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  • 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.
51

Molecular Insights into Lymphoid Malignancy : Role of Transcription Factor BCL11B in T-cell Leukemia Genesis and Biochemical Characterization of DNA Binding Domain of RAG1

Deepthi, R January 2017 (has links) (PDF)
The lymphoid tissues consist of distinct cell subpopulations of B and T cell lineages and possess complex signaling pathways that are controlled by a myriad of molecular interactions. During the fine-tuned developmental process of the lymphoid system, inappropriate activation of oncogenes and loss of tumor suppressor gene activity can push lymphocytes into uncontrolled clonal expansion, causing several lymphoid malignancies. V(D)J recombination is one such essential process, important for the proper development of the mammalian immune system. However, mistakes in normal V(D)J recombination can lead to deletion of tumor suppressor genes or activation of proto-oncogenes. In the first part of the study, the physiological and pathological roles of DNA binding domain of RAG1 have been characterized. RAG (Recombination Activating Gene) complex consisting of RAG1 and RAG2, is a site specific endonuclease responsible for the generation of antigen receptor diversity. It cleaves a specific DNA sequence termed as recombination signal sequence (RSS), comprising of a conserved heptamer and nonamer. Recent studies have shown that RAGs can also act as a structure-specific nuclease by cleaving flaps, heterologous loops, bubbles, hairpins etc. Nonamer binding domain (NBD) of RAG1 plays a central role in the recognition of RSS during its sequence specific activity. To investigate its DNA binding properties, NBD of murine RAG1 was cloned, overexpressed and purified from E. coli. Electrophoretic mobility shift assays showed that NBD binds with high affinity to nonamer in the context of 12/23 RSS. However, it did not bind to heteroduplex DNA, irrespective of the sequence of the single-stranded region. Interestingly, when a nonamer was present next to a heteroduplex DNA, NBD exhibited robust binding. NBD binding was specific to thymines when single stranded DNA containing poly A, C, G and T were used. Biolayer interferometry studies showed that the observed poly T binding to NBD was robust with a binding constant of 0.45±0.16 µM. >23 nt was essential for NBD binding at homothymidine stretches. On a double-stranded DNA, NBD could bind to A:T stretches, but not G:C stretches or random sequences. Although NBD is indispensable for sequence-specific activity of RAGs, external supplementation of purified nonamer binding domain to NBD deleted cRAG1/cRAG2 did not restore the sequence specific activity, suggesting that the overall domain architecture of RAG1 is important for maintaining its properties. Therefore, we define the sequence requirements of NBD binding to double- and single-stranded DNA, which will have implications in generation of chromosomal rearrangement and genomic instability in lymphoid cells. Genetic alterations are one of the hallmarks of lymphoid malignancies. Many genes involved in chromosomal abnormalities are known to play central roles in the development of normal lymphocytes. In the second part of the study, molecular mechanism associated with fragility of the transcription factor, B cell leukemia 11B (BCL11B) that drives malignant transformation of T-cells has been studied. BCL11B is a zinc finger protein transcription factor with multiple functions. It plays a key role in both development and subsequent maintenance of T-cells. BCL11B gene alterations are implicated in a number of diseases including T-cell malignancies. It acts as a haplo-insufficient tumor suppressor and loss of BCL11B allele leads to susceptibility to mouse thymic lymphoma and human T-ALL. Recent studies reveal heterozygous BCL11B mutations and deletions across each of the major molecular subtypes of T-ALL (15% of patients). Most of the BCL11B missense mutations identified so far affected the residues within BCL11B zinc finger domains of the exon 4. However, mechanism of generation of such specific mutations leading to altered functions of BCL11B remains to be explored. In the present study, we address the potential mechanism of fragility of BCL11B gene during leukemia genesis. Firstly, we have evaluated different regions of BCL11B gene for presence of non-B DNA sequence motifs. Studies using non-B DB database reveal clustering of several non-B DNA forming motifs at the region spanning exon 4 of BCL11B gene. In order to biochemically evaluate the potential of non-B DNA structure formation, two different regions of exon 4 were PCR amplified and cloned. Using bisulfite modification assay we demonstrate that, single strandedness exists at both region I and II of BCL11B exon 4, when the region is present on a plasmid DNA. Bisulfite reactivity on chromosomal DNA confirmed existence of such altered DNA structures in the context of human genome. In vitro gel shift assays showed formation of both intra and intermolecular G-quadruplexes. Primer extension studies revealed that non-B DNA structures could block polymerization during replication on a plasmid, leading to DNA replication arrest. Extrachromosomal assays showed that non-B DNA structure motifs, in contrast to its mutants, blocked transcription leading to reduced expression of green fluorescent protein (GFP) within cells. Many non-B DNA-forming sequences have been mapped to regions of common chromosomal breakpoints in human tumors, known as “hotspots”, which are associated with leukemia, lymphomas and genomic disorders. Thus, alternative DNA conformations are believed to contribute to mutations, deletions and other genetic instability, leading to the deregulation of cancer-related genes in malignant diseases such as leukemia and lymphoma. Activation induced cytidine deaminase (AID), is an essential enzyme involved in antibody diversification of immunoglobulin genes. However, aberrant AID expression in B- cell and non-B cell background is reported in various cancers including leukemia and lymphoma. AID activity requires single stranded DNA (ssDNA) as a substrate. Since activation induced cytidine deaminase (AID) deaminates cytosines when present on a single stranded DNA and its expression is deregulated in many cancers, we investigated the role of AID in BCL11B gene mutagenesis. We observed substantial AID expression in many T-cell leukemic cell lines. Thus, we hypothesize that AID might be targeted to single stranded DNA present at BCL11B exon 4 due to formation of non-B DNA structures such as G-quadruplexes causing AID mediated deamination, further leading to nucleotide alterations and the mutational signature observed at BCL11B exon 4 resulting in T-ALL. Based on our findings, we propose that single strandedness resulted due to formation of non-B DNA structures such as G-quadruplex DNA, triplex DNA or cruciform DNA during physiological processes like DNA replication and transcription at exon 4 of BCL11B, can act as the target for AID. Thus, our findings uncover a new possible link between non-B DNA structure motifs and AID expression in causing mutations at BCL11B exon 4 which could lead to T cell leukemia genesis. BCL11B is a bifunctional transcriptional regulator that can act as a repressor and transactivator, and is known to differentially control the expression of specific genes in a context-dependent manner. In order to understand the transcriptional network involving BCL11B, it was cloned, overexpressed and purified from E. coli. To investigate the DNA binding properties of BCL11B protein, electrophoretic mobility shift assays were performed. Our results lead to identification of a specific sequence motif that is responsible for DNA binding. Competition experiments in presence of specific and nonspecific oligomers further confirmed the binding specificity. Thus, in the present study, we have characterized the binding properties of nonamer binding domain of RAG1, emphasizing its pathological relevance in causing genomic instability in lymphoid cells. The study may help in better understanding of RAG induced genomic instability in lymphoid tissues and role of aberrant AID expression in inducing mutations at BCL11B Zinc finger domain, leading to its deregulation and culminating into T-cell leukemia
52

