909 resultados para mitochondrial DNA marker
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Endonuclease G (EndoG) is a well conserved mitochondrial nuclease with dual lethal and vital roles in the cell. It non-specifically cleaves endogenous DNA following apoptosis induction, but is also active in non-apoptotic cells for mitochondrial DNA (mtDNA) replication and may also be important for replication, repair and recombination of genomic DNA. The aim of our study was to examine whether EndoG exerts similar activities on exogenous DNA substrates such as plasmid DNA (pDNA) and viral DNA vectors, considering their importance in gene therapy applications. The effects of EndoG knockdown on pDNA stability and levels of encoded reporter gene expression were evaluated in the cervical carcinoma HeLa cells. Transfection of pDNA vectors encoding short-hairpin RNAs (shRNAs) reduced levels of EndoG mRNA and nuclease activity in HeLa cells. In physiological circumstances, EndoG knockdown did not have an effect on the stability of pDNA or the levels of encoded transgene expression as measured over a four day time-course. However, when endogenous expression of EndoG was induced by an extrinsic stimulus (a cationic liposome transfection reagent), targeting of EndoG by shRNA improved the perceived stability and transgene expression of pDNA vectors. Therefore, EndoG is not a mediator of exogenous DNA clearance, but in non-physiological circumstances it may non-specifically cleave intracellular DNA regardless of its origin. To investigate possible effects of EndoG on viral DNA vectors, we constructed and evaluated AdsiEndoG, a first generation adenovirus (Ad5 ΔE1) vector encoding a shRNA directed against EndoG mRNA, along with appropriate Ad5 ΔE1 controls. Infection of HeLa cells with AdsiEndoG at a multiplicity of infection (MOI) of 10 p.f.u./cell resulted in an early cell proliferation defect, absent from cells infected at equivalent MOI with control Ad5 ΔE1 vectors. Replication of Ad5 ΔE1 DNA was detected for all vectors, but AdsiEndoG DNA accumulated to levels that were 50 fold higher than initially, four days after infection, compared to 14 fold for the next highest control Ad5 ΔE1 vector. Deregulation of the cell cycle by EndoG depletion, which is characterized by an accumulation of cells in the G2/M transition, is the most likely reason for the observed cell proliferation defect. The enhanced replication of AdsiEndoG is consistent with this conclusion, as Ad5 ΔE1 DNA replication is intimately related to cell cycling and prolongation or delay in G2/M greatly enhances this process. Furthermore, infection of HeLa with AdsiEndoG at MOI of 50 p.f.u./cell resulted in an almost complete disappearance of viable, adherent tumour cells from culture, whereas almost a third of the cells were still adherent after infection with control Ad5 ΔE1 vectors, relative to the non-infected control. Therefore, targeting of EndoG by RNAi is a viable strategy for improving the oncolytic properties of first generation adenovirus vectors. In addition, AdsiEndoG-mediated knockdown of EndoG reduced homologous recombination between pDNA substrates in HeLa cells. The effect was modest but, nevertheless demonstrated that the proposed role of EndoG in homologous recombination of cellular DNA also extends to exogenous DNA substrates.
