No description available.

The epithelial sodium channel, ENaC, forms the rate-limiting step for sodium reabsorption in the cortical collecting duct of the kidney. It is known that ENaC is important in maintaining fluid homeostasis and ultimately blood pressure as mutations in ENaC result in inherited forms of hyper- and hypotension (Liddle's syndrome and Pseudohypoaldosteronism (PHA type I), respectively). Clinically, ENaC activity can be blocked by treatment with the potassium sparing diuretic amiloride. However, due to difficulties in dosing and the transient nature of channel block, treatment goals are seldom achieved. It is, therefore, necessary to better understand the function and regulation of ENaC activity. ENaC is a member of the DEG/ENaC family of ion channels. Each family member is composed of multiple subunits - each subunit contains two transmembrane domains, short cytoplasmic amino and carboxy termini, and a relatively large extracellular domain. ENaC is a heterotrimer of homologous subunits Α-,Β-, and ΓENaC. ENaC is a constitutively active ion channel. It is not ligand gated or voltage activated. However, channel activity can be modulated by a variety of stimuli. I hypothesize that the extracellular domain functions as a sensor, allowing the channel to detect and respond to changes in extracellular conditions. To test this, we expressed human ΑΒΓENaC in Xenopus oocytes and used the two-electrode voltage clamp technique to measure changes in ENaC activity in response to changing extracellular conditions. Using this technique, I identified several novel means of regulating ENaC activity. I found that ENaC activity can be rapidly and reversibly stimulated or suppressed in response to extracellular acidification depending on the balance of extracellular sodium and chloride concentrations and have identified several key residues involved. I found that extracellular chloride inhibits ENaC activity through putative binding sites in the extracellular domain located between the Α- and Β- and Β- and ΓENaC subunits. This allowed us to determine that ENaC adopts an ΑΓΒ channel architecture. Additionally, I have made progress in understanding channel movement by identifying length dependent intersubunit interactions that alter channel gating. Based on our data we conclude that the extracellular domain is integral to modulation of channel activity. The work described herein has significantly advanced the field by improving our understanding of ENaC structure and function.

No description available.

Made available in DSpace on 2017-07-10T17:37:56Z (GMT). No. of bitstreams: 1 2012_Maria_Cristina_Copello_Rotili.pdf: 1512539 bytes, checksum: 0de2ebbb956f5ea7ef24fdd44b97de82 (MD5) Previous issue date: 2012-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The passion fruit is a climacteric fruit and at the phase of the Post harvest suffers important physiological transformations resulting of its own metabolism of ripening and others oxidative stress. The storage conditions of the passion fruit establish determining factor for its conservation. The refrigeration and modified atmosphere have been widely used in fruits, and the yellow passion fruit appears very promising in the use of these techniques, due to high instability of its physical and physiological characteristics post harvest. Therefore, this study was conducted with the objective of to evaluate the biochemical, physicochemical and microbiological of the passion fruit during its storage in modified atmosphere and at different temperatures. The work was divided into two experiments: The first consisted of the evaluation of the effect of storage temperature, where the fruits were stored at 5 º and 24 ºC. And in the second experiment evaluated the effect of modified atmosphere during the storage of the fruits at 5 °C. In both experiments the evaluations occurred at intervals of 10 days for 40 days, being evaluated the antioxidant activity DPPH and TEAC, the content of total phenolic compounds, ß-carotene and ascorbic acid, and physical and microbiological quality of the fruits. In the second experiment were included assessments of total titratable acidity, total soluble solids and enzymatic activity for polyphenol oxidase and peroxidase. In both experiments, it was utilized a completely randomized delineation, with five repetitions. The results showed that the total phenolic compounds, β-carotene and antioxidant activity of passion fruit juice were not affected by storage temperature and the content of total phenolic compounds of