Department of Environmental and Radiological Health Sciences

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https://hdl.handle.net/10217/100418

These digital collections include theses, dissertations, faculty publications, and datasets from the Department of Environmental and Radiological Health Sciences. Due to departmental name changes, materials from the following historical departments are also included here: Radiology and Radiation Biology; Environmental Health.

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Now showing 1 - 20 of 264

Open Access
3-chloro-p-toluidine hydrochloride metabolism and detection of exposure in birds
(Colorado State University. Libraries, 2017) Goldade, David A., author; Marie, Legare, advisor; William, Hannemann, advisor; Gregory, Dooley, committee member; Gary, Mason, committee member
The avicide 3-chloro-4-methylanaline hydrochloride (chloro-p-toluidine hydrochloride, CPTH, DRC-1339) is used to control pest bird species that damage agricultural crops. While it is theorized that CPTH is a nephrotoxin, no definitive assessment of the mode of action has been performed. Additionally, the metabolic pathway of CPTH in birds has yet to be elucidated. Radioactively labeled [14C]-3-chloro-4-methylaniline hydrochloride (250 µg per bird) was delivered to 21 red-winged blackbirds (Agelaius phoeniceus) and 21 dark-eyed juncos (Junco hyemalis) via oral gavage, and the distribution and excretion of radioactivity were determined at 15 and 30 minutes and 1, 4, 8, 12, and 24 hours (n = 3 per time point). Direct measurement of radioactivity as well as measurement following combustion was accomplished using a liquid scintillation counter. Elimination from most tissues followed a two-compartment model, with very rapid elimination occurring between time 0 and 4 hours and a much slower elimination phase occurring after that. The average half-life of elimination for the initial phase in most tissues examined was 0.16 hours for juncos and 0.62 hours for blackbirds. The average for the slower second phase of elimination was 3.4 hours for juncos and 5.4 hours for blackbirds. The radioactivity in blackbird kidney tissues did not change significantly for the duration of the test, pointing toward the kidney as a possible site of action for this important agricultural chemical. To further explore the mechanistic toxicology of CPTH, sub-cellular preparations were made from the liver and kidney of various avian species. In-vitro metabolism experiments were performed using these preparations and the resulting metabolites were identified and quantified. Two metabolites were identified: 3-chloro-4-methylacetanilide (CAT) and N-[3-chloro-4-(hydroxymethyl)phenyl]acetamide (OH-CAT). A comparison of two methods was made for the analysis of CPTH and its metabolites. Due primarily to the solubility and volatility of the three compounds, CPTH and CAT performed well on gas chromatography tandem mass spectrometry (GC/MS/MS) and adequately on liquid chromatography tandem mass spectrometry (LC/MS/MS). Conversely, OH-CAT performed optimally on LC/MS/MS. LC/MS/MS was chosen as the technique for analysis of exposure data. Both methods generated residue values that demonstrated a high degree of variability between individuals. Despite the variability issues, the data showed that the primary chemical species present in the tissues of exposed birds was OH-CAT, and that the concentration of observed residue was related to the dose administered. In an effort to identify the target for tissue binding of CPTH or its metabolites in the kidney of exposed red-winged blackbirds, protein samples were extracted and digested with trypsin. Several chemical compounds were found to be significantly different between treated and control groups (α=0.05) and were subjected to tandem mass spectrometry to identify their chemical structure. Results from this analysis did not yield any identification of specific protein binding. Limitations of sensitivity and lack of sample enrichment likely led to this outcome.
Open Access
A characterization of foodborne illness data, Denver Metropolitan Area, Colorado, 1986-1989
(Colorado State University. Libraries, 1994) Higgins, Charles L., author; Salman, Mowafak Dauod, advisor; Savage, Eldon P., committee member; Reif, John S., committee member
A records search was conducted for foodborne illness complaints to local health departments in the Denver, Colorado Metropolitan Area, defined as Adams, Arapahoe, Boulder, Denver, Douglas, and Jefferson counties. Records for the four-year period beginning with 1986 through 1989 were searched for reports in which two or more persons were alleged to have become ill, experienced similar symptoms and had a common food exposure. Program administrators were interviewed about the procedures used to investigate these complaint reports. The documented cases of foodborne illness in the Denver Metropolitan Area are not sufficient to justify regulatory activities or to target prevention. The assistance of the public, academic and medical community appears to be needed in order to increase the percentage of complaints that can be properly investigated.
