Background and aims: Lung recruitment maneuvers (brief episodes of high airway pressure) are a modern treatment alternative to achieve open lung conditions under mechanical ventilation of patients with acute lung injury. It is well known that positive pressure ventilation with high airway pressures cause negative circulatory effects, and that the effects on regional vascular beds can be even more pronounced than the systemic effects. Hypoperfusion of the mesenteric vascular bed can lead to tissue ischemia and local inflammation. This intestinal inflammation has been associated with subsequent development of multiple organ dysfunction syndrome, a syndrome that still carries a high mortality and is a leading cause of death for intensive care patients. The aim of this thesis was therefore to investigate whether lung recruitment maneuvers would cause negative effects on mesenteric circulation, oxygenation or metabolism. Methods and results: In an initial study on ten patients with acute lung injury, we could demonstrate a trend towards a decreased gastric mucosal perfusion during three repeated lung recruitment maneuvers. To more closely examine this finding, we set up an oleic acid lung injury model in pigs, and in our second study we established that this model was devoid of inherent intestinal effects and was adequate for subsequent studies of intestinal effects of lung recrutiment maneuvers. In the acute lung injury model, we also tested the effect of an infusion of a vasodilating agent concurrent with the recruitment maneuvers, the hypothesis being that a vasodilating agent would prevent intestinal vasoconstriction and hypoperfusion. We could show that three repeated lung recruitment maneuvers induced short term negative effects on mesenteric oxygenation and metabolism, but that these findings were transient and short lasting. Further, the effects of prostacyclin were minor and opposing. These findings of relative little impact on the intestines of lung recruitment maneuvers, lead us to investigate the hypothesis that repeated recruitment maneuvers maybe could elicite a protective intestinal preconditioning response, a phenomenon previously described both in the rat and in the dog. However, in our fourth study, using both classical ischemic preconditioning with brief periods of intestinal ischemia or repeated lung recrutiment maneuvers, we could not demonstrate the phenomenon of intestinal preconditioning in the pig. Conclusions: We conclude, that from a mesenteric point of view, lung recruitment maneuvers are safe, and only induce transient and short lasting negative effects. We also conclude that the cause of the minor effects of lung recruitment maneuvers is not dependent on intestinal preconditioning.

Sunflower (Helianthus annuus L.) high oleic acid content lines differ from conventional sunflower by an increase in oleic acid (C18:1) content of more than 60%. The current sunflower cultivars under production in South Africa are standard sunflower with high levels of linoleic acid (C18:2). The aim of this study was to improve the quality of oil produced by local sunflower germplasm with respect to oleic acid through employing a marker-assisted breeding technique to facilitate and speed up the recovery of the high oleic acid allele into the background of the recurrent parent genome. Eleven sunflower breeding genotypes with high and low oleic acid traits were obtained from the Agricultural Research Council-Grain Crops Institute (ARC-GCI) in Potchefstroom. The breeding genotypes were phenotypically characterised based on their oleic and linoleic acid levels using gas chromatography. Results demonstrated that the average mean of oleic and linoleic acid contents in high oleic acid genotypes were 72% and 17% respectively, while the average mean of oleic acid and linoleic acid contents in wild type lines were 33.5 % and 54 % respectively. These results indicated a perfect negative correlation between the amount of oleic and linoleic acids possessed in high and low oleic acid genotypes (R2 = -99.16%). Sequence characterised amplified region (SCAR) markers were tested to ascertain if any of the ten available dominant FAD2-1 markers was segregating with the high oleic acid allele. Four dominant SCAR markers (FAD2-1F4/R1; FAD2-1F4/R2; FAD2-1F13/R1; FAD2-1F14/R2) were strongly associated with the high oleic acid trait (P< 0.001). With regard to the inheritance of the high oleic acid trait, 143 plants of the F2 segregating population derived from a cross between the high oleic acid parent (AP901-95-3-4-1) and low oleic acid parent (H55-9-2-1-1) were genotyped with the four SCAR markers to determine the genetic state concerning the high oleic acid gene (Ol). Results from a Chi square analysis of the observed frequencies of each dominant FAD2-1 marker locus in 143 F2 individuals indicated that the deviation from the expected ratio of 3:1 (high to low oleic acid) was not statistically significant (P< 0.95) from the observed segregation ratio. These results were consistent with the previous finding that an incomplete dominant gene governs sunflower high oleic acid. A multiplex assay of 78 Simple sequence repeat (SSR) markers was optimised and evaluated on 143 plants of the F2 population to determine suitable SSR markers that can be used in a marker-assisted background selection. Only 14 markers were suitable for marker-assisted background selection based on their high polymorphic information content, allele frequency and maximum allele numbers. In conclusion, this study demonstrated the potential of using SSR and SCAR marker systems as a breeding tool to characterise and speed up the selection process in marker-assisted backcross breeding. / Thesis (MSc (Botany))--North-West University, Potchefstroom Campus, 2013.

