83 resultados para Oligodendrocyte


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灵长类胚胎干细胞(ES 细胞)不仅能为研究生殖发育生物学基础理论提供良好的 模型,而且可为细胞替代治疗提供大量的供体细胞,因此具有重要的研究价值。当前 灵长类ES 细胞研究还有很多问题需要解决,如分离建立更多的胚胎干细胞系,优化培 养体系,提高ES 细胞定向分化为特定细胞的比例,研究ES 细胞自我更新和分化的机 制等。本文一方面概括了灵长类ES 细胞的研究进展,另一方面并对制备抗体,免疫外 科手术法分离灵长类胚胎内细胞团,建立猕猴ES 细胞的无饲养层、无血清培养体系和 诱导猕猴ES 细胞分化成高纯度的O2A 神经胶质前体细胞进行了研究。主要结论如下: 1)分别以猕猴脾脏淋巴细胞和人外周血单个核细胞作为免疫原,免疫日本大耳白兔, 得到免疫血清。在补体介导的细胞毒作用下,兔抗人和兔抗猕猴免疫血清可以裂解人 和猕猴囊胚滋养层细胞,从而分离出内细胞团,用于分离培养人和猕猴胚胎干细胞。2) 猕猴ES 细胞在以层粘连蛋白(laminin)为胞外基质,含转化生长因子beta1(TGFβ1) 的无血清培养基(SFM)中可以稳定的增殖至少22 代,保持不分化,并具有分化成三 个胚层细胞的能力。进一步的研究发现去除TGFβ1 后,猕猴ES 细胞出现分化,整合 素表达降低,推测TGFβ1 可能通过促进猕猴ES 细胞整合素的表达,加强其与胞外基 质的相互作用,从而维持ES 细胞的自我更新。然而猕猴ES 细胞不能在纤粘连蛋白 (fibronectin)和明胶上生长。3)无饲养层、无血清培养体系中长期培养的猕猴ES 细 胞,分化出拟胚体,14 天的拟胚体在血清中分化培养一周后,在含碱性成纤维生长因 子bFGF、表皮生长因子EGF 和胰岛素+转铁蛋白+亚硒酸钠ITS 的培养基中培养, 获得97%的O2A 胶质前体细胞,得到的O2A 细胞能够稳定增殖,并且可以自发分化 为II 型星型胶质细胞和少突胶质细胞。本实验的结果有助于猕猴ES 细胞分离建系和培 养系统的优化、推动猕猴ES 细胞自我更新和诱导为神经胶质细胞机制的研究,便于建 立ES 细胞替代治疗的猕猴模型,从而为人类ES 细胞的临床疾病治疗提供参考。

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The efficiency of central nervous system remyelination declines with age. This is in part due to an age-associated decline in the phagocytic removal of myelin debris, which contains inhibitors of oligodendrocyte progenitor cell differentiation. In this study, we show that expression of genes involved in the retinoid X receptor pathway are decreased with ageing in both myelin-phagocytosing human monocytes and mouse macrophages using a combination of in vivo and in vitro approaches. Disruption of retinoid X receptor function in young macrophages, using the antagonist HX531, mimics ageing by reducing myelin debris uptake. Macrophage-specific RXRα (Rxra) knockout mice revealed that loss of function in young mice caused delayed myelin debris uptake and slowed remyelination after experimentally-induced demyelination. Alternatively, retinoid X receptor agonists partially restored myelin debris phagocytosis in aged macrophages. The agonist bexarotene, when used in concentrations achievable in human subjects, caused a reversion of the gene expression profile in multiple sclerosis patient monocytes to a more youthful profile and enhanced myelin debris phagocytosis by patient cells. These results reveal the retinoid X receptor pathway as a positive regulator of myelin debris clearance and a key player in the age-related decline in remyelination that may be targeted by available or newly-developed therapeutics.

