Bacteria can inherit genes through two modes of transmission: vertical inheritance, in which a cell receives genes from its parent cell during division, or horizontal gene transfer, in which genes are passed laterally between two unrelated cells. Extrachromosomal DNA, called plasmids, can be transmitted from a bacterial cell to a neighboring cell of the same or different species through a form of horizontal gene transfer known as conjugation. These conjugative plasmids can encode for antibiotic resistance genes which allows a host cell to produce proteins that degrade antibiotics. In an environment with these drugs, a host cell with this plasmid would be more likely to survive, compared to a plasmid-free cell, due to the benefits of the antibiotic resistance gene. Additionally, these antibiotic resistance genes can often acquire mutations which increases the level of antibiotic resistance for the host cell. However, these acquired mutations may be more beneficial (i.e., higher resistance for the host cell) in one bacterial species than the same mutation in another species. In other words, the effect of mutation on the plasmid-encoded antibiotic resistance gene may be contingent upon the host species. Given that antibiotic resistance genes are often encoded on conjugative plasmids that are shared among species, my project is investigating how protein evolution may be affected due to plasmid genes existing in multiple bacterial hosts. I performed a series of competitions between three bacterial species containing plasmids with versions of an antibiotic resistance gene to determine which versions of the gene outcompete others in an environment containing antibiotics. In doing so, I can determine how this particular gene may evolve when various bacterial hosts exist in a microbial community. The results of this experiment will improve our understanding of plasmid biology and the evolution of antibiotic resistance genes in diverse communities of bacteria.

Mexico underwent a dramatic cultural revolution in 1920, and from this revolution sprung a new type of art. ‘Los Tres Grandes,’ as they came to be known, were three men, Rivera, Orozco, and Siqueiros, who painted legendary murals depicting anti-capitalist and Revolutionary themes. This paper discusses the works of David Alfaro Siqueiros, a revolutionary Mexican mural painter, and his involvement in the Modernist movement in the United States. I first explore Siqueiros’ Los Angeles mural America Tropical and argue that he created it to be a strong political statement in a time of national turmoil. I explore the iconology and iconography of the piece that combined ancient Maya symbolism with modern techniques, creating a wholly new form of publicly available art. I also highlighted the importance of the location of this mural in a Los Angeles district that relies on white tourism for survival, and contrasted it with a mural highlighting the suffering of Indigenous people in the United States and America as a whole. Focusing on his time spent in the United States, I also explore his artist-relationship with the modernist painter Jackson Pollock and Siqueiros’ apparent influences on his style. Finally, I will discuss the influences that Los Angeles art culture had on Siqueiros, including a change in his mural style from individualistic to collectivist.

When massive stars die, they explode in violent spectacles known as supernovae, specifically core-collapse supernovae. These cataclysmic events produce and distribute a large fraction of the heavy elements in the universe, but the properties of the massive stars that produce them have historically been difficult to measure. I have made new measurements constraining the masses of stars that have produced core-collapse supernovae, also known as supernova progenitors. I have done this by measuring the ages of stars at the location of supernova remnants: the nebulae of excited and enriched gas left behind by supernovae that have occurred over the past 20,000 years. Assuming the progenitor was associated with these stars, I am able to estimate the age of the star that exploded. Using theoretical models, I am able to infer the mass from this age. I used images taken by the Hubble Space Telescope to investigate the stars responsible for producing hundreds of these remnants in the nearby galaxy NGC 6946. In addition to the remnants of supernovae, this galaxy has hosted ten observed core-collapse supernovae within the past hundred years, leading to it being referred to as the “Fireworks Galaxy”. I was able to constrain the progenitor mass distribution for 175 remnants, eight of the historically observed supernovae, as well as the progenitor of the first direct black hole formation candidate in NGC 6946. I found the distribution of progenitor masses was consistent with mass distributions measured for massive stars in other galaxies, including our own Milky Way. These new measurements allow NGC6946 to be included for the first time in statistical studies of the masses of stars that produce supernovae.

Δ⁹-tetrahydrocannabinol (THC) is the primary psychoactive compound found in Cannabis sativa. The psychoactive and cannabimimetic behaviors associated with THC have been well described as being dependent on the partial agonist activity of THC at the endogenous cannabinoid 1 receptor (CB₁R). We are investigating the direct action of THC on the medial prefrontal cortex (mPFC, a brain region primarily responsible for executive function), and the effects of adolescent THC exposure on µ-opioid receptor (MOR) expression in adult periaqueductal grey (PAG, a brain region involved in opioid-mediated pain inhibition). To increase our understanding of the cannabimimetic behavioral effects of THC, and its direct pharmacological action in the brain, it is important to map the neuro-anatomical expression of target proteins. We examined expression patterns of CB₁R and MOR in the mPFC and the PAG, respectively. To do this, we utilized a form of in situ hybridization, RNAscope. We leveraged RNAscope by preparing tissue samples from brain regions of interest for treatment with mRNA-specific probes, allowing us to target CB₁R and MOR mRNA. After a series of washes and incubations, these fluorescent probes hybridize to our target mRNAs and allow us to visualize their expression under a confocal microscope. Analysis of mRNA expression informs us on the localization of the CB1R/MOR and known neuron types within our brain regions of interest. After imaging, we are able to utilize HALO software to analyze the levels of expression and co-localization of CB₁R/MORs with neuronal markers for glutamatergic and GABAergic neuron types. By creating and optimizing a workflow for extraction, preparation, hybridization, and analysis, we determined CB₁R mRNA is primarily co-localized with glutamatergic neurons in the mPFC. Moving forward, we are utilizing this RNAscope technique to investigate differential CB₁R expression GABA interneuron subpopulations in the mPFC. (Funded by DA051558)

 Cannabis sativa is one of the most widely used drugs in the world. In humans, Cannabis sativa is commonly used to alleviate anxiety and pain, among other things, in medical and recreational contexts. In mice, intraperitoneal (i.p.) injections of its primary psychoactive compound, Δ9-tetrahydrocannabinol (THC) produce a characteristic triad of behavioral responses consisting of hypolocomotion, hypothermia, and analgesia. However, injections of THC do not accurately represent how humans typically administer THC, which primarily consists of inhalation and oral consumption. To better model a typical route of administration used by humans, we developed a voluntary oral consumption paradigm in mice whereby THC is formulated in gelatin. Following habituation, mice were given ad libitum access to THC gelatin for 2 hours. We measured the triad behaviors immediately following consumption to determine whether voluntary oral consumption of THC-gelatin using this paradigm induces acute cannabimimetic behaviors. Due to the slow pharmacokinetic activity of orally consumed THC, we measured triad responses immediately, 1 hour, and 2 hours after consumption. To compare our relative THC-gelatin-induced cannabimimetic behaviors to published data, we replicated the triad experiment and demonstrated our ability to obtain dose-dependent triad responses by using i.p. injections. At high concentrations (4mg/15mL) of THC-gelatin, cannabimimetic behavioral responses matched those of mice treated with low-dose (3 mg/kg) of THC i.p. injections. From these initial studies we conclude that development of THC-gelatin formulation triggers characteristic cannabimimetic behavioral effects in mice. These results suggests that classical THC and cannabinoid-dependent behaviors in mice can feasibly be studied with a more translational model (Funded by DA051558). Optimizing an oral administration model of cannabinoids in mice will enable future research on the pharmacology of oral cannabinoid therapeutics.