Sunflower (Helianthus annuus L.) high oleic acid content lines differ from conventional sunflower by an increase in oleic acid (C18:1) content of more than 60%. The current sunflower cultivars under production in South Africa are standard sunflower with high levels of linoleic acid (C18:2). The aim of this study was to improve the quality of oil produced by local sunflower germplasm with respect to oleic acid through employing a marker-assisted breeding technique to facilitate and speed up the recovery of the high oleic acid allele into the background of the recurrent parent genome. Eleven sunflower breeding genotypes with high and low oleic acid traits were obtained from the Agricultural Research Council-Grain Crops Institute (ARC-GCI) in Potchefstroom. The breeding genotypes were phenotypically characterised based on their oleic and linoleic acid levels using gas chromatography. Results demonstrated that the average mean of oleic and linoleic acid contents in high oleic acid genotypes were 72% and 17% respectively, while the average mean of oleic acid and linoleic acid contents in wild type lines were 33.5 % and 54 % respectively. These results indicated a perfect negative correlation between the amount of oleic and linoleic acids possessed in high and low oleic acid genotypes (R2 = -99.16%). Sequence characterised amplified region (SCAR) markers were tested to ascertain if any of the ten available dominant FAD2-1 markers was segregating with the high oleic acid allele. Four dominant SCAR markers (FAD2-1F4/R1; FAD2-1F4/R2; FAD2-1F13/R1; FAD2-1F14/R2) were strongly associated with the high oleic acid trait (P< 0.001). With regard to the inheritance of the high oleic acid trait, 143 plants of the F2 segregating population derived from a cross between the high oleic acid parent (AP901-95-3-4-1) and low oleic acid parent (H55-9-2-1-1) were genotyped with the four SCAR markers to determine the genetic state concerning the high oleic acid gene (Ol). Results from a Chi square analysis of the observed frequencies of each dominant FAD2-1 marker locus in 143 F2 individuals indicated that the deviation from the expected ratio of 3:1 (high to low oleic acid) was not statistically significant (P< 0.95) from the observed segregation ratio. These results were consistent with the previous finding that an incomplete dominant gene governs sunflower high oleic acid. A multiplex assay of 78 Simple sequence repeat (SSR) markers was optimised and evaluated on 143 plants of the F2 population to determine suitable SSR markers that can be used in a marker-assisted background selection. Only 14 markers were suitable for marker-assisted background selection based on their high polymorphic information content, allele frequency and maximum allele numbers. In conclusion, this study demonstrated the potential of using SSR and SCAR marker systems as a breeding tool to characterise and speed up the selection process in marker-assisted backcross breeding. / Thesis (MSc (Botany))--North-West University, Potchefstroom Campus, 2013.