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Ionizing radiation causes degeneration of myelin, the insulating sheaths of neuronal axons, leading to neurological impairment. As radiation research on the central nervous system has predominantly focused on neurons, with few studies addressing the role of glial cells, we have focused our present research on identifying the latent effects of single/ fractionated -low dose of low/ high energy radiation on the role of base excision repair protein Apurinic Endonuclease-1, in the rat spinal cords oligodendrocyte progenitor cells’ differentiation. Apurinic endonuclease-1 is predominantly upregulated in response to oxidative stress by low- energy radiation, and previous studies show significant induction of Apurinic Endonuclease-1 in neurons and astrocytes. Our studies show for the first time, that fractionation of protons cause latent damage to spinal cord architecture while fractionation of HZE (28Si) induce increase in APE1 with single dose, which then decreased with fractionation. The oligodendrocyte progenitor cells differentiation was skewed with increase in immature oligodendrocytes and astrocytes, which likely cause the observed decrease in white matter, increased neuro-inflammation, together leading to the observed significant cognitive defects.

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Tese de mestrado, Neurociências, Faculdade de Medicina, Universidade de Lisboa, 2015

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In previous work we found that mezerein, a C kinase activator, as well as basic fibroblast growth factor (FGF-2) induce demyelination and partial oligodendrocyte dedifferentiation in highly differentiated aggregating brain cell cultures. Here we show that following protein kinase C activator-induced demyelination, effective remyelination occurs. We found that mezerein or FGF-2 caused a transient increase in DNA synthesis following a pronounced decrease of the myelin markers myelin basic protein and 2',3'-cyclic nucleotide 3'-phosphohydrolase. Both oligodendrocytes and astrocytes were involved in this mitogenic response. Within 17 days after demyelination, myelin was restored to the level of the untreated controls. Transient mitotic activity was indispensable for remyelination. The present results suggest that myelinating oligodendrocytes retain the capacity to reenter the cell cycle, and that this plasticity is important for the regeneration of the oligodendrocyte lineage and remyelination. Although it cannot be excluded that a quiescent population of oligodendrocyte precursor cells was present in the aggregates and able to proliferate, differentiate and remyelinate, we could not find evidence supporting this view.

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In the present study, we evaluated stimulation of the angiotensin type 2 receptor (AT2R) by the selective non-peptide agonist Compound 21 (C21) as a novel therapeutic concept for the treatment of multiple sclerosis using the model of experimental autoimmune encephalomyelitis (EAE) in mice. C57BL-6 mice were immunized with myelin-oligodendrocyte peptide and treated for 4 weeks with C21 (0.3 mg/kg/day i.p.). Potential effects on myelination, microglia and T-cell composition were estimated by immunostaining and FACS analyses of lumbar spinal cords. The in vivo study was complemented by experiments in aggregating brain cell cultures and microglia in vitro. In the EAE model, treatment with C21 ameliorated microglia activation and decreased the number of total T-cells and CD4+ T-cells in the spinal cord. Fluorescent myelin staining of spinal cords further revealed a significant reduction in EAE-induced demyelinated areas in lumbar spinal cord tissue after AT2R stimulation. C21-treated mice had a significantly better neurological score than vehicle-treated controls. In aggregating brain cell cultures challenged with lipopolysaccharide (LPS) plus interferon-γ (IFNγ), AT2R stimulation prevented demyelination, accelerated re-myelination and reduced the number of microglia. Cytokine synthesis and nitric oxide production by microglia in vitro were significantly reduced after C21 treatment. These results suggest that AT2R stimulation protects the myelin sheaths in autoimmune central nervous system inflammation by inhibiting the T-cell response and microglia activation. Our findings identify the AT2R as a potential new pharmacological target for demyelinating diseases such as multiple sclerosis.

