Dissertations / Theses on the topic 'Maturation'
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1
Papadiamantis, Anastasios. "Maturation and ageing in biominerals with application to enamel maturation." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7155/.
Abstract:
Dental enamel consists mainly of calcium-deficient hydroxyapatite (CDHA). The formation and evolution of enamel is a progressive and complex process the final stage of which is post-eruptive maturation (PEM), when mineralisation is completed following tooth eruption and exposure to oral fluids. Although PEM is directly correlated with decrease in caries susceptibility, a complete model to describe the whole process does not exist. Several reports have recently suggested that the previously observed caries decline, which started with the introduction of F- in drinking water and dental products, has stopped and is in some cases in reverse. New research approaches are therefore needed, which will focus on caries prevention and not treatment. This project monitored the in vitro effects of simulated PEM on the physicochemical properties of dental enamel and proposed a model which describes the whole process. For this purpose, primary and permanent bovine enamel was tested, using a suitably designed demineralisation/remineralisation laboratory protocol as well as characterisation techniques. The results were applied to the synthesis of enamel proxies, which could mimic the physicochemical properties of dental enamel; these proxies were evaluated for their potential to be used as enamel substitutes in dental research.
2
Brunious, Wendell J. "Maturation of Practices." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1855.
Abstract:
The disparate concepts of Pop Art and abstract painting heavily influence the scope of my work. Finding a link between these two concepts has been the focal point of my studio practices. The apex of my process is the focus on commercial imagery as abstract form. The merging of these two concepts presents a complex composition of balance, color and information.
This thesis explores the various concepts as well as influences that have propelled the evolution of my work. It chronicles the steps I have taken in my quest to articulate my conceptual ideas. By describing the works and defining their characteristics, this analysis gives further insight to my perception as well as process.
3
Wang, Ling. "Mouse oocyte maturation: How similar is it to frog oocyte maturation?" Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27075.
Abstract:
In this study, I have attempted to address the similarities/differences between amphibian and mouse oocytes by focusing on two aspects of mouse oocyte maturation. In the first project, I investigated the ability of several antagonists of serotonin receptors to initiate follicle-enclosed mouse oocytes to undergo maturation. I demonstrated that ritanserin, but not any others, was capable of inducing oocyte maturation in the intact mouse follicles. Significantly, ritanserin is also capable of inducing frog oocyte maturation, as demonstrated by others in our lab. These results therefore suggested that a similar cAMP-elevating G protein coupled receptor, the target of ritanserin, is responsible for maintaining prophase arrest in both frog and mouse oocytes. In the second project, I have investigated the ability brefeldin A (BFA), a specific inhibitor of a small G protein ARF1, to initiate mouse oocyte maturation, as it has been suggested that BFA is capable of inducing frog oocyte maturation. I demonstrated that BFA indeed was as potent as human chorionic gonadotropin (HCG) to initiate follicle-enclosed oocytes to undergo germinal vesicle breakdown. However, BFA-treated oocytes failed to complete maturation and, instead, were arrested at metaphase I with apparently normal bipolar spindles. We further demonstrated a dominant negative mutant of ARF1 (ARF1-T31N-HA) similarly arrested the maturing oocytes at metaphase I.
These studies helped reinforce the idea that oocyte maturation is fundamentally the same in mammals as it is in amphibians. The experimentally observed differences may not be very significant biologically. This concept will be discussed in conjunction with recently published literature. (Abstract shortened by UMI.)
4
Tiklová, Katarína. "Airway maturation in Drosophila." Doctoral thesis, Stockholms universitet, Wenner-Grens institut, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62419.
Abstract:
Tubes are a fundamental unit of organ design. Most of our major organs like the lung, kidney and vasculature are composed primarily of tubes. To identify fundamental biological principles of tubular organ formation we used the respiratory organ of Drosophila melanogaster, the trachea.This work dissects embryonic trachea maturation. Three precise epithelial transitions occur during airway maturation. A secretion burst deposits proteins into the lumen; then luminal material is cleared and finally liquid is removed. We identified the cellular mechanisms behind these transitions. Sar1 and γCOP are required for protein secretion, matrix assembly and tube expansion. Rab5-dependent endocytic activity internalizes and clears luminal contents. The data show how programmed transitions in cellular activities form functional airways, and may reflect a general mechanism in respiratory organ morphogenesis.We further focused on tube size regulation. We identified Melanotransferrin, a new component of septate junctions that limits tracheal tube elongation. MTf is a lipid- modified, iron-binding protein attached to epithelial cell membranes, similarly to its human homologue. We show that septate junction assembly during epithelial maturation relies on endocytosis and apicolateral recycling of iron-bound MTf. Mouse MTf complements the defects of Drosophila MTf mutants. This provides the first genetic model for the functional dissection of MTf in epithelial morphogenesis. In the last part, we describe two genes, which are selectively involved in tube diameter expansion. Obst-A and Gasp are closely related proteins with characteristic chitin-binding domains. They are strongly expressed in the trachea at the time of lumen expansion. The single and double mutants cause a tube diameter reduction, whereas their overexpression leads to its increase. We propose that Obst-A and Gasp organize luminal matrix assembly and thereby regulate the extent of tube diameter expansion.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.
5
Herbert, Mary. "Maturation of human oocytes." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362470.
6
Davies, S. "Oocyte maturation in mice." Thesis, University of Essex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377928.
7
Low, Nigel Murray. "Mimicking antibody affinity maturation." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364567.
8
Collins, Angela Joyce. "Maturation-related genes from eucalyptus." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365297.
9
Soegiharto, Benny Mulyono. "Skeletal maturation assessment in orthodontics." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445101/.
