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Synthesis and Processing of Polymers for Biomedical ApplicationsDai, Xiaoshu 20 December 2010 (has links)
"In situ polymerizing hydrogel systems play an important role in many tissue engineering applications. They have proven to be useful in biomedical applications that require conversion of liquid macromer solution to tissue compliant hydrogel under physiological conditions. A series of poly(ethylene glycol)-co-poly(lactate) diacrylate macromers were synthesized with variable PEG molecular weight and lactate content. The macromer compositions were confirmed by NMR spectroscopy and ion chromatography. These macromers were polymerized to form hydrogels by free radical polymerization using either redox or photochemical initiators. The current study focused on the optimization of polymerization conditions. Compressive modulus and residual acrylate analysis were used to evaluate polymerization efficiency. To characterize the network structure, the swelling ratio values were converted to the average molecular weight between crosslinks ( ) and mesh sizes (ξ) using Flory-Rehner theory. Current study suggested hydrophobic modification is desired to achieve high polymerization efficiency. Electrospinning is a developing technique to produce ultra fine fibrous structures from polymer solutions. Current research efforts have focused on understanding the effects of principal parameters such as molecular weight distribution (MWD) and polymer surfactant interactions on the morphology of the electrospun patterns. Fundamental understanding of the dilute solution rheology of the polydisperse polymer/solvent and polymer/solvent/surfactant systems was first established. Using viscometry, the on-set of entanglement concentrations could be obtained for various systems. Electrospinning was then carried out to evaluate the effects of polymer molecular weight, molecular weight distribution (MWD) and the polymer-surfactant interaction on the fiber formation and morphological features. The importance of increased chain entanglements due to high molecular weight component within the polydisperse system and the expansion of the coil dimension by binding the surfactant micelles have been recognized. The critical concentrations for incipient as well as stable fiber formation were determined. "
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The role of glutaredoxin-1 on B16F0 melanoma growth and angiogenesis in diet-induced diabetic miceChong, Brian Sung Ho 11 July 2018 (has links)
OBJECTIVES: Recent studies have elucidated that diabetes mellitus (DM) patients exhibit an accelerated tumor progression, but the mechanism of its regulation is not yet fully understood. The following study seeks to examine the role of angiogenic factors in the growth of subcutaneously injected melanoma cancer using a diet-induced type II diabetic mouse model.
METHODS: C57BL/6 mice were fed either a regular or high-fat, high-sucrose (HFHS) diet for 2 months (T2DM model; confirmed through a GTT) and subcutaneously injected with B16F0 melanoma cells. After a 1-week or 2-week incubation period, the tumor was extracted to examine its size, weight, vascularity, and gene/protein expression. In vitro studies were performed using endothelial cells to assess the effects of high-glucose on endothelial cell proliferation, migration, and tube formation. GLRX expression was examined in both tumor samples and endothelial cells.
RESULTS: The results of the study showed that T2DM induced by a HFHS diet is able to promote tumor growth in both weight (2-week, p = 0.0070) and volume (1-week, p = 0.0351; 2-week, p = 0.0002). Tumors extracted from the HFHS diet group showed reduced expressions of angiogenic markers (ACTA2 (1-week, p = 0.0239; 2-week, p = 0.0123), KDR (1-week, p = 0.0091)) by western blot and a slightly reduced trend of angiogenesis (PECAM1) in histological analyses. GLRX expression was reduced in HFHS tumor samples (1-week, p = 0.0090) and, interestingly, lower amounts of GSH adducts (2-week, p = 0.0317) could be seen in 2-week tumors as well. In vitro studies of endothelial cells showed reduced trends of endothelial cell function (proliferation, migration, and tube formation) in high glucose medium. Also, it has been observed that high glucose may be able to stimulate GLRX expression in endothelial cells.
CONCLUSION: The results of the following study have confirmed that B16F0 melanoma growth is, in fact, augmented in diet-induced diabetic mice; however, the vascularity and levels of angiogenic markers from the tumor tissues did not parallel the growth in its size. In vitro studies suggested that high glucose can impair EC function (i.e. proliferation, migration, and tube formation capabilities) as well as promote GLRX expression, which may be related to this discrepancy. Glutaredoxin-1 (GLRX), an enzyme which controls redox signaling, is upregulated in DM. Endothelial cell-specific GLRX overexpression in transgenic mice was found to stimulate subcutaneously injected melanoma (B16F0) growth, despite hindering limb revascularization after hind limb ischemia. The augmented tumor progression in DM may be associated with GLRX upregulation, alongside impaired ischemic limb revascularization and tumor angiogenesis; however, the mechanism of tumor growth in diabetes still lies inconclusive and further studies need to be examined to elucidate this phenomenon.