Nesta Dissertação, foram sintetizadas microesferas poliméricas com propriedades magnéticas à base de metacrilato de glicidila e divinilbenzeno pela técnica de polimerização em suspensão. O material utilizado para conferir as propriedades magnéticas ao copolímero foi magnetita sintetizada no laboratório. Foram estudados os efeitos da modificação da magnetita com ácido oleico, da velocidade de agitação, do teor de agente reticulante, do teor de material magnético adicionado e do teor de agente de suspensão sobre as características das partículas poliméricas obtidas. As microesferas foram caracterizadas quanto ao seu aspecto morfológico, à estabilidade térmica, à incorporação de material magnético e quanto às suas propriedades magnéticas. A quantidade de partículas de ferro incorporadas foi afetada pela velocidade de agitação durante a síntese, pelo teor de material magnético adicionado, pela fase de dispersão do material magnético e pelo teor de monômeros no copolímero. A estabilidade térmica dos copolímeros foi afetada, principalmente, pelo teor de material magnético incorporado e pelo teor de monômeros, levando em consideração resinas com a mesma quantidade de material magnético adicionado. A magnetização de saturação para as microesferas foi afetada pelo teor de material magnético incorporado. A modificação da superfície da magnetita com ácido oleico foi considerada importante para a incorporação do material magnético na matriz do copolímero.Partículas poliméricas magnéticas com comportamento superparamagnéticos foram obtidas com morfologia esférica e magnetização de saturação de 7,11 (emu/g), utilizando razão molar de monômeros de 50/50 %, 1 % de PVA, 20 % de magnetita modificada com ácido oleico adicionada à fase orgânica e velocidade de agitação mecânica de 500 rpm / In this dissertation, polymeric microspheres with magnetic properties based on glycidyl methacrylate and divinylbenzene were synthesized by suspension polymerization technique. In order to obtain magnetic properties, magnetite particles modified by oleic acid were synthesized in laboratory. The effects of stirring rate, concentration of crosslink, the concentration of magnetite added and the concentration of stabilizer on the particles properties were studied. The magnetic microspheres were characterized according their morphology, thermal stability, incorporation of magnetite and their magnetic properties. The incorporate of iron particles content was mainly affected by stirring rate during the synthesis, by the content of magnetic material added, by the dispersion phase of magnetic material and by the monomers content in the copolymer. The thermal stability of copolymers was mainly affected by the content of magnetic material incorporated and by the monomers content, taking in account the resins with the same content of magnetic material added. The saturation magnetization for the microspheres was effected by the content of magnetic material incorporated. The modification with oleic acid was considered important to the incorporation of the magnetic material in the copolymer matrix.Magnetic polymeric particles with superparamagnetic behavior have been obtained with spherical morphology and saturation magnetization of 7.11 (emu/g). It was used monomers molar ratio of 50/50 %, 1% PVA, 20 % magnetite particles modified by oleic acid dispersion on organic phase and stirring rate of 500 rpm during the synthesis

Introdução: Acne é uma dermatose que apresenta o padrão do sebo alterado, tanto quali, quanto quantitativamente. Objetivos: Estudar as possíveis alterações quali e quantitativas dos ácidos graxos encontrados no sebo de portadores de acne vulgar graus II ou III mediante ao uso diário de limeciclina e/ou suplemento oral a base de ácidos linoleico, gamalinolênico e oleico. Métodos: Quarenta e cinco sujeitos de pesquisa masculinos, de 12 a 40 anos de idade, portadores de acne vulgar graus II ou III, submeteram-se a 90 dias de uso de: Grupo A, 300mg/dia de limeciclina; Grupo B, 540mg de ácidos gamalinolênico, 1.200mg linoleico e 510mg oleico/dia; Grupo C: Grupos A+B. A cada 30 dias, eles tinham amostra de sebo da fronte coletada para análise cromatográfica dos ácidos graxos nele presentes. Resultados: Quarenta sujeitos de pesquisa (88,9%) concluíram o estudo, os quais ingeriram todas as doses dos produtos, sem apresentarem eventos adversos em qualquer dos Grupos. O número de comedões, pústulas e cistos reduziu com o tempo (p<0,001, para todos), nos três Grupos. Com relação ao número total de lesões, houve uma maior quantidade de lesões em pacientes do Grupo B, quando comparados aos do Grupo A (p=0,033) e aos do Grupo C (p=0,030). Sete ácidos graxos apresentaram mudanças de seu padrão durante o estudo. De um modo geral, as mudanças que se tornaram mais evidentes foram: 1) a concentração de esqualeno no SB não reduziu em qualquer Grupo de estudo; 2) C12:0, C14:0 e C16:1 tiveram suas respectivas concentrações aumentadas nos três Grupos com o