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 Department: Department of Biological Sciences
 Collection: UNT Theses and Dissertations
Optimization of Novel Culturing and Testing Procedures for Acute Effects on Acartia Tonsa and Tisbe Biminiensis

Optimization of Novel Culturing and Testing Procedures for Acute Effects on Acartia Tonsa and Tisbe Biminiensis

Date: December 2014
Creator: Ussery, Erin J.
Description: Copepods comprise an ecologically important role in freshwater and marine ecosystems, which is why they are often considered an important ecotoxicological model organism. The International Organization for Standardization’s (ISO) 14669 protocol is the only guideline for the determination of acute toxicity in three European marine copepod species: Acartia tonsa. The goal of this project was to assess the feasibility of establishing and maintaining cultures of Acartia tonsa, as well as to refine current culturing and egg separation methods. Initial culture methodology proved difficult for consistent production of eggs and collection of nauplii. The development of an airlift system for the separation of eggs from nauplii and adults, based on size, successfully increased the availability of eggs, nauplii and adults. The sensitivity and relative conditions of the copepod species was assessed by running a series of 48h acute toxicity tests with the reference toxicants 3,5-dichlorophenol, 4,4’-methylenebis(2,6-di-tert-butylphenol. The acute 48 hour median lethal dose concentration (LC50), the no observed effect concentration (NOEC), and the lowest observed effect concentration (LOEC) was analyzed for the three reference compounds for of A. tonsa.
Contributing Partner: UNT Libraries
brk1 and dcd1 Act Synergistically in Subsidiary Cell Formation in Zea mays

brk1 and dcd1 Act Synergistically in Subsidiary Cell Formation in Zea mays

Date: August 2014
Creator: Malhotra, Divya
Description: Subsidiary mother cell (SMC) divisions during stomatal complex formation in Zea mays are asymmetric generating a small subsidiary cell (SC) and a larger epidermal cell. Mutants with a high number of abnormally shaped subsidiary cells include the brick1 (brk1) and discordia1 (dcd1) mutants. BRK1 is homologous to HSPC300, an ARP2/3 complex activator, and is involved in actin nucleation while DCD1 is a regulatory subunit of the PP2A phosphatase needed for microtubule generation (Frank and Smith, 2002; Wright et al. 2009). Possible causes of the abnormal SCs in brk1 mutants include a failure of the SMC nucleus to polarize in advance of mitosis, no actin patch, and transverse and/or no PPBs (Gallagher and Smith, 2000; Panteris et al 2006). The abnormal subsidiary mother cell division in dcd1 is due to correctly localized, but disorganized preprophase bands (PPBs; Wright et al. 2009). The observation that brk1 has defects in PPB formation and that the dcd1 phenotype is enhanced by the application of actin inhibitors led us to examine the dcd1; brk1 double mutant (Gallagher and Smith, 1999). We found that dcd1; brk1 double mutants demonstrate a higher percentage of aberrant SCs than the single mutants combined suggesting that these two mutations have ...
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Cloacal Microbiota of Captive-bred and Wild Attwater’s Prairie-chicken, Tympanuchus Cupido Attwateri

Cloacal Microbiota of Captive-bred and Wild Attwater’s Prairie-chicken, Tympanuchus Cupido Attwateri

Date: August 2014
Creator: Simon, Stephanie E.
Description: The Attwater’s prairie-chicken (Tympanuchus cupido attwateri; APC) is a species of grouse native to Texas coastal prairies and is on the critically endangered species list as a result of habitat destruction and overhunting. All of the current populations were captively bred and released into the wild. Survivorship for released APCs is very low, and individuals seldom survive to reproduce in the wild. One factor contributing to this may be an alteration in the gut microbiota as a result of captivity. Factors potentially influencing the gut microbial composition in captivity include antibiotic therapy, stress, and a predominantly commercially formulated diet. Recent studies have begun to shed light on the importance of the host microbial endosymbionts. Antibiotic administration, stress, diet, age, genotype and other factors have been shown to influence microbial populations in the gastrointestinal tracts of many different vertebrates. Sequencing of 16S rRNA gene amplicons on the Ion Torrent™ platform was used in this study to identify groups of bacteria in the cloacas as a surrogate for the gut microbiota in the APC. Antibiotic-treated and untreated birds, wild-hatched and captive-bred birds, and individuals sampled before and after release to the wild were examined. Significant differences were found between wild-hatched and captive ...
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Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index

Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index

Date: August 2014
Creator: Goetz, Heinrich
Description: A method was developed for extending a fine-scaled forest gap model to a watershed-scaled landscape, using the Eastern Cross Timbers ecoregion as a case study for the method. A topographic wetness index calculated from digital elevation data was used as a measure of hydrologic across the modeled landscape, and the gap model modified to have with a topographically-based hydrologic input parameter. The model was parameterized by terrain type units that were defined using combinations of USDA soil series and classes of the topographic wetness index. A number of issues regarding the sources, grid resolutions, and processing methods of the digital elevation data are addressed in this application of the topographic wetness index. Three different grid sizes, 5, 10, and 29 meter, from both LiDAR-derived and contour-derived elevation grids were used, and the grids were processed using both single-directional flow algorithm and bi-directional flow algorithm. The result of these different grids were compared and analyzed in context of their application in defining terrain types for the forest gap model. Refinements were made in the timescale of gap model’s weather model, converting it into a daily weather generator, in order to incorporate the effects of the new topographic/hydrologic input parameter. The precipitation ...
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The Effects of Inbreeding on Fitness Traits in the Critically Endangered Attwater’s Prairie-chicken

The Effects of Inbreeding on Fitness Traits in the Critically Endangered Attwater’s Prairie-chicken

Date: August 2014
Creator: Hammerly, Susan C.
Description: The goals of captive breeding programs for endangered species include preserving genetic diversity and avoiding inbreeding. Typically this is accomplished by minimizing population mean kinship; however, this approach becomes less effective when errors in the pedigree exist and may result in inbreeding depression, or reduced survival. Here, both pedigree- and DNA-based methods were used to assess inbreeding depression in the critically endangered Attwater’s prairie-chicken (Tympanuchus cupido attwateri). Less variation in the pedigree-based inbreeding coefficients and parental relatedness values were observed compared to DNA-based measures suggesting that errors exist in the pedigree. Further, chicks identified with high parental DNA-based relatedness exhibited decreased survival at both 14- and 50-days post-hatch. A similar pattern was observed in later life stages (> 50 days post-hatch) with birds released to the wild; however, the pattern varied depending on the time post-release. While DNA-based inbreeding coefficient was positively correlated with mortality to one month post-release, an opposite pattern was observed at nine months suggesting purging of deleterious alleles. I also investigated whether immunocompetence, or the ability to produce a normal immune response, was correlated with survival; however, no significant correlation was observed suggesting that inbreeding was a more important factor influencing survival. Pairing individuals for breeding ...
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Engineered Microbial Consortium for the Efficient Conversion of Biomass to Biofuels

Engineered Microbial Consortium for the Efficient Conversion of Biomass to Biofuels

Date: August 2014
Creator: Anieto, Ugochukwu Obiakornobi
Description: Current energy and environmental challenges are driving the use of cellulosic materials for biofuel production. A major obstacle in this pursuit is poor ethanol tolerance among cellulolytic Clostridium species. The first objective of this work was to establish a potential upper boundary of ethanol tolerance for the cellulosome itself. The hydrolytic function of crude cellulosome extracts from C. cellulolyticum on carboxymethyl cellulose (CMC) with 0, 5, 10, 15, 20 and 25% (v/v) ethanol was determined. Results indicated that the endoglucanase activity of the cellulosome incubated in 5% and 10% ethanol was significantly different from a control without ethanol addition. Furthermore a significant difference was observed in endoglucanase activity for cellulosome incubated in 5%, 10%, 15%, 20% and 25% ethanol in a standalone experiment. Endoglucanase activity continued to be observed for up to 25% ethanol, indicating that cellulosome function in ethanol will not be an impediment to future efforts towards engineering increasing production titers to levels at least as high as the current physiological limits of the most tolerant ethanologenic microbes. The second objective of this work was to study bioethanol production by a microbial co-culture involving Clostridium cellulolyticum and a recombinant Zymomonas mobilis engineered for the utilization of oligodextrans. The ...
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Investigation of Strategies for Improving STR Typing of Degraded and Low Copy DNA from Human Skeletal Remains and Bloodstains

Investigation of Strategies for Improving STR Typing of Degraded and Low Copy DNA from Human Skeletal Remains and Bloodstains