the juice increased with storage time. The effects of high temperature during storage were more evident in the appearance of the fruit than at the nutritional quality of the juice. The antioxidant activity of the juice, expressed in kidnapping DPPH radical, decreased during the storage, independent of temperature. Under the conditions of storage at 5 ° C and normal atmosphere, the shelf-life of passion fruit was higher and lasted up to 20 days in good conditions of marketing. The use of modified atmosphere was not able to reduce the losses of antioxidant activity of passion fruit juice during its storage. Total phenolics compounds and ascorbic acid were not affected by the use of modified atmosphere. Up to 30 days of storage there was suppressive effect of the activity of pathogens similarly in the two atmospheres of storage, suggesting that this effect was more related to low temperature. At 40 days of storage the modified atmosphere was more effective in inhibiting the activity of pathogens. The modified atmosphere was effective in reducing fresh mass loss and wrinkling of the rind, evidencing the high sensitivity of the fruit changes involving the loss of water and the importance of the use of modified atmosphere in maintaining their physical quality. Total soluble solids and total titratable acidity decreased during the storage and the modified atmosphere did not affect these results. The use of modified atmosphere during the storage at 5° C provided great conditions for marketing the yellow passion fruit up to 20 days. This study revealed the existence of activities of the polyphenoloxidase and peroxidase enzymes in the yellow passion fruit rind, but they were not identified in the fruit juice / O maracujá-amarelo é um fruto climatérico e na fase pós-colheita sofre importantes transformações fisiológicas decorrentes do próprio metabolismo de maturação e de outros estresses oxidativos. As condições de armazenamento do maracujá estabelecem fator determinante para sua conservação. A refrigeração e a atmosfera modificada têm sido largamente utilizadas em frutos, e o maracujá-amarelo se apresenta muito promissor no uso dessas técnicas, devido à elevada instabilidade de suas características físicas e fisiológicas pós-colheita. Assim, este estudo foi realizado com o objetivo de avaliar as respostas bioquímicas, físico-químicas e microbiológicas do maracujá-amarelo durante o seu armazenamento em atmosfera modificada e em diferentes temperaturas. O trabalho foi dividido em dois experimentos: O primeiro constou da avaliação do efeito da temperatura de armazenamento, onde os frutos foram armazenados em temperatura de 5º e 24ºC. E no segundo experimento foi avaliado o efeito da atmosfera modificada durante o armazenamento dos frutos a 5 ºC. Em ambos os experimentos as avaliações ocorreram em intervalo de 10 dias durante 40 dias, sendo avaliada a atividade antioxidante DPPH e TEAC, os teores de compostos fenólicos totais, ß-caroteno e ácido ascórbico e a qualidade física e microbiológica dos frutos. No segundo experimento foram incluídas as avaliações de acidez total titulável, sólidos solúveis totais e a atividade enzimática para polifenoloxidase e peroxidase. Em ambos os experimentos, foi utilizado o delineamento inteiramente casualizado, com cinco repetições. Os resultados mostraram que os compostos fenólicos totais, β-caroteno e atividade antioxidante do suco do maracujá-amarelo não foram influenciados pela temperatura de armazenagem e o conteúdo de compostos fenólicos totais do suco aumentou com o tempo de armazenagem. Os efeitos da elevada temperatura durante o armazenamento foram muito mais evidentes na aparência do fruto do que na qualidade nutricional do suco. A atividade antioxidante do suco, expressa em sequestro do radical DPPH, diminuiu durante o armazenamento, independente da temperatura. Nas condições do armazenamento a 5 ºC e em atmosfera normal, a vida-de-prateleira do maracujá-amarelo foi superior e se estendeu até 20 dias em boas condições de comercialização. O uso da atmosfera modificada não foi capaz de reduzir as perdas de atividade antioxidante do suco do maracujá-amarelo, durante o seu armazenamento. Compostos fenólicos totais e ácido ascórbico também não foram influenciados pelo uso da atmosfera modificada. Até 30 dias de armazenamento houve efeito supressor da atividade de patógenos similarmente nas duas atmosferas de armazenagem, sugerindo que este efeito esteve mais relacionado à baixa temperatura. Aos 40 dias de armazenamento a atmosfera modificada foi mais eficiente