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Selectivity in the mechanism of action of antimicrobial mastoparan peptide Polybia-MP1

CABRERA, Marcia Perez dos Santos; COSTA, Sabrina Thais Broggio; SOUZA, Bibiana Monson de; PALMA, Mário Sérgio; RUGGIERO, José Roberto; RUGGIERO NETO, João
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.48%
Many potent antimicrobial peptides also present hemolytic activity, an undesired collateral effect for the therapeutic application. Unlike other mastoparan peptides, Polybia-MP1 (IDWKKLLDAAKQIL), obtained from the venom of the social wasp Polybia paulista, is highly selective of bacterial cells. The study of its mechanism of action demonstrated that it permeates vesicles at a greater rate of leakage on the anionic over the zwitterionic, impaired by the presence of cholesterol or cardiolipin; its lytic activity is characterized by a threshold peptide to lipid molar ratio that depends on the phospholipid composition of the vesicles. At these particular threshold concentrations, the apparent average pore number is distinctive between anionic and zwitterionic vesicles, suggesting that pores are similarly formed depending on the ionic character of the bilayer. To prospect the molecular reasons for the strengthened selectivity in Polybia-MP1 and its absence in Mastoparan-X, MD simulations were carried out. Both peptides presented amphipathic alpha-helical structures, as previously observed in Circular Dichroism spectra, with important differences in the extension and stability of the helix; their backbone solvation analysis also indicate a different profile...

Ligand- and Structure-Based Drug Design Strategies and PPAR delta/alpha Selectivity

Maltarollo, Vinicius G.; Honorio, Káthia Maria
Fonte: Wiley-Blackwell; Hoboken Publicador: Wiley-Blackwell; Hoboken
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.38%
Peroxisome-proliferator-activated receptors are a class of nuclear receptors with three subtypes: a, ? and d. Their main function is regulating gene transcription related to lipid and carbohydrate metabolism. Currently, there are no peroxisome-proliferator-activated receptors d drugs being marketed. In this work, we studied a data set of 70 compounds with a and d activity. Three partial least square models were created, and molecular docking studies were performed to understand the main reasons for peroxisome-proliferator-activated receptors d selectivity. The obtained results showed that some molecular descriptors (log P, hydration energy, steric and polar properties) are related to the main interactions that can direct ligands to a particular peroxisome-proliferator-activated receptors subtype.; FAPESP; FAPESP; CNPq; CNPq; CAPES; CAPES

A fragment-based approach for ligand binding affinity and selectivity for the liver X receptor beta

Salum, Lívia de Barros; Andricopulo, Adriano Defini; Honorio, Káthia Maria
Fonte: Elsevier Science INC; New York Publicador: Elsevier Science INC; New York
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.48%
Selective modulation of liver X receptor beta (LXR beta) has been recognized as an important approach to prevent or reverse the atherosclerotic process. In the present work, we have developed robust conformation-independent fragment-based quantitative structure-activity and structure-selectivity relationship models for a series of quinolines and cinnolines as potent modulators of the two LXR sub-types. The generated models were then used to predict the potency of an external test set and the predicted values were in good agreement with the experimental results, indicating the potential of the models for untested compounds. The final 2D molecular recognition patterns obtained were integrated to 3D structure-based molecular modeling studies to provide useful insights into the chemical and structural determinants for increased LXR beta binding affinity and selectivity. (C) 2011 Elsevier Inc. All rights reserved.; FAPESP (The State of Sao Paulo Research Foundation); FAPESP (The State of Sao Paulo Research Foundation); CNPq (The National Council for Scientific and Technological Development); CNPq (The National Council for Scientific and Technological Development); CAPES (Coordination for the Improvement of High Education Personnel), Brazil; CAPES (Coordination for the Improvement of High Education Personnel)...

