Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-06-29T11:30:31Z No. of bitstreams: 1 elisandramariadossantos.pdf: 1982471 bytes, checksum: c22e90b870706b5581808c86f2a81b4f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-07-03T14:40:57Z (GMT) No. of bitstreams: 1 elisandramariadossantos.pdf: 1982471 bytes, checksum: c22e90b870706b5581808c86f2a81b4f (MD5) / Made available in DSpace on 2018-07-03T14:40:57Z (GMT). No. of bitstreams: 1 elisandramariadossantos.pdf: 1982471 bytes, checksum: c22e90b870706b5581808c86f2a81b4f (MD5) Previous issue date: 2018-02-20 / Infecções bacterianas constituem uma ameaça à saúde humana e um sério problema para os sistemas de saúde, devido à uma crescente incidência de infecções causadas por bactérias multirresistentes. Entre importantes bactérias causadoras de infecções estão as Staphylococcus aureus, espécie de maior interesse médico, sendo a causadora mais comum de infecções nosocomiais e também comunitárias; Staphylococcus epidermidis, isolado mais frequente encontrada em epitélios humanos, sendo a principal responsável por infecções relacionadas a dispositivos médicos; e a Escherichia coli, dentre as bactérias gram-negativas é a causadora mais comum de infecções nosocomiais e adquiridas na comunidade. Peptídeos antimicrobianos (AMPs) são um grupo diverso e abundante de compostos produzidos por organismos multicelulares, tanto animais quanto vegetais, e são componentes principais da imunidade inata contra infecções e podem ser alternativas no tratamento de doenças infecciosas. Neste contexto, a associação entre AMPs e a nanotecnologia pode ser utilizada como estratégia no combate a infecções bacterianas. Entre os nanomateriais existentes estão as nanopartículas poliméricas, que são biodegradáveis e biocompatíveis. Esses nanomateriais podem participar de formulações contendo antibióticos usuais ou novas moléculas bioativas, como os AMPs, e podem ser alternativas promissoras para o tratamento de infecções bacterianas. O objetivo deste trabalho foi avaliar o potencial antimicrobiano do peptídeo Lrot3.6 nanoencapsulado frente à bactérias gram-positivas e gram-negativas, bem como os efeitos citotóxicos em cultura in vitro de células HEK293. Foram sintetizadas nanopartículas de quitosana livre e estruturadas com o peptídeo Lrot3.6 pelo método de gelificação iônica. As nanopartículas sintetizadas foram caracterizadas quanto ao tamanho, índice de polidispersão, potencial Zeta e foi determinada a eficiência de encapsulação do peptídeo. Após a síntese, foram realizados ensaios antimicrobianos por microdiluição em placa de 96 poços, utilizando cloranfenicol, o peptídeo livre e nanoencapsulado, e a nanopartícula livre nas concentrações de 8, 16, 32, 64 e 128 μg/mL, bem como ensaio para análise da ação bactericida ou bacteriostática dos tratamentos e avaliação da citotoxicidade dos tratamentos por MTT. As análises estatísticas foram realizadas pelo teste de Tukey (p<0,05). Os índices de polidispersão foram 0,356 (nanopartícula livre) e 0,398 (peptídeo nanoencapsulado). Os potenciais Zeta foram 36,5 ± 2,1 mV (nanopartícula livre) e 35,7 ± 2,2 mV (peptídeo nanoencapsulado). O peptídeo nanoencapsulado apresentou uma eficiência de encapsulação de 93,55%. Em relação aos ensaios antimicrobianos, o peptídeo livre apresentou MIC de 8 μg/mL para todas as bactérias testadas. A nanopartícula livre também apresentou efeito antimicrobiano, com MIC de 64 μg/mL para todas as bactérias. A nanoencapsulação do peptídeo favoreceu principalmente a inibição do crescimento de E. coli, bactéria em que o tratamento mais se destacou por possível efeito sinérgico entre a quitosana e o peptídeo Lrot3.6. No geral, observou-se também a liberação prolongada do peptídeo em até 48 horas. Além disso, o nanossistema na menor concentração, 8 μg/mL, não foi citotóxico em até 48 horas. / Bacterial infections are a threat to human health and a serious problem for health systems due to an increasing incidence of infections caused by multiresistant bacteria. Among important bacteria that cause infections are Staphylococcus aureus, a species of major medical interest, being the most common cause of nosocomial and community infections; Staphylococcus epidermidis, the most frequent isolate found in human epithelia, being the main responsible for infections related to medical devices; and Escherichia coli among gram-negative bacteria is the most common cause of nosocomial and community-acquired infections. Antimicrobial peptides (AMPs) are a diverse and abundant group of compounds produced by multicellular organisms, both animal and plant, and are major components of innate immunity against