Open Access
A comparative analysis between the rFC and LAL endotoxin assays for agricultural air samples
(Colorado State University. Libraries, 2016) Krause, Laura Ann, author; Reynolds, Stephen J., advisor; Schaeffer, Joshua W., committee member; Ellis, Robert P., committee member
Agricultural workers experience increased exposure to inhalable dust and endotoxins, which make up the outer membrane of Gram-negative bacteria species. Endotoxin has specifically been linked to an increased degree of pro-inflammatory symptoms from inhaled dust, leading to a variety of lung diseases. Because there is no standardized method of collection or analysis of endotoxin, there are paramount gaps in the knowledge of how best to collect and analyze samples. The aims of this study were to: (1) assess the recovery from PVC filters spiked with known endotoxin concentrations; and (2) compare two different biological endotoxin assay kits: Lonza rFC and Associates of Cape Cod Pyrochrome Chromogenic, in order to detect any significant variation in measured endotoxin concentrations and potentially establish a conversion factor for interstudy comparison purposes. The LAL assay uses a component found in the blood of horseshoe crabs in order to detect and quantify endotoxin concentrations. This process poses some concern with variability, as the reactivity of lysate with endotoxin can vary greatly between individual horseshoe crabs. The newer rFC assay offers an additional option for endotoxin analysis that does not require the use of horseshoe crabs. Because all of the materials are produced in a laboratory, the consistency between kits is much higher. In Aim 1, PVC filters in replicates of five were liquid-spiked with 5 levels of known amounts of endotoxin. To simulate effects of sampling and handling, each filter was then desiccated for 24 hours and loaded into SKC Button Aerosol Samplers where air was pulled through them for 4 hours at a flowrate of 4 L/min to mimic field sampling conditions. Samples were then frozen at -80ºC, thawed, and extracted. Each sample was analyzed for endotoxins using the rFC assay. For Aim 2, a combination of personal, area, and field blanks were collected from two Colorado dairy farms from 2013-2014 in conjunction with a larger study for a total sample size of n=31. Samples were desiccated for 24 hours, frozen at -80ºC, thawed, and extracted. Each sample was then analyzed using the rFC and LAL assay and the results were compared. Using the rFC assay, measurements for endotoxin concentrations were on average several magnitudes lower than the anticipated concentration. Spike recoveries ranged from 1-8%. It is likely that the hydrophobic properties of the PVC filters did not allow complete absorption of the liquid spikes, but rather evaporated into the air. For aim 2, there was no statistical difference found between the rFC and LAL assay for the total sample set (p-value 0.7146) using an alpha=0.10. There was also no statistical difference between assay types for the personal sample subset (p-value 0.3788). However, there was a statistically significant difference for the area sample subset (p-value 0.0698) and the lab and field blank sample subset (p-value 0.06638). Due to the small sample size, the power had to be adjusted to accommodate an alpha value of 0.10. The correlation between observations for all samples was found to be reasonably high with an r value of 0.867. The R2 coefficient value was found to be 0.7524. This indicates that 75.24% of the variability in LAL assay data can be explained by rFC assay data. The rFC assay serial dilution of standards gives a much more broad detection range of 0.005-5.0 EU/ml. The LAL standards only cover a fraction of this range, going from 0.005-0.04 EU/ml, 0.02-0.16 EU/ml, and 0.16-1.28 EU/ml. This dramatically decreases the chances of correctly identifying the dilution factor on the first attempt, and can create additional costs to use extra kits for re-analysis. The rFC assay can also be a considerably more cost effective option when purchasing in bulk of 20-30 kits at a time; however, when purchased individually, the LAL assay is less expensive. Overall, the development of the rFC assay greatly reduces the amount of horseshoe crabs harvested and bled for collection, reduces the costs of formulating the lysate enzyme, and most significantly, reduces the inconsistency in endotoxin measurement results.
Open Access
A comparison of air samples at ground level and aerial gamma count rates from the response to the Fukushima Dai-Ichi Nuclear Power Plant accident
(Colorado State University. Libraries, 2014) Sublett, Sarah Miriam, author; Brandl, Alexander, advisor; Biedron, Sandra, committee member; Johnson, Thomas, committee member
March 11, 2011 will be a day that will never be forgotten in the minds of the thousands of Japanese people whose lives were forever changed by a series of natural disasters, including a 9.0 earthquake and subsequent tsunami that triggered the Fukushima Dai-Ichi Nuclear Power Plant (FDNPP), located on the eastern coast of Japan, to become cripplingly damaged. The FDNPP nuclear accident resulted in the emission of radionuclides into the environment and those released nuclides, specifically 134Cs, 137Cs, and 131I and their measurement by ground and air based means, are the subject of this research project. Within the first few days following the start of the disaster, numerous US federal agencies responded and deployed to Japan to help characterize and measure the release of radionuclides from FDNPP. Over the course of approximately a two-month span, over 500,000 measurements were obtained and analyzed, including air and soil samples and in situ spectra. The core of this research project was to analyze and compare ground air samples to aerial gamma count rate measurements obtained in Fukushima Prefecture within the first two months following the disaster. The results of this project estimate the ground deposition of radionuclides in Fukushima Prefecture, which accounted for 99.4% of the measured aerial net gamma count rate. Another finding of this project is the estimated ground deposition of nuclides based upon aerial gamma count rates in areas where there was measurable ground air contamination was 14.25 times higher than in areas where there was no measurable ground air contamination as determined by the evaluated air samples in this project. Of the samples evaluated in this project, ground deposition averaged 5.4E6 Bq/m2 in areas where there was measurable ground air contamination, versus 3.79E5 Bq/m2 in areas where there was no measurable ground air contamination.
