• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 314
  • 62
  • 51
  • 48
  • 24
  • 19
  • 12
  • 11
  • 10
  • 5
  • 5
  • 5
  • 4
  • 4
  • 2
  • Tagged with
  • 780
  • 62
  • 57
  • 51
  • 51
  • 47
  • 46
  • 41
  • 40
  • 37
  • 36
  • 35
  • 30
  • 30
  • 30
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
461

Development of active integrated antennas and optimization for harmonic suppression antennas : simulation and measurement of active antennas for amplifiers and oscillators and numerical solution on design and optimization of active patch antennas for harmonic suppression with adaptive meshing using genetic algorithms

Zhou, Dawei January 2007 (has links)
The objectives of this research work are to investigate, design and implement active integrated antennas comprising active devices connected directly to the patch radiators, for various applications in high efficiency RF front-ends, integrated oscillator antennas, design and optimization of harmonic suppression antennas using a genetic algorithm (GA). A computer-aided design approach to obtain a class F operation to optimizing the optimal fundamental load impedance and designing the input matching circuits for an active integrated antenna of the transmitting type is proposed and a case study of a design for 1.6 GHz is used to confirm the design principle. A study of active integrated oscillator antennas with a series feed back using a pseudomorphic high electronmobility transistor (PHEMT) confirms the design procedure in simulation and measurement for the oscillator circuit connected directly to the active antenna. Subsequently, another design of active oscillator antenna using bipolar junction transistor (BJT) improves the phase noise of the oscillation and in addition to achieve amplitude shift keying (ASK) and amplitude modulation (AM) modulation using the proposed design circuit. Moreover, the possibility of using a sensor patch technique to find the power accepted by the antenna at harmonic frequencies is studied. A novel numerical solution, for designing and optimizing active patch antennas for harmonic suppression using GA in collaboration with numerical electromagnetic computation (NEC), is presented. A new FORTRAN program is developed and used for adaptively meshing any planar antenna structure in terms of wire grid surface structures. The program is subsequently implemented in harmonic suppression antenna design and optimization using GA. The simulation and measurement results for several surface structures show a good agreement.
462

Supressão de bandas laterais através da técnica de rotação da amostra em torno do ângulo mágico com frequência variável / Spinning sideband suppression by variable and low magic angle spinning

Vidoto, Ednalva Aparecida 11 October 1995 (has links)
Em experimentos de Ressonância Magnética Nuclear (RMN) com Rotação da Amostra em Tomo do Ângulo Mágico (MAS), as bandas laterais são um problema comum na obtenção de espectros de alta resolução em sólidos. Em espectrômetros de alto campo magnético ou então, em sistemas que não dispõem de rotores de amostra de freqüência elevada, este problema é mais grave. Para facilitar a interpretação do espectro de alta resolução torna-se necessário suprimir estas bandas laterais. Nesta dissertação descrevemos um método simples de supressão das bandas laterais que consiste em variar a freqüência de rotação da amostra durante a aquisição do sinal, assim como, a instrumentação necessária para realizar esse experimento. Este método, que denominamos de Supressão das Bandas Laterais utilizando-se Freqüência de Rotação Baixa e Variável, baseia-se na dependência da posição das bandas laterais com a freqüência de rotação, reduzindo as coincidências entre suas posições durante a promediação, enquanto o sinal isotrópico permanece estável sempre no mesmo ponto do espectro. Para ilustrar a utilização dessa nova técnica, realizamos experimentos de RMN com o núcleo de 13C em amostras de hexametilbenzeno, tirosina, lignina e ácido húmico, e com o núcleo quadrupolar 79Br em amostras de KBr e NaBr + KBr / Sidebands in Magic-Angle-Spinning Nuclear Magnetic Resonance (MAS-NMR) experiments are a common problem for high field spectrometers or low spinning frequency systems. Although these sidebands may be used to gain information after they have been identified, it is necessary to eliminate then to simplify the interpretation of the spectra; we have recently succeeded in suppressing spinning sidebands by continuously varying the speed during the signal acquisition. This method, that we called variable low speed sideband suppression, relies on the speed dependent of the sideband positions. The purpose of this work is to describe a simple method and apparatus to suppress spinning sidebands in MAS-NMR experiments. The method allows a quick acquisition of the isotropic chemical shift spectra and works well even when the highest available spinning cannot clearly resolve the spinning sidebands. To illustrate the method, we present the 13C MAS-NMR spectra of a variety of sample acquired using cross-polarization and high power proton decoupling. Among the samples studied were: hexamethylbenzene, tyrosine, lignin and humic acid. And quadrupolar nuclei 79Br in the samples Kbr and NaBr + KBr
463

Licenciamento ambiental e arborização urbana: estudos de caso do Município de São Paulo / Licensing of trees suppression and urban arborization: case study in São Paulo city.

