In a delayed serial same-different discrimination procedure, one stimulus is followed by either the same or a different stimulus after a brief delay. To receive reinforcement (e.g., food), the subject must respond “same” when the two stimuli match and a “different” response when they differ. The individual stimuli change across trials, so it is the relation between stimuli that signals the correct response. A differential outcomes procedure has been shown to facilitate learning of some discriminations but had not been tested with rats in a relational discrimination. In a differential outcomes procedure, one reinforcer (e.g., pellets) follows one response (e.g., a correct “same” response) and a different reinforcer (e.g., sucrose) follows another correct response (e.g., a correct “different” response). In the control condition, the same reinforcer follows a correct “same” and “different” response. In the current experiment, half of the rats were trained on a serial same-different discrimination using a differential outcomes procedure and the other half were in the control group. Stimuli were presented and responses recorded on an iPad mounted at the rear of an operant box. After the rat touched the sample stimulus (i.e., the first stimulus) it was removed for a delay of 500, 1500, 3000, or 6000 ms before the rats were presented with the comparison stimulus (i.e., the second stimulus). After touching the comparison stimulus, a response button appeared on each side of it. One button represented a “same” response and the button on the other side a “different” response. After training, rats were tested to determine if learning of the same-different relation would transfer to novel stimuli. The results showed no transfer of learning, and a decrement in performance on trials with the original training stimuli.

Individuals with Autism Spectrum Disorder (ASD) tend to have difficulties with emotional and social interactions (e.g., Stone & Caro-Martinez, 1990). It is possible that they also have deficits in their ability to monitor their learning of social and emotional information. If so, this could have negative downstream effects on their later memory. In the present experiment, we investigated the influence of social and emotional pictures on adolescents’ (with and without ASD) monitoring of learning and memory performance. To do so, participants studied 60 pictures that were positive or neutral and that either had a social component (e.g., a couple at their wedding, a child reading a book) or did not (e.g., ice cream, screwdriver). After studying each image, participants made a judgment of learning (JOL) predicting the likelihood that they would remember that picture on a later test. Finally, participants took a free-recall test. Overall, adolescents with ASD provided lower JOLs and demonstrated lower memory performance than did adolescents without ASD. In addition, all participants gave higher JOLs to positive pictures than to neutral pictures, and recall was also superior for positive relative to neutral pictures. Finally, participants gave higher JOLs to pictures with a social component than to pictures without a social component, although this dimension did not influence their memory. These results suggest that monitoring of learning is not impaired in adolescents with ASD. Thus, although adolescents with ASD tend to remember less than adolescents without ASD, this finding does not appear to be caused by monitoring deficits.

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.

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 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.