Open Access
A comparison of methods to derive aggregated transfer factors: tested using wild boar data from the Fukushima prefecture
(Colorado State University. Libraries, 2017) Anderson, Donovan, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Hess, Ann, committee member
In March of 2011, the Fukushima Daiichi disaster released airborne radioactive material dominated by Cs-134 and Cs-137. When the radionuclides settled, they contaminated soil and plants, with wild boar also becoming contaminated through various pathways. An estimate of the radiocesium concentration in wild boar tissues can be obtained from an aggregated transfer factor based on soil contamination levels. The aggregated transfer factor (Tag) for purposes of this study, is the ratio of Cs-137 concentration in wild boar tissues (Bq kg-1) divided by the Cs-137 surface contamination of soils (Bq m-2). In this study, two methods were used to estimate the Tag values, and a comparison was made to determine which method reduced uncertainty. Both methods rely on harvesting and measuring radiocesium in wild boar tissues (bicep femoris muscle). The radiocesium value used for soil, however, was different in the two methods. One was obtained from a public database of samples collected by the Japanese government in 2015. Oftentimes, the soil sample paired with the wild boar trap site were not within the home range of the wild boar, reducing accuracy of the predicted radiocesium concentration levels in the animal. The other method used soil samples collected at the point of wild boar capture. The purpose of this study is to ascertain if the use of the database radiocesium soil concentration values is of sufficient granularity to provide a useful estimate of Tag values. The mean Tag value calculated in the Fukushima prefecture for wild boar were 2.3×10-3 m2 kg-1 fresh weight. The research revealed that the database radiocesium concentration values for soil (Bq m-2) used in calculating aggregated transfer factors, do not accurately represent the containment levels in the wild boar. Collecting soil samples within the home range of the animal reduces uncertainty in calculating Tag values to estimate whole body contamination levels of a wild boar. Our data complements and supports the existing monitoring programs conducted by the National and Prefecture governments in Japan by showing lower concentrations of cesium in soil and wild boar within decontaminated areas.
Open Access
A comparison of the use of sodium iodide and lanthanum bromide scintillation crystals for airborne surveys
(Colorado State University. Libraries, 2014) Bailey, Derek M., author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Milton, Stephen, committee member
The Environmental Protection Agency (EPA) Aerial Spectral Environmental Collection Technology (ASPECT) program performs aerial radiological and chemical characterization of geographical regions of interest. Airborne surveys are performed to characterize environmental radionuclide content, for mineral exploration, as well as for emergency scenarios such as major releases or lost sources. Two radiological detection systems are used by the ASPECT team for gamma-ray detection and characterization: lanthanum bromide [LaBr3(Ce)] and sodium iodide [NaI(Tl)] scintillation systems. An aerial survey of a uranium mine in the western United States was performed using both NaI(Tl) and LaBr3(Ce) detection systems. Analyses of the survey data were performed with RadAssist software and applying International Atomic Energy Agency (IAEA) airborne gamma ray mapping guidelines. The data for the survey were corrected for cross-over, which is spectral interference from higher energy photons as a result of Compton scattering, height attenuation, cosmic ray contribution to signal, and Radon contribution to signal. Two radiation survey contours were generated from each discrete data set. Based on analysis of the uranium mine survey results, LaBr3(Ce) produced a product comparable to that of NaI(Tl). The LaBr3(Ce) detection system contained 1/16th the scintillating volume and had a total system weight that was 1/4th that of the NaI(Tl) system. LaBr3(Ce) demonstrated a clear advantage over NaI(Tl) detectors in system mobility, and weight factors in airborne gamma ray spectroscopy.
Open Access
A comparison of wearable measurement systems for estimating trunk postures in manual material handling
(Colorado State University. Libraries, 2017) Arroyo Vera, Jose Gustavo, author; Rosecrance, John, advisor; Gilkey, David, committee member; Reiser, Raoul, committee member
Epidemiologic studies have established that awkward trunk postures during manual materials handling are associated with an increased risk of developing occupational low back disorders. With recent advances in motion capture technology, emerging wearable measurement systems have been designed to quantify trunk postures for exposure assessments. Wearable measurement systems integrate portable microelectromechanical sensors, real-time processing algorithms, and large memory capacity to effectively quantify trunk postures. Wearable measurement systems have been available primarily as research tools, but are now quickly becoming accessible to health and safety professionals for industrial application. Although some of these systems can be highly complex and deter health and safety professionals from using them, other systems can serve as a simpler, more user-friendly alternative. These simple wearable measurement systems are designed to be less intricate, allowing health and safety professionals to be more willing to utilize them in occupational posture assessments. Unfortunately, concerns regarding the comparability and agreement between simple and complex wearable measurement systems for estimating trunk postures are yet to be fully addressed. Furthermore, application of wearable measurement systems has been affected by the lack of adaptability of sensor placement to work around obstructive equipment and bulky gear workers often wear on the job. The aims of the present study were to 1) compare the Bioharness™3, a simple wearable measurement system, to Xsens™, a complex wearable measurement system, for estimating trunk postures during simulated manual material handling tasks and 2) to explore the effects of Xsens sensor placement on assessing trunk postures. Thirty participants wore the two systems simultaneously during simulated tasks in the laboratory that involved reaching, lifting, lowering, and pushing a load for ten minutes. Results indicated that the Bioharness 3 and Xsens systems are comparable for strictly estimating trunk postures that involved flexion and extension of 30° or less. Although limited to a short range of trunk postures, the Bioharness also exhibited moderate to strong agreement and correlations with the Xsens system for measuring key metrics commonly used in exposure assessments, including amplitude probability distribution functions and percent time spent in specific trunk posture categories or bins. The Bioharness is suggested to be an a more intuitive alternative to the Xsens system for posture analysis, but industrial use of the device should be warranted in the context of the exposure assessment goals. In addition, a single motion sensor from the Xsens system placed on the sternum yielded comparable and consistent estimates to a sensor secured on the sternum relative to a motion sensor on the sacrum. Estimates included descriptive measures of trunk flexion and extension and percent time spent in specific trunk posture categories. Using one motion sensor instead of two may serve as an alternative for sensor placement configuration in situations where worker portable equipment or personal preference prevents preferred sensor placement.
