Introduction: Microbial fermentation of carbohydrates in forestomach of ruminants produces large amounts of short-chain fatty acids (SCFA, mainly acetic acid, propionic acid, and n-butyric acid). The majority of these substrates is taken up directly across the ruminal wall. After luminal uptake into the epithelial cells, SCFA mainly occur in the dissociated form due to the intracellular pH of ~7.4. Moreover, a big portion of SCFA is metabolised within the cytosol. Main end products of epithelial SCFA metabolism are ketone bodies (D-3-hydroxybutyric acid and acetoacetic acid) and lactic acid. Both intact SCFA and ketone bodies and lactate need to be efficiently extruded from the ruminal epithelial cells to prevent a lethal drop of intracellular pH and counteract osmotic load of the cytosol. All these substances are less lipophilic in comparison to the undissociated form of SCFA. Thus, dissociated SCFA (SCFA-) and their metabolites need Protein mediated mechanisms for the extrusion across the basolateral side of ruminal epithelium. One mechanism suggested to be involved in the extrusion of SCFA- across basolateral membrane of the ruminal epithelium is the monocarboxylate transporter 1 (MCT1). Functionally, MCT1 was first assumed to operate as proton-coupled transporter for monocarboxylates including SCFA. Nonetheless, a recent study found a bicarbonate dependent anion exchange mechanism which turned out to be sensitive to MCT1 Inhibitors at the basolateral side of the ruminal epithelium pointing to the ability of MCT1 to act as an anion exchanger. However, in these experiments the inhibition of MCT1 abolished bicarbonate dependent transport only by half. This suggests the involvement of further anion exchanger(s) in the transport of SCFA across the basolateral membrane of ruminal epithelium. Promising candidates to underlie this exchange are the putative Anion exchanger 1 (PAT1) and a transport protein designated „down-regulated in adenoma“ (DRA). Materials and Methods: Sheep rumen epithelium was mounted in Ussing Chambers under short-circuit conditions. Radioactively labelled acetate (ac) was added to the serosal side. Serosal to mucosal flux of ac (Jsm ac) was measured with or without anion Exchange inhibitors (50 mM NO3- or 1 mM DIDS) or the MCT1 inhibitor p-hydroxy mercuribenzoic acid (pHMB; 1.5 mM) in the serosal buffer solution. The inhibitors were added alone or in combination with each other. Furthermore, mucosal to serosal flux of radioactivelly labelled ac or butyrate (bu) (Jms ac, bu) was measured in the presence or absence of SO42-, Cl- or NO3- (50 mM respectively) as exchange substrate in the serosal buffer solution. Immunohistochemical staining was conducted to locate PAT1 and DRA by use of commercially available antibodies. Results: NO3- and pHMB significantly reduced Jsm ac by 57 % and 51 %, respectively. When pHMB was applied after pre-incubation with NO3- an additional inhibition of Jsm ac was observed. Vice versa, NO3- further inhibited Jsm ac when epithelia were pre-incubated with pHMB before. DIDS had no inhibitory effect on SCFA flux. Serosal presence of SO42- or Cl- enhanced Jms ac significantly. Regarding bu, Cl- or SO4 2- also enhanced Jms bu significantly. The different anions available in the serosal buffer solution numerically enhanced Jms in the order of SO4 2- > Cl- for both ac and bu, which corresponds to the known affinity sequence of PAT1 and DRA. Immunohistochemistry revealed localization of PAT 1 in the stratum basale, whereas DRA was not detectable using this method. Conclusions: Basically, this study supports the suggestion that MCT1 works as an Anion exchanger in ruminal epithelium. In addition, it clearly shows that there is at least one further anion exchanger involved in the basolateral extrusion of SCFA and their metabolites. The functional and immunohistochemical findings suggest that PAT1 holds a significant role in this respect.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 5 uppsatser.

