No description available.

The present study is targeted on the optimization of the flotation conditions for the improvement of the industrial flotation practice. Part I is focused on the improvement of the flotation of Mountain Pass mine ore for the beneficiation of rare earth elements. The objective is to improve the rare earth recovery of Mountain Pass ore by developing a novel flotation reagents' scheme, meanwhile reducing the flotation temperature to a cost-efficient level and simplifying the flowsheet. Surface chemistry study by contact angle, zeta potential and microflotation tests indicate that a mixed collector consisting of oleic acid (OA) and sodium octanohydroxamate hydrate (OHA) is beneficial for rare earth flotation. More importantly, salicylhydroxamic acid (SHA) is also a promising collector due to the high selectivity. Lab-scale flotation tests using SHA as collector show that 80-90% REE recovery and <20% gangue recovery are achieved at 40°C~60°C, which yield a rougher concentrate of 30%~40% REO. A novel flotation scheme has been developed towards Mountain Pass rare earth mine. The new scheme is of both high selectivity and high recovery, meanwhile the dosage of reagent required is much less, and the flotation temperature is also significantly reduced. Interactive adsorption models are built up through FT-IR and AFM study. The interaction of collector with bastnaesite surface is illustrated. Hydroxamic acid collectors (OHA and SHA) adsorb on bastnaesite surface by forming stable chelating complex. The selectivity of collectors towards bastnaesite flotation is summarized as SHA>OHA>OA. Part II is focused on the improvement of the flotation of Resolution Copper's Superior mine ore at an elevated temperature for the beneficiation of chalcopyrite. Because the Resolution Copper ore is mined from a deep, hot, underground mine, the temperature of ROM (run of mine ore) is much higher than that of the ore usually processed in a typical open-pit copper mine. The ore temperature will still be high during flotation. It is therefore critical to carry out a systemic study on the flotation of Resolution Copper ore at elevated temperatures and clarify the impact on flotation. An overall beneficial effect is observed in high temperature flotation through a lab-scale flotation study. Further action of temperature control is not necessary. The contact angle results indicate that surface hydrophobicity is enhanced at elevated temperature, of which the surface morphology change (shown by AFM images) of xanthate adsorption species (dixanthogen) is the key factor.

No description available.

The iron chelating molecule, ethylenediaminetetraacetic acid (EDTA) is used in food applications for the preservation of oxidation prone ingredients. Research has suggested that EDTA is also capable of enhancing the antimicrobial effectiveness of various compounds including naturally-derived antimicrobials. With consumer demand for cleaner food labels, there remains an opportunity to introduce new chelating technology to replace synthetically-derived EDTA. Through photographting and chemical conversion, hydroxamic acid ligands were covalently bound to polypropylene films resulting in polypropylene-graft-poly(hydroxamic acid) (PP-g-PHA). The resulting films demonstrated an ability to chelate 64 nmol/cm2 from an iron saturated environment or 163 nmol/cm2 of magnesium and 139 nmol/cm2 of calcium from bacterial growth media. A surface pKa of 8.97 suggested that film ligands should remain protonated under acidic and neutral pH conditions. When combined with lysozyme, PP-g-PHA films were able to reduce inhibitory concentration of lysozyme for Listeria monocytogenes by half. When tested against Bacillus cereus, Pseudomonas fluorescens, and E. coli O157:H7; PP-g-PHA films were unable to inhibit growth and showed little enhancement of lysozyme. EDTA controls revealed that similar levels of soluble chelator were more effective than immobilized chelators. EDTA results also suggested that a chelating film with a higher affinity for iron (through coordination or ligand stability) may be able to control B. cereus growth. Both EDTA and PP-g-PHA caused P. fluorescens to produce siderophores (pyoerdines), suggesting that each treatment resulted in a low-iron growth environment. These findings suggest that surface bound chelating technology can affect the growth of L. monocytogenes and enhance the effectiveness of lysozyme. With improved surface chemistry (a higher binding constant with iron), this technology has the potential to influence the growth of other pathogens and spoilage microorganisms.