Estratégias para aumento de sensibilidade e seletividade de separações cromatográficas em sistemas de análises em fluxo; Strategies to improve sensitivity and selectivity of chromatographic separations in flow analysis systems

Batista, Alex Domingues
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/12/2014 PT
Relevância na Pesquisa
36.48%
A introdução de separações cromatográficas expandiu a aplicabilidade de sistemas de análises em fluxo. No entanto, a seletividade e sensibilidade de procedimentos são restritos devido à escassa disponibilidade de fases estacionárias que operam a baixas pressões. Sendo assim, foram desenvolvidos quatro procedimentos analíticos visando a melhoria destes aspectos. A primeira proposta explorou pioneiramente colunas de núcleo fundido em sistemas de análises por injeção em fluxo. A separação de metil, etil e propil parabenos foi selecionada com aplicação. As eficiências cromatográficas de quatro colunas (C18, RPamida, F5 e fenil-hexil) foram avaliadas criticamente. Acetonitrila e uma solução de ácido fosfórico pH 2,5 foram utilizadas como fase móvel. A fase RP-amida apresentou melhor desempenho com a separação dos três analitos em 8,0 min, com resoluções > 1,72, simetrias de pico < 1,66, LOD entre 0,12 e 0,39 mg L-1, resposta linear até 5,0 mg L-1 (r > 0,996) e CV para altura dos picos < 3,5 % (n=10). O procedimento foi aplicado à determinação de parabenos em produtos de cuidados pessoais e os resultados concordaram com o procedimento de referência a 95% de confiança. Um procedimento envolvendo o acoplamento de extração em fase sólida (SPE) a um sistema de cromatografia por injeção sequencial (SIC) foi proposto para pré-concentração e separação de oito sulfonamidas. A fase estacionária pentafluorofenilpropil foi selecionada após comparação crítica da eficiência apresentada por três colunas de núcleo fundido e duas colunas de fases monolíticas. Acetonitrila e tampão fosfato (pH 5...

Seletividade e dose de injúria econômica de nicosulfuron aplicado em diferentes estádios de desenvolvimento da cultura do milho; Selectivity and rate of economic injury of nicosulfuron on corn treated at different growth stages

Spader, Vitor; Vidal, Ribas Antonio
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
Relevância na Pesquisa
36.48%
A tolerância de plantas de milho ao herbicida nicosulfuron é variável em função dos estádios de desenvolvimento da cultura. Um experimento foi conduzido a campo, na EEA-UFRGS, em Eldorado do Sul, com os objetivos de avaliar a seletividade de nicosulfuron aspergido nos diferentes estádios de desenvolvimento vegetativo do milho e com diferentes doses do herbicida e de verificar a resposta econômica da fitotoxicidade do produto na cultura. O milho híbrido AG501, tolerante ao nicosulfuron, foi implantado no sistema de semeadura direta numa área com controle prévio das plantas daninhas com herbicida pré-emergente. Os tratamentos foram organizados num esquema fatorial representado por doses de nicosulfuron (0, 60 e 80g ha-1) e pelos estádios de desenvolvimento vegetativo do milho (V3, V6 e V9, indicando 3, 6 e 9 folhas expandidas, respectivamente). O delineamento experimental foi o de blocos casualizados com quatro repetições. A seletividade do nicosulfuron para a cultura do milho diminui a partir do estádio de 6 folhas expandidas (V6) e com o incremento da dose além de 60g ha-1. A dose de injúria econômica, ou seja, a dose de nicosulfuron no qual o benefício do controle de ervas se iguala à perda de rendimento de grãos devido a injúria à cultura se reduz com a diminuição do dano causado pelas infestantes e com o aumento do preço da cultura.; The tolerance of the corn crop to the herbicide nicosulfuron depends on the crop growth stage. An experiment was conducted in Eldorado do Sul...

