Over the last few decades, there has been increasing concern regarding the environmental presence and biological effects of endocrine disrupting compounds. Studies aimed at determining the adverse impacts associated with exposures to thyroid disrupting compounds have focused primarily on the ability of such compounds to alter patterns of growth and development; however, the actions of thyroid hormones extend well beyond these basic functions. As such, there is a need to investigate the potential for thyroid disrupting compounds to alter other physiological processes. Recent studies have suggested a role for thyroid hormones in the regulation of immune function. As such, it is reasonable to suspect that exposure to endocrine disrupting chemicals that impair thyroid activity will lead to alterations in immune function and subsequent changes in pathogen and disease resistance. Using the fathead minnow (Pimephales promelas) as a model organism, this study sought to determine the impact of propylthiouracil (PTU, a known thyroid inhibitor) on various aspects of immune function including immune gene expression, spleen index and pathogen resistance. To achieve this, male fathead minnows were divided into two groups – a control and a PTU-exposed group. Following a 21day exposure period, both groups were challenged with the pathogen Yersinia ruckeri, and mortality was monitored for 14 days to assess pathogen resistance. In addition, tissues (i.e., liver, spleen and kidney) were sampled at 8 hours and 72 hours post infection for the assessment of immune gene expression and spleen index. PTU exposed males were less able to survive pathogen infection relative to the controls. In addition, PTU-exposed males had significantly lower spleen index than the controls following injections, suggesting that they had a reduced ability to elicit an immune response. Gene expression of certain immune genes also showed a change in pattern of expression, signifying potential pathways and proteins that are particularly affected by thyroid hormone presence. These results show that chemically-induced decreases in thyroid hormone levels can suppress immune function and demonstrate that the immune system is a target for thyroid disrupting chemicals.

Neotropical rain frogs serve as an indicator of habitat and ecological disruption in tropical rainforests through species-specific response to environmental stimuli. These responses are reflected in preference of habitat, such as primary or secondary forest, which may provide insights into the health and stability of not only Neotropical rain frogs and amphibians, but also of the surrounding ecosystem. We studied the diversity and abundance of rain frogs at the El Jamaical Field Station in Costa Rica, located in a transition zone between tropical rainforest and premontane rainforest, by overturning leaf litter along previously established trails that passed through both forest types, photographing found individuals, and recording discovery locations on a map. Focusing our study on the primary and secondary forests, we predicted that the diversity and abundance of rain frogs would be greater in the primary forest than in the secondary due to differences in diversity of trees and flora, humidity, temperature, and light levels. Data analysis will include species identification, proximity to dry streams, and comparison between primary and secondary forest.

The Syr Darya, one of the largest rivers in southern Kazakhstan, is a major source of freshwater feeding the Aral Sea. In the 1950s, water was diverted from the Syr Darya to support agricultural production leading to the drying of the Aral Sea, which has been characterized as one of the worst environmental catastrophes in modern day history. Mismanagement of these diverted waters has paved the way for potential surface water contamination in the Aral Sea Basin. While efforts to revive the Aral Sea are underway, few investigations have sought to assess the impacts of potential heavy metal contamination in the Syr Darya Watershed. As such, the goal of this study was to assess the presence and biological effects of heavy metal contaminants in the Syr Darya. This was accomplished by collecting water and sediment samples from five sites and roach (Rutilus rutilus) samples from three sites along the Syr Darya. Water, sediment, and roach muscle tissue samples were analyzed for a suite of contaminants, while roach liver, brain, gonad, and gill tissues were analyzed for the expression of genes considered to be biomarkers of heavy metal exposures (e.g., metallothionein and superoxide dismutase). Water and fish muscle tissue analysis revealed the presence of multiple heavy metals above local regulatory limits. Roach fish from two of the three sites experienced alterations in the expression of genes considered biomarkers of contaminant exposure suggesting that chemical loads at some of the sites in the Syr Darya were sufficient to induce biological effects. Data collected as part of this study will be utilized to complete an ecological risk assessment of the Syr Darya River basin.

Alzheimer’s disease is a neurodegenerative disorder characterized by the presence of amyloid beta (Aβ) plaques. This pathology results in neuronal dysfunction and eventual cell death. Aβ plaques come from the buildup of beta-amyloid protein which clump together and block cell-to-cell signaling at synapses. To stimulate Aβ production, our lab uses an inflammation model utilizing lipopolysaccharide (LPS) injections. When mice are given intraperitoneal LPS injections over the course of one week they show a significant increase of Aβ in the brain. When a second course of LPS is administered following a two-week recovery period, Aβ levels return to baseline levels. The initial exposure to LPS protects the mouse from a second exposure, preventing further increase in the Aβ. One likely explanation is that the initial exposure primes the immune system, enabling the mouse to quickly initiate an antibody response upon subsequent exposure to LPS. The objective of the present study was to investigate the antibodies produced after the second course of LPS in 5xFAD mice. Plasma antibody levels were measured, and co-localization of antibodies around hippocampal Aβ plaques was investigated. We found that mice who received a second course of LPS injections had a significantly higher amount of IgG co-localized around plaques compared to non-treated control animals. This correlated with higher levels of IgG in the plasma. This data suggests that LPS exacerbates the antibody response in 5xFAD mice, and that these antibodies may specifically target Aβ.

