Delisea pulchra is a red macroalga that produces furanones, a class of secondary metabolites that inhibit the growth and colonization of a range of micro- and macroorganisms. In bacteria, furanones specifically inhibit acyl homoserine lactone (AHL)- driven quorum sensing, which is known to regulate a variety of colonization and virulence traits. This thesis aims to unveil multiple aspects of the chemically mediated interactions between an alga and its bacterial flora. It was demonstrated that the quorum sensing genetic machinery of bacteria is laterally transferred, making traditional 16S rRNA gene based-diversity techniques poorly suited to identify quorum sensing species. Previous studies had shown that AHL-producing bacteria belonging to the roseobacter clade can be readily isolated from D. pulchra. Because of this, it was decided to use a roseobacter epiphytic isolate from this alga, Ruegeria strain R11, to conduct a series of colonization experiments on furanone free and furanone producing D. pulchra. Furanones were shown to inhibit Ruegeria strain R11's colonization and infection of D. pulchra. In addition, it was demonstrated that Ruegeria strain R11 has temperature-regulated virulence, similar to what is seen for the coral pathogen Vibrio shiloi. Rising ocean temperatures may explain bleached D. pulchra specimens recently observed at Bare Island, Australia. To assess whether quorum sensing is common within the roseobacter clade, cultured isolates from the Roseobacter, Ruegeria and Roseovarius genera were screened for AHL production. Half of the bacteria screened produced the quorum sensing signal molecules, AHLs. These AHLs were identified using an overlay of an AHL reporter strain in conjunction with thin layer chromatography (TLC). The prevalence of quorum sensing within the roseobacter clade, suggests that these species may occupy marine niches where cellular density is high (such as surface associated communities on substratum and marine eukaryotes). Diversity studies in marine microbial communities require appropriate molecular markers. The 16S rRNA gene is the most commonly used marker for molecular microbial ecology studies. However, it has several limitations and shortcomings, to which attention has been drawn here. The rpoB gene is an alternate ???housekeeping??? gene used in molecular microbial ecology. Therefore, the phylogenetic properties of these two genes were compared. At most taxonomic levels the 16S rRNA and rpoB genes offer similar phylogenetic resolution. However, the 16S rRNA gene is unable to resolve relationships between strains at the subspecies level. This lack of resolving power is shown here to be a consequence of intragenomic heterogeneity.

[Truncated abstract] Melanoma cell adhesion molecule (MCAM) is highly expressed in more than 70% of metastatic melanoma and is correlated with invasive potential. However, the specific contribution MCAM makes to invasion and metastasis in melanoma is not clear. In this study, I have demonstrated that transfection of MCAM into MCAM-negative melanoma and CHO cells leads to changes in cell shape, and the modulation of cell-to-cell and cell-matrix interactions. MCAM positive cells were slower to spread on collagen type I, collagen type IV and laminin 1 than MCAM negative cells, although these differences were not apparent on vitronectin, fibronectin and laminin 10. In contrast, MCAM expression had little effect on cell adhesion to any of the matrices tested. MCAM positive (compared to negative) cells also showed morphological changes and a rearrangement of the actin cytoskeleton when plated on a matrix containing laminin 5. Taken together, these data suggest that MCAM expression modulates β1-integrinmediated spreading on matrix, but has little effect on αvβ3-mediated cell-matrix interactions. As this study provided little evidence to suggest that MCAM transfection altered β1 integrin expression levels on melanoma cells, it is proposed that a competitive interaction between the cytoplasmic domains of MCAM and β1 integrin may affect mature focal adhesion assembly. MCAM expression in melanoma cells was also associated with decreased cell movement over matrix into a scratch-wound site and an increased tendency to form cell cords on Matrigel. These two assays gauge the propensity of a cell to engage in cell-cell versus cell-matrix interactions, and suggest that MCAM positive cells favour cell-cell adhesion. Interestingly, MCAM transfection was also associated with an increased ability