Neste trabalho estudamos essencialmente problemas relacionados aos conceitos de superfícies e curvas bi-harmônicas e de superfícies de ângulo constante. Caracterizamos as curva bi-harmônicas do grupo especial linear SL(2,R). Em particular, mostramos que todas as curvas bi-harmônicas de SL(2,R) são hélices e damos suas parametrizações explícitas como curvas do espaço pseudo-Euclidiano R42. Estudamos as superfícies biconservativas (as quais representam uma grande família que inclui as superfícies bi-harmônicas) nos espaços de Bianchi-Cartan-Vranceanu, obtendo a caracterização daquelas de ângulo constante e daquelas SO(2)-invariantes. Também, caracterizamos as superfícies de ângulo constante do espaço Euclidiano tridimensional que possuem aplicação de Gauss bi-harmônica, provando que são cilindros de Hopf sobre uma clotóide. Além disto, caracterizamos as superfícies de ângulo contante de SL(2,R). Mais especificamente, damos uma descrição local explícita para estas superfícies em termos de uma determinada curva de SL(2,R) e de uma família a um parâmetro de isometrias do espaço ambiente. / In this work we mainly study some problems related to the concept of biharmonic curves and surfaces and to surfaces of constant angle. We characterize the biharmonic curves in the special linear group SL(2,R). In particular, we show that all proper biharmonic curves in SL(2,R) are helices and we give their explicit parametrizations as curves in the pseudo-Euclidean space R42</sub. We study the biconservative surfaces (which represent a large family including the biharmonic surfaces) in the Bianchi-Cartan-Vranceanu spaces, obtaining the characterization of those with constant angle and of those which are SO(2)-invariant. Furthermore, we characterize the constant angle surfaces of the three-dimensional Euclidean space which have bi-harmonic Gauss map, proving that they are Hopf cylinders over a clothoid. Also, we characterize the constant angle surfaces of SL(2,R). In particular, we give an explicit local description of these surfaces by means of a suitable curve of SL(2,R) and a 1-parameter family of isometries of SL(2,R).

Neste trabalho foi realizado um grande levantamento de técnicas de esparsidade relacionadas a sistemas estáticos de energia elétrica. Tais técnicas visam, do ponto de vista computacional, ao aumento da eficiência na solução de rede elétrica objetivando, além da resolução em si, a redução dos requisitos de memória, armazenamento e tempo de processamento. Para tanto, uma extensa revisão bibliográfica foi compilada, apresentando um posicionamento histórico e uma ampla visão do desenvolvimento teórico. Os testes comparativos realizados para sistemas de 14, 30, 57 e 118 barras, sobre a implantação de três das técnicas mais empregadas, apontou a Bi-fatoração como tendo o melhor desempenho médio. Para sistemas pequenos, a Eliminação Esparsa e Sintética de Gauss apresentou melhores resultados. Este trabalho fornecerá subsídios conceituais e metodológicos a técnicos e pesquisadores da área. / In this work a great survey of sparsity techniques related to static systems of electric power was accomplished. Such techniques seek, for of the computational point of view, the increase of the efficiency in the solution of the electric net aiming, besides the resolution of itself, the reduction of memory requirements, the storage and time processing. For that, an extensive bibliographic review was compiled providing a historic positioning and a broad view of theoretic development. The comparative tests accomplished for systems of 14,30, 57 and 118 buses, on the implementation of three of the most employed techniques, it pointed out an bi-factorisation as best medium performance. For small systems, the sparse symmetric Gaussian elimination showed the best results. This work will supply conceptual and methodological subsidies to technicians and researchers of the area.

