Orientadores: Karina Gottardello Zecchin, Edgard Graner / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-24T17:35:39Z (GMT). No. of bitstreams: 1 Ortega_RoseMara_D.pdf: 2691297 bytes, checksum: ea4bceee611c0e68c84223cc02b8fd52 (MD5) Previous issue date: 2014 / Resumo: Ácido graxo sintase (FASN - fatty acid synthase, EC 2.3.1.85) é a enzima metabólica responsável pela síntese endógena do ácido graxo saturado palmitato, a partir dos precursores acetil-CoA e malonil-CoA. Diversos estudos mostram que, em contraste com a maioria das células normais, FASN é altamente expressa em vários tipos de neoplasias malignas humanas, tais como as de próstata, mama e melanoma sendo que, em alguns destes tumores, a alta expressão de FASN está associada a um pior prognóstico. A inibição da enzima FASN resulta em inibição da proliferação e induz morte celular em diversas neoplasias malignas. Recentemente demonstramos que, in vitro, a inibição específica da atividade de FASN em linhagem celular de melanoma murino, B16-F10, induz a via intrínseca da apoptose, com liberação de citocromo c e ativação de caspase-3, assim como altera a composição dos ácidos graxos livres presentes nas mitocôndrias das células B16-F10. O objetivo deste trabalho foi investigar de que maneira a inibição farmacológica de FASN reduz a proliferação de células B16-F10, in vitro e in vivo, utilizando C75 como inibidor de FASN. O tratamento de células e animais com C75 reduziu significativamente a proliferação celular e induziu apoptose. Houve significativa redução de células na fase S do ciclo celular, com acúmulo de células de G0/G1, em comparação com os controles. Western blottings feitos a partir de extratos de células em cultura e de tumores intraperitoneais mostraram aumento de p21WAF1/Cip1, p27Kip1, redução de Skp2 e cdk2, sem mudanças nos níveis de cdk4, 6 e ciclina E após tratamento com C75. A especifidade destes resultados foi confirmada pela redução da atividade enzimática de FASN após tratamento com C75 e pelo silenciamento de FASN com RNAi. Efeito anti-tumoral de C75 foi sugerido pela formação de tumores subcutâneos de menor volume quando comparados aos tumores de animais controle. Nossos achados mostram que a proliferação de células de melanoma é dependente de FASN, e que sua inibição primeiramente altera os níveis de proteínas envolvidas na transição de G1 para S, para posteriormente induzir apoptose em células de melanoma B16-F10 / Abstract: Fatty acid synthase (FASN) is the metabolic enzyme responsible for the endogenous synthesis of the saturated long-chain fatty acid palmitate, from the precursors acetyl-CoA and malonyl-CoA. In contrast to most normal cells, the overexpression of FASN in several human malignancies, such as those of prostate, breast, ovary, melanoma, and soft tissue sarcomas has been associated with poor prognosis. FASN inhibition reduces cell proliferation by blocking DNA replication during S-phase, and induces apoptosis in several malignant neoplasias. We have previously shown that the specific inhibition of FASN activity significantly reduce proliferation and promote apoptosis, as demonstrated by the cytochrome c release and caspase-9 and -3 activation, as well as induces signi?cant changes in the free fatty acids composition of B16-F10 cells mitochondria. Here we investigated the events involved in cell cycle arrest subsequent to FASN inhibition with C75. C75 treatment significantly reduced melanoma cells proliferation and induced apoptosis in vitro and in mice. Cell cycle arrest after C75 treatment was evidenced by a significant increase in G0/G1 phase, as well as decline of the S phase, in comparison with untreated cells. Western blotting analysis showed significant accumulations of the tumor suppressor proteins p21WAF1/Cip1 and p27Kip1, together with decreased amounts of Skp2, essential for the proteasomal degradation of p27Kip1, and cdk2, a Ser/Thr protein kinase necessary for the G1/S transition, in C75-treated cells or mice tumors. The levels of other proteins involved in G1/S cell cycle progression, such as cyclin E, cdk4, and cdk6 were not affected by FASN inhibition. These results were confirmed by inhibition of FASN activity after C75 treatment and by RNAi for FASN. Antitumoral effect of C75 was suggested by reduced subcutaneous tumors volume when compared to controls mice. Our results suggest that melanoma murine B16-F10 cells proliferation is dependent on FASN activity, and its inhibition first modify the levels of some proteins involved in the transition G1?S of cell cycle, to finally induce apoptosis in neoplasic cells / Doutorado / Estomatologia / Doutora em Estomatopatologia