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Contrôle microstructural des réactions rédox à l'interface solide/solution lors de la dissolution d'oxydes mixtes à base d'uranium (IV) / Microstructural control of redox reactions at the solid/solution interface during the dissolution of uranium (IV) - based mixed oxidesTocino, Florent 14 December 2015 (has links)
Dans le cadre de l’utilisation potentielle d’oxydes mixtes d’actinides au sein des réacteurs nucléaires de 3ème et 4ème générations, des solutions solides de formules générales U1-xThxO2, U1-xCexO2-y, U0,75Nd0,25O1,875, U0,75Gd0,25O1,875 et Th0,75Nd0,25O1,875 ont été préparées par conversion thermique de précurseurs oxalate. Préalablement à l’évaluation de la durabilité chimique des matériaux, une étape de frittage a été entreprise afin d’obtenir des pastilles denses présentant diverses propriétés physico-chimiques et microstructurales d’intérêt (composition, homogénéité, taux de densification, …) L’étude multiparamétrique de la dissolution, conduite en milieux nitrique, sulfurique et chlorhydrique a souligné l’impact important de la composition chimique au sein du matériau sur la durabilité chimique des échantillons. En effet, plusieurs paramètres (ordres partiels par rapport à l’activité en protons, énergie d’activation apparente, …) ont confirmé une modification significative du mécanisme de dissolution prépondérant pour les échantillons enrichis en uranium. Par ailleurs, le rôle important joué par certaines espèces azotées à l’interface solide/solution a également été démontré. L’évolution de l’interface solide/solution (surface réactive, composition) en cours de dissolution a également été suivie à travers une étude operando par Microscopie Electronique à Balayage en mode Environnemental. Cette étude a souligné l’existence de zones préférentielles de dissolution (jonctions triples, joints de grains, porosités inter- et intragranulaires) pour les échantillons les moins riches en uranium ; laquelle s’accompagne d’une forte augmentation de la surface réactive. En raison d’un phénomène prépondérant d’oxydation de l’uranium(IV) à l’interface, la dissolution des échantillons enrichis en uranium apparaît nettement plus homogène. / In the field of the use of actinides mixed oxides as potential fuels for the Gen(III) and Gen(IV) nuclear reactors, solid solutions with general formula U1-xThxO2, U1-xCexO2-y, U0.75Nd0.25O1.875, U0.75Gd0.25O1.875 and Th0.75Nd0.25O1.875 were prepared by thermal conversion of oxalate precursors. Dense pellets exhibiting various physico-chemical and microstructural properties (in terms of composition, homogeneity, densification rate, …) were prepared through sintering then submitted to dissolution tests.The multiparametric study of the dissolution, performed in nitric, sulfuric and hydrochloric media clearly underlined the important effect of the chemical composition on the chemical durability of the samples. Indeed, several parameters (including partial order related to proton activity, apparent activation energy) confirmed the significant modification of the preponderant dissolution mechanism for uranium-enriched samples. Moreover, the role of various nitrogen-based species was evidenced at the solid/solution interface.The evolving of solid/solution interfaces (reactive surface area, composition) during dissolution was monitored by the means of operando ESEM experiments. Preferential dissolution zones (triple junctions, grain boundaries, inter- and intra-granular porosities) were clearly observed for uranium-depleted samples. They induce a significant increase of the reactive surface area even for short progress of the reaction. On the contrary, the dissolution appeared more homogenous for uranium-enriched samples due to the existence of a preponderant mechanism associated to the oxidation of the uranium(IV) at the interface.