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L’administration systémique d’atorvastatine s’est montrée neuroprotective suivant un traumatisme médullaire, en diminuant la réponse inflammatoire au site de la lésion ainsi qu’en réduisant l’apoptose des oligodendrocytes. Ce dernier épargne la matière blanche au site de l’insulte et améliore la locomotion. Le but de cette étude était de confirmer l’efficacité neuroprotective de l’atorvastatine ainsi que son action précoce, lorsqu’administré post-trauma, sur la limitation de l’apoptose. Des rats Sprague-Dawley femelles ont reçu une injection intrapéritonéale de : (1) statine/saline (5 mg/kg) 2 h après une lésion contusive; (2) saline physiologique 2 h post-contusion; ou (3) saline physiologique sans lésion. Les rats traités à la statine ont montré une amélioration significative (p<0.05) de leur locomotion après 4 semaines post-trauma, comparée au groupe « véhicule » lésé. Expliquant cette observation, l’activité de la caspase-3 fut diminuée de 50% (p<0.05) et la méthode de TUNEL révéla une diminution d’approximativement 20% du nombre de cellules apoptotiques au site lésionnel (p<0.01) 4 h après l’insulte contusive chez le groupe traité en comparaison aux groupes « véhicules ». Ces résultats démontrent que l’atorvastatine est efficace dans la prévention de l’apoptose précoce au site lésionnel dans un modèle expérimental de traumatisme médullaire après seulement 2 h post-traumatisme.

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La sclérose en plaques (SEP) est une maladie inflammatoire démyélinisante et neurodégénérative du système nerveux central (SNC). Les cellules T activées qui expriment le PD-1 sont inhibées via l’interaction avec l’un des ligands: PD-L1 ou PD-L2. Des études effectuées chez le modèle murin de la SEP, l’encéphalomyélite auto-immune expérimentale (EAE), ont démontré que l’interaction du PD-1 avec ses ligands contribue à atténuer la maladie. Toutefois, le rôle du PD-1 et de ses ligands dans la pathogenèse de la SEP chez l’humain et dans le modèle murin n’a pas été complètement élucidé. Nous avons déterminé que plusieurs cellules du SNC humain peuvent exprimer les ligands du PD-1. Les astrocytes, les microglies, les oligodendrocytes et les neurones expriment faiblement le PD-L1 dans des conditions basales mais augmentent de façon significative cette expression en réponse à des cytokines inflammatoires. Le blocage de l’expression du PD-L1 par les astrocytes à l’aide de siRNA spécifiques mène à l’augmentation significative des réponses des cellules T CD8+ (prolifération, cytokines, enzymes lytiques). Nos résultats établissent ainsi que les cellules gliales humaines peuvent exprimer des niveaux suffisants de PD-L1 en milieu inflammatoire pour inhiber les réponses des cellules T CD8+. Notre analyse de tissus cérébraux post-mortem par immunohistochimie démontre que dans les lésions de la SEP les niveaux de PD-L1 sont significativement plus élevés que dans les tissus de témoins; les astrocytes et les microglies/macrophages expriment le PD-L1. Cependant, plus de la moitié des lymphocytes T CD8+ ayant infiltré des lésions de SEP n’expriment pas le récepteur PD-1. Au cours du développement de l’EAE, les cellules du SNC augmentent leur niveau de PD-L1. Le PD-1 est fortement exprimé par les cellules T dès le début des symptômes, mais son intensité diminue au cours de la maladie, rendant les cellules T insensibles au signal inhibiteur envoyé par le PD-L1. Nous avons observé que les cellules endothéliales humaines formant la barrière hémato-encéphalique (BHE) expriment de façon constitutive le PD-L2 mais pas le PD-L1 et que l’expression des deux ligands augmente dans des conditions inflammatoires. Les ligands PD-L1 et PD-L2 exprimés par les cellules endothéliales ont la capacité de freiner l’activation des cellules T CD8+ et CD4+, ainsi que leur migration à travers la BHE. L’endothélium du cerveau des tissus normaux et des lésions SEP n’exprime pas des taux détectables de PD-L1. En revanche, tous les vaisseaux sanguins des tissus de cerveaux normaux sont positifs pour le PD-L2, alors que seulement la moitié de ceux-ci expriment le PD-L2 dans des lésions SEP. Nos travaux démontrent que l’entrée des cellules T activées est contrôlée dans des conditions physiologiques grâce à la présence du PD-L2 sur la BHE. Cependant, l’expression plus faible du PD-L2 sur une partie des vaisseaux sanguins dans les lésions SEP nuit au contrôle de la migration des cellules immunes. De plus, une fois dans le SNC, les cellules T CD8+ étant dépourvues du PD-1 ne peuvent recevoir le signal inhibiteur fourni par le PD-L1 fortement exprimé par les cellules du SNC, leur permettant ainsi de rester activées.