Selectivity of the cyclic carbonate formation by fixation of carbon dioxide into epoxides catalyzed by Lewis bases

Gomes, Caio Ribeiro; Ferreira, Daniele Marcondes; Leopoldo Constantino, Carlos J.; Perez Gonzalez, Eduardo R.
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 6879-6881
ENG
Relevância na Pesquisa
36.38%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Cyclic carbonate and polycarbonate have been selectively obtained with good conversion by coupling carbon dioxide with diglycidylether of bisphenol A. The ruthenium trichloride supported on tetraethylammonium bromide and polyphosphotungstic acid has been found active and selective to produce the corresponding monomeric and polymeric carbonates. These catalysts can be recycled keeping their high product conversion and selectivity. The heteropolyacid itself showed high activity also under supercritical CO(2) conditions to yield polycarbonate. (c) 2008 Elsevier Ltd. All rights reserved.

Catch and selectivity parameters of the anastomid fish Schizodon nasutus using gillnets in the Jurumirim reservoir (São Paulo, Brazil)

Garcia-Mellado, A.; Oliva-Paterna, F. J.; Carvalho, E. D.; Torralva, M.
Fonte: Unione Zoologica Italiana Publicador: Unione Zoologica Italiana
Tipo: Artigo de Revista Científica Formato: 333-338
ENG
Relevância na Pesquisa
36.56%
Catch and selectivity parameters using gillnets were calculated for Schizodon nasutus in the Jurumirim reservoir on the Parana-panema River in southern Brazil. The simple gillnets used were made of monofilament nylon of 30 to 140 mm mesh size an of different heights. The relative abundance of the S. nasutus caught was analysed monthly and a positive relationship was found between catches per unit effort in number and biomass. The relative catches were more abundant for the nets of 40 and 50 mm, mesh size. Catches were characterized by clear temporal variations and a predominance of medium size fish throughout the study period. The selectivity curve of gillnets for S. nasutus in this ecosystem was obtained. The catch obtained was compared with the available catch for each mesh size, and the available catch for a certain length of fish was calculated starting from the theoretical selectivity curve. The 50 mm mesh size gillnet showed the best fit between real and available captures and was considered the most suitable, because a smaller mesh size resulted in a catch of predominantly immature specimens. It is expected that these results will contribute to improving management strategies for conservation of resources. Parameters such as the minimum catch length advisable or the mesh size permitted for a given species are indispensable for such decision-making.

Selectivity in the mechanism of action of antimicrobial mastoparan peptide Polybia-MP1

Santos Cabrera, Marcia Perez dos; Broggio Costa, Sabrina Thais; Souza, Bibiana Monson de; Palma, Mario Sergio; Ruggiero, José Roberto; Neto, Joao Ruggiero
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 879-891
ENG
Relevância na Pesquisa
36.48%
Many potent antimicrobial peptides also present hemolytic activity, an undesired collateral effect for the therapeutic application. Unlike other mastoparan peptides, Polybia-MP1 (IDWKKLLDAAKQIL), obtained from the venom of the social wasp Polybia paulista, is highly selective of bacterial cells. The study of its mechanism of action demonstrated that it permeates vesicles at a greater rate of leakage on the anionic over the zwitterionic, impaired by the presence of cholesterol or cardiolipin; its lytic activity is characterized by a threshold peptide to lipid molar ratio that depends on the phospholipid composition of the vesicles. At these particular threshold concentrations, the apparent average pore number is distinctive between anionic and zwitterionic vesicles, suggesting that pores are similarly formed depending on the ionic character of the bilayer. To prospect the molecular reasons for the strengthened selectivity in Polybia-MP1 and its absence in Mastoparan-X, MD simulations were carried out. Both peptides presented amphipathic alpha-helical structures, as previously observed in Circular Dichroism spectra, with important differences in the extension and stability of the helix; their backbone solvation analysis also indicate a different profile...