Ferreira, Laurita Bravo 28 April 2011 (has links)
Este trabalho tem por objetivo analisar como o licenciamento de supressão de árvores contribui para a implantação da arborização urbana no município de São Paulo e salienta a importância do planejamento para a identificação das áreas com prioridade para sua implantação. Abordam-se as diferentes contribuições da arborização e suas funções como determinantes para a área de escolha da implantação de espécies arbóreas. Por fim, é realizado um estudo de caso no distrito de Santo Amaro onde o mapeamento da distribuição existente da arborização, associado aos mapas de temperatura aparente, espaços livres intraquadras, uso do solo e sistema viário, auxiliam a analisar as áreas com déficits de arborização através da identificação do sistema de áreas arborizadas. O entendimento desse sistema permite a implantação de arborização nas áreas mais deficitárias das funções proporcionadas pela arborização, como amenização da temperatura, filtragem do ar e diminuição das enchentes. / This study aims to examine how the licensing of trees suppression contributes to the settlement of urban arborization in São Paulo city, it also reinforces the importance of planning, identifying priority areas for adequate arborization implementation. It addresses the different contributions of trees and their uses, as determiners for the arboreous implementation. Finally, a case study is carried out, focusing the district of Santo Amaro, where mapping the distribution of present arborization along with maps of apparent temperature, intra blocks open spaces, land use and road system help to analyze the areas with deficit of arborization by the identification of the arborization system. The understanding of this system allows the implementation of arborization in the most defficient areas in need of its benefits, such as softening temperature, air filtration and reduction of floading.
464

Análise do envolvimento do receptor de quimiocinas - CCR5 - na migração de células T reguladoras: correlação com o desenvolvimento de carcinoma espinocelular

Oliveira, Carine Ervolino de 07 June 2013 (has links)
Apesar dos avanços sobre a efetiva participação das células T reguladoras (Treg) na resposta imune antitumoral, ainda existem vários pontos que precisam ser esclarecidos. Visto que, os fatores que controlam a migração destas células para o microambiente tumoral ainda não estão totalmente definidos, o esclarecimento dos mecanismos de migração de células Treg no contexto do câncer poderia fornecer novos alvos para o desenvolvimento de terapias mais específicas. Diversos modelos de estudo demonstraram que o recrutamento preferencial de células Treg ao invés de outros tipos de células T pode ser explicado pela expressão diferencial de receptores de quimiocinas como o CCR5. Assim, é de extrema importância estabelecer qual é o papel de CCR5 na migração de células Treg em tumores induzidos quimicamente e seu envolvimento no desenvolvimento tumoral. Baseado no exposto, o presente estudo analisou o envolvimento de CCR5 na migração de células Treg e a sua correlação com o desenvolvimento de carcinoma espinocelular (CEC) induzido quimicamente. Os resultados obtidos demonstraram que camundongos geneticamente deficentes de CCR5 (CCR5KO) apresentaram baixo número de células Treg nas lesões e foram menos suscetíveis ao desenvolvimento de carcinoma espinocelular. Na fase de progressão tumoral verificou-se o desenvolvimento de CEC in situ por animais CCR5KO em combinação com a maior infiltração leucocitária, enquanto camundongos do grupo controle (WTCEC) apresentaram lesões de CEC bem diferenciado associado à elevada frequência de células Treg no microambiente tumoral e menor infiltração leucocitária. Interessantemente, a transferência adotiva de células Treg CCR5+ para animais CCR5KO (CCR5CEC Treg) resultou no acúmulo destas células no microambiente tumoral, elevado nível de CCL4, CCL17 e CCL22, e aumento