The Role of ADAM10 in the Immune System: Maintenance of Lymphoid Architecture, MDSC Development and Function, B cell Derived Exosomal Antigen Presentation, and B1 cell IgE Production.

Martin, Rebecca 25 April 2014 (has links)
ADAM10 is a zinc-dependent metalloprotease. ADAM10 has emerged as a key regulator of cellular processes by cleaving and shedding extracellular domains of multiple transmembrane receptors and ligands. In this study, we examined the role of ADAM10 in the immune system. Here, we show that knocking out ADAM10 on the mature B2 cell causes a defect in the development of secondary lymphoid architecture that becomes more severe post-immunization. We also show that overexpression of ADAM10 leads to a defect in hematopoiesis, which eliminates B2 lymphocyte development. This defect additionally induces accumulation of myeloid derived suppressor cells, MDSCs. ADAM10Tg MDSCs function synonymous to tumor MDSCs. Of the two subpopulations of MDSCs, granulocytic MDSCs increase parasitic clearance in a model of N. brasiliensis. Monocytic MDSCs are more immunosuppressive in regards to tumor. Both subpopulations are dependent on the presence of mast cells for activity. It is thought that this relationship is mediated through histamine and IL-13. During N. brasiliensis infection, ADAM10Tg mice, lacking B2 B cells but having intact B1 B cells, makes increased IgE over WT mice. This production of IgE is thought to be produced by the B1 cells. Of the two types of B1 cells, B1a cells make the majority of the IgE. This IgE production is enhanced by MDSC accumulation and can be induced by MDSC adoptive transfer in a parasite-free mouse. Lastly, ADAM10 is the key sheddase for CD23 on B2 cells. When IgE is bound to its antigen to form an immune complex, IC, it binds CD23 and is internalized. After CD23 bound to IgE ICs is internalized, it is sorted into bexosomes. These bexosomes are transferred to dendritic cells which are responsible for presenting to T cells and inducing an increased antigen-specific immune response. Overall, ADAM10 is important for many aspects of the immune response.
53

Distribuição anatômica e histológica dos componentes do tecido linfóide ao longo do intestino de avestruz (Struthio camelus) / Anatomic and histhologic distribuition of the lymphoid tissue components in the intestin of ostrich

Saviani, Gisele 25 February 2005 (has links)
O avestruz (Struthio camelus), embora compartilhe de muitas adaptações evolucionárias de outros pássaros, possui algumas características anatômicas relacionadas com o seu tubo digestivo que são únicas, entre as quais podemos citar o cólon que se apresenta maior que o ceco (aparece duplicado) . Há algum tempo esta ave têm sido explorada economicamente, principalmente na alimentação como uma carne alternativa para o consumo humano. O presente trabalho tem como objetivo estudar as estruturas anatômicas e histológicas do intestino ligadas a distribuição do tecido linfóide . No estudo foram utilizados vinte e quatro avestruzes, com idade entre 2 meses e 2,5 anos, sendo animais destinados ao abate. Para a descrição morfológica utilizou-se a metodologia preconizada Bezuindenhout (1986) e o método de rotina para coloração hematoxilina e eosina. Esperamos contribuir na multiplicação de conhecimentos na área da estrutiocultura. / Although the ostrich shares a lot of evolutionary adaptation with other birds, it presents some anatomical characteristics concerning its digestive tube that are unique, like the colon for instance. The ostrich?s colon is bigger than its caecum. The caecum is doubled. The caecum is folded. This bird has been economically exploited, mainly because of its meat as an alternative food for humans. The purpose of the present research is to study the anatomical and histological structures connecting them to the lymphoid tissue distribution. In this study, 24 ostriches between the ages of 2 months and 2 years and a half ? when they?re ready to be slaughtered ? were used. In order to describe the study, the Bezuindenhout methodology and the routine method for printing H. E. and eosine were used.
54

Estudos estruturais e funcionais de Tsa1 de Saccharomyces cerevisiae: um modelo biológico para o estudo de inibidores de crescimento celular para leucemia linfoide aguda / Functional and structural evaluation of Tsa1 from Saccharomyces cerevisiae: a biological model for study of cellular growth inhibitors for acute lymphocytic leukemia