Orientador: Irani Quagio-Grassiotto / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T18:28:03Z (GMT). No. of bitstreams: 1 Mazzoni_TalitaSarah_M.pdf: 22131608 bytes, checksum: df7814a1f55f5088400f2b70e4520216 (MD5) Previous issue date: 2009 / Resumo: Numa nova visão da morfogênese gonadal, sua descrição em Cyprinus carpio, mostra como a proliferação e diferenciação de células germinativas e somáticas a partir do primórdio gonadal levam à formação das diferentes estruturas ovarianas e testiculares e à constituição do epitélio germinativo que margeia as lamelas ovígeras e os túbulos testiculares. Em C. carpio, o primórdio gonadal é formado por células germinativas primordiais (CGPs) rodeadas por células somáticas. Após sucessivas divisões mitóticas das células somáticas, o tecido gonadal aumenta em comprimento e espessura. As CGPs isoladas entre células somáticas se dividem mitoticamente formando grupos de células germinativas, que se organizam em cordões contínuos, os quais são invadidos por células somáticas, levando à uma reorganização estrutural e diferenciação gonadal. Nas gônadas femininas, as oogônias são envolvidas por expansões citoplasmáticas das agora células pré-foliculares, formando cistos, delimitados por uma membrana basal em formação. Cada oogônia divide-se por mitose, formando novas oogônias ou entra em meiose originando os oócitos. Com a entrada e permanência em diplóteno, os oócitos, ainda no interior dos cistos, iniciam seu desenvolvimento que completar-se-á no interior dos folículos ovarianos. As células pré-foliculares progressivamente interpenetram nos cistos e envolvem cada oócito individualizando-os. Estas gradativamente sintetizam a membrana basal envolvendo progressivamente o folículo em formação. As células foliculares assentadas em parte na membrana basal do próprio epitélio germinativo mantêm uma região de contato entre o folículo ovariano e o epitélio germinativo, que compartilham uma mesma membrana basal. Ao término da foliculogênese, o oócito inicia seu crescimento primário. No tecido gonadal, células mesenquimais se interconectam e se diferenciam, dando origem ao estroma ovariano, isolado do compartimento germinativo pela membrana basal. Células indiferenciadas do estroma emitem prolongamentos que contatam os folículos em formação, constituindo a teca. Células somáticas periféricas por migração e invaginação no tecido gonadal, formam as lamelas ovígeras. Lâminas teciduais de células somáticas formam-se em ambos os lados do ovário, projetando-se até se contatarem, formando o lúmen ovariano. Nas gônadas masculinas, as células somáticas, pré- Sertoli, invadem os cordões contínuos de CGPs. Estas, agora espermatogônias, são envolvidas por expansões citoplasmáticas das células de Sertoli, formando cistos. Estes formam conjuntos celulares que se distribuem ao longo da gônada, cada qual circundado por células somáticas. Ao redor de cada conjunto celular, inicia-se a formação da membrana basal, porém de forma incompleta. Gradativamente, os cistos de espermatogônias que constituem um mesmo conjunto, afastam-se uns dos outros, criando um espaço central. Células somáticas de conjuntos celulares adjacentes afastam-se, permitindo fusão entre os dois conjuntos celulares e aumento do espaço central formando um único compartimento luminal, delimitado por cistos de espermatogônias, estes, apoiados na membrana basal. Formam-se os túbulos testiculares e o epitélio germinativo masculino é estabelecido. O compartimento germinativo encontra-se agora separado pela membrana basal dos demais componentes celulares, que irão se diferenciar no compartimento intersticial. Inicia-se a espermatogênese no interior de cada cisto, de forma sincrônica. Após espermiogênese, os espermatozóides são liberados no lúmen, e os túbulos testiculares se anastomosam, culminando com a formação do ducto espermático na porção dorsal do testículo / Abstract: The description of gonadal morphogenesis in Cyprinus carpio provides a new vision of proliferation and differentiation of germ and somatic