Abstract:
Aims: (1) To assess skeletal maturation in orthodontics using hand-wrist and cervical vertebrae methods and (2) To characterise the morphological differences of the craniofacial and cervical vertebrae morphologies at different growth stages in two different populations.;Subjects and Methods for the main study: The study included 2,167 subjects with hand-wrist and lateral cephalometric radiographs. Of these, there were 648 Indonesian males, 303 Caucasian males (age range 10-17 years), 774 Indonesian females and 442 Caucasian females (age range 8-15 years). Each hand-wrist radiograph was observed and classified according to the Skeletal Maturation Index (SMI) (Fishman, 1982). Similarly, cervical vertebrae maturation was assessed using lateral cephalometric radiographs. The outlines of the cervical vertebrae were traced and classified according to the Cervical Vertebrae Maturation (CVM) Index (Baccetti et al., 2002). Craniofacial and cervical vertebrae morphologies were evaluated from the lateral cephalograms. Each radiograph was initially traced and then digitised using a customised computer program.;Results: 1. Repeatability study (Chapter 2) Kappa values showed substantial to good intra-operator repeatability for the Skeletal Maturation Index (SMI) and Cervical Vertebrae Maturation (CVM Index) for both ethnic groups and these two methods were used in the main study. For the cephalometric data, the Bland and Altaian method and the Lin's Concordance Correlations showed acceptable agreement and the methods were considered appropriate for use in the main study. 2. Main study: Chapter 3: Skeletal maturation stages were described using the SMI and CVM Index. On average, the Caucasian children attained each maturational stage at an earlier age than their Indonesian peers although the differences were less obvious in females than in males. Multiple regression analysis showed that, on average at any given age, the Caucasian males were 1 SMI stage ahead of the Indonesians, whilst the Caucasian females were around 0.5 SMI stage ahead of their Indonesian peers. Chapter 4: Ages of attainment of peak pubertal growth for the selected craniofacial parameters were determined. Growth curves and growth velocity curves were constructed for each of these parameters. The results for the craniofacial parameters showed that the Caucasian males attained peak pubertal growth slightly earlier than their Indonesian peers for the majority of parameters. However, in contrast to the SMI and CVM Index results, the Indonesian female, on average, reached peak pubertal growth earlier than the Caucasians for the majority of parameters. In both Indonesians and Caucasians, on average, the females reached peak pubertal growth of the craniofacial parameters earlier than the males. Chapter 5: Receiver Operating Characteristic (ROC) analysis was performed to assess, and compare, the ability of the SMI and CVM Index to discriminate between subjects who had yet to attain peak pubertal growth and those who had reached, or passed it. This analysis was based on the velocity growth curves produced for Chapter 4. Areas Under the ROC Curve analysis (AUC) for the SMI (AUC > 0.9) were greater than those for the CVM Index (AUC > 0.8) and the differences between the two methods were statistically significant (P<0.05 for all parameters investigated). Nevertheless, the curves for both SMI and CVM approached the top left comer of the ROC graphs, indicating that both tests have good discriminatory ability. The differences between the two methods ranged between only 1 and 7%. Chapter 6: Differences in the craniofacial and cervical vertebrae structures at different growth stages in both ethnic and gender groups were investigated.;Conclusions: Differences in the age of attainment of each skeletal maturation stage, as well as the age of attainment of the peak pubertal growth of selected craniofacial parameters, exist between the two ethnic and gender groups. These differences need to be taken into account in orthodontic diagnosis and treatment planning. This study also confirmed the validity of both the SMI and CVM Index to discriminate individuals into those who have yet to attain peak pubertal growth and those who have reached/passed peak pubertal growth. However, as the differences in the discriminatory ability were low, this study questions the benefit of taking additional hand-wrist radiographs when the use of lateral cephalograms can be optimised. There were differences in craniofacial and cervical vertebrae morphologies between the two ethnic and gender groups, although they were usually not statistically significant. A small number of parameters showed statistically significant differences, however, these differences were small and unlikely to be clinically relevant. Therefore this study suggests that orthodontic modalities commonly used in Caucasians, may also be applied in Indonesian subjects and that the use of the CVM Index is justified in Indonesians.
10
Haigh, R. M. "Urogastrone and fetal lung maturation." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377734.
11
Dempster, Anne Margaret. "Endothelial influences on monocyte maturation." Thesis, University of Aberdeen, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425102.
Abstract:
The aims of this project were to determine the phenotype of migrating monocytes and examine the influence transmigration has on their differentiation to macrophages or DC. To determine stages of differentiation and activation of monocytes cultured in the presence of autologous serum without endothelium nine cell surface receptors were used. These cells matured over time with an increase in CD16+ cells and increased major histocompatibility complex II and macrophage mannose receptor (MMR) expression suggesting alternative activation over time compared to cells cultured in foetal calf serum. Monocyte contact with unstimulated endothelium and a gradient of CCL2 also results in cells with an alternatively activated phenotype with a proportion having a tendency to form dendritic cells (DC). Migration of monocytes is markedly enhanced and endothelium is activated by chemokines and cytokines in the context of inflammation. Contact with endothelium activated with interferon gamma (IFNg) prevents monocytes development into alternatively activated macrophages and may bias them towards classical activation. However contact with endothelium activated with an interleukin 10 (IL-10) results in cells with an alternatively activated phenotype with a subpopulation of cells, which remain on the apical surface, showing a tendency to become DC. These results show that IFNg and IL-10 confer different effects on endothelium and monocytes. Manipulation or activation of the endothelium to program the transmigrating cells to become alternatively activated may provide a novel option to alter macrophage function for therapeutic gain.
12
Salavati, Mazdak. "Studies on in vitro maturation of dog oocytes to improve maturation rate and development potentials." Thesis, University of Bedfordshire, 2013. http://hdl.handle.net/10547/312054.
Abstract:
In vitro maturation of dog oocytes has always been the main obstacle preventing reproductive biologist from producing canine in vitro cultured embryos. The unsuccessful oocyte maturation in canine species originates from their unique physiological and biological specifications. Ovulation of dominant follicles in bitch (6-12 in each oestrous cycle) occurs at prophase I stage of oocyte nucleus and meiotic resumption develops during 3-5 days of oviductal transition. During this PhD thesis, studies were designed in order to speculate characteristics of canine oocyte maturation in vitro in terms of maturation media components, gas composition of the incubator and hormonal requirements. Level of oxidative stress during 72h (culture period) of in vitro maturation showed that 5%O2, 5% CO2 and 90% N2 composition improves meiotic resumption and reduces degeneration rate significantly compared to 5% CO2 in air. Utilization of caffeine as a non specific phosphodiesterase inhibitor at 10mM for 12h at the beginning of the 72h culture (12+60) also improved MII maturation rate (16.9% ± 2.4; P < 0.05). Among several hormonal treatments recombinant porcine Growth Hormone (PGH) at 100ng/ml and Melatonin (MTN) at 100nM concentrations had outstanding improvement over meiotic resumption (28.9% ±10.0 and 56.2% ±8.6 respectively; P < 0.05). Attempts were made to study developmental potentials of optimally matured oocytes by parthenogenetic activation (PA) and in vitro fertilization (IVF) using chilled semen. Partial digestion of the zona pellucida prior to IVF improved the cleavage rate at 48h 6.4% ± 0.3 and resulted in production of a single 8 cell embryo. Moreover; canine follicular cells were culture in order to characterize their primary culture morphology and steroidogenic responsiveness to physiological and pharmaceutical substances. Immunolocalization of aromatase (CYP19) positive cell clumps, presumptive oestrogen producing colonies, was identified. This primary culture also maintained its steroidogenic machinery up to 96h (measured by radioimmunoassay) with a significant increase in production of estradiol and progesterone after 72h compare to the start of the culture.
13
McPherson, Lindsay Rhona. "Energetics and maturation : tracking physiological changes through the maturation cycle of Atlantic herring (Clupea harengus L.)." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=165271.
Abstract:
This thesis focuses on the link between condition, defined as the magnitude of fat reserves, and maturation in two sub-populations of Atlantic herring (Clupea harengus L.). Histological, fatty acid (FA), univariate and multivariate analyses were used in a multi-scale approach to elucidate the relationship between body fat and maturity. Furthermore, the accuracy of commonly used proxies of condition and maturity was tested. No evidence was found to support the hypothesis that a threshold of fat must be exceeded for first maturation to occur; however, a size threshold was observed. During maturation, herring may be capable of both selectively incorporating certain FA into the ovary and also of synthesising FA within the ovary itself. Mesenteric fat was highly dynamic during maturation and likely plays a role in gonad development. Commonly used morphometric condition indices were not related to mesenteric fat and the relationship between morphometric indices and other more direct indices was dependent on maturity stage. Macroscopic maturity staging was unreliable and errors led to an under-estimation of the herring spawning stock biomass of up to 26%. A gonadosomatic index was validated which was able to discern between immature, mature and recovering fish more accurately than macroscopic staging. Few differences were found between North Sea autumn-spawning (NSAS) and Norwegian spring-spawning (NSS) herring in this study. The FA profiles of both sub-populations were similar over the maturity cycle and the effects of length and maturity stage on mesenteric fat were analogous for both populations. A photoperiod cue of first maturation was found for Atlantic herring. However, this cue differed between the subpopulations, with NSAS herring maturation being triggered by the spring equinox and NSS herring maturation being triggered later. A multi-scale approach was successfully employed to demonstrate that there is an intrinsic link between fat reserves and maturity in herring.
