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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Activity-dependent bulk endocytosis : control by molecules and signalling cascades

Nicholson-Fish, Jessica January 2017 (has links)
Synaptic vesicle (SV) recycling in the presynapse is essential for the maintenance of neurotransmission. During mild stimulation clathrin-mediated endocytosis (CME) dominates, however during intense stimulation activity-dependent bulk endocytosis (ADBE) is the dominant form of membrane retrieval. The aim of this thesis was to determine how the signalling molecule GSK3 controlled ADBE, with the hypothesis that this enzyme was required at multiple stages of this endocytosis mode. I also hoped to identify a specific cargo for ADBE. I found that during intense action potential stimulation, a localised calcium increase is necessary for the activation of Akt, which inhibited GSK3. This activation was mediated via a phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. Furthermore, I found that phosphatidylinositol 4-kinaseIIα (PI4KIIα), a molecule whose abundance is regulated by GSK3, had a key role in ADBE. Specifically, I found that the absence of PI4KIIα accelerated CME but inhibited ADBE and that PI4KIIα controls CME and ADBE via distinct mechanisms. The PI4KIIα study revealed potential cross-talk between CME and ADBE. To determine whether modulation of either endocytosis mode impacts on the other, the retrieval of genetically-encoded reporters of SV cargo was monitored during intense stimulation during inhibition of either CME or ADBE. The recovery of almost all SV cargo was unaffected by ADBE inhibition but was arrested by abolishing CME. In contrast, VAMP4-pHluorin retrieval was perturbed by inhibiting ADBE and not by blocking CME. Knockdown of VAMP4 also arrested ADBE, indicating that in addition to being the first identified ADBE cargo, it is also essential for this endocytosis mode to proceed.
182

Development of circulatory microRNAs as markers of organ injury and mediators of inter-organ signalling

Morrison, Emma Elisabeth January 2018 (has links)
Plasma contains small, non-protein coding RNA species, microRNAs (miRNAs). Circulating miRNAs originate from tissues throughout the body and circulate in the blood bound to proteins or encapsulated in extracellular vesicles (EVs). The pattern of circulating miRNAs changes in different pathological states, leading to the hypothesis that they could act as biomarkers or mediators of inter-organ signalling. Acute kidney injury (AKI) is associated with high morbidity worldwide. Recent work has highlighted a potential role for EV signalling in the delivery of functional exogenous miRNA into kidney cells, which may contribute to the pathogenesis of AKI. The studies described in this thesis investigate the effects of circulating miRNAs on renal proximal tubular (PT) cells. Utilising next generation sequencing technology, circulating miRNA profiles were demonstrated to change significantly following myocardial injury. These findings were translated from humans into a mouse model of myocardial injury. Investigation of EV cell signalling, using flow cytometry and nanoparticle tracking analysis, demonstrated that PT cell EV uptake was not affected by known physiological agonists. By contrast, EV release from PT cells was regulated by purinergic P2Y1 and dopamine D1 receptors. Toxic cisplatin injury of PT cells resulted in increased EV release and reduced EV uptake in a dose-dependent manner. Cisplatin toxicity in PT cells was unaffected by EVs from mice with myocardial injury, but toxicity was reduced by EVs from mice with drug-induced liver injury (DILI). Circulating EVs from mice with DILI transferred the liver specific miRNA, miR-122, into PT cells in both in vivo and in vitro models. The consequence of miR-122 transfer was modulation of downstream target genes including Foxo3 which has been implicated in cell injury by apoptosis. These findings therefore show that circulatory miRNA profiles change in different models of organ injury and suggest miRNAs can be transferred to PT cells in vivo and in vitro. The improved viability of injured PT cells following co-incubation with DILI EVs, and subsequent transcriptomic work, suggests this may be as a consequence of miRNA transfer. In conclusion, circulatory miRNAs may act as mediators of inter-organ signalling and could play a crucial role in the propagation of systemic illness.
183

