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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1071

In Vitro Regulation of Growth, Differentiation and Survival of Leukemic CD5+ B Cells

January 1995 (has links)
B cell chronic lymphocytic leukemia (B-CLL) is a hematologic neoplasm characterised by the proliferation and accumulation of sIgM+/D+ B cells that fail to progress to the final stages of B cell development. The malignant cells in B-CLL also express the pan-T cell antigen CD5, suggesting that CLL is a malignancy of the CD5+ subset of B cells. Additional characteristics of the malignant clone include a low proliferative index, enhanced in vivo survival and constitutive expression of the anti-apoptosis oncoprotein bcl-2. The behaviour of leukemic CD5 B cells in vitro contrasts their arrested in vivo state. That is, despite the majority of cells being arrested in the G0 phase of the cell cycle, the leukemic B cells are not irreversibly frozen as they can be induced to differentiate to Ig-secreting cells under appropriate in vitro conditions. Furthermore, leukemic CD5 B cells rapidly undergo death by apoptosis following in vitro culture. This thesis describes the requirements for in vitro activation of leukemic CD5+ B cells, the characterisation of the events involved in apoptosis of these cells as well as the identification of various growth factors capable of modulating these events. Stimulation of unfractionated peripheral blood lymphocytes (PBLs) from three patients with B-CLL with the phorbol ester PMA and the mitogens PHA and PWM resulted in significant increases in cell proliferation, RNA synthesis and 1gM secretion when compared to unstimulated cell populations. PMA was the most potent inducer of 1gM secretion and this occurred irrespective of the presence of residual T cells. PMA-induced proliferation and RNA synthesis were also independent of T cells. However, in the presence of T cells, these parameters of cellular activation were enhanced during in vitro culture. Thus, the inductive ability of PMA on leukemic CD5 B cells was independent of T cells. In contrast, activation and differentiation of the leukemic CD5 B cells into 1gM-secreting cells following culture with mitogens did not occur in the absence of T cells. Interestingly, co-stimulation of leukemic CD5+ B cells with PMA and anti-Ig induced cellular responses that exceeded those induced by either activator alone. Thus, leukemic CD5+ B cells from patients with B-CLL can be activated in vitro and differentiate in response to stimulation via both T cell-dependent and T cell-independent mechanisms. Apoptotic cell death was characterised in purified leukemic CD5 B cells obtained from six B-CLL patients. All leukemic CD5 B cell populations entered an apoptotic pathway in vitro as evidenced by a reduction in cell size, loss of cell viability and fragmentation of DNA into multimers of -180 base pairs. Following 24 hours of in vitro culture 24.0±16% of DNA was fragmented. After 8 days, the majority of DNA was fragmented, and fewer than 10% of cultured cells were viable. Examination of bcl-2 expression in the malignant B cells by flow cytometry revealed a unimodal pattern of expression in greater than 85% of cells from each B-CLL patient prior to culture. During in vitro culture, bcl-2 expression became bimodal such that the B cells displayed a bcl-2hjgh and bcl-2iow phenotype. The level of expression by the bCl2hjgh cells was similar to that observed prior to in vitro culture, indicating that bcl-2 is down-regulated in apoptosing cells. Interestingly, despite this downregulation, the overall number of cells positive for bcl-2 remained constant. This suggests that the enhanced survival of leukemic CD5+ B cells in vivo is mediated by the sustained expression of bcl-2 and that additional mechanisms exist capable of overriding the protective effect of bcl-2 when bcl-2 is present at reduced levels. Leukemic B cell apoptosis has previously been reported to be delayed or prevented by IL-4, IFN-y and IFN-a. These results were confirmed in this study where it was found that culture of leukemic CD5 B cells with IL-4 or IFN-y enhanced cell viability and delayed apoptosis in 6/6 and 5/6 populations of leukemic B cells, respectively. This function was also found to be shared by IL-2, IL-6, IL-13 and TNF-a as these cytokines enhanced cell viability and delayed apoptosis in some of the cell populations examined at a level similar to that observed for IL-4 and IFN-y. These cytokines may mediate their effect via the expression of bcl2 as culture in the presence of IL-2, IL-4, IL-6, IL-13, IFN-y or TNF-a resulted in a higher percentage of cells displaying the bcl-2high phenotype, compared to unstimulated cells. Taken together, these results suggest that autocrine and/or paracrine growth loops may play a role in the pathogenesis of B-CLL and that cytokines that prevent apoptosis in vitro may be targets for treatment of this B cell malignancy.
1072