infections and may be alternatives in the treatment of infectious diseases. In this context, the association between AMPs and nanotechnology can be used as a strategy to combat bacterial infections. Among the existing nanomaterials are polymer nanoparticles, which are biodegradable and biocompatible. These nanomaterials may participate in formulations containing usual antibiotics or novel bioactive molecules, such as AMPs, and may be promising alternatives for the treatment of bacterial infections. The objective of this work was to evaluate the antimicrobial potential of the peptide Lrot3.6 nanoencapsulated against gram-positive and gram-negative bacteria, as well as the cytotoxic effects in vitro culture of HEK293 cells. Free chitosan nanoparticles were synthesized and structured with the Lrot3.6 peptide by the ionic gelation method. The synthesized nanoparticles were characterized by size, polydispersity index, Zeta potential and the peptide encapsulation efficiency was determined. After the synthesis, antimicrobial assays were performed by microdilution in a 96-well plate using chloramphenicol, the free and nanoencapsulated peptide, and the free nanoparticle at the concentrations of 8, 16, 32, 64 and 128 μg/mL, as well as assay for analysis of the bactericidal or bacteriostatic action of the treatments and evaluation of the cytotoxicity of the treatments by MTT. Statistical analyzes were performed using the Tukey test (p<0.05). The polydispersity indices were 0.356 (free nanoparticle) and 0.398 (nanoencapsulated peptide). Zeta potentials were 36.5 ± 2.1 mV (free nanoparticle) and 35.7 ± 2.2 mV (nanoencapsulated peptide). The nanoencapsulated peptide showed an encapsulation efficiency of 93.55%. Regarding the antimicrobial assays, the free peptide showed MIC of 8 μg/mL for all the bacteria tested. The free nanoparticle also showed antimicrobial effect, with MIC of 64 μg/mL for all bacteria. Nanoencapsulation of the peptide mainly favored the inhibition of the growth of E. coli, a bacterium in which the treatment was most highlighted by a possible synergistic effect between the chitosan and the peptide Lrot3.6. In general, prolonged release of the peptide was also observed within 48 hours. In addition, the nanosystem at the lowest concentration, 8 μg/mL, was not cytotoxic within 48 hours.

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-20T16:40:36Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_SheylaSilvaLima_2015.pdf: 4958893 bytes, checksum: 21511e1c9e1a86ea210befeb33c91543 (MD5) / Made available in DSpace on 2016-04-20T16:40:36Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_SheylaSilvaLima_2015.pdf: 4958893 bytes, checksum: 21511e1c9e1a86ea210befeb33c91543 (MD5) Previous issue date: 2015-02-24 / FACEPE / Ciclotídeos são uma classe de peptídeos antimicrobianos (AMPs - do inglês Antimicrobial peptide) cíclicos de plantas, compostos de, aproximadamente, 30 resíduos de aminoácidos, sendo seis cisteínas conservadas e conectadas por três pontes de dissulfeto. Sua expressão é constitutiva, tendo sua principal função na defesa vegetal contra patógenos, que podem causar perdas significativas em culturas importantes para a agricultura, como no caso da família Poaceae que apresenta destacada importância econômica no Brasil e no mundo. Nesse estudo foi conduzida uma busca por genes relacionados a ciclotídeos vegetais, disponíveis em bancos de dados de acesso restrito e público, com vistas ao isolamento e caracterização in silico desses peptídeos. Através da busca nos genomas de Hevea brasiliensis, Manihot esculenta, Ricinus communis, Sorghum bicolor e Zea mays; bem como no transcriptoma de Vigna unguiculata foi verificado que apenas o genoma de Zea mays apresentou dois possíveis genes codificadores de ciclotídeos. Assim, primers foram desenhados para o isolamento destes genes em milho. Além da espécie Z. mays, as espécies Triticum aestivum (trigo) e Secale cereale (centeio), foram utilizadas para a tentativa de isolamento a partir dos pares de primers desenhados. Foram obtidos 19 fragmentos (amplicons), sendo quatro deles (zm315, zm316, zm317, sc359) com o domínio ciclotídeo, os três primeiros de milho e o último de centeio. Essas quatro sequências foram, então, submetidas a uma caracterização in silico, para predição da estrutura secundaria, terciaria e função predita. Verificou-se que esses peptídeos apresentam as seis cisteínas conservadas, três pontes dissulfeto e o padrão de aminoácidos entre as cisteínas, similar aos encontrados em ciclotídeos. Ainda foi possível a predição de algumas propriedades físico-químicas e modelagem por homologia para as quatro proteínas, o