Excitotoxic injury mechanisms in central white matter

Doyle, Seán P. January 2017 (has links)
Myelinated axons are crucial for rapid information transmission within the central nervous system (CNS). Myelin injury is a common feature of white matter (WM) pathology in a number of disease states, including ischemic stroke. Myelin disruption can lead to a complete failure in saltatory action potential conduction, resulting in devastating neurological deficits. However, the fundamental mechanism of ischemic myelin injury is controversial. Glutamate-mediated excitotoxicity is now recognised as a crucial event in the development of ischemic WM pathology. This thesis investigates the potential mechanisms of glutamate release in central WM and examines the hypothesis that NMDA receptor over-activation mediates ischemic myelin damage. Using glutamate biosensor microelectrodes and FM-dye imaging, I show that axonal depolarisation in the adult corpus callosum evokes rapid vesicular docking in axons, capable of elevating extracellular glutamate concentration. My findings show that vesicular fusion occurs under the myelin sheath in myelinated axons, which supports the existence of a novel synapse between the axon and overlaying myelin. Simulation of ischemia triggered an early and robust rise in optic nerve extracellular glutamate levels. Unexpectedly, a significant component of ischemic glutamate release also originated from axonal vesicular fusion. Together, these findings show that the axon-myelin synapse represents a significant site of excitotoxic injury during ischemia. Resolving prior conflicting results, I show that NMDA receptor antagonists prevent myelin degradation and improve functional recovery when applied for sufficient time to penetrate the sheath. Finally, I identify a fluorescent myelin stain (QNZ-46) which is a negative allosteric modulator of NR2C/D-containing NMDA receptors. QNZ-46 selectively accumulates in myelinated WM regions of the CNS following systemic administration, and is retained following wash-out. As a result, QNZ-46 provides persistent protection during ischemia by preserving myelin structure and improving functional recovery.
184

Identificação dos Genes, Expressão e Localização Celular do Complexo Adaptador 1 em Trypanosoma cruzi