Open Access
A multimethod simulation paradigm for investigating complex cellular responses in biological systems of aging and disease
(Colorado State University. Libraries, 2019) Hoffman, Timothy Edward, author; Hanneman, William H., advisor; Legare, Marie E., advisor; Wallis, Lyle E., committee member; Moreno, Julie A., committee member
Classical studies in toxicology and disease research have relied on the use of high-dose experiments and often lacked quantitative and comprehensive components essential to understanding biological queries. These shortcomings in the research community have been the result of modern methodological limitations, however, more robust and expansive experimental and computational methods are emerging. In this dissertation, I present a novel multimethod computational simulation paradigm that adds value to new and existing studies of toxicological and pathological endeavors. First, I established the use of this approach for pharmacokinetic and pharmacodynamic applications, with published examples in regulatory exposure toxicology and contemporary dose-response nuances. Following establishing the success of this approach in toxicology, I then applied this methodology to the broader question of degenerative aging, as it has been arduous with conventional techniques to understand the various mechanisms that contribute to and protect against cellular aging. The foundational simulation created for general cellular aging was then expanded in the context of tauopathies and Alzheimer's disease to better quantify and understand the pathways involved in this age-dependent disorder. The final results presented here improve experimental translatability, robustness and descriptiveness in order to better understand age-related diseases. More broadly, this dissertation in totality attempts to minimize quantitative deficits in toxicological and pharmacological research.
Open Access
A net-risk approach to displacement and reoccupation decision making
(Colorado State University. Libraries, 2019) Braley, Gerald Scott, author; Johnson, Thomas E., advisor; Brandl, Alexander, committee member; Fisher, Gwen, committee member; Sudowe, Ralf, committee member
Decision makers and planners have a large body of information available concerning most aspects of a radiation disaster. International and national standards organizations, as well as national and local level policies and plans provide little guidance about the risks involved in relocating a population from a radiologically contaminated area. Populations displaced after all types of disasters have demonstrated poorer health outcomes, both physiological and psychological, than their non-displaced peers. These include a greater risk of diabetes and greater rates of post-traumatic stress disorder and depression when compared with other populations who experienced the disaster but were not relocated. Methodologies for population-level radiation dose prediction have improved, with recent data from contaminated areas in Japan providing real-world information about radiation doses. These improvements have not yet made their way into policies and guidance. The objective of this work is to quantify and incorporate multiple forms of risk, radiological and non-radiological, into a single model to improve decision making and minimize harm connected to displacement from and reoccupation of radiologically contaminated areas after a disaster.
Open Access
A novel method for rapid in vitro radiobioassay
(Colorado State University. Libraries, 2015) Crawford, Evan Bogert, author; Zimbrick, John, advisor; Hulpke, Alexander, committee member; LaRosa, Jerome, committee member; Ramsdell, Howard, committee member; Steinhauser, Georg, committee member
Rapid and accurate analysis of internal human exposure to radionuclides is essential to the effective triage and treatment of citizens who have possibly been exposed to radioactive materials in the environment. The two most likely scenarios in which a large number of citizens would be exposed are the detonation of a radiation dispersal device (RDD, "dirty bomb") or the accidental release of an isotope from an industrial source such as a radioisotopic thermal generator (RTG). In the event of the release and dispersion of radioactive materials into the environment in a large city, the entire population of the city - including all commuting workers and tourists - would have to be rapidly tested, both to satisfy the psychological needs of the citizens who were exposed to the mental trauma of a possible radiation dose, and to satisfy the immediate medical needs of those who received the highest doses and greatest levels of internal contamination - those who would best benefit from rapid, intensive medical care. In this research a prototype rapid screening method to screen urine samples for the presence of up to five isotopes, both individually and in a mixture, has been developed. The isotopes used to develop this method are Co-60, Sr-90, Cs-137, Pu-238, and Am-241. This method avoids time-intensive chemical separations via the preparation and counting of a single sample on multiple detectors, and analyzing the spectra for isotope-specific markers. A rapid liquid-liquid separation using an organic extractive scintillator can be used to help quantify the activity of the alpha-emitting isotopes. The method provides quantifiable results in less than five minutes for the activity of beta/gamma-emitting isotopes when present in the sample at the intervention level as defined by the Centers for Disease Control and Prevention (CDC), and quantifiable results for the activity levels of alpha-emitting isotopes present at their respective intervention levels in approximately 30 minutes of sample preparation and counting time. Radiation detector spectra - e.g. those from high-purity germanium (HPGe) gamma detectors and liquid scintillation detectors - which contain decay signals from multiple isotopes often have overlapping signals: the counts from one isotope's decay can appear in energy channels associated with another isotope's decay, complicating the calculation of each isotope's activity. The uncertainties associated with analyzing these spectra have been traced in order to determine the effects of one isotope's count rate on the sensitivity and uncertainty associated with each other isotope. The method that was developed takes advantage of activated carbon filtration to eliminate quenching effects and to make the liquid scintillation spectra from different urine samples comparable. The method uses pulse-shape analysis to reduce the interference from beta emitters in the liquid scintillation spectrum and improve the minimum detectable activity (MDA) and minimum quantifiable activity (MQA) for alpha emitters. The method uses an HPGe detector to quantify the activity of gamma emitters, and subtract their isotopes' contributions to the liquid scintillation spectra via a calibration factor, such that the pure beta and pure alpha emitters can be identified and quantified from the resulting liquid scintillation spectra. Finally, the method optionally uses extractive scintillators to rapidly separate the alpha emitters from the beta emitters when the activity from the beta emitters is too great to detect or quantify the activity from the alpha emitters without such a separation. The method is able to detect and quantify all five isotopes, with uncertainties and biases usually in the 10-40% range, depending upon the isotopic mixtures and the activity ratios between each of the isotopes.