of melanoma cells to migrate through a basement membrane towards a chemoattractant. ... Analysis of the intracellular domain of MCAM revealed the presence of tyrosine and dileucine endocytosis signals. Interestingly, disruption of these two motifs did not seem to impair the internalization of MCAM from the cell surface. The di-leucine motif, however, was necessary for the recycling of MCAM back to the surface following endocytosis. Lastly, MCAM was found to exists as dimers within the cell membrane in the absence of ligand, although the exact location of the dimerization motif is not yet clearly defined. Collectively, findings from my study suggest: MCAM expression in melanoma cells facilitates cell-cell interactions, whilst concomitantly modulating cell-matrix interactions. MCAM transfection also leads to enhanced migration of melanoma cells through a basement membrane. Thus, MCAM expression may increase the ability of melanoma cells to migrate as a collective, a feature of highly invasive cancer. The intracellular domain of MCAM interacts with ApxL2, a novel member of the Shroom family of actin-binding proteins. It is likely that ApxL2 links a proportion of MCAM within the cell to the actin cytoskeleton, contributing to cell shape determination and other processes, such as migration. MCAM exists as dimers on the cell surface and is internalized at least partially by a clathrin-mediated mechanism.

Orientador: Prof. Dr. Anderson Orzari Ribeiro / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2015. / O cancer e uma doenca caracterizada pelo crescimento desordenado de celulas com potencial invasivo. Diversos tratamentos podem ser empregados para a doenca, dentre eles, a terapia fotodinamica, pela qual se utiliza, como agentes terapeuticos, um fotossensibilizador (FS), luz em comprimento de onda especifico e oxigenio. Este projeto tem como principal objetivo o estudo biologico de novos derivados de ftalocianinas para o emprego como fotossensibilizadores em Terapia Fotodinamica. Foram estudados macrociclos com ligantes perifericos derivados do acido glicolico ou do acido latico, e que contem zinco ou rutenio como atomo central sintetizados pelo grupo sobre uma linhagem de adenocarcinoma mamario humano (MCF7). Nos estudos com irradiacao de luz verificamos uma diminuicao da porcentagem de celulas viaveis, sendo os compostos pouco toxicos no escuro, podendo-se utilizar desde concentracoes baixas como 1 ¿ÊM ate concentracoes altas como 100 ¿ÊM. Observamos que quanto maior o tempo de contato entre os compostos e as celulas (no escuro), mais toxico se torna o composto, sendo o melhor tempo de incubacao de 2 horas, isto se deve aos efeitos agudos ocasionados por esta exposicao. Comparando as quatro ftalocianinas estudadas, concluimos que a estrutura que contem acido glicolico e zinco como metal central foi a que apresentou resultados mais promissores em todos os aspectos, principalmente nas analises de fototoxicidade que se relacionam a Terapia Fotodinamica, sendo que a viabilidade em relacao ao controle decaiu aproximadamente 50%. Pelos dados obtidos, pode-se inferir que, em uma unica sessao de irradiacao de luz, a morte celular foi de aproximadamente 20 a 30% para todas as ftalocianinas estudadas. / Cancer is a disease characterized by uncontrolled growth of cells. Some treatments are actually employed for the disease, including photodynamic therapy, which uses, as therapeutic agents, a photosensitizer (PS), light at a specific wavelength and the oxygen molecule near or inside the cells. In this project, the main objective is to study new phthalocyanine derivatives for their use as photosensitizers in photodynamic therapy. We studied phthalocyanines modified with glycolic or lactic acid in their peripheral positions, and with zinc or ruthenium as a central metal synthesized by our group on a human mammary adenocarcinoma line (MCF7). Our results revealed a good phototoxicity under irradiation and a low toxicity in the dark for all the studied compounds, from low concentrations such as 1 uM to the higher ones such as 100 uM. Comparing the studied phthalocyanines, we conclude that the structure containing glycolic acid and zinc as the central metal showed the most promising results in all aspects, especially in phototoxicity tests, where we observed a decrease in about 50% of cell viability after irradiation. According with our results, a single light irradiation session can promote approximately 20 to 30% of cell death for all studied phthalocyanines.

