Honors Projects

Inflammatory Thermal Hypernociception in ND4 and C57BL/6 Mice: A Possible Role for Mast Cells in Initiating Inflammatory Pain

Carolina Mora Solano — Tue, 08 Dec 2009 12:32:06 PST

Pain is a cardinal component of inflammation. Mast cells are granule-filled white blood cells, know for their functions in inflammation, tissue remodeling and host defense. A number of investigations performed in rats suggest that mast cells could also be involved in the initiation of inflammatory pain mechanisms. For example, degranulation of dural mast cells produces an extended excitation of meningeal nociceptors, underlying a possible mechanism for the initiation of migraine headaches. On the other hand, thermal hyperalgesia is produced by allergen-evoked inflammation, suggesting the important role of mast cell activation and mast cell products for the induction of this response. Therefore, this study aimed to establish murine models of pain where the potentially critical role(s) of mast cells could be examined. Here we are presenting evidence that suggests we may have two novel models useful for the study of mast cells as critical initiators of inflammatory pain. The first is a model of thermal hypernociception in mice following intraplantar administration of compound 48/80 (c48/80) - a chemical inducer of mast cell degranulation - and blockade of c48/80-induced hypernociception using sodium cromolyn (SCG) - a known mast cell stabilizer. In a second mast cell-specific model of thermal hypernociception, we show that sensitization with anti-dinitrophenyl (DNP)-Immunoglobulin E followed by antigen challenge with DNP also elicits a pain response to thermal stimuli in mice. We are currently using these models to characterize the precise roles of mast cells in the inflammatory pain response.

Semaphorin and Semaphorin Receptor Expression in the Mouse

Udochukwu Obodo — Thu, 25 Sep 2008 08:59:47 PDT

Semaphorins function in the nervous system as axon guidance cues and in the immune system where they modulate immune cell activation and migration in the immune system periphery. Their roles in migration led us to hypothesize that semaphorins may be important in T-cell migration and/or activation and proliferation. Studies show that thymic T-cell migration depends on differential expression of chemokines/chemokine receptors in the different thymic regions. Likewise, the differential expression of semaphorins/semaphorin receptors in the thymic medulla and thymic cortex and on various subsets of thymus cells would suggest functional roles for these molecules in T-cell development. Reverse-transcriptase (RT)-PCR and irnmunohistochemistry results respectively show that Sema4A protein; is expressed by hematopoeitic thymic cells and is found in the thymic medulla, but not the thymic cortex. The thymic medulla contains dendritic cells (DCs) not usually found in the cortex. Moreover, Sema4A is expressed by DCs in the periphery, thus suggesting that the Sema4A-expressing cells in the medulla may be DCs. Thus, thymic DCs may express Sema4A to attractSema4A receptor-expressing thymocytes and facilitate the process of antigen presentation during negative selection in the medulla.

Investigating Auxin Metabolism in Arabidopsis thaliana Mutants With Altered Adventitious Rooting via High Throughput Indolealkanoic Acid Quantification

Ben L. Pederson — Mon, 22 Oct 2007 06:00:21 PDT

Auxins are a class of plant hormones, or phytohormones, that mediate the coordination of a number of important growth and behavioral processes in plants. The two widely distributed naturally occurring auxins are indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). Interestingly, IBA can be converted to IAA and IAA can serve as a precursor to IBA. These two events happen through two different pathways. IAA is converted into IBA in a two-step process that is only partially understood. This work aims to identify by genetic analysis the unknown enzyme involved in catalyzing the initial step in this biosynthetic conversion of IAA to IBA through the quantification of these auxins within lines of Arabidopsis thaliana mutated in genes that have been positively or negatively correlated with endogenous auxin levels and/or developmental events mediated by these hormones, such as adventitious root formation. Endogenous IAA and IBA were extracted via an automated high-throughput solid-phase extraction method and a modified post-extraction clean-up specifically designed to purify both IAA and IBA within the same sample. GC-SIM-MS analysis of samples utilized a novel IBA internal standard, [13C815N]-indole-3-butyric acid. This modified high-throughput method of multiple indolealkanoic acid quantification was applied to determine IAA and IBA concentrations in different ecotypes of Arabidopsis thaliana seedlings under different experimental growth conditions. Once optimal growth conditions for IBA production were identified, IBA and IAA levels in a series of insertional mutants revealed two gh3-6 mutants with an increased ratio of IAA to IBA concentrations suggesting that the GH3-6 protein is involved in maintaining endogenous levels of IAA and IBA.

Impact of agriculture and urban development on the community structure of wetland birds in East Central Minnesota

