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Coussa-Charley, Michael. "A novel «in vitro» mucosal gut bacterial adhesion model". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106420.
Abstract (sommario):
The gut bacterial system is truly a dynamic, complex organ. Although there is a constant flux of activity, the microflora can be considered as a bioreactor at a quasi-steady state throughout a person's life. In fact, the relative composition of different bacterial genera can lead directly to health or disease. By understanding how the gut is colonized and what can be administered to alter overall composition, one would be able to use the gut as a legitimate target for drug delivery. In vitro gut adhesion models have been developed exactly for this purpose however have several limitations. In this thesis, an attempt has been made to develop a new gut adhesion model that included several key components associated with bacterial adhesion to the gut mucosal lining. For this, mucus-coated beads were used to simulate the mucosal lining. As well, beads were incubated with intestinal bacteria from a fresh human fecal sample. In this way, one would be study to observe the interactions between different bacteria within the gut, and the interaction between these commensal bacteria and any potential therapeutic design. This new model is a continuous model, allowing for real-time analysis of the mucosal-associated flora. This will allow its use to understand the effect of different external factors over an indefinite experimental period on gut bacterial adhesion. Results demonstrated that this model was highly effective in providing a stable microbial ecosystem for a single bacterial strain or for a large number of aerobic or anaerobic bacteria. The model was also shown to perform very well over long-term studies. This model has numerous applications and includes the investigation of probiotics, prebiotics, and antibiotics on altering a mucosal-associated microflora. In this thesis, an attempt has been made to develop a model that included several key components associated with bacterial adhesion to the gut mucosal lining. For this, mucus-coated beads were used in order to simulate the mucosal lining. As well, beads were incubated with intestinal bacteria from a fresh human fecal sample. In this way, one would be study to observe the interactions between different bacteria within the gut, and the interaction between these commensal bacteria and any potential therapeutic design. Finally, the model is continuous, allowing for real-time analysis of the mucosal-associated flora while at the same time, allow the researcher to understand the effect of different external factors over an indefinite experimental period. Results demonstrated that the platform was highly effective in providing a stable microbial ecosystem for a single bacterial strain or for a large number of aerobic or anaerobic bacteria. The model was also shown to perform very well over long-term studies. This model has numerous applications and includes the investigation of probiotics, prebiotics, and antibiotics on altering a mucosal-associated microflora.La flore intestinale est un organe dynamique et complexe qui se trouve à l'intérieur du tube digestif. Bien qu'il y ait un flux d'activité constant, la microflore peut être considérée comme un bioréacteur ayant un quasi état d'équilibre durant toute la vie d'une personne. En fait, la composition relative des différents types de bactéries est directement reliée à la santé de l'individu. En comprenant comment l'intestin est colonisé et ce qui peut être administré pour modifier sa composition générale, on serait en mesure de l'utiliser comme une cible légitime pour la livraison de médicaments. Des modèles in-vitro d'adhérence intestinale ont été mis au point exactement à cette fin. Un modèle comprenant plusieurs éléments clés associés à l'adhésion bactérienne sur la muqueuse intestinale a été développé pour cette thèse. Tout d'abord, des capsules d'alginates recouvertes de mucus ont été utilisées afin de simuler la muqueuse intestinale. En outre, ces capsules ont été incubés avec les bactéries intestinales à partir d'un échantillon frais provenant des fécales humaines. De cette façon, on serait en mesure d'observer les interactions entre les différentes bactéries dans l'intestin, et l'interaction que ces bactéries ont avec tout autre traitement. Finalement, ce modèle est continu, permettant une analyse en temps réel de la muqueuse associée à la flore et nous permet de comprendre l'éffet de différents facteurs environnementaux sur de longues périodes de temps. Les résultats ont démontré que la plate-forme a été très efficace dans la fourniture d'un écosystème stable microbien pour une seule souche bactérienne ou pour un grand nombre de bactéries aérobies ou anaérobies. Le modèle a également montré de très bonnes performances au cours des études à long terme en utilisant plusieurs échantillons pendant l'expérience. Les applications de ce modèle sont pratiquement infinies, et permettent notamment d'enquêter sur l'effet que les probiotiques, les prébiotiques, et les antibiotiques ont sur la modification d'une microflore associée à la muqueuse.
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GARUGLIERI, ELISA. "EFFECTS OF SILVER NANOPARTICLES ON IN VITRO GUT MICROBIAL MODELS AND OTHER ANAEROBIC ENVIRONMENTS". Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/488359.
Abstract (sommario):
The impacts of AgNPs on both natural and engineered ecosystems is a topic of outstanding importance having socio-economic consequences on medical, industrial and environmental fields. Silver nanoparticles are widely used as antimicrobial agents in consumer products for domestic, environmental, medical, and industrial applications. Release of AgNPs from nanoenabled products has been observed, and the potential impacts of such releases on a wide variety of organisms at many trophic levels have been recognized. However, there has been little exploration of the impact of AgNPs on the microflora associated with living organisms and their environments. For instance, of special interest is the effects on the human microbiota considering the range of consumer goods that could be directly or indirectly ingested.
Furthermore, most of the studies concerning toxic effects of AgNPs on biologic systems consider high NPs concentrations, while the effects of real environmental and dietary concentrations are still poorly investigated.
Thus, the principal aim of my PhD project was to provide science-based evidence needed to elucidate the effects of sub-lethal concentrations of AgNPs on bacterial ecosystems, with the final goal of creating the scientific know-how to master biological processes and develop leading edge methodologies vital for the nanosafety assessment. In particular, I focused my attention on studying the response of in vitro gut microbial models and other anaerobic ecosystems to acute and chronic AgNPs exposures at vicinity of environmental and human intake concentrations.
To this end, three different systems have been investigated:
1) Planktonic cultures of two well characterized bacterial strains (Chapter 3). The aim of this work was to compare the impacts of different sub-lethal AgNPs concentrations on the growth kinetic, adhesion ability, oxidative stress, and phenotypic changes of model bacteria under both aerobic and anaerobic conditions. To gain a mechanistic insight, the experiments were conducted using two differ-ent microbial model systems: (i) a Gram-negative bacterium Escherichia coli representative of human intestinal flora and responsible for infection, and (ii) a Gram-positive bacterium Bacillus subtilis, wide-ly distributed in soil, freshwater, marine environments and used as a probiotic. I also established the minimum AgNPs sub-lethal concentration able to evoke effects on planktonic bacteria.
2) Biofilm cultures of the model bacterium Escherichia coli and their interplays with CaCo2 cells system (Chapter 4). The goal was to investigate the physiological response of a mono-species gut bio-film to chronic and acute exposure to 1 μg/mL AgNPs, and how this physiological response affected the intestinal epithelial cells. To study the interplays among sub-lethal concentrations of AgNPs, the gut biofilm and its host, a simplified experimental lab model system was designed and tested.
3) Human fecal microbiota in combination with the probiotic Bacillus subtilis (Chapter 5). I aimed to explore possible impacts of single and combined treatments of dietary AgNPs and the probiotic Ba-cillus subtilis to the composition, functional performances and microbial metabolites of in-vitro batch fecal fermentation models to mimic the human digestive tract environment. Furthermore, I investigat-ed their potential cytotoxicity and genotoxicity on the human intestinal Caco-2 cell line.
These experimental designs were created to investigate microbial ecosystems of increasing complexity, assessing whether sub-lethal concentrations of AgNPs influence microbial physiology and behavior in such settings.
3
Gérémie, Lauriane. "Development of an in-vitro intestinal model featuring peristaltic motion". Thesis, Sorbonne université, 2019. http://accesdistant.sorbonne-universite.fr/login?url=http://theses-intra.upmc.fr/modules/resources/download/theses/2019SORUS118.pdf.
Abstract (sommario):
Le Gut-on-chip fait partie d'un thème de recherche plus générale, appelez Organ-on-chip qui a pour objectif de développer des modèles in-vitro qui récapitulent des caractéristiques essentielles de l'organe d'intérêt. Dans le cas de l'intestin, les Gut-on-chip plateformes ont été principalement développés pour reconstituer soit l'architecture 3D de l'intestin, soit sa dynamique et plus particulièrement le péristaltisme. Durant ma thèse j'ai développé une nouvelle et polyvalente Gut-on-chip, présentant ces deux aspects du micro-environnement intestinale. Cette Peristalsis-on-chip nous a permis d'étudier l'influence du mouvement péristaltique sur le comportement cellulaire en fonction de la géométrie de la structure. Pour cette étude nous avons ensemencé des cellules Caco2 sur des substrats 2D ou 3D recouvert de laminine et les avons soumis à un étirement cyclique (à 0.2 Hz et 10\%) pendant 2, 5, 8, 16, 24 et 48 heures. Lors de ces expériences nous avons pu observer une réorientation cellulaire perpendiculaire à l'axe d'étirement que nous avons caractérisé en fonction des conditions de recouvrement, de la confluence initiale, du temps d'étirement et de la géométrie de la structure. Il est intéressant de noter que la réponse cellulaire la plus importante a été obtenue par la combinaison de la géométrie 3D et de l'étirement, ce qui illustre bien le besoin de ces deux éléments pour mieux mimer les conditions intestinales in vivoMy PhD work is part of the organ-on-chip field, and more precisely part of the gut-on-chip field. It is in line with the main objective of this field, which is the development of in-vitro models recapitulating as faithfully as possible the intestinal micro-environment. Through my PhD work I first developed a versatile gut-on-chip platform recapitulating the intestinal 3D architecture as well as its dynamic micro-environment. Therefore, this platform allows us to study the influence of the intestinal dynamic, especially the peristalsis, on cellular behavior in function of the 3D architecture of the scaffold. For this study Caco2 cells have been seeded either on a 2D or a 3D scaffold coated with laminin and submitted to a cyclic stretching (at 0.2 Hz and 10%) for 2, 5, 8, 16, 24 and 48 hours. Our main observation was the cellular reorientation induced by the stretching, therefore we characterized the cell behavior in function of the coating condition, the initial confluency, the stretching time and the scaffold geometry. Interestingly, the strongest cellular response was obtained when the 3D geometry and the stretching was combined illustrating the need of these two stimuli to better mimic the intestinal in vivo conditions
4
Crowther, Grace. "Development and characterisation of an in vitro human gut model to study the biofilm mode of growth of Clostridium difficile and the indigenous gut microbiota". Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5736/.
Abstract (sommario):
Clostridium difficile infection (CDI) is associated with significant patient morbidity, mortality and financial burden. Until recently, antimicrobial treatment options were limited to metronidazole and vancomycin, but both agents are associated with recurrence rates of approximately 20%. The human gastrointestinal tract harbours a complex microbial community which exist in planktonic and sessile form. Sessile organisms are known to cause chronic infection such as cystic fibrosis. Mucosal biofilms exist on surfaces of the gastrointestinal tract, but the existence and role of C. difficile in these structures remains unknown. The present study describes the process undertaken to adapt and validate an in vitro human gut model to study the planktonic and biofilm mode of growth of C. difficile and the indigenous gut microbiota. A triple stage chemostat gut model, primed with a human faecal emulsion was used to induce and treat simulated CDI. A glass rod system was incorporated into the third vessel to facilitate the formation and subsequent analysis of mixed-species biofilms. Sessile and planktonic gut microbiota and C. difficile populations within an in vitro gut model are similar in the absence of antimicrobial intervention. Differences in behaviours of the two modes of growth are evident upon antimicrobial administration, with a delayed response in sessile populations. The sessile mode of growth of C. difficile within mature biofilm structures is complex and variable. Within the redesigned biofilm gut model, sessile C. difficile remained in spore form for the duration of the experiment, despite induction of simulated CDI, treatment of CDI and recurrence of disease evident within planktonic communities. Recalcitrant spores within biofilms may be seeded into the planktonic fluid of the gut model after apparent successful initial treatment and contribute to recurrence of CDI. The role of sessile C. difficile in recurrent CDI should be further investigated.
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VERDILE, NICOLE. "MORPHOLOGICAL AND FUNCTIONAL CHARACTERIZATION OF THE RAINBOW TROUT GUT (ONCORHYNCHUS MYKISS) TO DEVELOP A PREDICTIVE IN VITRO INTESTINAL MODEL". Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/928771.