Neste trabalho apresentamos uma descrição geométrica do grupo de tranças no disco Bpnq e sua apresentação em termos de geradores e relatores no famoso teorema da apresentação de Artin. Mostraremos também que o grupo de tranças puras PBpnq, grupo que possui a permutação trivial das cordas, é bi-ordenável, ou seja, exibiremos uma ordenação para PBpnq que será invariante pela multiplicação em ambos os lados. Esse processo é dado a partir da combinação da técnica de pentear Artin e a expansão Magnus para grupos livres. / In this work, we present a geometric description of the braids groups of the disk Bpnq and its presentation in terms of generators and relations in the famous theorem of Artin\'s presentation. We also show that groups of pure braids, denoted by PBpnq, groups that have the trivial permutation of the strings, are bi-orderable, that is, we will present the explicit construction of a strict total ordering of pure braids PBpnq which is invariant under multiplying on both sides. This process is given from the combination of the techniques of combing Artin and Magnus expansion to free groups.

Made available in DSpace on 2017-07-21T14:54:08Z (GMT). No. of bitstreams: 1 Lilian Cristina Amaral Martines.pdf: 1866867 bytes, checksum: 1077f1ac7728e9fb521dc8861b193151 (MD5) Previous issue date: 2014-06-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Currently in Brazil, according to Maher (2013), are spoken by around 222 indigenous languages. However, although this number represent a major linguistic diversity, "It is also estimated that since the arrival of the Portuguese there was the loss of 1,000 languages, representing 85% of the languages in Brazilian territory in the sixteenth century" (RODRIGUES, 2005), result of "an extremely violent and ongoing colonization process" (Rodrigues, 2005), the indigenous peoples were submitted. When the establishments of formal education, learning models were quite radical and mostly aimed at monolingual teaching in Portuguese, which since the Pombal reform was imposed as the most prestigious language throughout the national territory. Concerning this, in order to conduct a search that values and contribute to the work on Brazilian minority languages in the school context, this research aims to analyze the initiative of the language policy of officialisation the Guarani language, in Tacuru city in the state of Mato Grosso do Sul, trying to highlight, from the point of view of the school community, what the political and pedagogical implications of this initiative in the school studied. As theoretical perspectives to research is based on authors like Altenhofen (2004), Calvet (2007, 2002), Hamel (1988), Moserrat (2001, 2006), Oliveira (2003, 2005, 2009) and Tobias (2008), which supported our discussions on Linguistics policies in multilingual contexts. We used authors as Benites (2009), Cavalcanti (1999), Luciano (2006), Maher (2010), Miller (2003); Seki (1993); among others in order to support the discussions directly related to contexts in which indigenous communities are inserted. Regarding the methodology, this study was developed through methodological principles of qualitative perspective, understanding that we are dealing with sensitive issues that involve value judgments. We used also in qualitative perspective, the research mode of ethnographic to be working directly with students and teachers. This methodological choice, in turn, aims to support the work of observation and description of the cultural and linguistic aspects of these participants, so that a greater knowledge of the culture of the participants involved is essential for the research could bring contribution to its participants. The results obtained in this research suggest that: a) the Guarani language was implemented at School X in foreign language format, with a team of two professors who taught the language, both in the morning and in the evening; b) lack dialogue with members of the School X, regarding the implementation of the law, because according to participants the law "come from above"; c) lack Linguistic preparation of teachers and teaching materials to work with discipline Guarani language; d) it is designed little workload to Guarani language discipline; e) the school does not have a multidisciplinary team and teachers who work properly the issue of indigenous