que mostrou a qualidade e confiabilidade dos modelos. Sugere-se que dois dos ciclotídeos isolados (zm315, zm316) pertençam a uma nova classe de peptídeos lineares, mas com características de ciclotídeos. / Cyclotides are a class of cyclic antimicrobial peptides (AMPs) present on plants, composed by approximately 30 amino acid residues, including six conserved cysteines connected by three disulphide bridges. Its expression is constitutive, with main function on plant defense against pathogens, that may cause significant losses in important cultivars, as in the case of Poaceae, a family that presents economic importance for the agriculture in Brazil and worldwide. This study performed a search for genes related to plant cyclotides, available in restricted and public access databases, aimed at their in silico isolation and characterization. Searching for these peptides in Hevea brasiliensis, Manihot esculenta, Ricinus communis, Sorghum bicolor, Vigna unguiculata and Zea mays genomes, we obtained two possible genes encoding Cyclotides in Z. mays. Thus, primers were designed for the isolation of these genes in maize as well in wheat (Triticum aestivum) and rye (Secale cereale) species. We obtained 19 amplicons and four of them (zm315, zm316, zm317, sc359) presented cyclotide domain. These four sequences were then subjected to in silico characterization, for predicting their secondary and tertiary structures, as well their function. It was found that these peptides present six conserved cysteines, three disulphide bridges and the amino acid pattern between the cysteines similar to those found in cyclotides. It was also possible to predict some physical chemical properties and also building a 3D protein by homology modeling for the four peptides, presenting high quality and reliability. Our analysis indicates that two isolated cyclotides (zm315, zm316) appear to belong to a new class of linear peptides, but with cyclotide features.

The rapid increase of multi-drug resistant bacteria and associated deaths has stimulated research into the development of novel therapeutic options. Antimicrobial peptides (AMPs) display a high therapeutic potential in solving this problem. Research focuses on new ways to enhance the antibacterial activity of AMPs and this includes the amidation of the C-terminus. Once the structure of an AMP is altered it is altered it is necessary to revaluate the properties of this AMP compared to the unaltered peptide. In this study, a peptide fragment Os(3-12), based on a defensin from the tick Ornithodoros savignyi, was amidated at the C-terminus. The effect of C-terminal amidation on the structural, antibacterial, cytotoxic and antioxidant activities of Os(3-12)NH2 was investigated and compared to Os(3-12) as well as the parent peptide Os. Mode of action related to membrane permeabilization was evaluated. The effect of serum and on the antibacterial activity of Os(3-12)NH2 was also determined. Circular dichroism experiments indicated Os(3-12) and Os(3-12)NH2 to be unstructured in sodium dodecyl sulphate micelles and 50% trifluoroethanol, unlike Os which was predominantly α-helical. Although still less potent than Os, the determined minimum bactericidal concentration (MBC) for each peptide indicated that amidation increases the bactericidal activity of Os(3-12) by 16-fold against Escherichia coli and by 8-fold against both Pseudomonas aeruginosa and Bacillus subtilis. In comparison amidation enhanced the activity of the peptide towards Staphylococus aureus by only 2-fold. The kinetics of bactericidal activity revealed that Os(3-12)NH2 killed E. coli within 10 minutes and B subtilis within 60 minutes. SYTOX green was applied to evaluate the effects of the peptides on the membrane integrity of the bacterial cells. LL-37, a peptide known to disrupt microbial membranes, induced membrane permeabilization of both E. coli and S. aureus membranes. Both Os and Os(3-12)NH2 were found to also cause membrane permeabilization of these bacteria, albeit not to the same extent as LL-37, thus suggesting possible internal targets subsequent to membrane permeabilization. In the presence of 30% human serum and a physiological salt mixture comprising of 145 mM NaCl, 2.5 mM CaCl2 and 1 mM MgCl2 the bactericidal activity of Os(3-12)NH2 was lost. The amidated peptide was found to be non-toxic towards human erythrocytes and Caco-2 cells. Os(3-12)NH2 showed strong antioxidant activity and was found to be 15-fold more active than glutathione (GSH), a known antioxidant. In conclusion Os(3-12)NH2 has been identified as a multifunctional AMP that is nontoxic to mammalian cells. However the therapeutic potential of Os(3-12)NH2 may be restricted to topical applications due to the peptide’s inactivity under physiological conditions. Although Os(3-12)NH2 causes membrane permeabilization, indications are that there are additional intracellular targets that need to be identified. / Dissertation (MSc)--University of Pretoria, 2016. / Biochemistry / Unrestricted