Orientador: Pablo Agustin Vargas / Texto em português e inglês. / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-25T00:22:26Z (GMT). No. of bitstreams: 1 Diaz_KatyaPulido_D.pdf: 16670871 bytes, checksum: b517ca4541e83574a899265d975bcafd (MD5) Previous issue date: 2014 / Resumo: Introdução: Os tumores das glândulas salivares (TGS) são lesões incomuns e correspondem a aproximadamente 3 a 10% das neoplasias que acometem a região de cabeça e pescoço. A angiogênese, proliferação celular e a expressão da enzima ácido graxo sintase (FASN) podem interferir nos mecanismos de progressão tumoral e comportamento clínico dos tumores malignos de glândulas salivares. Objetivos: Avaliar imunoistoquímicamente a angiogênese, índice de proliferação celular e expressão de FASN em tumores malignos de glândulas salivares maiores e menores e correlacionar a expressão destes biomarcadores com os dados clínicos e agressividade histopatológica além de comparar a expressão de FASN e Ki67 entre 12 casos de adenoma pleomorfo e 6 de carcinoma ex-adenoma pleomorfos. Pacientes e Métodos: Foram utilizadas 52 peças cirúrgicas de pacientes portadores de tumores malignos de glândulas salivares maiores e menores e 12 de adenomas pleomorfos como controle do marcador FASN e Ki67. As amostras de tecidos dos TGS malignos foram submetidas a reações imunoistoquímicas para os anticorpos CD31, CD34, CD105, e para ambos tipos de tumores Ki-67 e FASN. Para a quantificação microvascular e determinação da proliferação celular utilizamos os métodos quantitativos Microvessel Analysis Algorithm e Nuclear Image Analysis Algorithm com o software ImageScope (Aperio Scanscope® CS System). Foi utilizado o método semi-quantitativo convencional para a análise do marcador FASN. Resultados: O local anatômico mais acometido foi a parótida (67,3%), os pacientes apresentaram idade média de 50,2±21,9 anos e 17,6% tiveram metástases à distância. A densidade microvascular nas áreas intra e peritumorais com marcadores CD31, CD34 e CD105 não mostrou significância estatística em relação aos índices de proliferação celular ou expressão de FASN (P>0,05). Os TGS malignos de alto grau apresentaram altos índices de proliferação celular (P<0,006) maior expressão de FASN do que os TGS de baixo grau de malignidade (P<0,003) e de igual forma em 6 casos de carcinoma ex-adenoma pleomorfo do que em adenomas pleomorfos (P<0,001). Conclusões: Esses dados sugerem que os tumores malignos de glândulas salivares com altos índices de Ki-67 e FASN podem estar relacionados a maior proliferação celular em tumores de alto grau de malignidade e podem contribuir na identificação do componente maligno do carcinoma ex-adenoma pleomorfo / Abstract: Salivary gland tumors (SGT) are uncommon and account for approximately 3-10% of cancers affecting the head and neck region. Angiogenesis, cell proliferation, expression of the enzyme fatty acid synthase (FASN) may interfere with the mechanisms of tumor progression and clinical behavior of malignant SGT. Objectives: To assess the expression of biomarkers related to angiogenesis and cell proliferation, as well FASN protein in major and minor malignant SGT, correlating the results with clinical findings and histopathological agressivity. Also, to compare the expression of FASN and Ki67 between 12 pleomorphic adenomas and 6 carcinomas ex-pleomorphic adenomas. Patients and Methods: 52 surgical specimens from patients with malignant SGT were assessed. We performed immunohistochemical study for CD31, CD34, CD105, Ki67 and FASN antibodies. For quantification and determination of the microvascular density (MVD) of tumors, quantitative method was used with Microvessel Analysis Algorithm (software Aperio Scanscope® CS System) and for nuclear analysis was used Nuclear Image Analysis Algorithm, but for FASN only conventional semi-quantitative method was used. Results: The most affected anatomical site was the parotid gland (67.3 %), average age 50.2±21,9 years and 17.6% of patients had distant metastases. Microvascular analysis in intra and peritumoral areas with markers CD31, CD34 and CD105 showed no statistical significance in relation to rates of cell proliferation and expression of FASN (P >0.05). However, patients with high-grade malignant SGT showed higher rates of cell proliferation (P<0.006) and increased expression of FASN (P<0.003) at the same time to 6 cases of carcinoma ex-pleomorphic adenoma compared with 6 of pleomorphic adenoma (P<0.001). Conclusions: These data suggest that malignant salivary gland tumors with high levels of Ki-67 and FASN may be associated with high index of cellular proliferation in high-grade malignant SGT and its overexpression may be a useful marker for carcinoma ex-pleomorphic adenoma / Doutorado / Patologia / Doutora em Estomatopatologia

