For several years, Texas horned lizards (Phrynosoma cornutum) in Kenedy and Karnes City (TX) have been the subject of ongoing studies at TCU. In the past decade lizards have disappeared from multiple locations in these towns, suggesting these populations are declining. To determine whether these populations have been stable or are declining in recent years, I used ArcGIS software to map GPS coordinates and calculate spatial statistics of horned lizards, their fecal pellets, and harvester ant mounds from 2013-2016. Stable spatial statistics across this time period should correlate with population stability at these sites.
Over the past century, millions of hectares of tropical rain forest have been cleared due to logging and agricultural endeavors. In addition to direct effects to terrestrial systems, conversion of land for agricultural use alters inputs to watersheds and has indirect effects on surrounding aquatic communities. Stream macroinvertebrates, which are often used as indicators of ecosystem health, can experience substantial changes in species composition as a result of these watershed alterations. We sampled macroinvertebrates from riffles and pools in a small stream with agricultural headwaters near the TCU El Jamaical Field Station in Costa Rica. We identified invertebrates to the lowest taxonomic level, and compared species abundance, richness, diversity, and evenness between riffles and pools. The high water quality and presence of bioindicator species suggest that this stream has been relatively unaffected by anthropogenic ecosystem alterations
Exposure to endocrine disrupting chemicals (EDCs), compounds that disrupt the normal hormone signaling pathways, can lead to a wide variety of negative outcomes in organisms. Although it has been shown that endocrine signaling systems interact with each other, research into the effects of EDCs has typically focused on a single endocrine axis independent of all others. This means that alterations in processes associated with nontargeted endocrine systems may be ignored. The interaction may also make it difficult to identify mechanisms of newly discovered EDCs. Because of these potential issues, it is important to understand the outcomes of endocrine axis interaction in organisms used as models for EDC testing. This experiment examined the effects of exposure to model thyroid disruptors, thyroxine (T4) and propylthiouracil (PTU), on reproductive function in the fathead minnow (Pimephales promelas). This species is a commonly used model organism but the outcomes of thyroid-reproductive system interaction are unknown. In addition to endpoints traditionally associated with the thyroid (e.g., thyroid related gene expression), this study included endpoints associated with overall reproductive function (e.g., number of eggs laid) and those more specific to the reproductive endocrine system (e.g., sex steroid related gene expression). It was found that model thyroid disruption lead to alterations in several thyroid and reproductive endpoints. Information on how thyroid disruption affects reproductive function in the fathead minnow will aid future experiments on EDC exposure in this species.
Author(s): Madeline Bush Biology Kevin Claunch Biology Chris Evans Biology Jacob Malmquist Biology
Advisor(s): Shauna McGillivray Biology
Location: Session: 2; 2nd Floor; Table Number: 9
ClpX is a regulatory ATPase that functions along with ClpP as part of the intracellular bacterial ClpXP protease. Previous research from our group has shown that genetic loss of ClpX (∆ClpX) in Bacillus anthracis Sterne increases susceptibility to antimicrobial agents that target or interact with the cell wall including penicillin, daptomycin, and LL-37. In order to gain a better understanding of ClpX function in B. anthracis Sterne, a microarray analysis comparing WT and ∆ClpX gene expression was performed in B. anthracis. We found that LrgAB, a negative regulator of autolysis, was significantly downregulated in the ∆ClpX mutant and this finding was confirmed with QPCR. In order to determine whether LrgAB also had a role in antibiotic resistance in B. anthracis, we made a genetic deletion of LrgAB (∆LrgAB) and found it has similar phenotypes to ∆ClpX in B. anthracis. To see if these findings were consistent in other gram- positive pathogens, we expanded our research to Staphylococcus aureus, the leading cause of skin and soft tissue infections. We constructed a ∆ClpX mutant in the Newman strain of S. aureus and found it also exhibited sensitivity to cell wall active antimicrobial agents. Loss of ClpX in S. aureus also resulted in decreased expression of LrgAB by QPCR. Lastly, we examined a S. aureus ∆LrgAB mutant and observed an increase in antibiotic susceptibility. We conclude that ClpX plays a role in resistance to cell wall active antimicrobials in both B. anthracis and S. aureus, and that this is connected to its regulation of LrgAB.