Cardiovascular diseases (CVD) have been the leading cause of death worldwide for many years, making it a devasting and increasing concern across the globe. The risk factors of CVD include postnatal factors and prenatal factors. For the prenatal CVD risk factors study, we focused on maternal hypothyroidism (MH), which is a common clinical condition. Studies have shown MH progeny have increased susceptibility to both acquired cardiovascular disease in adulthood and congenital heart disease, but the underlying mechanisms are not well understood. The goal of the present experiments was to test the hypothesis that MH reduces early postnatal cardiac myocyte proliferation in the progeny so that their adult hearts have a smaller complement of cardiac myocytes, which leads to adverse cardiac disease responses. MH model was induced by thyroidectomy (TX) with total thyroxine (TT4) under 1ng/dl after surgery. The progeny from mice that underwent Sham or TX surgery was termed WT (wild type) or MH (maternal hypothyroidism) progeny, respectively. Hearts were collected from WT and MH progeny to determine heart weight (HW), CM size, CM proliferation, and cell culture. RNA-seq was performed on heart tissue at postnatal day 5 (P5) and P60. Transverse Aortic Constriction (TAC) was performed to cause pressure overload-induced cardiac hypertrophy and/or heart failure (HF) in adult WT and MH progeny. ECHO (in-vivo) and histological (ex-vivo) studies were performed at specific times after TAC. Thyroid hormone treatment (levothyroxine, T4) for MH mother was administered. The results showed that the Heart weight (HW) to body weight (BW) ratio at P60 was no difference between groups, but the MH progeny had a larger CM size, consistent with fewer CM numbers. MH progeny had lower EdU+, Ki67+, and PH3+ CMs, and fewer mononucleated CMs, which shows they had a decreased CM proliferation capacity. RNA-seq data showed that genes related to DNA replication were downregulated in P5 MH progeny, including Bmp10. Both in vivo and in vitro studies showed Bmp10 treatment increased CM proliferation in the presence of thyroid hormone. In adult progeny, RNA-seq data showed that MH mice had genes upregulated in the inflammatory response before TAC surgery. Six weeks after TAC, the MH progeny had a greater HW/BW ratio, larger CM size, and more severe LV fibrosis consistent with more severe cardiac pathological remodeling compared with WT progeny. T4 supplemented treatment for MH mothers preserved progeny’s early postnatal CM proliferation capacity and the excessive pathological remodeling after TAC. Concluding, CM proliferation during the early postnatal development stage was significantly attenuated in MH progeny, which results in fewer CMs and CM hypertrophy in adult MH progeny. These changes are associated with worse cardiac disease responses under pressure overload in adult MH progeny. For the postnatal CVD risk factors study, we focused on calcium overload and metabolic disorder, which play a critical role in heart failure with preserved ejection fraction (HFpEF). HFpEF is defined as HF with an EF ≥50% and elevated cardiac diastolic filling pressures. The underlying causes of HFpEF are multifactorial and not well-defined. A transgenic mouse with low levels of cardiomyocyte (CM)-specific inducible Cavβ2a expression (β2a-Tg mice) showed increased cytosolic CM Ca2+, and modest levels of CM hypertrophy and fibrosis. This study aimed to determine if β2a-Tg mice develop an HFpEF phenotype when challenged with two additional stressors, a high-fat diet (HFD) and L-NAME (LN). Four-month-old wild-type (WT) and β2a-Tg mice were given either normal chow (WT-N, β2a-N) or HFD and/or L-NAME (WT-HFD, WT-LN, WT-HFD-LN, β2a-HFD, β2a-LN, and β2a-HFD-LN). Some animals were treated with the HDAC (hypertrophy regulators) inhibitor suberoylanilide hydroxamic acid (SAHA) (β2a-HFD-LN-SAHA). Echocardiography was performed monthly. After four months of treatment, terminal studies were performed, including invasive hemodynamics and organ weight measurements. Cardiac tissue was collected. Our results showed that four months of HFD plus L-NAME treatment did not induce a profound HFpEF phenotype in FVB WT mice. β2a-HFD-LN (3-Hit) mice developed features of HFpEF, including increased natriuretic peptide (ANP) levels, preserved EF, diastolic dysfunction, robust CM hypertrophy, increased M2 macrophage population, and myocardial fibrosis. SAHA reduced the HFpEF phenotype in the 3-Hit mouse model by attenuating these effects. Concluding, the 3-Hit mouse model induced a reliable HFpEF phenotype with CM hypertrophy, cardiac fibrosis, and an increased M2 macrophage population. This model could be used for identifying and preclinical testing of novel therapeutic strategies. / Biomedical Sciences