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-22T16:55:34Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_SheylaSilvaLima_2015.pdf: 4958893 bytes, checksum: 21511e1c9e1a86ea210befeb33c91543 (MD5) / Made available in DSpace on 2016-04-22T16:55:34Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_SheylaSilvaLima_2015.pdf: 4958893 bytes, checksum: 21511e1c9e1a86ea210befeb33c91543 (MD5) Previous issue date: 2015-02-24 / FACEPE / Ciclotídeos são uma classe de peptídeos antimicrobianos (AMPs - do inglês Antimicrobial peptide) cíclicos de plantas, compostos de, aproximadamente, 30 resíduos de aminoácidos, sendo seis cisteínas conservadas e conectadas por três pontes de dissulfeto. Sua expressão é constitutiva, tendo sua principal função na defesa vegetal contra patógenos, que podem causar perdas significativas em culturas importantes para a agricultura, como no caso da família Poaceae que apresenta destacada importância econômica no Brasil e no mundo. Nesse estudo foi conduzida uma busca por genes relacionados a ciclotídeos vegetais, disponíveis em bancos de dados de acesso restrito e público, com vistas ao isolamento e caracterização in silico desses peptídeos. Através da busca nos genomas de Hevea brasiliensis, Manihot esculenta, Ricinus communis, Sorghum bicolor e Zea mays; bem como no transcriptoma de Vigna unguiculata foi verificado que apenas o genoma de Zea mays apresentou dois possíveis genes codificadores de ciclotídeos. Assim, primers foram desenhados para o isolamento destes genes em milho. Além da espécie Z. mays, as espécies Triticum aestivum (trigo) e Secale cereale (centeio), foram utilizadas para a tentativa de isolamento a partir dos pares de primers desenhados. Foram obtidos 19 fragmentos (amplicons), sendo quatro deles (zm315, zm316, zm317, sc359) com o domínio ciclotídeo, os três primeiros de milho e o último de centeio. Essas quatro sequências foram, então, submetidas a uma caracterização in silico, para predição da estrutura secundaria, terciaria e função predita. Verificou-se que esses peptídeos apresentam as seis cisteínas conservadas, três pontes dissulfeto e o padrão de aminoácidos entre as cisteínas, similar aos encontrados em ciclotídeos. Ainda foi possível a predição de algumas propriedades físico-químicas e modelagem por homologia para as quatro proteínas, o que mostrou a qualidade e confiabilidade dos modelos. Sugere-se que dois dos ciclotídeos isolados (zm315, zm316) pertençam a uma nova classe de peptídeos lineares, mas com características de ciclotídeos. / Cyclotides are a class of cyclic antimicrobial peptides (AMPs) present on plants, composed by approximately 30 amino acid residues, including six conserved cysteines connected by three disulphide bridges. Its expression is constitutive, with main function on plant defense against pathogens, that may cause significant losses in important cultivars, as in the case of Poaceae, a family that presents economic importance for the agriculture in Brazil and worldwide. This study performed a search for genes related to plant cyclotides, available in restricted and public access databases, aimed at their in silico isolation and characterization. Searching for these peptides in Hevea brasiliensis, Manihot esculenta, Ricinus communis, Sorghum bicolor, Vigna unguiculata and Zea mays genomes, we obtained two possible genes encoding Cyclotides in Z. mays. Thus, primers were designed for the isolation of these genes in maize as well in wheat (Triticum aestivum) and rye (Secale cereale) species. We obtained 19 amplicons and four of them (zm315, zm316, zm317, sc359) presented cyclotide domain. These four sequences were then subjected to in silico characterization, for predicting their secondary and tertiary structures, as well their function. It was found that these peptides present six conserved cysteines, three disulphide bridges and the amino acid pattern between the cysteines similar to those found in cyclotides. It was also possible to predict some physical chemical properties and also building a 3D protein by homology modeling for the four peptides, presenting high quality and reliability. Our analysis indicates that two isolated cyclotides (zm315, zm316) appear to belong to a new class of linear peptides, but with cyclotide features.