Carnivorous plants inhabit nutrient-poor environments, and they supplement nutrient uptake by capturing and absorbing nutrients from prey, such as insects. Like other plants, carnivorous plants are subject to loss of nutrient-containing tissues to herbivores. Because they occur in low-nutrient environments, tissue loss to herbivory can be expected to have a particularly strong negative effect on carnivorous plants. However, herbivory in carnivorous plants has not been well studied. In this study, we quantified tissue and nutrient losses sustained from herbivory by larvae of the specialist moth, Exyra semicrocea, in a population of pitcher plants, Sarracenia alata. We conducted field surveys, analyses of areal foliar damage, nutrient analyses, and feeding trials. In the study population, 83% (0.83 ± 0.033; mean ± SE) of pitchers were damaged by E. semicrocea. On average, approximately 15% of each affected pitcher was consumed before the larvae began feeding on another pitcher. Mean foliar nitrogen concentration was 1.19%, resulting in a mean nitrogen loss to consumption of 0.24 ± 0.041 mg per pitcher (N = 40). Mean foliar phosphorus concentration was 0.044%, resulting in a mean phosphorus loss per pitcher of 0.0086 ± 0.0015 mg (N = 37). In preliminary feeding trials, 4th and 5th instar larvae consumed 32 ± 3.8 mg /day and 33 ± 4.3 mg /day, respectively. Based on these consumption rates, estimated mean time spent feeding on a single pitcher was 2.5 ± 0.18 days (N = 95). Current studies are evaluating the impact of herbivory on reproductive output of these plants.
Breast cancer is a growing problem in the United States and worldwide. It takes the lives of approximately 40,000 U.S. women a year. 1 in 8 U.S. women will develop breast cancer during the course of their lifetime and it continues to be the most commonly diagnosed cancer in women. Clearly, this is a serious issue that must be solved. Current chemotherapy treatments often result in widespread cell death, including the killing of healthy cells. Therefore, it is necessary to find alternative treatments that specifically target cancer cells. Many breast cancer cells over express estrogen receptors, which are vital to the rapid cell division and growth of tumors. Estrogen is a steroid hormone that enters the cell, binds to its receptor, translocates to the nucleus, and leads to gene expression. Previous work from our group has resulted in the development of a drug which targets estrogen receptor positive breast cancer cells called Est-3-Melex. The drug contains a DNA methylating group (Melex) conjugated to estrogen. The mechanism of action of the drug is by the binding of the estrogen portion of the molecule to its receptor that ultimately translocates to the nucleus. While in the nucleus, the Melex portion of the compound is brought in close proximity to the DNA and methylates the adenines, eventually resulting in cell death. Essentially, this is a receptor targeted cancer therapy. In order to test the toxicity of this drug, we utilized a MTT cytotoxicity assay, which quantifies the amount of cell death. Est-3-Melex was more toxic to cancer cells that overexpressed the estrogen receptor compared to those that did not. Treating the estrogen receptor positive breast cancer cells with excess amounts of estrogen inhibited Est-3-Melex-induced cell death. Fluorescence imaging was also utilized to visualize localization of the drug. A fluorescent tag was attached to Est-3-Melex and introduced into estrogen receptor positive breast cancer cells. The results showed the drug localized to the nucleus and this localization was inhibited by estrogen. Our results suggest that Est-3-Melex is effective in specifically killing estrogen receptor positive breast cancer cells by binding to the estrogen receptor. Additional investigations are underway to identify the mechanism of cell death.