em inibir a atividade de patógenos. A atmosfera modificada foi eficaz na redução da perda de massa fresca e do enrugamento da casca, ficando evidente a alta sensibilidade dos frutos à alterações envolvendo a perda de água e a importância do uso da atmosfera modificada na manutenção da sua qualidade física. Sólidos solúveis totais e acidez total titulável diminuíram durante o armazenamento e a atmosfera modificada não influenciou estes resultados. O uso da atmosfera modificada durante o armazenamento a 5 ºC proporcionou condições ótimas para comercialização do maracujá-amarelo até 20 dias. Este estudo revelou a existência de atividade das enzimas polifenoloxidase e peroxidase na casca do maracujá-amarelo, mas não foram identificadas no suco do fruto

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / This work aimed to study the effects of five layers of irrigation and five doses of potassium â applied through fertirrigation â on productivity and on quality of yellow passion fruits, in order to provide a proper crop management. The experiments were conducted on Embrapa Meio-Norte experimental field, in the municipality of Alvorada do Gurgueia, PI, Brazil, from March 2004 through April 2006. The experimental design consisted of randomized blocks with design in split-plots, with four replications. The treatments consisted of five doses of potassium (0,000; 0,225; 0,450; 0,650; 0,900 kg of K2O plant-1) and five irrigation layers (30; 60; 90; 120 and 150% of ECA). The plants were spaced by 2.5m x 4.0m. The results show that productivity and mean weight of fruits were significantly affected by irrigation layers, doses of potassium, as well as by the interaction term between the two factors; as for the number of fruits per hectare was significantly affected only by doses of potassium. Regarding the physical characteristics of the fruits, the longitudinal diameter and the juice production were significantly affected by number of layers, doses of potassium, and by the interaction term. The thickness of the rind was affected only by doses of potassium. As for the chemical characteristics of the fruits, only the level of total soluble solids was significantly affected by number of layers, doses, and by the interaction term; tritable total acidity (ATT) was affected only by doses of potassium; and pH was affected by none of the factors considered in this study. Among all treatment combinations, L4K4 yielded the highest fruit productivity, number, and mean weight. The levels of total soluble solids decreased with the increase layers applied, and the total acidity increased linearly with the increase of doses of potassium. / O trabalho teve como objetivo estudar o efeito de cinco lÃminas de irrigaÃÃo e cinco doses de potÃssio, aplicados via fertirrigaÃÃo, na produtividade e nas qualidades dos frutos do maracujazeiro amarelo, para posteriormente definir um manejo adequado da cultura. O experimento foi realizado no campo experimental da Embrapa Meio-Norte, no municÃpio de Alvorada do GurguÃia-PI, no perÃodo de marÃo de 2004 a abril de 2006, sendo que o delineamento utilizado foi em blocos casualizados com arranjo em parcelas subdivididas, com quatro repetiÃÃes. Os tratamentos foram compostos por cinco doses de potÃssio (0,000; 0,225; 0,450; 0,650; 0,900 kg de K2O planta-1) e cinco lÃminas de irrigaÃÃo (30; 60; 90; 120 e 150% da ECA). As plantas foram espaÃadas de 2,5 x 4,0 m. Verificou-se que a produtividade e o peso mÃdio dos frutos foram influenciados significativamente pelas lÃminas de irrigaÃÃo, pelas doses de potÃssio e pela interaÃÃo entre os fatores; jà o nÃmero de frutos por hectare somente foi influenciado significativamente pelas doses de potÃssio. Para as caracterÃsticas fÃsicas dos frutos, somente o diÃmetro longitudinal e o rendimento do suco sofreram influÃncia significativa da lÃmina, das doses de potÃssio e da interaÃÃo entre os fatores. A espessura da casca sà foi influenciada pelas doses de potÃssio. Nas caracterÃsticas quÃmicas dos frutos observou-se que, somente o teor de sÃlidos solÃveis totais sofreu influÃncia das lÃminas, das doses de potÃssio e da interaÃÃo entre os dois fatores; a acidez total titulÃvel foi influenciada apenas pelas doses de potÃssio e o pH, nÃo foi influenciado por nenhum dos fatores estudados. A combinaÃÃo dos tratamentos L4K4 foi a que proporcionou maior produtividade, nÃmero e peso mÃdio dos frutos. Os teores de sÃlidos solÃveis totais diminuÃram com o aumento da lÃmina aplicada e a acidez total titulÃvel cresceu linearmente com as doses de potÃssio.