Abstract (sommario):
To obtain an adequate comprehension of the intestinal morphology and function, I performed a detailed morphological evaluation of the intestinal epithelial cells lining the rainbow trout gut. This was obtained through histological, histochemical and immunohistochemical observation, accurate stereological analysis, morphometric measurements, and fine qualitative and quantitative characterization of goblet cells secreting activity at typical time points of in vivo feeding trials (50, 150 and 500 g). The gross anatomy of the rainbow trout gut corresponds to the general description of the organ in teleost fish. It consists of a proximal intestine with annexed pyloric caeca, easily distinguishable from the distal intestine, which presents a larger diameter, dark pigmentation, and circularly arranged blood vessels. Microscopically, the proximal intestine was characterized by simple folds whereas the distal intestine displayed a more complicated mucosa arrangement. In fact, this latter, was defined by the presence of peculiar complex folds from which other simpler originated. While only minor changes took place along the classical time points of in vivo feeding trials, two morphological and functional compartments not linearly distributed were observed along the trout gut. The first included the proximal intestine and the apical part of the complex folds of the distal portion. This was characterized by abundant and actively secreting goblet cells, no pinocytotic vacuoles, high expression of three defined functional enterocytes markers (PepT1, Sglt1 and Fabp2), low proliferation rate, few round apoptotic cells and an extended area of fully differentiated cells. The other, comprised the basal part of the complex folds and the pyloric caeca and was defined by few goblet cells with deflated mucus vacuoles, pinocytotic vacuolization, weak expression of the classical functional enterocytes markers, high proliferation and apoptotic rate and by a smaller extension of fully differentiated epithelial cells. The presence of these Chapter 2 23 distinct morphological and functional compartments suggest that digestive and absorptive function are mingled along the trout gut and that possibly in this species, the proximal intestine extend itself in the distal portion of the intestine to maximize its absorptive capacity [65]. To achieve a better knowledge of the cellular and molecular mechanisms implied in the intestinal homeostasis preservation and to further investigate the two different renewal rate previously observed, I performed a detailed qualitative description of the organization of the intestinal epithelial stem cell (IESC) niche and their regulatory molecules. To this end, the typical mouse ISCs markers (LGR5, HOPX, SOX9, NOTCH1, DLL1, and WNT3A) have been selected as target genes, and subsequently their expression have been localized along the different portions of the trout gut trough in situ hybridization. All the target genes were expressed also in rainbow trout intestine. However, considering their typical position in mouse, we highlighted substantial differences. Lgr5+ cells were rare but surprisingly in RT were located along the folds’ stroma rather than restricted in the crypt epithelium. The folds’ connective axis hosted also scattered notch1+ as well as wnt3a+ cells where they colocalized with lgr5+ cells. Interestingly, also in mouse these markers colocalize, even if this occurs in the epithelium lining the crypt base. Moreover, close to lgr5+ stromal cell population we observed elongated, epithelial cells expressing dll1. This marker in mouse is selectively expressed by Paneth cells at the crypt bottom. Despite the different spatial position of dll1+ cells in mouse and rainbow trout, it is interesting to note that in both species lgr5 and dll1 are expressed by cells topographically close each other, suggesting a functional interaction. Moreover, the epithelium lining the intestinal folds base in rainbow trout showed exclusively positivity to sox9. Particularly, here, we observed slender cells expressing sox9 at high level, strongly reminiscent of the crypt base columnar cells (CBCs) cells described in mouse intestinal crypts. Sox9 expression tended to disappeared outside del fold base to give way to hopx which was abundantly detected along the folds rather than restricted to the +4 position as described in mouse. Based on these observation, it is reasonable to assume that in this species Chapter 3 66 the functional equivalent of lgr5 is sox9, since sox9+ cells showed the typical location and shape of CBCs in mouse intestine. Whereas, lgr5 expressed by a stromal population along the folds could represent a specific mesenchymal subsets involved in the maintenance of the folds tip epithelium. To expand and integrate our previous findings describing the organization and the architecture of the RT stem cell niche, here I performed a detailed qualitative analysis of the distribution of the stromal component of the niche and in particular of telocytes (TC) as active player of the intestinal homeostasis maintenance. To this purpose, specific histological staining for the connective tissue and ultrastructural analysis have been performed. Furthermore, since the mouse is the species in which the mesenchymal component of the niche has been studied most, I selected the typical mouse TC markers (PDGFRα and FOLX1) as target genes, and I verified their topographical localization through fluorescence in situ hybridization. In addition, I studied their spatial distribution in relation with the epithelial components of the stem cell niche. Our results indicated the presence of slender elongated cells, distributed juxtaposed the enterocytes’ basement membrane creating an intricate mesh extending from the folds base to their apex. TEM analysis confirmed the identity of this cell population as TC; indeed, they possessed the distinctive features of this cell type, including a voluminous nucleus and limited cytoplasm from which long thin discontinuous branches develop. Moreover, in the close proximity of telocytes, I observed extracellular vesicles suggesting their functional implication in long distance cell-to-cell communication. In situ localization of pdgfrα transcripts highlighted two distinct pdgfrα+ cell populations, one displaying the typical morphology and position of TC, and another expressing pdgfrα at lower level and not possessing the distinctive TC morphological features and therefore considered as common fibroblasts. In situ localization of foxl1 transcripts revealed that foxl1+ cells were rare and distributed in the peri-epithelial space both at the folds base and along the folds length. In both locations, foxl1 was always co-expressed with pdgfrα, indicating the existence of a small functional telocytes subset. Basal TC were in the proximity of actively cycling intestinal stem cells, suggesting a possible interaction through short-range signaling. Their morphology and distribution at the basal and apical portion of the intestinal folds were identical to those observed in the mouse. This allows us to infer that also in RT, as in mouse, telocytes stimulate either cell proliferation or cell differentiation depending on their topographical location. Altogether, these results substantially improve our understanding of the molecular mechanism and of the cell types involved in the maintenance of intestinal homeostasis. As mentioned above, despite the complexity organization of the RT mucosa, the development of an in vitro tool able to retain similarities with the in vivo counterpart, would be a helpful tool for the rapid screen of several alternatives feeds implied in aquaculture. After several attempts, two novel cells line belonging from proximal (RTpi-MI) and distal (RTdi-MI) intestine of RT were successfully derived and characterized. Therefore, based on the extensive morphological and functional characterization of the RT mucosa in vivo, in this thesis several efforts have been also dedicated to the derivation of new stable cell lines. Then, they have been compared with the only continuous cell line that so far has been established from rainbow trout intestine (RTgutGC). Gene expression analysis demonstrated that all the cell line presented both epithelial and mesenchymal components. However, despite all of them displayed an epithelial component, this was significantly higher in the RTpiMI. Moreover, they also expressed the typical enterocytes’ functional markers (PepT1 and Sglt1) suggesting their suitability as a model of in vitro absorption. Furthermore, all the cell lines preserved both stem cells and differentiating cell types. High seeding density induced their differentiation into more mature phenotypes, as indicated by the simultaneously downregulation of intestinal stem cell-related genes (i.e., sox9, hopx and lgr5) and upregulation of alkaline phosphatase activity. Nevertheless, among the three cell lines most parameters that we analyzed were conserved, some significant differences were observed. Therefore, this suggests that some typical features that characterize the two main intestinal portions are also preserved in vitro. Moreover, since only a mild stimulus was able to induce their differentiation it would be interesting to further explore these mechanisms using more controlled and sophisticated culture systems.
6
Tuohy, K. "Measurement of DNA transfer in the gut using in vitro and in vivo models". Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322465.
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Shah, Pranjul, Joëlle V. Fritz, Enrico Glaab, Mahesh S. Desai, Kacy Greenhalgh, Audrey Frachet, Magdalena Niegowska et al. "A microfluidics-based in vitro model of the gastrointestinal human–microbe interface". NATURE PUBLISHING GROUP, 2016. http://hdl.handle.net/10150/614760.
Abstract (sommario):
Changes in the human gastrointestinal microbiome are associated with several diseases. To infer causality, experiments in representative models are essential, but widely used animal models exhibit limitations. Here we present a modular, microfluidics-based model (HuMiX, human-microbial crosstalk), which allows co-culture of human and microbial cells under conditions representative of the gastrointestinal human-microbe interface. We demonstrate the ability of HuMiX to recapitulate in vivo transcriptional, metabolic and immunological responses in human intestinal epithelial cells following their co-culture with the commensal Lactobacillus rhamnosus GG (LGG) grown under anaerobic conditions. In addition, we show that the co-culture of human epithelial cells with the obligate anaerobe Bacteroides caccae and LGG results in a transcriptional response, which is distinct from that of a co-culture solely comprising LGG. HuMiX facilitates investigations of host-microbe molecular interactions and provides insights into a range of fundamental research questions linking the gastrointestinal microbiome to human health and disease.
8
Vangala, Swathi. "Human Cytochrome P450 3A4 Over-Expressing IEC-18 and MDCK Cell Lines as an In-Vitro Model to Assess Gut Permeability and the Enzyme Metabolism". Scholarly Commons, 2013. https://scholarlycommons.pacific.edu/uop_etds/273.
Abstract (sommario):
Purpose. The fate of an orally administered drug is dependent on many parameters before it can reach the systemic circulation, including drug absorption and first-pass metabolism in the gut and the liver. Mammalian cells lines such as MDCK and Caco-2 are commonly employed to assess drug permeability but they lack or have low expression level of drug metabolism enzyme expression such as CYP3A4, which contributes to significant first-pass gut and liver metabolism for many drugs. Consequently, these cell lines are not sufficient to integrate metabolism when assessing drug absorption. Here, we tested MDCK and IEC-18 cells transiently over-expressing CYP3A4 as models that can simultaneously assay a compound's permeability and metabolism potential in a single experiment. Method. A recombinant adenovirus carrying the hCYP3A4 cDNA was constructed according to Stratagene's AdEasy XL Adenoviral system. This adenovirus was used to transiently transfect hCYP3A4 into MDCK and IEC-18 cells. Western blot was performed to assess the level of hCYP3A4 expression in the wild type and CYP3A4 over-expressing IEC-18 and MDCK cells. In situ metabolism and transport studies were performed with wild-types and IEC-18-3A4 or MDCK-3A4 cells. Results. The amount of CYP3A4 present in MDCK-3A4 cells was 250 times to that of wild type cells which 1/4th the amount present in human liver microsomes. The amount of CYP3A4 present in IEC-18-3A4 cells was 150 times to that of wild type cells which 1/6th the amount present in human liver microsomes. In metabolism studies, there was higher formation of metabolites in cells transfected with hCYP3A4 compared to controls. In addition, apical to basal transport studies of several drugs in IEC-18-3A4 and MDCK-3A4 showed increased appearance of metabolites compared to the wild-type cells. Conclusions. This model may be a useful to assess the extent of drug absorption into systemic circulation after oral administration.
9
Deschamps, Charlotte. "Impact du poids corporel et d'une perturbation antibiotique sur le microbiote intestinal du chien : simulation in vitro et stratégies de restauration". Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2023. http://www.theses.fr/2023UCFA0055.