Orientador: José Angelo Camilli / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-23T08:42:16Z (GMT). No. of bitstreams: 1 Domingues_JulianaAlmeida_M.pdf: 6712230 bytes, checksum: abfef192b69eeb8cc178a08e435692fd (MD5) Previous issue date: 2013 / Resumo: Cimentos de fosfato de cálcio (CFC) a base de ?-TCP, que originam como processo final de cura uma hidroxiapatita deficiente em cálcio (CDHA) são muito utilizados como biomateriais para osso, por possuírem similaridade estrutural e química à porção inorgânica do tecido ósseo. Porém o uso dos CFC se restringe a pequenos defeitos bucomaxilofaciais e recobrimento de próteses metálicas, em função do déficit considerável de suas propriedades mecânicas. Visando melhorar as propriedades mecânicas dos CFCs estudos têm sido direcionados à aplicação de fibras de vários materiais, como as fibras de carbono, as fibras de vidro, as de carboneto, entre outras. No entanto, muitas dessas fibras introduzidas se mostraram tóxicas às células, impedindo sua aplicação clínica. Recentemente, os "whiskers" (fibras curtas de monocristal) de biocerâmicas vêm sendo estudados como outro tipo de reforço, cujos resultados têm se mostrado promissores por melhorarem as propriedades mecânicas e biológicas dos materiais. Nesse trabalho, a resposta biológica das CDHA pura e contendo 5 e 10% de "whiskers" de wollastonita, foram estudadas através de um sistema de cultivo celular com células osteoblásticas, o qual tem sido muito utilizado para elucidar a resposta celular em biomateriais. Porém cultivar células em CDHAs não é uma tarefa fácil, pois o processo de hidrólise sofrido por esses materiais promove a liberação de íons para o meio de cultura, o que acarreta na mudança de pH e concentração iônica do meio. Essas mudanças promoveram a morte das células após 48h de cultivo. Foi possível manter as células viáveis ao longo do tempo realizando a lavagem dos discos de CDHA com DMEM (Dulbecco's Modified Eagle Medium) antes da semeadura e também com a troca diária do meio de cultura. Nossos resultados demonstraram que as CDHA contendo "whiskers" foram capazes de estimular a proliferação celular quando comparadas com a placa de poliestireno e a CDHA pura. No ensaio de MEV foi possível observar uma densa camada celular na superfície da CDHA contendo 10% de "whiskers". A atividade da fosfatase alcalina (FAC) foi significativamente maior nas CDHAs contendo "whiskers", sendo proporcional a concentração de "whiskers" wollastonita nas amostras, o ensaio de mineralização corroborou com o ensaio de FAC, no qual a CDHA contendo 10% de "whiskers" apresentou maior produção de matriz mineralizada. Tendo-se em vista os presentes resultados pode-se dizer que as CDHA contendo "whiskers" de wollastonita são biomateriais promissores para engenharia tecidual óssea, pois foram capazes de estimular a proliferação e diferenciação celular, além da resistência mecânica melhorada pela adição dos "whiskers" / Abstract: Calcium phosphate cements (CFCs) are widely used as biomaterials for bone because they have chemical and structural similarity to the inorganic portion of bone tissue. But the use of CFCs is restricted to maxillofacial small defects and coating metallic prostheses, due to the considerable deficit of its mechanical properties. In order to improve the mechanical properties of CFCs studies have focused on the application of fibers of many materials such as carbon fibers, glass fibers, carbide fibers among others. However, many of these fibers are shown toxic to the cells, preventing their clinical application. Recently, the "whiskers" (short crystal fibers) of bioceramics have been studied as another type of reinforcement and the results have shown promise for improving the mechanical and biological properties of materials. In this work the biological response of hydroxyapatites deficient in calcium (CDHA) pure and containing 5 and 10% "whiskers" of wollastonite, were studied using a cell culture system with osteoblastic cells, which has long been used to elucidate the cell behavior in biomaterials. However cultivating cells in CDHAs is not an easy task because the hydrolysis process undergone by such materials promotes the release of ions to the culture medium, which results in the change of pH and ionic concentration of the medium. These changes promoted cell death after 48 h of cultivation. Cell viability was maintained for 14 days by a simple washing of CDHA discs with DMEM before cell culture and also with daily changes of culture medium. Our results demonstrate that CDHA containing "whiskers" were able to stimulate cell proliferation when compared to the polystyrene plate and CDHA pure. In the assay by SEM was possible to see a dense cell layer on the surface of the CDHA containing 10% "whisker." The alkaline phosphatase activity (ALP) was significantly higher in CDHAs containing "whiskers" being proportional to the concentration of "whiskers" wollastonite samples. The mineralization assay corroborated with ALP assay in which the CDHA containing 10% " whisker "showed higher production of mineralized matrix. In summary the CDHAs containing "whiskers" of wollastonite are excellent biomaterials for bone tissue engineering, because they were able to stimulate cell proliferation and differentiation, as well as mechanical strength improved by the addition of "whiskers" / Mestrado / Biologia Celular / Mestra em Biologia Celular e Estrutural

