Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Lymphocyte subpopulations and oxidative stress following sub-acute exposure to natural dust collected from the Nellis Dunes Recreational Area(Montana State University - Bozeman, College of Letters & Science, 2015) Leetham, Mallory Spencer; Chairperson, Graduate Committee: Deborah Keil; Deborah Keil and Jamie DeWitt were co-authors of the article, 'Oxidative stress and lung histopathology following sub-acute exposure to natural dust collected from the Nellis Dunes Recreation Area' submitted to the journal 'Bureau of Land Management Report' which is contained within this thesis.Exposure to particulate matter containing heavy metals has been linked to adverse health effects when exposure occurs in industrial settings; however, little data exist on effects associated with natural exposure settings. In this study, markers of oxidative stress and lymphocyte subpopulations in mice were observed following sub-acute exposure to metals-containing dust collected from a natural setting used heavily for off-road vehicle (ORV) recreation. Adult female B6C3F1 mice were exposed to concentrations of dust collected from seven types of surfaces at the Nellis Dunes Recreation Area. Dust representing each of the seven map units was prepared with a median diameter of < or = 4.5m and suspended in PBS immediately prior to oropharyngeal aspiration at concentrations from 0.01 - 100 mg of dust/kg body weight. Four exposures were given a week apart over 28-days to mimic a month of weekend exposures. Thymi, spleens and blood for evaluation of oxidative stress markers and lymphocyte sub-populations were collected 24 hours after the final exposure. Blood markers of oxidative stress included levels of free radicals, superoxide dismutase, total antioxidant capacity, and total glutathione. CD4, CD8, FoxP3, CD25, IL-17, and B220 cell surface markers were used for T and B cell identification using flow cytometry. Overall, no single surface type was able to consistently induce markers of oxidative stress at a particular dose or in a dose-responsive manner. The two highest concentrations of dust from one surface type increased two markers of oxidative stress, but results of other surface types were inconsistent. No statistically significant changes were observed in the splenic B220+ cells following NDRA dust exposure. Three CBN units (1, 2, and 6) showed decreases in splenic CD4+/CD25+/FoxP3- cells. These observations were relatively consistent with TiO 2, where a significant change at the highest exposure level was observed in only one measure of oxidative stress. Additionally, the TiO 2 dosing groups showed no significant changes in lymphocyte subpopulations. These results indicate that exposure to these natural, mineral dusts, under the exposure scenario of our study, while are unlikely to considerably increase the risk of oxidative damage systemically, may induce a reduction in some cell populations in exposed individuals.Item Forced unilateral nostril breathing affects lateralized cognitive functions(Montana State University - Bozeman, College of Letters & Science, 1985) Arnott, David PhillipItem Simulation of nanoparticle transport in airways using Petrov-Galerkin finite element methods(Montana State University - Bozeman, College of Engineering, 2012) Rajaraman, Prathish Kumar; Chairperson, Graduate Committee: Jeffrey HeysNanoparticles with various diameters, i.e. 1 nm d d d 150 nm, were studied with respect to their transport and deposition properties in the human airways. A finite element code, written in C++, was developed that solved both the Navier-Stokes and Advection-Diffusion equation monolithically. When modeling nanoparticles, the regular finite element method becomes unstable, and, in order resolve this issue, various stabilization methods were consider including Streamline Upwind, Streamline Upwind Petrov-Galerkin and Galerkin Least Square. In order to validate the various types of stabilization, the stabilized finite element solution was compared to the analytical Graetz solution. The comparison was done by calculation an approximation of the L 2 - error, and the best stabilization method was found to be Galerkin Least Square. Also in this thesis, we found that the Crank-Nicolson time stepping scheme is not the best option for the human airways simulations problem, and this is due to both the complex nature of the geometry and the Crank-Nicolson method lacks the ability to damp out error when the problem is advection dominated. However, using Crank-Nicolson in straight tube geometry with various stabilization methods provides better accuracy than other second-order time stepping schemes, such as BDF-2. The type of stabilization method used when d < 10 nm does matter since Streamline Upwind Petrov-Galerkin introduces higher deposition fraction compared to Galerkin Least Square. This statement is not true when d > 10 nm, since mesh refinement is important at this range. In the human airways simulation, we found that for d = 1 nm the concentration distribution is uniform compared to d = 150 nm , where localized concentration exists. This implies a potential health risk when inhaling nanoparticles because nanoparticles have a very high surface area and the potential for exposure is much greater. The stabilization methods tested in this thesis show promise for modeling nanoparticle transport in the human airways.