Date: August 2014
Creator: Ambers, Angie D.
Description: Forensic STR analysis is limited by the quality and quantity of DNA. Significant damage or alteration to the molecular structure of DNA by depurination, crosslinking, base modification, and strand breakage can impact typing success. Two methods that could potentially improve STR typing of challenged samples were explored: an in vitro DNA repair assay (PreCR™ Repair Mix) and whole genome amplification. Results with the repair assay showed trends of improved performance of STR profiling of bleach-damaged DNA. However, the repair assay did not improve DNA profiles from environmentally-damaged bloodstains or bone, and in some cases resulted in lower RFU values for STR alleles. The extensive spectrum of DNA damage and myriad combinations of lesions that can be present in forensic samples appears to pose a challenge for the in vitro PreCR™ assay. The data suggest that the use of PreCR™ in casework should be considered with caution due to the assay’s varied results. As an alternative to repair, whole genome amplification (WGA) was pursued. The DOP-PCR method was selected for WGA because of initial primer design and greater efficacy for amplifying degraded samples. Several modifications of the original DOP-PCR primer were evaluated. These modifications allowed for an overall more robust amplification ...
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Regulation of Alternative Sigma Factors During Oxidative and Ph Stresses in the Phototroph Rhodopseudomonas Palustris

Regulation of Alternative Sigma Factors During Oxidative and Ph Stresses in the Phototroph Rhodopseudomonas Palustris

Date: August 2014
Creator: Perry, Leslie M.
Description: Rhodopseudomonas palustris is a metabolically versatile phototrophic α-proteobacterium. The organism experiences a wide range of stresses in its environment and during metabolism. The oxidative an pH stresses of four ECF (extracytoplasmic function) σ-factors are investigated. Three of these, σ0550, σ1813, and σ1819 show responses to light-generated singlet oxygen and respiration-generated superoxide reactive oxygen species (ROS). The EcfG homolog, σ4225, shows a high response to superoxide and acid stress. Two proteins, one containing the EcfG regulatory sequence, and an alternative exported catalase, KatE, are presented to be regulated by σ4225. Transcripts of both genes show similar responses to oxidative stress compared to σ4225, indicating it is the EcfG-like σ-factor homolog and controls the global stress response in R. palustris.
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The Role of the Actin Cytoskeleton in Asymmetric Cell Division in Maize

The Role of the Actin Cytoskeleton in Asymmetric Cell Division in Maize

Date: August 2014
Creator: Alhassan, Hassan Hamdan
Description: Stomata are specialized plant structures required for gaseous exchange with the outer environment. During stomata formation, the cytoskeleton plays an important role in controlling the division of the individual cells leading to the generation of the stomata complex. Two mutants that affect microfilament and microtubule organization in subsidiary mother cells include brk1 and dcd1. While only 20% of the subsidiary cells in the brk1 and dcd1 single mutants are abnormally shaped, it was reported that there is a synergistic effect between the brk1 and dcd1 mutations in the brk1; dcd1 double mutant since 100% of the subsidiary cells are abnormal. The focus of this research is to try to understand this synergistic effect by investigating the actin cytoskeleton and nuclear position in the single and double mutants. The reported results include the observation that the size of actin patch was largest in the wild-type subsidiary mother cells (SMCs) and smallest in dcd1 and brk1; dcd1 SMCs and that brk1 and brk1; dcd1 double mutants had fewer actin patches than wild-type and dcd1 SMCs. Additionally, we observed that some SMCs that did not have actin patches still underwent nuclear migration suggesting that nuclear migration may not be solely dependent on actin ...
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Women Have Higher Skin Temperature on the Back during Treadmill Exercise in a Hot, Humid Environment

Women Have Higher Skin Temperature on the Back during Treadmill Exercise in a Hot, Humid Environment

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Date: August 2014
Creator: Venable, Adam Steven
Description: A common measurement of body temperature during exercise in a hot, humid environment is mean skin temperature collected from 3-12 sites on the body. However, such an approach fails to demonstrate localized differences in skin temperature that are likely to exist as a function of gender. The purpose of this study was to examine potential differences in skin temperature between men and women at 17 different locations on the body. Young women (21 ± 1 y; n = 11) and men (23 ± 3; n = 10) were recruited to complete a 60-min walk/jog interval protocol in a hot (34 ± 1 °C), humid (64 ± 8%) environment while skin temperature was measured. Data was analyzed using a repeated-measures ANOVA (p < 0.05) and location of interaction effects determined using a Fisher’s least squares difference test. We observed a higher change (p < 0.05) from baseline skin temperatures (ΔTsk) for women in three locations: left upper back (women: avg. ΔTsk = 4.12 ± 0.20 °C; men: avg. ΔTsk = 2.70 ± 0.10 °C), right upper back (women: avg. ΔTsk = 4.19 ± 0.07 °C; men: avg. ΔTsk = 2.92 ± 0.05 °C), and right mid-back (women: avg. ΔTsk = 4.62 ...
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The Effect of Natural Gas Well Setback Distance on Drillable Land in the City of Denton, Texas