This report focuses on the application of adaptive arrays to the Advanced Mobile Phone Service (AMPS) and Code Division Multiple Access (CDMA) cellular systems. Adaptive arrays have been proposed as early as in the 1960s to improve the signal quality, but most of its applications were restricted to defense purposes. Recently, there has been a surge in interest of applying adaptive arrays for cellular systems. This work introduces new blind adaptive array algorithms for AMPS and CDMA signals. The theoretical capacity limit using an adaptive array at the base station for an AMPS cellular system is derived in this work. One of the significant contributions in this research is a macrocell channel model which provides angle-of-arrival (AOA) statistics of the multipath components. Practical issues involved in the implementation of an adaptive array are addressed and the author's implementation of an 8-element adaptive array operating at 2.05 GHz is explained. This research also analyzes the capacity that can be o ered by an adaptive array in a system where CDMA users co-exist with existing AMPS users. A novel cellular CDMA system which exploits adaptive arrays is introduced and the capacity o ered by this system is compared with existing and other systems exploiting spatial dimension. / Ph. D.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-05-10T13:03:57Z No. of bitstreams: 1 carolinadossantosfernandesdasilva.pdf: 3138226 bytes, checksum: 48d21f2f7120dba69bf9b23c69d8ed0b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-05-22T15:24:12Z (GMT) No. of bitstreams: 1 carolinadossantosfernandesdasilva.pdf: 3138226 bytes, checksum: 48d21f2f7120dba69bf9b23c69d8ed0b (MD5) / Made available in DSpace on 2018-05-22T15:24:12Z (GMT). No. of bitstreams: 1 carolinadossantosfernandesdasilva.pdf: 3138226 bytes, checksum: 48d21f2f7120dba69bf9b23c69d8ed0b (MD5) Previous issue date: 2016-10-31 / Peptídeos antimicrobianos são um grupo diverso de moléculas bioativas produzidas naturalmente por uma variedade de organismos procariotos e eucariotos, e que tem atividade antimicrobiana. Tendo em vista que o Brasil representa o país de maior incidência de leishmaniose no continente americano e a inexistência de peptídeos bacterianos com atividade neste parasito, o objetivo desde trabalho foi a prospecção de peptídeos produzidos por bactérias com ênfase na atividade anti-Leishmania. Foram utilizadas 466 amostras bacterianas para a obtenção de extratos brutos extracelulares, investigados quanto a atividade antimicrobiana total, utilizando como células-alvo culturas de bactérias (Grampositivas e negativas), leveduras (Candida sp) e Leishmania sp. Esta avaliação da atividade antimicrobiana total permitiu definir as amostras produtoras de substâncias bioativas, bem como a caracterização do espectro de ação da substância antimicrobiana. E somente os extratos que tiveram atividade anti- Leishmania foram submetidos a precipitação protéica para avaliação da produção de peptídeos antimicrobianos. Quanto à caracterização da amostra produtora, foram realizados testes morfo-tintoriais, genéticos e metabólicos para garantia da pureza da cultura e determinação do melhor momento fisiológico de produção da substância antimicrobiana. Em relação ao espectro de ação, 222 extratos tiveram atividade antagônica ao crescimento bacteriano; 05 extratos tiveram atividade antagônica à Candida sp.; e 20 extratos tiveram atividade antagônica ao crescimento de Leishmania sp., totalizando 51 % de amostras positivas para produção de substâncias antimicrobianas. Quanto à atividade anti-Leishmania, os valores médios de inibição de extratos a 20 mg/mL em formas promastigotas do parasito pelo método do MTT foi de 33 % em L. braziliensis e L. chagasi, 30,7 % em L. major e 29 % em L. amazonensis. A redução da viabilidade de formas amastigotas também foi observada para o extrato bruto a 40 mg/mL de Staphylococcus edpidermidis (CGP360), com valor de 60 %. E esse mesmo extrato não apresentou toxicidade para macrófagos peritoneais, resultado importante para novas drogas de uso sistêmico. Quanto à caracterização da amostra produtora, observou-se que a produção da substância antagonista com maior atividade anti- Leishmania ocorreu em extratos advindos de culturas crescidas em meios TSB e BHI e provenientes da fase estacionária de crescimento. Estudos adicionais devem ser realizados para uma melhor compreensão da interação dos extratos bacterianos em espécies de Leishmania, mas os resultados descritos neste trabalho são promissores e inéditos na literatura