Orientador: Oslei Paes de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-19T00:01:15Z (GMT). No. of bitstreams: 1 Martinez_MarisolMartinez_M.pdf: 7220256 bytes, checksum: f7a9e6a4858d9247d65345dd79c7382b (MD5) Previous issue date: 2011 / Resumo: Os tumores odontogênicos (TO) são um grupo heterogêneo de lesões derivadas de tecidos dentários, que ocorrem nos ossos gnáticos e tecidos adjacentes. Os TO são raros, na grande maioria benignos, representando menos de 4% de todos os espécimes recebidos em laboratórios de patologia bucal. Os TO malignos freqüentemente apresentam dificuldades para diagnóstico e correta classificação, com vários pontos ainda não bem esclarecidos. O objetivo deste estudo foi analisar as características clínicas, histopatológicas e imunoistoquímicas em 39 casos de TO malignos. A idade média dos pacientes foi de 43,37 anos, com 16 casos acometendo pacientes do gênero feminino, 20 masculino e 3 de gênero desconhecido. Quatorze casos eram carcinoma ameloblástico (CA), 11 fibrossarcoma ameloblástico (FSA), 7 carcinoma espinocelular intra-ósseo primário (CEIP), 4 carcinoma odontogênico de células claras (COCC) e 3 carcinoma odontogênico de células fantasmas (COCF). Observou-se em alguns casos necrose, invasão perivascular, invasão perineural, infiltrado inflamatório e calcificações distróficas. A análise imunoistoquímica para citoqueratinas mostrou que a maioria dos casos foram positivos para CK5 e CK14 (69,2% e 53,8%), com expressão menor para CK7 e CK19. A imunoexpressão de Ki-67, p53 e p63 para CA foi 19,8%, 33,0% e 94,7%, respetivamente; para CEIP foi 52,9%, 55% e 91,5%; para COCC 9,0%, 4,5% e 60,8%, para COCF 17,4%, 20,9% e 95,9% e para FSA 16%, 28,0% e 10,% respectivamente. Onze casos foram negativos para CD138, e o restante dos casos mostraram variável perda da expressão focal para esse anticorpo. A expressão para E-caderina e ?-catenina foi negativa em 12 e 11 casos respectivamente, com perda de expressão focal, associada a variação da intensidade no restante dos casos. Dentre os casos positivos para ?-catenina, foram observados 5 casos com marcação nuclear / Abstract: Odontogenic tumors correspond to a heterogenous group of lesions derived from dental tissues, involving the jaws and adjacent tissues. OT are rare, te majority benign, representing less than 4% of all specimes of an oral pathology laboratory. OT frequently present difficulties for the correct diagnosis and classification, with various points yet to be clarified. The objetive of this study was to analyse the clinical, histological and the expression of immunohistochemical markers in 39 cases of malignant OT. The mean age of the patients was 43.37 years, with 16 cases occurring in women, 20 in men and in 3 the gender was not possible to obtain. Fourteen cases were ameloblastic carcinoma, 11 ameloblastic fibrosarcoma, 7 primary intraosseous squamous carcinoma, 4 clear cell odontogenic carcinoma and 3 ghost cell odontogenic carcinoma. In some cases markers of malignancies as necrosis, perivascular and perineural invasion, inflammation and dystrophic calcificications were observed. By immunohistochemistry most cases were positive for CKS 5 and 14, with lower expression for CKS 7 and 19. In AC Ki-67, p53 and p63 showed values of 19.8%, 33.0% and 94.7% respectively. Corresponding values for PISC were 52.9%, 55.0% and 91.5%, for CCOC of 9.0%, 4.5% and 60.8%; for GCOC of 17,4%, 20,9% e 95,9% and for AFS of 16%, 28,0%. Eleven cases were negative for CD138, and in all others expression was positive but variable. E-caderin and B-catenin was negative in 12 and 11 cases respectively, with variable expression in the positive cases. In 5 cases B-catenin also showed nuclear expression. / Mestrado / Patologia / Mestre em Estomatopatologia

A tolerância materno-fetal envolve, além do sistema imune, muitas peculiaridades quanto ao tipo de placenta e placentação. A placenta em bovinos é considerada não invasiva, e como conseqüência de uma implantação superficial, sem invasão endometrial, se estabelece uma barreira placentária complexa que se interpõe entre a circulação materna e fetal. Aliado a isso, a placenta um órgão que se encontra em constante diferenciação e proliferação celular além da alta atividade metabólica, fontes constantes de estresse e desafio para o sistema imune. Atuando nesse contexto, destacamos as proteínas de choque térmico (heat shock proteins HSP), proteínas que são expressadas em condições fisiológicas mas, em situações de estresse, sua expressão aumenta. Na placenta bovina já se constatou a expressão das HSP 60 e 70; contudo notou-se uma maior peculiaridade na expressão da HSP 60, que é maior no primeiro trimestre da gestação. Observando-se o perfil da presença e expressão dessa proteína na placenta bovina e, tendo em vista a característica desse órgão em apresentar populações leucocitárias funcionalmente distintas das do sangue periférico, levantou-se a hipótese da influência desta proteína sobre as células placentárias, particularmente sobre os leucócitos no processo de tolerância materno fetal. Desta forma, esse trabalho analisou a participação da HSP 60 em mecanismos imunes junto à alguns leucócitos placentários por meio de ensaio de proliferação pela técnica de CFSE, ensaio de fagocitose e ensaios bioquímicos como peroxidação lipídica; ciclo celular e potencial de membrana mitocondrial de células placentárias em cultivo. Nossos resultados mostraram que