The Effect of Natural Gas Well Setback Distance on Drillable Land in the City of Denton, Texas

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Date: May 2014
Creator: Daniel, Michael
Description: Municipalities protect human health and environmental resources from impacts of urban natural gas drilling through setback distances; the regulation of distances between well sites and residences, freshwater wells, and other protected uses. Setback distances have increased over time, having the potential to alter the amount and geographical distribution of drillable land within a municipality, thereby having implications for future land use planning and increasing the potential for future incompatible land uses. This study geographically applies a range of setback distances to protected uses and freshwater wells in the city limits of Denton, Texas to investigate the effect on the amount of land remaining for future gas well development and production. Denton lies on the edge of a productive region of the Barnett Shale geological formation, coinciding with a large concentration of drillable land in the southwestern region of the study area. This region will have the greatest potential for impacts to future municipal development and land use planning as a result of future gas well development and higher setback standards. Given the relatively high acreage of drillable land in industrially zoned subcategory IC-G and the concern regarding gas well drilling in more populated areas, future drilling in IC-G, specifically in ...
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Designing Tools to Probe the Calcium-dependent Function of Arabidopsis Tonneau2

Designing Tools to Probe the Calcium-dependent Function of Arabidopsis Tonneau2

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Date: December 2013
Creator: Oremade, Oladapo O.
Description: Plants possess unique features in many aspects of development. One of these features is seen in cell wall placement during cytokinesis, which is determined by the position of the preprophase band (PPB) and the subsequent expansion of the phragmoplast that deposits the new cell wall. During phragmoplast expansion, the phragmoplast tracks to the cortical division site, which was delineated by the PPB. Thus the position of the PPB determines the orientation of the division plane. In Arabidopsis thaliana, TONNEAU2 (TON2) is required for PPB formation and has been shown to interact with a type A subunit of the PP2A phosphatase in the yeast two-hybrid system. In Arabidopsis tonneau2 (ton2) mutants, abnormalities of the cortical microtubule cytoskeleton, such as disorganization of the interphase microtubule array and lack of PPB formation before mitosis markedly affects cell shape and arrangement as well as overall plant morphology. Loss of dcd1/add1, the maize ton2 homologues gives rise to a similar phenotype in Zea mays. The TON2 protein has two EF hand domains which are calcium-binding sites. Since calcium has been known to play key roles in several areas of plant functioning, the following question was raised: “Does calcium binding contribute to the localization and function ...
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The Effect of Menthol on Nicotine Metabolism:  a Cross Species Evaluation

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

Date: December 2013
Creator: Pace, Wendy Lee
Description: 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.
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Effects of Airway Pressure, Hypercapnia, and Hypoxia on Pulmonary Vagal Afferents in the Alligator (Alligator Misssissippiensis)

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

Date: December 2013
Creator: Marschand, Rachel E.
Description: 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 ...
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Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone

Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone

Date: December 2013
Creator: García Martínez, Santos Noé
Description: 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.
Contributing Partner: UNT Libraries
Functional Characterization of Mtnip/latd’s Biochemical and Biological Function