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Peroxiredoxins : yeast redox switches that regulate multiple cellular pathwaysKritsiligkou, Paraskevi January 2016 (has links)
Peroxiredoxins are small ubiquitous cysteine-containing proteins that exhibit high reactivity to hydrogen peroxide. Apart from their role as antioxidants, detoxifying hydrogen peroxide to water, peroxiredoxins have been implicated in other cellular processes, such as protein folding and signalling. Using S. cerevisiae as a model organism, we utilised a variety of techniques to examine previously unexplored links between peroxiredoxins and mitochondrial function. Firstly, we characterised the role of Gpx3 in yeast mitochondria. Proteomic work revealed the presence of Gpx3 in the mitochondrial intermembrane space (IMS) and we characterised when, how and why Gpx3 can be found within the mitochondria. We showed that cells lacking Gpx3 have aberrant mitochondrial morphology and defective protein import capacity and inner membrane potential upon H2O2 stress. Gpx3 translocates to the IMS via a targeting sequence encoded from a non-AUG codon. This provides a novel and unique molecular mechanism that protects mitochondria from the exceptional oxidative stress which their activity imposes. Secondly, we focused on the role of Tsa1 upon protein aggregation-induced stress. Previous studies using the proline analogue AZC to cause protein misfolding revealed that protein aggregates are localised adjacent to mitochondria and mitochondrial ROS are generated in response. We questioned what effect this might have on mitochondrial function and we showed that upon AZC treatment there is a drop in respiratory rate, dependent on Tsa1. We questioned whether Tsa1, like other peroxiredoxins, is involved in regulating signalling cascades and we showed that cells that are lacking Tsa1 have alterations in the activity of the cAMP/PKA pathway. In parallel, we looked for differences both in the proteome and the transcriptome to understand what is the cause of the lethality of a tsa1 strain upon protein aggregation stress. We propose a mechanism where Tsa1 mediates a transcriptional response to protein misfolding stress via the activity of the heat shock transcription factor, Hsf1. Finally, we focused on the role of the mitochondrial peroxiredoxin Prx1. Under conditions where the mitochondrial matrix is oxidised, either genetically or by chemical addition, we showed than an apoptotic pathway is activated, dependent on the redox state of thioredoxin, Trx3. We showed that Trx3 can interact with Prx1 and loss of Prx1 also stops the induction of cell death. Analysis of the interactome of Trx3 unraveled the involvement of Bxl1/Ybh3, the yeast BH3 domain-containing protein and Aim9, a previously uncharacterised protein with kinase-like motifs, in the progression of cell death. The data presented in this thesis widens our understanding of the function of peroxiredoxins and their involvement in the regulation of cellular cascades that ensure correct mitochondrial function and responses to stress.
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Molecular mechanisms of redoxin-mediated signalling in plant immunityKneeshaw, Sophie January 2016 (has links)
Posttranslational modification (PTM) of proteins is essential to creating a diverse proteome with the complex functions necessary to regulate key cellular processes. Redox-based PTMs exhibit many desirable characteristics to finely modulate transcriptional regulators; they occur rapidly and can alter protein conformation, localisation and activity. The plant immune system offers an excellent model in which to study redox-based modifications due to the rapid accumulation of oxidising agents that occurs during immune invasion. This so-called “oxidative burst” causes spontaneous oxidation of cysteine residues that are present in many regulatory proteins. These modifications fine-tune the activities of proteins that harbour them, enabling them to act in a concerted effort to reprogram the transcriptome, prioritising the expression of immune-related genes over housekeeping genes. Disulphide bonds (S-S) and S-nitrosothiols (SNO, i.e. the addition of an NO group to a cysteine moiety) have been shown to play particularly important roles in plant immunity. However, what still remains unclear is how these redox-based PTMs are rendered reversible, enabling them to act as molecular signalling switches. The work presented in this thesis explores a class of enzymes that are responsible for controlling the cellular levels of protein oxidation: the Thioredoxins. In addition to their well-established role in reducing disulphide bonds, I demonstrate in Chapter 3 that Thioredoxins are able to reverse protein S-nitrosylation during plant immune signalling. Immune-inducible Thioredoxin-h5 (TRXh5) was shown to be unable to restore immunity in gsnor1 mutants that display excessive accumulation of the NO donor S-nitrosoglutathione, but rescued impaired immunity and defence gene expression in nox1-mutants that exhibit elevated levels of free NO. This data indicates that TRXh5 discriminates between protein-SNO substrates to provide previously unrecognized specificity and reversibility to protein-SNO signalling in plant immunity. Furthermore, data is presented to show that TRXh5 reversed the effects of S.nitrosylation on many immune-related transcriptional regulators in vitro, forming the initial stages of an investigation into which proteins and pathways might be controlled by reversible S-nitrosylation in plant immunity (Chapters 3 & 4). Although the majority of transcriptional regulators are likely modified at their site of action, the nucleus, very little is currently known about nuclear redox signalling in plants. Therefore, in Chapter 5 a subclass of theThioredoxin superfamily was studied, the Nucleoredoxins, which have previously been shown to display disulphide reduction activity and localise in part to the nucleus. Here it is revealed that the activity and nuclear accumulation of Nucleoredoxin 1 (NRX1) is induced by the plant leaf pathogen Pseudomonas syringae, suggesting a key role for this protein in immune signalling. Target-capture experiments and subsequent mass spectrometry analysis identified the first in vitro targets of NRX1 and revealed many proteins with roles in oxidative stress, including the hydrogen peroxide scavenger Catalase 2 (CAT2). Moreover, overexpression of NRX1 was shown to be able to rescue the enhanced cell death phenotype of cat2 knockout mutants in response to the oxidative stressor, methyl viologen. Accordingly, nrx1 knockout mutants also exhibited an enhanced cell death phenotype in response to methyl viologen treatment. Together, these data indicate that NRX1 plays a key role in the control of oxidative stress-mediated cell death, potentially through direct regulation of Catalase proteins. Taken together, the work in this thesis implicates members of the Thioredoxin family as key regulators of transcriptional reprogramming during plant immunity and uncovers a novel role for Thioredoxin superfamily member, NRX1, in the control of oxidative stress.