cells from the gonadal primordium leading to the formation of different ovarian and testicular structures, and the constitution of germinal epithelium which borders the ovigerous lamellae and the seminiferous tubules. In C. carpio the gonadal primordium is an elongated structure with individual PGCs scattered among somatic cells. The PGCs divide and organize into continuous cords that are delimited by the somatic cells. Then, in female gonad, somatic cells move into the cords, wrap around and individualize the PGCs that subsequently differentiate in oogonia. Each oogonium is wrapped by the now prefollicle cells giving rise to a cyst. Prefollicle cells rest upon a forming basement membrane. Inside the cysts oogonium proliferates by mitosis, originating new oogonia. Or, they enter into meiosis, becoming oocytes. Oocytes advance to diplotene where meiosis is arrested. Still inside the cysts oocytes enter primary growth, they are subsequently surrounded by prefollicle cells, and they become ovarian follicles. The differentiating gonad maintains a compact structure, continues elongating and becomes larger. Invaginations appear in the ventral region of the ovary; these form the ovigerous lamellae. Mesenchymal cells scattered inside the lamellae move away from one another giving rise to the extra-vascular space in the developing stroma where the cellular processes of these cells connect to one another and form a cellular net. Meanwhile, epithelial cells coming from the gonad periphery, and present in the ventral invaginations, associate with oogonia forming germinal epithelium. These also interact with the follicles that become connected to the epithelium sharing some extension of the basement membrane. Mesenchymal cells surround the ovarian follicles, becoming theca and, include the follicle, forms the follicle complex. On either side of the developing ovary, a coelomic epithelial cell proliferation forms a laminar tissue that grows ventrally, then extending beneath the developing ovary and fusing to form the central lumen of the carp cystovarian ovary. In male gonad, somatic cells move into the cords, wrap around and individualize the PGCs that subsequently differentiate in spermagonia. Each spermatogonium wrapped by the now pre-Sertoli cells giving rise to a cyst. The cysts join one another forming clusters. A basement membrane is synthesized around each cluster. Pre-Sertoli cells rest upon the forming basement membrane. In the center of the clusters a space is created when pre-Sertoli cells move away from one another. Then, nearby clusters fuse to one another that become connected by the same luminal space. The progressive fusion of the clusters gives rise to the seminiferous tubules that are bordered by the new formed germinal epithelium constituted by the cysts that rest upon the basement membrane. Mesenchymal cells surround the seminiferous tubules give rise to the cellular components of the interstitial compartment. Inside the cysts spermatogenesis starts. As the final spermatic cells are released into the luminal compartment, the anostomosis of the testicular tubules occurs forming the spermatic duct on the dorsal region of the testis / Mestrado / Biologia Celular / Mestre em Biologia Celular e Estrutural

Orientador: Irani Quagio-Grassiotto / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-23T21:20:24Z (GMT). No. of bitstreams: 1 Mazzoni_TalitaSarah_D.pdf: 26204829 bytes, checksum: b3ecbe44f1a0367d6194fb7c297136c2 (MD5) Previous issue date: 2013 / Resumo: Considerando o status atual de conhecimento da morfogênese e diferenciação gonadal nos Teleostei frente à restrição de informações, especialmente em aspectos tangentes ao estabelecimento do epitélio germinativo e sua relação com a formação da estrutura gonadal tomou-se aqui como modelos biológicos Tanichthys albonubes, Gymnocorymbus ternetzi, Corydoras schwartzi, Amatitlania nigrofasciata e Poecilia reticulata, representando as séries Otophysi, Percomorpha e Atherinomorpha, visando estabelecer uma análise comparativa da diferenciação