Functional Characterization of Mtnip/latd’s Biochemical and Biological Function

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Date: December 2013
Creator: Bagchi, Rammyani
Description: Symbiotic nitrogen fixation occurs in plants harboring nitrogen-fixing bacteria within the plant tissue. The most widely studied association is between the legumes and rhizobia. In this relationship the plant (legumes) provides the bacteria (rhizobia) with reduced carbon derived from photosynthesis in exchange for reduced atmospheric nitrogen. This allows the plant to survive in soil, which is low in available of nitrogen. Rhizobia infect and enter plant root and reside in organs known as nodules. In the nodules the bacteria fix atmospheric nitrogen. The association between the legume, Medicago truncatula and the bacteria Sinorhizobium meliloti, has been studied in detail. Medicago mutants that have defects in nodulation help us understand the process of nitrogen fixation better. One such mutant is the Mtnip-1. Mtnip-1 plants respond to S. meliloti by producing abnormal nodules in which numerous aberrant infection threads are produced, with very rare rhizobial release into host plant cells. The mutant plant Mtnip-1 has an abnormal defense-like response in root nodules as well as defects in lateral root development. Three alleles of the Mtnip/latd mutants, Mtnip-1, Mtlatd and Mtnip-3 show different degrees of severity in their phenotype. Phylogenetic analysis showed that MtNIP/LATD encodes a protein belonging to the NRT1(PTR) family of ...
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Immunohistochemistry of the Gills of the Channel Catfish Ictalurus Punctatus: Cells and Neurochemicals That May Be Involved in the Control of Cardioventilatory Reflexes

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

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Date: December 2013
Creator: Oden, David S.
Description: 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) ...
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Investigation of the Pharmacokinetics of Diazepam in Juvenile Channel Catfish (Ictalurus Punctatus)

Investigation of the Pharmacokinetics of Diazepam in Juvenile Channel Catfish (Ictalurus Punctatus)

Date: December 2013
Creator: Overturf, Carmen L.
Description: The presence of pharmaceuticals in the environment is becoming an increasing regulatory and scientific concern. Thus, the metabolic profile and bioconcentration potential of diazepam, a model benzodiazepine, were examined, as well as effects on the endocrine system in channel catfish. Through the use of specific and non-specific cytochrome P450 (CYP450) inhibitors, it was determined that CYP3A-like enzymes may play a role in the biotransformation of diazepam into temazepam; however, the isoform(s) required for the formation of other metabolites is still unknown. Overall, only around 7-8% of diazepam is biotransformed into two known metabolites. Due to the lack of inherent metabolism of diazepam in channel catfish, further analysis was conducted to determine the tissue-specific bioconcentration potential of diazepam in catfish. Various tissues were analyzed for the presence of diazepam as well as metabolites and bioconcentration factors (BCF) were calculated, which were all well below regulatory threshold values (> 2000). Additionally, modulation of the endocrine system by diazepam was examined by measuring steroid hormone concentrations and analyzing mRNA expression of selected steroidogenic enzymes and receptors. Two steroidogenic enzymes were modulated following diazepam exposure, indicating potential endocrine disrupting properties of diazepam. Together, these data suggest that diazepam exhibits low metabolic transformation rates in ...
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Modeling the Effects of Chronic Toxicity of Pharmaceutical Chemicals on the Life History Strategies of Ceriodaphnia Dubia:  a Multigenerational Study

Modeling the Effects of Chronic Toxicity of Pharmaceutical Chemicals on the Life History Strategies of Ceriodaphnia Dubia: a Multigenerational Study

Date: December 2013
Creator: Lamichhane, Kiran
Description: Trace quantities of pharmaceuticals (including carbamazepine and sertraline) are continuously discharged into the environment, which causes concern among scientists and regulators regarding their potential long-term impacts on aquatic ecosystems. These compounds and their metabolites are continuously interacting with the orgranisms in various life stages, and may differentially influence development of embryo, larvae, juvenile, and adult stages. To fully understand the potential ecological risks of two candidate pharmaceutical chemicals (carbamazepine (CBZ) and sertraline (SERT)) exposure on survival, growth and reproduction of Ceriodaphnia dubia in three sucessive generations under static renewal toxicity test, a multigenerational approach was taken. Results indicate that SERT exposure showed higher sensitivity to chronic exposure to C. dubia growth and reproduction than CBZ exposure. The lowest concentration to affect fecundity and growth was at 50 µg L-1 SERT in the first two generations. These parameters become more sensitive during the third generation where the LOEC was 4.8 µg L-1. The effective concentrations (EC50) for the number of offspring per female, offspring body size, and dry weight were 17.2, 21.2, and 26.2 µg SERT L-1, respectively. Endpoints measured in this study demonstrate that chronic exposure of C. dubia to SERT leads to effects that occur at concentrations an order ...
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Molecular and Functional Characterization of Medicago Truncatula Npf17 Gene