14
Scherrer, Serge. "Étude sur la maturation protéolytique du précurseur de la pénicilline g amidase d'Escherichia coli : compétition entre maturation et agrégation in vivo : repliement et maturation du précurseur in vitro : effet de mutations dans le gène sur la maturation." Nancy 1, 1994. http://www.theses.fr/1994NAN10408.
Abstract:
La pénicilline g amidase (pga) d'e. Coli atcc 11105 est une enzyme de haut intérêt industriel, utilisée pour la production des antibiotiques de type b-lactame. Les pga bactériennes ont la particularité d'être des hétérodimères, produits par une double protéolyse interne d'un précurseur protéique. L'utilisation au niveau industriel de la surproduction de pga par bactéries recombinées semble limitée par l'existence de ce processus de maturation. J'ai employé différentes approches pour essayer d'apporter des informations sur ce processus. Par une étude in vivo, j'ai montré que la surproduction du précurseur pga chez e. Coli, a partir de son gène cloné, entraine son agrégation dans le periplasme et que la présence de saccharose dans le milieu de culture limite cette agrégation periplasmique. Par une étude in vitro, j'ai montré que la maturation protéolytique du précurseur pga fait vraisemblablement appel à une étape autocatalytique. En effet, j'ai pu obtenir une activité pga par dénaturation, puis renaturation de précurseur pga, purifie par électroélution. J'ai étudié, in vitro, l'effet sur l'efficacité de maturation des conditions de renaturation-maturation, ainsi que la cinétique de repliement-maturation du précurseur pga. Sur la base des résultats obtenus, un modèle de renaturation-maturation in vitro du précurseur pga est proposa. Par ailleurs, un effet très complexe de la température sur le processus de renaturation-maturation in vitro a été mis en évidence. Enfin, j'ai à la fois caractérisé le phénotype et identifié les mutations portées par un grand nombre de mutants du gène pga, produits par mutagenèse au hasard par le bisulfite. La majorité de ces mutants sont affectés au niveau du processus de maturation et les résultats obtenus démontrent l'importance de l'intégrité structurale du précurseur dans le processus complexe de repliement et de maturation protéolytique. Par ailleurs, six des précurseurs mutants présentaient des propriétés intéressantes, que j'ai étudiées in vivo et in vitro
15
Agervald, Åsa. "Maturation and Regulation of Cyanobacterial Hydrogenases." Doctoral thesis, Uppsala universitet, Mikrobiell Kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110871.
Abstract:
Accelerated global warming plus an increasing need for energy is an equation not easily solved, thus new forms of sustainable energy production are urgently requested. In this context hydrogen production based on a cyanobacterial system offers an environmentally friendly alternative for energy capture and conversion. Cyanobacteria can produce hydrogen gas from sun light and water through the combination of photosystems and hydrogenases, and are suitable to cultivate in large scale. In the present thesis the maturation process of [NiFe]-hydrogenases is investigated with special focus on transcription of the accessory genes encoding proteins needed for assembly of the large and possibly also for the small hydrogenase subunit. The cyanobacteria used are two N2-fixing, filamentous, heterocystous strains; Nostoc sp. strain PCC 7120 and Nostoc punctiforme PCC 73102. For a biotechnological exploration of hydrogen production tools for regulatory purposes are important. The transcription factor CalA (cyanobacterial AbrB like) (Alr0946 in the genome) in Nostoc sp. strain PCC 7120 was found to be involved in hydrogen metabolism by regulating the transcription of the maturation protein HypC. Further the bidirectional hydrogenase activity was down-regulated in the presence of elevated levels of CalA, a result important to take into account when optimizing cyanobacteria for hydrogen production. CalA regulates at least 25 proteins in Nostoc sp. strain PCC 7120 and one of the down-regulated proteins was superoxide dismutase, FeSOD. The characterization of FeSOD shows that it has a specific and important function in the oxidative stress tolerance of Nostoc sp. stain PCC 7120. Since CalA is involved in regulation of both the hydrogen metabolism as well as stress responses these findings indicate that Alr0946 is an important transcription factor in Nostoc sp. strain PCC 7120 active on a global level in the cell. This thesis adds more knowledge concerning maturation and regulation of cyanobacterial hydrogenases which might be useful for future large scale hydrogen.
16
Suri, Rakesh Mark. "Dendritic cell maturation, migration and function." Thesis, University of Oxford, 1998. https://ora.ox.ac.uk/objects/uuid:47d2be37-0508-47d6-8b97-a3cf8e39f9f6.
Abstract:
Dendritic cells (DC) have a fundamental role in priming naive T-cell responses and a suspected importance in the regulation of central and peripheral tolerance. Before DC can be responsibly used in human clinical trials, the generation of both immature and mature subsets must be standardised and their in vivo migratory and functional characteristics explored. The generation of human blood monocyte-derived DC in either fetal calf serum (PCS) or autologous plasma (HP) were compared. Phenotypic and functional assays demonstrated that DC derived from either system were similarly immature and underwent comparable maturation in response to LPS, TNF-α and MCM (decreasing potencies.) Furthermore, we demonstrated that adherent cells from HP cultures were likely DC but failed to react with the anti-rat CD8 antibody OX-8 which labels nonadherent DC. DC grown from mouse bone marrow (BMDC) using GM-CSF (GM) plus (IL4) were capable of undergoing further maturation with TNF-α or LPS. In contrast, the growth of BMDC in GM alone, gave rise to N418+ immature DC which could not be matured subsequently using TNF-α, LPS or IL1-β under our conditions. The migration of immature and mature BMDC was compared after IV injection. Fluorochrome labelled cells were found in splenic T-cell areas 24 hours after injection of all DC subsets into either syngeneic or allogeneic hosts. Furthermore, DC could be re-isolated from spleen and characterised by FACS analysis at various times after administration. Tc-99m radiolabel studies demonstrated similar quantitative migration of BMDC subsets and primary splenic DC (LODACS) to peripheral tissues (spleen, liver and lung) by 24 hours after injection. Emerging evidence suggests that inhibition of costimulatory signalling during antigen presentation may lead to specific unresponsiveness. The ability of immature versus mature donor strain DC pre-treatment to alter cardiac allograft survival was investigated. Only GM-DC (immature) but not more mature GM/IL4-DC subsets were capable of inducing significant graft survival prolongation (MST>100d). Furthermore, the effect was dependant upon pre-treatment 7d before transplantation and was strain specific. The CD4+ T-cell priming patterns of immature versus mature BMDC were investigated using TCR transgenic mice recognising OVA plus MHCII. Mature OVApulsed DC were able to induce antigen-specific T-cell proliferation, activation marker upregulation and intracellular IL2, IL4 and TNF-α production, while immature GMDC proliferation was less, activation marker expression limited, and no IL4 seen. Our findings represent the first demonstration that cytokine cultured DC migrate similarly to primary DC after IV injection. Furthermore, the comparable migratory patterns of immature and mature BMDC subsets contrasts with differences in CD4+ T-cell priming responses in spleen and the unique ability of immature GM-DC to selectively induce cardiac allograft prolongation.
17
Cotta, Doné Stefania. "Nephrin - intracellular trafficking and podocyte maturation /." Stockholm, 2007. http://diss.kib.ki.se/2007/978-91-7357-411-2/.
18
Missenden, Kirstie. "Premature sexual maturation : subjectivity and discourse." Thesis, University of East London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532412.
19
Harpin, V. A. "The functional maturation of newborn skin." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603732.
20
Köchl, Robert. "Autophagosome maturation in primary rat hepatocytes." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1444897/.