científica. / Antimicrobial peptides are a diverse group of bioactive molecules naturally produced by a variety of prokaryotic and eukaryotic organisms with antimicrobial activity. Brazil represents the highest incidence country of leishmaniasis in the American continent, so the objective of this work was prospect bacteria peptides with anti-Leishmania activity. A total of 466 bacterial samples were used to produce extracellular crude extracts to evaluate antimicrobial activity against bacterial cells (Gram-positive and negative bacteria), yeast (Candida sp) and Leishmania sp. and characterize antimicrobial spectrum of action. Only Leishmania activity extracts were submitted to protein precipitation and tested to peptides production. The producing sample were characterized by genetic, morphologic and metabolic tests, and the best physiological moment of peptides production was determinate. The results showed that 222 extracts had bacterial activity, 05 extracts had Candida activity, and 20 extracts had Leishmania activity, summarizing 51 % of positive samples to antimicrobial substances production. For promastigote Leishmania activity, 20 mg/ mL extracts showed inhibition values by MTT method of 33 % in L. braziliensis and L. chagasi, 30.7 % in L. major and 29 % in L. amazonensis. The amastigote forms viability was observed for 40 mg/mL crude extract of Staphylococcus edpidermidis (CGP360), with a reduction value of 60 %. And this same extract did not have toxicity to peritoneal macrophages, an important result for new drugs of systemic use. Concerning the characterization of the producing sample, it was observed that the production of the antagonistic substance with the highest anti-Leishmania activity occurred in TSB and BHI media extracts coming from stationary phase. Additional studies should be performed to better understand the interaction of bacterial extracts in Leishmania species, but the results described in this paper are promising and unpublished in the scientific literature.

Les aires marines protégées (AMPs), soulèvent un intérêt croissant pour leur capacité à améliorer la conservation des ressources marines et, potentiellement, les captures des pêcheries au travers de l'export de poissons et de larves vers les zones pêchées. Des lacunes importantes subsistent dans nos connaissances des impacts du mouvement des poissons sur le fonctionnement des AMPs, et sur la manière dont les AMPs protégeant les populations de poissons modérément à fortement mobiles pourraient être efficaces sans être extrêmement larges. Différents modèles sont utilisés ici afin de combler ces lacunes de connaissances. Tout d'abord, un modèle conceptuel a été développé afin d'explorer les impacts du mouvement des poissons sur l'efficacité des AMPs comparativement à ceux de la dispersion larvaire. Les résultats de ce modèle démontrent que le mouvement des poissons a un impact négatif plus fort sur la persistance d'une population dans les réseaux d'AMPs que la dispersion larvaire. La redistribution de l'effort de pêche anciennement dans les AMPs et la concentration des pêcheurs en bordure d'AMPs réduisent de façon significative la persistance et les captures des populations se dispersant dans le stade adulte, tandis qu'elles n'ont qu'un effet marginal pour les populations se dispersant dans le stade larvaire. Deux modèles appliqués ont été ensuite développés afin d'examiner les impacts des AMPs protégeant des fractions spécifiques de populations migratrices. Un modèle spatialement explicite a été utilisé afin d'étudier les effets des AMPs pour deux populations de merlus sud africaines effectuant des migrations ontogéniques. Les résultats de ce modèle montrent que les AMPs ciblant les juvéniles entraînent une augmentation considérable de la biomasse féconde. Cette augmentation de biomasse conduit à une amélioration des captures de certaines, mais pas de toutes les flottes de pêche. Un modèle par recrue est utilisé afin d'évaluer les effets des AMPs pour les populations récifales effectuant des migrations pour former des agrégations de ponte transitoires. L'application de ce modèle à deux populations de poissons des Seychelles révèle que les AMPs protégeant les agrégations de ponte augmentent le potentiel reproductif des poissons en général, mais pas les captures par recrue. / Marine protected areas (MPAs) are increasingly considered for their ability to improve species conservation and, potentially, fisheries yields via the export of fish and larvae to fished areas. Critical knowledge gaps remain on the impacts of fish