Nascimento Moreira, Claudia Maria do January 2013 (has links)
Submitted by Renata Fontoura (comunicaicc@fiocruz.br) on 2014-11-26T15:13:12Z No. of bitstreams: 2 Dissertação Claudia Maria do Nascimento Moreira - 01.pdf: 4994656 bytes, checksum: c9acb588dbfcaa318394a1f54b594a32 (MD5) Dissertação Claudia Maria do Nascimento Moreira - 01.pdf: 4994656 bytes, checksum: c9acb588dbfcaa318394a1f54b594a32 (MD5) / Made available in DSpace on 2014-11-26T15:15:37Z (GMT). No. of bitstreams: 2 Dissertação Claudia Maria do Nascimento Moreira - 01.pdf: 4994656 bytes, checksum: c9acb588dbfcaa318394a1f54b594a32 (MD5) Dissertação Claudia Maria do Nascimento Moreira - 01.pdf: 4994656 bytes, checksum: c9acb588dbfcaa318394a1f54b594a32 (MD5) Previous issue date: 2013 / Fundação Oswaldo Cruz. Instituto Carlos Chagas. Curitiba, PR, Brasil / O complexo adaptador 1 (AP-1) atua na formação do revestimento de vesículas com clatrina na rede trans-Golgi em células eucariontes. O conhecimento sobre o complexo AP-1 em tripanosomatídeos é escasso, mas já foi demonstrada sua importância na infectividade de Leishmania mexicana em macrófagos, assim como na viabilidade de Trypanosoma brucei. O Trypanosoma cruzi é um protozoário flagelado pertencente à família Trypanosomatidae, sendo o agente etiológico da doença de Chagas, a qual afeta milhões de pessoas no mundo. Neste contexto, esta dissertação teve como objetivo identificar os genes que codificam as quatro subunidades do complexo AP-1 no genoma de T. cruzi, analisar sua expressão e localização subcelular nesse parasita. Busca em banco de dados genômicos permitiu identificar as sequências codificantes para todas as subunidades do complexo AP-1, sendo obtidos os seguintes números de acesso gênicos: AP1-γ: XP_818958.1; AP1-β: XP_820334.1; AP1-µ:XP_818899.1; AP1-σ: XP_804127.1. Foram produzidos anticorpos em camundongos contra as proteínas recombinantes de todas as subunidades do complexo AP-1. Análise da especificidade dos anticorpos foi realizada por western blot e a localização subcelular das proteínas foi feita por imunofluorescência em microscopia de epifluorescência e microscopia confocal a laser. Resultados negativos foram obtidos com o antisoro contra a subunidade AP1-σ. Anticorpos obtidos contra as subunidades AP1-µ (policlonal) e AP1-β (monoclonal) reconheceram polipetídeos de tamanho compatível ao peso molecular da proteína endógena em extratos de formas epimastigotas, porém não reconheceram as proteínas por imunofluorescência. O antisoro policlonal obtido contra a subunidade AP1-γ reconheceu em extratos de diferentes formas evolutivas de T. cruzi (epimastigotas, tripomastigotas e amastigotas) um polipeptídeo de peso molecular compatível com o predito em banco de dados (~90 kDa). Imunolocalização demonstrou reação positiva pontual em região compatível com a do complexo de Golgi deste protozoário: entre núcleo e cinetoplasto de formas tripomastigotas e entre cinetoplasto e bolsa flagelar de epimastigotas e amastigotas. Colocalização da AP1-γ com a GTPase Rab7 (marcador de complexo de Golgi em T. cruzi) confirmou a localização desta subunidade no complexo de Golgi desse parasita. Nossos resultados demonstram que as subunidades do complexo AP-1 são conservadas e expressas em T. cruzi e que pelo menos a subunidade AP1-γ possui localização celular em complexo de Golgi, similar ao que é descrito em outras células eucariontes. / The adaptor complex 1 (AP-1) acts in the formation of clathrin-coated vesicles at the transGolgi network of eukaryotic cells. Knowledge about the AP-1 complex in trypanosomatids is scarce, but it has been already demonstrated its importance in the infectivity of Leishmania mexicana in macrophages, as well as the viability of Trypanosoma brucei. Trypanosoma cruzi is a protozoan flagellate that belongs to the family Trypanosomatidae, being the etiologic agent of Chagas disease, which affects millions of people worldwide. In this context, this study aimed to identify the genes encoding the four subunits of the AP-1 complex in the genome of T. cruzi and analyze their expression and subcellular localization in this parasite. Search in genomic database identified gene sequences coding for all subunits of the AP-1 complex, the following accession numbers being obtained: AP1-γ: XP_818958.1; AP1-β: XP_820334.1; AP1-µ: XP_818899 .1; AP1-σ: XP_804127.1. Antibodies were produced in mice against recombinant proteins of all subunits of the AP-1 complex. Analysis of the specificity of the antibodies was performed by western blot and subcellular localization of the proteins by immunofluorescence was done by epifluorescence microscopy and confocal laser microscopy. Negative results were obtained with the antiserum against subunit AP1-σ. Antibodies raised against the AP1-µ (polyclonal) and AP1-β (monoclonal) subunits recognized polypeptides with size compatible to the molecular weight of the endogenous protein in extracts from epimastigotes, but no proteins could be localized by fluorescence microscopy. The antiserum polyclonal obtained against the AP1-γ subunit recognized a polypeptide in extracts of different evolutionary forms of T. cruzi (epimastigotes, trypomastigotes and amastigotes) of molecular weight consistent with that predicted in database (~90 kDa). Immunolocalization showed punctual positive reaction in the region compatible with the Golgi complex of this protozoan: between nucleus and kinetoplast of trypomastigotes and between kinetoplast and flagellar pocket of epimastigotes and amastigotes. Colocalization of AP1-γ with the GTPase Rab7 (a marker of the Golgi complex in T. cruzi) confirmed the location of this subunit in the Golgi apparatus of this parasite. Our results demonstrate that the subunits of the AP-1 complex are conserved and expressed in T. cruzi and that at least the AP1-γ subunit has cellular localization in the Golgi apparatus, similar to that described in other eukaryotic cells.
185

