<p> To maintain human health, the lymphatic system requires a structurally and functionally sound network of lymph vessels to absorb lipid-based nutrients, preserve extracellular fluid homeostasis, and mediate immune responses. Aside from lymphedema, investigations in the past few decades have found that impairment of the lymphatic vasculature is also involved in processes such as inflammation, tumor metastasis, fat metabolism, and obesity. However, despite a long history of study and rekindled vigor in the field of lymphatic vascular research, our knowledge of lymph vessel development and physiology is still quite limited. Recently, mutations in a protein family known as connexins (Cxs) were identified as the cause of lymphatic dysfunction in some cases of inherited lymphedema. This dissertation explores the role of primarily two specific connexins, Cx37 and Cx43, and the transcription factor Foxc2 in the morphogenesis and function of the lymphatic vasculature in mice. To accomplish this, phenotypic characterization of mice with genetic deficiencies (knockout mice) in Cx37, Cx43, and/or Foxc2 was performed principally via necropsy, histological techniques (immuno-fluorescence microscopy and H&amp;E staining), and Evans blue dye (EBD) injections. Developmental abnormalities were found in lymphatic vascular growth, patterning, and remodeling in mice lacking Cx37, Cx43, Foxc2 or a combined deficiency of these proteins. Reductions or complete loss of lymphatic valves were a common finding in mice lacking one or more of these proteins. These valve deficits underlay lymphatic insufficiencies that resulted in lymphedema and chylothorax in some genotypes. Foxc2 was found to be a regulator of Cx37 expression. Moreover, Foxc2 was also dependent on Cx37 function for proper morphogenesis of lymph vessels. These findings pertaining to the expression of connexins in the lymphatic vasculature, their role in lymphatic valvulogenesis, and the interdependence of Cx37 and Foxc2 during lymph-vascular development represent my original contributions to human knowledge.</p>

<p> Nitrogen deficiency is the most common and widespread nutritional deficiency affecting plants worldwide. Ectomycorrhizal symbiosis involves the beneficial interaction of plants with soil fungi and plays a critical role in nutrient cycling, including the uptake of nitrogen from the environment. The main goal of this study is to understand how limiting nitrogen in the presence or absence of an ectomycorrhizal fungi, <i>Laccaria bicolor,</i> affects the health of aspen trees, <i>Populus tremuloides.</i> Under limited nitrogen conditions, aspen tree growth and development is reduced, and mycorrhizal symbiosis may significantly improve plant biomass, providing sufficient nitrogen is available. The results of biochemical analysis also indicate that the supply of carbon to fungus associated with aspen roots is reduced as a result of aspen utilizing more sugar resources for the production of sucrose and starch within shoot tissues. Identification of metabolic pathways in aspen tree roots revealed that carbohydrate and nitrate metabolism was impacted by changing environmental conditions, including interactions with the fungi.</p>

Thesis (M. S.)--Computing, Georgia Institute of Technology, 2009. / Committee Chair: Bader, David; Committee Co-Chair: Heitsch, Christine; Committee Member: Harvey, Stephen; Committee Member: Vuduc, Richard.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

<p> <b>Aims:</b> Propofol, clinically named as Diprivan is an intravenous anesthetic known to cause hypotension in patients presenting for surgery. We have investigated the vasodilatory signaling cascade by which propofol causes hypotension using both <i>in vivo</i> and <i>in vitro </i> experimental approaches. </p><p> <b>Methods and Results:</b> Using high-fidelity microtip transducer catheter, mean arterial blood pressure (MAP) was measured in control, transient receptor potential ankyrin subtype 1 knock-out (TRPA1^-/-), transient receptor potential vanilloid 1 knock-out (TRPV1^-/-) and TRPA1-TRPV1 double-knockout mice (TRPAV^-/-) in the presence and absence of L-NAME (an endothelial nitric oxide synthase inhibitor) and penitrem A [a big-conductance calcium gated (BK_Ca) channel inhibitor]. To further support our <i>in-vivo</i> data, murine coronary microvessels were isolated and cannulated for vasoreactivity studies. Furthermore, NO production from endothelial cells isolated from mouse aorta was also measured and immunocytochemical (ICC) studies were performed to show the intracellular localization of TRPA1 and TRPV1. Our <i>in-vivo</i> data shows that the characteristic propofol-induced depressor response is dependent on TRPA1-NO-BK_Ca pathway. Interestingly, vasoreactivity studies in isolated murine left anterior ascending (LAD) arteries demonstrate that TRPA1 and TRPV1 communicate with each other and propofol-induced vasodilation is dependent on both TRPA1 and TRPV1. Moreover our data also suggest that NO production and BK channel activation are the downstream mediators in this pathway. Finally, we demonstrate that NO production is attenuated in primary endothelial cells isolated from TRPAV^-/- mice. ICC data also shows the co-localization of these channels in mouse aortic endothelial cells. </p><p> <b>Conclusions: </b>This is the first study which has shown that propofol-induced vasodilation involves TRPA1 <i>in-vivo</i> and also there is an implication of cross-talk between TRPA1 and TRPV1 in the coronary bed. Furthermore by understanding the mechanisms by which this anesthetic causes hypotension and coronary dilation will help to mitigate the potential harmful side-effects of anesthesia in patients with little cardiovascular reserve. This will in turn ensure a better and faster post-operative recovery in patients, especially benefiting those suffering from diabetes and other cardiovascular disorders.</p>