gonadal entre as espécies, considerando suas posições na escala filogenética. A proliferação e diferenciação de células germinativas e somáticas a partir do primórdio gonadal em T. albonubes, G. ternetzi, C. schwartzi, A. nigrofasciata e P. reticulata levam à formação das diferentes estruturas ovarianas e testiculares e à constituição do epitélio germinativo que margeia as lamelas ovígeras e os túbulos/lóbulos testiculares. Nesses animais, o primórdio gonadal é formado por células germinativas primordiais (CGPs) rodeadas por células somáticas. Após sucessivas divisões mitóticas das células somáticas, o tecido gonadal aumenta, originando uma gônada indiferenciada, com as mesmas características morfológicas entre machos e fêmeas de T. albonubes e C. schwartzi. Em A. nigrofasciata e P. reticulata grupos de células germinativas e somáticas organizam-se de maneira distintas em machos e fêmeas. Nas gônadas femininas, as CGPs estão distribuídas por todo o tecido gonadal, enquanto que nas masculinas, as CGPs localizam-se na periferia. Na região dorsal das gônadas masculinas de A. nigrofasciata e P. reticulata, células somáticas organizam-se formando o ducto testicular, enquanto que em T. albonubes, G. ternetzi e C. schwartzi esse é a última estrutura a se formar. Nas gônadas femininas das cinco espécies, os processos envolvidos na diferenciação gonadal, como a foliculogênese, o estabelecimento do epitélio germinativo e a formação da cavidade ovariana são bastante semelhantes. Nas gônadas masculinas, as células somáticas, pré-Sertoli, associam-se às CGPs, formando cistos de espermatogônias; estas proliferam formando conjuntos celulares. Em T. albonubes e A. nigrofasciata os cistos de espermatogônias que constituem um mesmo conjunto, afastam-se uns dos outros, criando um espaço central, que se torna maior, originando um compartimento luminal, delimitado por cistos de espermatogônias. Formam-se os túbulos e lóbulos testiculares e o epitélio 2 germinativo masculino é estabelecido. Em G. ternetzi o tecido gonadal masculino é estabelecido e organizado em túbulos após a diferenciação gonadal feminina, sobre um ovário previamente desenvolvido, constituindo uma diferenciação gonocorística do tipo indireta. C. schwartzi apresenta um tecido gonadal masculino compacto, que sofre degenerações no interior de estruturas acinares compostas por cistos, para constituir os túbulos testiculares. Em P. reticulata, os conjuntos de espermatogônias conectam-se ao ducto em formação, originando os primeiros lóbulos testiculares. Ao final da diferenciação gonadal, os testículos de T. albonubes, G. ternetzi e C. schwartzi apresentam espermatogônias distribuídas aleatoriamente no túbulo. Estes anastomosam-se, caracterizando o testículo como tubular anastomosado. Em P. reticulata, as espermatogônias ficam restritas na região periférica dos lóbulos, os quais não apresentam lúmen testicular, características estas de um testículo lobular restrito. A mesma distribuição aleatória de cistos nos túbulos dos Otophysi ocorre nos lóbulos testiculares de A. nigrofasciata, caracterizando um testículo com organização lobular do tipo irrestrita / Abstract: Considering the lack of information about the gonadal morphogenesis and differentiation in Teleostei, especially in tangent aspects concerning the establishment of the germinal epithelium and its relation with the formation of the gonadal structure, in the present study, it was taken Tanichthys albonubes, Gymnocorymbus ternetzi, Corydoras schwartzi, Amatitlania nigrofasciata and Poecilia reticulata as biological models, representing the series Otophysi, Percomorpha and Atherinomorpha, to establish a comparative analysis of the gonadal differentiation among the species, taking into account their position in the phylogenetic scale. The proliferation and differentiation of germ and somatic cells from the gonadal primordium of the T. albonubes, G. ternetzi, C. schwartzi, A. nigrofasciata and P. reticulata lead to the formation of different testicular and ovarian structures and to the