Abstract:
Nutrient deprivation of eukaryotic cells elicits a rapid survival response, including the induction of autophagy. Autophagy, or "self-eating", involves the formation of autophagosomes from an unknown membrane source and the sequestration of cytosolic components, including organelles such as mitochondria, endoplasmic reticulum and small vesicles. Autophagosomes then fuse with protease-containing endosomes and their contents are degraded. This allows the cell to recycle amino acids and to reuse them for the synthesis of new proteins. To study the formation and fusion of autophagosomes, I have developed in vivo and in vitro assays, based on primary rat hepatocytes cultures. For the in vitro assay, the aim of which is to identify proteins involved in fusion, I have designed specific markers and internalized them into endosomes and autophagosomes. Both vesicle populations have been purified and used to reconstitute fusion in vitro. For the in vivo experiments I expressed the GFP-tagged autophagosomal marker, LC3, in cultured primary rat hepatocytes. By measuring the translocation of GFP-LC3 from a cytosolic pool to newly formed autophagosomes, using a high throughput-imaging system, and by assaying for the lipidation of GFP-LC3, I was able to quantify the rate and magnitude of autophagosome formation and fusion. Starvation led to an increase in the rate of autophagosome formation, and the total number of autophagosomes per cell increased more than two-fold. Autophagosome formation was independent of mTOR, a negative regulator of autophagy in yeast and many cell lines, and could be strongly inhibited by leucine, a regulatory amino acid. I then investigated the role of microtubules in the formation and fusion of autophagosomes, using the microtubule-depolymerising drugs nocodazole and vinblastine. I found that nocodazole treatment reduced the rate of autophagosome formation and completely inhibited their mobility. In addition, both drugs inhibited fusion with endosomes, showing that an intact microtubule network is also required for fusion. Interestingly, vinblastine also strongly stimulated autophagosome formation, even in nutrient-rich medium. This effect was independent of mTOR activity, but required the autophagy proteins Atg5 and Atg6, suggesting that vinblastine affects a novel signalling pathway upstream of autophagy proteins.
21
Arora, Natasha. "Developmental Maturation within the Hematopoietic System." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11341.
Abstract:
Stem cell biologists creating cells and tissues for therapies, disease modeling, and drug screening have observed that differentiating pluripotent stem cells (PSCs) tend to produce cells at an embryonic stage of development but have difficulty maturing into adult definitive cells. A better understanding of developmental maturation will provide insights into embryogenesis and permit more accurate disease modeling. In the hematopoietic system, primitive and definitive cells are distinguished by functional transplantation assays, well characterized cell surface antigens, and gene expression signatures. We examined the transition in vivo in transplanted murine hematopoietic stem cells (HSCs) and in vitro in human PSC (hPSC) derived red blood cells (RBCs). We found that the hematopoietic microenvironment of the recipient significantly affects the outcome of HSC transplantation. The earliest embryonic HSCs perform better in neonatal recipients, whereas more mature adult-like HSCs perform better in adult recipients. The preference may be related to different active hematopoietic niches in neonates and adults, as we observed adult HSCs homing to different tissues in neonatal and adult recipients. Additionally, we found that proliferation may enhance the neonatal engraftment potential of adult-like HSCs. Our data highlight the importance of the host environment on transplantation outcomes, and point to the neonatal transplant model as a tool to functionally examine the earliest HSCs and primitive derivatives of PSCs.
22
Meltzer, Ulrike Anne. "Dendritic cell maturation and antigen presentation." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407647.
23
Dalton, C. M. "Mitochondrial dynamics during mouse oocyte maturation." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1335718/.
Abstract:
Mitochondria provide the primary source of ATP for the oocyte and pre-implantation embryo and undergo a number of redistributions during oocyte maturation which may be related to developmental competence. The experiments presented in this thesis aim to examine the changes in distribution and function of mitochondria during the transition from the germinal vesicle stage to the mature metaphase II arrested egg. Mitochondrial distribution was monitored throughout oocyte maturation and accumulation of mitochondria around the first meiotic spindle was observed. This was dependent on the activities of microtubules and their associated motor proteins dynein and kinesin. Migration of the spindle to the oocyte cortex was accompanied by mitochondria but at polar body extrusion a dramatic reorganisation of mitochondria away from the cortical domain occurred, suggesting that a mechanism exists for retention of these important organelles in the oocyte during this asymmetric cell division. The role of the mitochondrial adapter proteins Trak and Miro in establishing redistribution of mitochondria was also addressed. Finally, a novel recombinant FRET probe for measuring ATP was validated for use in oocytes. Use of this probe revealed alterations to both ATP levels and ATP consumption at different stages of oocyte maturation. Furthermore, whilst the first meiotic spindle was found to be dependent on mitochondrial activity to retain its structure and function, attempts to identify subcellular heterogeneity in ATP supply and demand related to the distribution of mitochondria around the spindle did not reveal any differences. However, the presence of cumulus cells surrounding the oocyte as part of a cumulus-oocyte complex was found to influence ATP levels in the oocyte; oocytes matured as part of a cumulus-oocyte complex had higher ATP levels than those observed in oocytes which had been denuded of cumulus cells. This was found to be dependent on the presence of gap junctional communication between the somatic and germ cell compartments, since inhibition of gap junctions abolished the higher ATP levels observed in cumulus enclosed oocytes.
24
Galan, Carolina. "Epigenomics of Post-testicular Sperm Maturation." eScholarship@UMMS, 2021. https://escholarship.umassmed.edu/gsbs_diss/1153.
Abstract:
Beyond the haploid genome, mammalian sperm carry a payload of epigenetic information with the potential to modulate offspring phenotype. Morphologically mature sperm exit the testes, but cannot swim or interact with the oocyte without extensive remodeling during epididymal transit; this includes modifications to the lipid composition of the sperm membrane, gain of necessary proteins, and a dramatic shift in sperm RNA content. Epididymal maturation has also been linked to changes in the sperm methylome suggesting that the epididymis might play a broader role in shaping the sperm epigenome. First, we characterized the genome-wide methylation landscape in seven germ cell populations from throughout the male reproductive tract. Our data emphasize the stability of cytosine methylation in mammalian sperm, and identify a surprising, albeit transient, period during which sperm are associated with extracellular DNA. Second, given our interest in the small RNA repertoire of sperm we set out to address known bias in sequencing protocols by comparing several small RNA cloning protocols. We found a protocol recently developed by Kathleen Collins’ lab (OTTR) to be superior to commercially available kits in providing an accurate representation of tRNA fragment levels as compared to Northern blotting. These results not only provide a more accurate representation of tRNA fragments, but also more complexity than previously seen allowing us to reassess the true sperm small RNA content. Taken together, these results provide significant insight into the mechanisms and factors modulating sperm epigenomics during post-testicular sperm maturation.
25
Nist, Richard Neil. "Maturation of tRNA in Haloferax volcanii." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308066223.
26
Armbruster, David W. "Transfer RNA maturation in the Archaea /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487952208108583.
27
Thimon, Véronique. "Protéases et maturation épididymaire des spermatozoïdes." Tours, 2005. http://www.theses.fr/2005TOUR4016.