culture and diversity; f) except for the hospital, which has an interpreter to meet the indigenous population, according to the speech of participants, no major advances in the appreciation of indigenous culture in the municipality of Tacuru observed. / Atualmente, no Brasil, segundo Maher (2013), são faladas por volta de 222 línguas indígenas. No entanto, apesar de esse número representar uma grande diversidade linguística, “estima-se também que desde a chegada dos portugueses houve a perda de 1.000 línguas, o que representa 85% das línguas existentes no território brasileiro no século XVI” (RODRIGUES, 2005), resultado “de um processo colonizador extremamente violento e continuado” (RODRIGUES, 2005), a que os povos indígenas foram submetidos. Quando do estabelecimento do ensino formal, os modelos de aprendizagem eram bastante radicais e em sua maioria visavam ao ensino monolíngue em língua portuguesa, que desde a reforma pombalina foi imposta como a língua de maior prestígio em todo território nacional. Concernente a isso, a fim de realizar uma pesquisa que valorize e contribua com o trabalho sobre línguas minoritárias brasileiras no contexto escolar, essa pesquisa tem como objetivo analisar a iniciativa da política linguística de cooficialização da língua guarani, na cidade de Tacuru, no estado do Mato Grosso do Sul, a partir do ponto de vista da comunidade escolar, quais as repercussões políticas e pedagógicas dessa iniciativa na escola pesquisada. Como perspectivas teóricas a pesquisa está fundamentada em autores como Altenhofen (2004), Calvet (2007, 2002), Hamel (1988), Moserrat (2001, 2006), Oliveira (2003, 2005, 2009) e Tobias (2008), que subsidiaram nossas discussões relativas às políticas Linguísticas em contextos multilíngues. Utilizamos autores como Benites (2009), Cavalcanti (1999), Luciano (2006), Maher (2010), Monteiro (2003); Seki (1993); dentre outros, para amparar as discussões diretamente relacionadas a contextos em que as comunidades indígenas estão inseridas. Quanto à metodologia, esta pesquisa foi desenvolvida através dos princípios metodológicos da perspectiva qualitativa, por entender que estamos lidando com questões delicadas, que envolvem juízo de valor. Utilizamos, também, dentro da perspectiva qualitativa, a modalidade de pesquisa de cunho etnográfico, por estarmos trabalhando diretamente com alunos e professores. Essa escolha metodológica, por sua vez, objetiva subsidiar o trabalho de observação e descrição dos aspectos culturais e linguísticos desses participantes, de forma que um maior conhecimento da cultura dos participantes envolvidos é fundamental para que a pesquisa pudesse trazer contribuição para seus participantes. Os resultados obtidos na pesquisa sugerem que: a) a língua guarani foi implantada na Escola X, no formato de língua estrangeira, com a lotação de dois professores que lecionavam essa língua, tanto no período matutino como no vespertino; b) falta diálogo com os integrantes da Escola X, quanto à implementação da lei, pois segundo os participantes a lei “veio de cima para baixo; c) falta de preparo linguístico dos professores e material didático para o trabalho com disciplina língua guarani; d) pouca carga horária à disciplina de língua guarani; e) a escola não possui uma equipe multidisciplinar e professores que trabalhem adequadamente a questão da cultura indígena e da diversidade; f) com exceção do hospital, que possui um intérprete para atender a população indígena, de acordo com a fala dos participantes, não se observou maiores avanços quanto à valorização da cultura indígena no município de Tacuru.

Dans un environnement en constant changement, les fonctions exécutives (FRE) nous permettent d'organiser l'information en provenance de sources multiples, de s'adapter à des situations sociales complexes et d'inhiber les comportements inappropriés. Les recherches sur le fonctionnement exécutif ont été initiées en neuropsychologie, après avoir observé chez des patients frontaux, des difficultés à organiser leurs comportements quotidiens sans pour autant présenter de difficultés de langage ou de mémoire. Un grand nombre de tests neuropsychologiques sont disponibles afin d'évaluer les FE. Cependant, ces tests sont souvent critiqués pour leur complexité et leur manque de validité de construction. Le champ des FE manque en réalité de modèles théoriques