da suscetibilidade desses animais à carcinogênese química. Verificou-se o desenvolvimento de CEC indiferenciado por animais CCR5CEC Treg e este foi associado à elevada frequência de macrófagos, células mielóides e dendríticas, linfócitos CD19+, T CD4+, T CD8+ e células Treg na fase de progressão tumoral. Outro aspecto relevante de nosso estudo foi à observação de que a transferência adotiva de células T CD4+CD25-CCR5+ para animais CCR5KO (CCR5CEC CD4+) induziu o desenvolvimento de CEC moderadamente diferenciado com características intermediárias as lesões observadas em animais WTCEC e CCR5CEC Treg. A transferência adotiva de células T CD8+CCR5+ para animais CCR5KO (CCR5CEC CD8+) promoveu o aparecimento precoce de papilomas e inibiu a progressão de papilomas para o CEC. A menor suscetibilidade à carcinogênese química de animais CCR5CEC CD8+ foi associada ao alto número de macrófagos, células mielóides, linfócitos B e T CD8+, células NK detectado nas lesões destes animais. Dessa forma, os resultados descritos estabelecem que a quimiotaxia de células Treg para o microambiente tumoral é dependente de CCR5 e estas células regulam aspectos críticos desta doença, sugerindo que o bloqueio da migração de células Treg CCR5+ seria uma importante estratégia imunoterapêutica no combate deste tipo de câncer. / Considering the advances on the effective participation of regulatory T cells (Treg) in the antitumor immune response, there are still several points that need to be clarified. The mechanisms that control the Treg cells migration to the tumor microenvironment are not completely defined, for these reason, establish these mechanisms could provide new targets for the development of more specific therapies. Several study models have demonstrated that preferential recruitment of Treg cells rather than other types of T cells can be explained by the differential expression of chemokine receptors such as CCR5. Thus, the present study examined the involvement of CCR5 in the migration of Treg cells and their correlation with the development of squamous cell carcinoma (SCC) chemically induced. The results showed that CCR5 knockout mice (CCR5KO) showed a low number of Treg cells in the lesions and these animals were less susceptible to the development of squamous cell carcinoma. SCC in situ was developed in CCR5KO mice and associated with high leukocytes infiltration, whereas the development SCC well differentiated in the control group (WTSCC) was associated with a high number of Treg cells and lower leukocyte infiltration in the tumor microenvironment. Interestingly, adoptive transfer of CCR5+Treg cells to CCR5KO mice (CCR5SCC Treg) resulted in the accumulation of these cells, high levels of CCL4, CCL17 and CCL22 in the tumor microenvironment and increased susceptibility to chemical carcinogenesis. CCR5SCCTreg mice developed SCC undifferentiated associated with a higher incidence of macrophages, myeloid and dendritic cells, CD19+, CD4+ T, CD8+ T lymphocytes, and Treg cells in the stage of tumor progression. Another relevant aspect of our study was the observation that adoptive transfer of CD4+CD25-CCR5+ T cells to CCR5KO animals (CCR5SCC CD4+) induced the development of SCC moderately differentiated with intermediate features observed in the WTSCC and CCR5SCC Treg mice. The adoptive transfer of CD8+CCR5+ T cells to CCR5KO mice (CCR5SCC CD8+) promoted the early incidence of papillomas and inhibited the progression to SCC. Reduced susceptibility to skin carcinogenesis in CCR5SCC CD8+ mice was associated with high frequency of macrophages, myeloid cells, B lymphocytes, CD8+ T lymphocyte and NK cells. In this study we showed that the migration of Treg cells to the tumor microenvironment is CCR5 dependent and that it regulates critical aspects of tumor development. The development of drugs that blocks CCR5+ Treg cells migration could be an important immunotherapeutic strategy to control this type of cancer.
465