a HSP 60 não influencia a proliferação de linfócitos e outras células placentárias nas diversas condições testadas. Em contrapartida a HSP 60 aumenta a fagocitose e apoptose no terceiro terço gestacional, bem como a produção de radicais oxidados poliinsaturados e o potencial de membrana mitocondrial. Tendo em vista esses resultados, podemos observar que a HSP 60 nas células da placenta bovina possivelmente esteja modulando a cinética da ativação de mecanismos de sinalização de morte celular programada entre as células da placenta e o sistema imunológico. Esta hipótese assegura que, no concepto a termo, as variações hormonais e o sistema imune possam estar regulando o processo para o nascimento do feto. / The maternal-fetal tolerance involves, besides the immune system, many peculiarities regarding the type of placenta and placentation. The bovine placenta is considered not invasive and, as consequence of a superficial implantation without endometrial invasion, it establishes itself as complex barrier that interposes between the maternal and fetal circulation. In addition to that, placenta is an organ that undergoes continuous differentiation and cellular proliferation besides the high metabolic activity that represents a constant source of stress and challenge for the immune system. As an important component in this context, we highlight the heat shock proteins - HSP, that are usually expressed in physiological conditions but, in situations of stress, their expression increases. In the bovine placenta the expression of HSP 60 and 70 has already been verified; however HSP 60 showed a peculiar expression behavior, with higher staining in the first trimester of pregnancy. Considering the presence and expression profiles of HSP 60 in the bovine placenta allied to the particularity of presenting functional distinct leucocytes populations, a hypothesis was raised regarding the influence of this protein on the placental cells, particularly on the leucocytes in the process of fetal-maternal tolerance. Therefore, this work analyzed the role of HSP 60 in immune mechanisms related to some placental leucocytes by several approaches like proliferation assay by CFSE technique, phagocytosis assay and biochemical assays as lipoperoxidation; cell cycle phases and mitochondrial membrane potential of placental cells in culture. Our results showed that HSP 60 does not influence the proliferation of lymphocytes or any other placental cells in various conditions tested. On the other hand, HSP 60 increases phagocytosis and apoptosis in the third trimester, as well as the production of polyunsaturated oxide radicals and the mitochondrial membrane potential. In view of these results, we may infer that HSP 60 may be modulating the kinetics of activation mechanisms for signaling programmed cellular death between placental and immune cells. This hypothesis assures that, on the termed conceptus, the hormonal variation and the immune tolerance may be responsible for regulating the parturition process.

It is widely accepted that A-beta (Aβ) generated from amyloid precursor protein (APP) oligomerizes and fibrillizes to form neuritic plaques in the Alzheimer’s disease (AD) brain, yet little is known about the contribution of APP preceding AD pathogenesis. Our data presented here suggest that APP has a functional role in cell cycle regulation and proliferation. First, we demonstrat that APP is pathologically phosphorylated at Thr668 and that P-APP localizes to the centrosomes. Furthermore, P-APP is proteolytically processed in a cell cycle -dependent manner to generate its pathogenic metabolites. Using Stable Isotope Labeling by Amino Acids in Culture (SILAC) and mass spectrometry analyses, we also show that expression of APP results in the expression of proliferation-associated proteins and the phosphorylation of proteins associated with cell cycle regulation and transcription. Here, we demonstrate that APP expression and oligomeric Aβ42 elicit Ras/ERK signaling cascade and glycogen synthase kinase3 (GSK3) activation. Both ERK and GSK3 are known to induce hyperphosphorylation of tau and of APP at Thr668, and our findings suggest that aberrant signaling by APP facilitates these events. Supporting this notion, analysis of human brain samples show increased expression of Ras, activation of GSK3 and phosphorylation of APP and tau, which correlate with Aβ levels in the AD brains. Furthermore, treatment of primary rat neurons with Aβ recapitulate these events and show enhanced Ras-ERK signaling, GSK3 activation, upregulation of cyclin D1, and phosphorylation of APP and tau. The finding that Aβ induces Thr668 phosphorylation on APP, which we show enhances APP proteolysis and Aβ generation, denotes a vicious feed-forward mechanism by which APP and Aβ promote tau hyperphosphorylation and neurodegeneration in AD. Based on these results we hypothesize that aberrant proliferative signaling by APP plays a fundamental role in AD neurodegeneration and an inhibition of this would impede the mitotic catastrophe and neurodegeneration observed in AD.