précis qui permettraient de décrire ces fonctions et leurs potentielles interactions pour le contrôle des comportements complexes. En conséquence, les tâches sont souvent construites de manière intuitive, dans le présent travail de thèse, après revue d'un état de l'art sur les FE (Ch1), je propose une nouvelle tâche, le spatial-tapping, qui pourrait être utilisée en remplacement des tâches classiques complexes (Ch2). Je promeus également le potentiel de cette tâche à être utilisée dans des contextes cliniques (Ch3). Je présente finalement comment les analyses réalisées pour le spatial-tapping afin d'étudier les FE peuvent être transférées à des situations motrices plus complexes, comme la coordination bi-manuelle (Ch4). En conclusion, les résultats présentés dans ce travail de thèse sont en faveur de l'idée selon laquelle notre organisation mentale reflète la manière dont on organise nos mouvements. / In a constant changing environment, executive abilities allow us to organize sensory information of multiple sources and to adapt to diverse stuations while at the same time inhibiting inappropriate behaviors. research on the executive functions (EFS) have historical roots on neuropsychology, with the description of frontal patients that were showing disruptions in organizing their daily behaviors independently of any impairment in memory, language or general intelligence. A wide range of neuropsychological tools is used today to evaluate executive abilities : tower of London for planning, go-no-go for inhibition, etc. However, the classical tasks often present methodological limitations and they lack of correpondence between process and behavior. Furthermore, the field lacks of a compelling theory that make links between the EFS themselves. The present PHD work was an attempt to propose a novel task to assess the EFS in the place of the classical batteries of neuropsychological tasks. After offering an overview of the EF literature and presenting simple motor tasks that seem to target similar EFS than those described in neuropsychology (Ch1), I present the spatial-tapping task as a challenging paradigm to understand the relationships between the different EFS (Ch2), and its potential to be used in clinical settings (Ch3). The I present how a similar approach can be used to investigate how EFS intervenes in the control of more complex motor sequences, E.G. bi-manual tasks (Ch4). Overall, the results presented here support an emboided perspective of cognition with mental organization reflecting the way one plans motor sequences for adaptive behavior.

The goal of this thesis is to create a comprehensive overview of how the economic crisis influenced the business intelligence market. The introduction is dedicated to the general principles of the business intelligence technologies. It is followed by analysis and identification of the commercial sector's problems associated with the recent economic decline as well as shortcomings that the corporate executives commit in the times of economic growth, and a proposal of solutions to these problems using Business Intelligence applications. The next part of the work is focused on the global analysis of benefits of the solutions and their future development. The final part of the thesis serves as an argument to highlight the importance of BI and is demonstrated on several examples of successful BI implementations in various businesses operating in different sectors. The thesis aims not only to analyze and document the development and changes in the understanding of Business Intelligence during the economic crisis but it should also motivate potential readers from among the management to consider whether they should also support the acquisition of BI in their businesses. This document should prove that if they invest in Business Intelligence in times of crisis then they might not need to implement unpopular solutions to their problems. The relevance of this subject is only underscored by the fact that unless the development of the world economy improves its current course, we might find ourselves at the beginning of another, perhaps even more significant crisis. The appendix summarizes the BI applications' inputs, different processing and information analysis methods, and the possibility of using their outputs to improve the operation of the enterprise.

