Oxidative stress and reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), which is detoxified by catalase, are implicated in fetal death and birth defects, but embryonic levels of catalase are only about 5% of adult activity, and its protective role is unknown. Our approach involved the use of mice genetically modified to either: (1) express low levels of endogenous catalase (acatalasemic, aCat); or, (2) express human catalase resulting in elevated levels of embryonic catalase activity (hCat). Using these mouse models we investigated the protective importance of constitutive embryonic catalase against endogenous ROS and the ROS-initiating teratogen phenytoin in embryo culture and in vivo. We hypothesized that aCat mice would be more sensitive to endogenous embryonic and phenytoin-enhanced ROS production, while hCat embryos would be less sensitive. aCat and hCat embryos respectively exhibited reduced and enhanced catalase activity compared to wild-type (WT) controls, with conversely enhanced and reduced spontaneous and phenytoin-enhanced embryopathies and DNA oxidation. Among aCat embryos exposed to phenytoin, embryopathies increased with decreasing catalase activity, and were completely blocked by addition of exogenous catalase. The alterations in phenytoin embryopathies were not due to pharmacokinetic differences, as drug concentrations in maternal and fetal tissues were similar among all strains. However, phenytoin concentrations in fetal brain exceeded those in fetal liver or maternal tissues, which may explain the predominance of cognitive deficits over structural birth defects in children exposed in utero to phenytoin. Similarly in untreated aged mice (about 18 months), female aCat mice showed a substantial loss in motor coordination compared to WT controls in the rotarod test. Following in utero exposure to phenytoin, the effect of altered embryonic catalase activity on postnatal neurodevelopment was assessed by several pre- and post-weaning tests. Catalase deficiency (aCat), independent of drug treatment, reduced performance in surface righting, negative geotaxis tests and rotarod tests. Conversely, high catalase expression (hCat) enhanced performance in the surface righting, negative geotaxis, air righting and rotarod tests. Our results provide the first evidence that the quantitatively minor amounts of antioxidative enzymes like catalase in the embryo and fetus provide important protection against the molecular damage and adverse fetal effects caused by developmental and drug-enhanced oxidative stress. Accordingly, interindividual variation in embryonic/fetal activities of catalase, and possibly other antioxidative enzymes, likely constitute an important determinant of risk for adverse developmental outcomes.

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--Columbia University, 1942. / Vita. Bibliography: p. 22.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Abstracted in Dissertation abstracts, v. 17 (1957) no. 6, p. 1361. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 70).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 69-74.

Thèse--Sc. nat.--Strasbourg, 1970. N°: 572. / Bibliogr. f. 141-145.

No description available.

No description available.