Este estudo teve como objetivo avaliar a expressão hipocampal de proteínas e de RNAm das Cx43 e Cx36 no modelo de epilepsia do lobo temporal (ELT) induzido por pilocarpina. Além disso, os efeitos do bloqueador de canais de junções comunicantes (CJC), carbenoxolona (CBX), foram avaliados por eletrofisiologia durante o período de status epilepticus. Os dados referentes à Cx43 demonstraram redução dos níveis proteicos no período latente (p<0,05) e aumento no período crônico do modelo (p<0,01). Os níveis de RNAm de Cx43 não sofreram alterações. Tanto os níveis proteicos quanto os de RNAm de Cx36 não se alteraram. Os dados eletrofisiológicos mostraram redução da potência na banda de frequência entre 15 e 30 Hz no eletrocortigrama, além de redução da amplitude relativa dos potenciais epileptiformes. Foi observado ainda que o grupo tratado com CBX passou a apresentar períodos flat antecipadamente. Os dados deste estudo sugerem um importante papel dos CJC na ELT induzida por pilocarpina, contribuindo para o conhecimento da regulação destes canais na epilepsia. / In this study, the hippocampal protein and mRNA levels of Cx43 and Cx36 were investigated in the pilocarpine model of temporal lobe epilepsy (TLE). In addition, the effects of a gap junction (GJ) blocker (carbenoxolone-CBX) on pilocarpine-induced status epilepticus (SE) were also evaluated by electrophysiological recordings. Our results on Cx43 showed reduction of protein levels in the latent period (p<0.05) and increase in the chronic period of the model (p<0.01), whereas no changes were observed in the mRNA levels. Both protein and mRNA levels of Cx36 showed no changes. The electrophysiological recordings indicated that CBX promoted a marked reduction of power in the 15-30 Hz electrocorticographic frequency. Decrease in the amplitude of the epileptiform potentials was also seen, in addition to anticipation of occurrence of flat periods in the group treated with CBX. Data obtained from this study suggest an important role for GJ channels in the pilocarpine-induced TLE, contributing to a greater understanding of the regulation of these channels in the epilepsy.

The effects of MF exposure on the chemically induced production of NPY mRNA in the rat pheochromocytoma, PC-12 cell line.

The two main themes in this thesis are the implementation of interference methods with optically trapped particles for measurements of position and optical phase (optical interferometric metrology) and the optical manipulation of nanoparticles for studies in the assembly of nanostructures, nanoscale heating and nonlinear optics (nanophotonics). The first part of the thesis (chapter 1, 2) provides an introductory overview to optical trapping and describes the basic experimental instrument used in the thesis respectively. The second part of the thesis (chapters 3 to 5) investigates the use of optical interferometric patterns of the diffracting light fields from optically trapped microparticles for three types of measurements: calibrating particle positions in an optical trap, determining the stiffness of an optical trap and measuring the change in phase or coherence of a given light field. The third part of the thesis (chapters 6 to 8) studies the interactions between optical traps and nanoparticles in three separate experiments: the optical manipulation of dielectric enhanced semiconductor nanoparticles, heating of optically trapped gold nanoparticles and collective optical response from an ensemble of optically trapped dielectric nanoparticles.