<p>From insects to mammals, the ability to constantly sense environmental stimuli is essential for the survival of most living organisms. Most animals have nocifensive behaviors towards extreme temperatures, mechanical stimuli or irritant chemicals that are considered to be noxious. Nociception is defined as the neural encoding and processing of noxious stimuli. This process starts from the activation of pain detecting peripheral sensory neurons (nociceptors) that can detect noxious mechanical, thermal or chemical stimuli. On the other hand, animals also have the ability to discriminate innocuous temperatures and to direct their locomotions to their favorable environmental temperatures and this behavior is called thermotaxis. </p><p>In this study, I used <italic>Drosophila melanogaster</italic>as a genetic model organism to study the molecular and cellular basis of nociception and thermotaxis. <italic>Drosophila</italic> larvae exhibit a stereotyped defensive behavior in response to nociceptive stimuli (termed nocifensive escape locomotion behavior, NEL). Using this behavior as a readout, we manipulated the neuronal activities of periphery sensory Type II multidendritic neurons and have identified a specific class of neurons, class IV multidendritic neurons, to function as nociceptors in <italic>Drosophila</italic> larvae. </p><p>After identifying the nociceptors, I next investigated several ion channels that are critical molecular components for larval nociception. The Degenerin Epithelial Sodium Channel (DEG/ENaC) protein called pickpocket (ppk) is required specifically for larval mechanical nociception but not for thermal nociception. Being specifically expressed in class IV multidendritic neurons (the nociceptors), pickpocket is likely to function as a first detector of mechanical stimuli and upstream of general neuronal action potential propagation. In addition, I have found that the <italic>Drosophila</italic> orthologue of mammalian TRPA1 gene, <italic>TrpA1</italic>, is required for both mechanical and thermal nociception in <italic>Drosophila</italic> larvae. I have cloned a new isoform of dTRPA1 and have found it to be specifically expressed in class IV md neurons. Unlike the known dTRPA1 isoform that is warmth activated, this new isoform is not directly activated by temperatures between 15-42 °C. Instead, it may function downstream of sensory transduction step in the nociceptors. </p><p>Interestingly, <italic>dTrpA1</italic> mutants are also defective in their thermotaxis behavior within innocuous temperature ranges. In addition to the previously reported defects in avoiding warm temperatures, I have found these flies also failed to avoid cool temperatures between 16-19.5 °C. This defect is likely to be mediated by temperature sensing neurons in the antennae. I have detected antennal expression using a GAL4 reporter of dTrpA1. Significantly, these neurons exhibit elevated calcium levels in response to cooling. dTrpA1 mutants have a premature decay of the cooling response at temperatures below 22 °C during a cooling process. I have also identified another population of cells in the antennae that can respond to temperature changes. These neurons express the olfactory co-receptor Or83b and are known to be olfactory neurons. Calcium oscillations triggered by cooling were detected in these neurons and they were terminated by warming. Severe behavioral defects in avoiding cool temperatures were found in animals lacking <italic>Or83b</italic>. Our results suggest that there are multiple pathways regulating cooling sensation in the fly antennae.</p><p>Taken together, I have shown that <italic>Drosophila</italic> serves as a great model system to study nociception and thermosensation at molecular, cellular and behavioral levels.</p> / Dissertation

The family of Deg/HtrA proteases is present in a wide range of organisms from bacteria, archaea to eukaryota. These ATP-independent serine endopeptidases play key roles in the cellular protein quality control. The cyanobacterium Synechocystis sp. PCC 6803, a model organism for studies on photosynthesis, metabolism and renewable energy, contains three Deg proteases known as HhoA, HhoB and HtrA. The three proteases are important for survival in stress conditions, such as high light or temperature. In my work the biochemical characteristics of each protease were revealed in vitro and in vivo. In vitro studies performed using recombinant Synechocystis Deg proteases allowed conclusions about their oligomerization states, proteolytic activities and tertiary structure. The in vivo studies addressed their sub-cellular localization, expression and physiological importance by comparing wild-type Synechocystis cells with the three single mutants lacking one of the Deg proteases. HhoA seems to be involved in the cytoplasmic protein quality control. This protease is regulated post-transcriptional and post-translational: oligomerization, pH and/or cation-binding are some of the important factors to stimulate its proteolytic activity. Instead HhoB acts on periplasmic proteins and seems to be important for the transportation/secretion of proteins. While it has low proteolytic capacity, it may act as a chaperone. The stress-induced HtrA functions in the cellular tolerance against photosynthetic stress; additionally it might act as a protease partner of HhoB, generating a protease/chaperone complex. The results presented in this thesis lay the foundation for a better understanding of the dynamic protein quality control in cyanobacteria, which is undoubtedly important for various cellular metabolic pathways.