movement for MPA functioning and on how MPAs protecting moderately to highly mobile populations may be effective without being extremely large. Here, different models are used to address these knowledge gaps. First, a conceptual model was developed to explore the impacts of fish movement versus larval dispersal on MPA effectiveness. Results demonstrate that fish movement has a stronger negative impact on population persistence in MPA networks than larval dispersal. Redistribution of the fishing effort formerly in MPAs and concentration of fishers on MPA borders dramatically reduce persistence and yields for mobile populations, while they marginally change results for populations with dispersing larvae. Two applied models examining the effects of MPAs targeting specific fractions of migratory populations were then developed. A spatially-explicit model was used to study the effects of MPAs on two South African hake populations undergoing ontogenetic migrations. Results show that MPAs targeting juveniles considerably increase hake spawning biomass. This increase in biomass improves the yields of some, but not all fishing fleets. A per-recruit model was used to assess MPA effects for reef populations migrating to form transient spawning aggregations. Applying the model to two populations from Seychelles, MPAs protecting spawning aggregations are found to improve fish reproductive potential in general, but not yield-per-recruit.

La recherche de nouvelles molécules bioactives utilisables en thérapeutique est un enjeu majeur de santé publique en particulier dans le traitement de certaines maladies telle que les infections bactériennes.La résistance naturelle des bactéries et la surutilisation des antibiotiques ont entraîné la sélection de bactéries pathogènes résistantes à de multiples médicaments. Depuis les dernières décennies, la résistance aux antibiotiques conventionnels a limité les options thérapeutiques, entraînant une augmentation significative de la mortalité et de la morbidité dans les hôpitaux. En outre, depuis 1970, seules deux nouvelles classes d'antibiotiques ont été mises sur le marché. Les venins constituent une source riche de substances naturelles pharmacologiquement actives uniques et novatrices, tels que les peptides antimicrobiens (PAMs) qui représentent une alternative originale pour remédier à ce problème de santé publique.Dans notre étude, parmi les 200 venins d’animaux étudiés pour leurs propriétés antibactériennes, au moins six PAMs ont été isolés à partir d’un venin d’insecte. Le peptide 1 original inhibe la croissance des bactéries Gram positives et négatives mais présente une forte hémotoxicité (IT = 1,6-3,2). La synthèse en phase solide d’analogues structuraux a permis d’identifier R1W8 et I1N11, moins toxiques (IT = 18 et >800 respectivement). Les résultats préliminaires de l’étude du mécanisme d’action suggèrent que ces peptides agissent contre les bactéries par perméabilisation de leur membrane cytoplasmique. Ces peptides peuvent servir de modèles pour l’élaboration de nouveaux agents antimicrobiens. / The research for new bioactive molecules which can be used in therapeutic is a major public health issue, particularly in the treatment of certain diseases such as bacterial infections.The natural resistance of bacteria consecutive to overuse of antibiotics have resulted in the selection of pathogenic multi-drug resistant bacteria. Over the last few decades, resistance to conventional antibiotics has limited treatment options, resulting in a significant increase in mortality and morbidity in hospitals. Moreover, since 1970, only two new classes of antibiotics have been placed on the market. Venoms are known to be a rich source of unique and innovative pharmacologically active substances, such as antimicrobial peptides (PAMs), which represent an original alternative to small molecules for the development of new active and non-resistance inducing antibiotics.In our study, among the 200 venoms of animals studied for their antibacterial properties, at least six PAMs were isolated from an insect venom. The original peptide 1 inhibits the growth of Gram positive and negative bacteria but shows a high hemotoxicity (TI = 1,6-3,2). The solid phase synthesis of structural analogs allowed to identify R1W8 and I1N11, less toxic (TI = 18 et >800 respectively). The preliminary results of the action mechanism study suggest that these peptides have a pore-forming action on bacteria cytoplasmic membrane. These peptides can be used as models for the development of new antimicrobial agents.