Efeito do tratamento local de vesiculite seminal sobre a qualidade e longevidade so sêmen equino

Silva, Yamê Fabres Robaina Sancler da [UNESP] 26 February 2014 (has links) (PDF)
Made available in DSpace on 2014-11-10T11:09:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-26Bitstream added on 2014-11-10T11:57:43Z : No. of bitstreams: 1 000789914.pdf: 1497556 bytes, checksum: 733d284c8aacfd301e7a417adb15a971 (MD5) / A vesiculite seminal possui grande relevância na clínica reprodutiva devido à dificuldade de tratamento, elevados índices de recidiva, risco de contaminação de fêmeas com agentes patogênicos, inutilização de animais e baixos índices de fertilidade. O tratamento local tem sido apontado por diversos autores como a melhor alternativa terapêutica, porém nenhum estudo avaliou seus efeitos na qualidade e longevidade seminal. Nesse sentido, os objetivos do presente estudo incluíram: investigar quais são as principais bactérias envolvidas na enfermidade e os principais fatores de risco para os garanhões; avaliar e comparar o efeito do tratamento local de vesiculite seminal quanto aos índices de cinética e morfologia espermática, integridade de membrana plasmática, porcentagem de leucócitos e contagem de unidades formadoras de colônias (UFC) de amostras seminais frescas, refrigeradas e congeladas e o teor de óxido nítrico no plasma seminal, antes (M0), após uma semana (M1) e um mês (M2) da terapia. Os resultados obtidos permitiram inferir que a vesiculite seminal foi mais prevalente em animais adultos e idosos, a evolução da enfermidade ocorreu de forma crônica em todos os animais selecionados, a monta natural constituiu um fator predisponente para o surgimento da doença, a coloração amarelada do sêmen e a dificuldade na ejaculação são sinais indicativos de alteração da glândula e a bactéria mais prevalente envolvida na etiopatogenia da infecção foi a Pseudomonas aeruginosa. De maneira geral, o tratamento local levou a uma melhora da qualidade seminal após uma semana (M1), no sêmen a fresco, refrigerado e congelado, quanto aos índices de cinética espermática e integridade de membrana plasmática (p<0,05). No sêmen a fresco promoveu redução do volume seminal, incremento da concentração espermática, redução da porcentagem de leucócitos e de UFC/mL no M1 em relação aos demais momentos ... / Seminal vesiculitis has great relevance in reproductive clinic due to the difficulty of treatment, high rates of recurrence, risk of female contamination with pathogenic agents, retirement of animals and low fertility rates. Local treatment has been reported as the best therapeutic alternative, although no other studies have evaluated its effects on seminal quality and longevity. The aims of this study included: to investigate what are the main bacteria involved in the disease and the risk factors for stallions; to evaluate and to compare the effect of local treatment of seminal vesiculitis on the sperm kinetic parameters, morphology and viability (plasma membrane integrity), percentage of leukocytes and counting colony forming units (CFU) of fresh, cooled and frozen semen samples and the content of nitric oxide in the seminal plasma, before (M0) and after one week (M1) and one month (M2) therapy. The results allow us to infer that the seminal vesiculitis was more prevalent in adults and aged animals, the evolution of the disease appeared chronically in all selected animals, natural breeding was a risk factor for onset of the disorder, the bege coulor of semen and ejaculatory dysfunction were signs indicative of abnormalities in the gland and the most common bacteria involved in the pathogenesis of the infection was Pseudomonas aeruginosa. In general, the local treatment produced an improvement in semen quality after a week (M1) in fresh, cooled and frozen semen on the kinetic parameters and sperm viability (p<0.05). In fresh semen promoted reduction in the volume of ejaculate, sperm concentration increased, reducing the percentage of leukocytes and CFU/mL in M1 compared to the other moments (p<0.05). In frozen semen promoted reduction of lipid peroxidation and of ROS content in M1 compared to other moments (p<0.05). The cooled semen for 24 hours at 5°C and 15°C demonstrated similar efficiency in the pre and post-treatment ...
186