A lipoproteína de baixa densidade (LDL) pode sofrer modificações, oxidativas ou enzimáticas, gerando compostos, lipídicos e proteicos, capazes de interagir com macrófagos, contribuindo para a resposta inflamatória presente na aterosclerose. Os macrófagos interagem tanto com LDL contendo baixo ou alto grau de oxidação (LoxLDL e HoxLDL) e também com fragmentos proteicos provenientes da ApoB-100, os quais podem exercer efeitos biológicos em macrófagos, contribuindo para a formação de células espumosas. Neste trabalho demonstramos que formas modificadas da LDL interagem com monócitos e/ou macrófagos, dependendo do grau de oxidação. A expressão de FcgRII por HoxLDL em macrófagos é dependente de PPARg. Parte da expressão de CD36 induzida por LoxLDL e HoxLDL em macrófagos é dependente de PAF-R. A LoxLDL induz uma maior produção de IL-6 e IL-8. Já, a HoxLDL de TNF-a, IL-10 e TGF-b em macrófagos. Encontramos um peptídeo da ApoB-100 é capaz de aumentar o fluxo intracelular de cálcio, ativar a via das MAP quinases em monócitos humanos, induzindo a produção de IL-8. / The Low Density Lipoprotein (LDL) may undergo oxidative or enzymatic modifications, producing lipid or proteic compounds that interact with macrophages, contributing to inflammatory response in the atherosclerosis. Into the arterial intima, the macrophages interact with minimally modified LDL (LoxLDL) and with highly oxidized LDL (HoxLDL). Moreover, in the arterial intima, enzymes may induce cleavage of the apoB-100, releasing protein fragments, which may have biological effects on macrophages. In this study, we showed that modified forms of LDL interact with monocytes or macrophages, depending on oxidation degree. The expression of FcgRII-induced HoxLDL in macrophages is dependent on PPARg and part of the expression of CD36 induced by LoxLDL and HoxLDL in macrophages is dependent on PAF-R. In macrophages, LoxLDL induced higher production of IL-6 e IL-8, whereas HoxLDL induced TNF-a, IL-10 e TGF-b. Furthermore, we found one peptide from apoB-100 capable to increase calcium flux and activate MAP kinase pathway, inducing production of IL-8 in human monocytes.

A lipoproteína de baixa densidade (LDL) pode sofrer modificações, oxidativas ou enzimáticas, gerando compostos, lipídicos e proteicos, capazes de interagir com macrófagos, contribuindo para a resposta inflamatória presente na aterosclerose. Os macrófagos interagem tanto com LDL contendo baixo ou alto grau de oxidação (LoxLDL e HoxLDL) e também com fragmentos proteicos provenientes da ApoB-100, os quais podem exercer efeitos biológicos em macrófagos, contribuindo para a formação de células espumosas. Neste trabalho demonstramos que formas modificadas da LDL interagem com monócitos e/ou macrófagos, dependendo do grau de oxidação. A expressão de FcgRII por HoxLDL em macrófagos é dependente de PPARg. Parte da expressão de CD36 induzida por LoxLDL e HoxLDL em macrófagos é dependente de PAF-R. A LoxLDL induz uma maior produção de IL-6 e IL-8. Já, a HoxLDL de TNF-a, IL-10 e TGF-b em macrófagos. Encontramos um peptídeo da ApoB-100 é capaz de aumentar o fluxo intracelular de cálcio, ativar a via das MAP quinases em monócitos humanos, induzindo a produção de IL-8. / The Low Density Lipoprotein (LDL) may undergo oxidative or enzymatic modifications, producing lipid or proteic compounds that interact with macrophages, contributing to inflammatory response in the atherosclerosis. Into the arterial intima, the macrophages interact with minimally modified LDL (LoxLDL) and with highly oxidized LDL (HoxLDL). Moreover, in the arterial intima, enzymes may induce cleavage of the apoB-100, releasing protein fragments, which may have biological effects on macrophages. In this study, we showed that modified forms of LDL interact with monocytes or macrophages, depending on oxidation degree. The expression of FcgRII-induced HoxLDL in macrophages is dependent on PPARg and part of the expression of CD36 induced by LoxLDL and HoxLDL in macrophages is dependent on PAF-R. In macrophages, LoxLDL induced higher production of IL-6 e IL-8, whereas HoxLDL induced TNF-a, IL-10 e TGF-b. Furthermore, we found one peptide from apoB-100 capable to increase calcium flux and activate MAP kinase pathway, inducing production of IL-8 in human monocytes.