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Funktionale Analyse des CC-Typ Glutaredoxin ROXY19 in Arabidopsis thaliana / Functional Analysis of CC-type glutaredoxin ROXY19 in Arabidopsis thalianaOberdiek, Jan 31 May 2018 (has links)
No description available.
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Avaliação da interferência de diferentes doadores de elétronse Mediadores Redox sobre a remoção anaeróbia de cor em efluentes têxteisMeirelles de Amorim, Sandra 31 January 2010 (has links)
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Previous issue date: 2010 / Faculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco / A adição de diferentes doadores de elétrons (sacarose e etanol) e mediadores redox (riboflavina e lawsone) foi realizada em efluente têxtil real de uma lavanderia da cidade de Caruaru PE e em efluente têxtil sintético, com o intuito de avaliar a interferência sobre a remoção anaeróbia de cor. Foram realizados 14 ensaios com ausência e presença de doadores de elétrons e mediadores redox em combinações variadas. Os mediadores redox, quando adicionados, possuíam uma concentração de 0,012 mM, e o corante (Direct Black 22), usado no efluente sintético, foi adicionado em concentração de 0,06 mM. Para o efluente têxtil real, as eficiências de remoção de cor variaram de 23 a 38%, sendo o maior valor obtido com a adição apenas sacarose; as velocidades de remoção se mostraram melhores em ausência de ambos os mediadores redox; a remoção de DQO variou de 26 a 65%, sendo o maior valor observado em presença de etanol com riboflavina. Considerando eficiências de remoção de cor e DQO, os ensaios em presença apenas de etanol, demonstraram melhor desempenho com eficiência de 31% e 57% para cor e DQO, respectivamente. Para o efluente sintético, as eficiências de remoção de cor variaram de 83 a 93% sendo o maior valor observado em presença de sacarose; para a remoção de DQO, verificaram-se eficiências variando de 24 a 69%, sendo considerada mais eficiente a remoção no ensaio em presença apenas de etanol. A velocidade de remoção foi 2,8 vezes menor com a adição do mediador redox riboflavina para a sacarose e 1,3 vezes maior quando adicionado lawsone a sacarose, em relação ao ensaio apenas com sacarose. Para os ensaios em presença de etanol, houve um aumento na velocidade de remoção de cor de 1,7 vezes em presença de lawsone e 2,5 vezes em presença de riboflavina, quando em relação ao ensaio apenas com etanol. Considerando remoção de cor e DQO os melhores resultados foram obtidos em presença de etanol, com eficiências iguais a 83% e 69%, respectivamente. No entanto, neste caso, a velocidade de remoção de cor foi inferior aos demais ensaios. Para o experimento em questão a adição de mediadores redox não interferiu positivamente, tendo o acréscimo apenas de doadores de elétrons fornecido boas eficiências
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Measuring redox potential in 3D breast cancer tumour models using SERS nanosensorsJamieson, Lauren Elizabeth January 2016 (has links)
Cellular redox potential is incredibly important for the control and regulation of a vast number of processes occurring in cells. Disruption of the fine redox balance within cells is has been associated with disease. Of particular interest to my research is the redox gradient that develops in cancer tumours, in which the internal regions are further from vascular blood supply and therefore become starved of oxygen and hypoxic. This makes treatment of these areas a lot more challenging, as radiotherapy approaches rely on the presence of oxygen and, with a poor vascular blood supply, drugs delivered through the blood stream will have poor access to these regions. Currently, there is limited knowledge regarding the quantitative nature of this redox gradient in cancerous tumours. To aid the development of drugs and therapies to overcome this problem, a system that enables quantitative mapping of redox potential through a tumour would be a vital tool. In this work redox sensitive molecules attached to gold nanoparticles (NPs) are delivered to cells and give signals using surface enhanced Raman scattering (SERS). Redox potential changes are monitored quantitatively by ratiometric changes in signal intensity of selected signals in the SER spectra acquired. Multicellular tumour spheroids (MTS) are used as a three dimensional (3D) in vitro tumour model, in which the 3D architecture and gradients observed in tumours in vivo develop. As redox potential is pH dependent and pH is another important physiological characteristic in its own right, a SERS pH sensor was developed and ultimately a system that multiplexes intracellular pH and redox measurement by SERS. Initially, simultaneous redox potential and pH measurements were performed in monolayer culture before extending this to MTS. Photothermal optical coherence tomography (OCT) was used to investigate overall 3D NP distribution in the MTS models. It was possible to control NP delivery to MTS to localise NPs to various regions. Redox potential and pH could then be measured using a fibre optic Raman probe, and spatial response to drug treatment monitored. Intracellular NP localisation was investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), helium ion microscopy (HIM) and confocal fluorescence microscopy (CFM) and attempts were made to control NP delivery to particular intracellular compartments.
