2008 MU dissertations - Freely available online
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Item The semiaquatic heteroptera (Gerromorpha) of Thailand : faunistics, biogeography and phylogeography(University of Missouri--Columbia, 2008) Vitheepradit, Akekawat; Sites, Robert William, 1954-Semiaquatic heteropterans (Gerromorpha) were collected from mountain streams and waterfalls and lowland ponds adjacent to the mountains were collected from 2002 to 2006. One hundred fifty-eight species representing 31 genera and 5 families of semiaquatic Heteroptera were collected in this study. This includes an undescribed genus, 50 undescribed species, and 7 new country records. A biogeographic study based on presence/absence data was conducted using Cluster analysis, TWINSPAN, and DECORANA to assess the compositional similarity of the Gerromorpha of highland and lowland communities. The results indicate that the species composition of southern ranges were distinctly similar to each other and substantially different from those of the ranges north of the northern limit of the Isthmus of Kra, whereas the analyses revealed no clear biogeographic patterns of the community of lowland ponds were recognized. Three distinct biogeographic groups were recognized based on species compositions of eight mountain ranges. A phylogeographic study was conducted using a ca. 750 bp fragment of the mitochondrial gene cytochrome oxidase c subunit 1 (COI) to assess if the genetic structure among populations of Ptilomera tigrina and Onychotrechus esakii . the results indicated that the populations north of and in the Isthmus of Kra differed from each other genetically, but populations within each side are similar to one to another.Item Cruciate ligament pathogenesis and its role in the initiation and progression of osteoarthritis(University of Missouri--Columbia, 2008) Breshears, Lee A. (Lee Andrew), 1974-; Cook, James L. (James Lee), 1965-The pathogenesis of cruciate ligament disease and how it may be linked to the initiation and progression of osteoarthritis were investigated using in vitro and in vivo models. Normal and diseased tissues were initially evaluated to identify genes that may be involved in this disease process. Structural, degradative and inflammatory genes were found to be expressed differentially in these tissues. Gene expression data corresponded well to protein expression when investigated. The role of mechanotransduction in ligament health was investigated. Strain amplitude and duration were found to affect these differentially expressed genes. The Pond-Nuki model was utilized to investigate and confirm the role of these genes in vivo. A novel method of matrix metalloproteinase detection was compared to traditional techniques and found to be superior to techniques currently utilized in the literature. Further investigation of these genes and molecules in cruciate ligament pathogenesis is warranted.Item Scale and stability analysis of selected atmospheric blocking events(University of Missouri--Columbia, 2008) Hussain, Athar; Lupo, Anthony R., 1966-Global six year climatology of mid latitude atmospheric blocking events, during the period 1999-2004, is presented based on the scale and stability analysis, using the NCEP/NCAR re-analysis data. A total of 278 blocking events over the Northern as well as the Southern Hemispheres are analyzed. It is pointed out that globally, over the six year period, 83% of the blocking events have single-scale dominance, whereas remaining 17% of the blocking events have an alternating-scale dominance behavior. In the Northern Hemisphere, during the later half of the six year period, a 28% rise in the planetary-scale dominance behavior blocking events is noticed over the synoptic-scale dominance behavior blocking events. A comparison of the time variability of the three stability indicators over the entire life cycle of the selected blocking events with earlier works performing the synoptic and dynamics studies shows that the three stability indicators can be used as climatologically reliable stability indicators giving useful insight into the stability of the flow attending the blocking event. It is noticed that in the scale dependent flow, the scale that dominates during the mature stage of the blocking event determines the stability of the flow during the blocking, and that the blocking is relatively more stable state than the more frequent zonal flow, irrespective of which scale dominates the flow during blocking.Item The effects of toll-like receptor ligand-activated dendritic cells on human CD4⁺T cell responses(University of Missouri--Columbia, 2008) Benwell, Risa Kitawaki, 1977-; Lee, David R.Dendritic cells (DCs) play an important role as a link between innate and adaptive immunity through their abilities to detect infection and to prime naïve T cells (signal 1 and 2). They not only activate naïve T cells, but also direct differentiation of CD4+ T cells to induce appropriate immune responses against pathogens via cytokine production (signal 3). In this study, human monocyte-derived dendritic cells (moDCs) as a model for myeloid DCs were activated in vitro with an array of Toll-like receptor (TLR) ligands derived from or mimicking various pathogens, to determine their cytokine profiles, as well as the ability of these differentially TLR ligand-activated DCs to induce differentiation of naïve CD4+ T cells. moDCs activated with a viral TLR ligand (TLR3 ligand) induced more heavily skewed Th1 responses, whereas bacterial TLR ligand (TLR1/2, 4 and 5 ligand)-activated moDCs induced more balanced Th1/Th2/Th17 responses in CD4+ T cells. Unexpectedly, moDCs activated with another viral TLR ligand (TLR7/8 ligand) also induced more balanced Th1/Th2/Th17 CD4+ T cell responses. These results provide a framework for the use of these TLR ligands in tailoring T cell responses in vaccines and other immunotherapeutic approaches.Item Multilevel models for intensive longitudinal data with heterogeneous error structure : covariance transformation and variance function models(University of Missouri--Columbia, 2008) Jahng, Seungmin, 1974-; Wood, Phillip K. (Phillip Karl)Recent developments in data collection methods in the behavioral and social sciences, such as Ecological Momentary Assessment (EMA) enables researchers to gather intensive longitudinal data (ILD) and to examine more detailed features of intraindividual variation of a variable(s) over time. Due to its high intensity of assessments within individuals, ILD often has different characteristics from traditional longitudinal data with a few measurement occasions and requires different assumptions of statistical models in use. In the present thesis, issues in the analysis of ILD and problems of current use of statistical models for the analysis of ILD are discussed and investigated. Specifically, the issue of heterogeneity of autocorrelation and variance across individuals in ILD is extensively studied for multilevel models (MLMs). In chapter 2, a brief introduction to multilevel models and issues in modeling residual covariance structure in MLMs are provided and discussed. In chapter 3, it is shown that bias in estimation of parameters in MLMs under homogeneity assumption is not ignorable when autocorrelation differs across individuals and its average is high. It is also shown that a transformation method, which multiplies variables in the model by the inverse of Cholesky factor of individual-specific error covariance, attenuates the bias for ILD. Chapter 4 reviews variance function models for heterogeneous variance and introduces a two-step MLM approach for modeling heterogeneous variance using squared residuals. A simulation study showed that the two-step MLM does not suffer from non-convergence and is applicable to ILD.