A cana-de-açúcar é uma das principais culturas agrícolas no cenário econômico e social brasileiro. Na cultura de cana-de-açúcar o estresse hídrico é o principal fator limitante para o aumento de produtividade, sendo responsável por alterações fisiológicas, bioquímicas e moleculares nas plantas, que podem deflagrar perturbações metabólicas que ativam a morte celular programada (MCP). Sabendo-se que o gene BI-1 apresenta o potencial de reduzir os efeitos da MCP desencadeado por estresses bióticos e abióticos em plantas, este trabalho teve como objetivo analisar plantas transgênicas de cana-de-açúcar que expressam o gene BI-1 de Arabidopsis thaliana (AtBI-1) em condições de estresse hídrico. Também, plantas transgênicas e controle foram inoculadas com o fungo Puccinia melanocephala demonstrando que o processo de transformação genética com o gene AtBI-1 alterou as características pré existentes de resistência a ferrugem marrom nas plantas transgênicas. Os estudos de tolerância ao défict hídrico foram realizados em dois experimentos, o experimento 1 com plantas transgênicas e controles de 90 dias e o experimento 2 com plantas de 60 dias. Plantas do experimento 1 foram analisadas quanto características morfológicas como número de estômatos e tricomas, altura e circunferência do colmo e após ficarem 24 dias sem água foram analisadas quanto a taxa fotossintética, comportamento estomático e conteúdo relativo de água nas folhas, enquanto no experimento 2 as plantas foram analisadas quanto aos teores de prolina, atividades das enzimas guaiacol peroxidase (GPOX), ascorbato peroxidase (APX) e catalase (CAT) após as plantas ficarem 17 dias sob déficit hídrico. Estas enzimas estão envolvidas em processos de desativação de elementos ativos de oxigênio. Os resultados demonstraram que as plantas transgênicas expressando o gene AtBI-1 possuem fenótipo de menor altura, e maior taxa fotossintética, maior comportamento estomático e maior conteúdo relativo de água nas folhas, e assim apresentam maior tolerância ao déficit hídrico que plantas controle. Contudo, houve baixo acúmulo de prolina, baixa atividade da GPOX, APX e CAT nas plantas transgênicas durante o estresse hídrico comparada com as plantas controle do mesmo tratamento. Porém foi observado alta atividade constitutiva da catalase nas plantas transgênicas. A atividade da catalase nestas plantas transgênicas sugere a possibilidade da interação entre AtBI-1 e calmudolinas. Futuros estudos podem contribuir para elucidar se a proteína BI-1 é essencial para a ativação das catalases por calmudolinas. / Sugarcane is one of the main agricultural crops in the Brazilian social and economic scenario. Water stress in the culture of sugarcane is the main limiting factor for increasing productivity accounting for physiological, biochemical and molecular plants that can trigger metabolic disturbances activating programmed cell death (MCP). Knowing that the BI-1 gene has the potential to reduce the effects of MCP triggered by biotic and abiotic stresses in plants, this study aimed to analyze transgenic sugarcane that express the BI-1 gene of Arabidopsis thaliana (AtBI-1) under water stress. Also, transgenic and control plants were inoculated with Puccinia melanocephala fungus demonstrating that the genetic transformation process with the AtBI-1 gene altered the pre-existing characteristics of brown rust resistance in transgenic plants. Studies of tolerance to water deficit were performed in two experiments, the experiment 1 was prepared with transgenic and control plants with 90 days and the experiment 2 used plants with 60 days. Plants from experiment 1 were analyzed as for morphological characteristics such as number of stomata and trichomes, height and diameter of stem after plants being under water for 24 days as were analyzed photosynthetic rate, stomatal behavior, relative water content in leaves while in the experiment 2, plants were analyzed for the levels of proline, enzyme activities of guaiacol peroxidase (GPOX), ascorbate peroxidase (APX) and catalase (CAT) under water deficit for 17 days. These enzymes are involved in deactivation of active elements oxygen. The results demonstrated that the transgenic plants expressing the AtBI-1 gene presented the phenotype of lower height, higher index of leaf area, higher photosynthetic rate, higher stomatal behavior and higher relative water content in leaves than control plants increasing tolerance to drought stress. However, there were low levels of proline, low activity of GPOX activity, APX and CAT in transgenic plants during drought stress compared to control plants of the same treatment, but the observed high constitutive activity of catalase in transgenic plants. Catalase activity in these transgenic plants suggests the possibility of interaction between AtBI-1 and calmudolinas. Future studies may contribute to understand whether the BI-1protein is essential for the activation of catalase by calmudolinas.