Micro and nanofabrication technologies have been used extensively in many biomedical and biological applications. Integration of MEMS technology and biology (BioMEMS) enables precise control of the cellular microenvironments and offers high throughput systems. The focus of this research was to develop three dimensional (3-D) isotropic microstructures for comprehensive analysis on cell-substrate interactions. The aim was to investigate whether the normal and cancerous cells differentially respond to their underlying substrate and whether the differential response of the cells leads to a novel label-free technique to distinguish between normal and cancerous cells. Three different generations of 3-D isotropic microstructures comprised of curved surfaces were developed using a single-mask, single-etch step process. Our experimental model included HS68 normal human fibroblasts, MCF10A normal human breast epithelial cells and MDA-MB-231 metastatic human breast cancer cells. Primary findings on the first generation of silicon substrates demonstrated a distinct adhesion and growth behavior in HS68 and MDA-MB-231 cells. MDA-MB-231 cells deformed while the fibroblasts stretched and elongated their cytoskeleton on the curved surfaces. Unlike fibroblasts, MDA-MB-231 cells mainly trapped and localized inside the deep microchambers. Detailed investigations on cytoskeletal organization, adhesion pattern and morphology of the cells on the second generation of the silicon substrates demonstrated that cytoskeletal prestress and microtubules organization in HS68 cells, cell-cell junction and cell-substrate adhesion strength in MCF10A cells, and deformability of MDA-MB-231 cells (obtained by using AFM technique) affect their behavior inside the etched cavities. Treatment of MDA-MB-231 cells with experimental breast cancer drug, SAHA, on the second generation of substrates, significantly altered the cells morphology, cytoarchitecture and adhesion pattern inside the 3-D microstructures. Third generation of silicon substrates was developed for comprehensive analysis on behavior of MDA-MB-231 and MCF10A cells in a co-culture system in response to SAHA drug. Formation of colonies of both cell types was evident inside the cavities within a few hours after seeding the cells on the chips. SAHA selectively altered the morphology and cytoarchitecture in MDA-MB-231 cells. Most importantly, the majority of MDA-MB-231 cells stretched inside the etched cavities, while the adhesion pattern of MCF10A cells remained unaltered. In the last part of this dissertation, using AFM analysis, we showed that the growth medium composition has a pronounced effect on cell elasticity. Our findings demonstrated that the proposed isotropic silicon microstructures have potential applications in development of biosensor platforms for cell segregation as well as conducting fundamental biological studies. / Ph. D.

L'épilepsie du lobe temporal (ELT) est la forme la plus fréquente de l'épilepsie chez l'adulte. Elle se traduit par des crises spontanées et récurrentes, qui sont résistantes à tout traitement dans 90% des cas. Une agression initiale du cerveau (traumatisme crânien, méningite, convulsions fébriles etc.), est souvent à l'origine de la transformation d'un cerveau « sain » en cerveau épileptique. L'ensemble des processus responsables de cette transition s'appelle l'épileptogenèse. Pouvoir bloquer et/ou retarder l'épileptogenèse chez les patients à risque est une question de santé majeure. En plus des crises, l'ELT soulève d'autres questions. Elle est souvent associée à des déficits cognitifs, qui sont la conséquence de la réorganisation des circuits neuronaux. Ces déficits pourraient être traités de façon indépendante de l'épilepsie elle-même. Le projet de recherche de cette thèse s'inscrit dans ce cadre général. / Temporal Lobe Epilepsy (TLE) is the most common form of epilepsy in adults. It translates into spontaneous and recurrent seizures, which are resistant to any treatment in 90% of cases. An initial brain insult (head injury, meningitis, febrile seizures etc.), is often the cause of the transformation of a "healthy" brain into an epileptic one. The process responsible for this transition is called epileptogenesis. Blocking and/or delaying epileptogenesis in at-risk patients is a key issue for public health. In addition to the seizures, TLE raises other problems. It is often associated with cognitive deficits, which are the result of the reorganization of neuronal circuits. These deficits may be treated independently of epilepsy itself. The work presented here fits into this general framework.