Abstract (sommario):
Différentes tailles de chiens sont associées à des variations de la physiologie digestive, principalement liées au colon et à ses microorganismes résidents. Ce microbiote intestinal joue un rôle clé en santé, soutenant les processus nutritionnels, immunologiques et physiologiques. Néanmoins, les maladies ou l'antibiothérapie peuvent altérer l'équilibre microbien et induire un état perturbé appelé dysbiose. Pour restaurer l'eubiose du microbiote, de nouvelles stratégies de restauration ont été développées telles que les pré, pro ou postbiotiques. Cependant, peu d'études ont évalué leurs effets sur le microbiote dans le cadre de l'antibiothérapie. Cette thèse entre l'unité Microbiologie, Environnement digestif et Santé de l'Université Clermont Auvergne et les deux sociétés Lallemand Animal Nutrition et Dômes Pharma, visait à étudier l'impact du poids corporel et des antibiotiques sur le microbiote colique canin, ainsi que le potentiel de stratégies de restauration microbienne, à l'aide de modèles intestinaux in vitro.Cette thèse a commencé par évaluer l'impact de différentes méthodes de stockage des échantillons fécaux (congélation 48 h à -80°C, 48 h à -80°C avec du glycérol ou lyophilisation avec maltodextrine/tréhalose) sur la cinétique de colonisation du microbiote et ses activités métaboliques dans Mucosal Artificial Colon (M-ARCOL). Par rapport aux selles fraîches, l'inoculation avec des selles congelées brutes est apparue comme la meilleure option. Grâce à une revue de la littérature, le modèle a été adapté pour reproduire les paramètres nutritionnels, physicochimiques et microbiens spécifiques des conditions du petit, moyen et grand chien dans un nouveau modèle appelé Canine M-ARCOL (CANIM-ARCOL), validé avec des comparaisons in vitro-in vivo. Ceci a permis de reproduire in vitro l'augmentation de la production des principaux acides gras à chaîne courte (AGCC), et la prolifération des Bacteroidota et Firmicutes observées in vivo. Puis, le modèle a permis de réaliser une étude mécanistique, révélant que les paramètres nutritionnels et physicochimiques façonnent l'activité du microbiote associé à la taille du chien, mais que l'inoculum fécal est nécessaire pour reproduire sa composition. Enfin, notre modèle a été adapté pour reproduire la dysbiose induite par les antibiotiques. Conformément aux données in vivo, l'antibiothérapie a induit la prolifération des Enterobacteriaceae, Streptococcaceae et Lactobacillaceae, tandis que la diversité et la production d'AGCC diminuaient. Des effets similaires mais moindres ont été observés dans le microbiote mucosal. Enfin, nous avons évalué l'effet de Saccharomyces boulardii CNCM I-1079 et de Lactobacillus helveticus HA-122 tyndallisée sur la résistance du microbiote pendant le traitement antibiotique et la résilience après celui-ci. Les deux stratégies ont réduit la prolifération des Enterobacteriaceae pendant l'antibiothérapie et permis au cours des deux premiers jours, une résilience plus rapide de la composition et l'activité du microbiote, dans le lumen et le mucus.Ce travail a fourni des informations pionnières et significatives sur l'impact de la taille du chien et de l'antibiothérapie sur la composition et l'activité du microbiote luminal et mucosal du colon canin, comblant les lacunes dans ces domaines. Ces travaux améliorent la compréhension de la résilience du microbiote en réponse aux perturbations antibiotiques. Dans un futur proche, en accord avec les règles européennes 3R visant à réduire les expérimentations animales, nos approches in vitro pourraient être utilisées pour des études mécanistiques des interactions entre nutriments, additifs alimentaires ou produits vétérinaires et microbiote. De telles expériences pourraient être réalisées en situations saines ou perturbées (obésité, maladies inflammatoires de l'intestin ou entéropathies chroniques), en tenant compte des variabilités interindividuelles pour progresser vers une nutrition et une médecine personnaliséesDifferent dog sizes are associated with variations in digestive physiology, mainly related to the large intestine and its resident microorganisms. This gut microbiota plays a key role in animal health, supporting nutritional, immunological and physiological processes. Nevertheless, diseases or antibiotherapy can disturb microbial equilibrium and induce a perturbated state called dysbiosis. To restore microbiota eubiosis, new restorations strategies have been developed such as pre-, pro- or postbiotics. However, very few studies have evaluated their effects on gut microbiota in the context of antibiotherapy. This joint PhD between the Microbiology, Digestive Environment and Health unit from Université Clermont Auvergne and the two compagnies Lallemand Animal Nutrition and Dômes Pharma, aimed to investigate the impact of body weight and antibiotic disturbance on canine colonic microbiota, as well as the potential of microbial restoration strategies, using in vitro gut models.This thesis started by evaluating the impact of different methods for faecal sample storage (48-h freezing -80°C, 48-h -80°C with glycerol or lyophilization with maltodextrin/trehalose) on the kinetics of microbiota colonization and metabolic activities in the Mucosal Artificial Colon (M-ARCOL). Compared to fresh stools, inoculating with raw frozen stool without cryoprotectant was the best option among those tested. Second, thanks to a large literature review, the M-ARCOL model was adapted to reproduce the main nutritional, physicochemical and microbial parameters specific from small, medium and large size conditions in a new model called Canine M-ARCOL (CANIM-ARCOL), further validated through in vitro-in vivo comparisons. This adaptation allowed to reproduce in vitro the increase in Bacteroidota and Firmicutes abundances and higher main short-chain fatty acid (SCFA) concentrations observed in vivo. Then, we used the CANIM-ARCOL to perform a mechanistic study, which revealed that nutritional and physicochemical parameters are enough to shape microbiota activity according to dog size, but faecal inoculum was necessary to reproduce size-related microbiota composition. The next step was to adapt the CANIM-ARCOL to diseased situation, focusing on antibiotic-induced dysbiosis. In accordance with in vivo data, antibiotherapy induced an increase in Enterobacteriaceae, Streptococcaceae and Lactobacillaceae relative abundances while alpha-diversity and SCFA production decreased. Similar but lower effects were observed in mucus-associated microbiota. Lastly, we evaluated the effect of the live probiotic yeast Saccharomyces boulardii CNCM I-1079 and the heat-inactivated bacteria Lactobacillus helveticus HA-122 on microbiota resistance during antibiotic treatment and resilience afterwards. Of interest, both microbial strategies decreased the Enterobacteriaceae bloom during antibiotherapy and allowed, in the first two days, a quicker recovery of microbiota composition and activity, in both the luminal and mucosal compartments.This PhD work provided pioneering and significant insights into the impact of dog size and antibiotherapy on canine colonic luminal and mucus-associated microbiota composition and activity, filling gaps in knowledge in these fields. This work also contributed to a better understanding of microbiota resilience in response to antibiotic disturbance. In a near future, in accordance with the European 3R's rules aiming to reduce at a maximum animal experiments, our in vitro approaches could be used for mechanistic studies on the interactions between nutrients, feed additives or veterinary products and canine colonic microbiota. Such experiments could be performed under healthy but also disturbed gut microbial situations (including obesity, inflammatory bowel diseases or chronic enteropathies), always considering interindividual variabilities to move towards personalized nutrition and medicine
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MANCINO, ROBERTA. "Influence of cow diet on nutritional profile of milk and dairy products and effects on alterations of human gut microbiota by an in vitro digestion model". Doctoral thesis, Università di Foggia, 2018. http://hdl.handle.net/11369/363264.
Abstract (sommario):
I consumatori richiedono costantemente la presenza sul mercato di alimenti salutistici, che in termini di latte e prodotti lattiero-caseari si traducono in un latte con percentuali più elevate di acidi grassi “sani” come gli acidi grassi polinsaturi (PUFA), ed una più bassa percentuale di acidi grassi saturi (SFA). Il latte e prodotti lattiero-caseari contribuiscono in modo significativo all’assorbimento di sostanze nutritive essenziali nella dieta. Nonostante ciò, il consumo di latte ha fatto registrare un’inflessione a causa delle linee guida nutrizionali che suggeriscono di limitare il consumo pro capite di SFA, che per una parte significativa provengono da latte e derivati (USDA e HHS, 2010). Una strategia per migliorare il profilo di FA di latte e prodotti lattiero-caseari è l'integrazione della dieta bovina con semi oleaginosi, che diminuiscono la percentuale di SFA nel latte, diminuendo la sintesi de novo di FA nella ghiandola mammaria. Da precedenti sperimentazioni emerge che la supplementazione di semi di lino nella dieta delle bovine da latte riduce le concentrazioni di acidi grassi a corta catena corta e acidi grassi a media catena, ed aumenta il contenuto di acidi grassi a lunga catena nel grasso del latte. Tuttavia, l’inclusione dei semi oleaginosi, in particolare dei semi di lino, nella dieta della vacca da latte, scoraggia gli allevatori dal loro utilizzo, a causa del costo molto elevato. É necessario, quindi, trovare un compromesso tra costi aggiuntivi stimati e la giusta quantità di semi oleaginosi da somministrare nella dieta degli animali per migliorare la produzione di latte e la sua composizione. In Italia, circa l'80% delle aziende lattiero-casearie utilizza vacche di razza Frisona per la produzione lattea da destinare sia al consumo diretto che alla produzione di formaggio. Le bovine di razza Jersey vengono utilizzate per migliorare l'efficienza del settore della produzione di formaggio in diverse parti del mondo. Il tratto gastrointestinale costituisce la più grande interfaccia del corpo con l'ambiente esterno ed è esposto ad una grande quantità di materiale estraneo, inclusi batteri patogeni e commensali, così come antigeni alimentari. La tolleranza orale è una proprietà importante del sistema immunitario intestinale; l’omeostasi intestinale richiede interazioni equilibrate tra il microbiota intestinale e gli antigeni alimentari. Alla nascita, siamo colonizzati da una complessa comunità di cellule mcrobiche che arriva fino a una densità di 1 × 1012 cellule batteriche per grammo di microbi contenuti nel colon adulto. Queste cellule microbiche vivono in una relazione simbiotica con l'ospite e sono determinanti in materia di salute e di malattia, influenzando l'assorbimento dei nutrienti, la funzione di barriera e lo sviluppo del sistema immunitario. Sulla base delle considerazioni precedenti gli scopi del presente lavoro di tesi sono: 1. cercare di ridurre la quantità giornaliera di semi di lino somministrati agli animali per incoraggiare il loro utilizzo da parte degli allevatori per aumentare il contenuto di acidi grassi polinsaturi nel latte a scapito degli acidi grassi saturi con una connotazione salutistica del latte prodotto; 2. testare gli effetti della somministrazione di semi di lino su due diverse razze da latte: Frisona e Jersey; 3. valutare il trasferimento di acidi grassi polinsaturi in due diversi prodotti lattiero-caseari (Caciotta vs Caciocavallo) con tempi di stagionatura diversi; 4. valutare gli effetti dei prodotti lattiero-caseari naturalmente arricchiti in acidi grassi polinsaturi sulla salute umana di un modello di digestione in vitro con la valutazione di: a) variazioni di profilo degli acidi grassi di prodotti lattiero-caseari dopo la digestione in vitro; b) acidi grassi a catena corta (SCFA) prodotti dal gut microbiota; c) variazioni della flora intestinale tramite fermentazione fecale seguito da pirosequenziamento. Dai risultati ottenuti il contenuto elevato di latte C18:3n3 nel latte suggerisce che la riduzione della quantità di supplementazione di semi di lino nella dieta delle bovine può migliorare latte profilo di acidi grassi con una consistente riduzione dei costi di produzione; le razze sottoposet alla sperimentazione, Frisona e Jersey hanno risposto in modo diverso alla stessa supplementazione di semi di lino. Gli acidi grassi polinsaturi sono stati trasferiti nei prodotti lattiero caseari, soprattutto nella Caciotta, suggerendo un ruolo determinante del protocollo di caseificazione nel trasferimento della tipologia di acido grasso della dieta. Dopo la digestione in vitro, gli acidi grassi rimangono nel digerito gastro-intestinale; la loro presenza può avere effetti benefici sul tratto gastrointestinale e di conseguenza sulla salute umana. Inoltre la presenza e la quantità di acidi grassi a catena corta (SCFA) ritrovata nei fermentati fecali suggeriscono alcuni cambiamenti delle popolazioni microbiche indotte dalla presenza dei prodotti lattiero caseari sperimentali, lasciando intravedere importanti effetti benefici sulla salute umana.Health-conscious consumers are demanding milk with higher proportions of healthy fatty acids as polyunsatured fatty acids (PUFA), and lower proportion of saturated fatty acids (SFA). Milk and dairy products contribute significantly to the consumption of essential nutrients in human populations. Despite its important roles in human nutrition, consumption of milk has declined, because nutritional guidelines have limited capita consumption of SFA, which to a significant proportion originate from milk and dairy products (USDA and HHS, 2010). A strategy to improve the FA profile of milk and dairy products is the supplementation of cow’s diet with oilseeds, which decrease the proportion of SFA, by decreasing de novo FA synthesis in the mammary gland. Feeding flaxseed to dairy cows decreases the concentrations of short-chain fatty acids and medium chain fatty acids and increases the long-chain fatty acid content in milk fat. However, oilseeds, and in particular flaxseed, have a very high costs that discourage farmers in their utilization. It’s necessary, therefore to find a compromise between costs and the right amount to be administered in the diet to the animals to ameliorate milk yield and composition. In Italy, about 80% of dairy farms produce milk of Friesian cows both for direct consumption and for cheese production. Jersey breed and it has been used to improve the efficiency of the cheesemaking sector in different part of the world, and is characterized by improved longevity, superior udder health, higher cheese yield, reduced feed and water requirement. The gastrointestinal tract constitutes the body’s largest interface with the external environment and is exposed to a vast amount of foreign material, including pathogenic and commensal bacteria, as well as food antigens. Oral tolerance is an important property of the gut immune system; intestinal homeostasis requires balanced interactions between the gut microbiota, dietary antigens. At birth, we are colonized with a complex community of microbes that reaches up to a density of 1 × 1012 bacterial cells per grams of content in the adult colon. These microbes live in a symbiotic relationship with the host and they are determinants in health and disease influencing nutrient absorption, barrier function and immune development. On the basis of the previous considerations and considering that oil seeds are expensive and many farmers are reluctant to use them the aims of this PhD thesis are: 1. trying to reduce the daily amount of flaxseed administered to animals in order to increase the content of polyunsaturated fatty acids in milk at the expense of saturated fatty acids, and to encourage its utilization by farmers as supplements to dairy cows with a reduction of management costs; 2. testing the effects of flaxseed administration on two different dairy cows breeds: Friesian and Jersey; 3. evaluating the transferring of polyunsaturated fatty acids in two different dairy products (Caciotta vs Caciocavallo) at different ripening time; 4. evaluating the effects of dairy products naturally enriched in polyunsaturated fatty acids on human health by an in vitro digestion model with the evaluation of changes in: a) fatty acid profile of dairy products after in vitro digestion; b) short chain fatty acids (SCFA) produced by gut microbiota; c) changes in gut microbiota populations by fecal fermentation followed by pyrosequencing. The higher milk content of C18:3n3 in milk suggests that the reduction in the amount of flaxseed supplementation can also improve milk fatty acid profile with a consistent reduction of production costs; however, Friesian and Jersey cows replied differently to the same flaxseed supplementation; Polyunsatured fatty acids are transferred into dairy products, especially in Caciotta cheese, suggesting that probably the different cheese making influenced the transferring. After in vitro digestion, fatty acids remain in the digest; their presence can have beneficial effects on the gastrointestinal tract and consequently on human health. Moreover the presence and the amount of short chain fatty acids (SCFA) could suggest some changes of microbiological populations that could have beneficial effects on human health.