Santos, Melina Cardoso dos 01 June 2017 (has links)
As peroxirredoxinas (Prx) são enzimas antioxidantes que se destacam pela capacidade de decompor uma grande variedade de hidroperóxidos com elevada eficiência (106-108M-1s-1), mantendo essas moléculas em níveis adequados à homeostase celular. Entretanto, já foi demonstrado que em diversos tipos tumorais os níveis de Prx são extremamente aumentados e experimentos envolvendo sua inativação resultam na diferenciação ou apoptose de células tumorais. Recentemente, foi descoberto um diterpenóide denominado adenantina que seria o primeiro inibidor para as Prx1 e Prx2 de humanos e foi demonstrada que sua aplicação em células de leucemia mieloide aguda promoveu diferenciação ou apoptose dessas células. Nesse contexto, o presente trabalho apresenta duas vertentes: 1) A caracterização das alterações estruturais e funcionais promovidas pela ligação da adenantina ao sítio ativo das Prx utilizando Tsa1 de Saccharomyces cerevisiae como modelo biológico, em função da sua alta similaridade com Prx2 de humanos; 2) Avaliação da atividade antitumoral dose dependente de adenantina sobre as linhagens celulares REH e MOLT-4 de leucemia linfoide aguda. No que concerne à primeira linha de investigação, nossos resultados revelam que Tsa1 é suscetível à inibição por adenantina, uma vez que o tratamento reduziu em ~66 % a velocidade de decomposição de peróxido de hidrogênio. Adicionalmente, a mutação da Thr44 de Tsa1, pertencente à chamada tríade catalítica, por uma Ser resultou em uma proteína mais suscetível a alterações na estrutura secundária e à inibição da atividade peroxidásica em função da ligação com adenantina, apresentando uma diminuição de ~85% na velocidade de reação. Características semelhantes foram observadas para a proteoforma Tsa2 de S. cerevisiae, que carreia naturalmente a substituição da Thr44 pela Ser. Análises de sequências de Prx em bancos de dados revelaram que majoritariamente proteínas contendo Ser são encontradas em organismos procariotos, muitos deles patogênicos. Finalmente, demonstramos por meio de ensaios citotoxicidade que as bactérias Staphylococcus aureus e Staphylococcus epidermidis, que possuem uma Ser na tríade catalítica, têm seu crescimento inibido pelo tratamento com adenantina (IC50 de 460µM e 77µM, respectivamente), enquanto que para Escherichia coli, que possui Thr nessa posição, a toxicidade da adenantina foi bastante baixa (não foi possível determinar o IC50 nas condições utilizadas). Dessa forma, os dados apresentados neste trabalho demonstram o potencial da utilização da adenantina tanto como antibiótico quanto como antileucêmico. / Peroxiredoxins (Prx) are antioxidant enzymes which stand out due the ability to decompose a wide variety of hydroperoxides with high efficiency (106-108M-1s-1) maintaining these molecules at suitable levels to cellular homeostasis and participating in several signaling events. However, it has been shown that, in many tumor types, Prx levels are extremely increased and experiments involving its inactivation have resulted in differentiation or apoptosis of tumor cells. It was recently found a diterpenoid, called adenanthin, that would be the first human Prx1 and Prx2 inhibitor and it was demonstrated that its application in acute myeloid leukemia cells was able to promote differentiation or apoptosis. In this context, this work presents two lines of research: 1) Characterization of structural and functional changes promoted by adenanthin binding to Prx active site using Tsa1 from Saccharomyces cerevisiae as biological model, due to its high similarity to human Prx2. 2) Evaluation of adenanthin dose-dependent antitumor activity over the acute lymphoid leukemia cell lines REH and MOLT-4. As regards the first line of research, our result reveal that Tsa1 is susceptible to inhibition by adenanthin, since the treatment with this binder reduced the hydrogen peroxide decomposition velocity in ~ 66%. In addition, the replacement of Thr44 from Tsa1, aminoacid belonging to the so-called catalytic triad, by a Ser resulted in a protein more susceptible to alterations in secondary structure and to peroxidase activity inhibition in function of adenanthin binding, presenting ~85% of decrease in reaction velocity. Similar characteristics were observed for Tsa2 proteoform from S. cerevisiae, which naturally carries the substitution of Thr44 by Ser. Prx sequences analyzes in databases revealed that mostly Ser-containing proteins are found in prokaryotic organisms, many of them pathogenic ones. Finally, we demonstrate through cytotoxicity assays that the bacteria Staphylococcus aureus and Staphylococcus epidermidis, which have a Ser in catalytic triad, have their growth inhibited by adenanthin treatment (IC50 of 460µM and 77µM, respectively), whereas for Escherichia Coli, which has Thr at that position, the tocyxicity of adenanthin was quite low (it was not possible to determine the IC50 under the used conditions). Regarding the second line of investigation, we found that adenanthin is able to induce the death of leukemic cell lines REH and MOLT-4, and for the last one, there was an unexpected proliferation of cells treated by the longest incubation period (72 hours), characterizing a possible indication of differentiation process. In this sense, the data presented here demonstrate the potential of adenanthin use in both antibiotic and antileukemic treatments.
55

Aspectos quantitativo e biomolecular da vascularização do timo em gatos / Quantitative and biomolecular aspects of the thymus vascularization in cat

