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<p>Basement membranes are dense, sheet-like forms of extracellular matrix that</p><p>surround the epithelial tissues of metazoan organisms. While these structures are</p><p>critical for epithelial support and tissue organization, basement membranes also pose</p><p>formidable barriers to most cells. However, certain specialized cells are able to breach</p><p>these barriers and move between tissues. Acquisition of cell invasive behavior by some</p><p>tumor cells is thought be an important step in cancer progression. Due to the clear basic</p><p>and clinical importance of understanding the mechanisms underlying cell invasion</p><p>through basement membranes, cell invasive behaviors has been an area of intense study.</p><p>In this work I examine a developmentally regulated model of cell invasive behavior in</p><p>the nematode worm, C. elegans. In this system a single proto-epithelial cell remodels</p><p>basement membrane to connect two epithelial tissues, the uterus and vulva. Using this</p><p>model I identify a novel role for UNC-6/Netrin signaling during this process through basement membranes. I show that Netrin signaling is a third regulatory input for AC invasion that functions partially in parallel to fos-1a and the vulval signal. Further I link netrin signaling to the formation of invasive protrusions that penetrate basement membrane.</p> / Dissertation

Cell migration and invasion are essential physiological processes required for the growth and development of all multicellular organisms. However, they have also been implicated in the pathogenesis of certain vascular system diseases and invasive cancers. In this study, we investigate two proteins involved in cell proliferation and survival signaling, p53 and Stat3, which have been found misregulated in atherosclerosis and cancer, to establish what effect they have on the development of Src-induced invasive phenotypes in aortic vascular smooth muscle cells (VSMC) and NIH 3T3 fibroblasts. In the first stage of this experiment, we investigated the tumor suppressor p53. Once believed to act primarily as a regulator of the cell cycle, DNA repair, senescence and apoptosis, current evidence suggests that p53 can also regulate cell migration and invasion. For our study, we stably transduced VSMC and NIH 3T3 fibroblasts with constitutively active Src (SrcY527F) to generate invasive cell lines with pronounced podosome and rosette formation. We established for the first time that p53 suppresses Src-induced podosome and rosette formation, extracellular matrix degradation, cell migration and invasion in these cells. We also present novel data showing that p53 suppresses these invasive phenotypes, at least in part, by up-regulating the expression of caldesmon, an actin binding protein which stabilizes stress fibers and inhibits podosome and rosette formation. In the second part of this study, we show that Stat3, a pro-survival and pro-metastatic transcription factor, is required downstream of Src for the promotion of invasive phenotypes in VSMC and NIH 3T3 fibroblasts. Interestingly we have also shown for the first time that Stat3 can localize to podosomes and rosettes in these cells. The exact physiological reasoning for this localization, however, remains to be determined. This study provides strong evidence suggesting that mutual antagonism between the anti-invasive ‘p53-caldesmon’ and pro-invasive ‘Src-Stat3’ pathways dictates the outcome of Src-induced invasive phenotypes in VSMC and NIH 3T3 fibroblasts. / Thesis (Master, Biochemistry) -- Queen's University, 2010-01-09 21:57:30.056

No description available.

No description available.

<p>Basement membranes are a dense, sheet-like form of extracellular matrix that underlie epithelia and endothelia, and surround muscle, fat and Schwann cells. Basement membranes separate tissues and protect them from mechanical stresses. Although traditionally thought of as a static support structure, a growing body of evidence suggests that dynamic basement membrane deposition and modification instruct cell behavior and morphogenetic processes. In this thesis, I discuss how changes to basement membrane affect anchor cell (AC) invasion during C. elegans uterine vulval attachment. During AC invasion, the uterine AC breaches two juxtaposed basement membranes to contact the underlying vulval epithelium. Using live-cell imaging, genetics, molecular biology and electron microscopy I identify three modifications to the BM that affect AC invasion. In Chapter 2, I describe a system for linking juxtaposed basement membranes to stably align or connect adjacent tissues. This adhesion system promotes rapid AC invasion and also regulates a more long-term connection between the uterine tissue and the hypodermal seam cell in the adult worm. Chapter 3 elucidates how the BM component SPARC promotes cell invasion. As SPARC overexpression is correlated with cancer metastasis, this aims to understand how SPARC overexpression promote invasion in a pathological situation. In Chapter 4, I discuss preliminary data showing that the AC actively secretes laminin into the basement membrane targeted for invasion. I outline how future studies could elucidate the mechanism by which AC-derived laminin might promote cell invasion. Finally, Chapter 5 discusses conclusions and future directions for these studies.</p> / Dissertation

The objective of this study was to determine the effect of nutrient density and housing on E. coli populations in beef and dairy production systems. In the first trial, sixty second trimester beef cows were housed in two different overwintering environments and provided dry hay which was either bale grazed or placed in a feed bunk. Selected pens had supplemented with dried distiller’s grain with soluble (DDGS; 2.5 kg/cow/every third day) or rolled barley (1 kg/cow/day). In the second trial, six rumen and caecal-cannulated, non-lactating, multiparous Holstein cows received one of the following diets: i) 70% forage ii) grain pellet or iii) alfalfa pellet. The latter two diets were formulated to induce subacute ruminal acidosis (SARA). All animals were randomly sorted to pens and treatments. Fecal samples were collected and cultured on selective media. E. coli were enumerated and three isolates were chosen for PCR to detect the presence of 18 selected genes encoding a range of virulence factors. These same isolates were tested for their ability to invade the human adenocarcinoma epithelial cell line HT-29. Diet did not significantly affect E. coli abundance but did influence the prevalence of virulence genes involved in adhesion of bacteria to epithelial surfaces. When the diet contained grain, cows shed isolates which were more invasive than those from cows in the other treatments. The data suggest that diet may affect the abundance of E. coli shed in the feces and increase the presence of E. coli harbouring particular virulence genes that mediate adhesion and invasion of epithelial surfaces.

The objective of this study was to determine the effect of nutrient density and housing on E. coli populations in beef and dairy production systems. In the first trial, sixty second trimester beef cows were housed in two different overwintering environments and provided dry hay which was either bale grazed or placed in a feed bunk. Selected pens had supplemented with dried distiller’s grain with soluble (DDGS; 2.5 kg/cow/every third day) or rolled barley (1 kg/cow/day). In the second trial, six rumen and caecal-cannulated, non-lactating, multiparous Holstein cows received one of the following diets: i) 70% forage ii) grain pellet or iii) alfalfa pellet. The latter two diets were formulated to induce subacute ruminal acidosis (SARA). All animals were randomly sorted to pens and treatments. Fecal samples were collected and cultured on selective media. E. coli were enumerated and three isolates were chosen for PCR to detect the presence of 18 selected genes encoding a range of virulence factors. These same isolates were tested for their ability to invade the human adenocarcinoma epithelial cell line HT-29. Diet did not significantly affect E. coli abundance but did influence the prevalence of virulence genes involved in adhesion of bacteria to epithelial surfaces. When the diet contained grain, cows shed isolates which were more invasive than those from cows in the other treatments. The data suggest that diet may affect the abundance of E. coli shed in the feces and increase the presence of E. coli harbouring particular virulence genes that mediate adhesion and invasion of epithelial surfaces.

No description available.

No description available.