Abstract:
La forme germinale de l'enzyme de conversion de l'angiotensine I (ECAg) présente sur la membrane des spermatozoïdes testiculaires apparaît dans le fluide de la tête de l'épididyme, long tube pelotonné reliant le testicule au canal déférent dans lequel les spermatozoïdes de mammifères acquièrent progressivement leur pouvoir fécondant et leur motilité. Cette libération laisse dans la membrane du spermatozoïde la partie C-terminale trans-membranaire et intracellulaire de l'ECAg. Le site de coupure déterminé par spectrométrie de masse se fait entre l'Arg622 et la Leu623 de la séquence de l'ECAg ovine mature. Ce processus de libération n'est pas dépendant de la phosphorylation de l'ECA. In vitro la libération est activée par le fluide de la tête de l'épididyme, activation fortement diminuée par l'AEBSF, inhibiteur de serine protéase. Ces résultats nous ont conduit à rechercher les sérine protéases du fluide épididymaire. Nous avons découvert que la furine, une sérine endoprotéase calcium-dépendante, est présente dans le fluide depuis la tête médiane jusqu'au corps distal de l'épididyme. Un marquage métabolique montre qu'elle est synthétisée et libérée uniquement au niveau de la tête médiane. Cette protéase ne semble pas être impliquée dans la libération de l'ECA. La furine participe à la maturation protéolytique de précurseurs de nombreuses protéines et pourrait intervenir dans la maturation des protéines du fluide ou de la membrane du spermatozoïde. C'est la première fois qu'elle est mise en évidence in vivo dans un fluide biologique. Ces deux enzymes, ECAg et furine, sont libérées de façon séquentielle dans le fluide de la même région de l'épididyme. Une même sécrétase présente dans le fluide pourrait être responsable de cette libération de leur ectodomaineThe germinal form of angiotensin-I converting enzyme (ACEg) is present on the membrane of testicular spermatozoa, but is absent from testicular fluid. It first appears in the fluid of the epididymis, a long tubule that connects the testis to the deferent duct and in which mammalian spermatozoa acquire their motility and ability to fertilize an ovum. The epididymal fluid derived ACEg comes from the proteolytic cleavage of the sperm membrane bound form, which leaves the C-terminal intracellular and transmembrane part of the enzyme associated with the sperm. The cleavage site, determined by mass spectrometry, occurs between Arg622 and Leu623 of the ovine ACEg sequence. This shedding process is not dependent upon phosphorylation of ACEg and, in vitro, we found that it is increased by fluid from the proximal (caput) epididymis, and strongly reduced by AEBSF, a serine protease inhibitor. As a result of studies aimed at determining the fluid serine protease responsible for this process we identified furin, a serine endoprotease calcium-dependent, that is present in the epididymal fluid. Metabolic labeling studies showed that furin is synthesized and released only in the middle region of the caput epididymis and is absorbed out of the fluid by the distal corpus epididymis. This protease is implicated in the proteolytic maturation of many proteins, but does not participate in the release of ACEg. This protease is likely to be involved in the maturation of other luminal or sperm plasma membrane proteins in the epididymis. Both enzymes, ACEg and furin, are released in the fluid of nearby epididymal zones. Based on their cleavage site a common fluid secretase or sheddase may be implicated in their ectodomain shedding
28
Harney, Ewan. "The evolution of maturation in Daphnia." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/9173/.
Abstract:
Maturation is a key life history transition for many organisms, due to the importance of age and size at maturity in determining fitness. Understanding how maturation phenotypes evolve requires an appreciation of the underlying ontogenetic mechanisms, including the maturation threshold, which determines when an individual ‘decides’ to mature. Maturation thresholds are poorly understood, and little is known about how phenotypically plastic or genetically variable they are, or how variable thresholds influence fitness. In this thesis the evolution of maturation thresholds is investigated using the crustaceans Daphnia magna and D. pulex. A comprehensive approach to modelling the maturation process found that the maturation threshold was a developmentally plastic trait in response to variable resource availability, and more closely resembled a process with a rate than a discrete switch. The maturation threshold also differed between genotypes for both species, and these differences were more apparent in D. magna than D. pulex. A second study of maturation in D. magna identified clone-specific parental effects in the threshold. Furthermore, these parental effects influenced growth, and reaction norms for age and size at maturity were a product of interacting effects between both growth and maturation threshold. A microarray study of gene expression changes in D. pulex found that most gene expression changes during maturation were continuous, further supporting the idea that the threshold is better thought of as a rate than a switch. This study also identified increases in vitellogenin transcripts, indicating the allocation of resources towards reproduction, and potential mechanisms for epigenetic inheritance and endocrine control of maturation. Finally the fitness consequences of variation in the maturation threshold were investigated in D. magna. Genotypes with a smaller threshold had a higher intrinsic rate of population increase, but threshold size did not correlate well with competitive success when five clones were directly competed with each other, suggesting that interactions with other factors were influencing fitness. The findings of this thesis suggest that maturation thresholds are not based on a single fixed state, but are responsive to environmental variation. The presence of heritable variation and transgenerational effects in these developmentally plastic traits suggests an important and adaptive role for them in the evolution of age and size at maturity.
29
Kaps, Miroslav. "Growth and maturation of angus cattle /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9842543.
30
Rossi, Rubiana. "Contribution à la compréhension de l'effet de maturation des graines sur leur qualité physiologique chez les légumineuses." Thesis, Rennes, Agrocampus Ouest, 2016. http://www.theses.fr/2016NSARI077/document.
Abstract:
Pendant la maturation des graines, la germination, tolérance à la dessication et longévité sont acquises de manière séquentielle. La maturation s’achève par la dessication qui amène l’embryon à l’état de quiescence. La maturité des graines à la récolte est le premier facteur qui in¿ uence la longévité et l’établissement de la culture lors du semis. On ne comprend pas comment la longévité est installée pendant la maturation et comment un séchage prématuré in¿ uence la longévité et la reprise des activités cellulaires pendant l’imbibition. L’objectif de la thèse était de répondre à ces questions en comparant les transcriptomes de graines immatures et matures de soja et Medicago truncatula pendant la dessication et l’imbibition. Les graines immatures furent récoltées après le remplissage avant la dessiccation, lorsque la longévité n’est pas encore acquise.Chez le soja, la comparaison des transcriptomes des graines immatures et matures montre que le séchage forcé n’est pas identique à la dessication in planta qui se caractérise par la synthèse de protéines chaperones. Plus de 89% des gènes différentiellement exprimés après 18 h d’imbibition présentent des pro¿ ls d’expression identiques dans les graines immatures et matures, en accord avec la germination comparable de celles-ci. L’analyse des transcrits dont la teneur augmente uniquement pendant l’imbibition des graines mature suggère la mise en place de mécanismes de réparation. La comparaison de ces données avec Medicago montre que l’imbibition des graines matures se caractérise par une sur-représentation des gènes liés auDuring seed maturation, germination, desiccation tolerance and longevity are acquired sequentially. Seed maturation is terminated by a desiccation phase that brings the embryo to a quiescent state. Seed maturity at harvest in¿ uences seed longevity and crop establishment. After harvest, seeds are usually dried to water content compatible with long term storage and post-harvest treatments. However, there is a lack of understanding of how seed longevity is acquired during seed maturation and how premature drying impacts longevity and resumption of cellular activities during imbibition. This was addressed here by comparing transcriptome changes associated with maturation drying and imbibition of seeds of soybean and Medicago truncatula, harvested at an immature stage and mature dry stage.The immature stage corresponded to end of seed ¿ lling when longevity was not acquired while other vigor traits were acquired. Transcriptome characterization in soybean revealed that enforced drying was not similar to maturation drying in planta, which stimulated degradation of chlorophyll and synthesis of protective chaperones. Eighty-nine % of the differentially expressed genes during a 18h-imbibition period showed a similar pattern between immature and mature seeds, consistent with a comparable germination between stages. An analysis of the 147 transcripts that increased during imbibition of mature seeds but not in immature seeds suggested an activation of processes associated with shoot meristem development and DNA repair. These data were compared with imbibing immature and mature seeds
31
Rouillé, Yves. "Maturation et evolution des pro-hormones neurohypophysaires. La maturation adaptative de la pro-vasotocine amphibienne : les hydrines." Paris 6, 1991. http://www.theses.fr/1991PA066316.