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Cordonnier, Charlotte. "Survie et pathogénicité des EHEC dans l'environnement digestif : Interactions avec le microbiote et l'épithélium intestinal. : Influence de l'administration de levures probiotiques". Thesis, Clermont-Ferrand 1, 2015. http://www.theses.fr/2015CLF1MM21/document.
Abstract (sommario):
Les Escherichia coli entérohémorragiques (EHEC) sont des pathogènes majeurs pour l’homme responsables de toxi-infections alimentaires pouvant évoluer vers des complications potentiellement mortelles. La pathogénicité de ces souches est essentiellement due à la production de Shiga-toxines (Stx), même si d’autres facteurs semblent jouer un rôle important dans la virulence, comme des facteurs d’adhésion. La survie et la régulation des facteurs de virulence des EHEC dans l’environnement digestif humain sont des facteurs clés dans la pathogénicité bactérienne, mais restent à ce jour mal décrits, essentiellement en raison d’un manque de modèles d’étude adaptés. De plus, l’absence de traitement spécifique a conduit à s’intéresser à des moyens préventifs et/ou curatifs alternatifs, comme l’utilisation de probiotiques. L’objectif de ce travail de thèse est (i) de mieux comprendre le comportement de la souche de référence EHEC O157:H7 EDL933 dans l’environnement digestif humain simulé, et en particulier ses interactions avec le microbiote résident et l’épithélium intestinal, et (ii) d’évaluer l’effet antagoniste d’une souche de levure probiotique vis-à-vis de la survie, la virulence et l’interaction du pathogène avec l’épithélium intestinal, à l’aide d’approches in vitro et in vivo complémentaires. En modèles digestifs in vitro, la souche EHEC survit dans l’estomac, voire se multiplie dans les parties distales de l’intestin grêle, alors qu’elle ne se maintient pas dans l’environnement colique. Les gènes de virulence codant les Stx et des adhésines majeurs (intimine et « Long Polar Fimbriae » ou Lpf) sont surexprimés dès les parties hautes du tractus digestifs, et ce, même en absence de cellules épithéliales. Les conditions rencontrées dans le tractus digestif supérieur de l’enfant, comparativement à celui de l’adulte, conduisent à une survie et un niveau d’expression des gènes codant les Stx et les Lpf plus élevés chez l’enfant, ce qui peut contribuer à expliquer la grande sensibilité de cette population aux infections à EHEC. Enfin, les Lpf semblent jouent un rôle clé dans le ciblage spécifique des cellules M et le tropisme des EHEC pour les plaques de Peyer, et ce, à la fois in vitro (cellules M en culture) et in vivo (anses iléales murines). Même si elle ne modifie pas la survie du pathogène dans l’environnement colique, la levure probiotique S. cerevisiae CNCM I-3856 a montré des propriétés antagonistes intéressantes vis-à-vis d’EHEC O157:H7 en (i) modulant favorablement l’activité fermentaire du microbiote intestinal, (ii) diminuant significativement l’expression des gènes codant les Stx et (iii) inhibant la translocation bactérienne au travers des plaques de Peyer et les lésions hémorragiques associées. Par ailleurs, l’effet du pathogène et des probiotiques sur le microbiote colique est individu dépendant, confortant l’hypothèse que des facteurs associés à l’hôte, comme le microbiote, pourraient conditionner l’évolution clinique des infections à EHEC et l’efficacité d’une stratégie probiotique.Ce travail de thèse contribue à une meilleure compréhension du comportement des EHEC dans l’environnement digestif humain et confirme l’intérêt d’une stratégie probiotique dans la lutte contre le pathogène. Une étude plus approfondie du transcriptome du pathogène dans l’environnement digestif et une analyse par des méthodes haut débit du microbiote intestinal permettraient de continuer à mieux décrire la physiopathologie des infections à EHEC et comprendre les mécanismes associés à l’effet antagoniste des probiotiquesThe enterohemorrhagic Escherichia coli (EHEC) are major zoonotic pathogens responsible for food-borne infectionwhich leads to life-threatening complications in humans. The main virulence determinant of EHEC is the production of Shigatoxins (Stx), even if other factors seem to play an important role in virulence, such as adhesion factors. Survival and virulenceof EHEC strains in the human digestive environment are a key factor in bacterial pathogenesis but remains unclear owing tolack of relevant model. Moreover, no specific treatment has led to interest in preventative and / or curative alternatives, suchas using probiotics. The objective of this study is to better understand the behavior of the reference strain EHEC O157:H7EDL933 in the entire digestive tract, and in particular its interaction with the resident microbiota and the intestinal epithelium,and to evaluate the antagonistic effect of the probiotic yeast, Saccharomyces cerevisiae CNCM I-3856, using in vitro and in vivo complementary approaches.In vitro, bacterial mortality was noticed in the stomach, whereas bacterial growth resumption was observed in thedistal parts of the small intestine and the pathogen was not able to maintain in the human colonic conditions. Virulence genesencoding Stx and adhesins (intimin and “Long polar fimbriae”) are upregulated in the upper parts of the digestive tract. A ten-time higher amount of cells was found in the ileal effluents of infant compared to adult. stx genes were over-expressed (up to25-fold) in infant conditions compared to the adult ones. This results show that differences in digestive physicochemicalparameters of the upper gastrointestinal tract may partially explain why infants are more susceptible to EHEC infection thanadults. And finally, Lpf seem to play a key role in the interactions of EHEC with murine Peyer’s patches and are needed for anactive translocation of the pathogen across M cells, and both in vitro (M cells culture) and in vivo (murine ileal loops).S. cerevisiae had not effect on EHEC survival in the colonic environment but (i) favorably influenced gut microbiotaactivity through beneficial modulation of short chain fatty acid production, (ii) leading to significantly decrease stx expressionand (iii) significantly reduced EHEC translocation through M cells and inhibited in vivo interactions of the pathogen withPeyer’s patches and the associated hemorrhagic lesions. Probiotic had donor-dependent effect on the gut microbiota strengthenthe hypothesis that host-associated factors such as microbiota could influence the clinical evolution of EHEC infection and theeffectiveness of a probiotic strategy.This work contributes to a better understanding of the behavior of EHEC in the human digestive environment andconfirms the interest of probiotic strategy in controlling EHEC infections. Further transcriptome studies are warranted for thepathogen in the human digestive environment, with or without probiotics for the better understanding of the pathophysiologyof EHEC and so on the mechanisms involved in the antagonistic effect of probiotics
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Müller, Jakob Verfasser], Heinrich H. D. [Akademischer Betreuer] [Meyer, Michael W. [Akademischer Betreuer] Pfaffl e Andrea K. [Akademischer Betreuer] Büttner. "Secondary plant metabolites and gut health: functional studies on porcine small intestine in vitro models / Jakob Müller. Gutachter: Michael W. Pfaffl ; Andrea K. Büttner. Betreuer: Heinrich H. D. Meyer". München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1030099545/34.
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Li, Yingchuan. "A SUSY SO(10) GUT model with lopsided structure". College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6703.
Abstract (sommario):
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Kuwahara, M., T. Ogaeri, R. Matsuura, H. Kogo, T. Fujimoto, S. Torihashi e 茂子 鳥橋. "In vitro organogenesis of gut-like structures from mouse embryonic stem cells". Blackwell, 2004. http://hdl.handle.net/2237/7446.
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Jaiyeola, Etana Joy. "Gut microbiota in human type 2 diabetes : in-vivo and in-vitro studies". Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/844975/.
Abstract (sommario):
The gut microbiota plays an important role in the development of type 2 diabetes (T2D), which is an alteration in the diversity and abundance of the gut microbiota, favouring the growth of Gram-negative bacteria. Although a lot of studies have shown this to be the case, most of this work has been done in animal models with few studies in humans. In animal models of T2D, it is known that a high-fat diet alters the gut microbiota in favour of the growth of Gram–negative bacteria. The outer membrane of Gram-negative bacteria contains lipopolysaccharide (LPS) which is an endotoxin that can trigger inflammation leading to metabolic disorders such insulin resistance and T2D, hence T2D is considered a low grade inflammatory disorder. In this thesis, the effect of Galactooligosaccharide (GOS), a prebiotic, on the composition of the gut microbiota was investigated. Next generation sequencing (NGS) of the gut microbiota of T2D and healthy control subjects showed no significant difference at the phylum level between the two groups. Furthermore, T2D patients in the prebiotic group had a significant increase in the level of Firmicutes compared to the placebo group. Also, although not significant, T2D patients on metformin had increased level of Bacteroidetes, Proteobacteria and Actinobacteria compared to those not on metformin. The ability of human faecal water (FW) to distinguish between healthy and T2D patients using an in vitro model of the intestinal mucosa was studied. FW from T2D patients decreased Caco-2 cell monolayer integrity when compared to the healthy controls and in the T2D patients, FW activity in vitro correlated with biological markers of T2D severity measured in vivo. Additionally, cytokines were measured in T2D faecal samples using a human cytokine array. Finally, GOS anti-cytotoxic activity was also assessed in vitro using cell viability assays and the anti-cytotoxic effect of GOS was time and concentration dependent. Together, the thesis explored potential new ways of using faecal samples as biomarker for T2D in vitro and relating it to in vivo parameters of the patients. Also future work in this area may reveal mechanistic insight to the use of FW as a non-invasive biomarker for T2D.
16
Agans, Richard Thomas. "Modeling Effects of Diet on Human Gut Microbiota". Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1472128769.
17
Jiang, Lei. "On human gut microbial ecosystem : in vitro experiment, in vivo study and mathematical modelling". Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa42214.
Abstract (sommario):
The human gut microbiota is considered to be a highly specialized organ providing nourishment, regulating epithelial cell development, modulating innate immune responses and colonization resistances, and it significantly impacts human health and disease. Dispite of being extensively studied for several decades, the functionality of the microbiota colonization in the human gastrointestinal tract and the mechanisms of the interactions between the host and bacteria are still poorly understood. This research follows a novel and unique approach, which combines the complementary strengths of in vitro experiment, in vivo study and mathematical modelling. The work undertaken has three emphases: 1) probiotic strains and their impact on human health; 2) the development of gut microbiota in infants; 3) quantification of human gut microbial ecosystem at both the species level and the system level. In the first part of this research, a versatile anaerobic continuous culture platform was implemented following a novel and unique design, which allows easy and continuous sampling and monitoring of microbial growth. A number of carefully planned in vitro experiments have been conducted to investigate the growth and competition of probiotic strains under different culture conditions. These in vitro experiments improve the understanding for the growth behaviour of the specific probiotic strains. The second part of this project analyzed 50 faecal samples collected from 9 healthy infants with administration of probiotic strains and placebo. The analysis is based on the 454-pyrosequencing technology, which reveals the complete profiles of gut microbiota in these infants and confirmed the modulation effect of the specific probiotic strains. The last part of this research focused on the development of mathematical and computational models of human gut microbial ecosystem. The outcome from this part of the research includes: a) a new bacterial growth model that overcomes the parodox of competitative exclusion caused by previous models; b) a versatile computational framework to simulate in vitro fermentation experiments; and c) a comprehensive mathematical model for human gut and gut microbiota that is the first model for its nature.