Hook selectivity of the pacu Piaractus mesopotamicus (Holmberg, 1887) in the Pantanal, the state of Mato Grosso do Sul, Brazil

Peixer, J.; Petrere Jr., M.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: 339-345
ENG
Relevância na Pesquisa
36.61%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Desde 1994, o pacu Piaractus mesopotamicus, é a principal espécie nas capturas comerciais e esportivas no Pantanal sul-matogrossense, e seu rendimento máximo sustentável já foi ultrapassado. Sua captura só é permitida por anzóis, para as duas pescarias acima, visto que as artes de emalhe são proibidas na região. O objetivo deste estudo foi o de determinar a seletividade para diferentes tamanhos de anzóis usados na captura do pacu e verificar a partir de qual tamanho de anzol somente os adultos são capturados. Para tal, foram realizadas pescarias nos rios Miranda, Aquidauana e Vermelho, nos meses de janeiro, março e abril de 2002. Seis espinhéis contendo 8 tamanhos diferentes de anzóis foram empregados. A abertura do anzol foi adotada para expressar sua seletividade. Diferentes anzóis capturaram indivíduos de mesmo comprimento, e suas medianas foram similares, evidenciando a grande sobreposição dos tamanhos capturados. As regressões entre ln[c2 (l)/c1 (l)] e l não foram significativas. O teste de Kolmogorov-Smirnov também não detectou diferenças significativas nos tamanhos dos peixes capturados por diferentes anzóis. Várias hipóteses são levantadas para explicar a ausência de seletividade dessa amplitude de tamanhos de anzóis para a espécie. O recrutamento para a pesca...

Study of the selectivity of SnO2 supported membranes prepared by a sol-gel route

Santos, LRB; Larbot, A.; Santilli, C. V.; Pulcinelli, S. H.
Fonte: Kluwer Academic Publ Publicador: Kluwer Academic Publ
Tipo: Artigo de Revista Científica Formato: 805-811
ENG
Relevância na Pesquisa
36.38%
In this work the sol-gel process was used to prepare SnO2 supported membranes with an average pore size of 2.5 nm. The effects of salt concentration (NaCl or CaCl2) and of the pH of the aqueous solutions used on the flux and selectivity through the SnO2 membrane were analyzed by permeation experiments and the results interpreted taking account of the zeta potential values determined from the electrophoretic mobility of the SnO2 powder aqueous dispersion. The results show that the ion flux (Na+, Ca2+ and Cl-) throughout the membrane is determined by the electrostatic repulsion among these species and the surface charge at the tin oxide-solution interface.

Síntese total da (-)-goniotrionina : estudo teórico da influência estereoeletrônica na seletividade 1,5 em reações aldólicas envolvendo beta-alcoxi metilcetonas; Total synthesis of (-)goniotrionin : theoretical studies of stereoelectronic influence in the 1,5 selectivity of aldol reaction involving beta-alkoxy methylketones

Marco Antonio Barbosa Ferreira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/07/2012 PT
Relevância na Pesquisa
36.56%
SÍNTESE TOTAL DA (-)-GONIOTRIONINA: Foi desenvolvida uma rota sintética flexível, em uma abordagem modular, que permitiu a primeira síntese total da estrutura descrita para a goniotrionina (11), em 4% de rendimento global e em 17 etapas pela rota linear mais longa, a partir do glicidol quiral (R)-109. A nossa rota sintética fez uso de epóxidos quirais como blocos de construção, em uma estratégia envolvendo a abertura de epóxidos. As etapas chave incluem ciclização aeróbica de Mukaiyama para formação do anel THF-2,5-trans e reação aldólica de Mukaiyama 1,2-syn seletiva. Esta mesma abordagem sintética pode permitir a preparação de análogos e outros diastereoisômeros da (-)-goniotrionina (11). ESTUDO TEÓRICO DA INFLUÊNCIA ESTEREOELETRÔNICA NA SELETIVIDADE 1,5 EM REAÇÕES ALDÓLICAS ENVOLVENDO B-ALCOXI METILCETONAS. Nesta segunda parte do trabalho foi possível aprofundar o conhecimento sobre a origem da seletividade 1,5 em reações aldólicas envolvendo enolatos de boro de b-alcóxi metilcetonas, a partir do cálculo das estruturas eletrônicas dos estados de transição. Investigou-se a influência dos estereocentros em a, b, y e s em reações aldólicas, determinando os fatores decisivos que governam o senso de indução 1...