Malariapigment Hemozoin und die funktionelle Hemmung von Monozyten

Schwarzer, Evelin 02 May 2000 (has links)
Malariapigment Hemozoin wird üblicherweise als nicht-toxische, hochmolekulare, parasitäre Speicherform des nicht abgebauten, toxischen Häms aus dem Wirtszell-Hämoglobins betrachtet. Unaufgereinigtes Pigment, wie wir es im infizierten Erythroyzten finden und wie es nach Schizontenruptur freigesetzt wird, kann man als die "natürliche Diät" bezeichnen, die Makrophagen in Malaria-infizierten Wirten aufnehmen. Nach Aufnahme in den Makrophagen persistiert Hemozoin in den Lysosomen und wird nicht abgebaut. Das Häm-abbauende Enzym, die Häm-Oxygenase wird nicht induziert. Hemozoin ist eine potente Quelle für Radikale, woraus Lipoperoxide und davon abgeleitete Hydroxyaldehyde,wie 4-Hydroxynonenal resultieren . 4- Hydroxynonenal in Konzentrationen, wie sie in Hemozoin-beladenen Monozyten nachgewiesen wurden, hemmen die Proteinkinase C. In immunopräzipitierter Proteinkinase C aus Hemozoin- haltigen Makrophagen wurden ProteinkinaseC-Hydroxynonenal-Komplexe nachgewiesen. Die Hydroxynonenal-bedingte Hemmung der Proteinkinase C (und anderer bisher nicht untersuchter Enzyme und Prozesse) könnte die Hemozoineffekte auf den oxydativen burst und die Phagozytose erklären. Der Phorbolester-induzierte oxydative burst ist irreversibel gehemmt in Monozyten, die entweder Hemozoin oder aber Hemozoin-haltige infizierte Erythrozyten phagozytiert haben. Die Hemmung der NADPH-Oxydase, das für den oxydativen burst verantwortliche Enzym, durch intrazelluläres Hemozoin, sollte beträchtlich zur burst -Hemmung beitragen. Monozyten phagozytieren Hemozoin-haltige, infizierte Erythrozyten oder isoliertes Hemozoin , sind danach jedoch unfähig, erneut zu phagozytieren, wie es Monozyten nach Phagozytose und Verdau von nicht-infizierten Erythrozyten physiologischerweise tun. Schließlich ist die Expression von Membranantigenen, die für die Immunantwort von Bedeutung sind, in Hemozoin-haltigen Monozyten vermindert. Die Induktion des für die Präsentation externer Antigene verantwortlichen Histokompatibilitätskoplexes (MHC) Klasse II durch Interferon-gamma ist in Hemozoin-beladenen Monozyten aufgehoben. Sowohl das Interzelluläre Adhäsionsprotein 1 (CD54) als auch p150,95 Integrin (CD11c) sind in Hemozoin-haltigen Monozyten vermindert Oberflächen-exprimiert. Trotz der verschiedenen funktionellen Einschränkungen sind Hemozoin-beladene Phagozyten vital. Bei Plasmodium-falciparum-Malaria enthält ein hoher Anteil von Gewebsmakrophagen und zirkulierender Monozyten und Leukozyten große Mengen an Hemozoin. Wichtige Funktionen wie oxydativer burst , Phagozytose und die Expression von MHC Klasse II sind in Hemozoin- beladenen Phagozyten gestört. Es scheint deshalb gerechtfertigt, die Hemozoin-Beladung als wichtigen Faktor in der gestörten Immunantwort bei der P.falciparum-Malaria zu betrachten. / Malaria pigment hemozoin is generally considered to be a non-toxic, high-molecular-weight, parasitic storage form of undigested,toxic, host-hemoglobin-heme.Crude pigment, as present in infected erythrocytes and shed after schizont rupture, may be considered the 'natural diet' ingested by macrophages in malaria-infected hosts. After ingestion by macrophages hemozoin persists in the lysosomes without being degraded. The heme-degrading enzyme, the heme-oxygenase, is not induced. Hemozoin is a powerfull source of radicals that generates lipoperoxides and derived, toxic hydroxyaldehydes such as 4-hydroxynonenal. High concentrations of 4-hydroxynonenal, which have been detected in hemozoin-fed macrophages, inhibit protein kinase C. Complexes between hydroxynonenal and protein kinase C have been detected in immunoprecipitated protein kinase C from hemozoin-fed macrophages. Hydroxynonenal-mediated inhibition of protein kinase C (and of other as yet unidentified enzymes and processes) may explain hemozoin-mediated effects on oxidative burst and phagocytosis. The phorbol ester-eliceted oxidative burst is irreversibly suppressed in monocytes fed with hemozoin or hemozoin-containing, infected erythrocytes. The inhibition of NADPH-oxidase, the enzyme responsible for oxidative burst, by ingested hemozoin should considerably contribute to burst inhibition. Monocytes avidly ingest infected hemozoin-containing erythrocytes or isolated hemozoin but are unable to repeat the phagocytic cycle as monocytes do after phagocytosis and digestion of non-infected erythrocytes. Finally , the expression of membrane antigens involved in the immune response is decreased in hemozoin-loaded monocytes. The induction of the major histocompatibility complex (MHC) class II by interferon-gamma, that is responsible for presentation of external antigens, is abrogated in hemozoin-loaded monocyte. The intercellular adhesion molecule 1 (CD54) as well as the p150,95 integrin (CD11c) are decreased on the surface of monocytes containing hemozoin. Despite multiple functional impairments, hemozoin-loaded phagocytes remain alive. In Plasmodium-falciparum malaria large portions of resident macrophages and circulating monocytes and leukocytes contain massive amounts of hemozoin. Important functions like oxidative burst, phagocytosis and the expression of MHC class II are severely impaired in hemozoin-fed phagocytes. It seems therefore likly that hemozoin loading may play an important role in the impairment of the immune response seen in P.falciparum malaria.
466

Análise da expressão gênica no dermatófito Trichophyton rubrum mimetizando a infecção in vitro: pH e diferentes fontes de carbono regulando genes / Analysis of gene expression in the dermatophyte Trichophyton rubrum during the mimetic infection in vitro: pH and carboun sources are regulating genes