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Nistor, Nicolae, e Monika Schustek. "Wie gut sind die guten alten FAQs?" Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-76312.
Abstract (sommario):
Die zunehmende Nutzung der digitalen Medien im Rahmen des universitären Bildungsmanagements ist mit neuen Arbeitsweisen verknüpft. Dafür brauchen Hochschulmitarbeiter, Doktoranden und Studierende vielfältige Kompetenzen, die technisches Wissen und Können einschließen und im formellen Rahmen nicht vollständig abgedeckt werden können. Als Alternative zur Unterstützung durch spezialisierte Einrichtungen (wie z.B. IT-Helpdesks) bietet sich die gemeinsame Wissenskonstruktion und -kommunikation in der akademischen Wissensgemeinschaft an. Dabei stellt sich allerdings die Frage, inwieweit und unter welchen Bedingungen die mediengestützten, kulturellen Artefakte wie FAQ-Sammlungen, die diese Lernprozesse unterstützen können, von den Akteuren akzeptiert werden. Die vorliegende Arbeit stellt zunächst einen theoretischen Hintergrund der Wissenskommunikation in Wissensgemeinschaften vor. Dieser umfasst zum einen den Community of Practice-Ansatz (Lave & Wenger, 1991) und zum anderen die Unified Theory of Acceptance and Use of Technology (Venkatesh, Morris, Davis & Davis, 2003). Daraus wird ein Forschungsmodell abgeleitet, das die Zusammenhänge zwischen der Akzeptanz von mediengestützten kulturellen Artefakten, der Partizipation in der Wissensgemeinschaft und der Bereitschaft zur Wissenskommunikation erklärt. Anschließend wird das Modell durch eine empirische Studie überprüft. Auf theoretischer Ebene trägt die Studie zur Annäherung der Medienakzeptanztheorien an die Perspektive des situierten Lernens bei. Als medienpädagogische Konsequenz bietet das Modell Ansatzpunkte zur Förderung der Wissenskommunikation in akademischen Wissensgemeinschaften.
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Hand, K. V. "Studies investigating in vitro nutrient stimulated secretion of gut satiety signals and potential mechanisms of release". Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546355.
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FIORE, WALTER. "OVERALL ASSESSMENT OF A MODEL PROBIOTIC BACTERIUM: FROM GUT COLONIZATION TO CLINICAL EFFICACY". Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/737193.
Abstract (sommario):
Probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”. This definition is inclusive of a broad range of microbes and applications, whilst capturing the essence of probiotics (microbial, viable and beneficial to health). Specific guidelines describe the minimal requirement for the probiotic status. In particolar, the conventional process of selecting novel potential probiotic strains includes the assessment of: 1) the ability of the strains to survive during the gastrointestinal transit and reach alive the intestine, 2) the actual impact of the probiotic bacterium on the intestinal microbial ecosystem (IME).
To evaluate these two aspects, in my PhD project we first carried out two recovery studies (in children and adults) with a selected probiotic bacterial strain, named Lactobacillus paracasei DG. Then, to evaluate the impact of the strain DG on IME we partecipated in a multicenter, randomized, double-blind, cross-over, placebo-controlled, pilot trial in irritable bowel syndrome (IBS) and determined the overall structure of the intestinal microbial communities by 16S rRNA gene profiling.
Specifically, to demonstrate the capability of the selected bacterial strain to survive the gastrointestinal transit when consumed by healthy subjects, we developed and adopted in the recovery studies a strategy that combined culture-based methods and molecular methods for strain specific enumeration of viable cells in fecal samples. The results showed that the L. paracasei DG was re-isolated from at least one fecal sample of all the volunteers, survived the gastrointestinal transit and proliferated in the intestine, and persisted after the interruption of the probiotic intake up to 5 days in adults and 3 days in children.
The results of the pilot study in IBS showed that Lactobacillus paracasei DG is able to modulate gut microbiota structure/function and reduce immune activation in IBS. Specifically, the strain induced a significant reduction in genus Ruminococcus, a significant increase in the short chain fatty acids (SCFAs) acetate and butyrate, and a significant reduction in the pro-inflammatory cytokine interleukin-15.
Finally, we also investigated on mice the site of colonization of the probiotic bacterium in the intestine (animal study). The obtained results demostrated that L. paracasei DG colonized preferentially caecum and colon compared to ileum, suggesting a specific use of this probiotic in case of pathological situations with a localization at colonic level, such as diverticular disease and IBD, which are conditions including dysbiosis in their etiopathogenesis.
At the end of my PhD, we focused on another very important point in the probiotic world, i.e. the “neglected” bacterial components of commercial probiotic formulations. In fact, it is quite clear that not only live, but also dead cells are present in probiotic products and they can generate beneficial biological responses. This can have several implications for the production and application of probiotics, influencing the potential health promoting effects since the relative proportions of live and dead cells in a probiotic formulation is usually unkwnon. This aspect can be very important, even while conducting clinical trials aiming at studying the efficacy of a probiotic product.
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Joesten, William C. "Exploring the relationships between gut bacteria, gut permeability, and bacterial metabolism in the Non Obese Diabetic (NOD) mouse model of Type 1 Diabetes (T1D)". Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1574423689823958.
22
Wang, Xuedan. "Effect of inulin type fructans on protein fermentation by gut bacteria : in vitro and in vivo studies". Thesis, University of Reading, 2018. http://centaur.reading.ac.uk/79980/.
Abstract (sommario):
In Europe and Northern America, protein intake is high, whilst fibre intake is relatively low. With large amounts of protein entering the colon, bacterial proteolysis may have some negative effects through potentially toxic end-products. Prebiotics could have the potential to reverse negative consequences of gut bacterial protein fermentation. Single stage, pH controlled, anaerobic, stirred batch culture systems simulating the distal colon were applied first with faecal inoculum from both omnivore and vegetarian volunteers. Fermentation of different protein sources with and without supplementation of inulin type fructans (ITF) were tested. A significant increase of bifidobacteria was observed with the addition of the ITF together with lower concentrations of protein fermentation metabolites (BCFA and ammonia). Three-stage continuous colonic model systems simulating the whole colon were then studied with both omnivore and vegetarian volunteers. Casein, with and without two different doses of ITF were assessed. A significantly higher number of bifidobacteria and reduction of bacteroides and Desulfovibrio spp. were found with ITF addition. Furthermore, production of metabolites from protein fermentation (BCFA and ammonia) was significantly lowered with ITF. To confirm the health benefit of ITF on high protein population in vivo, 43 volunteers were recruited to complete a randomised, double blind, cross over trial. A significant increase in bifidobacteria and a decrease in Desulfovibrio spp. was confirmed with the addition of prebiotic treatment. Stool frequency was significantly higher with ITF as compared to the placebo group, with a trend towards softness as based on the Bristol scale. Total bacteria and bifidobacteria changes during interventions were significantly correlated with stool frequency. In conclusion, all three phases of the project found favourable bacterial and metabolic changes with ITF supplementation. ITF had inhibitory effects on colonic microbial proteolysis, and could exert health benefit for high protein consumers, especially those who also consume low fibre diet.
23
Poh, Zijie. "Model Building in the LHC Era: Vector-like Leptons and SUSY GUTs". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1502809360161742.
24
Kelsall, Ashlie Peta. "Studies on optimising the everted gut sac model (EGSM) in rat and possum tissue to compare selective drug movement across the intestinal wall". Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14578.
Abstract (sommario):
The in-vitro everted gut sac model has been used extensively in the laboratory environment to investigate the transfer of orally administered drugs across the intestinal wall of rodents. This model involves excision of fresh tissue from the small intestine, which is then everted and sectioned into individual sacs and incubated under mammalian physiological conditions in medium containing the target drug. One of the limitations of this model is the need to access tissue immediately following euthanasia, greatly restricting applicability for many species. This study investigated the movement of a number of drugs across the intestinal wall in rat tissue that had been stored at 4 ºC and then utilised for studies within 60 minutes and after being stored at 24 h; as well as possum tissue that had been stored for approximately 24 h. Transfer of the target drugs fluconazole, digoxin and chloramphenicol were significantly greater in the proximal quarter of the small intestine than the distal three, and so this quarter was used for remaining experiments. A number of segments could be gained from the length of intestine from this quarter and there was no significant difference shown in transfer between any segments. The transfer rate of drugs appeared to decrease following the initial 20 minutes of incubation, and so this initial 20 minutes was investigated in the remaining experiments with rat tissue. Digoxin, a recognised P-glycoprotein substrate, demonstrated the anticipated lower transfer across the intestinal wall of the rat compared to fluconazole and chloramphenicol. Whilst the addition of 5 μg/mL verapamil increased the initial transfer of digoxin across the gut wall, the addition of 25 μg/mL verapamil resulted in significantly lower absorption of all three target drugs following 20 minutes incubation. The transfer of glucose following tissue storage for 0.5 hours was slightly significantly lower than the transfer of glucose observed in tissue stored for 24 h. The transfer of glucose across the gut wall using possum tissue was investigated at 30, 60 and 90 minutes incubation, however access to fresh tissue was problematic, and the possum EGSM did not demonstrate the anticipated transfer curve. The use of lactate dehydrogenase was examined for use as an indicator of cell toxicity, but found to be unreliable. This study concluded that whilst this model may not have future use in wildlife studies that are performed ex-situ, sufficient correlations were seen in these experiments to suggest further studies to validate the EGSM using stored tissue would be warranted.
25
Chohan, M. B. N. "The impact of digestion and gut bioavailability, in vitro, on the polyphenolic associated activity of cooked culinary herbs". Thesis, Kingston University, 2011. http://eprints.kingston.ac.uk/22530/.
Abstract (sommario):
Culinary herbs, the use of which has increased significantly in the last decade, are known to possess health promoting properties, which are attributed mainly to their polyphenols. However, despite the fact that such herbs undergo some form of cooking prior to consumption, there is a paucity of data concerning the effects of cooking on their properties. Furthermore, little is known of the disposition of these polyphenols following digestion and absorption, and thus it is not known whether these herbs have the potential to be significant contributors of dietary polyphenols at amounts used domestically. Thus the aim of this study was to investigate: the impact of cooking processes on the polyphenolic antioxidant activity (AA) of parsley, rosemary, sage and thyme; the impact of digestion in vitro on the AA of the herbs post cooking; the role of the gut on the AA of these herbs using the Caco-2 model of intestinal transport; and whether the AA of these herbs, contributes to their anti-inflammatory and antimicrobial activities. Results showed that cooking significantly increased the AA of these herbs. AA was further enhanced following in vitro digestion with rosmarinic acid identified as the predominant polyphenol. Polyphenolic activity was detected post absorption in vitro but, possibly due to the dilute nature of the samples used, individual polyphenols were not identified. Anti-inflammatory activity of the herbs investigated was significantly associated with their AA. However, there was no association between AA and the anti-microbial activity of aqueous extracts of herbs. Some oil extracts possessed anti-microbial activity, which was enhanced by cooking. In conclusion, this study suggests that the culinary herbs investigated have the potential to contribute to dietary polyphenol intake and thus their health promoting properties. However, the biological significance of this contribution in vivo is yet to be established.
26
Holt, Marie Kragelund Bachmann. "In vitro and in vivo properties of GLP-1 producing neurons : the brain actions of a gut hormone". Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10039312/.