VASCONCELOS, Denise Vieira. Manejo de água e potassio por fertirrigação no maracujazeiro amarelo em alvorada do gurguéia, Piauí. 2007. 66 f. Dissertação (Mestrado em engenharia agrícola)- Universidade Federal do Ceará, Fortaleza-CE, 2007. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-17T17:57:46Z No. of bitstreams: 1 2007_dis_dvvasconcelos.pdf: 2270341 bytes, checksum: e29aea1e2937644f7b4c3462b5fdb1e6 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-07-21T20:08:37Z (GMT) No. of bitstreams: 1 2007_dis_dvvasconcelos.pdf: 2270341 bytes, checksum: e29aea1e2937644f7b4c3462b5fdb1e6 (MD5) / Made available in DSpace on 2016-07-21T20:08:37Z (GMT). No. of bitstreams: 1 2007_dis_dvvasconcelos.pdf: 2270341 bytes, checksum: e29aea1e2937644f7b4c3462b5fdb1e6 (MD5) Previous issue date: 2007 / This work aimed to study the effects of five layers of irrigation and five doses of potassium – applied through fertirrigation – on productivity and on quality of yellow passion fruits, in order to provide a proper crop management. The experiments were conducted on Embrapa Meio-Norte experimental field, in the municipality of Alvorada do Gurgueia, PI, Brazil, from March 2004 through April 2006. The experimental design consisted of randomized blocks with design in split-plots, with four replications. The treatments consisted of five doses of potassium (0,000; 0,225; 0,450; 0,650; 0,900 kg of K2O plant-1) and five irrigation layers (30; 60; 90; 120 and 150% of ECA). The plants were spaced by 2.5m x 4.0m. The results show that productivity and mean weight of fruits were significantly affected by irrigation layers, doses of potassium, as well as by the interaction term between the two factors; as for the number of fruits per hectare was significantly affected only by doses of potassium. Regarding the physical characteristics of the fruits, the longitudinal diameter and the juice production were significantly affected by number of layers, doses of potassium, and by the interaction term. The thickness of the rind was affected only by doses of potassium. As for the chemical characteristics of the fruits, only the level of total soluble solids was significantly affected by number of layers, doses, and by the interaction term; tritable total acidity (ATT) was affected only by doses of potassium; and pH was affected by none of the factors considered in this study. Among all treatment combinations, L4K4 yielded the highest fruit productivity, number, and mean weight. The levels of total soluble solids decreased with the increase layers applied, and the total acidity increased linearly with the increase of doses of potassium. / O trabalho teve como objetivo estudar o efeito de cinco lâminas de irrigação e cinco doses de potássio, aplicados via fertirrigação, na produtividade e nas qualidades dos frutos do maracujazeiro amarelo, para posteriormente definir um manejo adequado da cultura. O experimento foi realizado no campo experimental da Embrapa Meio-Norte, no município de Alvorada do Gurguéia-PI, no período de março de 2004 a abril de 2006, sendo que o delineamento utilizado foi em blocos casualizados com arranjo em parcelas subdivididas, com quatro repetições. Os tratamentos foram compostos por cinco doses de potássio (0,000; 0,225; 0,450; 0,650; 0,900 kg de K2O planta-1) e cinco lâminas de irrigação (30; 60; 90; 120 e 150% da ECA). As plantas foram espaçadas de 2,5 x 4,0 m. Verificou-se que a produtividade e o peso médio dos frutos foram influenciados significativamente pelas lâminas de irrigação, pelas doses de potássio e pela interação entre os fatores; já o número de frutos por hectare somente foi influenciado significativamente pelas doses de potássio. Para as características físicas dos frutos, somente o diâmetro longitudinal e o rendimento do suco sofreram influência significativa da lâmina, das doses de potássio e da interação entre os fatores. A espessura da casca só foi influenciada pelas doses de potássio. Nas características químicas dos frutos observou-se que, somente o teor de sólidos solúveis totais sofreu influência das lâminas, das doses de potássio e da interação entre os dois fatores; a acidez total titulável foi influenciada apenas pelas doses de potássio e o pH, não foi influenciado por nenhum dos fatores estudados. A combinação dos tratamentos L4K4 foi a que proporcionou maior produtividade, número e peso médio dos frutos. Os teores de sólidos solúveis totais diminuíram com o aumento da lâmina aplicada e a acidez total titulável cresceu linearmente com as doses de potássio.

