Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Deon van der Merwe / 1,4-Dioxane is a potentially carcinogenic solvent. It is a problematic groundwater contaminant because of its unique physical-chemical properties. It is found in a wide range of consumer products as a by-product contaminant. This research aimed to investigate contaminant properties and behavior of dioxane in the environment and also in the human body. The dioxane ability to decontamination by adsorption processes was evaluated with four adsorbents. The adsorption efficiencies of activated carbon (AC), metal oxide nanomaterials (TiO[subscript]2 and MgO), and diatomaceous earth (DE) were assessed in aqueous and vapor phases using infrared spectroscopy. AC showed the highest adsorptive capacity for dioxane at equilibrium in both phases. The rate and extent of dermal absorption are important in the analysis of risk from dermal exposure to dioxane. For this purpose, a new flow through diffusion system (FTDS) was developed by modifying a Bronaugh flow through diffusion cell with flow capacity in both the donor and receptor compartments and using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) as the analytical technique. FTDS can provide ‘real time’ quantitative high-density permeation data over time and is characterized by the simplicity of its use and the low cost of test samples. The in vitro dermal absorption study of dioxane across human skin showed that the absorption parameters of dioxane were 1.16 ± 0.22 hr, 5.7 X 10[superscript]-4 ± (0.62) cm/hr, 0.286 ± 0.035 mg/cm2/hr, 4.8 X 10-5 (± 0.32) cm[superscript]2/hr, and 1.99 ± 0.086 mg for lag time, permeability, steady-state flux, diffusivity, and total amount absorbed over 8 hr, respectively. The study of the effect of the surfactant sodium lauryl sulphate and solvent systems water, ethanol, propylene glycol, and ethyl acetate on permeation profiles revealed that these solvents and surfactants increased the permeation of dioxane significantly. The FT-IR spectra of stratum corneum treated with solvents showed that there was broadening of the CH[subscript]2 asymmetric stretching vibration of the CH[subscript]2 peak near 2920 cm[superscript]-1 only in samples treated with ethanol. The lipid extract precipitates were detected and were mostly composed of the stratum corneum lipid part.

Master of Science / Department of Chemical Engineering / Larry E. Erickson / The damage that can be inflicted by ultraviolet radiation has gained widespread interest. Traditionally sunscreens are made of organic and inorganic components that block two of the three types of ultraviolet radiation, UVA and UVB. This report is a literature review of several articles that have investigated the effects of inorganic UV filters; specifically titanium dioxide and cerium dioxide. There are concerns about absorption of titanium dioxide into the skin and the adverse reactions that could occur, but it was found that there is little to no absorption. Similarly the photostability of titanium dioxide is a concern; this was found to be remedied in part by a surface treatment to the titanium dioxide. The combination of titanium dioxide and carnauba wax was also studied and found to enhance the properties of both the organic and inorganic filters. Ceria was studied as a possible replacement for titanium dioxide. It was found to have similar ultraviolet shielding properties while minimizing the photocatalytic activity and photocytotoxicity seen in titanium dioxide.