Abstract (sommario):
Glucagon-like peptide-1 (GLP-1) is an incretin and neuropeptide primarily known for its role in glucose homeostasis. GLP-1 also has potent anti-obesogenic potential, and is known to inhibit food intake, food reward, and diet-induced obesity. In addition, brain GLP-1 increases heart rate and mediates effects of acute stress. Within the brain, GLP-1 is produced by preproglucagon (PPG) neurons in the caudal brainstem. Although the potential role of GLP-1 has been studied through pharmacological activation of brain GLP-1 receptors, little is known about the cellular properties and physiological role(s) of PPG neurons. In this thesis, a complementary array of in vitro and in vivo techniques was used to study the physiological roles of PPG neurons. In vitro Ca2+ imaging revealed that PPG neuron activity is modulated by a range of compounds relaying signals of energy balance, satiety, and visceral illness. In vivo, I selectively manipulated PPG neurons in mice using chemogenetic tools. Activation of PPG neurons dramatically reduced feeding, supporting a role for brain-derived GLP-1 in appetite control. Although selective inactivation of PPG neurons had no effect on ad libitum feeding, large meal- or stress-induced reductions in food intake were abolished when PPG neurons were silenced. In freely-behaving mice, systemic GLP-1 receptor activation had no effect on arterial blood pressure, but increased heart rate via stimulation of the sympathetic nervous system. Although permanent ablation of PPG neurons had no effect on heart rate and blood pressure, selective activation of PPG neurons using chemogenetic tools increased heart rate. These results provide the first evidence of the physiological role played by the GLP-1 producing neurons in the caudal brainstem. Activity of these neurons is modulated by diverse neural and humoral signals. They are critically important in the prevention of overeating as well as stress-induced hypophagia and may contribute to central nervous mechanisms of cardiovascular control.
27
Chase, Teena D. "An in vitro model of reactive astrogliosis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ49329.pdf.
28
Worrall, Lisa Kirsty. "A 3D in vitro breast cancer model". Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436812.
29
Mistry, Rupal. "Host-gut microbiota interaction in health and disease using Drosophila melanogaster as a model organism". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:c5add9af-9abf-4664-8c62-4b462c35e2c2.
Abstract (sommario):
The resident gut bacteria of the gastrointestinal tract (gut microbiota) have been known to influence the immune system. Yet the role of the immune system in shaping the gut microbiota composition across an organism's lifespan remains unclear. Previous work in mice has been conflicting and thus remains inconclusive. Here, Drosophila melanogaster was used as a model organism with a simpler gut commensal community to address this issue. Using four strains of Drosophila reflecting different immune statuses, we found that wild type and immune-compromised strains had the same Acetobacteraceae-dominant pattern across their adult lifespan. However, flies with a constitutively active immune system had a distinctive gut microbiota structure that persisted even when maternally transmitted bacteria were removed and was distinguishable from its genetic background. Additionally, co-housing experiments showed that the local environment also played an important role in gut microbiota composition. When the physiology of the gut was explored, it showed that the gut internal environment was affected as a consequence of having a de-regulated immune system. Together, our results in Drosophila showed that a constantly active immune system shaped microbiota in the gastrointestinal tract. Given the evolutionary conservation of innate immunity between insects and mammals our data has implications for the shaping of the gut microbiota structure in humans with a chronically inflamed intestine.
30
Fois, Chiara Anna Maria. "A Gut-on-a-chip Model for Testing the Anti-inflammatory Effects of Active Compounds". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25967.
Abstract (sommario):
Animal models are gold standards for testing active compounds on intestinal inflammatory conditions. However, the high costs involved cannot justify their use in all circumstances, such as in food and nutrition research. This study aimed to develop a gut-on-a-chip in vitro platform for screening the effect of anti-inflammatory compounds on gut inflammation. Because of its micrometre size, the chip allowed for reduced consumption of reagents. Furthermore, the use of constant media perfusion recreates the biological cues naturally present in the human body. CFD simulations were first performed to determine the effect of flow rate and shear stress on intestinal Caco-2 cells. These conditions were then tested and validated in vitro on a single-chamber chip to establish cell monolayers featuring tight junctions and other proteins. Co-cultures of Caco-2 with classically activated M1 macrophages were established in a double-chamber chip to represent the interaction between epithelial and immune cells. It was also found that damages of the intestinal barrier in vitro could be recreated via inflammatory triggers with TNF-α+LPS. Furthermore, this gut-on-a-chip was paired with a highly sensitive gene expression analysis for screening of over two hundred genes involved in human inflammation. To validate the functionality of the system, Dexamethasone and Mesalazine were used to modulate inflammation in both Caco-2 and M1 cells co-cultured in the gut-on-a-chip. To complement the study, Australian propolis was adopted as a natural product with anti-inflammatory properties. Regulations of genes involved in inflammatory mechanisms such as MAP2K6, COX2 and TNF were also recorded, resembling in vivo conditions. The findings suggest that the model developed in this study is functional and cost-effective and given the lowered consumption of reagents, this gut-on-a-chip could be used not only in the nutraceutical industry but also for the screening of expensive pharmaceuticals.
31
Eisa, Osama Eltayeb Idris. "Modulators of innate gut immunity to enteric viral infections : murine norovirus (MNV) as a model". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271239.
Abstract (sommario):
Challenged by a huge and diverse antigenic stimulus, the intestinal mucosa has developed a unique immune system that mainly functions to maintain tolerance to innocuous antigens while retaining the ability to respond swiftly to pathogenic threats. Central to this specialised immune system are the Intraepithelial Lymphocytes (IELs). These cells are uniquely located between Intestinal Epithelial Cells (IECs) ready to respond to exogenous antigens in the intestinal lumen. The intestinal immune system is constantly influenced, not only by the commensal microbiota, but also by the nutritional status of the host and the availability of certain essential micronutrients that are derived from a healthy-balanced diet. Additionally, age has a significant impact on the efficiency of gut immunity in responding to infectious pathogens, as reflected by the increased burden of gastrointestinal infections at the extremes of age. In this thesis, using the Murine Norovirus (MNV) oral infection model, I aimed to characterize intestinal mucosal antiviral-responses with specific focus on the role of IELs, the impact of aging and the influence of certain micronutrients whose effects are mediated through the Aryl Hydrocarbon Receptor (AhR). Employing different knock-out and adoptive transfer experiments, I concluded that, at least in our experimental conditions and in a viral strain-specific manner, the activated IELs are not essential and may play a minor role in the protective response against MNV infection. This work also demonstrated that various MNV virus strains activate IELs differentially and for the first time (to our knowledge) revealed distinct abilities of these different Norovirus variants to infect IECs. Recognising an impaired response in old (2-year) mice, we were also able to identify a specific defect in the IFN-Lambda response of aged IECs. Furthermore, using the model of MNV infection to investigate the role of AhR signalling, the data I generated suggested a direct link between constitutive AhR signalling and innate interferon-mediated responses. These findings have uncovered a potential preventive/therapeutic targets for enhancing anti-viral responses.
32
Djamiatun, Kis. "In vitro studies on induction of lymphocyte and cytokine responses to the gut protozoans Giardia lamblia and Giardia muris". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23882.
Abstract (sommario):
In mice infected with 10$ sp4$ Giardia muris cysts, a peak lymphocyte proliferation in the spleen and Peyer's patches in response to Giardia extract occurred during the elimination and latent phases, respectively. This shows that the Peyer's patch cells are more responsive than the spleen to Giardia infection. Th2-type cytokines produced by Peyer's patch cells may play a protective role during the latent and acute phases. Th1-type cytokines may contribute to this production during the elimination phase. Cytokine production in response to Giardia extract in vitro was observed in mice immunized with this extract, but not in control mice. Therefore, Giardia antigen can induce cytokine production in vitro in a specific manner.
33
Saxton, Katie. "Development and mechanisms of fluoroquinolene resitance in epidemic clostridium difficile strians in a human gut model". Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511177.
34
Goggans, Mallory. "Elucidating Tomato Steroidal Glycoalkaloid Metabolism and Effects of Consumption onthe Gut Microbiome in a Pig Model". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1594824484770731.
35
Rich, Barbara Sharon. "Development of an in vitro model for accommodation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28982.pdf.
36
Aldsworth, Timothy Grant. "Microbial in vitro model of root surface caries". Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360285.
37
Ohene-Abuakwa, Yaw. "In vitro erythroid model for diamond blackfan anaemia". Thesis, St George's, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420364.
38
Owen, Robert. "Tissue engineering an in vitro model of osteoporosis". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19265/.
Abstract (sommario):
Postmenopausal osteoporosis is a skeletal disorder characterised by bone loss. Declining oestrogen levels postmenopause disrupt bone remodelling by over-stimulating resorption. Although the disorder is currently studied in animals, we should aim to minimise their use. Therefore, this thesis explored the feasibility of developing an in vitro model of postmenopausal osteoporosis using tissue engineering principles. The response of three osteoblast cell lines, MC3T3-E1, MLOA5, and IDG-SW3, to oestrogen was explored, finding only MC3T3-E1 was stimulated by the hormone. The ability of RAW264.7 to undergo osteoclastogenesis was strongly influenced by seeding density and proliferation. Additionally, tartrate-resistant acid phosphatase (TRAP) activity could be suppressed by oestrogen exposure. Due to its ability to support osteoclastogenesis in co-culture, IDG-SW3 was the most suitable osteoblast cell line for the model. Bone-matrix deposition over 28 days on three scaffolds (PolyHIPE, polyurethane, Biotek) was compared to select the most appropriate for the model. PolyHIPE and polyurethane scaffolds supported significantly more matrix deposition than the Biotek. Mineralisation on the scaffold could be detected by micro-computed tomography; however, the presence of PBS interfered with this. Due to its cellular performance and ease of manufacture, the polyurethane scaffold was identified as the most suitable for the model. Changes in mineral content, TRAP and alkaline phosphatase activity were confirmed as markers for osteoclast and osteoblast activity in co-culture. RAW264.7 pre-treatment with oestrogen to mimic pre-menopause had lasting effects on their ability to undergo osteoclastogenesis. 2D co-cultures using oestrogen withdrawal to mimic menopause resulted in increased resorption, analogous to the effect seen in vivo. From the conditions assessed in 3D co-cultures, no equivalent response was observed. This thesis demonstrates it is possible to imitate the onset of postmenopausal osteoporosis in vitro. However, a 3D system that uses human cells and longer time periods is necessary to provide a valid alternative to animal models.
39
Davern, Jordan W. "Development of a bioengineered microvascular in vitro model". Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/201653/1/Jordan_Davern_Thesis.pdf.
Abstract (sommario):
This thesis focuses on the development of methods to create stable microvascular structures using miniaturised devices containing microchannels and water-swollen networks known as hydrogels. The combination of miniaturised devices and hydrogels provide a platform to recreate key aspects of human tissues and organs in a laboratory setting. It examines different hydrogel materials and their capacity to facilitate microvascular network formation. It also introduces a novel concept termed "on-demand matrix reinforcement" to stabilise vascular structures in generating long term microvascular studies.
40
Rebelo, Sandra da Silva. "Desenvolvimento de um modelo in vitro para avaliação de um biogel antimicrobiano com potencial para o controlo da doença periodontal canina". Master's thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2020. http://hdl.handle.net/10400.5/20210.
Abstract (sommario):
Dissertação de Mestrado Integrado em Medicina VeterináriaA doença periodontal (DP) é uma das doenças mais frequentes na espécie canina, afetando cerca de 80-85% destes animais. Esta doença, de etiologia multifatorial, inicia-se com o desenvolvimento, na superfície do dente, de placa bacteriana, um biofilme composto maioritariamente por bactérias contidas numa matriz de polissacáridos extracelulares, com o potencial de inibir a ação antimicrobiana e as defesas naturais do hospedeiro. Os processos de agregação bacteriana constituem um fenómeno bastante importante na formação de biofilme ao contribuir para a interação bacteriana durante a evolução da DP. O principal objetivo do controlo da DP é controlar a formação da placa bacteriana. Estudos realizados com isolados de Enterococcus faecalis, obtidos a partir de amostras da cavidade oral canina, demonstraram atividade antimicrobiana de um gel de goma de guar suplementado com nisina (biogel de nisina) contra esta espécie bacteriana, demonstrando a sua potencial eficácia para o controlo da DP canina. Este estudo teve como objetivos o desenvolvimento de um modelo de biofilme polimicrobiano in vitro, que seja representativo da placa bacteriana presente na cavidade oral canina, e a avaliação do potencial inibitório e de erradicação do biogel de nisina relativamente ao biofilme polimicrobiano estabelecido. As espécies bacterianas incluídas foram: Porphyromonas cangingivalis, Neisseria zoodegmatis, Corynebacterium canis, Peptostreptococcus canis e E. faecalis. Durante a primeira fase deste projeto, foi avaliada a capacidade de agregação entre os cinco isolados bacterianos. Todos os isolados demonstraram capacidade de agregação, revelando o seu potencial para a formação de biofilmes polimicrobianos. De seguida, promoveu-se a formação de um biofilme polimicrobiano constituído pelas cinco espécies bacterianas em estudo. A presença das espécies bacterianas no biofilme estabelecido in vitro foi confirmada através da sua observação direta ao microscópio de fluorescência após aplicação da técnica de “Fluorescent In Situ Hybridization”. Os resultados da avaliação do potencial inibitório e de erradicação do biogel de nisina revelaram um valor de concentração mínima inibitória de biofilme de 25 μg/mL e um valor de concentração mínima de erradicação de biofilme superior a 100 μg/mL. Ambos os valores correspondem a concentrações de nisina abaixo do limite da dose diária aceitável definida pela Organização Mundial de Saúde, que corresponde a 0 – 2 mg/Kg. Este estudo demonstrou mais uma vez a eficácia do biogel de nisina para a inibição de biofilmes polmicrobianos confirmando o potencial para a sua utilização no controlo da DP canina.
