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For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling agent. Traditional studies have addressed the improvement of adhesion between components of wood thermoplastic composites through the use of coupling agents such as maleated PO. The objective of this study was to increase adhesion between wood and PO through reactive processing conditions of steam-explosion. PO characteristics, such as type (polyethylene or polypropylene), form (pellet, fiber, or powder) and melt viscosity were studied along with oxygen gas content of the steam-explosion reactor vessel. Modification of co-processed wood fiber was characterized in four studies: microscopy analysis of dispersion of PO with wood fiber, sorption properties of co-processed material, chemical analysis of fractionated components, and morphological investigation of co-processed material. Two additional studies are listed in the appendices that relate to adsorption of amphiphilic polymers to the cellulose fiber surface, which is one hypothesis of fiber surface modification by co-steam-explosion. Microscopy studies revealed that PO melt viscosity was found to influence the degree of dispersion and uniformity of the steam-exploded material. The hygroscopic nature of the co-processed fiber declined as shown by sorption isotherm data. Furthermore, a water vapor kinetics study found that all co-refined material had increased initial diffusion coefficients compared to the control fiber. Chemical changes in fractionated components were PO-type dependent. Lignin extracted from co-processed wood and polyethylene showed PO enrichment determined from an increase of methylene stretching in the Fourier Transform infrared subtraction spectra, while lignin from co-processed wood and polypropylene did not. Additionally, extracted PO showed indirect signs of oxidation as reflected by fluorescence studies. Solid state nuclear magnetic resonance spectroscopy revealed a number of differences in the co-processed materials such as increased cellulose crystallinity, new covalent linkages and an alternative distribution of components on the nanoscale reflected in the T1Ï relaxation parameter. Steam-explosion was shown to modify wood fiber through the addition of "non-reactive" polyolefins without the need for coupling agents. In light of these findings, co-refining by steam-explosion should be viewed as a new reactive processing method for wood thermoplastic composites. / Ph. D.

Background: Syllids are a species rich annelid family possessing remarkable regenerative ability, which is not only the response after traumatic injury, but also a key step during the life cycle of several syllid taxa. In these animals the posterior part of the body becomes an epitoke and is later detached as a distinct unit named stolon. Such a sexual reproductive mode is named schizogamy or stolonization. The prostomium and the proventricle, a modified foregut structure, have been proposed to have a control function during this process, though the concrete mechanisms behind it have never been elucidated. Results: By using different experimental set-ups, histology and immunohistochemistry combined with subsequent cLSM analyzes, we investigate and document the regeneration and stolonization in specimens of Typosyllis antoni that were amputated at different levels throughout the antero-posterior body axis. The removal of the anterior end including the proventricle implies an incomplete anterior regeneration as well as severe deviations from the usual reproductive pattern, i.e. accelerated stolonization, masculinization and the occurrence of aberrant stolons. The detailed anatomy of aberrant stolons is described. A histological study of the proventricle revealed no signs of glandular or secretory structures. The ventricle and the caeca are composed of glandular tissue but they are not involved in the reproductive and regenerative processes. Conclusions: As in other investigated syllids, the proventricle region has a significant role during stolonization and reproduction processes in Typosyllis antoni. When the proventricle region is absent, anterior and posterior regeneration are considerably deviated from the general patterns. However, proventricle ultrastructure does not show any glandular component, thereby questioning a direct involvement of this organ itself in the control of reproduction and regeneration. Our findings offer a comprehensive starting point for further studies of regeneration and reproductive control in syllids as well as annelids in general.

Escapin is an L-amino acid oxidase that produces antimicrobial metabolites collectively called “Escapin Intermediate Products” (EIP-K). EIP-K and H2O2 together were previously shown to be bactericidal towards diverse planktonic bacteria. The present work investigates the ability of EIP-K and H2O2 to antagonize bacterial biofilms, using Pseudomonas aeruginosa as a model. The project had three aims: 1) determine the most effective concentrations of EIP-K and H2O2 necessary to break down existing P. aeruginosa biofilms, using a crystal violet assay; 2) examine the ability of EIP-K + H2O2 to inhibit biofilm formation, using triphenyl tetrazolium chloride dye; and 3) determine the effect of EIP-K + H2O2 on the viability, biomass and structure of biofilms cultivated in flow cells using confocal laser scanning microscopy (CLSM). Results showed that EIP-K + H2O2 significantly reduced biofilm biomass relative to controls and that the compounds are effective at nanomolar concentrations.

