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Aging Is a Determinant in Anoxia Stress Tolerance in Caenorhabditis Elegans (open access)

Aging Is a Determinant in Anoxia Stress Tolerance in Caenorhabditis Elegans

Oxygen availability is critical for survival for most organisms. The nematode, C. elegans, has been useful for studying genetic regulation of anoxia tolerance due to the oxygen deprivation response mechanisms shared with other metazoans. Studies examining long-term anoxia (72h, LTA) tolerance have only been conducted at adult day 1. To investigate the effect of aging on anoxia tolerance wild-type and mutant strains were exposed to LTA between adult day 1 and day 9. Wild-type isolates and daf-16(mu86) (FOXO transcription factor regulated by insulin-signaling) and aak-2(gt33) (catalytic subunit of AMP-activated protein kinase) strains were anoxia sensitive at day 1 and displayed increased LTA tolerance with aging correlated with reproductive senescence followed by a decline in survivorhsip through day 9. The daf-2(e1370) (insulin receptor homologue of C. elegans), glp-1(e2141) (a lin-12/Notch receptor) and fog-2(q71) (required for spermatogenesis) strains were LTA-tolerant through day 5. I conclude that aging influences LTA-tolerance in a strain- and age-dependent manner. In addition to being LTA-tolerant the daf-2(e1370) and glp-1(e2141) strains have a longevity phenotype that is suppressed by loss of kri-1 or daf-12. While loss of kri-1 did not suppress the LTA-tolerant phenotype of glp-1(e2141) at day 1 the portion of impaired survivors increased at day 3 …
Date: May 2013
Creator: Goy, Jo M.
System: The UNT Digital Library
Bioconcentration and Morphological Effects of Triclosan on Three Species of Wetland Plants (open access)

Bioconcentration and Morphological Effects of Triclosan on Three Species of Wetland Plants

Triclosan (TCS) is an antimicrobial compound found in several types of common household products. After being washed down the drain, TCS will then end up in the local watershed. Although numerous studies have been conducted to evaluate the fate and effects of TCS in aquatic environments, there have been no studies evaluating the role arbuscular mycorrhizal fungi (AM) play in a plants response to TCS exposure. Three species of wetland plants native North Texas were inoculated with AM spores and exposed to 0, 0.4 g/L and 4.0 g/L TCS concentrations. Root morphology of E. prostrata and S. herbacea showed AM and exposure responses. S. herbacea produced the greatest amounts biomass and TCS bioaccumulation, in all but one treatment. It also displayed opposing results to E. prostrata in measures of root length, root surface area, relative root mass, relative shoot mass and shoot:root ratio. TCS root tissue concentrations increased with increased exposures for both E. prostrata and S. herbacea. Even though E. prostrata had the lowest levels in each measure of biomass production, it had the highest amount of root TCS bioaccumulation in the AM inoculated 4.0 g/L treatment. H. laevis was between the other two species in terms of biomass …
Date: May 2013
Creator: Smith, Caleb M.
System: The UNT Digital Library
Evaluating the Habitat Requirements of the Golden Orb Mussel (Quadrula Aurea) for Conservation Purposes (open access)

Evaluating the Habitat Requirements of the Golden Orb Mussel (Quadrula Aurea) for Conservation Purposes

Many freshwater mussels are imperiled, due to a number of interrelated factors such as habitat alteration, degradation of water quality, and impoundments. The Golden Orb mussel (Quadrula aurea, I. Lea, 1859) is endemic to the state of Texas and is currently a candidate for the endangered species list, as the number of known populations has been declining in recent years. Little is currently known about Q. aurea aside from basic distribution data. This study is focused on evaluating a combination of macro-habitat and micro-habitat variables to determine their influence on the distribution and density of this species. Macro-habitat variables, including dominant land cover, surface geology, and soil erodibility factor, did not have a significant relationship with mussel distributions. The best model of micro-habitat variables that impacts the Q. aurea distributions is comprised of relative substrate stability (RSS) at moderate flows and current velocity at low flows. For all mussel species in this study, current velocity at low flows is the primary variable that influences distribution. Q. aurea are associated with habitats where larger sediment particles (large gravel and cobble) help to stabilize the substrate in areas with higher current velocities. An understanding of the preferred habitats for Q. aurea can …
Date: May 2013
Creator: Hammontree, Sarah
System: The UNT Digital Library
Examination of the Relationship Between Glucuronic Acid and Vascular Damage in Rats (open access)