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La nature a développé diverses stratégies afin d’assurer le commencement de la vie dans des conditions d’homoplasmie, c’est-à-dire des conditions telles que les cellules sont dotées du même ADN mitochondrial. Toutefois, des nouveaux haplotypes de l’acide désoxyribonucléique mitochondrial (ADNmt) peuvent apparaitre et croître de plusieurs façons tout au long de la durée d’une vie menant à l’hétéroplasmie. Par exemple, l’hétéroplasmie de l’ADNmt peut être créée artificiellement par des technologies reproductives assistées, ainsi que naturellement par le processus de vieillissement. De ce fait, la thèse de ce doctorat fut divisée en deux principaux objectifs. Le premier étant celui d’analyser les changements survenus dans l’hétéroplasmie de l’ADNmt produit par le transfert nucléaire des cellules somatiques (SCNT) lors du développement de l’embryon jusqu’au fœtus et aux tissus adultes de bovins clonés. En ce qui concerne le second objectif, il s’agit d’analyser les changements survenus dans l’hétéroplasmie de l’ADNmt causés par le vieillissement dans une cellule somatique adulte et dans des tissus germinaux durant l’ovogénèse, ainsi qu’au début de l’embryogenèse et dans la procédure de culture in vitro sur des souris. Dans la première série d’expériences sur des bovins, des fibroblastes fœtaux transportant une mutation d’ADNmt (insertion de 66 pb) furent fusionnés avec des ovocytes receveurs transportant l’ADNmt du type sauvage. La présence d’ADNmt venant de la cellule donneuse a été analysée à différents stades de développement, soit sur des embryons âgés de 17 jours (n=17), des fœtus âgés de 40 jours (n=3), des fœtus âgés de 60 jours (n=3), un fœtus âgé de 240 jours et 3 clones post-nataux âgés de 18 à 24 mois. Chaque individu s’est avéré être hétéroplasmique et 99 % (103/104) des échantillons de tissus analysés étaient également hétéroplasmiques. Cependant, l’ovaire venant du fœtus de 240 jours fut le seul à être homoplasmique pour l’ADNmt de l’ovocyte receveur. Dans la plupart des échantillons analysés (95,2 %, soit 99/104) la moyenne d’hétéroplasmie était de 1,46 %. Par contre, un fœtus âgé de 40 jours a présenté un niveau élevé d’hétéroplasmie (20,9 %), indiquant ainsi que des évènements rares d’augmentation de l’ADNmt des cellules donneuses peuvent survenir. Étant donné que la majorité des clones SCNT montrait de l’hétéroplasmie de l’ADNmt à des proportions comparables à celles des cellules donneuses au moment de la reconstruction de l’embryon, on a pu conclure que l’hétéroplasmie produite par des techniques de transfert nucléaire utilisant des cellules somatiques est due à une ségrégation neutre de l’ADNmt. Dans la seconde série d’expériences sur des souris, des femelles de différents âges, c.à.d. jeunes (0 – 8 mois), moyennes (8 – 16 mois) et vieilles (16 – 24 mois), ont été synchronisées (gonadotrophines) et sacrifiées dans le but d’obtenir des ovocytes au stade de vésicule germinal, et des ovocytes au stade métaphase-II produits in vivo et in vitro. De plus, des embryons in vivo et in vitro au stade de deux-cellules et des embryons au stade de blastocystes ont été obtenus de femelles jeunes. Différents tissus somatiques, venant de femelles des trois stades d’âge ont été obtenus : cerveau, foie, muscle et du cumulus ovocytaire. De plus, l’effet du vieillissement a été mesuré selon la fertilité de la femelle. En effet, les effets sur l’hétéroplasmie du vieillissement, du stade de développement et de la culture in vitro ont été mesurés dans des ovocytes et dans des embryons. Les effets du vieillissement sur les mitochondries ont été mesurés par rapport au nombre total de copies de l’ADNmt, au pourcentage des délétions communes et sur l’expression de trois gènes : Ndufs4, Mt-nd2 and Mt-nd4. Il a été possible d’observer que la fertilité des femelles dans la colonie de souris diminuait avec l’âge. En fait, le vieillissement affectait l’ADNmt dans les tissus somatiques, cependant il n’avait pas d’effet sur le cumulus, les ovocytes et les embryons. Le nombre de délétions de l’ADNmt augmentait pendant la reprise de la méiose et celui-ci diminuait au début du développement embryonnaire. La culture in vitro n’affectait pas la quantité d’ADNmt dans la plupart des tissus germinaux. Puisque nous n’avons pas trouvé d’effet de l’âge dans la majorité des paramètres mitochondriaux analysés dans les ovocytes et les embryons, il est suggéré que la délétion commune de l’ADNmt dans les tissus germinaux est davantage reliée au statut cellulaire de la production d’énergie qu’au processus de vieillissement. Deux sources différentes de mutations de l’ADNmt produites dans les ovocytes normaux ou reconstitués ont produit différents résultats d’hétéroplasmie au début de l’embryogénèse. Chez les bovins, l’hétéroplasmie artificielle impliquant une petite insertion (66 pb) dans la région non codante (D-loop) de l’ADNmt a été vraisemblablement non nocive pour l’embryon, tolérant la persistance de l’ADNmt étranger pendant les différents stades du développement des clones. Chez les souris, l’hétéroplasmie naturelle produite par une grande délétion (4974 pb délétion commune) dans la région codante de l’ADNmt a été vraisemblablement nocive pour l’embryon et par conséquent éliminée pour assurer l’homoplasmie au début du développement embryonnaire.