tempo de terapêuticas; 3) há indicativo de aumento de C18:1n9c+C18:1n9t na associação das duas classes terapêuticas estudadas; 4) limeciclina e/ou ingestão de ácido linoleico não aumentaram a participação do ácido linoleico no sebo; 5) ácido -linolênico teve sua concentração aumentada e, depois diminuída com o uso de LM e/ou com sua própria suplementação oral. Conclusões: A administração diária de limeciclina e/ou ácidos gamalinolênico, linoleico e oleico pode alterar o comportamento de alguns dos ácidos graxos presentes no sebo de pacientes portadores de acne vulgar graus II ou III. Os ácidos gamalinolênico, linoleico e oleico, se no uso sistêmico, não são considerados agentes terapêuticos na abordagem da acne; mais estudos precisam ser realizados a fim de se inferir a existência de possível benefício clínico de seu uso isolado e/ou associado na abordagem desta dermatose / Introduction: Acne is a dermatosis that presents an altered sebum pattern, quantitatively and qualitatively. Objectives: To study the possible quantitative and qualitative changes of fatty acids found in the sebum of patients with acne vulgaris grade II or III, through the daily use of lymecycline and/or oral supplementation based on linoleic, gamma-linolenic, and oleic acids. Methods: Fortyfive male research subjects, ages 12 to 40, presenting acne vulgaris grade II or III, were submitted to a 90-day use of: Group 1, 300mg of lymecycline per day; Group 2, 540mg of gamma-linolenic acid, 1,200mg of linoleic acid, and e 510mg of oleic acid per day; Group 3: Groups A+B. Every 30 days, a sample of the sebum of their forehead was collected for chromatographic analysis of the fatty acids contained therein. Results: Forty research subjects (88.9%) concluded the study. They ingested all dosages of the products, without presenting side effects in any of the Groups. The number of comedones, pustules, and cysts reduced with time (p<0.001, for all), in all the 3 Groups. With respect to the total number of lesions, Group B´s patients presented a larger quantity of lesions, as compared to those of Group A (p=0.033) and Group C (p=0.030). Seven fatty acids presented pattern changes during the study. In general, the changes that became more evident were: 1) the squalene concentration in the sebum did not diminish in any Group under study; 2) C12:0, C14:0, and C16:1 had their respective concentrations increased in the 3 Groups over the time of the treatments; 3) there is an indication for increasing of C18:1n9t+C18:1n9c when both of therapies are associated; 4) lymecycline and/or the ingestion of linoleic acid did not increase the participation of linoleic acid in the sebum; and 5) gama-linolenic acid had its concentration increased during the first 60-day and diminished during the last 30-day therapies period using lymecycline and/or with its own oral supplementation. Conclusions: The daily administration of lymecycline and/or gamma-linolenic, linoleic, and oleic acids may alter the behavior of some fatty acids present in the sebum of patients with acne vulgaris grade II or III. Gamma-linolenic, linoleic, and oleic acids, under systemic use, are not considered therapeutic agents in the treatment of acne; more studies need to be carried out in order to infer the existence of a possible clinical benefit of their isolated use and/or association in the treatment of this dermatosis

Made available in DSpace on 2017-07-10T17:59:27Z (GMT). No. of bitstreams: 1 Ana Carolina de Araujo Abdala.pdf: 1086977 bytes, checksum: 3669a77a33625e3d6a3660105a7eb19d (MD5) Previous issue date: 2013-02-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The current work aimed to investigate the production of ethyl esters which result from the esterification reactions of oleic acids (AO) and transesterifiction of residual fried oils (ORF), both in supercritical ethanol throught non-catalic method. The experiments were carried out in a packed bead reactor operated in continuous mode. The esterification reactions were carried out under a temperature from 200 to 325ºC, pressure of 15 and 20 MPa and molar reason AO: ethanol in the range of 1:3 to 1:12. From the results on, was possible to note, that the temperature and the pressure influenced positively the conversion on the esterification reaction of oleic acid, with an income of 93, 5%, observed under 325°C and 20Mpa, in a reaction that last 40 minutes. The excess of alcohol in the reactional system didn´t provide significant differences in the conversions, with the optimum molar reason, defined in 1:6 (AO: ethanol). The transesterification reactions, were carried out with pauses of temperatures from 275 to 325ºC, pressure fixed of 20MPa, adopting the mass reason of ORF to ethanol of 1:0.5 and 1:1, varying the residence time, leading the determination of great conditions to the ethyl esters synthesis. Notable results in the alcoholysis reactions were observed at 325ºC, mass ratio of ORF to ethanol at 1:1 and residence time of 