Master of Science / Department of Entomology / Kun Yan Zhu / Cytochrome P450 monooxygenases (P450s) are important enzymes involved in the metabolism of a variety of xenobiotics, including insecticides and plant allelochemicals, and endogenous compounds, including juvenile hormones, ecdysteroids and fatty acids, in insects. Despite rapid advances in revealing various P450 genes in insects, our knowledge on the role of these genes in detoxification of insecticides is very limited. This research was to perform a genome-wide analysis of P450 genes and evaluate the role of selected P450 genes in detoxification of three commonly used pyrethroid insecticides in the yellow fever mosquito (Aedes aegypti). Our genome-wide analysis of revealed 159 P450 genes that can be classified into 18 families and 63 subfamilies. These genes are distributed in four clans, including 11 genes in the CYP2 clan, 80 in the CYP3 clan, 58 in the CYP4 clan and 10 in the mitochondrial CYP clan. The largest families are CYP6, CYP9, CYP4 and CYP325. The intron-exon organization of the genes is very diverse among the gene families, and the highest conservation of gene structures was observed in the CYP6 and CYP9 families predominantly containing single-intron genes. The phylogenetic analysis suggested that the CYP6 and CYP9 families might be derived from a common ancestor. The expression patterns of five transcripts including three individual genes (CYP6AA5, CYP6AL1 and CYP9J32) and two alternative splicing variants (CYP4J16A and CYP4J16B) of CYP4J16 were investigated in various tissues and at different developmental stages of the mosquito. Our results indicated differential expressions of these transcripts in different tissues and at different developmental stages examined. Furthermore, the exposure of the mosquitoes (larvae and adults) to each of three pyrethroid insecticides (permethrin, cypermethrin and deltamethrin) resulted in either down or up-regulation of these transcripts. Functional analyses of the selected P450 transcripts were conducted by using RNA interference (RNAi) followed by insecticide bioassay. RNAi was achieved by feeding mosquito larvae with chitosan/double stranded RNA (dsRNA) nanoparticles or injecting dsRNA to the adults. For the larvae, we obtained relatively low repressions of the P450 transcripts but the repressions were sufficient for carrying out our functional studies. Our study showed increased mortalities by 41.2% to cypermethrin when CYP6AA5 was silenced and 46.0% to permethrin when CYP9J32 was silenced. Similarly, the injection of dsRNAs in adults resulted in significant repressions of the P450 transcripts, and subsequent insecticide exposures led to a 29.3% increase in the adult mortality to cypermethrin when CYP6AA5 was silenced. Our further analysis of the nuclear receptor HR96 in the up-regulation of the P450 genes showed that when HR96 was silenced by RNAi, the up-regulation of CYP4J16B by cypermethrin was reduced by 10.1-fold but silencing HR96 did not affect the up-regulation of other P450 genes examined. These results suggest that HR96 is likely involved in regulating the expression of CYP4J16B in Ae. aegypti. However, different regulatory mechanism (s) may be involved in the up-regulation of other P450 genes examined. Model structure of CYP6AA5 was created by homology modeling and insecticides substrates were docked into the active site of this protein. Our results indicate that all three insecticides can fit into the catalytic pocket. The interaction distances between the heme iron and the putative aromatic hydroxylation site were 9.2, 9.4 and 7.2 Å for permethrin, cypermethrin and deltamethrin, respectively, whereas for aliphatic hydroxylation site these distances were 5.3, 2.8 and 2.9 Å. These results showed that CYP6AA5 may be able to metabolize cypermethrin and deltamethrin preferentially by aliphatic hydroxylation as indicated by the close interaction with the heme iron.

Master of Veterinary Bioscience / Department of Diagnostic Medicine/Pathobiology / Deon Van Der Merwe / Every year thousands of domestic animals are poisoned by ethylene glycol. Exposure is normally orally, but may be dermal, and poisonings are usually accidental and not malicious. Antifreeze, overwhelmingly the source of the ethylene glycol poisoning, is responsible for over 99% of reported cases. Storage, handling and proper disposal of ethylene glycol is extremely important in limiting access to this deadly product. Ethylene glycol exposures were involved in 1737 calls made to the American Society for the Prevention of Cruelty to Animals call center between 2006 and 2011. Dogs were involved in approximately 87% of exposures and cats in 13%. There were no seasonal or breed patterns. The most common clinical signs reported were neurological and gastrointestinal for both cats and dogs. Urinary calcium oxalate crystals were reported in 28.6% of exposed cats, and 21% of dogs. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to detect calcium oxalate crystals in wax-mounted kidneys from twenty total cases, ten of which were suspected ethylene glycol poisoning submitted to the Kansas State Veterinary Diagnostic Laboratory, and ten samples deemed negative by a pathologist using light microscopy. Pure calcium oxalate monohydrate was used as a reference, and a unique absorption peak was detected between wavenumbers 1290 cm[superscript]-1 and 1320 cm[superscript]-1. The drying of kidney tissues resulted in increased sensitivity for calcium oxalate. Crystal detection by the ATR-FTIR was compared to light microscopy. Bi-fringence of crystals allowed microscopic detection, but the ATR-FTIR specificity for the test was 100%, and sensitivity was 80% compared to traditional microscopy for ca-oxalate crystal identification. ATR-FTIR was also used to detect un-metabolized ethylene glycol in vomitus using wavenumbers 1084 cm[superscript]−1, 1039 cm[superscript]−1, and 882 cm[superscript]−1, but ethylene glycol was not detectable. Ethylene glycol concentrations in samples were much too low to be detected as ethylene glycol on the ATR-FTIR, as the limit of detection was not distinguishable until 5000 ppm using a serial dilution. These methods presented simple, reliable, quick, sensitive, stable, and highly adaptable tests for detection, diagnosis and treatment of ethylene glycol poisoning.