ABSTRACT - Development of an in vitro model for the evaluation of an antimicrobial biogel with potential for the control of canine periodontal disease - Periodontal disease (PD) is one of the most common diseases in dogs, affecting around 80 to 85% of the canine population. It refers to a group of conditions caused by the development of a dental plaque in the tooth surface. The dental plaque is characterized by a microbial biofilm formed by a multi-species community of microorganisms enclosed in a self-producing extracellular matrix, which protects bacteria from the host immune system and reduces the action of antimicrobial therapy. It is a well-known fact that aggregation is a specific process that plays an important role in the bacterial interactions during biofilm formation. This process contributes to the changes on bacterial composition of the biofilm during the progression of PD. Periodontal therapy aims to control the formation of bacterial plaque. Previous studies have demonstrated that, when incorporated within a guar-gum biogel (nisin-biogel), antimicrobial peptide nisin can inhibit and eradicate mono-species biofilms formed by canine oral enterococci, rendering it a potential agent for PD control. The main objectives of this project were to establish a five-species biofilm model aiming to simulate dental biofilms from dogs with PD and to use the established model to evaluate the inhibitory potential of the nisin-biogel, previously developed by our research team. The bacterial species included were: Porphyromonas cangingivalis, Neisseria zoodegmatis, Corynebacterium canis, Peptostreptococcus canis and Enterococcus faecalis. During the first task, aggregation rates between all the isolates were calculated two by two and individually. All the isolates showed aggregation ability after either a 2h or 24h incubation, showing their potential to form multi-species biofilms. Later, a five-species biofilm model was successfully established and the presence of the five bacterial species was confirmed by Fluorescent In Situ Hybridization using specific probes. The susceptibility of the multi-species biofilm to the nisin-biogel was evaluated by determination of the Minimum Biofilm Inhibitory Concentration (MBIC) and of the Minimum Biofilm Eradication Concentration (MBEC). The nisin-biogel presented inhibitory activity against the polymicrobial biofilm, with a MBIC value of 25 μg/mL and a MBEC value > 100 μg/mL, both corresponding to nisin dosages lower than the acceptable daily intake, 0 – 2 mg/Kg, set by the World Health Organization. This study demonstrated that the nisin-biogel developed by our research team can inhibit the formation of multi-species biofilms, reinforcing its potential to control canine PD.
N/A
41
Farran, B. "Developing a recombinant model of the P2Y1 and P2Y11 receptor interactions mediating relaxation in gut smooth muscle". Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1464076/.
Abstract (sommario):
ATP and ADP mediate gut smooth muscle relaxation through two receptors, P2Y1 and P2Y11. This project aims to investigate the interaction between these two receptors by developing a recombinant model of the P2Y receptors expressed in gut smooth muscle cells (SMCs) by transfecting the human P2Y11 receptor cDNA into CHO-K1 cells, which express an endogenous P2Y1 receptor. Individual clonal cell lines expressing different densities of hP2Y11 were isolated from this stably-transfected CHO-K1:P2Y11 pool and characterized. A clone expressing a “high” density of hP2Y11 (13) and a clone expressing a “low” density of hP2Y11 (6) were selected for further study. Control 1321N1 cell lines expressing each receptor in isolation (1321N1-hP2Y1 and 1321N1-hP2Y11) were used for comparison purposes. The potency (EC50) of eight different nucleotide agonists was determined in calcium assays in the co-expressing cell lines. ADP and 2meSATP responses were biphasic in clone 13 but monophasic in clone 6. To investigate the nature of the two sites of the biphasic curves in clone 13, the effect of MRS 2179, NF 340 and Reactive Red on agonist responses was determined. MRS 2179 antagonized the high affinity site of the biphasic ADP and 2meSATP responses in clone 13 without affecting the low affinity site. NF 340 had no effect on agonist responses in clone 13. Reactive Red antagonized both sites of the biphasic curves in clone 13. These data suggest that the high-affinity site of the biphasic ADP and 2meSATP responses in clone 13 corresponds to P2Y1. The low-affinity site of the 2meSATP curve is most likely P2Y11. The low-affinity site the ADP response displays both P2Y1 and P2Y11-like. The novel ADP site, therefore, is elicited by differences in the expression level of P2Y11 and may correspond to a P2Y1:hP2Y11 receptor heteromer or a macromolecular complex containing both P2Y1 and P2Y11.
42
Hoffman, Jared D. "THE PREBIOTIC INULIN BENEFICIALLY MODULATES THE GUT-BRAIN AXIS BY ENHANCING METABOLISM IN AN APOE4 MOUSE MODEL". UKnowledge, 2018. https://uknowledge.uky.edu/pharmacol_etds/24.
Abstract (sommario):
Alzheimer’s disease (AD) is the most common form of dementia and a growing disease burden that has seen pharmacological interventions primarily fail. Instead, it has been suggested that preventative measures such as a healthy diet may be the best way in preventing AD. Prebiotics are one such potential measure and are fermented into metabolites by the gut microbiota and acting as gut-brain axis components, beneficially impact the brain. However, the impact of prebiotics in AD prevention is unknown. Here we show that the prebiotic inulin increased multiple gut-brain axis components such as scyllo-inositol and short chain fatty acids in the gut, periphery, and in the case of scyllo-inositol, the brain. We found in E3FAD and E4FAD mice fed either a prebiotic or control diet for 4-months, that the consumption of the prebiotic inulin can beneficially alter the gut microbiota, modulate metabolic function, and dramatically increase scyllo-inositol in the brain. This suggests that the consumption of prebiotics can beneficially impact the brain by enhancing metabolism, helping to decrease AD risk factors.
43
Mangwana, Noluxabiso. "The in vitro faecal evaluation of prebiotic effects of rooibos phenolic compounds on the gut microbiota of vervet monkeys (Chlorocebus pygerythrus)". Thesis, Cape Peninsula University of Technology, 2020. http://hdl.handle.net/20.500.11838/3109.
Abstract (sommario):
Thesis (Master of Environmental Health)--Cape Peninsula University of Technology, 2020Background: The development of metabolic disease is accompanied by changes in gut microbiota phenotype, including a decrease of beneficial bacteria and increase of pernicious bacteria of the gastrointestinal tract. A Western (high-fat and high-sugar) diet, sedentary lifestyle and altered gut microbiota diversity have been associated with an increased risk of developing metabolic diseases such as type 2 diabetes and its associated risk factor, obesity. Many researchers have studied the link between the gut microbiota and diet. Hence our in vitro study is aimed at investigating the potential prebiotic effect of an aspalathin-rich unfermented rooibos extract, Afriplex GRT™ and aspalathin on the faecal bacterial diversity of vervet monkeys fed Western diet. Methodology: A total of six vervet monkeys (Chlorocebus pygerythrus) were selected from monkeys fed either a maize based normal diet (standard diet group; n=3) or a high fat diet (Western diet group; n=3) for more than 5-years. Faecal samples were collected from the animals in both groups at the Primate Unit and Delft Animal Centre (PUDAC) between 7 – 9 AM. Faecal samples from the two groups were divided into culture-independent baseline samples (before culture) and culture-dependent samples (after anaerobic culture). The culture-dependent samples were cultured under anaerobic conditions at 37°C for 10 hours, with or without Afriplex GRT™ extract or aspalathin. Bacterial genomic DNA (gDNA) was extracted from all samples using the NucleoSpin® DNA Stool extraction kit. Purified gDNA was sent for metagenomic sequencing for 16S rRNA gene analysis of microbial diversity using an Ion Torrent Next-generation Sequencing platform. Results: Results indicated that the Western diet affects the abundance of several bacterial species. Afriplex GRT™ and aspalathin significantly enhanced the relative abundance of health promoting butyrate-producing bacteria such as Faecalibacterium prausnitzii in both standard and Western diet groups (p= 0.02 and p=0.04, respectively). A similar trend was observed in other beneficial bacteria such as Eubacterium spp., Sutterella spp., and Dorea longicatena. Conclusion: Based on the data observed, it can be suggested that Afriplex GRT™ has a beneficial prebiotic effect on gut microbiota diversity and gut health.
44
Ogue, Bon Eva. "In vitro investigations of the effects of dietary fibres and prebiotics on probiotic growth, antimicrobial activity and the canine gut microbiota". Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511667.
45
TRETOLA, MARCO. "FORMER FOODSTUFFS PRODUCTS INTENDED FOR PIG NUTRITION: IN VITRO AND IN VIVO NUTRITIONAL EVALUATION, IMPACT ON GROWTH PERFORMANCES AND GUT HEALTH". Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/609808.
Abstract (sommario):
La produzione animale riveste un ruolo chiave nel garantire la sicurezza alimentare. Tale ruolo viene esercitato soprattutto grazie all’approvvigionamento di prodotti di origine animale e prodotti dell’agricoltura. Tuttavia, a causa delle diminuite disponibilità di terreni destinati all’allevamento ed alla agricoltura, insieme ai cambiamenti climatici e alla riduzione delle risorse idriche, diventa sempre più importante aumentare la sostenibilità e l’efficienza del settore agroalimentare. Per fare ciò, diventa necessario soddisfare le crescenti esigenze utilizzando al tempo stesso una quantità ridotta di risorse. Questa tesi ha avuto come tema principale quello di esaminare a fondo il potenziale utilizzo di scarti della industria alimentare (chiamati “former foodstuffs products”, FFPs) come ingredienti alternativi e sostenibili per la nutrizione animale. I prodotti esaminati sono alimenti che vengono scartati dalla grande distribuzione per difetti relativi alla loro forma, al loro colore, al loro packaging ecc. Tali scarti solitamente sono destinati a diventare rifiuto, nonostante il loro elevato potenziale nel poter essere utilizzati come ingredienti sostenibili per mangimi.
La prima parte della tesi si concentra sull’analisi della composizione chimica di sei diversi tipi di FFPs. Inoltre, di questi prodotti sono state anche stimate l’energia digeribile e metabolizzabile con riferimento ai suini, la digeribilità in vitro, l’indice glicemico e di idrolisi attraverso tecniche di digestione enzimatica.
La seconda parte della tesi è stata dedicata agli aspetti legati alla sicurezza dei FFPs. Campioni di FFPs sono stati quindi analizzati per la loro carica microbica e la presenza di residui di materiale di imballaggio. Per questo ultimo aspetto, sono stati testati due metodi differenti: il primo, precedentemente validato, basato sull’uso dello stereomicroscopio; il secondo, basato sull’uso dello stereomicroscopio accoppiato ad un sistema digitale di acquisizione di immagine (Computer Vision System).
L’ultima parte, invece, ha investigato gli effetti di una dieta in cui in cui i cereali comunemente utilizzati per la formulazione di diete per suini in post svezzamento, sono stati parzialmente sostituiti dagli FFPs. In particolare, una dieta di controllo e quella contenente FFPs sono state confrontate per quanto riguarda la digeribilità in vitro ed in vivo della sostanza secca, le performances di crescita di suini in post svezzamento, così come alcuni metaboliti ematici ed il microbiota fecale.