Examination of the Relationship Between Glucuronic Acid and Vascular Damage in Rats

The goal of this experiment was to examine the role of glucuronic acid in the development of vascular damage in the kidneys and retinas of diabetic individuals. Glucuronic acid was provided to rats in their water at various concentrations in order to increase plasma levels of the compound. Kidneys and retinas were excised and compared to control specimens using microscopy to determine the effect of elevated blood glucuronic acid levels on the occurrence of microaneurysms in renal capillary networks. No differences were seen between the treatment and control groups. Further study needs to be conducted to determine a more suitable time frame for this experiment.
Date: May 2013
Creator: Moore, Ryan
System: The UNT Digital Library
Exploring the Evolutionary History of North American Prairie Grouse (Genus: Tympanuchus) Using Multi-locus Coalescent Analyses (open access)

Exploring the Evolutionary History of North American Prairie Grouse (Genus: Tympanuchus) Using Multi-locus Coalescent Analyses

Conservation biologists are increasingly using phylogenetics as a tool to understand evolutionary relationships and taxonomic classification. The taxonomy of North American prairie grouse (sharp-tailed grouse, T. phasianellus; lesser prairie-chicken, T. pallidicinctus; greater prairie-chicken, T. cupido; including multiple subspecies) has been designated based on physical characteristics, geography, and behavior. However, previous studies have been inconclusive in determining the evolutionary history of prairie grouse based on genetic data. Therefore, additional research investigating the evolutionary history of prairie grouse is warranted. In this study, ten loci (including mitochondrial, autosomal, and Z-linked markers) were sequenced across multiple populations of prairie grouse, and both traditional and coalescent-based phylogenetic analyses were used to address the evolutionary history of this genus. Results from this study indicate that North American prairie grouse diverged in the last 200,000 years, with species-level taxa forming well-supported monophyletic clades in species tree analyses. With these results, managers of the critically endangered Attwater's prairie-chicken (T. c. attwateri) can better evaluate whether outcrossing Attwater's with greater prairie-chickens would be a viable management tool for Attwater's conservation.
Date: May 2013
Creator: Galla, Stephanie J.
System: The UNT Digital Library
Genetic Interest Assessment (open access)

Genetic Interest Assessment

Genetics is becoming increasingly integrated into peoples' lives. Different measures have been taken to try and better genetics education. This thesis examined undergraduate students at the University of North Texas not majoring in the life sciences interest in genetic concepts through the means of a Likert style survey. ANOVA analysis showed there was variation amongst the interest level in different genetic concepts. In addition age and lecture were also analyzed as contributing factors to students' interest. Both age and lecture were evaluated to see if they contributed to the interest of students in genetic concepts and neither showed statistical significance. The Genetic Interest Assessment (GIA) serves to help mediate the gap between genetic curriculum and students' interest.
Date: May 2013
Creator: Doughney, Erin
System: The UNT Digital Library
Primary Cilia in the Oligodendrocyte Lineage (open access)

Primary Cilia in the Oligodendrocyte Lineage

oligodendrocytes migrate from the corpus callosum into the overlying cortex. The incidence of cilia did not change markedly across age groups, and did not vary consistently with the number of processes per cell, which was used as an indication of the maturation stage of OPCs and young OLs. The mean percent of Olig1 immunopositive (Olig1+) cells having cilia across ages was 33.1% + 16.5%, with all ages combined. In O4+ cells of these mice, 56.7 + 3.6% had primary cilia. If it is the case that adult OLs do not have cilia, the point in the lineage when primary cilia are lost is still unknown. Adult mice that had been injected with cyclopamine to block cilia-dependent Shh signaling were examined to determine whether the rate of generating new OPCs was influenced. In the CC of control mice, the numerical density of Olig1+/BrdU+ cells was 1.29 + 0.07/mm2 was reduced to 0.68 + 0.38/mm2 in the cyclopamine-injected group, and the numerical density of all BrdU+ cells (including both Olig1+ and Olig1- cells) of 4.55 + 1.50/mm2 in the control group was reduced to 3.14 + 1.27/mm2 in the cyclopamine-injected group. However, there were only 2 mice in each group and the …
Date: May 2013
Creator: Hao, Yung-Chia
System: The UNT Digital Library
Developing a Collection Digitization Workflow for the Elm Fork Natural Heritage Museum (open access)