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NG2-glia are an abundant population of glial cells that have been considered by many to be oligodendrocyte progenitor cells (OPCs). However, growing evidence suggests that NG2-glia may also be capable of differentiating into astrocytes and neurons under certain conditions. Here, we have examined NG2-glia in cerebellar slices, using transgenic mice in which the astroglial marker glial specific protein (GFAP) drives expression of the reporter gene enhanced green fluorescent protein (EGFP). Immunolabelling for NG2 shows that NG2-glia and GFAP-EGFP astroglia are separate populations in most areas of the brain, although a substantial population of NG2-glia in the pons also express the GFAP-EGFP reporter. In the cerebellum, NG2-glia did not express EGFP, either at postnatal day (P)12 or P29-30. We developed an organotypic culture of P12 cerebellar slices that maintain cytoarchitectural integrity of Purkinje neurons and Bergmann glia. In these cultures, BrdU labelling indicates that the majority of NG2-glia enter the cell cycle within 2 days in vitro (DIV), suggesting that NG2-glia undergo a [`]reactive' response in cerebellar cultures. After 2 DIV NG2-glia began to express the astroglial reporter EGFP and in some cases the respective GFAP protein. However, NG2-glia did not acquire phenotypic markers of neural stem cells or neurons. The results suggest that NG2-glia are not lineage restricted OPCs and are a potential source of astrocytes in the cerebellum.

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Transforming growth factor beta (TGF-beta) plays a role both in the induction of Treg and in the differentiation of the IL-17-secreting T cells (Th17) which drive inflammation in experimental autoimmune encephalomyelitis (EAE). We investigated the role that thrombospondin-1 (TSP-1) dependent activation of TGF-beta played in the generation of an encephalitic Th17 response in EAE. Upon immunization with myelin oligodendrocyte glycoprotein peptide (MOG(35-55)), TSP-1 deficient (TSP-1(null)) mice and MOG(35-55) TCR transgenic mice that lack of TSP-1 (2D2.TSP-1(null)) exhibited an attenuated form of EAE, and secreted lower levels of IL-17. Adoptive transfer of in vitro-activated 2D2.TSP-1(null) T cells induced a milder form of EAE, independent of TSP-1 expression in the recipient mice. Furthermore, in vitro studies demonstrated that anti-CD3/anti-CD28 pre-activated CD4+ T cells transiently upregulated latent TGF-beta in a TSP-1 dependent way, and such activation of latent TGF-beta was required for the differentiation of Th17 cells. These results demonstrate that TSP-1 participates in the differentiation of Th17 cells through its ability to activate latent TGF-beta, and enhances the inflammatory response in EAE. (C) 2009 Elsevier Ltd. All rights reserved.

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In multiple sclerosis, the immune system attacks the white matter of the brain and spinal cord, leading to disability and/or paralysis. Myelin, oligodendrocytes and neurons are lost due to the release by immune cells of cytotoxic cytokines, autoantibodies and toxic amounts of the excitatory neurotransmitter glutamate. Experimental autoimmune encephalomyelitis (EAE) is an animal model that exhibits the clinical and pathological features of multiple sclerosis. Current therapies that suppress either the inflammation or glutamate excitotoxicity are partially effective when administered at an early stage of EAE, but cannot block advanced disease. In a multi-faceted approach to combat EAE, we blocked inflammation with an anti-MAdCAM-1 (mucosal addressin cell adhesion molecule-1) monoclonal antibody and simultaneously protected oligodendrocytes and neurons against glutamate-mediated damage with the -amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate antagonist 2,3-dihydroxy-6-nitro-7- sulfamoylbenzo(f)quinoxaline (NBQX) and the neuroprotector glycine–proline–glutamic acid (GPE; N-terminal tripeptide of insulin-like growth factor). Remarkably, administration at an advanced stage of unremitting EAE of either a combination of NBQX and GPE, or preferably all three latter reagents, resulted in amelioration of disease and repair of the CNS, as assessed by increased oligodendrocyte survival and remyelination, and corresponding decreased paralysis, inflammation, CNS apoptosis and axonal damage. Each treatment reduced the expression of nitric oxide and a large panel of proinflammatory and immunoregulatory cytokines, in particular IL-6 which plays a critical role in mediating EAE. Mice displayed discernible improvements in all physical features examined. Disease was suppressed for 5 weeks, but relapsed when treatment was suspended, suggesting treatment must be maintained to be effective. The above approaches, which allow CNS repair by inhibiting inflammation and/or simultaneously protect neurons and oligodendrocytes from damage, could thus be effective therapies for multiple sclerosis.