The purpose of this work was to study polymer degradation mechanisms as well as ways to mitigate it. In the area of chemical stability, defined as divalent cation tolerance of acrylic polymers as hydrolysis increases, use of the n-vinyl pyrrolidone (NVP) monomer helps to preserve viscosity and tolerate higher calcium concentrations over those polymers without NVP. Also, ethylenediaminetetraacetate tetrasodium salt (EDTA-Na+4) is shown to sequester calcium ions at alkaline conditions (pH>10) and, in the case of lab-aged post-hydrolyzed poly(AM-co-AMPS), helps to retain full viscosity at all calcium concentrations when EDTA is present at a stoichiometric equivalence of calcium. Many discrepancies exist in the literature concerning the presence or absence of degradation under various field or laboratory conditions. Carbonate and bicarbonate, which are typically present in natural waters but often neglected in lab-prepared brines, prove to be a hidden variable in resolving why Shupe (1981) saw no loss in viscosity when sodium dithionite was added to polymer in the presence of oxygen (with bicarbonates) but others (Knight, 1973 and Levitt and Pope, 2008) observed severe degradation under similar conditions (but without bicarbonates). A commercial HPAM polymer (Flopaam 3630S) has been shown to be stable in the presence of ferrous iron in the absence of oxygen, clarifying an apparent discrepancy in the literature between the results of Yang and Treiber (1985) and Kheradmand (1987). Dissolved oxygen (DO) levels, and not redox potential (ORP) measurements, are often reported in polymer stability research on oxidative degradation. ORP is shown to be a better measure of the onset of degradation because oxygen is initially being consumed and may not appear until substantial degradation has occurred. Although generally believed to be a detriment to polymer stability in the field, aeration of iron-laden source water prior to hydration of polymer may be beneficial in certain cases where exposure to air in unavoidable. Also, a novel process of safely producing sodium dithionite in the field proves to perform better in terms of long-term polymer stability in anaerobic conditions than the traditional method of using a solution made from powder dithionite. Finally, a pre-sheared 5 million Dalton HPAM is successfully injected into a 3 mD carbonate reservoir core plug. Remarkably, permeability reduction factors remain at values close to unity. However, pressure data from ASP tertiary corefloods suggest that polymer is not feasible for field injections. / text

Em artrópodes o sistema imune inato contribui para a adaptação de animais como os escorpiões à diferentes ambientes. Esse sistema é composto por mecanismos capazes de agir contra injúrias e a ação de microrganismos e entre esses mecanismos estão os peptídeos antimicrobianos (PAMs). O objetivo deste trabalho foi identificar PAMs presentes na hemolinfa de Tityus serrulatus. Para isso sua hemolinfa foi extraída e separados os hemócitos e plasma, em seguida fracionamos em 3 concentrações de acetonitrila em TFA 0,05% (05, 40 e 80%). Estas frações foram submetidas a uma cromatografia liquida de alta eficiência (CLAE) e os picos foram avaliados quanto a sua ação antimicrobiana e hemolítica. Foram identificadas 16 frações que apresentam atividade antimicrobiana. Uma das frações com atividade antimicrobiana, presente nos hemócitos apresentou similaridade com defensina descrita em carrapatos da espécie Ixodes scapularis. Essa fração possui aproximadamente 3486 Da, não apresenta atividade hemolítica e foi denominada como Serrulina. / In arthropods, its innate immune system contributes to the adaptation of animals like scorpions to different environments. This system consists of mechanisms that act avoiding injuries and against the action of microorganisms, among these mechanisms are antimicrobial peptides (AMPs). The aim of this study was to identify AMPs, present in the hemolymph of Tityus serrulatus. The hemolymph was extracted and then we separated hemocyte and plasma. The samples were fractionated in different concentrations of acetonitrile in TFA 0.05% (05, 40 and 80%). These fractions were subjected to high-performance liquid chromatography (HPLC) and the peaks obtained were evaluated for its antimicrobial and hemolytic action. We found sixteen fractions with antimicrobial activity. One of the fractions with antimicrobial activity, present in hemocytes, is similar with a defensin described in ticks, Ixodes scapularis. This fraction has about 3486 Da, has no hemolytic activity and was named as Serrulina.