Barroso, Camila Ercolini 31 May 2012 (has links)
O sistema linfoide é composto de órgãos linfoides primários e secundários. O timo é um órgão linfoide primário responsável pela maturação, diferenciação e seleção da linhagem linfocitária do tipo T que é responsavel pela imunidade celular do individuo. Para cumprir estas funções, o timo possui uma disposição peculiar das suas células epiteliais morfologicamente distintas e de suas estruturas vasculares. Seus vasos sanguíneos possuem um papel na oxigenação tecidual e no processo de migração das células precursoras de linfócitos T para o interior do parênquima tímico e por isso apresentam uma arquitetura típica caracterizada por vasos de grande calibre, localizados na junção cortico-medular e uma fina rede de ramos e anastomoses que se estendem para o córtex. Este processo de estruturação e arquitetura vascular ainda possui sua base molecular desconhecida, assim como os mecanismos que provocam a involução do órgão. O VEGF é um fator angiogênico que atua na formação vascular e na modulação de funções relacionadas à vascularização, sendo um importante marcador da angiogênese. A fim de se melhor compreender o comportamento vascular na formação e involução tímica, propôs-se avaliar a expressão gênica e proteica deste fator durante fases de desenvolvimento e involução do órgão, além da quantificação da vascularização do timo pela técnica estereológica, análise do parênquima tímico pela técnica de microscopia eletrônica de varredura e análise dos tipos celulares presentes em cada estágio etário. Para tal utilizou-se amostras de timo de gato em quatro estágios de desenvolvimento fetal (35, 45, 55, 65), e dois estágios pós-natal (6 meses e 1 ano) para a realização da imuno-histoquímica, PCR em tempo real e MEV,e para a técnica estereológica 2 estágios pós-natal (6 meses e 1 ano). Na microscopia eletrônica de varredura foram observados os timócitos de diferentes tamanhos, em estágios de maturação distintos. As proteinas do VEGF-A e dos receptores Fit-1 e KDR foram identificadas no timo de gatos em todas as fases do desenvolvimento foram localizadas no citoplasma de células epiteliais e no interior dos corpúsculos tímicos. A expressão do mRNA no período de 1 ano de idade a expressão do mRNA do VEGF e seus receptores tem um aumento significativo, coincidindo com a diminuição do Nvasc e do Nv(vasc) podendo causar um estado de hipóxia no órgão levando a um aumento compensatório de sistema VEGF. A curva de crescimento vascular obedece a um padrão de desenvolvimento e involuçãio do órgão. / The lymphoid system is composed by primary and secondary lymphoid organs. The thymus is a primary lymphoid organ responsible for maturation, differentiation and selection of the lymphoid T cell lineage that is responsible for cellular immunity. To accomplish these functions has a peculiar arrangement with morphologically distinct epithelial cells and vascular structures. The blood vessels have a role in tissue oxygentation and the migration of T cells into the thymic parenchyma, therefore they presents large vessels in cortico-medullary junction and a fine network branches to the cortex. This process has its molecular basis unknown as well as the involution process of the thymus. VEGF is an angiogenic factor that plays a role in the formation and modulation of vascular functions, being an important marker of angiogenesis. We proposed to evaluate the gene and protein of VEGF during the thymus development and involution, stereological quantification and scanning electronic microscopy. Samples of cat´s thymus from 35, 45, 55, 65 days of development and 6 months and 1 year of age. In scanning electronic microscopy different stages maturation thymocytes were observed. Protein expression of VEGF and its receptors were identified in all development stages in epithelial cells, endothelial cells and thymic corpuscles. The VEGF mRNA expression and its receptors in 1 year old animals was significantly increased, coinciding with the decreasing Nvasc and the Nv(vasc) causing a hypoxic condition in the thymus resulting in a compensatory increase of VEGF system. The vascular growth curve follows a pattern of development and involution of the organ.
56

Estudo histomorfológico e análise dos perfis celulares do rim cefálico, fígado, baço e timo do Piaractus mesopotamicus (Holmberg, 1887, Teleósteo, Characidae), pacu / Histomorphologic study and analysis of the cellular profiles of the head kidney, liver, spleen and thymus of Piaractus mesopotamicus (Holmberg, 1887, Teleostei, Characidae), pacu