Development, tissue renewal and longevity of multi-cellular organisms require the ability to switch between a proliferative state and quiescence, a reversible arrest from the cell cycle. The balance of quiescence and proliferation underlies the fundamental feature of generating and maintaining the appropriate number of cells, which is essential for tissue architecture, regeneration, and function. Disruption of quiescence and proliferation balance leads to hypo- or hyper-proliferative diseases. To date, the regulatory mechanism of proliferation has been well established, while cellular quiescence has remained a phenotypic description without a clearly defined molecular control mechanism. Simply, quiescence has long been considered a passive counterpart to proliferation. However, recent findings have revealed that quiescence is an actively maintained state exhibiting a unique gene expression pattern. While quiescence has been traditionally considered as a state (namely G0) outside of the cell cycle, it is in fact a collection of heterogeneous states. In studies conducted in the 70's and 80's using fibroblasts and lymphocytes, it has been observed that the longer the cells were kept under quiescence inducing conditions such as contact inhibition, the deeper the cells moved into quiescence. Deep quiescent cells are still able to reenter the cell cycle upon growth stimulation but they exhibit a longer pre-DNA synthesis phase [1-4]. Shallow quiescent state has also been recently reported in muscle and neural stem cells termed GAlert and "prime" quiescent state, respectively. Heterogeneous quiescent depth entails that cells vary in their sensitivity to growth signals, representing an important yet underappreciated layer of complexity in cell growth control. The cellular mechanisms that control the depth of quiescence remains elusive. In my thesis work, I first investigate the strengths of serum stimulation required for cells to exit deep and shallow quiescence as a determinant of quiescence depth. Through model simulations and experimental measurements, I further demonstrate that various components of the Rb-E2F pathway control quiescence depth with varying efficacy. The Rb-E2F pathway interacts with diverse cellular pathways that respond to environmental signals to jointly modulate quiescence depth. Given that certain circadian clock genes (e.g., Cry) affect key components in the Rb-E2F pathway, I tested the effect of Cry activity on quiescence depth. I found that increased Cry activity resulted in deeper quiescence, contrary to our anticipation based on the literature. Next, we constructed a library of mathematical models that represent possible interactions between Cry and the Rb-E2F pathway. We computationally searched this model library for links that could explain the experimental observations. The modeling search suggested that Cry upregulation may lead to increased expression of cyclin dependent kinase inhibitor (e.g., p21), which in turn drives cells into deeper quiescence. This model prediction was confirmed by my follow-up experiments. Collectively, my thesis work establishes an integrated modeling and experimental framework that will help us to further investigate diverse cellular mechanisms controlling the heterogeneous quiescence depth.

Le testicule des mammifères possède deux fonctions majeures : la production des spermatozoïdes et la synthèse des androgènes. Le maintien et la régulation de cette fonction sont sous le contrôle des facteurs endocrines et paracrines, mais sont aussi liés à l’homéostasie des lipides, notamment le cholestérol. Les récepteurs nucléaires des oxystérols (LXRs) sont des facteurs de transcription appartenant à la superfamille des récepteurs nucléaires. Les LXRs sont exprimés dans le tractus génital mâle et les testicules et leurs ligands y sont présents à des concentrations physiologiquement actives. Dans ces organes, ces récepteurs régulent l’homéostasie du cholestérol, un précurseur indispensable pour la synthèse des stéroïdes testiculaires. Ils contrôlent aussi les différentes étapes de la stéroïdogenèse en régulant les enzymes de la stéroïdogenèse. Enfin, leur rôle dans la balance prolifération/apoptose des cellules germinales est éminent. On assiste depuis les dernières décennies à une augmentation des anomalies de la différenciation de l’appareil génital mâle (hypospadias, cryptorchidisme) et du cancer du testicule, ainsi qu’à une diminution quantitative et qualitative de la production de spermatozoïdes. Il a été proposé que ces anomalies aient pour origine une perturbation du développement du testicule pendant la vie foetale. Des arguments écologiques, expérimentaux et cliniques laissent supposer que ces troubles résultent, au moins en partie, de l’augmentation du nombre et de la concentration des perturbateurs endocriniens dans l’environnement et dans la nourriture. Ainsi, les xénoestrogènes comme le diéthylstilbestrol (DES), agissent sur les récepteurs des oestrogènes en provoquant des effets néfastes sur la fonction de reproduction masculine. Le but de ce travail a été d’évaluer l’effet postnatal du DES sur la fonction de reproduction chez la souris mâle. Pour pouvoir comprendre l’intervention des LXRs, nous avons choisi d’étudier cet effet chez les souris KO pour les deux isoformes de ces récepteurs nucléaires (lxrαβ-/-). Ce