Open Access
A study of fumed silica particle deagglomeration associated with instrument sampling techniques and A comparison of NIOSH 7402 and the Tsai Diffusion Sampler for collecting and analyzing carbon nanotubes
(Colorado State University. Libraries, 2018) Khattak, Jared, author; Tsai, Candace Su-Jung, advisor; Reynolds, Stephen, committee member; Jathar, Shantanu, committee member
Accurate characterization of contaminant exposures is critical in ensuring worker safety. Worker exposures are commonly characterized by area monitoring and personal samples. This research includes two parts, which study real time instrument measurements and personal sampling methods for exposure assessment. Real time instruments (RTIs) are used to assess concentrations of airborne particles in manufacturing facilities. These instruments often contain a cyclone, and previous studies have shown that the cyclone may cause measurement variations by dispersing agglomerated particles. This mechanism is thought to increase particle concentrations and decrease particle size. To determine the cyclone effect in this study, three RTIs were evaluated; the scanning mobility particle sizer (SMPS), fast mobility particle sizer (FMPS), and the optical particle sizer (OPS). The SMPS and FMPS contain a cyclone, the OPS does not. Nanoparticles were generated and sampled through pouring and automatic stirring inside a glovebox enclosure. After particles were generated, the glovebox was thoroughly cleaned and measurements were taken in the glovebox. For both generation methods, the SMPS and FMPS recorded an average concentration of 1.2 x 103 particles/cm3 and 1.7 x 104 particles/cm3 more after runs where the cyclone was used than when the cyclone was not used. The OPS, which does not contain a cyclone, recorded minimal differences during the measurement period after the glovebox was cleaned when the cyclone was used and not used on the other instruments. This result indicated that the measured nanoparticle concentrations increased with cyclone use. The results of this study indicate that the cyclone does influence the concentrations recorded by RTIs, and should be cleaned to ensure accurate measurements. The personal sampling methods evaluated were the NIOSH 7402 method for collecting and analyzing Carbon Nanotubes (CNTs) and the Tsai Diffusion Sampler (TDS) method for sampling CNTs. To evaluate each sampling method, CNTs were generated in a small enclosure inside of a glovebox; CNTs were generated by manual stirring. RTIs also sampled during each experiment to provide an estimate of airborne CNT concentrations. Airborne concentrations were estimated using the particle counts from TEM grid samples prepared using both methods. The majority of CNT structures collected by the TDS were individual fibers and clusters smaller than one micron in diameter. The NIOSH 7402 sampler primarily collected larger agglomerates, with the majority of collected particles being larger than two microns in diameter. The average estimated airborne concentrations calculated from the TDS and 7402 method particle counting were 5,200 fibers/cm3 and 59 fibers/cm3 respectively. During the experiments the SMPS recorded an airborne concentration of 1,100 particles/cm3 and the OPS measured an airborne concentration of 33 particles/cm3. Because the concentrations measured by the RTIs significantly exceeded the estimated concentrations derived from the NIOSH 7402 method, it is recommended that the TDS sampler be used as the concentrations derived from this sampler would warrant a more conservative approach to worker safety.
Open Access
A yeast-based assay system for the study of environmentally induced copy number variation
(Colorado State University. Libraries, 2012) Stanton, Jacquelyn Lee, author; Argueso, Juan Lucas, advisor; Legare, Marie, committee member; Stargell, Laurie, committee member
Multiple studies have shown that in different individuals, specific genomic segments can occur at a variable copy number relative to the reference human genome. Chromosomal rearrangements resulting in Copy Number Variations (CNVs) have long been recognized as contributing factors in carcinogenesis, and more recently in Autism Spectrum Disorders. The molecular mechanisms underlying the formation of CNVs are not completely understood. The goal of this research project was to complete the development of an assay system to study CNV, and to validate it as a tool to investigate the relationship between environmental exposures and CNV formation. We have optimized a CNV detection assay using the budding yeast Saccharomyces cerevisiae as an experimental model system. This CNV reporter contains two yeast genes, SFA1 and CUP1 that confer gene dosage-dependent tolerance to formaldehyde and copper, respectively. This system enables the detection of rare clones containing an amplification of the chromosomal segment containing the reporter by selection in media containing high levels of formaldehyde and copper, allowing the estimation of the rate of CNV formation. Results obtained in diploid cells under basal growth conditions (un-induced / un-exposed) showed that most spontaneous CNV events detected in our system were mediated through non-allelic homologous recombination (NAHR) between dispersed repetitive DNA sequences, mainly Ty1 and Ty2 retrotransposable elements and their LTRs. Another set of repeats involved in NAHR included conserved gene family. Single copy sequences and microhomology motifs were detected in our dataset, but were exceedingly rare. The most abundant classes of CNVs observed involved segmental duplications and non-reciprocal translocations. In order to characterize the effect of environmental factors on CNV, cells were exposed to relatively low doses of three different known mutagens: Hydroxyurea, Methyl Methanesulfonate, and Camptothecin. These exposures resulted in an increase of the CNV rate ranging from 3 to 17 fold over the un-induced cultures. The spectra of chromosomal rearrangements induced by these exposures was analyzed, revealing that not only did exposures result in more chromosomal breaks but often a higher frequency of resulting segmental copies, and allowing further understanding of the CNV mechanisms associated with these exposures.