Costa, Gerlane de Medeiros 11 December 2007 (has links)
O pacu, Piaractus mesopotamicus, é um teleósteo da Família Characidae, intensivamente cultivado no Brasil por causa de sua rusticidade, crescimento rápido e fácil adaptação, além de seu excelente sabor. Para uma melhor produção de peixes, informações sobre seu sistema imunológico incluindo a histologia dos órgãos linfóides se faz necessária. Sendo assim, o objetivo deste estudo foi descrever histomorfologicamente os órgãos linfóides: rim cefálico, fígado, baço e timo do Piaractus mesopotamicus, analisando os perfis celulares de cada órgão. Foram utilizados 30 animais juvenis, com idade que variaram entre 5 meses a um ano, com peso médio de 588.1 g e comprimento total médio de 27,51 cm. Os órgãos foram pós-fixados em solução de paraformaldeído 4% e Karnovsky, depois desidratados, diafanizados em xilol e incluídos em parafina. Os cortes foram obtidos com uma espessura de 4µm e corados em hematoxilina-eosina. Os esfregaços sanguíneos foram corados em Giemsa-May Grünwald para microscopia de luz. Para microscopia eletrônica de transmissão as amostras fixadas em Karnovsky foram lavadas em sacarose e pósfixadas em tetróxido de ósmio 1%, desidratadas e emblocadas em resina Spurr. O resultado da análise macroscópica mostra que a distribuição do rim, rim cefálico, timo, fígado e baço são as mesmas encontradas na maioria dos teleósteos. Quanto à forma desses órgãos, o fígado apresentou uma variação anatômica na forma e números de lobos, sendo constituído por três lobos. O rim apresentou uma forma em \"H\", onde a região central deste se expandia sobre a bexiga natatória. O rim cefálico, em animais com idade mais avançada, se apresentou como uma dilatação na região cranial do rim, se mostrando bem visível. O timo e o baço apresentaram localização e forma similares aos de outros teleósteos. A microscopia mostrou similaridades entre os órgãos do Piaractus mesopotamicus e outros teleósteos. Na microscopia eletrônica de transmissão foram observadas similaridades ultraestruturais das células encontradas no rim cefálico, fígado, timo e baço e as já descritas em peixes teleósteos. Hemácias, trombócitos, linfócitos, eosinófilos e células granulocíticas especiais encontrados no sangue periférico, tanto de animais jovens quanto dos animais com idade mais avançada, foram os mesmos tipos celulares descritos na literatura de teleósteos. Observando nossos resultados concluímos que histologicamente os órgão linfóides de Piaractus mesopotamicus são similares aos de outros teleósteos e comparando os resultados de microscopia de transmissão concluímos que as estruturas encontradas nas nossas análises são as mesmas das descritas em outras espécies. Os resultados das nossas observações macroscópicas mostraram que o pacu é uma espécie que apresenta algumas características morfológicas singulares e que podem estar ligadas ao tipo de alimentação e a adaptações evolutivas. Esses achados demonstram que a anatomia dos órgãos de peixes e suas variações precisam ser analisados e correlacionados com suas funções e forma de vida de cada espécie. / Piaractus mesopotamicus (Pacu) is a fish from the Characidae Family, it is intensively culture in Brazil because of its rusticity, easy raising and adaptation, besides its excellent flavour. In order to produce a healthy fish, information on its immunological system, including the histology of the lymphoid organs is needed. Therefore, the objective of this study is to describe histomorphologicaly the lymphoid organs: head kidney, liver, spleen and thymus of the Piaractus mesopotamicus, analyzing the cellular profiles of each organ. Thirty young animals, with age varying between 5 months to a year, with average weight and total length of 588.1 g and a 27.51 cm, respectively, were used. The organs were fixed in 4% paraformaldehyde solution, and Karnovsky, afterwards dehydrated, diafanized in xilol and included in paraffin. Four µm sections were obtained and stained with hematoxilin-eosin. Blood smears were stained with Giemsa-May Grünwald for light microscopy. Samples for transmission electric microscopy were fixed in Karnovsky, washed in sacarose and post-fixed with osmium tetroxide 1%, dehydrated and embedded in resin Spurr. The macroscopic analysis show that the localization of the kidney, head kidney, thymus, liver and spleen are very similar to most of the teleosts. Some particularities were observed in the liver, which presented an anatomical variation in the shape and number of lobes, being constituted by three lobes. The kidney presented existe \"H\" shape, where the central region overlaps the swimming bladder. The head-kidney, in adult animals, presented an evident dilation in the cranial region of the kidney. The thymus and spleen presented a similar location and shape to that of the teleosts. The light microscopy studies showed similarities between the organs of the Piaractus mesopotamicus and other teleost fishes. The transmission electron microscopy studies showed ultrastructural similarities, of the cells from the head kidney, liver, thymus and spleen with the literature. Eritrocytes, trombocytes, lymphocytes, eosinophils and special granulocytic cells were found in peripheral blood of both juvenile and adult animals and were similar to the cellular profiles described in the literature to the other teleost fishes. Our studies were successful in describing the macro, micro and ultrastructure of Piaractus mesopotamicus organs and may be used as reference for further research aiming the improvement of fish health status in aquaculture.
57

Étude de la migration thymique : vers une reconstitution optimale du compartiment T / Study of thymic migration : towards optimal reconstitution of the T