Sowohl in Süßwasserseen als auch in marinen Gewässern kommt es immer wieder zu Massenentwicklungen von Cyanobakterien, sogenannten “Blüten”. In Seen werden diese oftmals von Cyanobakterien der Gattung Microcystis dominiert, deren Arten häufig Toxine bilden. Die verbreitesten dieser Toxine sind die leberschädigen Microcystine, die eine Klasse nichtribosomal synthetisierter Peptide darstellen. Nachdem die toxische Wirkung der Microcystine bisher als deren Hauptfunktion angesehen wurde, deuten neuere Forschungsergebnisse darauf hin, dass Microcystine eine andere Primärfunktion für die Produzenten besitzen. Im Rahmen dieser Studie wurde Microvirin (Mvn), ein putatives Lektin aus Microcystis aeruginosa PCC 7806, von dem angnommen wurde, dass es funktional mit Microcystin assoziiert ist, charakterisiert. Zunächst konnte gezeigt werden, dass Mvn tatsächlich zuckerbindende Aktivität besitzt und spezifisch Mannan, ein Oligosaccharid aus Mannoseuntereinheiten, erkennt. Bindestudien zeigten, dass Zucker dieses Typs auf der Zelloberfläche von M. aeruginosa PCC 7806 lokalisiert sind und eine Bindestelle für das sekretierte Mvn darstellen. Mit Hilfe fluoreszenzmikroskopiebasierender Methoden wurde gezeigt, dass sowohl Mvn als auch das korrespondierende Mannanoligosaccharid stammspezifisch sind. Weiterhin konnte durch PCR gezeigt werden, dass das mvn-Gen in allen getesteten Microcystis-Stämmen vorkommt, die auch Gene für die Microcystinbiosynthese besitzen. Eine direkte Interaktion von Microcystin und Mvn konnte in vitro bestätigt werden. Microcystin bindet dabei über seinen N-Methyl-Dehydroalaninrest kovalent an die reduzierten Cysteinreste des Proteins. Ein Einfluss auf die Oligomerisierung des Proteins wurde festgestellt. Microcystin bindet an Cysteinreste von Proteinen, und es konnte gezeigt werden, dass dies besonders unter oxidativen Stressbedingungen geschieht. Die Daten liefern somit weitere Indizien für eine Rolle von Microcystin in der Stressadaptation. / Cyanobacteria frequently appear as so-called “water-blooms” during summer months. Cyanobacteria of the genus Microcystis, whose species often dominate freshwater lakes, produce toxins that represent a potential threat for humans and animals. The most prominent toxins are the non-ribosomally synthesised hepatotoxic microcystins. Toxicity has been considered the main function of these peptides, but recent studies propose different primary functions of microcystins for their producers. The involvement of microcystins in the response to oxidative stress was proposed recently. Within this study the putative lectin microvirin (Mvn), which was suggested to be functionally related to microcystin, was characterised. Initially it was shown that Mvn does indeed possess a carbohydrate binding activity, and specificity for mannan, an oligosaccharide made of mannose subunits, was proven. Binding studies using fluorescence-labelled Mvn and antibodies identified carbohydrates of this type at the cell surface of M. aeruginosa being a binding site for the secreted Mvn. Fluorescence microscopy techniques were employed to show that Mvn as well as the corresponding mannan oligosaccharide are strain-specific. Additionally it was shown by PCR that the mvn gene is present in all tested Microcystis strains possessing microcystin biosynthesis genes. A direct interaction of microcystin and Mvn was confirmed in vitro. Microcystin covalently binds to the reduced cysteine residues of the protein via its N-methyl-dehydroalanine moiety. An impact on the oligomerisation state of Mvn was observed. Microcystin seems to bind cysteine residues in an unspecific manner in vivo, and it was shown that this occurs especially under conditions of oxidative stress such as iron depletion and exposition to high light. Hence, the data provide further evidence for an involvement of microcystins in stress adaptation.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 191-209).