Abstract:
Les hormones neurohypophysaires sont des nonapeptides amides, matures a partir de precurseurs de 106 a 147 amino-acides contenant une neurophysine et eventuellement une copeptine. L'existence de deux hormones, l'une ocytocique et l'autre vasopressique, chez presque tous les vertebres revele la presence de deux lignees evolutives des poissons aux mammiferes. Dans une lignee, chaque hormone derive de la precedente par une substitution d'un acide amine en position 2, 3, 4 ou 8. Les deux lignees sont probablement issues de la duplication du gene d'une pro-hormone ancestrale. Des duplications additionnelles sont observees chez les marsupiaux et les poissons selaciens. Chez la roussette, deux nouvelles hormones ont ete identifiees, l'asn4-val8-ocytocine et la phe3,asn4,val8-ocytocine. La maturation des pro-hormones necessite l'intervention d'une endopeptidase clivant apres l'arginine 12, d'une carboxypeptidase e, d'une monooxygenase hydroxylante et d'une lyase amidante. La localisation et les ph d'action des enzymes suggerent que la maturation se deroule principalement dans le granule de secretion. Chez les anoures, a cote de la vasotocine, une regulation de la carboxypeptidase et de l'amidation produit l'hydrine 1 (vasotocinyl-gly-lys-arg) chez le xenope, et l'hydrine 2 (vasotocinyl-gly) chez les ranides et les bufonides. Les hydrines stimulent l'absorption d'eau par la vessie et la peau de la grenouille. L'hydrine 2 serait une hormone hydroosmotique des anoures terrestres, biosynthetisee par une maturation differentielle de la pro-vasotocine
32
Xu, Xiaoji. "Assessment of in vitro maturation and fertilization techniques for evaluation of oocyte maturation and sperm quality in pigs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23092.pdf.
33
Jonge, Wouter Jacob de. "Implications of arginine deficiency for growth and organ maturation studies on hair, muscle, brain and lymphoid organ maturation /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/59832.
34
Anderson, Donald P. "Rapid physical development and maturation, delayed behavioral maturation, and single birth in young adult Callimico: a reproductive strategy." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1342630196.
35
Bidzhekov, Kiril. "Investigations on endothelial maturation and anticoagulant properties." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-41786.
36
Currie, Ian Stewart. "Proliferation and maturation in developing human liver." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/27856.
Abstract:
In order to understand how human liver cells can proliferate and differentiate in vitro, a culture system was developed to support second trimester fetal liver cells. Having characterised the culture system, and demonstrated viable hepatocytes after seven days in vitro, cells were incubated with growth factors and cytokines and subject to two-colour flow cytometry to assess which cell fraction might proliferate in vitro. Experiments were then carried out to determine which circulating endocrine stimuli might initiate morphologic and functional maturation in the developing hepatocytes. Finally, urea metabolism and protein secretion were assessed in the presence and absence of glucocorticoid and different growth factors, to assess the interaction of these various stimuli at a functional level. Incubation with growth factors and cytokines showed that EGF alone caused cellular proliferation. This proliferation occurred within a primitive epithelial fraction, positive for cytokeratin 18, but negative for fibrinogen. The results showed that glucocorticoid alone brought about functional maturation in terms of increased protein secretion, with significant increases observed in α-fetoprotein, fibrinogen and α-1-antichymotrypsin secretion. This represented increased secretion per cell, as there was no effect of glucocorticoid on cell proliferation. Final experiments showed that EGF and HGF had modest stimulatory effects on urea synthesis. By contrast, KGF reduced urea synthesis by channelling ammonia into anabolic pathways. With regard to protein secretion, EGF inhibited fibrinogen and α-1-antichymotrypsin secretion, whereas, tumour necrosis factor inhibited fibrinogen alone. All of these observations were made only in the presence of dexamethasone. These data provide a frame of reference from which to develop cell-based therapies for the treatment of liver failure in clinical practice.
37
Sasseville, A. Marie-Josée. "La lamine A, localisation, maturation et interactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0012/NQ38833.pdf.
38
Zhao, Jing. "Tendon and ligament repair regeneration and maturation /." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1211389215/.
39
Dillon, John Edward Michael. "The Greek hero Perseus : myths of maturation." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303522.
40
Jovanovic, Ksenija. "Progressive maturation of CD4 single positive thymocytes." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-168051.
41
Davidson, Gary. "FGF2 requirement for podocyte maturation in-vitro." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311157.
Abstract:
FGF2 is expressed in renal podocytes as they differentiate in-vivo, as demonstrated by specific antibody staining within developing glomeruli of chicken metanephros. Mice lacking FGF2 have been generated in the laboratory by targeted deletion and kidneys of Fgf2 deficient mice appear to develop normally. Detailed histological analysis of adult kidneys from these mice however has revealed low frequency glomerular abnormalities. Additionally, a few obvious cases of glomerulosclerosis with severe podocyte damage were observed specifically in mutant mice. Taken together these observations indicate FGF2 plays a role in podocyte development and/or function. A novel culture system that allows the induction of podocyte cell differentiation in-vivo has recently been developed. The system is based on isolation of conditionally immortalised podocyte cells derived from H-2KbtsA58 transgenic (immorto) mice. Isolation of podocyte cells from renal glomeruli of wild-type and FGF2 deficient immorto mice was performed to address the functional relevance of FGF2 in podocyte development. Conditionally immortalised wild-type podocyte cells (wild-type MPCs) display characteristic features of podocytes in-vivo, however Fgf2 null MPCs show striking morphological and molecular abnormalities. Mutant podocyte cells do not undergo the epithelial-to-mesenchymal transformation (EMT) associated with normal podocyte maturation and, correspondingly, fail to differentiate. The EMT mediator Slug is up-regulated as wild-type cells differentiate but is missing in mutant cells, suggesting this transcription factor acts downstream of FGF signalling to mediate EMT associate maturation of podocytes. Fgf7 and Fgf10 expressions are lost in Fgf2 deficient MPC cells, but not in Fgf2 deficient kidney cortex, affording an explanation to the emergence of a stronger defect in-vitro.
42
Riquet, Fred. "Croissance du membre inférieur et maturation osseuse." Montpellier 1, 1991. http://www.theses.fr/1991MON11185.
43
Gil-Loyzaga, Pablo Enrique. "Maturation des éléments sensorinerveux de la cochlée." Montpellier 2, 1990. http://www.theses.fr/1990MON20287.
Abstract:
Le developpement des cellules sensorielles et des elements nerveux de la cochlee a ete analyse sous deux aspects principaux: differenciation des cellules ciliees et maturation neurochimique des fibres efferentes et efferentes. Les principaux resultats, detailles dans dix publications hors-texte concernent: 1) l'expression des antigenes des groupes sanguins b et h au cours des phases-cles de la differenciation cellulaire et de la synaptogenese, 2) la dependance etroite existant entre la differenciation cellulaire et la presence des elements nerveux, 3) la maturite neurochimique precoce de la plupart des elements nerveux afferents et efferents. Une discussion approfondie, s'ouvrant sur de larges perspectives, est centree sur deux problemes majeurs: d'une part, l'induction de la differenciation des cellules sensorielles et, d'autre part, les roles possibles des substances neuroactives au cours du developpement cochleaire
44
Virard, François. "Trafic, maturation et signalisation proapoptotique de TLR3." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10337.