Master of Science / Department of Entomology / Frank H. Arthur / Kun Yan Zhu / Experiments were conducted to assess the effects of direct and indirect exposure scenarios, different degrees of residual flour, open and obstructed positions, and seasonal temperature variations on the efficacy of synergized pyrethrin against the red flour beetle, Tribolium castaneum (Herbst) and the confused flour beetle, Tribolium confusum Jacquelin du Val. To evaluate effects of direct and indirect exposures of T. castaneum and T. confusum eggs, larvae, pupae, or eggs to the insecticide aerosol within a flour mill, the following treatments were made to each life stage: insects treated with aerosol and transferred to treated or untreated flour, untreated insects transferred to treated flour, and insects and flour combined and treated together. Different degrees of harborage or sanitation levels were created by exposing T. confusum larvae, pupae, and adults to pyrethrin aerosol in Petri dishes containing 0, 0.1, 1, 5, and 10 g of wheat flour. Effects of pyrethrin dispersal in open and obstructed positions and seasonal temperature variations were assessed by exposing T. confusum pupae and adults in open positions and inside wooden boxes (1 m long, 20 cm wide, and 5, 10, or 20 cm high) inside experimental sheds maintained at target temperatures of 22, 27, and 32 °C. Results showed that when T. castaneum and T. confusum were directly exposed to aerosol without the flour source, or with a low amount of flour at open exposed areas, the aerosol provided good control against all life stages of T. castaneum and T. confusum. However, when insects were indirectly exposed (treated together with flour or untreated insects were transferred to treated flour), or treated together with deeper flour amounts, and exposed inside the boxes, the efficacy was greatly reduced. Eggs and pupae of both the species were more susceptible compared to larvae and adults. Additionally, the moribund adults initially observed in indirect exposure treatments, or at the deeper flour depth and exposure positions insides the boxes, were better able to recover. Generally, temperatures in the range of 22-32 °C had no significant effects on overall efficacy of pyrethrin aerosol.

Master of Science / Department of Animal Sciences and Industry / KC Olson / Condensed tannins (CT) in plants are phenolic compounds with relatively high binding affinities for proteins. In ruminants, dietary CT limit DM intake and digestibility, and ruminal protein degradation by forming CT-protein complexes. Effects of dietary CT, animal species, prior dietary CT exposure, and antimicrobial inclusion on 48-h rate and extent of digestion were measured in two in vitro experiments. Cattle, sheep, and goats (n = 3 / species) were used in a 2-period, randomized complete-block experiment with a 2 × 3 × 2 × 3 factorial arrangement of treatments. Factor 1 was substrate: tannin-free or high-CT. Factor 2 was source of ruminal fluid inoculum: cattle, sheep, or goat. Factor 3 was prior animal exposure to a high-CT diet: non-exposed or exposed. Factor 4 was inclusion of antimicrobials: no antimicrobial, penicillin + streptomycin to suppress bacterial activity, or cycloheximide to suppress fungal activity in the fermentation. Tannin-free or high-CT substrates were incubated in vitro using ruminal fluid from animals either not exposed (period 1) or exposed to dietary CT (period 2). Periods consisted of an adaptation to tannin-free (10 d) or high-CT diets (21 d) and a 15-d period of ruminal-fluid collection via stomach tube. The presence of CT or penicillin + streptomycin in in vitro fermentation reduced (P < 0.001) total gas pressure, DM disappearance, and total VFA, acetate, propionate, butyrate, valerate, and branched-chain VFA concentrations. We concluded that: 1) CT had negative effects on fermentation, 2) prior exposure to dietary CT attenuated some but not all negative effects, and 3) CT effects were similar to the effects of penicillin + streptomycin.

Master of Science / Department of Chemical Engineering / Larry E. Erickson / Polycarbonate products have been used extensively world wide for decades because they are lightweight, shatter-resistant and considered to be safe. Polycarbonate is a thermoplastic that is used to make compact discs, phones, lenses, and food contact products such as water bottles, baby bottles and food storage containers. For more than half century, there has been interest in polycarbonate (PC) products and the monomer bisphenol-A (BPA) because BPA can leach from food polycarbonate containers. The environmental fate for both chemicals in air, water and soil is of interest, also. To understand the fate of polycarbonate, its main degradation pathways, main degradation mechanisms and main products are reviewed. These pathways are thermal degradation, photo-degradation and hydrolysis under different conditions. Furthermore, key topics like PC degradation kinetics and PC chemical resistance are part of this comprehensive discussion. The biodegradation of BPA has been thoroughly studied. About twelve lab methods for environmental fate are summarized and reviewed to understand the “big picture” for BPA degradation. This includes screening tests, which assess the ready and inherent degradability, to simulation tests for surface waters, soils and wastewater treatment systems. The testing of all methods is examined under conditions close to the real environment fate. Furthermore, the fate distribution for BPA based on the Equilibrium Criterion Model (EQC) model is reviewed. Extensive research on polycarbonate and BPA has been conducted in the last fifty years. During this time, both chemicals have been studied and tested by industry and government agencies. The pharmacological test results from major studies indicate that consumer exposure to BPA at concentrations normally experienced in daily living does not pose a risk to human health. On the other hand, minor toxicological studies indicate potential risks to human health. Research on health and safety are continuing.