The effects of the thyroid axis on metabolism, growth, and development are well documented. However, there is a paucity of information on the role of thyroid hormones in the development of the immune system. Therefore, the goal of this study was to determine the effects of early life stage exposures to thyroid-altering chemicals on the developing immune system using the fathead minnow (Pimephales promelas) as the model, an organism commonly used in toxicity testing. This was accomplished by measuring differential expression of several immune-related genes in fish exposed to various doses of propylthiouracil (PTU, a thyroid-inhibitor) and thyroxine (T4, a thyroid-stimulator) sampled at 7 and 35 days post hatch (dph). Fish exposed to PTU exhibited significant increases in rag2 expression at 7 dph, decreases IgLC1 expression of at both 7 dph and 35 dph, and decreases in IgLC3 expression at 7 dph. In contrast, T4-exposed fish showed elevated rag1 and rag2 expression at both 7 and 35 dph, increased IgLC2 expression at 7 dph, and upregulation of ikaros at 35 dph. The results of this study indicate that exposure to thyroid altering chemicals influences the expression of several genes associated with proper immune system development, indicating that thyroid hormones regulate various aspects of immune development. These findings provide evidence that exposures to environmentally-relevant compounds that modulate thyroid function may lead to improper immune system development, which is likely to adversely affect overall organism health.
Recent research has identified dung beetles as bioindicator species found in a wide range of environments. Bioindicators function as monitors for the health of an ecosystem, which can be determined by analyzing the function, population, or status of the species in said environment. The purpose of our project was to determine if dung beetle diversity and abundance differed between primary and secondary rainforests. We conducted a study in the transition zone between tropical wet forest and premontane rainforest at the El Jamaical Field Station in Costa Rica. We acquired feces from both cows and horses near the field station. For trial 1, we made four bait traps using cow feces and one control for each of the forest types. Within each forest type, we placed the bait traps 25 meters apart. We then repeated the experiment using horse feces for trial 2. Traps sat for a period of 24 hours to allow dung beetles time to burrow into the traps. We then collected and processed the samples. Processing consisted of sifting and breaking down the feces in a meticulous manner to find, collect and identify all dung beetles present. We identified a total of 303 beetles in trial one and 0 in trial 2.
Mercury (Hg) is a toxic heavy metal that contaminates aquatic food webs. Methylated Hg can accumulate in fish, posing health hazards to fish-eating birds. All water bodies in the south central U.S. are contaminated with Hg but the level of contamination varies with ecoregion. Spatial patterns in the risk that Hg-contaminated fish pose to fish-eating birds is not understood. The objective of this study was to quantify Hg levels in a common fish species (bluegill, Lepomis macrochirus) and determine if the Hg contamination of bluegill poses a risk to a native fish-eating bird (the double-crested cormorant, Phalacrocorax auritus) in 14 USEPA level III ecoregions in six states in the south central U.S. We used the National Descriptive Model for Mercury in Fish to estimate the concentration of Hg in 8-cm total length bluegill in 835 sites. We then compared those Hg concentrations to the cormorant wildlife value (WV), an estimate of the minimum concentration of Hg in the diet of the consumer to cause physiologically significant doses. The concentration of Hg in bluegill exceeded the WV in 38% of sampling sites across the region. Within the 14 ecoregions the proportion of sampling sites that exceeded the wildlife value ranged from 7% to 77%. Ecoregions with highest Hg deposition from the atmosphere adjusted for conifer coverage had the highest proportion of sampling sites exceeding the WV.
Mercury (Hg) is a hazardous contaminant that can be transferred from aquatic to terrestrial environments by emerging aquatic insects. Terrestrial predators, such as spiders, that live along shorelines of water bodies may consume emerging aquatic insects and become contaminated with Hg. Mercury-contaminated spiders may pose a risk to arachnivorous songbirds. The degree to which most families of spiders are contaminated with Hg and the risk they pose to songbirds is not well understood. The objectives of this study were to determine 1) Hg concentrations in two families of shoreline spiders (long-jawed orbweavers, [Tetragnathidae] and crab spiders [Thomisidae]) and 2) determine the risk these spiders pose to arachnivorous birds. We collected representatives from two families of spiders from the shorelines of 10 ponds located at the LBJ National Grassland in north Texas, USA. Both spider taxa in the present study were contaminated with Hg, however long-jawed orb weavers had significantly higher concentrations of Hg in their tissues than crab spiders (p < 0.001; average Hg concentration = 346 ng/g and 35.7 ng/g respectively). We calculated wildlife values for various songbirds to determine health risks that these Hg-contaminated spiders may pose to songbirds. Spider-based wildlife values revealed that one of the families of shoreline spiders, Tetragnathidae, had concentrations of MeHg high enough that they may pose a risk to arachnivorous songbirds that consume spiders along the shorelines of ponds.