formation of the germinal epithelium of the ovigerous lamellae and the testicular lobules/tubules. In these animals, the gonadal primordium is formed by primordial germ cells (PGCs) surrounded by somatic cell. After successive mitotic divisions of the somatic cells, the gonadal tissue increases, resulting in a undifferentiated gonad, with the same morphological characteristics between males and females of T. albonubes and C. schwartzi. In A. nigrofasciata and P. reticulata groups of germ and somatic cells organize distinctly in males and females. In the female gonads, the PGCs are distributed throughout the gonadal tissue. In the male, the PGCs are located in the periphery. In the dorsal region of the male gonads of A. nigrofasciata and P. reticulata somatic cells are organized forming the testicular duct, whereas at T. albonubes, G. ternetzi and C. schwartzi this is the last structure formed. In female gonads of the five species, the processes involved in gonadal differentiation, such as folliculogenesis, the establishment of the germinal epithelium and the formation of the ovarian cavity are quite similar. In male gonads, the somatic cells, pre-Sertoli, associate to the PGCs forming cysts of spermatogonia; these proliferate and form clusters. In T. albonubes and A. Nigrofasciata, the cysts of the spermatogonia, which form a single cluster, move away from each other, creating a central space, which becomes greater, originating a luminal compartment, delimited by cysts of spermatogonia. Thus, testicular tubules and lobules are formed and male germinal epithelium is established. In G. Ternetzi, the male gonadal tissue is established and organized in tubules after the female gonadal 4 differentiation on an ovary previously developed, constituting an indirect gonochoristic differentiation. C. schwartzi presents a compact male gonadal tissue, which undergoes degeneration within acinar structures composed of cysts, forming the testicular tubules. In P. reticulata, the clusters of spermatogonia connect to the duct in formation, originating the first testicular lobules. At the end of gonadal differentiation, the testis from T. albonubes, G. ternetzi and C. schwartzi present spermatogonia, distributed along the tubule. These anastomose, characterizing the testis as anastomosing tubular. In P. reticulata, the spermatogonia are restricted at the periphery of the lobules, which do not have lumen, features of a restricted lobular testis. The same random distribution of cysts in the tubules of the Otophysi occurs in testicular lobules of A. nigrofasciata, featuring a testis with unrestricted lobular organization / Doutorado / Biologia Celular / Doutora em Biologia Celular e Estrutural

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19561号 / 医博第4068号 / 新制||医||1013(附属図書館) / 32597 / 京都大学大学院医学研究科医学専攻 / (主査)教授 吉村 長久, 教授 戸口田 淳也, 教授 高橋 淳 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

For many developing tissues, their shape is established early in development and needs to be scaled isotropically during subsequent growth. The way by which cells inside tissues enable coordinated isotropic tissue scaling is not understood, however, as most studies focused on changing tissue shapes during development. In this study, I follow cell and tissue shape changes in the zebrafish retinal neuroepithelium, which forms a smooth cup early in development and maintains this architecture as it grows. By 3D tissue-wide analysis, I identify global cell elongation as a cellular mechanism that can maintain retinal shape during growth. Timely cell height increase occurs concurrently with a non-cell autonomous actin redistribution, during which the ratio of apico-basal to lateral actin intensity increases. Blocking actin redistribution and cell height increase perturbs isotropic tissue scaling and leads to a disturbed, folded tissue shape. Taken together, these data show how global changes in cell shape enable isotropic growth of the developing retinal neuroepithelium, a concept that could also apply to other systems.