Michaels Lopez, Victoria 23 October 2017 (has links)
Notre équipe s’intéresse à la différenciation des cellules souches hématopoïétiques (CSH) vers la lignée des lymphocytes T. Contrairement aux autres lignées sanguines, qui se développent dans la MO, les progéniteurs des lymphocytes T doivent terminer leur différenciation dans le thymus. Ma thèse a un double objectif: 1) caractériser les progéniteurs candidats à la reconstitution T pour établir leur contribution à celle-ci et 2) identifier les stades initiaux de la reconstitution T. Nous avons mis en évidence que seul le progéniteur multipotent au stade 3 (MPP3 : Lin- Sca1+ c-Kit+ VCAM1- Flt3+) et le progéniteur commun lymphoïde (CLP : Lin- Sca1lo c-Kitlo IL7Ra+ Flt3-) circulent dans le sang. De plus, nos résultats montrent que les gènes impliqués dans l’engagement T et dans la migration thymique sont uniquement exprimées par la population MPP3 circulante. Cette population est la plus compétente pour générer des précurseurs T (pré-T). Au contraire, les CLPs sont plus efficaces pour la production de différents types de cellules B de la rate. Par la suite, mon projet a consisté à déterminer la proportion de progéniteurs contribuant à la reconstitution T. En effet, le thymus peut être colonisé par différents progéniteurs (LMPP, Lymphoid-primed Multipotent Progenitors, et CLP), mais leur contribution dans la différenciation T reste inconnue et est sujet à controverse. Nous avons utilisé une stratégie innovante pour suivre les progéniteurs avec une séquence d’ADN ou Code Barre (CB) intégrée dans le génome par un vecteur viral. Les résultats préliminaires indiquent qu'une forte fréquence de CBs en provenance de la population LMPP est retrouvée dans le compartiment T thymique. Dans la dernière partie, nous nous sommes intéressés à élucider le premier stade de différenciation T dans le thymus et l’identité cellulaire et moléculaire des premiers migrants thymiques pour comprendre le délai de génération de ce compartiment. La population thymique la plus immature (TN1 : Lin- CD44+ CD25+) présente différentes sous-population selon l’expression de c-Kit et de CD24 chacune de ces différentes populations TN1 pourrait participer à cette reconstitution T. Leur analyse moléculaire montre deux lignées cellulaire selon l’expression de Pu1, dans les TN1 c-Kit+, et de Cd3e, dans la sous-population TN1e (CD24- c-Kit-). En parallèle, pour éclaircir le processus d’engagement des cellules T, ces sous-populations de TN1 ont été étudiées dans différentes conditions de reconstitution : une reconstitution endogène suite à une irradiation sub-létale et une exogène après greffe de MO. Nos résultats permettent de préciser les caractéristiques, propres aux progéniteurs thymiques au stade TN1, qui leur confèrent des compétences à se différencier et à proliférer plus efficacement. Après irradiation ou greffe de MO, le compartiment TN1 est constitué de cellules à faible capacité proliférative. Le thymus en état de reconstitution génère tout d’abord des cellules présentatrice d’antigène (APC) puis les cellules T. Ces deux points suggèrent que les cellules à faible capacité proliférative seront plus aptes à générer des cellules APC plutôt que des cellules T. Il reste à déterminer quel environnement thymique permet le maintien des cellules à faible capacité proliférative, notamment, par rapport à l’expression de Delta-4, de l’IL7 et du ligand c-Kit. Cela va permettre l'identification de facteurs favorisant leur induction et leur expansion. Il nous semble aussi intéressant d’étudier la contribution de la population à faible capacité proliférative, TN1 CD24- c-Kit-, dans la différenciation T. / Within the hematopoietic system, hematopoietic stem cells (HSCs) are the only cells with the functional capacity to give rise to all blood lineages and to self-renew for life. These properties and the ability of HSCs to engraft conditioned recipients permitted to apply these cells in regenerative medicine. Like all blood lineages, T cells develop from bone marrow HSC. However, T lineage development requires many weeks, three separate anatomical sites (bone marrow, blood and thymus), many environments and the loss of multiple alternative lineage potentials. Many questions remain to be clarified during this process: do all progenitors have an intrinsic feature of T cell development ? How does this intrinsic potential express ? How the bloodstream contributes to the T cell development ? Which BM progenitor contributes to T cell reconstitution ? What are the characteristics of T cell reconstitution ? We have shown that only the multipotent progenitor in stage 3 (MPP3: Lin- Sca1+ c-Kit+ VCAM1- Flt3+) and a subset of the common lymphoid progenitor (CLP Flt3-: Lin- Sca1lo c-Kitlo IL7Ra+ Flt3-) circulate in the blood. Moreover, our results show that T cell engagement and thymic migration genes are modulated in the circulation, especially up-regulated in the MPP3 circulating subset. This population present a T cell intrinsic potential and is the most competent to generate precursors T (pre-T). On the contrary, CLPs subsets are more efficient for the production of different B cells. Lymphoid primed multipotent progenitor (LMPP, MPP Flt3+) and CLP subsets' respective contributions to the T cell pathway are still being hotly debated. Multiple progenitors in BM have been shown to possess T lineage potential when placed in the thymus. However, it is unlikely that all of them contribute physiologically to thymopoiesis. It was claimed that CLPs are the earliest lymphoid committed progenitor from which B and T lineage cells arise. However, the concept that the CLP is the progenitor population through which all T lymphocytes are derived has been challenged. More specifically, which BM progenitor contribute to the T cell reconstitution ? In order to answer this question, we used an innovative strategy to follow the progenitors with a DNA sequence or Barcode (BC) integrated into the genome by a viral vector. Preliminary results indicate that a high frequency of BCs from the LMPP population is found in the T cell lineage. Finally, we characterized the first stage of T cell differentiation in the thymus by a cellular and molecular asses. We show that the most immature thymic population (TN1: Lin- CD44+ CD25+), at the molecular level, contain two separate lineages, detected by Pu1 (TN1a and b) or CD3e (TN1e) gene expression. In order to clarify the process of T-cell involvement, these TN1 subsets have been studied under different reconstitution conditions: endogenous reconstruction following sub-lethal irradiation and exogenous after bone marrow (BM) graft. In these conditions, the TN1 compartment presents cells with low proliferative capacity and that antigen presenting cells (APC) are the first mature population and thus T cells are generated in second place. These two points suggest that cells with low proliferative capacity will be more apt to generate APC cells rather than T cells. It remains to be determined which thymic environment permits the maintenance of cells with a low proliferative capacity, in particular, with respect to the expression of Delta-4, IL7 and the c-Kit ligand. This will allow the identification of factors favoring their induction and their expansion. It also seems interesting to study the contribution of the population with low proliferative capacity, TN1 CD24- c-Kit-, in the T cell differentiation.
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Caracterização de L-Asparaginase de Erwinia chrysanthemi melhorada por evolução sintética de proteí­nas e otimização das condições de produção / Characterization of Erwinia chrysanthemi L-Asparaginase improved by synthetic protein evolution and optimization of production conditions