Developing a Collection Digitization Workflow for the Elm Fork Natural Heritage Museum

Natural history collections house immense amounts of data, but the majority of data is only accessible by locating the collection label, which is usually attached to the physical specimen. This method of data retrieval is time consuming and can be very damaging to fragile specimens. Digitizing the collections is the one way to reduce the time and potential damage related to finding the collection objects. The Elm Fork Natural Heritage Museum is a natural history museum located at the University of North Texas and contains collections of both vertebrate and invertebrate taxa, as well as plants. This project designed a collection digitization workflow for Elm Fork by working through digitizing the Benjamin B. Harris Herbarium. The collection was cataloged in Specify 6, a database program designed for natural history collection management. By working through one of the museum’s collections, the project was able to identify and address challenges related to digitizing the museum’s holdings in order to create robust workflows. The project also produced a series of documents explaining common processes in Specify and a data management plan.
Date: August 2013
Creator: Evans, Colleen R.
System: The UNT Digital Library
Endocrine Disruption of Levonorgestrel in Early-life Stages of Fathead Minnows, Pimephales Promelas (open access)

Endocrine Disruption of Levonorgestrel in Early-life Stages of Fathead Minnows, Pimephales Promelas

Pharmaceuticals have routinely been detected in the environment resulting in a growing concern about whether these drugs could elicit effects on aquatic organisms. The concerns are centered on the highly conserved nature of mammalian therapeutic targets in fish. These pharmaceuticals are found at very low levels in the environment, which can result in sub-lethal effects in aquatic organisms. Therefore, 28 d early-life stage studies were conducted on six pharmaceuticals to assess their impacts on survival and growth fathead minnow larvae. Two pharmaceuticals tested, carbamazepine and fenofibrate, resulted in no alterations to survival and growth. However, amiodarone, clozapine, dexamethasone, and levonorgestrel (LNG) reduced survival at concentrations tested with LNG being the most potent at 462 ng/L. Survival was increased with amiodarone and clozapine; however LNG significantly decreased growth at 86 ng/L. Therefore, the most potent pharmaceutical tested was the synthetic progestin LNG with survival and growth impacts at concentrations less than 1 μg/L. Further analysis was conducted by measuring specific endocrine related mRNA transcript profiles in FHM larvae following the 28 d ELS exposure to LNG. Transcripts of 3β-HSD, 20β-HSD, and FSH were significantly down-regulated following 28 d exposure to both 16.3 and 86.9 ng/L LNG. Also, CYP19a expression was significantly …
Date: August 2013
Creator: Overturf, Matthew D.
System: The UNT Digital Library
The Effect of Menthol on Nicotine Metabolism:  a Cross Species Evaluation (open access)

The Effect of Menthol on Nicotine Metabolism: a Cross Species Evaluation

The effect of menthol on nicotine metabolism was examined in liver S9 fractions of four different species and in the in vivo mouse model. The purpose of this study was to investigate three parameters: (1) biotransformation of nicotine to cotinine in various species (human, mouse, rat and trout) using in vitro methods; (2) to determine if the addition of menthol with nicotine altered biotransformation of nicotine to cotinine; (3) and to assess similar parameters in an in vivo mouse model. The major findings of this study include: (1) mice appear to metabolize nicotine, over time, in a manner similar to humans; (2) menthol decreased cotinine production, over time, after a single dose in mice; and (3) menthol increased cotinine production, over time, after repeated doses, in mice.
Date: December 2013
Creator: Pace, Wendy Lee
System: The UNT Digital Library
Effects of Airway Pressure, Hypercapnia, and Hypoxia on Pulmonary Vagal Afferents in the Alligator (Alligator Misssissippiensis) (open access)

Effects of Airway Pressure, Hypercapnia, and Hypoxia on Pulmonary Vagal Afferents in the Alligator (Alligator Misssissippiensis)