Post-transcriptional regulation of gene expression in Hepatitis B virus

Panjaworayan, Nattanan, n/a January 2007 (has links)
Hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma and liver cirrhosis worldwide. HBV vaccination can prevent new infections, but effective antiviral drugs are not available for a large number of HBV infected patients. To develop novel antiviral drugs, a better understanding of the regulation of HBV gene expression is vital. One important aspect is to understand how HBV hijacks the cellular machinery to export unspliced RNAs from the nucleus of a cell to the site of incorporation into new HBV particles. The HBV post-transcriptional regulatory element (HBV PRE) is a cis acting RNA element found in all HBV transcripts. It has been reported to play an important role in the nuclear export of HBV mRNAs. Moreover, it has the ability to enhance expression of intronless as well as unspliced transcripts. Despite concerted investigations, the functional core element of HBV PRE remains unknown and the exact mechanism of how HBV PRE mediates nuclear export is unclear. This project first produced a complete HBV genome with comprehensive annotation of both coding regions and regulatory signals, which was then used for comparative genomic analysis. The functional elements of the HBV PRE were first subjected to analysis in silico. The HBV PRE is highly conserved among HBVs. Based on this sequence conservation and prediction of conserved RNA secondary structure, potentially functional HBV PRE elements including the previously reported elements (HBV SLα and HBV SLβ) were identified. Experimental deletion analysis of the HBV PRE sequence showed that the effect of each of these elements on the intronless reporter gene�s expression was similar to that of the entire full length HBV PRE. Thus, the results suggested that overall HBV PRE function was not due to additive effects from the individual elements. Surprisingly, a specific sub-section of HBV PRE decreased the level of reporter gene expression. This sub-section has not been identified previously, thus it is a novel HBV PRE inhibitory element. Further analyses using specific reporter assays revealed that the HBV PRE enhanced expression of an unspliced reporter gene whereas the RNA nuclear export elements of retroviruses, CTE (in MPMV) and RRE (in HIV-1) were not able to. Therefore, these results indicate that HBV PRE is involved in inhibition of splicing and it utilizes a different mechanism from CTE and RRE. Interestingly, HBV PRE was observed to be unable to enhance the expression of an intronless luciferase gene. Therefore, HBV PRE is not able to enhance cytoplasmic expression of all intronless transcripts. This project also addressed the idea that the RNA-binding protein, polypyrimidine tract binding protein (PTB) is a positive trans-acting factor for HBV PRE function. Transient expression of exogenous PTB in cultured cells showed no specific effect on constructs containing HBV PRE. Moreover, reduction of endogenous PTB by RNAi did not affect HBV PRE function. Therefore, the results presented in this project do not support the hypothesis that PTB plays a role in HBV PRE function. Given that HBV PRE is highly conserved and present in all HBV transcripts, it makes a good target site for novel molecular therapeutic treatments such as siRNA. To identify potential siRNA target sites within HBV PRE, an RNAi study using a plasmid expressing shRNA against HBV PRE was done. The results from the RNAi study revealed that the expression of a reporter gene could be significantly reduced by siRNA targeted to the HBV PRE. Overall, this project produced a highly annotated HBV genome that can be used as the reference sequence for comparative genomic analysis. Moreover, this work identified novel regulatory elements within HBV PRE that are likely to play an important role in HBV gene expression. Furthermore, the study also identified an excellent siRNA target site within HBV PRE that may inhibit HBV gene expression.
1073

The C+A theory of time: explaining the difference between the experience of time and the understanding of time.

Turner, Andrew J. January 2007 (has links)
The central problem addressed by this thesis is to attempt and reconcile our experience of time with our scientific understanding of time. Science tells us that time is static yet we experience it as dynamic. In the literature there tend to be two positions. Those who follow the science and claim that time is static and that our experience is mind-independent; those who favour our experience and question the science. I attempt to reconcile these positions. To do this I adopt terminology set out by McTaggart (1908) who termed the static view the B series and the dynamic view the A series. The literature that has developed out of this breaks down into the A Theory where time is the past, present and future; and the B Theory, where time is just involves events being earlier than or later than other events. I reject both positions as accounts of ontology. I adopt McTaggart’s C series, a series of betweenness only, on the grounds that it is this series that is mostly aligned to science. Given the C series, our experience requires explanation. A claim of mind-dependency is insufficient. I argue that the A series really refers to mind-dependent features that are brought out by our interaction with the C series; much like the way that colour is brought out by our interaction with a colourless world. The B series is the best description of the contents of time, not time itself. To examine the experience of time I adopt phenomenology to describe that experience. From within experience I show that certain features of that experience cannot be attributed to a mind-independent reality and use this as further evidence for the above claims. Finally I suggest that most theories of time are driven by the view that a theory of time has to be consistent. I examine recent developments in logic to see whether such a consistent requirement is needed. I conclude that the most we can get out of paraconsistent approaches is inconsistent experiences, not inconsistent reality. I conclude that the A series is the best description of our experience of time, the C series the best description of the ontology of time, and the B series as the best description of the contents of time. This reconciles our experience with our understanding of time. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1286776 / Thesis(PhD)-- School of Humanities, 2007
1074

Integrated study of group B streptococcus and human ureaplasmas : the paradigm shifts