Custodio, Débora Fernandes 07 May 2018 (has links)
A L-Asparaginase (L-ASNase) é uma enzima tetramérica bacteriana, utilizada em sessões de quimioterapia. Essa enzima depleta os aminoácidos asparagina (Asn) e glutamina (Gln), transformando-os em aspartato (Asp) ou glutamato (Glu), respectivamente, e em amônia. Contudo, a L-ASNase pode induzir resposta imune, levando à produção de anticorpos antiasparaginase, uma causa importante de resistência ao medicamento. Uma L-ASNase ideal seria aquela com alta atividade e estabilidade e baixo potencial imunogênico, porém, as L-ASNases utilizadas na terapêutica não reúnem essas características simultaneamente. Por essa razão, o presente trabalho utilizou técnicas de mutagênese randômica, a fim de criar uma nova proteoforma de L-ASNase de E. chrysanthemi com uma melhor atividade e estabilidade. Além disso, foram estudadas condições de cultivo em agitador metabólico, visando à otimização de condições de produção. Foi criada uma biblioteca com 1.056 clones, e desses, 19 foram selecionados por apresentarem atividade superior ou igual à enzima selvagem quando dosada em extrato bruto. Dentre eles, dois mutantes se destacaram por apresentarem a atividade específica glutaminásica diferente da enzima selvagem. Análises in silico indicam que o mutante 9-6D apresentou diminuição de desordem estrutural e epítopos imunogênicos. O mutante 9-5F demonstrou uma diminuição da porcentagem da atividade glutaminásica quando comparada a enzima selvagem. O estudo de produção do mutante 9-5F indicou que a temperatura de indução, seguida da concentração do indutor, são os parâmetros mais relevantes para a otimização da produção de L-ASNase de E. chrysanthemi mutante. / L-Asparaginase (L-ASNase) is a bacterial tetrameric enzyme used in chemotherapy sessions that deplete asparagine (Asn) and glutamine (Gln), transforming them into Aspartate (Asp) or glutamate (Glu), respectively, and ammonia. However, L-ASNase can induce immune response leading to the production of anti-asparaginase antibody, an important cause of drug resistance. Ideally, L-ASNase would be one with high activity, high stability and low immunogenic potential, but the L-ASNases commercially available today do not present these characteristics simultaneously. For this reason, this study used techniques of random and site-directed mutagenesis in order to create a new proteoform of E. chrysanthemi L-ASNase with improved activity and stability. In addition, culture conditions were studied in a metabolic shaker, aiming at the optimization of production conditions. A library with 1,056 clones was created, and of these clones, 19 were selected because they had activity superior or equal to the wild-type enzyme in crude protein extract. Among them, 2 mutants stood out for having different glutaminase specific activity in relation to wild-type enzyme. The 9-6D mutant also showed decreased structural disorder and immunogenic epitopes. The 9-5F mutant demonstrated a decrease in percentage of glutaminase activity when compared to the wild-type enzyme. The production study of 9-5F mutant indicated that the induction temperature followed by the inductor concentration are the most relevant parameters for the production optimization of E. chrysanthemi mutant L-ASNase.
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Elucidation of molecular mechanism of TSP-1 induced cell growth inhibition in childhood acute lymphoblastic leukemia. / Elucidation of molecular mechanism of thrombospondin-1 induced cell growth inhibition in childhood acute lymphoblastic leukemia