40 minutes. Using the molar ratio ORF: ethanol selected as the best suitable, was also evaluated the effect of the water addition to the reactional medium (0, 5 and10% of water relative to the ethanol mass), in order to investigate the technical viability of the use of low quality and costs of the raw materials containing water in the composition. The effect of addition of deco- hexane solvent (0, 5, 10 and 20% of hexane compared to the substrates mass), as well the effect of addition of soy bio-fuel (0, 20 and 40% of soy bio-fuel compared to substrates mass), were also investigated, in order to improve the performance of the reaction. Notable incomes were observed in the reaction with 5% of water addition and 20% of hexane. The best results related to the soy bio-fuel addition to the reactional medium were observed in the reactions carried out with 40% of soy bio-fuel, however, taking into consideration the amount of esters added to the process, the condition considered great was with 20% soy bio-fuel.. From the best conditions of the process, the kinetic daalcoholise super-critical was investigated with the reactions conducted with the residence time from 0 to 70 minutes and the notable results were: 83% in ethyl esters, obtained in 300ºC, 70 minuts of reaction, using 5% of water, 87% in ethyl esters observed in 300ºC, 70minutes of reaction, using 20% of hexane and 82% in ethyl esters obtained in 325ºC, 50 minutes of reaction, using 20% of soy bio-fuel. Lastly, the stability of the daalcoholise reactional medium was investigated. Temperatures of reaction till to 300ºC resulted in decomposition <10% with residence time of 20 minutes. However, the reactions with longer residence time, showed a higher ratio of decomposition of the constituents of the reactional medium. / O presente trabalho teve como objetivo investigar a produção de ésteres etílicos nas reações de esterificação do ácido oleico (AO) e transesterificação de óleo residual de fritura (ORF), ambas em etanol supercrítico pelo método não catalítico. Os experimentos foram realizados em um reator tubular com leito empacotado operado em modo contínuo. As reações de esterificação foram conduzidas com temperatura na faixa de 200 a 325ºC, pressão de 15 e 20 MPa e razão molar AO:etanol na faixa de 1:3 a 1:12. A partir dos resultados, foi possível observar que a temperatura e a pressão influenciaram positivamente a conversão nas reações de esterificação do ácido oleico, com rendimentos de 93,5%, observados a 325ºC e 20 MPa, em 40 minutos de reação. Já o excesso de álcool no sistema reacional não proporcionou diferenças significativas nas conversões, com a razão molar ótima, definida em 1:6 (AO:etanol). As reações de transesterificação foram conduzidas no intervalo de temperatura de 275 a 325ºC, pressão fixa de 20 MPa, adotando razão mássica de ORF para etanol de 1:0,5 e 1:1, variando-se o tempo de residência, possibilitando a determinação das condições ótimas para a síntese de ésteres etílicos. Resultados apreciáveis nas reações de álcoolise foram verificados em 325ºC, razão mássica de ORF para etanol de 1:1 e tempo de residência de 40 minutos. Utilizando a razão mássica ORF:etanol selecionada como a mais adequada, ainda foi avaliado o efeito da adição de água ao meio reacional (0, 5 e 10% de água em relação à massa do etanol), visando investigar a viabilidade técnica da utilização de matérias-primas de menor qualidade e menor custo que contenham água em sua composição. O efeito da adição de co-solvente hexano (0, 5, 10 e 20% de hexano em relação à massa dos substratos) bem como o efeito da adição de biodiesel de soja (0, 20 e 40% de biodiesel de soja em relação à massa dos substratos) também foram investigados, buscando melhorar o desempenho da reação. Rendimentos apreciáveis foram observados nas reações com 5% de adição água e 20% de hexano. Os melhores resultados referentes à adição de biodiesel de soja ao meio reacional foram observados nas reações conduzidas com 40% de biodiesel de soja, porém, levando-se em conta a quantidade de ésteres adicionada ao processo, a condição considerada ótima foi de 20% de adição de biodiesel de soja. A partir das melhores condições de processo, a cinética da álcoolise supercrítica foi investigada com reações conduzidas com tempo de residência na faixa de 0 a 70 minutos e os resultados apreciáveis foram de: 83% em ésteres etílicos, obtidos em 300°C, 70 minutos de reação, utilizando 5% de água, 87% em ésteres etílicos observados em 300°C, 70 minutos de reação, utilizando 20% de hexano e 82% em ésteres etílicos alcançados em 325°C, 50 minutos de reação, utilizando 20% de biodiesel de soja. Por fim, a estabilidade dos componentes do meio reacional da alcoólise foi investigada. Temperaturas de reação de até 300ºC resultam em decomposições <10% com tempo de residência de 20 minutos. Porém, as reações com tempos de residência mais longos, apresentaram taxas de decomposição dos constituintes do meio reacional mais elevadas.

