near active zones, we further identified the filamentous protein septin 5 as a molecular substrate, differentiating the two release modalities, which may act as a spatial barrier separating VGCCs and SVs in immature synapses. Finally, we have demonstrated that changes in release modality affect the nature of short-term plasticity observed at this synapse. Using trains of action potentials as presynaptic voltage-commands, we showed that, downstream of calcium influx, the microdomain modality promotes short-term facilitation in excitatory postsynaptic currents (IEPSC), and calcium-dependent decreases in SD, with these being absent in synapses employing the nanodomain modality. In contrast, we found that as a result of depletion of SVs, short-term depression of IEPSC dominates in synapses using the nanodomain modality, and correlates with calcium-dependent increases in SD. These findings imply that the type of release modality has a significant impact on the strength and timing of synaptic responses. The microdomain modality imparts greater dynamic range in timing and strength, but does so at the cost of efficiency and fidelity, while the nanodomain modality is a key accomplishment consolidating the high-fidelity abilities of this synapse.

No description available.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-02-03T12:05:23Z No. of bitstreams: 1 alencarmirandaamaral.pdf: 1670327 bytes, checksum: 2d9c3f9a9d891835776120bfdbe35f33 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-02-03T12:07:46Z (GMT) No. of bitstreams: 1 alencarmirandaamaral.pdf: 1670327 bytes, checksum: 2d9c3f9a9d891835776120bfdbe35f33 (MD5) / Made available in DSpace on 2017-02-03T12:07:46Z (GMT). No. of bitstreams: 1 alencarmirandaamaral.pdf: 1670327 bytes, checksum: 2d9c3f9a9d891835776120bfdbe35f33 (MD5) Previous issue date: 2007-08-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta dissertação de mestrado analiso o contato inter-religioso promovido pela atuação de missões evangélicas (SIL e MNTB) junto à comunidade indígena Maxakali, localizada no nordeste do Estado de Minas Gerais. Além de acompanhar o desenvolvimento das atividades proselitistas destas instituições entre os índios Maxakali, objetivamos compreender como ao longo do contato inter-religioso ocorre o processo de identificação do Deus cristão com o personagem indígena Topa. Na bibliografia sobre os índios Maxakali, Topa aparece como o personagem central do “mito de criação” do grupo, e apesar de alguns autores reconhecerem que seu nome também era associado ao Deus cristão, não existem análises sobre este processo. Assim, nosso desafio será compreender como Topa foi, e vêm sendo, apropriado de diferentes maneiras ao longo do contato entre os Maxakali e os missionários evangélicos; e também analisar o processo que possibilitou que este personagem gradativamente fosse identificado com o Deus cristão. O escopo desta pesquisa é, portanto, perceber o esforço missionário de inserir o Deus cristão ao contexto Maxakali através do personagem Topa. A partir da análise de mitos Maxakali e hinos evangélicos traduzidos para o idioma do grupo buscaremos compreender este processo de associação, e também a (in)adequação dos ensinamentos missionários aos padrões sócioculturais e religiosos dos índios Maxakali. / In this master’s dissertation, I analyze the pro inter-religious contact heard by acts of evangelic missions (SIL and MNTB) on the Maxakali Indian at the northeast of Minas Gerais. Besides of studying the proselytizes activities of this institutions among the Maxakali Indians, we have the goal to understand how the Indians started to associate Topa (the Indian character) as the Christian God during this inter-religious contact. In the Maxakali biography, Topa come as the central character of the “creation myth” of the group an despite of the fact that some authors recognize Topa as the Christian God in their works, that are no analysis about it. So the challenge here is to understand how Topa was used in so many ways during the contact between the Maxakali and the evangelic missionaries; and analyze the process the made possible this character to be gradually associated with the Christian God. Hence, the purpose of this research is to realize the missionary effort to introduce the Christian God in the Maxakali context through Topa. From the analysis of the Maxakali myths an evangelic religions songs translated to their idiom, we will try understand the association process, and also how (in)adequate were the Christian teaching to the Maxakali religious and social-cultural standards.