Molecular Profiling Plasma Extracellular Vesicles From Breast Cancer Patients

January 2018 (has links)
abstract: Extracellular vesicles (EVs) represent a heterogeneous population of small vesicles, consisting of a phospholipidic bilayer surrounding a soluble interior cargo. These vesicles play an important role in cellular communication by virtue of their protein, RNA, and lipid content, which can be transferred among cells. Peripheral blood is a rich source of circulating EVs. An analysis of EVs in peripheral blood could provide access to unparalleled amounts of biomarkers of great diagnostic, prognostic as well as therapeutic value. In the current study, a plasma EV enrichment method based on pluronic co-polymer was first established and characterized. Plasma EVs from breast cancer patients were then enriched, profiled and compared to non-cancer controls. Proteins signatures that contributed to the prediction of cancer samples from non-cancer controls were created by a random-forest based cross-validation approach. We found that a large portion of these signatures were related to breast cancer aggression. To verify such findings, KIAA0100, one of the features identified, was chosen for in vitro molecular and cellular studies in the breast cancer cell line MDA-MB-231. We found that KIAA0100 regulates cancer cell aggression in MDA-MB-231 in an anchorage-independent manner and is particularly associated with anoikis resistance through its interaction with HSPA1A. Lastly, plasma EVs contain not only individual proteins, but also numerous molecular complexes. In order to measure millions of proteins, isoforms, and complexes simultaneously, Adaptive Dynamic Artificial Poly-ligand Targeting (ADAPT) platform was applied. ADAPT employs an enriched library of single-stranded oligodeoxynucleotides to profile complex biological samples, thus achieving a deep coverage of system-wide, native biomolecules. Profiling of EVs from breast cancer patients was able to obtain a prediction AUC performance of 0.73 when compared biopsy-positive cancer patient to healthy controls and 0.64 compared to biopsy-negative controls and such performance was not associated with the physical breast condition indicated by BIRAD scores. Taken together, current research demonstrated the potential of profiling plasma EVs in searching for therapeutic targets as well as diagnostic signatures. / Dissertation/Thesis / Appendix-G / Appendix-B / Appendix-C / Appendix-D / Appendix-E / Appendix-F / Doctoral Dissertation Molecular and Cellular Biology 2018
187

Efeito do tratamento local de vesiculite seminal sobre a qualidade e longevidade so sêmen equino /