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Les biofilms sont des communautés de microorganismes adhérant à une surface et encastrées dans une substance polymérique produite par les cellules du système, dite matrice extracellulaire. Du fait de leur nature ubiquitaire, les biofilms colonisent de nombreux environnements et causent souvent de sérieux problèmes dans les secteurs de la santé et de l’industrie. La dispersion par ajout d’agent chimique est l’une des stratégies de lutte contre les biofilms. Un acide gras, l’acide cis-2-décénoique (CDA), semble être prometteur pour ce faire, grâce à l’étendue de son action dispersante sur les espèces et règnes du vivant. L’objectif de ce travail de thèse est d’investiguer les mécanismes de dispersion des biofilms de l’espèce bactérienne Escherichia coli (E. coli) par la molécule modèle CDA. Le CDA modifie-t-il les structures du biofilm ou induit-il une réponse génétique des bactéries lors de la dispersion ? Pour répondre à ces questions, la dispersion des biofilms d’E. coli a été étudiée in situ dans des chambres microfluidiques par microscopie confocale à balayage laser (CLSM). Des souches bactériennes spécifiques ont été construites par clonage de promoteurs d’intérêt en fusion transcriptionnelle avec un gène codant pour une protéine fluorescente verte. Les résultats confirment l’activité dispersante du CDA avec une réduction significative de la biomasse, de l’épaisseur moyenne et de l’aire de recouvrement par couche du biofilm. Un outil innovant d’analyse d’images CLSM a été développé en collaboration dans le but de déterminer les propriétés structurales du biofilm et l’intensité de fluorescence in situ du rapporteur étudié. Les résultats indiquent une augmentation de l’intensité moyenne de fluorescence des biofilms après dispersion avec le CDA, au niveau global en considérant tout le biofilm et au niveau local en considérant une segmentation du biofilm en microcolonies, ainsi qu’en profondeur. Ces résultats évoquent un changement d’expression génique des bactéries en présence de CDA. Par ailleurs, les résultats montrent que le CDA ne semble pas avoir d’effet en culture planctonique, ni sur la croissance bactérienne ni sur l’activité des promoteurs sélectionnés. Ceci suggère que les effets du CDA sont biofilm-dépendants. / Biofilms are microbial communities adhering to a surface and embedded in a self-produced polymeric substance, called extracellular matrix. By being ubiquitous in nature, biofilms colonize numerous environments, and they often cause serious problems for both health and industry sectors. Dispersion is one of the strategies for fighting biofilms. A fatty acid, cis-2-decenoic acid (CDA), seems to be promising for dispersing biofilms by the extent of its action on different species of microbes. The aim of this thesis work is to investigate the mechanisms of biofilm dispersion of the bacterial species Escherichia coli (E. coli) by the model molecule CDA. Does CDA modify the biofilm structures or does it induce a genetic response from bacteria during dispersion? To answer these questions, E. coli biofilm dispersal has been studied in situ in microfluidic chambers by confocal laser scanning microscopy (CLSM). Specific bacterial strains have been developed by cloning promoters of interest in transcriptional fusion with a gene encoding for a green fluorescent protein. The results confirm the dispersing activity of CDA with a significant decrease of biomass, biofilm average thickness and area over biofilm depth. A novel tool for analyzing CLSM images has been developed in collaboration in order to measure the biofilm structural properties as a function of in situ fluorescence intensity of the studied reporter. The results indicate an increase in the mean fluorescence intensity of the biofilms after dispersion with CDA, at a global level for the whole biofilm and at a local scale by considering a biofilm segmentation into microcolonies. These results evoke a change in gene expression by bacteria in the presence of CDA. Furthermore, the results show that CDA does not seem to have an effect on planktonic bacteria, neither on the bacterial growth nor on the activity of the selected promoters. This suggests that the CDA effects are biofilm-dependent.

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No description available.

4 Abstract The present thesis focuses on testate amoebae (TA) and their relationship to their natural environment, as well as on relevant microscopic imaging methods. The bulk of the data has been published in original scientific papers and is compiled into three separate chapters (Pt I, Pt II and Pt III), each annotated by a brief introduction. (Pt I) The methods section is devoted to specialized microscopic techniques employed to broaden the scope of the ecological analyses. In particular, precise discrimination between live and dead individuals, biomass determination inside individual tests and a multi-modal visualization of the cytoplasm and organelles enhance the data. Laser scanning confocal microscopy and two-photon microscopy are the main imaging modalities employed to study TA morphology in detail. The data have implications for taxonomy and ecophysiology, including the use of TA as bioindicators of pollution. (Pt II) An actuoecological analysis focuses on the seasonal variability of TA species composition in a freshwater ecosystem, namely the Komo any ponds in Prague, during the course of the year. The species composition variation is correlated to simultaneously recorded limnological parameters such as temperature, pH, contamination by (heavy) metals (As, Cd, Mn, Ni, Fe, Pb), polycyclic aromatic...