Molecular and Functional Characterization of Medicago Truncatula Npf17 Gene

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Date: December 2013
Creator: Salehin, Mohammad
Description: Legumes are unique among plants for their ability to fix atmospheric nitrogen with the help of soil bacteria rhizobia. Medicago truncatula is used as a model legume to study different aspects of symbiotic nitrogen fixation. M. truncatula, in association with its symbiotic partner Sinorhizobium meliloti, fix atmospheric nitrogen into ammonia, which the plant uses for amino acid biosynthesis and the bacteria get reduced photosynthate in return. M. truncatula NPF1.7 previously called MtNIP/LATD is required for symbiotic nitrogen fixing root nodule development and for normal root architecture. Mutations in MtNPF1.7 have defects in these processes. MtNPF1.7 encodes a member of the NPF family of transporters. Experimental results showing that MtNPF1.7 functioning as a high-affinity nitrate transporter are its expression restoring chlorate susceptibility to the Arabidopsis chl1-5 mutant and high nitrate transport in Xenopus laevis oocyte system. However, the weakest Mtnip-3 mutant allele also displays high-affinity nitrate transport in X. laevis oocytes and chlorate susceptibility to the Atchl1-5 mutant, suggesting that MtNPF1.7 might have another biochemical function. Experimental evidence shows that MtNPF1.7 also functions in hormone signaling. Constitutive expression of MtNPF1.7 in several species including M. truncatula results in plants with a robust growth phenotype. Using a synthetic auxin reporter, the presence ...
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Origin and Role of Factor Viia

Origin and Role of Factor Viia

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Date: December 2013
Creator: Khandekar, Gauri
Description: Factor VII, the initiator of the extrinsic coagulation cascade, circulates in human plasma mainly in its zymogen form, Factor VII and in small amounts in its activated form, Factor VIIa. However, the mechanism of initial generation of Factor VIIa is not known despite intensive research using currently available model systems. Earlier findings suggested serine proteases Factor VII activating protease, and hepsin play a role in activating Factor VII, however, it has remained controversial. In this work I estimated the levels of Factor VIIa and Factor VII for the first time in adult zebrafish plasma and also reevaluated the role of the above two serine proteases in activating Factor VII in vivo using zebrafish as a model system. Knockdown of factor VII activating protease did not reduce Factor VIIa levels while hepsin knockdown reduced Factor VIIa levels. After identifying role of hepsin in Factor VII activation in zebrafish, I wanted to identify novel serine proteases playing a role in Factor VII activation. However, a large scale knockdown of all serine proteases in zebrafish genome using available knockdown techniques is prohibitively expensive. Hence, I developed an inexpensive gene knockdown method which was validated with IIb gene knockdown, and knockdown all serine proteases ...
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Population Dynamics of Zebra Mussels (Dreissena Polymorpha) in a North Texas Reservoir: Implications for Invasions in the Southern United States

Population Dynamics of Zebra Mussels (Dreissena Polymorpha) in a North Texas Reservoir: Implications for Invasions in the Southern United States

Date: December 2013
Creator: Churchill, Christopher J.
Description: This dissertation has two main objectives: first, quantify the effects of environmental conditions on spatio-temporal spawning and larval dynamics of zebra mussels (Dreissena polymorpha [Pallas 1771]) in Lake Texoma, and second, quantify the effects of environmental conditions on survival, growth, and reproduction of young of the year (YOY) juvenile zebra mussels. These biological responses directly influence population establishment success and invasive spread dynamics. Reproductive output of the zebra mussel population in Lake Texoma was significantly related to water temperature and lake elevation. Annual maximum larval (veliger) density decreased significantly indicating a population crash, which was likely caused by thermal stress and variability of lake elevation. In 2011, temperatures peaked at 34.3°C and lake elevation decreased to the lowest level recorded during the previous 18 years, which desiccated a substantial number of settled mussels in littoral zones. Estimated mean date of first spawn in Lake Texoma was observed approximately 1.5 months earlier than in Lake Erie, and peak veliger densities were observed two months earlier. Veligers were observed in the deepest oxygenated water after lake stratification. During a 69-day in situ experiment during summer in Lake Texoma, age-specific mortality of zebra mussels was generally high until temperatures decreased to approximately 28°C, ...
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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

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

Date: December 2013
Creator: Slye, Jaime L.
Description: 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.
Contributing Partner: UNT Libraries
Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio

Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio

Date: December 2013
Creator: Cantu, Mark
Description: 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 ...
Contributing Partner: UNT Libraries