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Pilot study on the transport and effect of hormonally-active compounds in Texas watersheds

Type: Graduate
Author(s): Kyle Roush Biology
Advisor(s): Marlo Jeffries Biology

Globally, there is demand for increased meat production. Texas, a leader in cattle production in the United States, has met this demand utilizing confined animal feeding operations (CAFOs) containing hundreds to thousands of cattle. To increase production efficiency, cattle receive growth-promoting hormone treatments to enhance growth and increase cattle mass. These hormonally-active compounds (HACs) have been found in cattle waste, feedlot runoff, and surface waters. The ultimate goal of this project was to identify watershed characteristics that promote the transport of cattle-associated HACs to surface waters. Therefore, the objectives of this pilot study were to: 1) identify and define a study area for evaluating HACs in Texas watersheds and 2) begin preliminary assessments of HAC activity in watersheds downstream of cattle feedlots. A suitable study site was identified using satellite imagery, elevation data and the ArcGIS hydrology tool pack. Sample sites were selected within this area based on geographical features and position to CAFOs. Caged fish studies, followed by analysis of estrogen-responsive gene expression, were utilized to assess the presence and activity of HACs. Though no statistically significant alterations in estrogen-responsive gene expression metrics were observed, females from three of the four sites downstream of CAFOs experienced 2.9 to 3.7-fold and 1.9 to 5.3-fold decreases in the expression of estrogen receptor alpha and vitellogenin, respectively. This could have larger implications as previous research by Miller et al. 2007 forecasted that a 50% reduction in vitellogenin plasma concentration could result in a 41.8% decrease in average population size after one year.

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Measuring Associations Between Polymorphisms in the GREB1L Gene and the Development of Different Migratory Phenotypes in Oncorhynchus mykiss

Type: Undergraduate
Author(s): Ben Showalter Biology
Advisor(s): Matthew Hale Biology

Rainbow trout, Oncorhynchus mykiss, exhibit two life-history strategies: resident rainbow trout and migratory steelhead trout. Previous research has shown that the migratory decision is highly heritable. Recently, interest has focused on the GREB1L gene as studies in several populations of rainbow trout have found alleles associated with migration. This project aimed to measure allelic associations between GREB1L and migratory life-history in rainbow trout from Sashin Creek, Alaska. Sequence data suggests that all individuals, regardless of migratory trajectory, had alleles associated with migration. These results confirm that there are population specific genetic effects that determine the migratory life-history of rainbow trout.

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The Comparison of Herbivory Damage on Red and Green Leaves in a Neotropical Rainforest

Type: Undergraduate
Author(s): Kristen Silva Biology Amal Khan Biology
Advisor(s): Dean Williams Biology Amanda Hale Biology Michael Misamore Biology

A distinctive feature in many tropical trees is the presence of red young leaves which turn green with maturity. Some theories as to why the young leaves are red is because it could signal to herbivores that the young leaf is full of toxins, or that it is low in nutrients. During a spring break trip to the TCU Field Station in Costa Rica we tested the hypothesis that green leaves have more herbivory damage than red ones. Fifteen trees were randomly sampled in the secondary forest. All the leaves were counted on the selected trees and we recorded the total number of both red and green leaves and then how many leaves of each color had herbivore damage. We then analyzed the ratio of damaged red and green leaves to determine if red leaves are predated on less than green leaves. This will help us understand if this means that red leaves have a natural defense against herbivory.

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DNA Barcoding Insect Species for Texas Horned Lizard Diet Analysis

Type: Undergraduate
Author(s): Kaitlyn Upton Biology
Advisor(s): Dean Williams Biology

The Texas horned lizard (Phrynosoma cornutum) is a threatened species in the state of Texas whose main dietary staple is believed to be the harvester ant (Pogonomyrmex spp.). In two South Texas towns horned lizards are consuming many ants and termites other than harvester ants and so we developed DNA barcoding methodology to help identify these taxa in the DNA extracted from horned lizard feces. We used a small portion of the mitochondrial cytochrome oxidase I gene to confirm morphological identifications and to identify ants and termites to the species level from horned lizard scat.