Wildfire selectivity for land cover type: does size matter ?

Barros, Ana M.G.; Pereira, J.M.C.
Fonte: Gil Bohrer, The Ohio State University, USA Publicador: Gil Bohrer, The Ohio State University, USA
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
36.72%
Previous research has shown that fires burn certain land cover types disproportionally to their abundance. We used quantile regression to study land cover proneness to fire as a function of fire size, under the hypothesis that they are inversely related, for all land cover types. Using five years of fire perimeters, we estimated conditional quantile functions for lower (avoidance) and upper (preference) quantiles of fire selectivity for five land cover types - annual crops, evergreen oak woodlands, eucalypt forests, pine forests and shrublands. The slope of significant regression quantiles describes the rate of change in fire selectivity (avoidance or preference) as a function of fire size. We used Monte-Carlo methods to randomly permutate fires in order to obtain a distribution of fire selectivity due to chance. This distribution was used to test the null hypotheses that 1) mean fire selectivity does not differ from that obtained by randomly relocating observed fire perimeters; 2) that land cover proneness to fire does not vary with fire size. Our results show that land cover proneness to fire is higher for shrublands and pine forests than for annual crops and evergreen oak woodlands. As fire size increases, selectivity decreases for all land cover types tested. Moreover...

Market timing and selectivity: evaluating both contributions towards the performance of portuguese equity funds

Govan, Chandni
Fonte: Instituto Universitário de Lisboa Publicador: Instituto Universitário de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2011 ENG
Relevância na Pesquisa
36.48%
Mestrado em Finanças; This study attempts to understand the selectivity and market timing abilities of the Portuguese mutual fund managers. Therefore, the focus of the present investigation will be the evaluation of the performance of 51 Portuguese Equity Funds between January 2001 and December 2010. In order to achieve this, the methodology developed by Merton and Henriksson in 1981 will be used. The Jensen measure (1968) will also be applied in order to compare the results. Additionally, the problem of heteroscedasticity and autocorrelation of the errors will also be addressed, where the following methods will be used: the method of White (1980), the method of Newey-West (1987) and the method of Cochrane-Orcutt (1949). The results of this study shows that there is neither clever selectivity (security selection) nor skillful market timing abilities evidenced by most of the analyzed Equity Fund managers which is consistent with prior studies realized by Romacho (2004) and Afonso (2010). Other finding is regarding the negative correlation between the both abilities which is more evident in the international group of funds.; O presente estudo pretende analisar as capacidades de selectividade e de market timing dos gestores de fundos de investimento Portugueses. Neste sentido o foco da investigação incide sobre o desempenho de 51 Fundos de Acções Portugueses durante o período de Janeiro de 2001 a Dezembro de 2010. Para tal foi aplicada a metodologia de Henriksson e Merton (1981). Também foi utilizada a medida de Jensen (1968)...

Ethylbenzene Disproportionation on HZSM-5 Zeolite: The Effect of Aluminum Content and Crystal Size on the Selectivity for p-Diethylbenzene

Velasco,N.D.; Machado,M.S.; Cardoso,D.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/1998 EN
Relevância na Pesquisa
36.61%
The aim of this work was to verify the effect of MFI aluminum content and crystal size on the selectivity for para-diethylbenzene during ethylbenzene disproportionation. It was observed that the para-diethylbenzene selectivity increased as MFI crystal size increased. The increase in aluminum content caused a decrease in the selectivity for para-diethylbenzene. However, for crystals larger than 8 m m, the decrease in aluminum content had little influence on the selectivity for para-diethylbenzene. The results can be explained by the number of active aluminum sites on the external surface of the crystals.