Orientadores: Valéria Maia Merzel, Anete Pereira de Souza / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-27T08:16:52Z (GMT). No. of bitstreams: 1 Ottoni_JuliaRonzella_D.pdf: 14116261 bytes, checksum: f49982ceaff5d9b1dd9c87dcf8c01fcf (MD5) Previous issue date: 2015 / Resumo: Os manguezais são ecossistemas peculiares de alta atividade biológica, considerados um dos ambientes mais ricos do mundo. No Brasil, os manguezais ainda são pouco estudados, tornando o conhecimento e exploração de micro-organismos e seus metabólitos nesses ecossistemas um tópico importante. Os manguezais são ambientes adversos, caracterizados, em muitos casos, pela alta salinidade, variações constantes de pH e temperatura, e condições anóxicas. Micro-organismos adaptados à essas condições podem ser fontes de moléculas bioativas ainda desconhecidas e de interesse ambiental e econômico. Neste contexto, o presente trabalho teve como um dos objetivos analisar a diversidade taxonômica e funcional presente em sedimento de manguezal contaminado com petróleo através do sequenciamento de uma biblioteca metagenômica construída em vetor do tipo fosmídio. As análises taxonômicas da biblioteca metagenômica mostraram predominância do filo Proteobacteria, seguido por Actinobacteria, Planctomycetes, Firmicutes, Cloroflexi e Bacteroidetes. Em nível de classe, a mais abundante foi Gamaproteobacteria, seguida de Alfaproteobacteria e Deltaproteobacteria. A diversidade taxonômica se reflete na diversidade metabólica, com espécies capazes de degradar hidrocarbonetos, oxidar enxofre em zonas de transição oxica-anóxica costeiras, transformar metais pesados e outros compostos xenobióticos, dentre outras habilidades. Em adição, foram realizadas triagens funcionais com 4.800 clones da biblioteca e 215 isolados bacterianos para esterase e lipase, 5.184 clones para atividade proteolítica e os genomas de duas bactérias foram analisados in silico na busca de genes que codificam para atividade de catalase. As triagens dos clones resultaram em 17 hits positivos para esterases que posteriormente se revelaram falsos-positivos, e 182 hits positivos para proteases nos ensaios com sondas, sendo 60 hits positivos no pH 4,0, 55 no pH 7,0 e 67 no pH 9,0. Nos ensaios com isolados de bactérias foram detectados 42 com atividade de esterase e 20 com atividade de lipase, sendo que a melhor atividade de esterase foi obtida com um isolado de Gordonia sp. e a melhor atividade de lipase foi obtida para um isolado de Bacillus safensis. Estes dois isolados já possuem seus genomas sequenciados e uma análise in silico foi realizada para busca dos respectivos genes de atividade lipolítica. Na busca in silico por catalases foi selecionada uma sequência completa para ensaios de expressão. Foram desenhados pares de primers para amplificação dos genes das três enzimas e, destes, os genes da lipase e da catalase foram expressos, ambos do Bacillus safensis. A caracterização funcional e estrutural foi realizada com a catalase, cujo gene possui 1500 pb, é um tetrâmero composto por 4 monômeros de 59 kDa cada, ativa em intervalo de pH de 6,0 a 12 e temperaturas de 25 ºC a 55 ºC, com atividade ótima em pH 10 e 30 ºC e estável até 40 ºC. Os resultados mostraram que o mangue impactado é composto por populações microbianas adaptadas ao ambiente, e também responsáveis pela degradação de compostos xenobióticos, auxiliando na sua recuperação. A abordagem metagenômica foi bem sucedida nas triagens funcionais para proteases, indicando um grande potencial proteolítico no ambiente. As triagens funcionais com os isolados mostraram a presença de enzimas lipolíticas ativas, e a catalase expressa exibiu características funcionais interessantes, tais como atividade ótima em pH 10 e estabilidade térmica até 40 ºC, com potencial aplicação industrial / Abstract: Mangroves are unique ecosystems of high biological activity and are considered one of the richest environments in the world. In Brazil, mangroves are still poorly studied, making the knowledge of microorganisms and their metabolites in these ecosystems an important topic. Mangroves are harsh environments characterized, in many cases, by high salinity, high pH and temperature variations, and anoxic conditions. Microorganisms adapted to these conditions may be sources of yet unknown bioactive molecules of environmental and economic interest. In this context, one of the objectives of the present study was to analyze the taxonomic and functional diversity present in mangrove sediment contaminated with oil through the sequencing of a metagenomic library constructed using fosmid vector. The taxonomic analysis of the metagenomic library showed predominance of Proteobacteria phylum, followed by Actinobacteria, Planctomycetes, Firmicutes, Chloroflexi and Bacteroidetes. At class level, the most abundant was Gammaproteobacteria, followed by Alphaproteobacteria and Deltaproteobacteria. The taxonomic diversity is reflected in the metabolic diversity, with species capable of degrading hydrocarbons, oxidizing sulfur in oxic-anoxic coastal transition zones, transforming heavy metals and other xenobiotic compounds, among other skills. In addition, functional screenings were performed with 4,800 fosmid clones and 215 bacterial isolates for esterases and lipases, and with 5,184 clones for proteolytic activity and the genomes of two bacteria were analyzed in silico to search for genes encoding catalase activity. The screening of the clones resulted in 17 positive hits for esterases that later proved to be false-positive, and 182 positive hits for proteases using probe-based assays: 60 positive hits at pH 4.0, 55 at pH 7.0 and 67 at pH 9.0. Tests with bacterial isolates yielded 42 positive hits for esterase activity and 20 for lipase activity. The best esterase activity was obtained with one isolate of Gordonia sp. and the best lipase activity was obtained with one isolate of Bacillus safensis. These two isolates have their genomes already sequenced and in silico analyses were performed in the search for the respective genes of lipolytic activity. In silico analysis for catalase genes was performed and a complete sequence was selected for expression assays. Primer pairs were designed to amplify the genes encoding the three enzymes, and of these, lipase and catalase were expressed, both from Bacillus safensis. The functional and structural characterization was carried out with catalase, which gene has 1500 bp, it is a tetramer composed of four monomers of 59 kDa each, active in the pH range from 6.0 to 12 and temperatures of 25 °C to 55 °C, with optimum activity at pH 10 and 30 °C and stable until 40 ºC. The results showed that oil-impacted mangrove is composed by microbial populations adapted to the environment, responsible for the degradation of xenobiotics and assisting in the recovery of the mangrove. The metagenomics approach was successful in the functional screening for proteases, indicating a great proteolytic potential in the environment. Functional screening with the bacterial isolates showed presence of active lipolytic enzymes, and the expressed catalase exhibited unique functional characteristics, such as optimal activity at pH 10 and thermal stability until 40 ºC, with potential industrial application / Doutorado / Genetica de Microorganismos / Doutora em Genética e Biologia Molecular

Catalase HPII of Escherichia coli is similar in sequence and structure to other catalases including the conservation of several residues on both the distal and proximal sides of the active center heme. The roles of many residues on the distal side of the heme have been well characterized. By contrast, very few residues on the proximal side of the heme or in the plane of the heme have been investigated. The primary goal of this thesis is to develop a better understanding of the role of the residues and structural features at the core of catalases and in the lateral access channel. The results demonstrate that a break in molecular symmetry does not have any functional significance. Replacing Ile274 with a Cys resulted in the heme being covalently linked to the protein through a Cys-vinyl bond which is hypersensitive to X-ray irradiation being largely degraded within seconds of exposure to the X-ray beam.