45
Magne, Fabien. "Maturation de la flore intestinale chez l'enfant." Paris, CNAM, 2005. http://www.theses.fr/2005CNAM0511.
Abstract:
Le tube digestif héberge une flore bactérienne dense et complexe. La flore intestinale exerce différentes fonctions, comme la fermentation des substrats, la production de vitamines essentielles, la stimulation du système immunitaire et la protection vis-à-vis des bactéries pathogènes (effet de barrière). Cette protection vient probablement de la compétition pour les nutriments et pour les sites d'attachement à la muqueuse, mais aussi de la production des substances inhibitrices. Chez l'enfant, la prématurité et l'alimentation sont des facteurs pouvant modifier la flore intestinale et entraîner des pathologies digestives. Au cours de ce travail, les flores intestinales chez les enfants prématurés et chez les enfants au moment du sevrage ont été étudiées grâce à des méthodes moléculaires. Au cours de l'inventaire moléculaire réalisé sur la flore fécale de 16 enfants prématurés, 288 séquences ont été analysées et OTUs. Toutes les OTUs identifiées dans cette étude correspondaient à des espèces cultivables. En effet la flore fécale de ces enfants existe une grande variabilité inter-individuelle pouvant s'expliquer par les conditions de vie particulières des prématurés (hospitalisation, poses de cathéters, antibiothérapies. . . ). Lors de l'analyse de ces échantillons de selles par électrophérèse en gradient de dénaturation thermique dans le temps (TTGE), des résultats similaires ont été obtenus. Peu d'études ont décrit la flore fécale durant la période du sevrage. Dans notre étude, la flore fécale de 11 enfants a été analysée et suivie au cours de l'allaitement maternel exclusif, puis pendant et après le sevrage. Afin d'évaluer l'impact du sevrage sur la flore fécale, un même lait artificiel a été donné à tous les enfants étudiés. Par TTGE, il a été mis en évidence que la flore bactérienne évoluait au cours du temps, mais aucun bouleversement n'a été observé lors de l'introduction des laits artificiels ou lors de l'arrêt de l'allaitement maternel. L'analyse de la diversité des bifidobactéries par TTGE a montré des résultats similaires. De plus, la quantité de bifidobactéries par TTGE a montré des résultats similaires ont été obtenus. Peu d'études ont décrit la flore fécale durant la période du sevrage. Dans notre étude, la flore fécale de 11 enfants a été analysée et suivie au cours de l'allaitement maternel exclusif, puis pendant et après le sevrage. Afin d'évaluer l'impact du sevrage sur la flore fécale, un même lait atificiel a été donné à tous les enfants étudiés. Par TTGE, il a été mis en évidence que la flore bactérienne évoluait au cours du temps, mais aucun bouleversement n'a été observé lors de l'introduction des laits artificiels ou lors de l'arrêt de l'allaitement maternel. L'analyse de la diversité des bifidobactéries par TTGE a montré des résultats similaires. De plus, la quantité de bifidobactéries déterminée par PCR compétitive ne semble pas être modifiée. Dans une autre étude, l'impact de l'administration de prébiotiques durant la période de sevrage a été étudié chez des enfants, par hybridation in situ couplée à la cytométrie en flux. Deux laits artificiels enrichis en oligosaccharides (FOS et GOS) complétés ou non avec des oligosaccharides acides (hydrolysats de pectine) ont été testés et comparés avec un lait de même composition, mais sans oligosaccharides acides (hydrolisats de pectine) ont été testés et comparés avec un lait de même composition, mais sans oligosaccharideThe human gut harbors a dense and complex microbial community. This microbiota plays several roles, such as vitamin production, stimulation of the immune system and protection against pathogens. This protection is probably due to nutriment and binding site competitions but also to secretion of inhibitory substances. Prematurity and diet could modify infant intestinal microbiota and lead to digestive pathologies. During this thesis, fecal microbiota of preterm infants and evolution of this ecosystem during the weaning were investigated using molecular tools. 288 sequences, representing the fecal microbiota of 16 preterms infants, were classified into 25 OTUs (operational taxonomic unit). Diversity was low in each infant fecal sample: from one to eight OTUs. All these OTUs corresponded to cultivated bacteria. Actually, the genus Enterococcus and enterobacteria, facultative anaerobes, represented the dominant fraction of the bacterial community. Nevertheless, a high inter-individual variability could be observed and may come from hospitalization, catheter use, antibiothérapies. . . Similar results were obtained using temporal temperature gradient gel electrophoresis (TTGE). Few studies investigated the fecal microbiota during the weaning period. In this study, fecal microbiota of 11 infants was followed from exclusive breastfeeding to weaning and post-weaning. In order to analyze the impact of weaning on intestinal community, the same infant formula was given to all infants. PCR-TTGE showed that gut microbiota evolved over time,nevertheless no dramatic change was observed when formula milk was introduced or when breastfeeding was stopped. Specific PCR-TTGE showed that bifidobacterial, populations followed the same pattern. Based on competitve PCR, there was no change in the counts of bifidobacteria
46
Rainey, Billie-Jean. "Reliability of cervical vertebrae maturation staging method." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/18455/.
Abstract:
Background: Knowledge of craniofacial growth and development is a prerequisite for the comprehensive and successful management of orthodontic patients. In orthodontic treatment during adolescence, craniofacial growth is often paramount to its success of treatment, especially in patients with skeletal discrepancies. The ultimate goal, in orthodontics, would be the ability to predict accurately the onset, duration and magnitude of the peak pubertal growth spurt, particularly in relation to the mandible. The radiographic assessment of features of skeletal maturation has been extensively researched, as a means of determining an individual’s growth potential. Historically, assessments of the ossification of the bones on the hand-wrist radiograph were evaluated. However for orthodontics, in the UK and some other parts of the world, this method has been superseded by assessment of morphological features of the cervical vertebrae, on the lateral cephalogram. This increase in popularity is because the cervical vertebrae assessment prevents additional radiation to the patient. It is, therefore, safer for the patient. Aim: This study aimed to: 1. Determine the reliability and reproducibility of Cervical Vertebrae Maturation (CVM) stage assessment amongst orthodontists in training and specialist orthodontists, looking at a sample of consecutive lateral cephalograms taken at Liverpool University Dental Hospital. 2. Determine the reliability and reproducibility of CVM stage assessment amongst orthodontists in training and specialist orthodontists, looking at a sample of ideal images provided by co-author of the index, Dr J McNamara. 3. Compare the agreement of specialist orthodontists with orthodontists in training. 4. Determine whether increased experience with the index improved the agreement between observers. 5. Determine if the principal investigator (BJR) and research supervisor (JEH) agree with the experts and developers of the index (JMN/LF) and determine if they could be classified as experts. Design: This was a two phase reliability study. A group of 20 orthodontic clinicians, none of whom had used a CVM staging method previously, were trained in the use of the improved version of the CVM method for the assessment of mandibular growth using McNamara’s teaching programme. They independently assessed a sample of 72 consecutive lateral cephalograms, taken at Liverpool University Dental Hospital, on two separate occasions. The cephalograms were presented in a random order and interspersed with 11 ideal images from McNamara for standardisation. The intra- and inter-observer agreements were evaluated, for both image samples, using the weighted kappa statistic. The principal researchers also completed the two phase reliability study. Their results were analysed separately and compared to the findings for observers with no previous experience. The principal investigators then mutually agreed on staging of each radiographs and compared these to the staging given by the developers of the index, to determine if the principal investigator and research supervisor could be classified as experts. Results: The intra-observer and inter-observer agreements were substantial, (weighted kappa 0.6-0.8). The overall intra-observer agreement was 0.70 (SE 0.01) with average agreement 89%. The inter-observer agreement on the first occasion was 0.68 (SE 0.03) and 0.66 (SE 0.03) on the second occasion, with an average inter-observer agreement of 88%. Conclusions: The intra-observer and inter-observer agreement of classifying CVM stages, using the improved version of the CVM method for the assessment of mandibular growth, were substantial.