Conditional protein splicing (CPS) is an intein-mediated post-translational modification. Inteins are intervening protein elements that autocatalytically excise themselves from precursor proteins to ligate flanking protein sequences, called exteins, with a native peptide bond. Artificially split inteins can mediate the same process by splicing proteins in trans, when intermolecular reconstitution of split intein fragments occurs. An established CPS model utilizes an artificially split Saccharomyces cerevisiae intein, called VMA. In this model, VMA intein fragments are fused to the heterodimerization domains, FKBP and FRB, which selectively form a complex with the immunosuppressive drug, rapamycin. Treatment with rapamycin, therefore, heterodimerizes FKBP and FRB, and triggers trans-splicing activity by proximity association of intein fragments. Here, we engineered a CPS model to assemble inert fragments of the potent fungal ribotoxin, alpha (α)-sarcin, in vivo. Using this model, we demonstrate rapamycin-dependent protein splicing of α-sarcin fragments and a corresponding induction of cytotoxicity in HeLa cells. We further show that permissive extein context and incubation temperature are critical factors regulating the splicing of active target proteins. Ultimately, this technology could have potential applications in the fields of developmental biology and anti-tumour therapy.

Comparisons of functionally important changes at the molecular level in model systems have identified key adaptations driving isolation and speciation. For example, recent studies suggest mutations in opsins, the genes that encode retinal photoreceptors, influence colour-based female mate choice and have, thereby, contributed to the radiation of African cichlids. To test the hypothesis that the evolution of elaborate colouration in guppies (Poecilia reticulata) is also associated with opsin gene diversity, long wavelength-sensitive (LWS) opsin genes were sequenced in six species of the family Poeciliidae. Sequences of four LWS genes were amplified from the guppy genome and from mRNA isolated from adult eyes. Variation in expression was quantified using qPCR. Three of the four paralogs encode opsins that appear to be most sensitive to different wavelengths of light, as they vary at key amino acid positions. This family of LWS opsin genes was produced by a diversity of duplication events. One gene appears to be the product of retrotransposition. Between-gene PCR and DNA sequencing show that two of the guppy LWS opsins are linked in an inverted orientation. The fourth locus is a hybrid, with the first five exons most similar to one of the tandem duplicates and the last exon most similar to the other. The single-exon LWS opsin was produced prior to the divergence of families Fundulidae and Poeciliidae. The inverted tandem duplication event occurred near the base of the poecilid tree, in the common ancestor of Poecilia and Xiphophorus, and the hybrid locus is found only in the genus Poecilia. Enhanced wavelength discrimination, a likely consequence of opsin gene duplication and divergence, might have been an evolutionary prerequisite for colour based sexual selection and have led to the extraordinary colouration now observed in male guppies and in many other poeciliids.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2005. / (UnM)AAI3202116. Adviser: Arthur L. DeVries. Source: Dissertation Abstracts International, Volume: 67-02, Section: B, page: 0633.

Thesis (Ph.D.)--University of California, Berkeley, 2006. / (UMI)AAI3254111. Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0763. Adviser: Jillian F. Banfield.

Thesis (M. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 56-69). Also available in electronic format on the Internet.