I risultati della tesi hanno dimostrato che gli FFPs possono essere considerati una “versione fortificata” dei cereali tradizionali comunemente utilizzati nel settore suinicolo, con valori di digeribilità in vitro comparabili agli stessi, ma con valori di indice glicemico e di idrolisi maggiori, caratterizzandoli come una fonte eccellente di carboidrati. Tutti i campioni di FFP sono risultati sicuri dal punto di vista microbiologico e sempre privi di Salmonella. Per quanto concerne la presenza di residui di materiale da imballaggio, il livello di contaminazione è risultata sempre al di sotto delle soglie di tolleranza. Il Computer Vision System si è inoltre rivelato essere una rapida alternativa per rilevare la presenza di materiali di imballaggio nei FFPs se accoppiata allo seteromicroscopio.
Lo studio in vivo ha rivelato che sia i valori di digeribilità in vitro che in vivo delle diete contenenti FFPs sono maggiori rispetto ai valori delle diete di controllo. Alla fine dell’esperimento, non sono state osservate differenze nelle performance di crescita, tuttavia nei suinetti alimentati con la dieta FFP c’è stato un aumento di glucosio plasmatico ed una riduzione nella concentrazione di urea.
Il sequenziamento di nuova generazione delle regioni variabili V3 e V4 del gene che codifica per il 16S rRNA hanno evidenziato come l’utilizzo di FFPs nelle diete per suini in post svezzamento riduca sia la numerosità che la biodiversità dei batteri che costituiscono il microbiota nel largo intestino. L’analisi “unweighted beta diversity” ha anche dimostrato piccole differenze nella composizione dei taxa batterici tra il gruppo FFP e quello di controllo. Inoltre, l’analisi lineare delle discriminanti ha documentato un aumento del phylum Proteobacteria ed una diminuzione del genere Lactobacillales nel gruppo FFP rispetto al controllo. Questi risultati hanno messo in evidenza il potenziale di questi ingredienti alternativi ed il loro utilizzo sicuro nella nutrizione suinicola. Il loro aumentato utilizzo potrebbe quindi portare ad una riduzione dello spreco alimentare, una riduzione dei costi del mangime, e ad un ridotto impatto ambientale della catena alimentare.Livestock play a key role in food security, through food provision, agricultural production, and by providing employment and income. However, with the diminishing availability of farmland, climate change and the threat of declining water resources, the goal is to meet the growing demand for food and feed by using fewer resources. Exploiting alternative ingredients for livestock, feed could be one way of increasing livestock sustainability. This thesis focused on processed and ready-to-eat food products that are no longer suitable for human consumption due to logistical, manufacturing or packaging defects. Such products would normally go to a landfill yet actually have a high potential of being used as sustainable feed ingredients. The first part of this thesis investigated the chemical composition of six different former foodstuff products (FFPs). Based on the FFP composition data, the digestible energy and metabolisable energy values for pigs were estimated. In addition, the in vitro digestibility values of FFPs were evaluated using a multi-step enzymatic technique. The in vitro predicted glycaemic index and hydrolysis index of the same samples were examined using a two-step in vitro digestion assay. In the second part, the safety issues linked to the use of FFPs were investigated. FFP samples were thus analysed in relation to the microbial load and the presence of presumed remnants of packaging materials. For this purpose, two different methods were used: stereomicroscopy, according to published methods; and stereomicroscopy coupled with a computer vision system. The final part addressed the effects of a diet in which common cereal grains were partially replaced by FFPs in post weaning piglet diets. Specifically, pig growth performance and selected plasma biochemical variables were evaluated in twelve post-weaning piglets. The apparent total tract digestibility of dry matter and the faecal microbiota were also characterized. When compared with common cereal grains used in pig feed formulations, FFPs can be considered a fortified version of cereals, with comparable in vitro digestibility values and with higher glycaemic and hydrolysis indexes, thus characterizing them as an excellent source of carbohydrates. All FFP samples were safe from a microbiological point of view, showing a limited microbial load and were always Salmonella free. Regarding the presumed remnants of packaging materials, the contamination level was always below the safety threshold set by German authorities, and the validated method demonstrated that packaging remnants were mainly from the 1-mm sieve mesh fraction. In order to find a more rapid and objective method for evaluating the packaging remnants, the innovative computer vision system was a rapid alternative for the detection of packaging remnants in ex-food samples when combined with a stereomicroscope. The in vivo study revealed that both in vitro and in vivo digestibility values were higher for the diet based on FFPs compared to the control diet. At the end of the experiment, no differences in growth performance were observed, however the plasma glucose increased in piglets fed FFPs compared to piglets fed the control diet, while the urea concentration decreased. The sequencing analysis of the variable regions V3 and V4 of the 16S rRNA gene showed that the use of FFPs in the post-weaning period decreased the bacterial richness and evenness in the large intestine. The unweighted beta diversity analysis also resulted in a statistically significant difference between the two groups in terms of the taxa composition. The linear discriminant analysis of effect size also demonstrated an increased amount of Proteobacteria phylum and a decreased amount of Lactobacillales genus in the FFP compared to the control group. The results highlighted the potential of these alternative feed ingredients and their safe use in pig nutrition. This is essential for establishing the best scientific practices for the use of FFPs in animal nutrition and feeding. Given the increasing need to obtain a more sustainable livestock sector, research in animal sciences should focus not only on increasing the efficiency of the animal production chain but also on the efficiency of the entire food system in ensuring sustainable nutrition. By recognizing that former foodstuffs that are not suitable for human consumption are a resource for animal nutrition and not a waste product, food and feed industries could reduce the amount of waste sent to landfill or deposed-off every year, thus saving costs, and reducing the environmental impact of the food production chain.
46
Patient, J. D. "Development of an in-vitro epithelial-myofibroblast intestinal model". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33617/.
Abstract (sommario):
In vitro studies of drug permeability are traditionally carried out using cultured monolayers of epithelial cell lines grown on semi permeable membranes. Caco-2 cells, which are colon-derived, spontaneously form polarised cell layers when cultured in vitro which are akin to an epithelium of enterocyte-like cells. The Caco-2 model has been developed as a powerful in vitro tool in the early assessment of human drug permeability and is even approved by regulatory agencies for biowaver applications (i.e. in vitro tests in lieu of in vivo animal experiments). As Caco-2 cells are derived from colon tissue they represent a more formidable barrier to drug absorption than the upper regions of the intestine which is where the majority of oral drugs permeate into the body. Whilst the Caco-2 model, alongside other in vitro methods, has provided a significant means to understand the mechanics of drug permeability. Many researchers have sought to improve upon the existing unicellular model; it is hoped that this will result in a more relevant and predictive model for researchers to test new drugs but also to dissect cellular cross talk and to probe cell-matrix interactions. Myofibroblasts are a niche cell type located subjacent to epithelial tissues which regulate the integrity, growth and differentiation of the overlying epithelium. In this study the co-culture of human epithelial cell lines with a myofibroblast cell line, CCD-18co, were investigated to study how myofibroblasts influence the barrier integrity of epithelia in vivo. Additionally, nanofibre scaffolds produced by electrospinning were explored as 3-dimensional and topographically relevant cell scaffolds to support the growth of intestinal cells in vitro. In a traditional transwell format, cultured epithelial lines Caco-2 (intestinal), HT-29 (intestinal) and Calu-3 (airway) in co-cultures with CCD-18co revealed cell-line specific response with respect to the modulation of barrier integrity. The mechanism of the modulation was confirmed to be mediated through paracrine signalling by using myofibroblast conditioned media. Fibre scaffolds which mimic the fibrillar nature of the extra cellular matrix and basement membrane were produced by electrospinning using the polymer, poly (ethylene terephthalate). Nanofibre scaffolds were characterised and further optimised for cell culture with surface coating with collagen to achieve adequate cell attachment and confluence. Work was also conducted to incorporate villi architectures into the fibre scaffolds; the potential of this ambition was investigated by using models produced by rapid prototyping. These models, which demonstrated good fidelity with the actual villi dimensions found in vivo, were used during the electrospinning process to shape the polymer scaffolds towards the geometry found in intestinal tissue. A number of molecular tracers and model drug compounds were used to evaluate the permeability profiles of Caco-2 monocultures, Caco-2/CCD-18co co-cultures cultured on the two different culture substrates in addition to the assessment of resected porcine intestinal tissue sections. Caco-2 cells and Caco-2/CCD-18co co-cultures grown on nanofibre substrates were found to have lower electrical resistance and higher permeability properties than their transwell equivalents. Caco-2/CCD-18co co-cultures on conventional transwell inserts demonstrated a permeability profile closer to the resected porcine tissue and reported human tissue values than the conventional Caco-2 model whilst maintaining p-glycoprotein assay sensitivity. This work forms a solid foundation for further research into the role of myofibroblasts in epithelial cell function and in the development of more predictive in vitro cell models for widespread scientific research.
47
Hung, Chao-Chun. "In Vitro Model Systems of a-Synuclein Over-Expression". Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485237.
Abstract (sommario):
Parkinson's disease (PD) is the second most common neurodegenerative disease in humans. Pathologically, it is characterised by an accumulation of proteinaceous intraneuronal inclusions termed Lewy bodies (LBs). a-Synuclein is the major protein found at the core of LBs. However, it is not known what stimulus causes inclusion formation, or whether LBs are cytotoxic. I wished to address these questions using cell-based model systems. Consequently, stable transfected nonneuronal (HEK293) and neuronal (SH-SY5Y) cell lines were generated and cells could be induced to express wild type or mutants of a-synuc1ein. Moreover, the Parkin inducible cell lines were generated and used as a comparison. The characterisation of a-synuclein in HEK293 cells was demonstrated to have a relatively long half-life, and over-expression had no effect on cell death. In the absence of exogenous stimuli, over-expression of a-synuclein did not form inclusions. Only after the inhibition of proteasomal activity, inclusions were observed a relatively small number of cells. The mutated A53T form appeared to make the protein more prone to aggregate, and caused a greater level of cell· death. This data suggested that additional factors are required to provide an initial seed for inclusion formation in the presence of high concentrations of a-synuclein. A proteomic approach was then applied to determine if the over-expression asynuclein caused a wide-ranging effect on the cellular proteome. Few changes were observed. However, of particular interest, one of the most significant changes was a decreased level of the proteasome a7 subunit. Although this observation suggested that the levels of proteasomal activity may be altered in cells, I went on to demonstrate that over-expression of a-synuclein did not lead to an inhibition of total cellular proteasomal activity. One observation that may explain the long-term effect of a-synuclein in cells was that its over-expression caused the induction of the unfolded protein response followed by the activation of the endoplasmic reticulum-associated protein degradation (ERAD) pathway. Chronic activation of this pathway could induce apoptosis cells, eventually causing cell death.
48
Turner, Andrew. "Vitamin D metabolism in an In Vitro mineralisation model /". Title page and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09SB/09sbt9438.pdf.
49
Sung, Hsing-Wen. "In vitro velocity measurements in a pulmonary artery model". Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/13388.
50
Tretiak, Tania. "A bovine in vitro model of human cerebral vasospasm". Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22819.
Abstract (sommario):
Cerebral vasospasm is a common cause of ischemia and death in patients suffering from cerebral hemorrhage, most notably subarachnoid hemorrhage (SAH), and it usually occurs 4-14 days after the initial episode of bleeding. Many mediators of cerebral vasospasm (CVS) have been proposed, but at this time the pathogenesis of CVS is poorly understood, and oxyhemoglobin is thought to be the principal pathogenic agent.This project was designed to examine the effects of oxyhemoglobin on the vascular tone of the middle and basilar cerebral arteries in vitro and to evaluate the validity of using bovine vessels as an animal model of the human cerebral vasculature in which to study cerebral vasospasm. Human vessels were studied in parallel with the bovine arteries to test the validity of the animal model. To further evaluate the model, some experiments were also carried out on canine vessels, because the dog has frequently been used for cerebrovascular studies in the past.
The cow is a better model of the human cerebral vasculature than the dog. Arteries respond to a variety of vasoactive stimuli, in a manner closely resembling human vessels, and can be induced into a prolonged vasospastic state by exposure to oxyhemoglobin. Vasospasm in all three species was independent of endothelial status, functional innervation, or morphological evidence of atherosclerosis. Vasospasm could not be prevented by diltiazem, nicardipine or ascorbic acid, but was partially reversed in some samples by verapamil. Bovine vessels would appear to be exceptionally useful for studies designed to test pharmacological agents for the prevention or therapy of post-hemorrhagic vasospasm and also to determine the pathophysiological mechanisms involved.