Made available in DSpace on 2016-01-26T12:51:28Z (GMT). No. of bitstreams: 1 vivianecuri_tese.pdf: 3356542 bytes, checksum: 3e315d421d5b2c78bdb72380eb601099 (MD5) Previous issue date: 2010-11-29 / Alcoholism is a public health problem worldwide, involving thousands of men and women, bringing serious consequences as a disease in all organs of the human body, especially the stomach, liver, heart and brain. The consumption of alcoholic beverages for infants and mothers have attracted the attention of researchers in recent decades, with significant. Objective: This study aimed to evaluate the effects of ethanol in the junctional epithelium, adamantine epithelium, epithelium of attached gingiva and periodontal ligament of the upper first molar of the rat, during lactation. Materials and Methods: To this end, we used mice with a day of postnatal life, whose mothers received 20% ethanol in drinking water and rats whose mothers do not received ethanol during the entire lactation. After 21 days, the chicks were sacrificed with anesthetic overdose (Hypnol 3%). The heads were separated and fixed in a solution of "alfac" (alcohol 80% -85 ml, 10 ml of formalin and acetic acid 5-ml), embedded in paraffin and frontal serial sections were stained with hematoxylin and eosin. The cuts were focused light microscope (100x) fitted with a camera lucida. The nuclei of cells from tissue fragments were designed on paper with increased end of 1000x. and 50 nuclei of each structure were outlined with black pencil for later measurement of larger (D) and smaller (d)diameters. Once determined the diameters were estimated karyometric following parameters: geometric mean diameter ratio D / d, perimeter, area, volume, relationship between volume and area, eccentricity, shape coefficient and contour índex. This work also was done using a grid printed on paper. The images were drawn on the grid. In order to assess the volumes and cell cytoplasm, the nucleus / xxiv cytoplasm ratio, the numerical cell density, relation to the external surface / basal layer, the thickness of epithelial layers and the density of the surface was sometimes used the count of the points and sometimes the number of intersections and applied to stereological equations appropriate for each of these variables. All data collected were submitted to non-parametric statistics (Wilcoxon-Mann-Whitney). Results: Histologically, the superior maxillar molar tooth of the rat treated with ethanol was not erupted or partially eruído; the junctional epithelium was reduced and the adamant epithelium was in full function and consists of high palisade cells. The epithelium of attached gingiva was more slender and composed of smaller cells. In the Periodontal ligament was possible to observe bigger and disorganizedfibers. The nuclei of the epithelia studies have shown decreased values after Karyometry, for larger and smaller medium diameters, volume, area, perimeter, and the relation V / A. Stereologically could be observed in the junctional epithelium, adamantine and the attached gingiva, less voluminous cell with scarce cytoplasm leading to a greater number of cells per mm3 of tissue. The disorganized periodontal ligament showed larger fibers with smaller number per mm3. Conclusion: In this study, ethanol resulted in a framework of epithelial hypotrophy, indicating a direct action on the junctional and adamantineepithelium, epithelium of attached gingiva and periodontal ligament. / O alcoolismo é um problema de saúde pública mundial, envolvendo milhares de homens e mulheres, trazendo conseqüências graves como doença em todos os órgãos do corpo do humano, em especial o estômago, o fígado, o coração e o cérebro. O consumo de bebidas alcoólicas por lactantes e lactentes vem despertando a atenção dos pesquisadores, nas últimas décadas, com achados significantes. Objetivo: Este trabalho teve como objetivo avaliar os efeitos do etanol no epitélio juncional, epitélio adamantino, epitélio da gengiva inserida e ligamento periodontal do primeiro molar superior do rato, durante a lactação. Materiais e Métodos: Para tal, foram utilizados ratos com um dia de vida pós-natal, cujas mães receberam etanol a 20% na água do bebedouro e ratos cujas mães não receberam o etanol, durante toda a lactação. Ao final de 21 dias, os filhotes foram sacrificados com sobredosagem anestésica (Hypnol a 3%). As cabeças foram separadas e fixadas em solução de alfac (álcool 80%-85 ml, formalina-10 ml e ácido acético-5 ml), incluídas em parafina e os cortes frontais seriados foram corados com hematoxilina e eosina. Os cortes foram focalizados ao microscópio de luz (100x) munido de uma câmara clara. Os núcleos das células dos tecidos estudados foram projetados sobre papel com aumento final de 1000x. e 50 núcleos de cada estrutura foram contornados com lápis preto para posterior medição dos diâmetros maior (D) e menor (d). Uma vez determinados os diâmetros, foram estimados