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La Fibrosis Quística es la enfermedad autosómica recesiva mas frecuente en caucásicos. En Colombia no se conoce la incidencia de la enfermedad, pero investigaciones del grupo de la Universidad del Rosario indican que podría ser relativamente alta. Objetivo: Determinar la incidencia de afectados por Fibrosis Quística en una muestra de recién nacidos de la ciudad de Bogotá. Metodología: Se analizan 8.297 muestras de sangre de cordón umbilical y se comparan tres protocolos de tamizaje neonatal: TIR/TIR, TIR/DNA y TIR/DNA/TIR. Resultados: El presente trabajo muestra una incidencia de 1 en 8.297 afectados en la muestra analizada. Conclusiones: Dada la relativamente alta incidencia demostrada en Bogotá, se justifica la implementación de Tamizaje Neonatal para Fibrosis Quística en Colombia.
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Las reacciones alérgicas a medicamentos cutáneas severas (RAM) como el Síndrome Stevens Johnson (SJS) y la Necrólisis Epidérmica Tóxica (NET),caracterizadas por exantema, erosión de la piel y las membranas mucosas, flictenas, desprendimiento de la piel secundario a la muerte de queratinocitos y compromiso ocular. Son infrecuentes en la población pero con elevada morbi-mortalidad, se presentan luego de la administración de diferentes fármacos. En Asia se ha asociado el alelo HLA-B*15:02 como marcador genético para SJS. En Colombia no hay datos de la incidencia de estas RAM, ni de la relación con medicamentos específicos o potenciales y tampoco estudios de aproximación genómica de genes de susceptibilidad.
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Tuna species of the genus Thunnus, such as the bluefin tunas, are some of the most important and yet most endangered trade fish in the world. Identification of these species in traded forms, however, may be difficult depending on the presentation of the products, which may hamper conservation efforts on trade control. In this paper, we validated a genetic methodology that can fully distinguish between the eight Thunnus species from any kind of processed tissue. Methodology: After testing several genetic markers, a complete discrimination of the eight tuna species was achieved using Forensically Informative Nucleotide Sequencing based primarily on the sequence variability of the hypervariable genetic marker mitochondrial DNA control region (mtDNA CR), followed, in some specific cases, by a second validation by a nuclear marker rDNA first internal transcribed spacer (ITS1). This methodology was able to distinguish all tuna species, including those belonging to the subgenus Neothunnus that are very closely related, and in consequence can not be differentiated with other genetic markers of lower variability. This methodology also took into consideration the presence of introgression that has been reported in past studies between T. thynnus, T. orientalis and T. alalunga. Finally, we applied the methodology to cross-check the species identity of 26 processed tuna samples. Conclusions: Using the combination of two genetic markers, one mitochondrial and another nuclear, allows a full discrimination between all eight tuna species. Unexpectedly, the genetic marker traditionally used for DNA barcoding, cytochrome oxidase 1, could not differentiate all species, thus its use as a genetic marker for tuna species identification is questioned
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Aquest treball es centra en el coneixement de l'estructura poblacional de tres espècies piscícoles de la família Scombridae, el bonítol (Sarda sarda), la bacora (Thunnus alalunga) i la tonyina (Thunnus thynnus) en la seva distribució de l'atlàntic i el mediterrani.