Maranhão, Fernanda Cristina de Albuquerque 12 December 2008 (has links)
Dermatófitos são fungos filamentosos com a habilidade de invadir substratos queratinizados e causar dermatofitoses em humanos e animais, penetrando profundamente apenas em hospedeiros imunocomprometidos. Trichophyton rubrum é um fungo antropofílico e cosmopolita, o mais comum agente de micoses superficiais, que usa componentes celulares como proteínas e lipídeos após uma específica regulação de sua expressão gênica governada pelo pH ambiente e sensoriamento celular. A virulência de T. rubrum é relacionada com a secreção de enzimas proteolíticas, um importante fator determinante na invasão, utilização e subseqüente disseminação através do estrato córneo. O objetivo desse estudo foi identificar através de Hibridização Subtrativa Supressiva (SSH) genes de T. rubrum preferencialmente expressos durante o crescimento na presença de queratina e lipídeos, quando T. rubrum degrada fontes de carbono tipicamente encontradas em células epidérmicas. Inicialmente, nós avaliamos as mudanças no pH extracelular durante seu crescimento em queratina e lipídeo (depois de 6, 12, 24, 48, 72 h e 7 dias) em pH inicial 5,0, onde foi observado um gradual aumento do pH basal sob ambas as condições de teste, comparado com a condição glicose (controle). Também identificamos 576 transcritos de T. rubrum diferencialmente expressos por SSH usando conídios cultivados por 72 h em queratina como teste e em glicose como controle. Os genes de T. rubrum ativados codificam proteínas putativas que foram validadas por cDNA dot-blot e northern blot, mostrando similaridade com proteínas fúngicas envolvidas no metabolismo básico, crescimento e virulência, p. ex., transportadores ABC-MDR, MFS e ATPase de cobre, permease, NIMA interactive protein, poliproteína Gag-Pol, fatores de virulência subtilisinas serino-proteases (Sub 3 e 5) e metaloproteases (Mep 3 e 4) e Hsp30. Adicionalmente, entre os 762 clones obtidos na biblioteca da condição lipídeo (72 h), 80 transcritos superexpressos foram confirmados por cDNA dot-blot, revelando 14 unigenes similares à proteínas de vários organismos patogênicos, como glicoproteína 43 kD, transportador MDR, proteína G, quitina sintase e serino/treonina fosfatase. Transcritos do gene TruMDR2, codificador de um transportador ABC, foi isolado tanto na presença de queratina quanto em lipídeo, e a análise da linhagem mutante TruMDR2 de T. rubrum mostrou uma redução na atividade infectante, caracterizada pelo baixo crescimento em unhas humanas comparada com o tipo selvagem. A alta expressão de transportadores por T. rubrum em condições que mimetizam a infecção e a redução na virulência de TruMDR2 durante o modelo in vitro sugerem que transportadores estão envolvidos na patogenicidade de T. rubrum. Outro linhagem mutante (pacC-1) com um nocaute no gene pacC que codifica um fator de transcrição regulado pelo pH local, mostrou a expressão de proteases (Sub 3 e 5 e Mep 4) diminuída após o crescimento em queratina em comparação com o tipo selvagem em análises de northern blots. Essas proteases tem uma atividade ótima em pH alcalino, e nossos resultados indicam uma regulação defectiva do gene pacC de T. rubrum na ativação de proteases. Em conclusão, através do uso de SSH foi possível identificar genes de T. rubrum ativados após tratamentos específicos, o que sugere a importância dos mesmos na interação dermatófito-hospedeiro, instalação e manutenção da doença. Esses resultados disponibilizam novos dados sobre T. rubrum que levarão a um melhor entendimento dos mecanismos moleculares envolvidos no crescimento, metabolismo geral e patogenicidade, e também auxiliar na identificação de novos e efetivos alvos de drogas para dermatófitos. / Dermatophytes are a group of fungi filamentous that have the ability to invade keratinized substrates, causing dermatophytosis in humans and animals and only penetrate deeper if the host is immunocompromised. Trichophyton rubrum is an anthropophilic and cosmopolitan fungi, the most common agent of superficial mycoses, which uses cell components such as proteins and lipids after a specific regulation of its gene expression governed by pH environment and sensing cell. The virulence T. rubrum is related to secretion of proteolytic enzymes, an important factor determinant in the invasion, utilization and subsequently dissemination through the stratum corneum. The aim of this study was to indentify by Suppression Subtractive Hybridization (SSH) T. rubrum genes preferentially expressed during growth in the presence of keratin and lipids, upregulated when this fungus degrades carbon source typically found at epidemic cells. Initially, this work evaluated the changes in the extracellular pH during its growth in keratin and lipid (after 6, 12, 24, 48, 72 h and 7 days) at initial pH 5.0, where we observed a gradual increase of basal pH under both tests when compared to glucose condition (control). Also, we identified 576 T. rubrum transcripts differentially expressed by SSH using conidia cultivated for 72 h in keratin as tester, and in glucose as driver. The T. rubrum genes upregulated encode putative proteins that were validated by cDNA dot-blot and northern blot, showing similarity to fungi proteins involved in basic metabolism, growth and virulence, i.e., transporters ABC-MDR, MFS and ATPase of copper, permease, NIMA interactive protein, Gag-Pol polyprotein, virulence factors serine-protease subtilisins (Sub 3 and 5) and metalloproteases (Mep 3 and 4) and Hsp30. Additionally, among the 762 clones obtained in a library of lipid condition (72 h), 80 over-expressed transcripts were confirmed by cDNA dot-blot, revealing 14 unigenes similar to proteins of several pathogenic organisms, like glicoprotein 43 kD, MDR transporters, G protein, chitin synthase and serine/threonine-protein phosphatase. Transcripts of TruMDR2 gene, encoding an ABC transporter in T. rubrum, were isolated in the presence of keratin and lipid, and the examination of TruMDR2 mutant T. rubrum showed a reduction in infecting activity, characterized by low growth in human nails compared to wild-strain. The high expression of transporter by T. rubrum in conditions that mimetize the infection and the virulence reduction of TruMDR2 in an in vitro model suggests that transporters are involved in T. rubrum pathogenicity. Another mutant, pacC-1 with a knockout in PacC gene that encodes a transcription factor regulated by local pH, showed the expression of proteases (Sub 3, Sub 5 and Mep 4) decreased after growth in keratin (72 h) in comparison to wild-strain in northern blot analyzes. These proteases have an optimal activity in alkaline pH, and our results indicate a defective regulation of T. rubrum pacC gene in the activation of proteases. In conclusion, by means of SSH to identify genes upregulated in T. rubrum after specific treatments, their importance in the dermatophyte-host interaction, installation and maintenance in the disease is suggested. These results provide new insights about T. rubrum that will contribute to a better understanding of molecular mechanisms about the growth, metabolism and pathogenicity, and may also aid in the identification of novel effective drug targets for dermathophytes.
467