abstract: With the high demand for faster and smaller wireless communication devices, manufacturers have been pushed to explore new materials for smaller and faster transistors. One promising class of transistors is high electron mobility transistors (HEMT). AlGaAs/GaAs HEMTs have been shown to perform well at high power and high frequencies. However, AlGaN/GaN HEMTs have been gaining more attention recently due to their comparatively higher power densities and better high frequency performance. Nevertheless, these devices have experienced truncated lifetimes. It is assumed that reducing defect densities in these materials will enable a more direct study of the failure mechanisms in these devices. In this work we present studies done to reduce interfacial oxygen at N-polar GaN/GaN interfaces, growth conditions for InAlN barrier layer, and microanalysis of a partial InAlN-based HEMT. Additionally, the depth of oxidation of an InAlN layer on a gate-less InAlN/GaN metal oxide semiconductor HEMT (MOSHEMT) was investigated. Measurements of electric fields in AlGaN/GaN HEMTs with and without field plates are also presented. / Dissertation/Thesis / Doctoral Dissertation Physics 2018

My thesis research comprises two projects looking into physiological functions of Drosophila ion channels: first, contribution of several T ransient R eceptor P otential (TRP) channels to gravity sensing; second, regulation of metabolic homeostasis by a D egenerin/ E pithelial Na + C hannel (DEG/ENaC). Many animal species sense gravity for spatial orientation. In humans recurrent vertigo and dizziness are often attributable to impairment of gravity sensing in the vestibular organs. However, the molecular bases for gravity sensing and its disruption in vestibular disease remain uncertain. Here I studied gravity sensing in the model organism Drosophila melanogaster, with a combination of genetic, behavioral and electrophysiological methods. My results show that gravity sensing requires Johnston’s organ, a mechanosensory structure located in the antenna that also mediates hearing. Johnston’s organ neurons fire action potentials in a phasic manner in response to body rotations in the gravitational field. Furthermore, gravity sensing and hearing require different TRP channels with distinct anatomical localizations, implying separate neural mechanisms underlying gravity sensing and hearing. These findings set the stage for understanding how TRP channels contribute to the sensory transduction of gravity. Drosophila melanogaster has over 20 genes belonging to the DEG/ENaC family, which are collectively referred to as pickpockets (ppks) . Genetic analyses have implicated ppk genes in salt taste, tracheal liquid clearance, pheromone detection, and developmental timing. These results, together with the conserved presence of DEG/ENaC genes through evolution, suggest that further studies on fly ppk genes may help gain insights to a number of physiological processes. Here I report that the ppk11 gene regulates metabolic homeostasis. A ppk11 enhancer/promoter fragment labels the fat body, the lipid storage organ of Drosophila. ppk11 mutants are lean — they store less triacylglyceride (TAG), possess smaller lipid droplets and are sensitive to starvation compared to wild–type flies. ppk11 mutants also show signs of enhanced insulin sensitivity — they store more glycogen and maintain a lower level of circulating carbohydrate (trehalose). Moreover, the mutants have extended life span, suggesting ppk11–dependent activities of the fat body have systematic and long–term effects on the fly body. Understanding the cellular function of ppk11 may offer new insights into mechanisms that regulate metabolic homeostasis.