O objetivo deste estudo in vitro foi avaliar o potencial erosivo de suco de fruta amazônica ácida sobre a superfície dentinaria associado ao efeito abrasivo de diversos cremes dentais contendo agentes dessensibilizantes. O trabalho foi dividido em 3 fases distintas: Na fase 1, o valor do pH inicial de diversas frutas amazônicas foi medido utilizando 50 ml de cada suco, obtido de polpa industrializada. Foi utilizado um eletrodo de pH calibrado e a água destilada foi utilizada como controle. Na fase 2, 120 espécimes de dentina bovina foram submetidos a ciclos alternados de desafio abrasivo e erosivo, com a fruta escolhida na fase 1. Os espécimes foram divididos aleatoriamente em Grupo A (Desafio Abrasivo) e Grupo B (Desafio Erosivo e Abrasivo). Cada um destes grupos foram subdivididos em 5 subgrupos: 1: Água Destilada (Controle Negativo), 2: Colgate Tripla Ação (Controle Positivo), e os demais de acordo com o creme dental utilizado 3: Sensodyne Rápido Alívio, 4: Colgate Pró-Alivio e 5: Sensodyne Repair&Protect, (n=9). Na fase 3 foi realizado microscopia eletrônica de varredura para avaliar qualitativamente os espécimes (n=3). - O suco da fruta taperebá (Spondias mombin) apresentou os menores valores de pH, diante disso, foi escolhido como agente erosivo; Os testes de Kruskall Wallis e Teste de Dunn, mostraram que para os grupos nos quais somente a abrasão foi realizada, todos os cremes dentais mostraram comportamentos semelhantes em relação a perfilometria, não havendo diferença estatisticamente significante entre os grupos. Porém, para os grupos nos quais o processo erosivo foi adicionado, observou-se a potencialização do processo abrasivo, sendo que os cremes dentais Sensodyne Rápido Alivio e Colgate Sensitive Pro-Alivio foram os que mostraram menores alterações superficiais no padrão de perfilometria, comparados com o grupo controle negativo. Já os cremes dentais, Colgate Tripla Ação (controle positivo) e Sensodyne Repair&Protect apresentaram-se semelhantes entre si e com uma perda de estrutura dentinaria. mais significante. Conclui-se que o efeito erosivo da fruta amazônica taperebá é fator de grande importância na potencialização do efeito abrasivo, mesmo quando do uso de cremes dentais com agentes dessensibilizantes.. Na análise qualitativa da superfície dentinária em MEV, com exceção do Colgate tripla ação, os demais grupos não apresentaram oclusão tubular após o desafio ácido / The aim of this in vitro study was to evaluate the erosive potential of amazonian fruit juice with or without the abrasive challenge with various toothpastes containing desensitizing agents. The work was divided into three phases: in phase 1, the pH of various Amazonian fruits was evaluated. In step 2 it was performed surface perfilometry of the specimens, and in phase 3 it was evaluated qualitatively the dentin surface. In step 1, the initial pH value of several amazonian fruits was measured using 50 mL of each juice, from industrialized pulp. It was used a calibrated pH electrode, and distilled water was used as control. In step 2, 120 bovine dentin specimens were subjected to alternate cycles of abrasive and erosive challenge, with the fruit chosen in step 1. The specimens were randomly divided into Group A (without erosion) and Group B (with erosion). Each of these groups were divided into 5 groups: 1: Distilled Water, 2: Colgate Tripla Ação, 3: Sensodyne Rápido Alívio, 4: Pro-Alivio, 5: Sensodyne Repair & Protect, (n = 9). In Phase 3 it was conducted scanning electron microscopy to evaluate qualitatively the specimens (n=3). As a result it can be stated that: 1. The juice of the taperebá fruit had the lowest pH values, so it was chosen as the erosive agent; 2. For the groups in which only the abrasion was performed, all toothpastes showed similar behaviors, no statistically significant difference was observed between groups, but for the groups in which the erosion process was added, there was a potentiation of the abrasive process, and the toothpastes showed different profiles. The toothpaste Sensodyne Rapido Alívio Pró-Alívio was the ones that showed lower mineral loss, compared with the negative control group. Colgate Tripla Ação and Sensodyne Repair&Protect were similar among themselves and with a more significant mineral loss. It can be conclude that erosive effect of diet is a factor of great importance in the potentiation of abrasive effect. Clinical studies are essential to determine the dentin hypersensitivity levels after use of toothpaste used.