Análise do envolvimento de células T reguladoras na hanseníase

Lima, Hayana Ramos 16 October 2012 (has links)
A hanseníase é uma doença crônica causada por Mycobacterium leprae e apresenta diversas formas clínicas. O entendimento da interação parasita-hospedeiro na hanseníase evidenciou que ocorre a persistência assintomática do patógeno, caracterizando um estado de latência. Os fatores mais importantes relacionados com a permanência do patógeno são: a patogenicidade do agente infeccioso e o perfil da resposta imune, no qual os eventos de migração celular, produção de citocinas, as células efetoras e reguladoras são extremamente relevantes. As células T reguladoras (Treg) desempenham papel central na regulação da resposta imune em infecções crônicas o que favorece a persistência do patógeno. A importância de células T reguladores na hanseníase ainda é pouco conhecida. Neste trabalho investigou-se a presença de células T reguladoras em lesões e sangue periférico de indivíduos com hanseníase. Inicialmente avaliou-se a proliferação e a produção de citocinas por células mononucleares do sangue periférico (PBMC) de pacientes com hanseníase. Os resultados evidenciaram que não há diferenças quanto à proliferação de células T e produção de IFN-γ e TNF-α por células desses pacientes, mas a produção de IL-4 e IL-5 foi detectada apenas entre os pacientes com hanseníase virchoviana. Em relação à presença de células T reguladoras, os resultados evidenciaram aumento no número de linfócitos T CD4+CD25+FoxP3+ no sangue periférico de pacientes com hanseníase virchoviana. As células T reguladoras dos pacientes com hanseníase apresentaram elevada expressão de moléculas co-inibitórias PD-1, CTLA-4, GITR e ICOS. De modo relevante, as células T CD4+CD25+ isolados de pacientes com hanseníase virchoviana apresentaram maior atividade supressora quando comparado às células isoladas de pacientes com hanseníase tuberculóide. As células T CD4+CD25+ de pacientes com hanseníase virchoviana inibiram a proliferação de PBMC alogênico e a produção de IFN-γ e TNF-α. Os resultados demonstraram também que nas amostras de lesão de pele de pacientes com hanseníase virchoviana há acúmulo de células CD25+ produtoras de IL-10 e TGF-β, enquanto que estas células não foram detectadas nas lesões de pacientes com hanseníase tuberculóide. Dessa forma, os resultados descritos indicam que pacientes com hanseníase virchoviana apresentam aumento no número de células T reguladoras circulantes e no infiltrado inflamatório, e estas células apresentaram maior atividade supressora. O acúmulo de células T reguladoras no sítio da infecção pode ser correlacionado com o controle da resposta imune e conseqüente persistência de M. leprae. / Leprosy is caused by Mycobacterium leprae and its clinical features depend on the host immune background. The understanding of parasite-host interactions in leprosy have highlighted asymptomatic persistence of the pathogen, which indicates that this infection becomes latent. The most important factors related to the permanence of pathogens are: the pathogenicity of the infectious agents; the profile of the immune response developed by the host whose events of cellular migration, cytokines production, and the effector and regulatory cells are extremely relevant. The regulatory T cells (Treg) seem to play a central role in the regulation of the immune response in chronic infections, which favors the persistence of the pathogen. Herein, we analyzed the relation between tuberculoid and lepromatous leprosy with the presence and function of T regulatory cells from peripheral blood mononuclear cells (PBMC) and skin lesions from these patients. First, the proliferation and cytokine production of PBMC isolated from leprosy patients were analyzed. We did not observe any difference in the proliferation ability or IFN-γ and TNF-α release; however, the production of IL-4 and IL-5 was detected only in patients with lepromatous leprosy. Furthermore, T CD4+CD25+FoxP3+ cells were detected in the PBMC of patients with leprosy and these cells from lepromatous patients showed high expression of co-inhibitory molecules such as PD-1, GITR, CTLA-4 and ICOS. T CD4+CD25+cells isolated from patients with lepromatous leprosy were significantly more suppressive than the cells obtained from tuberculoid patients. In addition, TCD4+CD25+ cells isolated from patients with lepromatous leprosy inhibited allogeneic PBMC proliferation and their production of IFN-γ and TNF-α. The results also demonstrated that IL- 10 and TGF-ß were co-expressed with CD25+ cells at the inflammatory infiltrate of skin lesions from lepromatous patients, but similar results were not detected among tuberculoid patients. Thus, these results indicate that lepromatous leprosy patients have an enhanced presence of Treg cells with a suppressive ability in the blood and in the inflammatory infiltrate. The accumulation of Treg cells at the infection sites might be associated to the control of immune response and consequently to Mycobacterium leprae presistence.
468