Silva, Yamê Fabres Robaina Sancler da. January 2014 (has links)
Orientador: Frederico Ozanam Papa / Banca: João Carlos Pinheiro Ferreira / Banca: André Maciel Crespilho / Resumo: A vesiculite seminal possui grande relevância na clínica reprodutiva devido à dificuldade de tratamento, elevados índices de recidiva, risco de contaminação de fêmeas com agentes patogênicos, inutilização de animais e baixos índices de fertilidade. O tratamento local tem sido apontado por diversos autores como a melhor alternativa terapêutica, porém nenhum estudo avaliou seus efeitos na qualidade e longevidade seminal. Nesse sentido, os objetivos do presente estudo incluíram: investigar quais são as principais bactérias envolvidas na enfermidade e os principais fatores de risco para os garanhões; avaliar e comparar o efeito do tratamento local de vesiculite seminal quanto aos índices de cinética e morfologia espermática, integridade de membrana plasmática, porcentagem de leucócitos e contagem de unidades formadoras de colônias (UFC) de amostras seminais frescas, refrigeradas e congeladas e o teor de óxido nítrico no plasma seminal, antes (M0), após uma semana (M1) e um mês (M2) da terapia. Os resultados obtidos permitiram inferir que a vesiculite seminal foi mais prevalente em animais adultos e idosos, a evolução da enfermidade ocorreu de forma crônica em todos os animais selecionados, a monta natural constituiu um fator predisponente para o surgimento da doença, a coloração amarelada do sêmen e a dificuldade na ejaculação são sinais indicativos de alteração da glândula e a bactéria mais prevalente envolvida na etiopatogenia da infecção foi a Pseudomonas aeruginosa. De maneira geral, o tratamento local levou a uma melhora da qualidade seminal após uma semana (M1), no sêmen a fresco, refrigerado e congelado, quanto aos índices de cinética espermática e integridade de membrana plasmática (p<0,05). No sêmen a fresco promoveu redução do volume seminal, incremento da concentração espermática, redução da porcentagem de leucócitos e de UFC/mL no M1 em relação aos demais momentos ... / Abstract: Seminal vesiculitis has great relevance in reproductive clinic due to the difficulty of treatment, high rates of recurrence, risk of female contamination with pathogenic agents, retirement of animals and low fertility rates. Local treatment has been reported as the best therapeutic alternative, although no other studies have evaluated its effects on seminal quality and longevity. The aims of this study included: to investigate what are the main bacteria involved in the disease and the risk factors for stallions; to evaluate and to compare the effect of local treatment of seminal vesiculitis on the sperm kinetic parameters, morphology and viability (plasma membrane integrity), percentage of leukocytes and counting colony forming units (CFU) of fresh, cooled and frozen semen samples and the content of nitric oxide in the seminal plasma, before (M0) and after one week (M1) and one month (M2) therapy. The results allow us to infer that the seminal vesiculitis was more prevalent in adults and aged animals, the evolution of the disease appeared chronically in all selected animals, natural breeding was a risk factor for onset of the disorder, the bege coulor of semen and ejaculatory dysfunction were signs indicative of abnormalities in the gland and the most common bacteria involved in the pathogenesis of the infection was Pseudomonas aeruginosa. In general, the local treatment produced an improvement in semen quality after a week (M1) in fresh, cooled and frozen semen on the kinetic parameters and sperm viability (p<0.05). In fresh semen promoted reduction in the volume of ejaculate, sperm concentration increased, reducing the percentage of leukocytes and CFU/mL in M1 compared to the other moments (p<0.05). In frozen semen promoted reduction of lipid peroxidation and of ROS content in M1 compared to other moments (p<0.05). The cooled semen for 24 hours at 5°C and 15°C demonstrated similar efficiency in the pre and post-treatment ... / Mestre
188

Interação de poli(etileno glicol) com brometo de dioctadecildimetilamônio e didodecilmetilamônio em dispersões aquosas /