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Les anàlisis realitzades en cent deu poblacions de truita comuna (Salmo trutta) que abarquen el seu rang natural de distribució indiquen que el patró filogenètic es relaciona amb les tres grans vessants on es troba distribuïda l'espècie: ponto-càspia, atlàntica i mediterrània. Aquesta diferenciació estaria associada a l'aïllament de les vessants durant el Quaternari. L'origen de l'espècie es relaciona amb la vessant ponto-càspia, d'acord amb els models biogeogràfics que postulen l'origen asiàtic de la ictiofauna europea. S'ha detectat també un segon nivell de divergència dins de cada vessant que dóna com a resultat l'existència de sis llinatges evolutius: Atlàntic i Duero a la vessant atlàntica, els llinatges Adriàtic, Mediterrani i Marmoratus als rius mediterranis, i el llinatge Danubi a la zona ponto-càspia. Les glaciacions del Pleistocè han modificat profundament el rang de distribució de la truita comuna, especialment a la vessant atlàntica, on s'han proposat quatre grans refugis glacials: a l'est de la capa de gel, a Europa central, a l'entorn del canal de la Mànega i a l'entorn del golf de Biscaia; tot i que només els tres primers haurien participat en la recolonització del nord d'Europa al final de l'última glaciació. El quart refugi, que inclou el sud de França i el Cantàbric hauria estat l'origen de l'expansió cap al sud durant el Pleistocè Superior d'un grup de poblacions distribuïdes actualment a la vessant atlàntica ibèrica, i també hauria servit de base per a l'expansió cap al nord d'altres grups de truita durant interglacials anteriors. A la vessant atlàntica de la peninsula Ibèrica, l'estructura poblacional es troba associada a la xarxa hidrogràfica i es determinen fins a cinc unitats poblacionals: les truites dels rius Cantàbrics, les del Miño, les del Duero, les del Tajo i les del Guadalquivir. Les poblacions del Guadalquivir pertanyerien a un grup d'influència mediterrània. Els marcadors d'al·lozims i de DNA mitocondrial es troben fortament correlacionats en aquesta vessant, on apunten cap als mateixos grups de poblacions. Per contra, els rius de la vessant mediterrània haurien estat colonitzats pels llinatges Adriàtic i Mediterrani i s'hauria produït una intensa intergradació secundària entre aquests llinatges durant els períodes glacials a partir de l'expansió de les poblacions retingudes a les capçaleres durant els interglacials. Els grups de hibridació, l'aïllament i la deriva en el període interglacial fa que els grups de poblacions identificats pels marcadors d'al·lozims i de DNA mitocondrial no coincideixin.
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Mitochondrial DNA (mtDNA) is one of the most Popular population genetic markers. Its relevance as an indicator Of Population size and history has recently been questioned by several large-scale studies in animals reporting evidence for recurrent adaptive evolution, at least in invertebrates. Here we focus on mammals, a more restricted taxonomic group for which the issue of mtDNA near neutrality is crucial. By analyzing the distribution of mtDNA diversity across species and relating 4 to allozyme diversity, life-history traits, and taxonomy, we show that (i) mtDNA in mammals (toes not reject the nearly neutral model; (ii) mtDNA diversity, however, is unrelated to any of the 14 life-history and ecological variables that we analyzed, including body mass, geographic range, and The World Conservation Union (IUCN) categorization; (iii) mtDNA diversity is highly variable between mammalian orders and families; (iv) this taxonomic effect is most likely explained by variations of mutation rate between lineages. These results are indicative of a strong stochasticity of effective population size in mammalian species. They Suggest that, even in the absence of selection, mtDNA genetic diversity is essentially unpredictable, knowing species biology, and probably uncorrelated to species abundance.