os seguintes parâmetros cariométricos: diâmetro geométrico médio, relação entre D/d, perímetro, área, volume, relação entre volume e área, xxi excentricidade, coeficiente de forma e índice de contorno. Neste trabalho também, foi utilizada uma grade impressa sobre papel. As imagens obtidas foram desenhadas sobre a grade. Com a finalidade de se avaliar os volumes citoplasmáticos e celular, a relação núcleo/citoplasma, a densidade numérica celular, a relação superfície externa/ camada basal, a espessura das camadas epiteliais e a densidade da superfície, foi utilizada ora a contagem de pontos ora o número de intersecções e aplicadas às equações estereológicas apropriadas para cada uma dessas variáveis. Todos os dados colhidos foram submetidos à estatística não-paramétrica (teste de Wilcoxon-Mann-Whitney). Resultados: Histologicamente, o dente molar do maxilar superior do rato tratado com etanol não estava erupcionado ou então, parcialmente erupcionado; o epitélio juncional estava reduzido e o epitélio adamantino presente estava em plena função e constituído de células altas em paliçada. O epitélio da gengiva inserida era mais delgado e constituído de células menores. No ligamento periodontal foi possível observar fibras desorganizadas e maiores. Os núcleos dos epitélios estudados mostraram valores diminuídos, após cariometria, para os diâmetros maior, menor e médio; volume, área, perímetro e relação V/A. Estereologicamente foi possível observar, nos epitélios juncional, adamantino e da gengiva inserida, células menos volumosas com citoplasma mais escasso levando a um maior número de células por mm3 de tecido. O ligamento periodontal desorganizado mostrou fibras mais volumosas e com menor número por mm3. Conclusões: Neste estudo, o etanol ocasionou um quadro de hipotrofia epitelial, indicando uma xxii ação direta nos epitélios juncional e adamantino, epitélio de gengiva inserida bem como no ligamento periodontal.

"April 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 158-181). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Crohn's disease, a chronic inflammation of the bowel, is a multi-factorial condition where uncontrolled immune responses to luminal bacteria occur in genetically predisposed individuals. The first observable clinical signs are small ulcers that form at a specialised form of epithelium, follicle-associated epithelium (FAB). The FAB covers immune inductive sites, Peyer's patches, which function primarily as sensory areas that sample the externaI gut environment. Dendritic cells are one of the key cells that are involved in sensing luminal contents and orchestrating the gut immune system. The main aim of this thesis was to determine whether the barrier of the FAB is breached in Crohn's disease and if dysfunctional immune regulators, namely dendritic cells, playaroIe in initiating and/or maintaining the chronic intestinal inflammation. Using biopsies and surgical specimens, we were able to show that in Crohn's disease, there was an increased transmucosaI transport of Escherichia coli compared to specimens from ulcerative colitis and non-inflammatory bowel disease (IBD) controIs. Dendritic cells internalised a higher percentage of bacteria that had translocated across the FAB in the Crohn's samples. Furthermore, significantly higher concentrations of TNF-u was released upon bacterial stimulation by tissues from patients with Crohn's disease than in controIs. We went on to characterise the dendritic cells present in the Peyer's patches of patients with Crohn's disease. We found an accumulation of both immature and mature dendritic cells beneath the FAB, in the sub-epithelial dome (SED). Normally, mature dendritic cells migrate towards T cell-rich areas. However, we observed mature dendritic cells accumulating in the SED because they lacked the CCR7 migratory receptor. Furthermore, they were more prone to take-up bacteria, and produced TNF-α. To study the function of mucosal dendritic cells, we performed isolation experiments and mixed Iymphocyte reactions. Dendritic cells from both the ileum and blood of patients with active Crohn's had reduced capacity for inducing T cell proliferation than non-IBD controIs. Blood dendritic cells of patients in remission had normalised function that was similar to dendritic cells from healthy controls. The SAMPl/YitFc mice, considered an appropriate murine model for Crohn's disease, had an inherent permeability defect that increased with the chronicity of intestinaI inflammation. However unlike in human Crohn's disease, dendritic cells did not seem to playaroIe in murine ileitis. This thesis highlights the accumulation of the actively surveying dendritic cells that are prone to bacterial internalisation, and points to their possible different functional roles in active versus in-active disease; thereby confirming dendritic cells as one ofthe key components in the pathogenesis ofCrohn's disease.