Estudo, projeto e implementação de sistemas UPQC/UPS trifásicos aplicados no condicionamento ativo de energia elétrica / Study, design and implementation of an UPQC/UPS systems applied in three-phase active power conditioning

Modesto, Rodrigo Augusto 11 February 2015 (has links)
Este trabalho apresenta o estudo, análise e a implementação de três topologias de condicionadores ativos de energia elétrica, utilizados para a melhoria da qualidade da energia em sistemas elétricos trifásicos a quatro fios. Estes condicionadores de qualidade de energia podem trabalhar tanto como um condicionador unificado de qualidade de energia (UPQC), bem como uma fonte de alimentação ininterrupta (UPS), permitindo: (i) a supressão das correntes harmônicas da carga; (ii) a compensação de energia reativa da carga; (iii) compensação dos desequilíbrios das correntes de carga; (iv) a compensação de desequilíbrios de tensão da rede; (v) supressão das tensões harmônicas da rede elétrica; (vi) a regulação das tensões de saída (tensões de carga); e (vii) fornecimento de energia ininterrupta para as cargas críticas (sistema UPS). Dentre as três topologias de UPQC/UPS estudadas, uma delas é proposta neste trabalho com o intuito de reduzir a tensão no barramento CC. Além disso, todas as topologias em estudo são constituídas por dois conversores PWM, nos quais é adotada uma estratégia de controle dual. Desse modo, o conversor colocado em paralelo com a carga, funciona como uma fonte de tensão senoidal, enquanto que o conversor colocado em série entre a rede elétrica e a carga, é controlado para operar como uma fonte de corrente senoidal. Tanto os controladores de tensão, quanto os de corrente são implementados no referencial síncrono dq0. Além disso, a técnica de modulação vetorial espacial tridimensional (3-D-SVM) é empregada nos conversores. Testes experimentais são apresentados para validar o desenvolvimento teórico e verificar o bom desempenho estático e dinâmico dos condicionadores ativos de energia elétrica, operando como UPQC, bem como sistema UPS. / This work presents the study, analysis and implementation of three topologies of active power conditioners, which are used to improve the power quality in three-phase four-wire systems. These power quality conditioner can work as unified power quality conditioner (UPQC), as well as an uninterruptible power supply (UPS) system allowing: (i) suppression of load harmonic currents; (ii) compensation of load reactive power; (iii) load unbalances compensation; (iv) utility voltage unbalances compensation; (v) utility voltage harmonics suppression; (vi) regulation of the output voltages (load voltages); and (vii) uninterruptible power for critical loads when working as UPS system. Among the three topologies of UPQC/UPS studied, one of them is proposed in this work in order to reduce the DC-bus voltage. Besides, all the topologies are comprised of two PWM converters, where a dual control strategy is adopted. The first converter, which is placed in parallel with the load, operates as a sinusoidal voltage source, while the second, which is placed in series between the utility grid and the load, is controlled to operate as a sinusoidal current source. Both the voltage and current controllers are implemented into the synchronous rotating reference frame (dq0-axes). In addition, the series and parallel converters use the three-dimensional space vector modulation (3-D-SVM) technique. The experimental tests are presented to validate the theoretical development and to verify the effective static and dynamic performance of the proposed active power conditioners, operating as UPQC and UPS.
469

Development of a novel diffuse correlation spectroscopy platform for monitoring cerebral blood flow and oxygen metabolism: from novel concepts and devices to preclinical live animal studies