47
Archer, Madeline A., Teal M. Brechtel, Leslie E. Davis, Rinkuben C. Parmar, Mohammad H. Hasan, and Ritesh Tandon. "Inhibition of endocytic pathways impacts cytomegalovirus maturation." NATURE PUBLISHING GROUP, 2017. http://hdl.handle.net/10150/623928.
Abstract:
Endocytic processes are critical for cellular entry of several viruses; however, the role of endocytosis in cellular trafficking of viruses beyond virus entry is only partially understood. Here, we utilized two laboratory strains (AD169 and Towne) of human cytomegalovirus (HCMV), which are known to use cell membrane fusion rather than endocytosis to enter fibroblasts, in order to study a post-entry role of endocytosis in HCMV life cycle. Upon pharmacological inhibition of dynamin-2 or clathrin terminal domain (TD) ligand association, these strains entered the cells successfully based on the expression of immediate early viral protein. However, both the inhibitors significantly reduced the growth rates and final virus yields of viruses without inhibiting the expression of early to late viral proteins. Clathrin accumulated in the cytoplasmic virus assembly compartment (vAC) of infected cells co-localizing with virus tegument protein pp150 and the formation of vAC was compromised upon endocytic inhibition. Transmission electron micrographs (TEM) of infected cells treated with endocytosis inhibitors showed intact nuclear stages of nucleocapsid assembly but the cytoplasmic virus maturation was greatly compromised. Thus, the data presented here implicate endocytic pathways in HCMV maturation and egress.
48
Eaton, Laura. "Skin dendritic cells : activation, maturation and migration." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/skin-dendritic-cells-activation-maturation-and-migration(0831ed5e-c580-406c-a404-4b1eb59b040d).html.
Abstract:
Langerhans’ cells (LC) are the dendritic cells (DC) of the epidermis and, as sentinels of the immune system, act as a bridge between the innate and adaptive immune responses. When LC, and other DC, recognise an antigen or pathogen they mature and are stimulated to migrate to the lymph nodes, where they orchestrate immune responses. Pathogen derived toll-like receptor (TLR) ligands, and chemical allergens, are recognised as being potentially harmful and stimulate LC to mobilise and mature. Cytokine signals, including tumour necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-18, all induce LC migration and are required for initiating LC mobilisation in response to certain contact allergens. Subsequently, chemokines promote the migration and localisation of LC within the draining lymph nodes. Chemokines are also involved in shaping the adaptive immune response by promoting differential T cell activation, such as T helper (Th)1 or Th2 responses, which are involved in immunity against different pathogens, and also in the development of different types of chemical allergy. The hypothesis is that LC phenotype (activation, migration and chemokine production), is dependent on the nature of the challenge ligand. The murine LC-like cell line XS106 was used to investigate the response of LC following stimulation with TLR ligands and chemical allergens. In addition, LC migration in response to these stimuli was investigated in vivo and the role of TNF-α was examined using mice deficient in either one of the two TNF-α receptors; TNF-R1 or TNF-R2.XS106 cells and freshly isolated LC were associated with a selective type 2 immune response, as determined by preferential expression of type 2 associated chemokines. Furthermore, XS106 cells responded to type 2, but not to type 1, associated TLR ligands. In contrast, all of the TLR ligands tested induced the migration of LC from the epidermis in vivo. Similarly, chemical allergens failed to induce a maximal response of XS106 cells, but did induce the migration of LC in vivo. There were differences in LC migration between the two mouse strains tested, with C57/BL6 strain mice being less responsive to administration of TNF-α and the contact allergen oxazolone compared with BALB/c strain mice. However, C57/BL6 and BALB/c strain mice responded similarly after exposure to the contact allergen 2,4-dinitrochlorobenzene (DNCB). Furthermore, DNCB was able to induce LC migration in mice deficient in TNF-R2, the TNF-α receptor expressed by LC.Collectively, these data suggest a paradigm in which keratinocytes and LC in the epidermis have distinct roles in promoting type 1 and type 2 immune responses, respectively. Therefore, LC may not be activated directly by certain TLR ligands or chemical allergens that are associated with type 1 responses. Consequently the migration of LC in vivo after encounter with these stimuli may be secondary to interaction with keratinocytes, or with other skin resident cells. Together, LC and keratinocytes allow the epidermis to respond to a range of pathogens, in addition to developing the necessary type 1 and type 2 responses. Chemical allergens may have divergent cytokine signalling requirements for the induction of LC migration as, unlike other contact allergens (and other stimuli such as irritant and ultraviolet [UV]B exposure), DNCB may induce LC migration independently of TNF-α.
49
Corrigan, Douglas Paul. "Role of Zmpste24 in Prelamin A Maturation." Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etd/1046.
Abstract:
The nuclear lamins form a karyoskeleton providing structural rigidity to the nucleus. One member of the lamin family, lamin A, is first synthesized as a 74 kDa precursor, prelamin A. Following the endopeptidase and methylation reactions which occur after farnesylation of the CAAX-box cysteine, there is a second endoproteolysis that occurs 15 amino acids upstream from the C-terminal farnesylated cysteine residue. Studies with knockout mice have implicated the enzyme Zmpste24 as a candidate to carry out one or both of these proteolytic reactions. In this body of work, the CAAX endopeptidase activity of recombinant, membrane reconstituted, Zmpste24 is demonstrated using a prelamin A farnesylated tetrapeptide as substrate. To monitor the second upstream endoproteolytic cleavage a 33 kDa prelamin A carboxyl terminal tail of prelamin A was expressed in insect cells. This purified substrate possesses a fully processed CAAX box, and, therefore, constitutes a valid substrate for assaying the second endoproteolytic step in lamin A maturation. In vitro reactions with this substrate and insect cell membranes bearing recombinant Zmpste24 demonstrate that Zmpste24 may possess the ability to directly catalyze the second endoproteolytic cleavage. Previous studies on nuclear envelope fractions have ascribed this second activity to a chymotrypsin like protease. However, Zmpste24 contains the canonical HEXXH domain, a common characteristic of zinc metalloproteinases. Experiments on Zmpste24 in this work demonstrate that inactivating the HEXXH domain by site directed mutagenesis results in a loss of the first endoproteolysis reaction, while the second endoproteolytic activity is retained. Supporting these data is the observation that a truncated mutant of Zmpste24 (residues: Met1 - Pro230) that does not contain the HEXXH motif, loses the first endoproteolytic activity while retaining the second. Furthermore, this second activity is not sensitive to the metalloproteinase inhibitors EDTA and 1,10-orthophenanthroline, but is sensitive to the chymotrypsin inhibitor TPCK and its fluorescent analogue, FFCK. The fact that Zmpste24 can be affinity labeled with FFCK suggests that this second activity is directly caused by a second, yet unidentified, active site with a chymotrypsin-like catalytic mechanism.
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Kilaru, Aruna. "Changes in Avocado Transcriptome During Fruit Maturation." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/4774.