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Background Figs and fig-pollinating wasp species usually display a highly specific one-to-one association. However, more and more studies have revealed that the "one-to-one" rule has been broken. Co-pollinators have been reported, but we do not yet know how they evolve. They may evolve from insect speciation induced or facilitated by Wolbachia which can manipulate host reproduction and induce reproductive isolation. In addition, Wolbachia can affect host mitochondrial DNA evolution, because of the linkage between Wolbachia and associated mitochondrial haplotypes, and thus confound host phylogeny based on mtDNA. Previous research has shown that fig wasps have the highest incidence of Wolbachia infection in all insect taxa, and Wolbachia may have great influence on fig wasp biology. Therefore, we look forward to understanding the influence of Wolbachia on mitochondrial DNA evolution and speciation in fig wasps. Results We surveyed 76 pollinator wasp specimens from nine Ficus microcarpa trees each growing at a different location in Hainan and Fujian Provinces, China. We found that all wasps were morphologically identified as Eupristina verticillata, but diverged into three clades with 4.22-5.28% mtDNA divergence and 2.29-20.72% nuclear gene divergence. We also found very strong concordance between E. verticillata clades and Wolbachia infection status, and the predicted effects of Wolbachia on both mtDNA diversity and evolution by decreasing mitochondrial haplotypes. Conclusions Our study reveals that the pollinating wasp E. verticillata on F. microcarpa has diverged into three cryptic species, and Wolbachia may have a role in this divergence. The results also indicate that Wolbachia strains infecting E. verticillata have likely resulted in selective sweeps on host mitochondrial DNA.
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Phylogenetic analyses of chloroplast DNA sequences, morphology, and combined data have provided consistent support for many of the major branches within the angiosperm, clade Dipsacales. Here we use sequences from three mitochondrial loci to test the existing broad scale phylogeny and in an attempt to resolve several relationships that have remained uncertain. Parsimony, maximum likelihood, and Bayesian analyses of a combined mitochondrial data set recover trees broadly consistent with previous studies, although resolution and support are lower than in the largest chloroplast analyses. Combining chloroplast and mitochondrial data results in a generally well-resolved and very strongly supported topology but the previously recognized problem areas remain. To investigate why these relationships have been difficult to resolve we conducted a series of experiments using different data partitions and heterogeneous substitution models. Usually more complex modeling schemes are favored regardless of the partitions recognized but model choice had little effect on topology or support values. In contrast there are consistent but weakly supported differences in the topologies recovered from coding and non-coding matrices. These conflicts directly correspond to relationships that were poorly resolved in analyses of the full combined chloroplast-mitochondrial data set. We suggest incongruent signal has contributed to our inability to confidently resolve these problem areas. (c) 2007 Elsevier Inc. All rights reserved.
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The toucan genus Ramphastos (Piciformes: Ramphastidae) has been a model in the formulation of Neotropical paleobiogeographic hypotheses. Weckstein (2005) reported on the phylogenetic history of this genus based on three mitochondrial genes, but some relationships were weakly supported and one of the subspecies of R. vitellinus (citreolaemus) was unsampled. This study expands on Weckstein (2005) by adding more DNA sequence data (including a nuclear marker) and more samples, including R v. citreolaemus. Maximum parsimony, maximum likelihood, and Bayesian methods recovered similar trees, with nodes showing high support. A monophyletic R. vitellinus complex was strongly supported as the sister-group to R. brevis. The results also confirmed that the southeastern and northern populations of R. vitellinus ariel are paraphyletic. X v. citreolaemus is sister to the Amazonian subspecies of the vitellinus complex. Using three protein-coding genes (COI, cytochrome-b and ND2) and interval-calibrated nodes under a Bayesian relaxed-clock framework, we infer that ramphastid genera originated in the middle Miocene to early Pliocene, Ramphastos species originated between late Miocene and early Pleistocene, and intra-specific divergences took place throughout the Pleistocene. Parsimony-based reconstruction of ancestral areas indicated that evolution of the four trans-Andean Ramphastos taxa (R. v. citreolaemus, R. a. swainsonii, R. brevis and R. sulfuratus) was associated with four independent dispersals from the cis-Andean region. The last pulse of Andean uplift may have been important for the evolution of R. sulfuratus, whereas the origin of the other trans-Andean Ramphastos taxa is consistent with vicariance due to drying events in the lowland forests north of the Andes. Estimated rates of molecular evolution were higher than the ""standard"" bird rate of 2% substitutions/site/million years for two of the three genes analyzed (cytochrome-b and ND2). (C) 2009 Elsevier Inc. All rights reserved.