Sutin, Jason 09 March 2017 (has links)
New optical technologies were developed to continuously measure cerebral blood flow (CBF) and oxygen metabolism (CMRO2) non-invasively through the skull. Methods and devices were created to improve the performance of near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) for use in experimental animals and humans. These were employed to investigate cerebral metabolism and cerebrovascular reactivity under different states of anesthesia and during models of pathological states. Burst suppression is a brain state arising naturally in pathological conditions or under deep general anesthesia, but its mechanism and consequences are not well understood. Electroencephalography (EEG) and cortical hemodynamics were simultaneously measured in rats to evaluate the coupling between cerebral oxygen metabolism and neuronal activity in the burst suppressed state. EEG bursts were used to deconvolve NIRS and DCS signals into the hemodynamic and metabolic response function for an individual burst. This response was found to be similar to the stereotypical functional hyperemia evoked by normal brain activation. Thus, spontaneous burst activity does not cause metabolic or hemodynamic dysfunction in the cortex. Furthermore, cortical metabolic activity was not associated with the initiation or termination of a burst. A novel technique, time-domain DCS (TD-DCS), was introduced to significantly increase the sensitivity of transcranial CBF measurements to the brain. A new time-correlated single photon counting (TCSPC) instrument with a custom high coherence pulsed laser source was engineered for the first-ever simultaneous measurement of photon time of flight and DCS autocorrelation decays. In this new approach, photon time tags are exploited to determine path-length-dependent autocorrelation functions. By correlating photons according to time of flight, CBF is distinguished from superficial blood flow. Experiments in phantoms and animals demonstrate TD-DCS has significantly greater sensitivity to the brain than existing transcranial techniques. Intracranial pressure (ICP) modulates both steady-state and pulsatile CBF, making CBF a potential marker for ICP. In particular, the critical closing pressure (CrCP) has been proposed as a surrogate measure of ICP. A new DCS device was developed to measure pulsatile CBF non-invasively. A novel method for estimating CrCP and ICP from DCS measurement of pulsatile microvascular blood flow in the cerebral cortex was demonstrated in rats. / 2018-03-08T00:00:00Z
470

Sincronização de Disparos Neuronais no Córtex

Lameu, Ewandson Luiz 25 October 2016 (has links)
Made available in DSpace on 2017-07-21T19:25:53Z (GMT). No. of bitstreams: 1 Lameu, Ewandson Luiz.pdf: 7848775 bytes, checksum: 6554423cbb845e57ef8b0353b78352c9 (MD5) Previous issue date: 2016-10-25 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / In this thesis we present a theoretical model of a neural network based on real anatomical structure of connections between cat’s cerebral cortex areas. This anatomical network contains 65 cortical areas organized into four regions called visual, auditory, somatosensory-motor and frontolimbic. We analize for which probabilities of connections the proposed network approaches with greater fidelity the real anatomical network. To describe the neuron dynamics we use a system known as Rulkov bidimensional map, which is a phenomenological model that simulates the changes in the neuronal membrane potential. For the coupling between neurons we consider electrical and chemical synapses. Then, we study the phenomenon of synchronization of neuronal firing due to its relationship with some neurological disorders such as Parkinson’s disease and epilepsy. In addition to seeking the cause of these disorders, the study of effective techniques to prevent such behavior becomes indispensable. In light of this, we propose three methods of applying external perturbations over the system with the aim of suppress synchronization. The first of these disorders simulates a stimulus by light that is capable of inducing a neuron to have a spike, the second perturbation used was the introduction of a periodic electrical current on the network, and the third was based on reinjection of an electric signal collected from the system itself. We show the coupling intervals where disturbances are able to suppress the synchrony and evaluate which of them has higher efficiency. / Nesta tese apresentamos um modelo teórico de uma rede neuronal baseado na estrutura anatõmica real das conexões entre áreas do córtex cerebral do gato. Esta rede anatômica contém 65 áreas corticais que estão organizadas em quatro regiões denominadas visual, auditiva, somatosensorialmotora e frontolımbica. Analisamos para quais probabilidades de conexões a rede modelada se aproxima com maior fidelidade da rede real anatomica. Para descrever a dinãmica neuronal consideramos um sistema bidimensional conhecido como mapa de Rulkov, sendo este um modelo fenomenol´ogico que simula as variações do potencial de membrana neuronal. Para o acoplamento entre os neuronios consideramos sinapses eletricas e quımicas. Entao, estudamos o fenomeno da sincronização dos disparos neuronais devido a sua relação com algumas desordens neurológicas, como Parkinson e epilepsia. Além de buscar compreender a causa destas desordens, o estudo de tecnicas eficazes para evitar tais comportamentos torna-se imprescindıvel. Com isso em mente, propomos tres métodos de aplicações de perturbações externas sobre o sistema com a finalidade de suprimir a sincronizaçãoo. A primeira destas perturbaçoes simula um estımulo por luz que é capaz de induzir um neuronio a ter um pico de potencial, a segunda perturbação utilizada foi a introdução de uma corrente eletrica periodica sobre a rede e a terceira baseou-se na reinjeção de uma sinal eletrico coletado do proprio sistema. Mostramos os intervalos de acoplamento onde as perturbacoes sao capazes de suprimir a sincronia e avaliamos qual delas apresenta maior eficiencia.

Page generated in 0.0679 seconds