modèle doit nous permettre d’identifier si les effets délétères du DES sur le testicule passent par lxrαβ et d’identifier plus précisément les mécanismes mis en jeu. Nous avons pu montrer que le DES provoque la perturbation de la stéroïdogenèse en diminuant les transcrits de la plupart des gènes stéroïdogéniques (StAR, Cyp11A1, Cyp17a1). Les analyses histologiques montrent que le DES altère la balance prolifération/apoptose quel que soit le génotype, indiquant la perturbation des spermatogonies pré- et post-méiotiques. Nous avons pu montrer également que l’effet du DES sur le phénotype lxrαβ-/- est plus accentué, suggérant un effet protecteur des LXRs in vivo contre l’effet délétère du diéthylstilbestrol. / The mammalian testis has two major functions, sperm production, and synthesis of androgens. The maintenance and regulation of those two functions are under the control of endocrine and paracrine factors, but are also related to lipid homeostasis, including cholesterol. The nuclear oxysterol receptors (LXRs) are transcription factors belonging to the superfamily of nuclear receptors. The LXRs are expressed in the male genital tract and testis, and their ligands are active at physiological concentrations. In these organs, these receptors regulate cholesterol homeostasis, a precursor essential for the synthesis of testicular steroids. They also control the different steps of steroidogenesis by regulating the enzymes of steroidogenesis. In the end, their role in the balance proliferation / apoptosis of germ cells is prominent. In recent decades, there has been an increase in abnormal differentiation of the male genital tract (hypospadias, cryptorchidism) and testicular cancer, as well as a decrease in quantity and quality of sperm production. It was proposed that these abnormalities originate from a disturbance of testicular development during fetal life. Environmental, experimental and clinical arguments suggest that these disorders result, at least in part, to the increased number and concentration of endocrine disruptors in the environment and in food. Thus, xenoestrogens such as diethylstilbestrol (DES) act on the estrogen receptors, causing adverse effects on male reproductive function. The aim of this study was to assess the effect of DES on postnatal reproductive function in male mice. To understand the involvement of nuclear oxysterol receptors, we chose to study this effect in LXRαβ-null mice (lxrαβ-/-). This model should allow us to determine whether the deleterious effects of DES on testis go through lxrαβ and to identify more precisely the mechanisms involved. We have shown that DES causes disruption of steroidogenesis by decreasing transcripts of most steroidogenic genes (StAR, CYP11A1 and Cyp17a1). The histological analysis showed that DES alters the proliferation / apoptosis ratio whatever the genotype, indicating the disruption of pre-and post-meiotic spermatogonia. We have also shown that the effect of DES on the phenotype lxrαβ-/- is more pronounced, suggesting a protective effect of LXRs in vivo against the deleterious effect of diethylstilbestrol.

>Magister Scientiae - MSc / The blood-brain barrier (BBB) is an interface between the brain parenchyma and the circulating system. This barrier plays a vital role in protecting the CNS by restricting free paracellular diffusion of molecules from the systemic circulation. Methamphetamine (MA) is a highly addictive psychostimulant and has demonstrated neurotoxic properties as well as the ability to compromise the BBB. MA exposure is strongly linked with increased oxidative stress which can result in a decrease in the integrity of the BBB.The aim of this study was to investigate in vitro effects of pure and street MA "tik" on DNA proliferation and cell cycles in mouse brain endothelial (bEnd5) cells. Trypan blue was used to determine effects of MA (0.0001M-1mM) on cell viability and % cell growth. The Cell Titer Glo® luminescent assay and nonradioactive analogue, 5-bromo-2'-deoxyuridine (BrdU) was used to detect ATP and DNA levels, respectively. Cell cycles (propidium iodide incorporation) were analysed using flow cytometry. Statistical analysis was performed using Wilcoxin Rank Sum Test in which P<0.05 was denoted as significant. Results of this study showed that: 1. Viability of bEnd5 cells exposed to all selected concentrations of MA were unaffected when compared to controls (P>0.05). 2. % Cell growth was suppressed by MA exposure at 96hrs in comparison to that of controls (P≤0.03). 3. Cells exposed to MA had significant higher ATP concentrations than control cells at 96hrs (P ≤.0.03) 4. DNA synthesis was markedly suppressed in cells exposed to pure MA and street MA sample 4 (P≤0.03), while was similar and higher in cells exposed to street MA sample 1 (P=0.39), and street MA sample 2 and 3 (P≤0.04), respectively at 96hrs. 5. bEnd5 cell were arrested between 72 and 96hrs at the G1-S phase. In conclusion, this study demonstrated pure and illicit samples of MA obtained from forensic police did not affect the viability of bEnd5 cells, however resulted in the significant suppression of their cell numbers. This growth inhibition may be due to MA-induced cell cycle arrest at the G1-S phase. The study also showed that compounds found in the samples of street MA produced results significantly different to that of pure MA.