Open Access
Active radiation detectors for use in space beyond low earth orbit: spatial and energy resolution requirements and methods for heavy ion charge classification
(Colorado State University. Libraries, 2017) McBeth, Rafe A., author; Borak, Thomas, advisor; Brandl, Alexander, committee member; Ray, Andrew, committee member; Homrighausen, Darren, committee member
Space radiation exposure to astronauts will need to be carefully monitored on future missions beyond low earth orbit. NASA has proposed an updated radiation risk framework that takes into account a significant amount of radiobiological and heavy ion track structure information. These models require active radiation detection systems to measure the energy and ion charge Z. However, current radiation detection systems cannot meet these demands. The aim of this study was to investigate several topics that will help next generation detection systems meet the NASA objectives. Specifically, this work investigates the required spatial resolution to avoid coincident events in a detector, the effects of energy straggling and conversion of dose from silicon to water, and methods for ion identification (Z) using machine learning. The main results of this dissertation are as follows: 1. Spatial resolution on the order of 0.1 cm is required for active space radiation detectors to have high confidence in identifying individual particles, i.e., to eliminate coincident events. 2. Energy resolution of a detector system will be limited by energy straggling effects and the conversion of dose in silicon to dose in biological tissue (water). 3. Machine learning methods show strong promise for identification of ion charge (Z) with simple detector designs.
Open Access
Acute and chronic cobalt toxicity in Dugesia dorotocephala
(Colorado State University. Libraries, 2011) Sternenberger, Andrea, author; Ramsdell, Howard, advisor; Legare, Marie, committee member; Strauss, Steven, committee member
Limited data are available regarding cobalt toxicity for water quality criteria and risk assessment evaluation for freshwater organisms. These experiments were performed to establish median lethal concentrations from short term studies and to identify the most sensitive sublethal effect in a long term study in a flatworm species, Dugesia dorotocephala. Another study was conducted to elucidate the relationship between calcium, magnesium and cobalt toxicity in D. dorotocephala. During 4 and 7 day studies, median lethal concentrations of cobalt increased with total hardness indicating a protective effect. Calcium was shown to be more protective than magnesium in the presence of cobalt. A 60 day study showed fissioning rate, a process essential for maintenance of the D. dorotocephala population, to be the most sensitive endpoint. A lowest observable adverse effect concentration (LOAEC) of 1 mg Co/L (nominal) was incorporated into the calculation of an acute to chronic ratio (ACR), an important metric for risk analysis accounting for sublethal effects that may occur by mechanisms different from lethal ones. A NOAEC (no observable adverse effect concentration) was not determined because significant effects were observed at the lowest cobalt concentrations tested (<1 mg Co/L). Without an exact NOAEC, the ACR values established in this study represent the upper and lower bounds of the acute to chronic ratio for cobalt in D. dorotocephala.
Open Access
Adult onset male hypogonadism: diagnosis and treatment
(Colorado State University. Libraries, 2022) Akagi Bath, Natalie, author; Legare, Marie, advisor; Dooley, Greg, committee member; Moreno, Julie, committee member; Nickoloff, Jac, committee member; Popichak, Katriana, committee member
Hypogonadism affects an estimated 2–4 million American men with increasing prevalence seen in older men. Normal aging processes lead to decreased biological production of testosterone. However, levels below physiologic function can decrease the quality of life and the life expectancy of men. A clinical diagnosis of hypogonadism, results from this failure to produce testosterone and or normal amounts of sperm and is more commonly referred to as low-Testosterone (low-T). Pharmacologic intervention with exogenous testosterone, hormone replacement therapy, can improve quality of life. However, this intervention is not without risks and should only be done when serum testosterone is below 300 ng/ml and is accompanied with symptoms associated with low testosterone. The aims of this work are to report the most commonly-used clinical symptoms associated with low-T for diagnosis, to provide a list of risks associated with hormone replacement therapy, and to analyze the different forms of pharmacologic intervention known commonly as Testosterone Replacement Therapy (TRT).
Open Access
AI for personalized medicine
(Colorado State University. Libraries, 2023) Lewis, Aidan Michael, author; Bailey, Susan M., advisor; LaRocca, Tom J., committee member; Nishimura, Erin O., committee member
In 2021, Americans spent an estimated $4.3 trillion dollars on healthcare, an extraordinary amount for treatment that is often less effective than care in other developed nations (1-3). Precision, or personalized, medicine represents a new frontier in healthcare that promises treatment plans and optimized health strategies tailored to an individual (4) thereby making medicine more effective and less costly. Contemporary Artificial Intelligence (AI) and Machine Learning (ML) approaches have tremendous potential to advance the field of precision medicine by leveraging the technology's power of deciphering patterns in the data to make predictions about an individual's health outcomes (3, 5-8). However, many developing AI/ML approaches to precision medicine have not proven particularly successful in making accurate predictions and conclusions mostly due to the limited availability of high-quality medical data for input. The Wake Forrest University Non-Human Primate Radiation Late Effects Cohort (NHP RLEC) provides an unprecedented opportunity to test AI's ability to be trained on a comprehensive human health analog data set in an experimentally irradiated Rhesus monkey cohort with extraordinary life-time records of biomarker levels and health outcomes. Here, we test prevalent, scalable ML models to improve accuracy of predictions specifically related to radiation biomarkers, dose, and health outcomes. We find that CatBoost, ElasticNet, and XGBoost models can accurately predict lymphocyte counts for both monkey populations and individual monkeys. Furthermore, these models can accurately predict radiation dose and biomarker levels using only five other features within the models. Although the models were only marginally successful at predicting lymphocyte counts using radiation-related data alone, and at predicting the health outcomes of the monkeys, these findings and this unique dataset represent key steps toward refining the combinations of factors necessary for the successful use of AI/ML models in precision medicine for humans.