L'intérieur des cellules eucaryotes est compartimenté en organites qui échangent des lipides et protéines entre eux et avec la membrane plasmique via le trafic vésiculaire. Dans les cellules polarisées comme les cellules épithéliales, dont la membrane plasmique est divisée en un pôle apical et un pôle basolatéral séparés par une ceinture de jonctions, le trafic vésiculaire est contrôlé par des systèmes de tri polarisé, permettant d'adresser les protéines appropriées au domaine membranaire approprié. Dans ces cellules épithéliales, le complexe adaptateur AP-1 contrôle l'adressage au pôle basolatéral et le trafic de la molécule d'adhésion E-Cadhérine, une protéine transmembranaire des jonctions d'adhérence. Il a de plus été démontré dans les cellules intestinales du nématode C. elegans et des mammifères qu'AP-1 est nécessaire au maintien de la polarité épithélial. J'ai étudié ces fonctions d'AP-1 chez l'organisme modèle Drosophila melanogaster. J'ai montré qu'AP-1 contrôle aussi le trafic de E-Cadhérine chez la Drosophile mais n'est pas requis pour la maintenance de la polarité de l'épithélium folliculaire, un épithélium entourant le cyste germinal femelle de 16 cellules au cours de l'ovogénèse chez la Drosophile. Ces expériences dans ce tissu m'ont amené à découvrir une nouvelle fonction de E-Cadhérine dans le cyste germinal. Les cellules de ce cyste sont connectées entre elles par des ponts cytoplasmiques stabilisés à l'issue de cytocinèses incomplètes. J'ai montré que les cellules du cyste mutantes pour AP-1 présentent un phénotype de multinucléation dû au décrochage des ponts cytoplasmiques. Ce phénotype corrèle avec un défaut d'adressage de E-Cadhérine dépendant d'AP-1 à la membrane plasmique entourant ces ponts, via les endosomes de recyclage. E-Cadhérine y est nécessaire pour leur ancrage à la membrane plasmique, un rôle qui avait été jusque-Là masqué par l'expression ectopique compensatoire de N-Cadhérine dans les mutants E-Cadhérine. Ce rôle d'E-Cadhérine passe par l'organisation de protrusions membranaires présentant l'aspect et contenant certains marqueurs protéiques des microvillosités observées au pôle apical des cellules épithéliales. / Eukaryotic cells are compartmentalized in organelles. Lipidic and proteic exchanges between organelles and the plasma membrane are controlled by vesicular trafficking. In polarised cells such as epithelial cells, whose plasma membrane is divided into an apical and a basolateral pole separated by a junctional belt, appropriate targeting of proteins to appropriate poles relies on polarised sorting mechanisms controlling vesicular trafficking. In these cells, the clathrin adaptor complex AP-1 controls basolateral targeting and trafficking of the adhesion molecule E-Cadherin, a transmembrane adherens junctions protein. AP-1 is furthermore necessary for epithelial polarity maintenance in intestinal epithelial cells in the nematode C. elegans and mammals. I studied AP-1 functions in the model organism Drosophila melanogaster. I showed AP-1 also controls E-Cadherin trafficking in Drosophila but is not required for polarity maintenance in follicular cells, an epithelium surrounding the female germline cyst during oogenesis. Experiments in this tissue led me to discover a new E-Cadherin function in the germline cyst. Germline cyst cells are interconnected by cytoplasmic bridges stabilised after incomplete cytokinesis. I showed AP-1 mutant cyst cells were multinucleated due to a detachment of cytoplasmic bridges from the plasma membrane. This phenotype correlated with an E-Cadherin AP-1-Dependent targeting defect from recycling endosomes to the plasma membrane surrounding these bridges. E-Cadherin is necessary for their anchoring to the plasma membrane, a role that was hidden by ectopic compensatory expression of N-Cadherin in E-Cadherin mutants. This new role is mediated by E-Cadherin-Dependent organisation of membrane protrusions similar in aspect with and containing proteins of microvillosities present at the apical pole of epithelial cells.