Kong, Fanrong January 2004 (has links)
Group B streptococcus (GBS, S. agalactiae) and human ureaplasmas (U. parvumand U. urealyticum) are two clinically and phylogenetically related, potentialperinatal pathogens. Their relationships between genotypes and pathogenesis ofGBS and ureaplasma infection were still not well understood, one of the reason isthat both of them are still short of a very practical genotyping system. In the study,to solve the above problem we developed genotyping systems for the organisms (thesecond section). For human ureaplasmas, based on four genes/gene clusters (rRNAgene clusters, the elongation factor Tu genes, urease gene complexes and multiplebanded antigen genes), we designed many primer pairs suitable for developing species identification assays for the two newly established human ureaplasmaspecies (U. parvum and U. urealyticum). Further, based on the heterogeneity ofureaplasma multiple banded antigen gene (which contains species- and serovar-specific regions), we developed genotyping methods for each ureaplasma species.For GBS, based on three sets of molecular markers (capsular polysaccharidesynthesis gene clusters, surface protein antigen genes and mobile genetic elements),we developed a genotyping system. The primary evaluation of the genotypingsystems showed that the genotyping systems were practical alternative assays forthe conventional serotyping and they will be useful to further explore therelationships between genotypes and pathogenesis of GBS and ureaplasmainfection. In the study, we introduced novel data and tools into GBS and ureaplasmastudies especially from genomic- and bioinformatics-based molecular microbiology(the third section). For two newly established human ureaplasma species, based onthe U. parvum serovar-3 genome, and using the above four important genes/geneclusters, we exposed some interesting problems in the understanding of newureaplasma taxonomy especially in the post genomic era. For GBS, we studied thetwo published full genomes and exposed some new problems or possible future newresearch fields. In particular we found the two finished and one ongoing GBSgenomes were all non-typical and suggest that future genomic project had better have genetic population structure viewpoint. Finally, we suggested that integratedstudies of the two potential or conditional perinatal pathogens, from the viewpointof evolution, would provide a new understanding angle of the pathogenesis of thetwo organisms. Studies suggested that during coevolution, human ureaplasmas(especially U. parvum) became friendlier than their ancestors to their human host(by losing most of its virulence genes); however, GBS tried to increase its invasiveabilities (by getting more virulence genes) to fight against the human host attack.
1075

Consciousness in Black a historical look at the phenomenology of W.E.B. Du Bois and Frantz Fanon /

Taylor, Jack A., January 2007 (has links)
Thesis (M.Ed.)--Bowling Green State University, 2007. / Document formatted into pages; contains vi, 100 p. Includes bibliographical references.
1076

The role of B cell activating factor in B cell development and autoimmunity

Zhang, Min, January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
1077

Improving business advantage by nurturing B players through emotional intelligence

Parada Sierra, Vilma Lorena, Pham Minh, Duc January 2009 (has links)
<p>Nurturing talent inside organizations through the use of Emotional Intelligence could strength businesses competitive advantage. The use of Emotional Intelligence as a tool to create closer liaisons among staff members could provide the connection that employers need to breed their employees, particularly, their B players. Our objective is to study the processes that are built between top managers and B players within the virtual space inside organizations and the viability to elevate their performance through the use of Emotional Intelligence when creating work relationships among them.</p><p>The study was performed by a cluster of interviews to top managers, practitioners and researchers involved with our object of study and by a series of surveys completed by employees. The main results were connected to verbal language and multicommunicative activities as management of meaning from a leader, intercultural differences, general prevention towards work relationship building, influence from physical space of offices, personal space and personal satisfaction, post modernity in the leadership style, advantages of using Emotional Intelligence, positive effects that interrelations have over businesses general activities and the viability to reinforce business competitive advantage by empowering their human resources.</p><p>After the termination of this study, we could conclude that communication channels, culture context and local values and beliefs are the main aspects that influence and limit the creation of processes among our both actors and their subsequent success. Furthermore, to create work relationship inside organizations indirectly build the defensive strategy that firms need against competitors and this reinforces their business competitive advantage.</p>
1078

Effektivare inköp på B&N Nordsjöfrakt : Amos M&P

Olofsson, Ola January 2002 (has links)
No description available.
1079

An Empirical Study on Market Segmentation and Information Diffusion in Chinese Stock Markets

Cao, Chen January 2010 (has links)
<p>The efficacy and accuracy of information is very important for making decision in stock markets. In this paper, we study on the effect of information diffusion in Chinese stock market before and after the owership release in February 19, 2001, by testing the stationary of A share premium and cointegration between A and B share prices. The panel unit root tests we propose on A share premium are Augmented Dickey-Fullar (ADF) tests for individual firm and Fisher tests for the panel, based on combining pvalues from each individual cross-section. The panel cointegration tests on A and B shares we use is Johansen’s likelihood ratio tests for individual firm and likelihoodbased panel cointegraion tests for panel, based on combining the test statistics. The results show that before the opening of B share markets to domestic investors, A share premiums have a unit root and there is no cointegration relationship between A and B share markets. On the contrary, after ownership release, A share premium is stationary and there is cointegration relationship between A and B share markets.</p>
1080

Hydrogenase in Azotobacter vinelandii : the role of the heme ligands in HoxZ

Meek, Laura 23 August 1999 (has links)
Graduation date: 2000

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