Pubertal timing displays wide, normally distributed variation in a healthy population of sexually maturing adolescents. However, like many complex traits, factors contributing to the variation are not well understood. Epigenetic regulation may contribute to some of the population variation. The role that epigenetics, specifically DNA methylation and histone acetylation, may play in regulating pubertal timing was investigated in C57BL/6 female mice: investigating whether population variation in pubertal timing among inbred mice could be explained by environmental factors; whether perturbing the epigenome using a histone deacetylase inhibitor or methyl-donor would alter pubertal timing; and examining genome-wide methylation patterns in hypothalami of early versus late maturing mice. Results demonstrate that measurable micro-environmental factors have only negligible effects on pubertal timing; pubertal timing was significantly altered by administration of epigenetic modifying agents; differences in methylation patterns are subtle. This initial evidence supports the involvement of epigenetic mechanisms in regulating pubertal timing.

Pubertal timing displays wide, normally distributed variation in a healthy population of sexually maturing adolescents. However, like many complex traits, factors contributing to the variation are not well understood. Epigenetic regulation may contribute to some of the population variation. The role that epigenetics, specifically DNA methylation and histone acetylation, may play in regulating pubertal timing was investigated in C57BL/6 female mice: investigating whether population variation in pubertal timing among inbred mice could be explained by environmental factors; whether perturbing the epigenome using a histone deacetylase inhibitor or methyl-donor would alter pubertal timing; and examining genome-wide methylation patterns in hypothalami of early versus late maturing mice. Results demonstrate that measurable micro-environmental factors have only negligible effects on pubertal timing; pubertal timing was significantly altered by administration of epigenetic modifying agents; differences in methylation patterns are subtle. This initial evidence supports the involvement of epigenetic mechanisms in regulating pubertal timing.