L’accumulation de lipides chez une espèce levurienne Yarrowia lipolytica souche sauvage a été caractérisée par l’analyse dynamique et systémique des différents états métaboliques identifiés lors des cultures sous conditions environnementales parfaitement maitrisées, à hautes densités cellulaires selon deux stratégies bien distinctes. En premier lieu sur substrat osidique avec le phosphore comme élément inducteur de l’accumulation de lipides, stratégie originale pour déclencher l’accumulation de lipides chez cette souche. Et deuxièmement sur co-susbtrats glucose et oléate et sans aucune limitation nutritionnelle.Ces stratégies de conduites ont permis de dégager les points suivants :- La limitation phosphore déclenche une accumulation en lipides mais aussi en polysaccharides de réserves mobilisables mais non transitoire contrairement à la limitation azote.- La teneur en phosphore de la biomasse catalytique est très variable. De ce fait, le taux de croissance de la biomasse catalytique n’est pas contrôlable par le débit en phosphore.- Le phosphore joue un rôle dans la régulation de l’entrée de glucose dans la cellule, et permet d’éviter la production de citrate lorsque les voies de production de biomasse et de lipides sont en débordement sur une large gamme de rapport C/P (de 0 à 8000 Cmole.mole-1).- La capacité maximale d’accumulation en réserves carbonées chez Y. lipolytica wT est identique quelle que soit la méthode d’accumulation (limitation azote, limitation phosphore, co-substrats glucose / oléate) et est égale à 0,5 Cmole/CmoleX-1. Il existe donc un phénomène de régulation de la levure encore inconnu et limitant l’accumulation en réserves carbonées chez cette souche.Ces résultats ont permis d’identifier des points clés dans l’accumulation en réserves carbonées de cette espèce levurienne et de proposer un mode de conduite original faisant l’objet d’un dépôt de brevet / Lipid accumulation by the yeast Yarrowia lipolytica wT was characterized by dynamic and systemic analysis of different metabolic states in a microbial culture under fully controlled environmental conditions with high cell concentration and under two different strategies:Glucose as the substrate and phosphorus limitation as an inducer of lipid accumulation, an original strategy for lipid accumulation in Y. lipolytica wT.A co-substrate strategy with glucose and oleic acid and without any nutritional limitation.These strategies allowed showing the following points:- Phosphorus limitation triggers a lipid accumulation and a non-transient accumulation of reserve polysaccharide that can be consumed by biomass when necessary, contrary to nitrogen limitation- Phosphorus rate in catalytic biomass shows great variations. Catalytic growth rate cannot be governed by phosphorus input. - Phosphorus has a role in regulating cellular glucose uptake and allows avoiding citric acid production due to overflow of carbon input over a large range of C/P ratios (0 to 8000 Cmol.mol-1)- Maximum capacity of reserve carbon accumulation in Y. lipolytica wT is similar for any culture strategy tested (under nitrogen limitation, phosphorus limitation or with glucose and oleic acid co-substrates) and is equal to 0,5 Cmol/CmolX-1. There is an unknown phenomenon of carbon regulation limiting reserve carbon accumulation in Y. lipolytica wT. Results allowed identifying key points in reserve carbon accumulation in this particular yeast strain and suggesting an original process, claim of a patent

La neurogenèse est présente, dans le cerveau adulte, dans la zone sous-ventriculaire (ZSV) encadrant les ventricules latéraux et dans le gyrus dentelé (GD) de l’hippocampe, permettant l’apprentissage, la mémoire et la fonction olfactive. Ces micro-environnements possèdent des signaux contrôlant l’auto-renouvellement des cellules souches neurales (CSN), leur prolifération, leur destin et leur différenciation. Or, lors du vieillissement, les capacités régénératives et homéostatiques et la neurogenèse déclinent. Les patients atteints de la maladie d’Alzheimer (MA), comme le modèle animal reproduisant cette maladie (3xTg-AD), montrent une accélération des phénotypes liés au vieillissement dont une diminution de la neurogenèse. Notre hypothèse est que la découverte des mécanismes affectant la neurogenèse, lors du vieillissement et de la MA, pourrait fournir de nouvelles cibles thérapeutiques pour prévenir le déclin cognitif. Les études sur l’âge d’apparition et les mécanismes altérant la neurogenèse dans la MA sont contrastées et nous ont guidé vers deux études. L’examen des changements dans les étapes de la neurogenèse lors du vieillissement et du développement de la neuropathologie. Nous avons étudié la ZSV, les bulbes olfactifs et le GD de souris femelles de 11 et 18 mois, et l’apparition des deux pathologies associées à la MA : les plaques amyloïdes et les enchevêtrements neurofibrillaires. Nous avons découvert que les souris 3xTg-AD possèdent moins de cellules en prolifération, de progéniteurs et de neuroblastes, induisant une diminution de l’intégration de nouvelles cellules dans le GD et les bulbes olfactifs. Notons que le taux de neurogenèse chez ces souris de 11 mois est similaire à celui des souris de phénotype sauvage de 18 mois, indiquant une accélération des changements