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Biology of redox active endosomal signaling in response to Il-1-BetaOakley, Fredrick Daniel 01 May 2011 (has links)
Interleukin-1-beta (IL-1β) is a potent proinflammatory cytokine. A primary outcome of IL-1β signaling is the activation of NFκB, a transcription factor that induces a large number of immune molecules, apoptotic factors, anti-apoptotic factors, and other transcription factors. Recent work has demonstrated that the activation of NFκB involves a multistep redox-signaling cascade that requires endocytosis of the interleukin receptor (IL-1R1)/ligand pair and superoxide production by NADPH oxidase 2 (Nox2) within the resulting newly formed early endosome. Hydrogen peroxide produced by the rapid dismutation of superoxide is necessary for the subsequent downstream recruitment of IL-1R1 effectors (TRAF6, IKK kinases) and ultimately the activation of NFκB. In this thesis, I have further dissected the spatial and temporal events that coordinate signaling processes of the IL-1β pathway. Using a combination of biophotonic imaging, immunofluorescence imaging, and lipid raft density gradient isolation, I demonstrate that both Nox2 and IL-1R1 are constitutively present in lipid raft microdomains on the plasma membrane. Stimulation by IL-1β induces endocytosis of Nox2 and IL-1R1 from the plasma membrane into caveolin-1, lipid raft positive early endosomes. Further, inhibition of lipid raft mediated endocytosis or deletion of caveolin-1 inhibits activation of NFκB, by IL-1β. We have also identified Vav1 as the Rac1 guanine exchange factor that is recruited to caveolin-1 positive lipid rafts following IL-1β stimulation, and demonstrated that dominant negative Vav1 inhibits NFκB activation by IL-1β. Following this work, I utilized assays for redox sensitivity and mass spectrometry to demonstrate that C70, C73, and C105 are hydrogen peroxide sensitive cysteines within the RING domain of TRAF6. I further demonstrate that hydrogen peroxide does not alter the E3 ubiquitin ligase activity associated with the TRAF6 RING domain. My findings suggest that the redox sensitivity of the RING domain mediates TRAF6 recruitment to the receptor complex. This is supported by the observation that hydrogen peroxide treatment of TRAF6, but not early signaling effectors (IL-1R1, IRAK1, IRAK4, MyD88) mediates TRAF6 recruitment to the IL-1 receptor complex. Further, mutation of the identified redox sensitive cysteines inhibits IL-1β signaling and NFκB activation. This research has helped to refine the understanding of the IL-1β signaling pathway, and may ultimately lead to new therapeutic targets for controlling inflammation.
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GEOCHEMISTRY AND ORGANIC PETROGRAPHY OF THE ANNA SHALE (PENNSYLVANIAN) AND THE OCCURENCE OF PYRITE “SUNS” IN SOUTHWESTERN ILLINOISDyson, Jacob 01 August 2019 (has links)
The Anna Shale (Pennsylvanian) is an organic-rich, marine black shale that commonly overlies the Herrin (No. 6) Coal of the Carbondale Formation, Illinois Basin. Disk-shaped iron sulfide concretions, called pyrite suns, which are commonly up to 10 cm or more across are found in the lowest few centimeters of the Anna Shale in coal mines near Sparta in southwestern Illinois. This area is the only known location where pyrite suns of this size have been found, suggesting that unusual geochemical and/or depositional conditions led to their formation. The primary objective of this study was to evaluate the geochemical conditions at the time of Anna Shale deposition in the area where the pyrite suns formed.
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