L'enveloppe cellulaire des bactéries à Gram négatif constitue la première ligne de défense contre les antibiotiques. Sous l’effet, d’une part, de la faible perméabilité de la membrane externe qui s'oppose à la pénétration des agents antibactériens, d’autre part des pompes d'efflux qui favorisent leur expulsion, elle empêche nombre de composés potentiellement actifs in vitro d'atteindre leur cible, limitant l’effet antibactérien. Un enjeu important pour restaurer l’activité de ces molécules est de trouver une stratégie pour en augmenter la concentration intracellulaire. L'objectif de cette thèse est de développer des métallodrogues comme nouvelle stratégie de vectorisation de drogues dans les cellules. Cette stratégie repose sur l’association d'une drogue active in vitro, et d’un ligand auxiliaire ayant des propriétés perméabilisantes ou inhibitrices de pompe d’efflux, dans un complexe qui jouera le rôle de chaperone. Les agents antibactériens utilisés sont des inhibiteurs (dérivés d’acides hydroxamiques) de peptide déformylase (PDF) et de méthionine aminopeptidase (MetAP) développés au laboratoire. Tout d’abord, une étude globale de la stratégie de vectorisation a été réalisée (i) étude de stabilité de métallodrogues modèles : en utilisant un acide hydroxamique fluorescent, nous avons montré que, seules, des métallodrogues à Co(III), à la différence de celles à Cu(II) et Fe(III), satisfaisaient aux conditions de stabilité compatibles avec les conditions de tests biologiques. (ii) Etude de la libération de la drogue : nous avons établi par une étude RMN 1H et UV-vis qu’en milieu tampon pH = 7,4, la libération de la drogue se faisait par échange de ligand avec un thiol exogène. Récemment, une nouvelle série d’inhibiteurs de PDF a été synthétisée au laboratoire. Elle est basée sur un squelette hétérocyclique à 5 chaînons fonctionnalisé par une chaîne en C4, puis via un espaceur monocarboné, à un acide hydroxamique. Les meilleurs résultats ont été obtenus avec un oxadiazole (AT002 16 µg/ml sur E. coli en présence de perméabilisant PMBN). Au cours de cette thèse, pour améliorer la lipophilie, des groupements aromatiques ont été fixés sur cet hétérocycle. Les MICs sur la souche d’E. coli sauvage n’ont pas été améliorées mais en présence de PMBN, le dérivé présentant la meilleure activité est le composé AT015 (2 µg/ml sur E. coli en présence de PMBN) qui a donc été choisi pour concevoir des métallodrogues. La métallodrogue réunit autour d’un métal deux parties: (i) un ligand auxiliaire fonctionnalisé via un espaceur par un perméabilisant peptidique analogue de peptide antimicrobien ou par un modulateur de l’efflux (ii) un acide hydroxamique inhibiteur de PDF. Au cours de la SAR réalisée en faisant varier la drogue, le ligand auxiliaire et le métal, nous avons montré que les meilleures métallodrogues permettent d’améliorer l’activité de la drogue sur la souche d’E. coli sauvage d’un facteur 16. Un des ligands auxiliaires fonctionnalisé par un tétrapeptide présente, seul, une activité sur une souche d’E. aerogenes résistante aux fluoroquinolones. Sur ce cas, l’activité biologique a été reliée, par des expériences de mapping par fluorescence, à son accumulation intracellulaire, en utilisant un analogue fluorescent de ce composé. / The gram negative bacterias’ cell envelopes are the first line of defense against antibiotics. First thanks to the low permeability of the external membrane that prevents the penetration of the antibiotics, but also thanks to the efflux pumps that help expelling the antibiotics from the cell. These mechanisms prevent many compounds, potentially active in vitro, from reaching their targets, thus limiting the antimicrobial effect. To increase the molecules’ intracellular concentration is one of the means to restore their activity. This thesis’ objective is to develop metallodrugs as a new drug vectorization strategy in cells. We here associate an active drug in vitro and an auxiliary ligand with permeabilization or efflux pumps inhibition abilities in a complex playing the role of a chaperone. We used peptide deformylase (PDF) and methionine aminopeptidase (MetAP) inhibitors (derived from hydroxamic acids) developed at the laboratory as antimicrobial agents. I’ll begin with a global study of the vectorization strategy we’ve adopted (i) Stability study of the metallodrugs models: using a fluorescent hydroxamic acid, we showed that only Co(III) metallodrugs are in agreement with the stability conditions compatible with the biological tests, in opposition with the Cu(II) and Fe(III) ones. (ii) Drug release study: we showed in 1H NMR and UV-vis studies that in a buffer solution pH 7.4, a ligand exchange with an exogenous thiol is responsible for the drug release. Recently, a new series of PDF inhibitors was synthesized at the laboratory. It is composed of a 5 membered heterocyclic skeleton functionalized by a chain in C4 followed by an hydroxamic acid via a monocarbonated spacer. The best results were obtained with an oxadiazole (AT002 16 µg/ml with E. coli and PMBN as permeabilizing agent). During this thesis, to enhance lipophilicity, we attached aromatic groups on the heterocycle. CMIs on the E. coli strain have not been increased but the compounds displaying the best activity in presence of PMBN (AT015, 2 µg/ml with E. coli and PMBN) was chosen to conceive metallodrugs. The metallodrug is composed of a metal center and two other parts: (i) an auxiliary ligand functionalized via a spacer by a permeabilizing peptide, an antimicrobial peptide analogue, or by an efflux modulator. (ii) An hydroxamic acid PDF inhibitor. We showed that the best metallodrugs enhance the drug activity on the wild E.coli strain by a 16 factor, with the SAR we realized, changing the drug, the auxiliary ligand and the metal. One of the auxiliary ligands functionalized by a tetrapeptide show an activity on a fluoroquinolone-resistant E. aerogenes strain while alone. Utilizing a fluorescent analogous of this compound, we linked the biological activity to its intracellular accumulation with fluorescence mapping experiments.