liés au vieillissement dans la MA. Dans la ZSV, nous avons aussi démontré une accumulation de gouttelettes lipidiques, suggérant des changements dans l’organisation et le métabolisme de la niche. Enfin, nous avons démontré que le déficit de la neurogenèse apparait lors des premières étapes de la MA, avant l’apparition des plaques amyloïdes et des enchevêtrements neurofibrillaires. A l’examen des mécanismes inhibant la neurogenèse lors de la MA, nous voyons que chez des souris de 5 mois, le déficit de la neurogenèse dans la ZSV et le GD est corrélé avec l’accumulation de lipides, qui coïncide avec l’apparition du déclin cognitif. Nous avons aussi découvert que dans le cerveau humain de patients atteints de la MA et dans les 3xTg-AD, des gouttelettes lipidiques s’accumulaient dans les cellules épendymaires, représentant le principal soutien des CSN de la niche. Ces lipides sont des triglycérides enrichis en acide oléique qui proviennent de la niche et pas d’une défaillance du système périphérique. De plus, l’infusion locale d’acide oléique chez des souris de phénotype sauvage permet de reproduire l’accumulation de triglycérides dans les cellules épendymaires, comme dans la MA. Ces gouttelettes induisent un dérèglement de la voie de signalisation Akt-FoxO3 dans les CSN, menant à l’inhibition de leur activation in vitro et in vivo. Ces résultats permettent une meilleure compréhension de la régulation de la neurogenèse par le métabolisme lipidique. Nous avons démontré un nouveau mécanisme par lequel l’accumulation des lipides dans la ZSV induit une inhibition des capacités de prolifération et de régénération des CSN lors de la MA. Les travaux futurs permettront de comprendre comment et pourquoi le métabolisme lipidique du cerveau est altéré dans la MA, ce qui pourrait offrir de nouvelles voies thérapeutiques pour la prévention et la régénération. / In the adult brain, neurogenesis continues in the subventricular zone (SVZ) surrounding the lateral ventricles and the dentate gyrus (DG) of the hippocampus where it plays a critical role in learning, memory, and olfactory function. Within these microenvironments, combinatorial signals control neural stem cell (NSC) self-renewal, proliferation, fate determination and differentiation. Unfortunately, during aging, neurogenesis declines along with many other homeostatic and regenerative capabilities. Furthermore, Alzheimer’s disease (AD) patients and many AD models show an acceleration of several aging related phenotypes including neurogenesis. We hypothesize that uncovering how neurogenesis is affected during aging and in AD will provide novel targets for prevention of cognitive decline. However, conflicting findings including the age of onset and the mechanisms altering neurogenesis in AD propelled us to perform the two following studies. First, we examined the various steps of neurogenesis and how they change as a result of aging, neuropathology development, and neurogenic niches. We studied neurogenesis in the SVZ, olfactory bulb, and DG of 11- and 18-month-old female mice and simultaneously measured the stages of the two major AD-associated pathologies, amyloid plaques and neurofibrillary tangles. We found that, 3xTg-AD mice had fewer proliferating cells, neural progenitors and neuroblasts, resulting in decreased numbers of adult-born cells added to the dentate granule cell layer and the olfactory bulbs. Interestingly, the levels of neurogenesis in 11-month-old 3xTg mice were similar to those in 18-month-old WT mice, indicating an acceleration of aging-related changes in neurogenesis. Interestingly, we found that the deficits in neurogenesis appear at early stages of AD-associated pathologies, before the appearance of the hallmark Aβ plaques and neurofibrillary tangles. Instead, we found a pronounced accumulation of large lipid droplets, suggestive of significant organizational and metabolic changes (Chapter 2). Second, we examined the mechanisms inhibiting neurogenesis in AD. Studying young 5-month-old mice, we found that deficits in SVZ and DG neurogenesis still correlated with extensive lipid accumulation coinciding with the onset of cognitive decline. Importantly, we found that postmortem AD brains and 3xTg-AD mice accumulate neutral lipids within ependymal cells, the main support cell of the SVZ niche. Using novel mass spectrometry techniques, we identified these lipids as oleic acid-enriched triglycerides. Moreover, analysis of plasma, cerebrospinal fluid, and microdissected SVZs showed that these lipids originate from niche-derived rather than peripheral lipid metabolism defects. Remarkably, locally increasing oleic acid in wild-type mice was sufficient to recapitulate the AD-associated ependymal triglyceride phenotype and led to a de-regulation of the Akt-FoxO3 NSC preservation pathway, and inhibition of NSC activation in vitro and in vivo (Chapter 3). Together, this work suggests a novel mechanism of cognitive defects. Specifically, lipid accumulation within SVZ niche cells during early adulthood inhibits the proliferative and regenerative capacity of NSCs in AD. Future work aimed at understanding how and why brain lipid metabolism is altered in AD could provide therapeutic targets for preventative and regenerative strategies for those suffering from AD.