Christa R. von Behren — Thu, 17 May 2007 05:43:46 PDT

Wetlands are one of the fastest disappearing habitats in America. Many wetlands are also being altered due to the effects of various types of land use. Because wetlands provide important habitat for many types of birds, these species can be affected by changes in wetlands due to land use. The impacts of several wetland features, including wetland size, proximity to other wetlands, and vegetation, on bird communities have been debated in the literature. While some studies have found landscape-level features, such as connectivity to other sites to be the most important factors for explaining bird diversity, others have found within-patch characteristics to be more important. It is also unclear how these variables affect rates of nest predation in wetlands. The purpose of this study was to analyze the effects of several wetland features on wetland bird assemblages and nest predation rates at several spatial scales. Bird surveys, vegetation surveys, and measurements of nest predation were conducted at the Cedar Creek Natural History Area in East Bethel, Minnesota. Landscape analyses were conducted at four different spatial scales. Results showed that wetlands are used extensively, not only by species that breed in wetlands, but by species that breed in other environments as well, particularly by woodland birds. Results also indicated that diversity in vegetation structure is associated with an increase in the number of species using wetlands. Low bird species richness in wetlands was associated with increased amounts of agriculture and urban development, which was due to the reduction in trees in agricultural and developed areas. Unlike studies of upland species, birds responded the same way to urban development as to agriculture in the landscape. Features at both the habitat level and at broader landscape scales were found to be significantly correlated with features of the bird communities, indicating the importance of implementing conservation plans at multiple spatial scales. Results suggest that for restoration and construction of wetlands, increasing the variation in both vertical and horizontal structure within the wetland and in the surrounding landscape will increase the bird diversity within the wetland. The results of this study suggest that further encroachment of development and agriculture on wetlands in East Central Minnesota will lead to a decline in wetland bird diversity, particularly with respect to woodland birds that use the wetlands for foraging purposes. The data suggest that woodland obligates will disappear first from the area, followed by sensitive wetland obligates.

Using a Chemical Genetics Approach to Characterize the Auxin Signaling Pathway in Arabidopsis thaliana

Can M. Sungur — Tue, 01 May 2007 05:48:04 PDT

Auxins are plant hormones involved in cell elongation, phototropism, and root development. Chemical genetics combines combinatorial synthetic chemistry, high-throughput screening, and genetic analysis to understand signaling pathways by identifying small molecules that inhibit its output. Previous work identified two small molecules, furylacrylic acid and Compound C, that attenuate auxin responses. I have determined the effect derivatives of these molecules have on auxin-induced reporter gene expression, seed germination, root elongation, and activity of the SCFTIR1-Aux/IAA auxin receptor. Collectively, these data establish the specificity and the minimal components of the biologically active molecules. Future experiments will focus on confirming putative cellular targets of these molecules.

The Seasonal Impacts of Urban Development on Roadside Old Field Birds in East Central Minnesota

Elizabeth W. Goldsmith — Tue, 01 May 2007 05:46:59 PDT

The study of the ecological landscape is vital to understanding processes of disturbance, particularly in patchy urban and urbanizing areas. The study of urban ecosystems is becoming increasingly important as urban and suburban development stretch into previously rural areas. In studying urban areas, birds have frequently been used as biological indicators of habitat quality. Urban development has often been shown to decrease habitat quality for birds, but old fields (abandoned agricultural fields) frequently function as refuges for a variety of grassland birds. The purpose of this study was to examine the effects of traffic density and urban development on old field birds in the Twin Cities Metro Area in east central Minnesota

Old field bird communities along a gradient of urban development in east central Minnesota were studied during post-breeding in 2005 and peak breeding season in 2006. Bird census data were collected both summers and analyzed using direct and indirect gradient analysis. In order to better understand the patterns of bird usage of old fields, a variety of environmental variables were measured, which describe the characteristics of the fields and surrounding landscape. GIS analysis and field data collection were used to gather these environmental variables. They included hourly traffic density, vegetation cover at each site, and landscape metrics such as percent surrounding agricultural lands at various spatial scales for each study site.

The results showed that traffic density plays a dominant role in the effects of the gradient of urban development on old field birds. These bird communities respond differently to the gradient of urban development during peak breeding season and post-breeding season, with larger, more diverse communities in low-traffic fields during the breeding season and larger communities in high-traffic fields post-breeding season. Agricultural fields may support grassland bird species as secondary habitat, but their presence within the landscape may contribute to decreasing use of old fields by ecotone bird species. These findings indicate that future urban development, decreasing agricultural lands and increasing traffic density, will significantly decrease breeding bird abundance and species richness in old field bird populations unless management actions are taken. Native grassland and ecotone species will be particularly impacted by these landscape changes. However, landscape metrics point to a relatively small zone of landscape influence of approximately 100 meters. If old fields are buffered from traffic and development during the breeding season, old field birds may be able to maintain viable populations within an urban landscape.

Long-Term Outcomes of Patients with Mitral Regurgitation Undergoing Percutaneous Coronary Intervention

Catherine A. Pastorius — Thu, 04 May 2006 06:46:21 PDT

Cardiovascular disease (CVD) is the number one cause of death in industrialized nations. Survival rates after acute myocardial infarction (MI) have dramatically improved over the past decade with mortality was decreasing to 4-8% from 30% in the 1980s due to rapid revascularization and improved medical treatment. CVD and moderate leaking of the mitral valve, known as mitral regurgitation (MR), have dismal prognosis, with 5-year survival rates under 50% in patients undergoing coronary artery bypass graft (CABG) surgery. Today more patients with CVD are referred for percutaneous coronary interventions (PCI), such as stents, and their long-term outcomes after revascularizations in patients with moderate MR has not been well defined.

Therefore, we examined 711 patients retrospectively who underwent PCI at the Minneapolis Heart Institute at Abbott Northwestern Hospital in the year 2000 and had qualitative assessment of MR by left ventriculography and/or echocardiography. MR severity was divided into 3 strata: none (n=420, 59%), mild (n=209, 29%), and moderate to severe (n=82, 12%). Patients with progressively more severe MR were older, more frequently female, had a lower left ventricular ejection fraction, had a higher incidence of previous MI, and higher creatinine (all p<0.003). Patients with increasing MR severity (none versus mild versus moderate-severe MR) undergoing PCI had significantly decreased survival rates at 5 years (97%, 83.3%, 57.5%; p<0.0001 respectively). Further study will be needed to evaluate whether concomitant valve repair or CABG with repair would improve outcome in patients with moderate to severe MR requiring revascularization.