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Mitochondrial diseases are clinically and genetically heterogeneous disorders due to primary mutations in mitochondrial DNA (mtDNA) or nuclear DNA (nDNA). We studied a male infant with severe congenital encephalopathy, peripheral neuropathy, and myopathy. The patient`s lactic acidosis and biochemical defects of respiratory chain complexes I, III, and IV in muscle indicated that he had a mitochondrial disorder while parental consanguinity suggested autosomal recessive inheritance. Cultured fibroblasts from the patient showed a generalized defect of mitochondrial protein synthesis. Fusion of cells from the patient with 143B206 rho(0) cells devoid of mtDNA restored cytochrome c oxidase activity confirming the nDNA origin of the disease. Our studies indicate that the patient has a novel autosomal recessive defect of mitochondrial protein synthesis. (C) 2008 Elsevier B.V. All rights reserved.
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7,8-Dihydro-8-oxoguanine DNA glycosylase (OGG1) is a major DNA glycosylase involved in base-excision repair (BER) of oxidative DNA damage to nuclear and mitochondrial DNA (mtDNA). We used OGG1-deficient (OGG1(-/-)) mice to examine the possible roles of OGG1 in the vulnerability of neurons to ischemic and oxidative stress. After exposure of cultured neurons to oxidative and metabolic stress levels of OGG1 in the nucleus were elevated and mitochondria exhibited fragmentation and increased levels of the mitochondrial fission protein dynamin-related protein 1 (Drp1) and reduced membrane potential. Cortical neurons isolated from OGG1(-/-) mice were more vulnerable to oxidative insults than were OGG1(+/+) neurons, and OGG1(-/-) mice developed larger cortical infarcts and behavioral deficits after permanent middle cerebral artery occlusion compared with OGG1(+/+) mice. Accumulations of oxidative DNA base lesions (8-oxoG, FapyAde, and FapyGua) were elevated in response to ischemia in both the ipsilateral and contralateral hemispheres, and to a greater extent in the contralateral cortex of OGG1(-/-) mice compared with OGG1(+/+) mice. Ischemia-induced elevation of 8-oxoG incision activity involved increased levels of a nuclear isoform OGG1, suggesting an adaptive response to oxidative nuclear DNA damage. Thus, OGG1 has a pivotal role in repairing oxidative damage to nuclear DNA under ischemic conditions, thereby reducing brain damage and improving functional outcome. Journal of Cerebral Blood Flow & Metabolism (2011) 31, 680-692; doi:10.1038/jcbfm.2010.147; published online 25 August 2010
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We have recently demonstrated that hypertriglyceridemic (HTG) mice present both elevated body metabolic rates and mild mitochondrial uncoupling in the liver owing to stimulated activity of the ATP-sensitive potassium channel (mitoK(ATP)). Because lipid excess normally leads to cell redox imbalance, we examined the hepatic oxidative status in this model. Cell redox imbalance was evidenced by increased total levels of carbonylated proteins, malondialdehydes, and GSSG/GSH ratios in HTG livers compared to wild type. In addition, the activities of the extramitochondrial enzymes NADPH oxidase and xanthine oxidase were elevated in HTG livers. In contrast, Mn-superoxide dismutase activity and content, a mitochondrial matrix marker, were significantly decreased in HTG livers. isolated HTG liver mitochondria presented lower rates of H(2)O(2) production, which were reversed by mitoK(ATP) antagonists. In vivo antioxidant treatment with N-acetylcysteine decreased both mitoKATP activity and metabolic rates in HTG mice. These data indicate that high levels of triglycerides increase reactive oxygen generation by extramitochondrial enzymes that promote MitoK(ATP) activation. The mild uncoupling mediated by mitoK(ATP) increases metabolic rates and protects mitochondria against oxidative damage. Therefore, a biological role for mitoK(ATP) is a redox sensor is shown here for the first time in an in vivo model of systemic and cellular lipid excess, (C) 2009 Elsevier Inc. All rights reserved.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)