Open Access
Air toxic assessment for short-term ambient air pilot study at private house in Battlement Mesa near oil and gas drilling site
(Colorado State University. Libraries, 2011) Alhaji, Hussain, author; Reynolds, Stephen J., advisor; Brazile, William Joseph, committee member; Kreidenweis, Sonia M., committee member
This pilot study evaluated the ambient air concentrations in Battlement Mesa, Colorado at private house near a well pad, for the four-day period of February 7 through February 10 of 2011. The natural gas site was operating in the production phase of oil and gas development process, and there were 12 wells commercial line. The overlying purpose of the study was to provide preliminary evaluation of air quality characteristics within Battlement Mesa with particular attention to Speciated Non-Methane Organic Compounds/Volatile Organic Compounds (SNMOC/VOCs), fine particulate matter (PM2.5) and total volatile organic compounds (TVOC's). SNMOCs including benzene, toluene, ethylbenezene, and xylene (BTEX) compounds were collected and analyzed using a modified EPA Organic Compendium Method TO-12 over a 22-hour period using Summa-polished stainless steel canisters. PM2.5 levels were measured using a directing reading photometer, a Personal Data RAM (pDR-1200) for 24-hour sampling period. Total VOCs, were measured in real-time using a Rae Systems PPB Rae 3000 photo ionization detector (PID). To measure the meteorological data, a portable weather station was deployed at the fire station site (FR) during the sampling period (about half mile from the sampling location). Sampling was performed at two locations around the private house, and background samples were collected at the FR for each parameter. The large percentage of detection (high prevalence i.e. ~95%) in samples from all sites appears to indicate that local VOCs sources do have impacts on air pollution levels. Compounds that were detected in the highest concentrations were light alkanes (i.e. ethane, propane) and the BTEX group (benzene, toluene, ethylbenzene and xylenes). The BTEX group, benzene in particular, recorded a potential health risk compared to the Risk Based Concentration (RBC) developed by the Environmental Protection Agency (EPA). In general, the SNMOCs/VOCs levels detected were low for all samples. TVOCs levels were also low and are consistent with the BTEX group where the background site recoded higher levels than the sampling sites (Upstream "UP" and Downstream "DN" sites). No exceedances of Federal National Ambient Air Quality Standards were recorded for PM2.5. In addition, PM2.5 concentrations were generally highest in the UP site which is close to the well pad. Comparisons of PM2.5 data to data from other studies in Garfield County show that PM2.5 concentrations in Battlement Mesa (oil and gas development area) are similar to or higher than the Rifle area (urban area) Meteorological monitoring was performed on a continuous basis with one-hour averages being generated. Wind speed and precipitation (snow) are the most pronounced meteorological parameters that are correlated with VOCs and PM2.5 levels. Overall for the study, pollutant levels were found to be generally very low as compared to the standards and suggested guidelines. In some locations, it is likely that more elevated pollutant levels are the result of local or individual sources. BTEX emissions sources should be evaluated more thoroughly and benzene in particular since elevated levels were observed. Given that benzene recorded a potential health hazard in the area (exceeded lower level for cancer risk), it is recommended that a comprehensive air study that measures VOCs at different seasons and at other well-development processes be conducted. The background site (FR) is affected by several emission sources. Therefore, it is recommended to relocate the background site to have a better representative background. A direct reading photometer method using the Personal Data RAM (pDR1200) is not the best method to collect the particulates during the winter season due to instrument related temperature bias. Therefore, an alternative method to measure the particulate matter is advised.