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A role for α4 and β7 integrins in mediating leucocyte entry into the central nervous system in the multiple sclerosis (MS)-like disease experimental autoimmune encephalomyelitis (EAE) has been demonstrated. However, the individual contributions of their respective ligands mucosal addressin cell adhesion molecule-1 (MAdCAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-cadherin expressed on the blood-brain barrier has not been determined. In the present paper, it is shown that an antibody directed against MAdCAM-1, the preferential ligand for α4β7, effectively prevented the development of a progressive, non-remitting, form of EAE, actively induced by injection of myelin oligodendrocyte glycoprotein peptide (MOG(35-55)) autoantigen. Combinational treatment with both anti-MAdCAM-1, VCAM-1, and intercellular adhesion molecule-1 (ICAM-1) (ligand for integrin lymphocyte function-associated antigen (LFA)-1) mAbs led to more rapid remission than that obtained with anti-MAdCAM-1 antibody alone. However, neither MAdCAM-1 monotherapy, nor combinational antibody blockade was preventative when administered late in the course of disease progression. In conclusion, MAdCAM-1 plays a major contributory role in the progression of chronic EAE and is a potential therapeutic target for the treatment of MS. Critically, antivascular addressin therapy must be given eaA role for alpha4 and beta7 integrins in mediating leucocyte entry into the central nervous system in the multiple sclerosis (MS)-like disease experimental autoimmune encephalomyelitis (EAE) has been demonstrated. However, the individual contributions of their respective ligands mucosal addressin cell adhesion molecule-1 (MAdCAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-cadherin expressed on the blood-brain barrier has not been determined. In the present paper, it is shown that an antibody directed against MAdCAM-1, the preferential ligand for alpha4beta7, effectively prevented the development of a progressive, non-remitting, form of EAE, actively induced by injection of myelin oligodendrocyte glycoprotein peptide (MOG(35-55)) autoantigen. Combinational treatment with both anti-MAdCAM-1, VCAM-1, and intercellular adhesion molecule-1 (ICAM-1) (ligand for integrin lymphocyte function-associated antigen (LFA)-1) mAbs led to more rapid remission than that obtained with anti-MAdCAM-1 antibody alone. However, neither MAdCAM-1 monotherapy, nor combinational antibody blockade was preventative when administered late in the course of disease progression. In conclusion, MAdCAM-1 plays a major contributory role in the progression of chronic EAE and is a potential therapeutic target for the treatment of MS. Critically, antivascular addressin therapy must be given early in the course of disease prior to the establishment of irreversible damage if it is to be effective, as a single treatment modality.