The American alligator (Alligator mississippiensis) is an aquatic diving reptile with a periodic breathing pattern. Previous work has identified pulmonary stretch receptors (PSR), both rapidly- and slowly-adapting, and intrapulmonary chemoreceptors (IPCs) that modulate breathing patterns in alligators. The purpose of the present study was to identify the effects of prolonged lung inflation and deflation (simulated dives) on PSR and/or IPC firing characteristics in the alligator. The effects of airway pressure, hypercapnia, and hypoxia on dynamic and static responses of pulmonary stretch receptors (PSR) were studied in juvenile alligators (mean mass = 246 g) at 24°C. Receptor activity appeared to be a mixture of slowly-adapting PSRs (SARs) and rapidly-adapting PSRs (RARs) with varying thresholds and degrees of adaptation, but no CO2 sensitivity. Dives were simulated in order to character receptor activity before, during, and after prolonged periods of lung inflation and deflation. Some stretch receptors showed a change in dynamic response, exhibiting inhibition for several breaths after 1 min of lung inflation, but were unaffected by prolonged deflation. For SAR, the post-dive inhibition was inhibited by CO2 and hypoxia alone. These airway stretch receptors may be involved in recovery of breathing patterns and lung volume during pre- and post-diving behavior and …
Date: December 2013
Creator: Marschand, Rachel E.
System: The UNT Digital Library
Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone (open access)

Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone

The goals of this dissertation work were to assess the bioaccumulation potential of carbamazepine and amiodarone, two widely used ionizable pharmaceutical compounds that possess mid-range and high LogD values, respectively, and to evaluate alternative methods to assess chemical accumulation in bluntnose minnows, catfish, and tilapia. Results indicated that carbamazepine does not appreciably bioaccumulate in fish tissue with BCFk and BAF carbamazepine values < 10. Amiodarone, however, with a log D of 5.87 at pH 7.4, accumulated in fish tissues with kinetic BCF values <2,400. Collectively, the data suggest that full and abbreviated laboratory-derived BCFs, BCFMs derived from S9 loss-of-parent assays, as well as field BAF values are similar for each of the two drugs. In summary, the results from this dissertation indicated: 1) The reduced design BCF test is a good estimate for the traditional OECD 305 test. 2) In vitro S9 metabolism assays provide comparable BCF estimates to the OECD 305 test. 3) Metabolism may play a large role in the accumulation of drugs in fish. 4) Reduced BCF tests and in vitro assays are cost effective and can reduce vertebrate testing.
Date: December 2013
Creator: García Martínez, Santos Noé
System: The UNT Digital Library
Immunohistochemistry of the Gills of the Channel Catfish Ictalurus Punctatus: Cells and Neurochemicals That May Be Involved in the Control of Cardioventilatory Reflexes (open access)

Immunohistochemistry of the Gills of the Channel Catfish Ictalurus Punctatus: Cells and Neurochemicals That May Be Involved in the Control of Cardioventilatory Reflexes

In teleost fishes the neurochemicals involved in sensing and responding to hypoxia are unresolved. Serotonergic branchial neuroepithelial cells (NECs) are putative O2 chemoreceptors believed to be homologous to the neural crest (NC) derived APUD (amine-precursor uptake and decarboxylation) pulmonary NECs and carotid body type-1 glomus cells. Branchial NECs contain serotonin (5-HT), thought to be central to the induction of the hypoxic cardioventilatory reflexes. However, application of 5-HT in vivo does not elicit cardioventilatory reflexes similar to those elicited by hypoxia. But previous in vitro neural recordings from glossopharyngeal (IX) afferents innervating O2 chemoreceptors in the trout gill show the same discharge response to hypoxic conditions as does that of acetylcholine (ACh) application. This evidence strongly supports the cholinergic hypothesis of chemoreceptor impulse origin rather than a serotonergic-induced impulse origin model. We therefore hypothesized that NECs contain ACh among other neurochemicals in cells belonging to the APUD series. Although serotonergic branchial NECs did not colocalize with ACh using immunohistochemical methods, several populations of ACh and/or tyrosine hydroxylase (TH) (catecholaminergic) positive, dopamine (DA) negative, cells were found throughout the second gill arch of the channel catfish Ictalurus punctatus. In addition, the NC derivation marker zn-12 labelled the HNK-1-like epitope (Human natural killer) …
Date: December 2013
Creator: Oden, David S.
System: The UNT Digital Library
Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna (open access)

Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna

Titanium dioxide nanoparticles (TiO2-NP) are one of the most abundantly utilized nanomaterials in the world. Studies have demonstrated the mechanism of acute toxicity in TiO2-NP to be the production of reactive oxygen species (ROS) leading to oxidative stress and mortality in exposed organisms. It has also been demonstrated that the anatase crystalline conformation is capable of catalyzing the cleavage of water molecules to further increase the concentration of ROS in the presence of ultraviolet radiation. This photoenhanced toxicity significantly lowers the toxicity threshold of TiO2-NP to environmentally relevant concentrations (ppb). The goal of this study was to determine whether dietary uptake and accumulation of TiO2-NP in the aquatic filter feeder Daphnia magna resulted in photoenhanced toxicity. D. magna and S. caprincornatum were exposed to aqueous solutions of 20ppm and 200ppm TiO2-NP for 24hrs and then transferred to clean moderately hard water. Samples were taken at various time points, dried, and TiO2 quantified using ICP-MS. Toxicity assays were run on D. magna using three TiO2-NP (20ppm, 200ppm) exposure protocols and two ultraviolet radiation treatments. The first exposure group was exposed to aqueous solutions of TiO2-NP for the duration of the test. The second exposure group was exposed to TiO2-NP for an …
Date: December 2013
Creator: Mansfield, Charles M.
System: The UNT Digital Library
Relationships of Benthic Macroinvertebrate Community Structure with Land-use, Habitat, In-stream Water Chemistry, Depositional Sediment Biofilm Fatty Acids, and Surfactants in the Effluent Dominated Texas Trinity River (open access)

Relationships of Benthic Macroinvertebrate Community Structure with Land-use, Habitat, In-stream Water Chemistry, Depositional Sediment Biofilm Fatty Acids, and Surfactants in the Effluent Dominated Texas Trinity River

The Trinity River is an urbanized, effluent-dominated river, and is heavily relied upon for drinking water. The benthic macroinvertebrate community has been monitored for over 20 years, with the focus of this dissertation on three studies (1987-88, 2005, and 2011). Water quality improvement following dechlorination resulted in increased benthic metrics. Overall habitat quality, in-stream cover, surface water total organic carbon, sediment total organic carbon, near-field urban land-use, near-field forested land-use, surface water surfactant toxic units, and depositional sediment biofilm fatty acids all have statistically significant relationships with benthic macroinvertebrate metrics. These relationships are better defined with increased taxonomic resolution at the genus/species level for all benthic taxa, including Chironomidae and Oligochaeta. It is recommend that benthic identifications for state and city water quality assessments be done at the genus/species level. A novel method for quantifying depositional sediment biofilm fatty acids has been produced and tested in this dissertation. Benthic metrics are directly related to fatty acid profiles, with several essential fatty acids found only at upstream sites.
Date: December 2013
Creator: Slye, Jaime L.
System: The UNT Digital Library
Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio (open access)

Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio

Bioconcentration factor testing serves as the most valuable surrogate for the assessment of bioaccumulation. The assessment of potentially harmful chemicals is crucial to not only the health of aquatic environments, but to humans as well. Chemicals that possess the ability to persist in the environment or that have the potential to bioaccumulate, pose a greater risk to organisms that are exposed to these chemicals. The Organization for Economic Cooperation and Development Guideline 305 outlines specific protocols to run an accurate and reliable aquatic flow-through test. However, since its adoption in 1996, very few changes have been made to accommodate the endeavor to lowering the amount of test species to run one of these said tests. Running an aquatic flow-through test, according to 305, takes much time and money as well as numerous amounts of fish. Such burdens can be eliminated through simple modifications to the standard protocols. In this study, we propose an abbreviated study design for aquatic bioconcentration testing which effectively alleviates the burdens of running a flow-through test. Four chemicals were used individually to evaluate the usefulness of the proposed shortened design; 4-Nonyphenol, Chlorpyrifos, Musk Xylene, and DDT. The study consisted of exposing Cyprinus carpio for 7 days …
Date: December 2013
Creator: Cantu, Mark
System: The UNT Digital Library