Changes in early physiological development due to chemical effluent exposure can be determined by measuring the levels of gene expression. Genes involved in cardiovascular and neurological development, as well as growth, serve as sensitive endpoints in toxicity tests involving the use of larvae. The purpose of this research was to determine when during development the level of gene expression was high enough for contaminant-induced decreases in expression to be detected. A suite of genes involved in growth, cardiovascular and neurological development was examined in embryos and larvae from 0 to 11 days post hatch. This information was used to determine time points at which selected genes were most highly expressed. For the growth-related genes, expression levels of growth hormone (gH) were highest at Days 4-7 and 11, levels of growth hormone receptor (gHR) at Days 1-7 and 11, and levels of insulin-like growth factor (igf1) at Days 4-11. For the thyroid hormone receptors, thyroid hormone receptor-α (TRα) showed highest expression levels at Days 3-11 and thyroid hormone receptor-β (TRβ) showed highest levels at Days 2-5 and 9. For the deiodinase enzymes, deiodinase-1 (Dio1) expression levels were highest at Days 2-3 and 7-11, levels of deiodinase-2 (Dio2) were highest at Days 7-11, and levels of deiodinase-3 (Dio3) were highest at Days 1-5. Vegfa, a gene involved in cardiovascular development, had levels of gene expression that were highest at days 7-11. HuC, a gene involved in neurological development, had the highest level of gene expression at days 7-11. When the level of expression of these genes is highest is when they have the greatest potential to be used in toxicity tests to measure alterations in expression.

Cancer is the second-leading cause of death in the US. Cancer cells are characterized by loss of regulation of the cell cycle that results in uncontrolled proliferation. To drive this high rate of cellular division, cancer cells have mutated to increase uptake of important nutrients including glucose and vitamins by increasing the number of glucose receptors and vitamin transporters, including biotin receptor, on their surface. Due to this difference in expression of biotin receptor between cancer and normal cells, research focusing on the use of biotin-conjugated molecules has gained attention as a method for anticancer drug delivery.
Another characteristic unique to certain cancer cells is that they exhibit dysregulation in normal cellular redox balance, such that the cellular environment becomes more reducing. A more reducing environment favors the generation of reactive oxygen species (ROS). Many metal-based anticancer drugs have taken advantage of this feature of cancer cells in an attempt to increase the levels of ROS to the point that harmful oxidation reactions occur that lead to cell death. Specifically, the iron atom of ferrocene has been shown to lead to the generation of damaging ROS upon oxidation from Fe2+ to Fe3+.
A problem with current cancer treatment is that the chemotherapeutics often are not specific to cancer cells and can lead to negative side effects. As a result, anticancer drugs with high specificity and cytotoxicity are needed to improve treatments. This research project focuses on testing the cytotoxicity of a variety of biotin-ferrocene derivatives on cancer (HeLa) and non-cancer (293HEK) cell lines. HeLa cells are known to express high levels of biotin receptor and are predicted to have more reducing cellular environments; additionally, 293HEK cells express low levels of biotin receptor and are predicted to have less reducing environments. The tested compounds have three main features: a biotin moiety, a ferrocene core, and a variable linker covalently bound to the ferrocene moiety. We hypothesize that the biotin-containing compounds will enter HeLa cells more efficiently than 293HEK cells, allowing for the ferrocene moiety to reduce oxygen, leading to increased ROS generation and cell death.
Here, we demonstrate that ferrocene shows dose-dependent cytotoxicity specific to HeLa cells, while one of the compounds shows dose-dependent cytotoxicity specific to 293HEK cells. Interestingly, two of the compounds show dose-dependent cytotoxicity to both cell lines. These findings are particularly intriguing in that there appears to be a difference in specificity between some of the compounds. However, future studies are required to reveal how these differences in cytotoxicity are related to the differences in chemical moieties and by what mechanisms these compounds are acting to cause specific cytotoxicity.

Most plants acquire mineral nutrients from the soil. However, in nutrient-poor environments, some plants have evolved carnivorous traits that allow them to obtain nutrients by capturing and digesting insects. For example, the carnivorous pitcher plant Sarracenia alata uses passive pitfall traps to capture their insect prey. Although studies have examined prey composition for S. alata, few have included a comparison to the insects available in the environment. The purpose of this study was to compare prey capture of S. alata pitchers with the available insects to determine whether this species is selective in prey capture. The available insects were sampled using artificial sticky traps in the vicinity of the pitchers. The insects in the study were identified first to the level of order and then further identified to “morphospecies” as a means of examining preference on a finer scale. The results show that the pitchers captured only a subset of the available insects. The average number of orders captured by each pitcher (1.8 ± 1.0 SD) was lower than that captured by artificial traps (2.8 ± 0.5). Likewise, the average number of morphospecies captured by the pitchers (4.5 ± 4.8) was lower than that captured by the artificial traps (6.8 ± 3.5). These results support the hypothesis that S. alata is selective in its prey capture, but further studies are needed with different methods of measuring the available insects in order to avoid potential bias.

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.

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.

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.