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Experimental autoimmune encephalomyelitis (EAE) is an artificially induced demyelination of the central nervous system (CNS) that resembles multiple sclerosis in its clinical, histopathological, and immunological features. Activated Th1 and Th17 cells are thought to be the main immunological players during EAE development. This study was designed to evaluate peripheral and local contribution of IL-17 to acute and chronic EAE stages. C57BL/6 mice were immunized with MOG plus complete Freund's adjuvant followed by pertussis toxin. Mice presented an initial acute phase characterized by accentuated weight loss and high clinical score, followed by a partial recovery when the animals reached normal body weight and smaller clinical scores. Spleen cells stimulated with MOG produced significantly higher levels of IFN-γ during the acute period whereas similar IL-17 levels were produced during both disease stages. CNS-infiltrating cells stimulated with MOG produced similar amounts of IFN-γ but, IL-17 was produced only at the acute phase of EAE. The percentage of Foxp3+ Treg cells, at the spleen and CNS, was elevated during both phases. The degree of inflammation was similar at both disease stages. Partial clinical recovery observed during chronic EAE was associated with no IL-17 production and presence of Foxp3+ Treg cells in the CNS. © 2013 Sofia Fernanda Gonçalves Zorzella-Pezavento et al.

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O objetivo desta investigação foi avaliar o padrão degenerativo de diversos tratos de substância branca após lesão isquêmica estriatal, correlacionando o processo degenerativo com os padrões de ativação microglial e expressão de Nogo-A. Para isso, foi induzida isquemia focal com injeção estereotáxica de endotelina no estriado de ratos adultos, e nos animais controle apenas injetou-se solução salina estéril. Os animais foram perfundidos 3, 7, 14 e 30 dias após isquemia. O cérebro removido, pós-fixado, crioprotegido, cortado em criostato e os cortes obtidos submetidos à investigação imunoistoquímica com os seguintes anticorpos: Anti-GFAP (1:2000,Dako), Anti-Tau-1 (1:500,Chemicon), Anti-MBP (1:100,Chemicon International), Anti-Nogo A (1:100,Invitrogen), Anti-Iba1 (1:1000, WAKO), Anti-ED1 (1:500, Serotec) e Anti-MHC-II (1:100 Abcam), além da visualização do padrão lesivo com violeta de cresila. As lâminas marcadas pelos diferentes métodos foram avaliadas qualitativamente e algumas também quantitativamente (Anti-Nogo A, Anti-ED1, Anti-MHC-II e Anti-Tau-1), com contagens realizadas no estriado e no corpo caloso. Os dados foram tabulados, submetidos à análise estatística pelo teste de Tukey (p<0,05) e capturadas micrografias dos achados mais representativos. As lâminas coradas com violeta de cresila revelaram um aumento da densidade celular pela infiltração de células inflamatórias à área isquêmica, com aumento expressivo ao 7º dia. Nas lâminas imunomarcadas para GFAP foi encontrado aumento progressivo da população de astrócitos, assim como um aumento do volume celular em 7 e 14 dias. Oligondendrócitos patológicos marcados com Tau-1 tiveram pico de marcação ao 3º dia no estriado e ao 7º dia no corpo caloso, e a perda de compactação de mielina identificada pelo MBP foi melhor observada ao 14º dia, nos diferentes tratos. A ativação microglial identificada pelas diferentes imunomarcações apresentou seu pico ao 7º dia, tanto em estriado como em corpo caloso, porém no corpo caloso com um número muito menor quando comparado com o estriado. A morfologia microglial sofreu variações, sendo encontrado o fenótipo ramificado nos animais controles, assim como nos tempos precoces e tardios pós isquemia e o padrão amebóide/fagocítico ao 7º dia, coincidente com o maior número de células ativadas. A contagem de células Nogo-A + teve seu pico observado ao 3º dia no estriado, não sendo observadas no corpo caloso diferenças de expressão de Nogo-A entre 3 a 14 dias, apenas uma diminuição quando comparado a 30 dias. Sendo assim, microinjeções de ET-1 no estriado induziram conspícua perda tecidual, concomitante com ativação microglial progressiva, astrocitose, perda da imunoreatividade para proteína básica de mielina e lesão de oligodendrócitos em diversos tempos de sobrevida após isquemia focal. Estes eventos acometem alguns tratos de SB, como o corpo caloso. O estabelecimento da evolução temporal destes eventos neuropatológico é a base para estudos futuros, nos quais se deverá manipular a resposta inflamatória com intuito de minimizar estas alterações teciduais.

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Pós-graduação em Biologia Geral e Aplicada - IBB