Mercury (Hg) is a toxic environmental contaminant formed in aquatic systems by bacterial methylation of inorganic mercury deposited from the atmosphere. Historically Hg contamination of food webs was thought to be restricted to aquatic systems. However recent research has shown that emergent aquatic insects such as dragonflies are contaminated with Hg as aquatic larvae, and then transport it to terrestrial ecosystems when they emerge from the water as adults. Terrestrial predators such as birds can be contaminated with Hg when the consume Hg-contaminated dragonflies. Because dragonfly larvae are top predators in aquatic systems, they contain high concentrations of Hg when they emerge from aquatic systems and can potentially pose a threat to the health of birds that feed on them. The objective of this study was to estimate the Total Hg (THg) concentrations in dragonflies across ecoregions in the South Central U.S. and the hazard Hg-contaminated dragonflies pose to dragonfly-consuming birds. I estimated THg concentrations in dragonflies by using published data on THg concentrations in predatory fish (pF) in 14 ecoregions and converting it to THg concentrations in gomphid dragonflies (gD) assuming a linear relationship (gD) = 0.0856(pF) + 25.92 constructed using data from Haro et al. 2013. The variation of predicted dragonfly THg was mapped by ecoregion using GIS software. GIS analysis tools were used to assess the risk the predicted THg in dragonflies that would pose a health hazard to dragonfly-consuming red winged blackbirds (Agelaius phoeniceus) in each ecoregion.
Mercury (Hg) is a highly toxic environmental contaminant found in all waterbodies on earth. Emergent aquatic insects (like mosquitoes) transfer Hg from the aquatic systems to terrestrial consumers such as spiders. The objective of this study was to examine Hg concentrations in larval mud daubers (Sceliphron caementarium) and their spider prey in mud dauber nests. Adult mud daubers capture spiders with a paralyzing sting to use as the food source for the larvae in their nest. I collected 350 mud dauber nests from three bridges on the Trinity River and one building 40 m inland from the Trinity River in Fort Worth, TX. The nests contained 74 mud dauber larvae and over 2,000 spiders of five different families. I used a Direct Mercury Analyzer to determine the total Hg concentration of mud dauber larvae and five spider taxa. All mud dauber larva and spiders were contaminated with Hg. The inland site had the lowest concentration of Hg in the spiders, suggesting that the spiders at this site were more reliant on low Hg terrestrial prey than high Hg aquatic prey. This is the first study to demonstrate that mud daubers nesting along river systems are part of the mercury cycle because of their use of shoreline spiders as prey for their larvae.
Leaf cutter ants are the rainforest’s most prolific herbivore, eating more vegetation than any other type of creature. The ants have a profound effect on the Neotropical ecosystem, for they improve the richness of the soil, and, by removing leaves from the trees, allow sunlight to reach the lower levels of the forest, facilitating plant growth and diversity. Leaf cutter ants are selective in the plant materials they harvest. The goal of this study is to determine whether leaf cutter ants have a preference for fragile versus tough leaves by examining the relationship between level of leaf damage by leaf cutter ants and leaf toughness among a number of plant species. Leaves damaged by leaf cutter ants of several plant species were identified and collected from the trails of two ant nests in El Jamaical Field Station in Costa Rica. Area of leaf cutter herbivory were traced and recorded as the measurements for level of leaf herbivory. Leaf toughness was quantified as the force required for tearing the leaf apart by using a gravity-based tearing device. From the obtained data, we will examine the level of leaf herbivory of each leaf of the same species against its toughness to see whether leaf cutter ants prefer cutting fragile leaves over tough leaves in order to minimize energy cost. We will also compare this foraging pattern between species to see whether there is a variation in the ants’ preference among different plant species.