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Nanopartiklar (NP) erbjuder unika möjligheter för medicinska tillämpningar, inklusive kontrollerad frisättning av cancerläkemedel, användning som bildkontrast vid avbildningsprocedurer eller hypertermisk behandling av cancerceller. Flash nanoprecipitation (FNP) producerar NPs för att kombinera dessa tillämpningar i en snabb, billig och skalbar beläggningsprocess. Användning av FNP med en Multi-Inlet Vortex Mixer (MIVM) är en lovande metod för att enkelt belägga hydrofoba oljesyra järnoxid NP (IONP) med olika biokompatibla block-copolymerer. Amfifila block-copolymerer baserade på hydrofil polyetylenglykol (PEG) och hydrofob poly(laktid) (PLA), poly(laktid-co-glykolid) (PLGA) eller poly(kaprolakton) (PCL) syntetiserades framgångsrikt. Den organiska katalysatorn 1,8-diazabicyclo[5.4.0]undec-7-en (DBU) användes för att öka biokompatibiliteten hos de resulterande polymererna PEG-PLA, PEG-PL7,5KG2,5KA och PEG2K-PCL2K. Syntes av hydroxylterminerad poly(akrylsyra) (PAA-OH) följt av polymerisation med PLGA prövades. De amfifila blockpolymererna användes i kombination med stabilisatorn polysorbat 80 (Tween80®) i FNP för att bilda nakna polymera NP med en MIVM som reaktor. DLS och STEM bekräftade partikelstorlekar mellan 50 - 100 nm. Tillsatsen av 13 ± 2 nm hydrofoba oljesyra-IONPs gav en ökning av partikelstorleken samt en ökning av partikelstabiliteten över tid. STEM-bilder visade att enstaka IONPs fästs på utsidan av de polymera NPs. Hydrofoba interaktioner mellan polymeren och oleinsyra-IONPs är möjliga. För att uppnå inkapsling av oljesyra-IONPs bör justeringar av processparametrarna för FNP övervägas i framtida forskning. Ytterligare experiment krävs för att utforska möjliga läkemedelstillsatser, frisättningsmekanismer och hypertermi hos de polymerbelagda IONP-partiklarna. / Nanoparticles (NPs) offer unique possibilities for medical applications, including the controlled release of cancer drugs, the use as imaging contrast during imaging procedures or the hyperthermic treatment of cancer cells. Flash nanoprecipitation (FNP) produces NPs to combine these applications in a fast, cheap, and scalable coating process. The use of FNP with a Multi-Inlet Vortex Mixer (MIVM) is a promising method to easily coat hydrophobic oleic acid iron oxide NPs (IONPs) with various biocompatible block-copolymers. Amphiphilic block-copolymers based on hydrophilic polyethylene glycol (PEG) and hydrophobic poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA) or poly(caprolactone) (PCL) were successfully synthesized. The organic catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was used to increase biocompatibility of the resulting polymers PEG-PLA, PEG-PL7.5KG2.5KA and PEG2K-PCL2K. The synthesis of hydroxyl terminated poly(acrylic acid) (PAA-OH) followed by the polymerization with PLGA was attempted. The amphiphilic block-copolymers were used in combination with the stabilizer polysorbate 80 (Tween80®) in FNP to form bare polymeric NPs using a MIVM as the reactor. DLS and STEM confirmed particle sizes between 50 - 100 nm. The addition of 13 ± 2 nm hydrophobic oleic acid IONPs yielded an increase in particle size as well as increase in particle stability over time. STEM images showed attachment of single IONPs to the outside of the polymeric NPs. Hydrophobic interactions between the polymer and oleic acid IONPs are possible. To achieve encapsulation of the oleic acid IONPs, adjustments to the process parameters of FNP should be considered in future research. Additional experiments are required to explore possible drug addition, release mechanisms and hyperthermia behavior of the polymer coated IONPs particles.