January 2010 (has links)
Ng, Ka Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 118-131). / Abstracts in English and Chinese. / Thesis Abstract --- p.i / 論文摘要 --- p.vi / Acknowledgements --- p.x / Abbreviations --- p.xii / Thesis Content --- p.xv / List of Figures --- p.xix / List of Tables --- p.xxi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Haematopoiesis --- p.1 / Chapter 1.2 --- Leukemia --- p.2 / Chapter 1.3 --- Childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) --- p.3 / Chapter 1.3.1 --- Epidemiology --- p.4 / Chapter 1.3.2 --- Causes and risk factors --- p.4 / Chapter 1.3.3 --- Clinical features --- p.6 / Chapter 1.3.4 --- Morphology --- p.6 / Chapter 1.4 --- Classification of BCP-ALL --- p.7 / Chapter 1.4.1 --- Immunophenotyping --- p.7 / Chapter 1.4.2 --- Cytogenetics and molecular genetics --- p.9 / Chapter 1.5 --- Prognostic factors --- p.13 / Chapter 1.6 --- Current treatments of BCP-ALL --- p.15 / Chapter Chapter 2 --- Literature Review --- p.18 / Chapter 2.1 --- Cytogenetics abnormalities in BCP-ALL --- p.18 / Chapter 2.1.1 --- Chromosomal translocation --- p.18 / Chapter 2.1.2 --- Aneuploidy --- p.21 / Chapter 2.2 --- Epigenetic aberrations --- p.21 / Chapter 2.2.1 --- DNA methylation --- p.22 / Chapter 2.2.2 --- Mechanism of DNA Methylation in Transcription Repression --- p.23 / Chapter 2.3 --- DNA Methylation in Normal Haematopoiesis --- p.25 / Chapter 2.4 --- DNA Methylation in Haematological Malignancies --- p.26 / Chapter 2.4.1 --- DNA methylation in ALL --- p.26 / Chapter 2.4.2 --- DNA methylation in BCP-ALL --- p.29 / Chapter 2.5 --- Angiogenesis in pathogenesis of acute leukemias --- p.30 / Chapter 2.6 --- Thrombospondin-1 (TSP-1) --- p.32 / Chapter 2.6.1 --- Structure of TSP-1 --- p.33 / Chapter 2.6.2 --- The role of TSP-1 in tumorigenesis --- p.34 / Chapter 2.6.3 --- TSP-1 mediates the activation of TGFβ --- p.36 / Chapter 2.6.4 --- TSP-1 mediates TGFβ-induced Apoptosis --- p.37 / Chapter 2.6.5 --- Association of TGFβ with normal haematopoiesis and haematological malignancies progression --- p.40 / Chapter 2.6.6 --- TSP-1 Induced Apoptosis via its Receptor CD36 --- p.42 / Chapter 2.6.7 --- THBS1 promoter hypermethylation and its association with tumorigenesis --- p.43 / Chapter 2.6.8 --- Effect of THBS1 aberrant methylation on TGFp --- p.45 / Chapter Chapter 3 --- Rationale of Study --- p.47 / Chapter Chapter 4 --- Materials and Methods --- p.52 / Chapter 4.1 --- Patient sample --- p.52 / Chapter 4.2 --- Cell lines --- p.52 / Chapter 4.3 --- Mononuclear cells isolation --- p.53 / Chapter 4.4 --- THBS1 promoter hypermethylation analysis --- p.54 / Chapter 4.4.1 --- DNA extraction from mononuclear cells and cell lines --- p.54 / Chapter 4.4.2 --- Bisulfite conversion --- p.55 / Chapter 4.4.3 --- Methylation specific PCR (MSP) --- p.55 / Chapter 4.5 --- Quantification of THBS1 mRNA expression --- p.57 / Chapter 4.5.1 --- RNA extraction --- p.57 / Chapter 4.5.2 --- Reverse transcription PCR --- p.58 / Chapter 4.5.3 --- Real-time RT-PCR --- p.58 / Chapter 4.6 --- Determination of plasma TSP-1 level --- p.59 / Chapter 4.7 --- TSP-1 treatment --- p.60 / Chapter 4.8 --- Flow cytometry analysis --- p.60 / Chapter 4.8.1 --- Annexin-V analysis --- p.60 / Chapter 4.8.2 --- Cell fixation --- p.61 / Chapter 4.8.3 --- Analysis of Caspase-3 activation --- p.62 / Chapter 4.8.4 --- "Analysis of TGFβ downstream pathway activation: Phosphorylation of Smad2/3, JNK and p38" --- p.62 / Chapter 4.9 --- Determination ofTGF-β expression --- p.63 / Chapter 4.10 --- Statistical analysis methods --- p.64 / Chapter Chapter 5 --- Results / Chapter 5.1 --- THBS1 methylation statuses in BCP-ALL patients and cell lines --- p.66 / Chapter 5.2 --- Correlation of THBS1 methylation statuses and clinico- pathological features in BCP-ALL patients --- p.68 / Chapter 5.3 --- Association of THBS1 methylation and THBS1 mRNA expression --- p.69 / Chapter 5.4 --- Effect of TSP-1 treatment on apoptosis level of BCP-ALL cells --- p.72 / Chapter 5.4.1 --- Annexin-V assay --- p.72 / Chapter 5.4.2 --- Caspase-3 activation assay --- p.75 / Chapter 5.5 --- THBS1 methylation and activation of secreted TGFβ --- p.78 / Chapter 5.6 --- Effect of TSP-1 treatment on activation of TGFβ --- p.80 / Chapter 5.7 --- The involvement ofTGFβ activation in TSP-1 induced apoptosis in BCP-ALL --- p.82 / Chapter 5.8 --- The association of TGFβ signaling pathway activities with THBS1 methylation --- p.86 / Chapter Chapter 6 --- Discussion --- p.91 / Chapter 6.1 --- THBS-1 promoter hypermethylation in BCP-ALL cell lines and patients: Correlation with expression and clinico-pathological profile --- p.93 / Chapter 6.1.1 --- THBS1 promoter hypermethylation status in childhood BCP-ALL --- p.93 / Chapter 6.1.2 --- THBS1 methylation as prognostic markers --- p.94 / Chapter 6.1.3 --- "Association of THBS1 methylation status, mRNA expression and TSP-1 protein expression in childhood BCP-ALL" --- p.96 / Chapter 6.2 --- Study of the correlation of TSP-1 induced apoptosis with the THBS1 promoter methylation status --- p.99 / Chapter 6.3 --- Elucidation of the molecular mechanisms of TSP-1 induced apoptosis: study of the involvement of TGFβ activation --- p.103 / Chapter 6.3.1 --- Latent TGFβ activation by TSP-1 in BCP-ALL and association with THBS1 methylation status --- p.103 / Chapter 6.3.2 --- TSP-1 induced cell death through activation ofTGFβ --- p.105 / Chapter 6.3.3 --- TSP-1 induced apoptotic signals via TGFβ signaling pathway --- p.107 / Chapter 6.4 --- Limitation of study --- p.113 / Chapter 6.5 --- Future studies --- p.114 / Chapter 6.5.1 --- Continuation study in TSP-1 induced TGFβ-mediated pathways --- p.114 / Chapter 6.5.2 --- Microarray analysis --- p.115 / Chapter 6.6 --- TSP-1 in treatment of childhood BCP-ALL --- p.115 / Chapter Chapter 7 --- Conclusion --- p.117 / Reference --- p.118
60

Molecular control of dendritic cell development and function

Lau, Colleen January 2015 (has links)
Dendritic cells (DCs) comprise a distinct lineage of potent antigen-presenting mononuclear phagocytes that serve as both mediators of innate immune responses and key facilitators of the adaptive immune response. DCs play both immunogenic and tolerogenic roles through their dual ability to elicit pathogen-specific T cell immunity as well as induce regulatory T cell (Treg) responses to promote tolerance in the steady state. The aim of the work presented here is to examine the normal regulatory mechanisms of DC development and function, starting with the dissection of mechanisms behind an aberrantly activated developmental pathway, followed by the exploration of new mechanisms governed by two candidate transcription factors. The first chapter of the thesis focuses on the growth factor receptor Flt3, an essential regulator of normal DC development in both mice and humans, and concurrently one of the most commonly mutated proteins found in acute myeloid leukemia (AML). We investigated the effect of its most common activating mutation in AML, the Flt3 internal tandem duplication (Flt3-ITD), and found that this mutation caused a significant cell-intrinsic expansion of all DC populations. This effect was associated with an expansion of Tregs and the ability to dampen self-reactivity, with an inability to control autoimmunity in the absence of Tregs. Thus, we describe a potential mechanism by which leukemia can modulate T cell responses and support Treg expansion indirectly through DCs, which may compromise immunosurveillance and promote leukemogenesis. The subsequent chapters explore the basic molecular mechanisms of DC development by using Flt3 expression as a guide to uncover new candidates involved in the DC transcriptional program. We show that Myc family transcription factor, Mycl1, is largely dispensable for DC development and function, contrary to recent published findings that propose a role in proliferation and T cell priming. On the other hand, we find that conditional deletion of our second candidate gene, an Ets family transcription factor, has diverse effects on DC development, monocyte homeostasis, and cytokine production. Overall, our studies highlight an unexpected molecular link between DC development and leukemogenesis, and elucidate novel mechanisms controlling DC differentiation and function.

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