Open Access
Alteration of differentiation and growth of normal human epidermal keratinocytes by benzo[a]pyrene and arsenic
(Colorado State University. Libraries, 2005) Perez, Damon Scott, author; Campain, Julie, advisor; Yang, Raymond Shih-hsien, 1940-, advisor; Legare, Marie E., committee member; Fox, Michael, committee member; Ranu, Rajinder S., committee member
Normal human epidermal keratinocytes (NHEK) were chosen as an in vitro model for mechanistic studies into how altered regulation of differentiation may play a role in the malignant transformation process in human cells. Initially, the cytotoxicity of four petroleum-derived hydrocarbons [benzo[a]pyrene (BaP), carbazole, dibenzothiophene, and isoquinoline] was investigated using the MTT assay; however, the research direction changed to focusing on examining the cellular effects, in NHEK, of BaP, the most toxic and carcinogenic polycyclic aromatic hydrocarbon among the four, and arsenic, another high priority skin carcinogen. This work demonstrates that BaP and arsenic inhibit terminal differentiation in NHEK. Arsenic also decreases proliferation in a manner suggestive of a G2 block. In contrast, BaP increases proliferation rates and induces rapid progression through the cell cycle, possibly by a shortened G2 phase. Differentiation is more sensitive to chemically-mediated perturbations than is proliferation, indicating that the former process may be the initial target at environmentally prevalent concentrations. To identify molecular alterations that are responsible for the observed chemical-specific effects, microarray analysis was carried out on NHEK treated with each carcinogen. From this analysis, BaP and arsenic altered 103 and 122 genes respectively. More sensitive real-time PCR revealed that BaP-treatment perturbed the expression of genes involved in cellular differentiation and growth. Altered genes include; α-integrin binding protein-63, interleukin-1α, interleukin-1β, Ras guanyl releasing protein-1, retinoic acid- and interferon-inducible protein, and YY1-associated factor-2. Arsenic altered the expression of genes involved in cell cycle checkpoint regulation. These genes include; MAX binding protein, RAD50, retinoblastoma-1, retinoblastoma-binding protein-1, and transforming growth factor β-stimulated protein. Gene expression results suggest that BaP and arsenic target different steps in the pathways to growth and differentiation in this cell type and provide mechanistic clues as to how these chemicals favor transformation in target cells. Moreover, a quantitative biologically-based computer model of NHEK was developed providing an in silico experimental platform with which one can test chemical-mediated effects on cell cycle kinetics and differentiation. A clearer understanding of cellular growth and differentiation, both from a normal standpoint and from alterations induced by chemical exposure, will greatly aid the risk assessment process for environmental contaminants.
Open Access
An epidemiologic evaluation of risk factors associated with asthma severity and phenotypes
(Colorado State University. Libraries, 2008) Busacker, Ashley A., author; Keefe, Thomas J., advisor
Asthma is an inflammatory disorder of the airways characterized by airway hyperresponsiveness, periodic episodes of bronchoconstriction and airway obstruction. Severe asthma accounts for a minority of asthma, but utilizes a disproportionate amount of asthma-associated healthcare costs. Further studies are needed to identify risk factors associated with severe asthma, a very heterogeneous disease. Asthma-particularly severe asthma-consists of several different phenotypes. Limited epidemiologic studies have been conducted to identify risk factors specific to severe asthma. Factors associated with proposed asthma phenotypes have not been evaluated in a multivariate manner. This study investigated the risk factors associated with severe asthma, with specific phenotypes of asthma, and the association between a potential biomarker, C-reactive protein (CRP), and aspirin intolerant asthma. The project utilized data that were collected from National Institutes of Health funded studies and data collected from an electronic chart review. Data from questionnaires, histological, radiological and physiological studies were used to determine univariate associations between these factors and asthma severity and then to determine associations between the factors and different asthma phenotypes. Multiple logistic regression analysis was used to evaluate the differences between severe and non-severe asthma, early and late onset asthma, asthma subjects who did or did not exhibit air trapping, and aspirin intolerant and tolerant asthma with particular attention to CRP levels. This investigation found important clinical differences between severe and non-severe asthma that should be further evaluated as risk factors that may give insight into severe-asthma mechanisms to be targeted in asthma treatment. The analysis of asthma phenotypes also yielded important findings. Specifically, early onset asthmatics appear to be a relatively homogeneous group with strong genetic influences and presence of allergic responses, whereas late onset disease is more heterogeneous. The analysis of the air trapping phenotype demonstrated that quantitative CT-determined air trapping in asthmatic subjects identifies a group of individuals with a increased odds of intensive health care utilization. Additionally, several independent risk factors for the presence of this phenotype were identified, perhaps most interestingly history of pneumonia, neutrophilic inflammation, and atopy. Lastly, this study provides evidence that CRP may be elevated in aspirin intolerant subjects and that CRP deserves further study as a potential biomarker for the aspirin intolerant phenotype of asthma.
Open Access
An evaluation of the collection characteristics and usability factors of three nanoparticle samplers
(Colorado State University. Libraries, 2017) Castano, Andrew, author; Tsai, Candace Su-Jung, advisor; Brazile, William, committee member; Clegg, Benjamin, committee member
Occupational exposure to nanoparticles is a concern to occupational hygienists because of the potential health effects of exposure, the lack of standardized sampling methods and regulatory guidance for exposure limits. Exposure assessments for nanoparticles should include analysis of particles with an electron microscope to allow for identification of particle size, shape and composition. This study is the first to use multiple aerosols to compare the particle size fractions collected by three handheld nanoparticle samplers designed to use transmission electron microscope grids for particle collection. These include the Tsai diffusion sampler (TDS), electrostatic precipitator (ESP), and thermophoretic personal sampler (TPS). Aerosols of sodium chloride, ISO fine test dust, and aluminum oxide were tested and the particle size fractions collected by the nanoparticle samplers were compared. The TDS collected more particles in a wider size range for the lowest concentration aerosol. The ESP sampled for much shorter than the others but collected the most particles for two out of three aerosols. The usability questionnaire assessed all steps involved in sampler usage and rated the features of each device. The TDS and TPS were best suited for full shift sampling and the ESP best for short term. The TDS was the most affordable and has the potential to collect larger particles on a secondary filter. Overall, the TPS was the easiest device to use. Study results indicated that all samplers successfully collected three types of aerosols, with smaller differences in the size fractions they collected and larger differences in the number of particles per surface area of their collection media.