In many African countries, including South Africa, sorghum is malted for the brewing of traditional beer. In South Africa, most sorghum malting is by traditional outdoor floor malting, whereby the sorghum grain is steeped for about 8 hours, left outdoors to germinate in an uncontrolled environment. These malting conditions (wet grain and more or less ambient temperature) encourage microbial proliferation. Microorganisms may themselves negatively impact on the safety of the malts. Of more concern is the proliferation of fungi which can potentially produce highly poisonous mycotoxins in the sorghum malt. Microbial proliferation can also affect the quality of malt, and thereby resulting in undesirable malts. Therefore there is a need for efficient and safe ways to control microbial growth during sorghum malting. The aim of this research was to determine processes to produce sorghum malt that is free of unwanted yeasts, coliforms, moulds and mycotoxins. The first process investigated involved turning the grains during germination. The second process involved the addition of dilute sodium hydroxide (NaOH)/ caustic soda and calcium hydroxide [(Ca(OH)2]/lime during steeping and the third process was by the use of biological control methods which involved inoculation with microbial starter cultures. The effect of the three processes on the levels of moulds, coliforms, mycotoxins (aflatoxins, fumonisins, deoxynivalenol and zearalenone), cytotoxicity, expressed in terms of their IC50 (Inhibitory concentration resulting in 50% inhibition of the cleavage activity) and quality in terms of diastatic power (DP) of sorghum malt were investigated. Turning the sorghum grains during germination did not affect the microbial load of the malt. The total bacterial counts were at high levels of 107-109 cfu/g, fungi at 104-106 cfu/g and coliforms at 103-105 cfu/g. Turned and unturned grains produced malt which showed contamination by about 8 different mould species. Some of these moulds (Fusarium verticillioides, Phoma sorghina. Aspergillus flavus, Alternaria alternata and Penicillium spp.) are known to produce mycotoxins. Malt samples contained fumonisins, deoxynivalenol and zearalenone at levels of < 0.25-2 _g/g, 15-20 and 10-15 _g/kg, respectively. However, they all had very low cytotoxicity (IC50 from 31.2 to > 500 mg/kg). Turning had the negative effect of decreasing the DP of the sorghum malt. The reason that turning did not reduce the microbial load is probably due to the fact that the blending of malt as a result of turning ensured that bacteria and moulds were evenly distributed throughout the malt bed. Steeping sorghum grains in 0.2% NaOH reduced the level of microbial contamination in the malt. Coliforms and moulds were reduced from 104 and 105 cfu/g respectively, to levels of 102 cfu/g in the malt that do not pose health hazards. The high pH (10-13) that resulted from the addition of NaOH probably caused the inhibition of coliforms and moulds by distorting their cell membranes, destroying the proton gradient of the bacterium cell and thus leading to their death. Steeping in 0.2% NaOH resulted in malts with no detectable amounts of mycotoxins and no indication of cytotoxicity in the sorghum malt. A further advantage was that the DP of the 0.2% NaOH steeped malts was doubled. The addition of about 107-108 cfu/ml of Saccharomyces spp. and Pediococcus. pentosaceus cultures to steep water reduced moulds in the malt from 104 cfu/g to 102 cfu/g and coliforms from 104 cfu/g to 102 and <101 cfu/g, respectively. The antimicrobial activity of the Saccharomyces spp. appears to be mainly due to the competition with the other microorganisms. The antimicrobial activity of P. pentosaceus is mainly attributed to the low pH. In addition to the low pH, production of CO2, competition for nutrients and the production of antimicrobial activity could have been responsible for the overall antimicrobial activity of P. pentosaceus. Steeping with microbial cultures resulted in malts that contained no traces of mycotoxins and cytotoxicity. The DPs of the sorghum malts were not affected by steeping with microbial cultures. Turning of grains during germination is not a good method to control microbial load during sorghum malting. The addition of dilute NaOH in steeping water is proposed as a chemical method for the control of bacterial and fungal contamination during sorghum malting whereas the use of the Saccharomyces spp. and P. pentosaceus cultures offers a potential alternative as natural, biocontrol agents. However, dilute alkaline steeping is a more favoured method because it is an easier and practical method to put into operation. / Thesis (PhD (Food Sciences))--University of Pretoria, 2007. / Food Science / unrestricted