Hook selectivity of the pacu Piaractus mesopotamicus (Holmberg, 1887) in the Pantanal, the state of Mato Grosso do Sul, Brazil

Peixer,J.; Petrere Jr.,M.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2007 EN
Relevância na Pesquisa
36.61%
The Pacu Piaractus mesopotamicus is the most captured fish species in the Pantanal, Mato Grosso do Sul State, and since 1994, its maximum sustainable yield had already been exceeded. Its capture is carried out only by hooks, as mesh gears are forbidden either for professional or for recreational fishing. The aim of this study was to determine selectivity for different hook sizes used in P. mesopotamicus fishing and to verify which sizes capture only adults. Data were collected in the rivers Miranda, Aquidauana, and Vermelho, in January, March, and April 2002. Six longlines with eight hook sizes were used and we adopted the hook opening as a measure related to selectivity. Different hooks captured individuals of the same length and their medians were similar, evidencing the great overlap among sizes. Regression results showed no significant relationship between ln[c2 (l)/c1 (l)] and total length of captured individuals. In addition, the Kolmogorov-Smirnov test also did not detect significant differences in the size of captured fish. Several hypotheses, such as the selectivity models, shape of selection curves, scarcity of large fishes, and behavior are used in order to explain the absence of hook selectivity for this species. Size of recruitment for this gear was 28 cm of total length...

Cytochrom Oxidase Blobs und Orientierungsselektivität. Eine funktional-anatomische Studie am primären visuellen Kortex von Primaten; Cytochrome Oxidase Blobs and Orientation Selectivity. Functional-Anatomical Investigations of the Primary Visual Cortex of Primates

Valverde Salzmann, Matthias Felipe
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.56%
Eine der herausragenden Eigenschaften des visuellen Kortex in Primaten ist seine ausgeprägte Tendenz zur Musterbildung, die sich in seiner anatomischen und funktionellen Struktur zeigt. Durch histologische Färbungen lässt sich diese Musterbildung auf anatomischer Ebene bei der Verteilung von Zelltypen, thalamischer Afferenzen, neurochemischer Gradienten und Blutgefäßdichten aufzeigen. Für die Darstellung der funktionellen Strukturen hat sich die Optical-Imaging-Technik hervorgetan. Sie ermöglicht, topographische Karten von dem Verlauf funktioneller Bereiche wie etwa Okulärer Dominanzkolumnen (ODK) oder farb- und orientierungsselektiver Gewebebereiche zu erstellen. Verschiedene Modelle sind in den letzten Jahrzenten entwickelt worden, um die Informationsverarbeitungsmechanismen des visuellen Systems zu erklären und dabei die Topographie der funktionellen Strukturen mit anatomischen Strukturen wie z.B. den thalamischen Eingangsbereichen (zB. Blob- und Zwischenblobbereiche) und darüber wiederum mit den verschiedenen Informationspfaden des visuellen Systems (Magno-, Parvo-, Koniopfade) in Übereinstimmung zu bringen. Solche Untersuchungen werden durch eine Reihe von methodischen Schwierigkeiten beeinträchtigt, die es notwendig machen...

Orientation Selectivity and Contrast Gain Control in Representations of Natural Images; Orientierungsselektivität und Kontrastverstärkungsregelung in Repräsentationen von natürlichen Bildern

Sinz, Fabian H.
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
EN
Relevância na Pesquisa
36.48%
This thesis explores the role of orientation selectivity and contrast gain control with respect to Barlow's normative redundancy reduction hypothesis in simple models of the early visual system. Our general approach uses the fact that-under the goal of redundancy reduction-early vision models are density models on natural images. We identify and develop new classes of probabilistic models for natural image patches that contain these early vision models. We use those classes to quantitatively explore their parameter space around the early vision models statistically and information theoretically with respect to the influence of filter shapes and contrast transforms on redundancy reduction. We identify an optimal contrast gain control transform and compare it to the standard model of cortical divisive contrast gain control, divisive normalization. We also identify a new estimation method for the true redundancy of natural images. Our main findings are that, in contrast to divisive contrast gain control, orientation selectivity plays a minor role for redundancy reduction in the models investigated, and that the cortical model of divisive contrast normalization is not the optimal redundancy reducing contrast transformation on static image patches. However...