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To BEE or Not to BEE? – Species Diversity and Abundance in the Neotropics

Type: Undergraduate
Author(s): Julianna West Biology Bobby Boone Biology Troy Marshall Biology Julianna Martinez Biology
Advisor(s): Amanda Hale Biology

Euglossine, or Orchid bees, belong to a monophyletic clade of neotropical bees and are specialized pollinators for orchids in the neotropics. Orchid bees are used to study the effects of deforestation and pollination patterns because the males collect fragrances, and therefore by using scents, can be tracked and counted throughout a habitat. Because previous research has shown that scent preference and orchid bee diversity varies across different habitats, we wanted to compare the abundance and diversity of euglossine bees in a forest edge, a secondary forest, and a primary forest near San Ramón, Costa Rica. By placing different scents on filter papers, we counted and identified the number of bees attracted to each scent. We found a variation in scent preference and species diversity across the different forest types. At a forest edge, more bees were attracted to eugenol, while in the secondary forest, most bees preferred cineole. Methyl salicylate was the scent preferred in the primary forest. Scent preference also varied between different species and species diversity was different between the habitat types. While Eulaema meriana was common in both habitats, E. meriana was observed more frequently in the forest edge, while Euglossa imperialis was not seen in the forest edge and was more abundant in the secondary forest and the primary forest. These findings indicate that changes in habitat type and forest structure can impact orchid bee diversity, thus affecting the tropical ecosystem.

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The Effect of Hepatitis C Virus Non-Structural Protein NS5A on Antiviral Gene Expression

Type: Undergraduate
Author(s): Emily Williams Biology
Advisor(s): Giridhar Akkaraju Biology

Hepatitis C Virus (HCV) is a bloodborne pathogen that infects approximately 3 million people in the United States and 140 million people worldwide. Once infected, only 15-25% of patients are able to clear the virus from their systems without treatment, leaving 75-85% of affected individuals with a chronic, life-long infection. Chronic HCV is often asymptomatic until decades after infection, so many patients are unaware of the need for treatment until damage has already reached advanced stages. Long-term HCV infection can lead to several serious diseases, including chronic hepatitis, liver cirrhosis, and liver cancer. In the United States, chronic HCV infection is the leading cause for liver transplants. As a RNA virus, mutations in the HCV genome are relatively common. Currently, there are 6 genotypes and at least 50 subtypes of the virus, which can affect response both to pharmaceutical treatment and to the host innate immune response.
When HCV infects a cell, the cell fights the infection by turning on the expression of antiviral genes, such as interferon-beta (IFNb). Once IFNb is produced, it is secreted from the cell and in turn activates expression of interferon-stimulated genes (ISGs) in the same cell and surrounding cells, thereby triggering the host innate immune response. HCV produces proteins that are capable of blocking IFNb. Without IFNb, the host is unable to fight off the HCV infection, which allows the infection to become chronic. Our lab has shown that the HCV non-structural protein NS5A inhibits Sendai Virus (SV)-induced IFNb gene expression, and is also vital to viral replication.
This study focuses on two mutant forms of HCV NS5A. NS5A 10A is the K2040 mutant with a lysine deletion, and has been shown to result in increased levels of viral replication. NS5A H27 is the L2198S mutant with a lysine to serine substitution, and has been shown to result in decreased levels of viral replication. We hypothesize that the differences in levels of replication between the two mutants is due to differential inhibition of SV-induced IFNb gene expression. Cells expressing NS5A 10A should have lower levels of antiviral gene expression, while expression of NS5A H27 should lead to higher levels of antiviral gene expression. RT-PCR and q-RT-PCR was performed on HEK 293 cells in order to measure differences in gene expression of IFNb and ISGs MX1, OAS1, and TRIM14 in the presence or absence of Sendai Virus and NS5A. GAPDH was used as an endogenous control, as GAPDH levels are unaffected by viral infection. Cells were infected using Sendai Virus in order to trigger the IFNb antiviral pathway, and were transfected with the different mutant forms of NS5A.

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