Santos, Cecilia Cristina Marques dos. January 2006 (has links)
Orientador: Eloi da Silva Feitosa / Banca: Maria Elisabete Darbello Zaniquelli / Banca: Mário José Politi / Banca: Ieda Aparecida Pastre Fertonani / Banca: Maurício Boscolo / Resumo: Poli(etilenoglicol) (PEG) é um polímero neutro hidrossolúvel, e brometo de dioctadecildimetilamônio (DODAB) e diododecildimetilamônio (DDAB) são surfactantes catiônicos dialquilados, C18 e C12, respectivamente, derivados da amônia quaternária, formadores de vesículas. As suas propriedades físicas, em solução aquosa, são bem conhecidas. No entanto, as propriedades de misturas desse polímero com esses surfactantes não o são. Investigamos a interação de PEG com DODAB e DDAB em solução aquosa, numa faixa de concentração total dos componentes até 1% em peso, e construímos diagramas de fases, com especial destaque para a fase vesicular. Utilizamos PEG com massa molecular entre 200 Da e 2 MDa e os diagramas de fases foram construídos a 25oC, isto é, acima da temperatura de transição gel-líquido cristal (Tm) de DDAB (Tm = 16oC) e abaixo da Tm de DODAB (Tm = 45oC). DODAB e DDAB têm a característica comum de formar vesículas unilamelares em baixas concentrações do surfactante e vesículas multilamelares em concentrações mais elevadas; em regiões intermediárias, vesículas uni e multilamelares coexistem em equilíbrio na solução. A fronteira entre essas regiões de vesículas não é muito bem definida e observamos, neste estudo, que o efeito de PEG na estrutura de agregados de DODAB e DDAB em água depende da massa molecular do polímero. Além disso, PEG favorece a formação de vesículas unilamelares em concentrações mais elevadas de DODAB e DDAB, quando predominam as vesículas multilamelares de DODAB puro (sem o polímero), possibilitando a formação de vesículas mistas de DODAB/PEG e DDAB/PEG em água e concentrações relativamente grandes desses surfactantes. Dentre os métodos experimentais empregados nesse estudo, destacamos, turbidimetria, fluorescência de estado estacionário, calorimetria diferencial de varredura (DSC) e por titulação isotérmica (ITC) e análise visual por polarizadores cruzados. / Abstract: Poly (ethyleneglycol) (PEG) is a water soluble neutral polymer, and dioctadecyldimethylammonium (DODAB) and diododecyldimethylammonium (DDAB) bromide are double chain cationic surfactants derived from the quaternary ammonium that have been widely investigated due to their high application potential in different areas of the science and technology. The physical properties of PEG, DODAB and DDAB in aqueous solution are well-known. However, the properties of mixtures of the polymer with those surfactants are not. We investigated the interaction of PEG with DODAB and DDAB in aqueous solution, within a range of total concentration of the components of 0-1 wt%, and the phase diagrams built up, with special interest for the vesicular phases. We used PEG with molecular mass between 200 Da and 2 MDa and the phase diagrams were built up at 25°C, that is, above the melting temperature (Tm) of DDAB (Tm = 16°C) and below Tm of DODAB (Tm = 45°C). DODAB and DDAB have the common characteristic of forming unilamellar vesicles at low surfactant concentrations and umultilamellar vesicles at higher concentrations; at intermediate concentrations, uni- and multilamellar vesicles coexist in solution. The borders of these different vesicle phases are not well defined. We observed in this Thesis that the effect of PEG on the structures of DODAB and DDAB aggregates in water depends on the molecular mass of the polymer. Besides, PEG stabilizes the unilamellar vesicles at high concentrations of DODAB, where the multilamellar vesicles are the dominant structures present in solution, thus allowing the formation of mixed DODAB/PEG and DDAB/PEG vesicles in water at relatively high concentrations of these surfactants. The experimental methods used in this investigation include turbidimetry, steady-state fluorescence, differential scanning calorimetry (DSC), isothermal titration calorimetry (ITC), and visual analysis by crossed polaroids. / Doutor
189

Quantifying passive drug transport across lipid membranes

Cama, Jehangir January 2016 (has links)
Antibiotic resistance has emerged as one of the World's leading public health challenges. The inexorable emergence of drug resistant pathogens, combined with a steep decline in antibacterial drug discovery, has led to a major crisis. One of the most common drug resistance mechanisms involves bacteria adapting to reduce intracellular drug accumulation. To understand these resistance mechanisms, one needs quantitative information about the membrane permeability of drugs. In this Thesis, we develop a novel optofluidic permeability assay that allows us to quantify the permeability coefficient of drugs crossing lipid membranes. Lipid vesicles are used as model systems and drug molecules are tracked directly using their autofluorescence in the ultraviolet. The permeability coefficient of the drug is inferred by studying the increase in drug autofluorescence intensity within vesicles as they traverse a microfluidic network while exposed to the drug for well defined times. This provides a novel platform from which we can develop membrane models for understanding drug permeability. We incorporate the Escherichia coli outer membrane protein OmpF in vesicles and quantify its role in the transport of fluoroquinolone antibiotics. We provide direct visualisation of OmpF mediated fluoroquinolone transport. We study the pH dependence of antibiotic transport both through pure phospholipid membranes and through OmpF, and present a physical mechanism to explain the pH dependence of E. coli fluoroquinolone susceptibility. We also show the importance of lipid composition on drug permeability - changing the lipid composition of the membrane is shown to change antibiotic permeability by over an order of magnitude. Finally, we report on the discovery of a novel signalling mechanism in E. coli that relies on the transport of small drug-like molecules, and discuss the role it plays in stress response in the microbial community.
190