Effects of Nb2O5 addition on the formation and properties of the Bi-based superconductors were studied. The superconducting samples were synthesized by two different methods, the solid state reaction (SSR) and ammonium nitrate melt route (ANM) to obtain information about the growth techniques. Ten samples (five with each method) with the chemical compositions of Bi1.6Pb0.4Sr2Ca2Cu3NbxOy, with x= 0.00, 0.05, 0.10, 0.20, and 0.30 were prepared. Phase identification, structural and microstructural analysis were carried out using powder X-ray diffraction method, scanning electron microscopy and energy dispersive X-ray (EDX) analysis. The transition temperature and the critical current measurements were carried out using the electromagnetic measurement system. The critical parameters of the samples were also determined by AC susceptibility and magnetization measurements. Improvements in the formation of the Bi-2223 phase with Nb addition have been observed by both methods. The ANM method leads mixtures of Bi-2223 and Bi-2212 phases, but with the SSR method pure Bi-2223 phase was obtained. With small amounts of Nb addition the critical temperature, Tc, remains the same for ANM samples and it increases for the SSR samples. For both series of samples Tc decreases with further increase of Nb content. With Nb addition the critical currents of the ANM sample almost remain the same and those of the SSR samples increases. Observations based on AC susceptibility measurements showed that Nb addition improve inter-grain coupling. Inductive critical current densities obtained from magnetization measurements agree with the critical currents stated above and show that Jc increase with increase Nb content.

Wood pellets are offering opportunities for a cleaner-burning biofuel but major concerns are overshadowing their potential. Tony Bi and UBC’s Clean Energy Research Centre are engineering solutions.

Résumé L’approvisionnement en cholestérol est un facteur limitant la stéroïdogenèse ovarienne. Pour cette raison, la majorité du cholestérol requis pour la synthèse des stéroïdes est importé de la circulation via les récepteurs des lipoprotéines de haute (HDL) et de basse densité (LDL) nommés scavenger receptor (SR-BI) et low-density lipoprotein receptor (LDLr). L’ARN messager de SR-BI est exprimé dans les ovaires de porcs durant toutes les étapes de la folliculogenèse ainsi que dans le corps jaune (CL). L’expression de la protéine SR-BI a également été détectée dans les follicules de souris lors du cycle œstral. Chez les deux espèces, l’expression est concentrée dans le cytoplasme et en périphérie des cellules du follicule. Les gonadotrophines induisent l'expression de SR-BI dans les cellules de la granulosa porcines, avec une expression cytoplasmique qui augmente durant la période périovulatoire, et avec une migration aux périphéries cellulaires durant la maturation du CL. Une conformation de 82 kDa de SR-BI est fortement exprimée dans le CL porcin, avec une conformation moins abondante de 57 kDa. Les différences entre les conformations sont attribuables à la glycosylation. La culture in vitro de follicules porcins avec des gonatrophines chorioniques humaines (hCG) a induit une hausse de régulation dépendante du temps du SR-BI de 82 kDa dans les cellules du granulosa. SR-BI et LDLr ont été exprimés réciproquement, avec LDLr étant le plus élévé dans les cellules folliculaires du granulosa et diminuant précipitamment avec la formation du CL. Pour explorer plus en détail les mécanismes d’approvisionnement en cholestérol de la stéroïdogenèse ovarienne, nous avons examiné des souris soumis à un traitement de désaccouplement de l'ovulation, et des souris portant la mutation nulle du gène Scarb1 (SR-BI-/-). Les résultats ont démontré que des ovocytes enfermés dans des structures lutéinisées expriment SR-BI. Les souris SR-BI-/ - présentaient de petits CLs, et de large follicules avec des cellules de thèque hypertrophiées et des kystes folliculaires avec des cavités remplies de sang et une diminution de 50% du niveau de progestérone dans le sérum. Les souris SR-BI-/ - traitées avec une combinaison de 20 g / g de mevinoline et 100  g / g de chloroquine ont démontré une diminution de 43% du niveau de progestérone sérique chez le type sauvage et de 30% chez les souris SR-BI-/ -. L’expression protéique de l’enzyme limitant pour la synthèse du cholestérol, 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), a