The United States requires that whole effluent and chemicals be tested for aquatic toxicity using the fathead minnow larval growth and survival (LGS) test. While the LGS test has been effective for determining acute and chronic aquatic toxicity, a fathead minnow fish embryo toxicity (FET) test has been proposed as a refinement to the LGS as younger organisms are thought to experience less stress during toxicant exposure. Presently, the FET test protocol does not include endpoints that allow for the prediction of non-lethal adverse outcomes or chronic toxicity. This limits its utility relative to other test types. This study investigated the utility of sublethal endpoints related to cardiovascular function and development (e.g., heart rate, pericardial area, and cardiovascular related genes) as additional FET test metrics. FET tests were run with four model toxicants: 3,4 –dichloroaniline, sodium chloride, cadmium, and triclosan. Heart rate was evaluated at 76 hpf, while pericardial area was assessed at 120 hpf. Hatched larvae were sampled at the conclusion of the tests (120hpf) for gene expression analysis. Pericardial area was identified as the most sensitive sub-lethal endpoint, although alterations were also seen in the other metrics investigated. These alterations suggest that sublethal endpoints related to cardiovascular function and morphology may be useful for estimating non-lethal adverse effects and chronic toxicity. Future studies aimed at linking alterations in these endpoints to longer term adverse impacts are needed to fully describe the predictive power of these metrics in whole effluent and chemical toxicity testing.
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.
Wind energy is a renewable resource with many environmental benefits. However, one environmental impact from wind energy is on bats, because bats can be killed when they fly into the path of spinning turbine blades. Estimates of bat fatalities at wind facilities across the U.S. exceed 500,000 per year. One potential way to reduce bat fatalities at wind facilities is with acoustic deterrents. These devices, including the newly designed acoustic deterrent tested during this study, produce sound which is intended to disrupt bat echolocation. We used video cameras to evaluate bat activity and behavioral responses to the acoustic deterrent at a wind facility in north-central Texas. The acoustic deterrent reduced the level of bat activity by up to 90%, and also altered the flight behavior of bats. Our data indicate that this acoustic deterrent could significantly reduce bat fatalities at wind facilities once the devices are installed on turbines.
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.
Author(s): Michaela O'Connor Biology Haley Moore Biology Kelsey Paulhus Biology Morgan Thompson Biology
Advisor(s): Michael Chumley Biology Gary Boehm Psychology
Location: Session: 2; B0; Table Number: 10
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.
(Poster is private)
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.
Author(s): Celeste Ortega-Rodriguez Biology MacGregor Hall Biology James Kennedy Biology Kyle Lauck Biology Kirkland Polk Biology Edward Williams Biology
Advisor(s): Matt Chumchal Biology Ray Drenner Biology
Location: Session: 1; B0; Table Number: 2
Mercury (Hg) is a hazardous contaminant that can be transferred from aquatic to terrestrial environments by emerging aquatic insects. Terrestrial predators, such as spiders, that live along shorelines of water bodies may consume emerging aquatic insects and become contaminated with Hg. Mercury-contaminated spiders may pose a risk to arachnivorous songbirds. The degree to which most families of spiders are contaminated with Hg and the risk they pose to songbirds is not well understood. The objectives of this study were to determine 1) Hg concentrations in seven families of shoreline spiders, 2) if each family was connected to the aquatic food web via the consumption of emergent insects and 3) determine the risk these spiders pose to arachnivorous birds. We collected representatives from seven families of spiders along with a variety of aquatic and terrestrial plant, invertebrate, and fish samples from 10 ponds located in north Texas, USA. We used methylmercury (MeHg) concentrations in combination with stable isotopes of nitrogen (δ15N) to determine if each family of shoreline spider was connected to the aquatic food web. All spider taxa in the present study were contaminated with Hg and connected to the aquatic food chain. We calculated wildlife values for various songbirds to determine health risks that Hg-contaminated spiders may pose to songbirds. Spider based wildlife values revealed that six of the seven families of shoreline spiders examined had concentrations of MeHg high enough that they may pose a risk to arachnivorous songbirds that forage for spiders along shorelines of ponds.
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.
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.
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.