Coencapsulação de curcumina e vitamina D3 em lipossomas multilamelares / Co-encapsulation of curcumin and vitamin D3 in multilamellar liposomes

Matheus Andrade Chaves 23 February 2017 (has links)
Atualmente, a demanda por alimentos com apelo funcional tem se tornado cada vez mais recorrente dentre os consumidores devido a uma crescente busca por hábitos de vida mais saudáveis. Sendo assim, o desenvolvimento de técnicas que possibilitem uma adição mais efetiva de ingredientes funcionais em matrizes alimentícias se torna uma necessidade. Essas técnicas devem possibilitar principalmente (i) a incorporação de mecanismos de liberação sustentada na formulação; (ii) o aumento da bioacessibilidade e biodisponibilidade aos ingredientes, a partir do controle da microestrutura do alimento. Esse projeto visa contemplar essas duas premissas, ao propor a encapsulação de dois bioativos hidrofóbicos, a curcumina e a vitamina D3, conhecidos pelas suas propriedades antioxidantes e nutracêuticas, em carreadores de origem lipídica, os lipossomas, estabilizando-os com diferentes hidrocoloides - goma xantana, goma guar e inulina. Os lipossomas foram produzidos por hidratação de prolipossomas e suas propriedades físico-químicas foram caracterizadas ao longo de 42 dias de armazenagem, a partir de análises de diâmetro médio hidrodinâmico, potencial zeta, colorimetria instrumental e quantificação de bioativos encapsulados. Análises que permitiram a caracterização da microestrutura das dispersões produzidas também foram realizadas, sendo elas: calorimetria diferencial de varredura (DSC), espalhamento de raios-X a baixos ângulos (SAXS) e ensaios reológicos. As análises de SAXS mostraram que lipossomas produzidos na presença de curcumina são mais estáveis que àqueles produzidos na ausência da mesma e que não houve mudança na estrutura da bicamada lipídica das vesículas após a adição de vitamina D3, mesmo quando uma alta concentração foi incorporada ao sistema (80.000 UI). Por fim, verificou-se que a coencapsulação foi possível em lipossomas multilamelares estabilizados apenas com gomas guar e xantana, resultado que pode ser comprovado pelo alto teor de retenção dos bioativos ao longo do tempo de armazenagem. / Currently, the demand for food with functional appeal has become increasingly recurrent among the consumers due to a growing search for healthier living habits. Therefore, the development of techniques that allow a more effective addition of functional ingredients in food matrices becomes a necessity. These techniques should mainly enable to (i) incorporate a sustained release mechanisms into the formulation; (ii) increase the bioaccessibility and bioavailability to these ingredients, from the control of the food microstructure. This project aims to contemplate these two premises by proposing the encapsulation of two hydrophobic bioactives, curcumin and vitamin D3, known for their antioxidant and nutraceutical properties, in liposomes - lipid carriers - stabilizing them with different hydrocolloids - xanthan gum, guar gum and inulin. Liposomes were produced by proliposomes hydration and their physicochemical properties were characterized during 42 days of storage, including analyzes of hydrodynamic average diameter, zeta potential, instrumental colorimetry and quantification of encapsulated bioactives. Analyzes that allowed the microstructure characterization of the produced dispersions were also performed, including: differential scanning calorimetry (DSC), small-angle X-ray scattering and rheological tests. The SAXS analysis showed that liposomes produced in the presence of curcumin were more stable when compared to the empty ones and that there was no change in the lipid bilayer of the vesicles after the addition of vitamin D3, even when a high concentration was incorporated into the system (80,000 IU). Finally, it was concluded that the coencapsulation was possible in multilamellar liposomes stabilized with guar and xanthan gums, a result that can be evidenced by the high content of bioactives retained throughout the storage time.

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