augmenté chez les souris SR-BI-/-. Nous avons présenté des preuves démontrant que les cellules des follicules expriment le SR-BI durant la stéroïdogenèse et que la lutéinisation augmente l’expression de SR-BI. La maturation post-transcriptionelle est caractérisée par la glycosylation. Sous des conditions normales, l’expression de LDLr est arrêtée durant la lutéinisation. Ainsi SR-BI devient le facteur principal pour l’importation du cholestérol extracellulaire. En plus, la perturbation extracellulaire du cholestérol synthétisé de novo et l’absorption par les LDLr chez les souris SR-BI-/- diminuent la fonction lutéal. L’homéostasie du cholestérol ovarien est très importante pour une lutéinisation adéquate et sa perturbation mène à une réduction, mais non à un blocage complet, de la fonction lutéal. En conclusion, l’expression de SR-BI est un facteur important, mais non essentiel, pour maintenir l’homéostasie du cholestérol ovarien et la synthèse des stéroïdes, et la lutéinisation. Un réseau de mécanismes complémentaires et compensatoires d’approvisionnement en cholestérol agit en concert pour assurer la synthèse des stéroïdes ovariens. / Abstract Ovarian cholesterol supply is rate limiting to ovarian steroidogenesis. For this reason, the majority of cholesterol required for steroid synthesis is imported via scavenger receptor-BI (SR-BI) and the low-density lipoprotein (LDL) receptor from circulating HDL and LDL. SR-BI mRNA is expressed in pig ovaries at all stages of folliculogenesis and in the corpus luteum (CL). SR-BI protein expression in mouse ovary during estrous cycle was also detected. In both species, expression is concentrated in cytoplasm and periphery of follicular cells. Gonadotropins induce SR-BI expression in pig granulosa cells, with cytoplasmic expression increasing through the periovulatory period, with migration to the cell periphery as the CL matured. An 82-kDa form of SR-BI is strongly expressed in the pig CL, with the less abundant 57-kDa form, differences between forms are attributable to glycosylation. In vitro culture of pig follicles with human chorionic gonadotropin (hCG) induced time-dependent upregulation of 82-kDa SR-BI in granulosa cells. SR-BI and LDL receptor were reciprocally expressed, with the latter highest in follicular granulosa cells, declining precipitously with CL formation. To further explore mechanisms of cholesterol supply to ovarian steroidogenesis, we examined mice treated to uncouple ovulation and mice bearing null mutation of the Scarb1 gene (SR-BI-/-). Results show entrapped oocytes in luteinized structures expressed SR-BI. SR-BI-/- mice displayed small corpora lutea, large follicles with theca cells hypertrophied, follicular cysts with blood filled cavities and 50% decreased in plasma progesterone. In SR-BI-/- mice, treatment with a combination of 20 g/g of mevinolin and 100 g/g of chloroquine (CHLORO) was employed to disturbed cholesterol sources. Serum progesterone was reduced by 43% in wild type and 30% in SR-BI-/- mice. The protein expression of the rate-limiting enzyme for cholesterol synthesis, 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR) increased in SR-BI-/- mice. It was concluded that follicular cells express SR-BI during follicle development and luteinization causes upregulation of SR-BI expression. Posttranslational maturation is characterized by glycosylation. Under normal conditions expression of the LDLr (low density lipoprotein recepors) is extinguished during luteinization such that SR-BI becomes the principal means of importation of extracellular cholesterol. Further, perturbation of cholesterol de novo synthesis and uptake from LDLr in SR-BI-/- mice leads to a reduction of luteal function. Ovarian cholesterol homeostasis is central to adequate luteinization, and its perturbation leads to reduction, but not to complete impairment, of luteal function. We conclude that SR-BI expression is an important but not essential factor in maintaining ovarian cholesterol homeostasis, steroid synthesis and luteinization. A network of complementary and compensatory cholesterol supply mechanisms act in concert to assure ovarian steroid synthesis. / Studies were funded by Colegio de Postgraduados, México. CONACyT, México. SRE, México. Ministère de l’Éducation du Québec, University of Montreal and an Operating Grant to B.D. Murphy from the Canadian Institutes of Health Research.