Use of cellular impedance to characterize ligand functional selectivity at G protein-coupled receptors

Stallaert, Wayne
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
Relevância na Pesquisa
36.65%
Les récepteurs couplés aux protéines G (RCPGs) représentent la plus grande famille de cibles thérapeutiques pour le traitement d’une panoplie de pathologies humaines. Bien que plusieurs décennies de recherche aient permis de façonner nos connaissances sur ces protéines membranaires, notre compréhension des déterminants moléculaires de leur activité signalétique reste encore limitée. De ces domaines de recherche, une avancée récente a mis à jour un nouveau phénomène, appelé sélectivité fonctionnelle des ligands, qui a bouleversé les paradigmes décrivant leu fonctionnement de ces récepteurs. Ce concept émane d’observations montrant que l’activité pharmacologique de certains ligands n’est pas nécessairement conservée sur tout le répertoire signalétiques connu du récepteur et peu se restreindre à l'activation sélective d’un sous-groupe de voies de signalisation.Ce nouveau modèle pharmacologique de l'activation des RCPG ouvre de nouvelles possibilités pour la découverte de médicaments plus efficace et sûr, ciblant les RCPGs. En effet, il permet la conception de molécules modulant spécifiquement les voies signalétiques d’intérêt thérapeutique, sans engager les autres voies qui pourraient mener à des effets secondaires indésirables ou de la tolérance. Cette thèse décrit l'utilisation d'une nouvelle approche sans marquage...

Improved trawl selectivity: effects on the ecosystem in the South Catalan Sea (NW Mediterranean)

Coll, Marta; Bahamon, Nixon; Sardà, Francisco; Palomera, Isabel; Tudela, Sergi; Suuronen, Petri
Fonte: Inter Research Publicador: Inter Research
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
Relevância na Pesquisa
36.61%
17 pages, 9 figures, 6 tables; We explored the potential ecosystem effects of improved selectivity in the South Catalan Sea demersal trawl fishery. A calibrated food web model representing current conditions of the ecosystem and selectivity data from recent fishing experiments were used to perform temporal dynamic simulations. This enabled the evaluation of direct and indirect impacts of fishing and provided insights into the sustainability of various management options for the trawl fishery. This fishery has the biggest fleet in the area, it is highly multispecies, and catches are largely composed of juveniles of target species and non-target species, which are often discarded in large quantities. Simulations indicate that improvement of trawl selectivity would have noticeable and complex direct and indirect effects on target and non-target demersal species. The biomass and catch of various commercial species (e.g. anglerfish, adult hake) would increase, while that of invertebrates (e.g. suprabenthos, Norway lobster) and juvenile and small-sized fish species (e.g. juvenile hake, blue whiting) would decrease due to higher predation mortalities and trophic cascades in the food web. Impacts on the pelagic compartment would also be noticeable. A slight increase in the mean trophic level of the community and of the catch is predicted...

Functional Analysis of Ion Selectivity and Permeation Mechanisms of the C. elegans TRPV Channel OSM-9

Lindy, Amanda Sue
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
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For all organisms, the ability to sense and react to noxious environments is fundamental to their survival. For multi-celled organisms this process generally involves a nervous system and an extensive network of signal transduction pathways. TRPV ion channels have been shown to participate in signal transduction in response to noxious stimuli. At the cellular level these channels function in sensing of mechanical, thermal, and osmotic stimuli, and at the organismal level they function in homeostasis and nociception. TRPV ion channels participate in nociceptive signal transduction via cation influx, but exactly how these channels function at a mechanistic level and lead to activation of the cell or induction of a specific behavior is elusive. Previous research has shown that the pore-forming unit of an ion channel is critical for channel regulation, gating, ion selectivity, and ion permeation. Various regulatory domains have been identified to date in the pore-forming unit of TRP channels and a clearer picture of channel gating is beginning to emerge, but less is known about ion permeation.

To better understand the specific domains that are critical to ion capture, selectivity, and permeation in TRPV channels, we investigated the function of these regions using the C. elegans TRPV channel OSM-9 in vivo...