Biological Science
http://hdl.handle.net/10211.3/10211.8_13
2024-03-29T09:53:57ZEffects of Nitrogen Availability and Climate on Hermes Copper Butterfly (Lycaena hermes) Habitat in Southern California
http://hdl.handle.net/10211.3/218065
Effects of Nitrogen Availability and Climate on Hermes Copper Butterfly (Lycaena hermes) Habitat in Southern California
Malter, Liberty
As environmental conditions continue to change, phytophagous insects are under increasing selective pressure when identifying and choosing quality host plants. The Hermes copper butterfly (Lycaena hermes) is a rare species endemic to San Diego County and parts of northern Baja California. The small butterfly population is a fascinating topic since the host plant, Rhamnus crocea, extends well beyond the range of the insect. Based on what is known about plant herbivore interactions it is possible that variation in plant chemistry is contributing to small population sizes and a limited distribution. Plant tissue chemistry is affected by environmental variations, such as chronic nitrogen deposition, temperature, and precipitation. We hypothesized that plant secondary compounds are likely to vary significantly within and outside of the Hermes copper butterfly range, trends in secondary compounds will be affected by variations in climate, such as temperature and precipitation, and spatial variations in plant secondary compounds will be affected by N availability. Leaf tissue from current and historical Hermes copper habitat sites were analyzed and plant secondary compounds classes were identified. Soil samples were collected in May 2018 to measure extractable N, soil moisture, total N and C, and pH. N availability did not have a significant effect on plant secondary compounds within and outside of the range of the butterfly. However, it was found that climate conditions did have a significant effect on these compounds. The lack of a N effect on plant secondary compounds in the host plant suggests that allocation of resources within the plant may not be significantly influenced by changes in N availability, but may be affected by changes in temperature and precipitation.
2020-11-05T00:00:00ZInvestigating the Role of Genome Repair Mechanisms in the Instability of Myotonic Dystrophy Type 2-Causing CCTG Repeats
http://hdl.handle.net/10211.3/217184
Investigating the Role of Genome Repair Mechanisms in the Instability of Myotonic Dystrophy Type 2-Causing CCTG Repeats
Papp, David
Genome maintenance is essential for the healthy development and survival of all organisms. Various molecular mechanisms are in place to prevent and repair mutations to the genome. However, some of these mechanisms lead to instability of expansion-prone microsatellite DNA repeats, which are the cause of over 40 genetic diseases in humans. While trinucleotide repeats (TNRs) have been well studied, information on tetranucleotide repeats is sparse. CCTG repeat instability in the CNBP gene leads to Myotonic Dystrophy Type II (DM2), a neuromuscular disease. In this study, we utilized Saccharomyces cerevisiae cells containing an engineered URA3 reporter with CCTG repeats to investigate the effect of genetic and environmental factors on large-scale CCTG repeat contractions. First, we identified several candidate genes involved in DNA replication, repair, and recombination events, as well as osmotic and replicative stressors for use in the study. Then we constructed knockout and separation-of-function mutants with the use of CRISPR-Cas9. Finally, we conducted assays to investigate the mutation rate of CCTG repeats in these mutants. Our results showed a significant effect of several proteins involved in DNA repair, such as Sgs1, Msh3, Msh6, Mlh1, Mlh2, Rad51, and Rad52, among other mutants, on CCTG repeat contraction rates. Though the helicase Srs2 did not show a significant effect on CCTG contractions, treatment with replicative stressors revealed a protective effect. Overall, however, the results suggest that homologous recombination during repair of double-strand breaks and mitotic crossover events is one of the major drivers of large-scale CCTG repeat contractions. We propose that the results of our study will aid in the development of therapeutic solutions for DM2 patients, that reduce instability of or induce contraction in CCTG repeats.
2020-08-11T00:00:00ZImpact of Rapamycin on Secondary Infection of Laboratory Mice (Mus musculus) with the Intestinal Nematode Heligmosomoides bakeri
http://hdl.handle.net/10211.3/217180
Impact of Rapamycin on Secondary Infection of Laboratory Mice (Mus musculus) with the Intestinal Nematode Heligmosomoides bakeri
Banuelos, Ashley
The National Institutes of Health is studying rapamycin for over-the-counter use, as it may aid in slowing biological ageing. However, due to the immunosuppressive effects of rapamycin, over-the-counter use may be premature. Parasitic infections occur less frequently in the United States than in other countries; however, it is a reality that citizens are infected with parasites. With the current idea of providing people with a readily available dietary supplement to slow biological aging that also is a known immunosuppressant, it is important to discover the possibilities of rapamycin causing adverse effects on combating a parasitic worm infection. I studied the effects rapamycin ingestion on host susceptibility with associated immune measures, host food consumption and host body mass using a laboratory mouse-intestinal nematode model. Mice (Mus musculus) were fed a diet supplemented with rapamycin or a control diet and then, after a secondary infection with the intestinal nematode Heligmosomoides bakeri, we measured infection intensity, eosinophil production, and morphology of one primary lymphoid organ (thymus) and one secondary lymphoid organ (spleen). Impressively, mice fed rapamycin retained nearly eight times more worms than mice fed the control diet. Spleen mass reflected this difference in infection intensity, where infected mice had spleens that were 223% larger, however, spleen mass was not affected by diet. Mice fed rapamycin had 22% smaller thymi than those fed the control diet and infected mice had 32% smaller thymi than uninfected mice. These changes in thymi mass are in contrast with number of live thymocytes, where I found a significant interaction between diet and infection because uninfected rapamycin fed mice retained more live thymocytes than other experimental groups. However, mice that were infected and consumed rapamycin had the least number of thymocytes, which may be correlated with smaller thymi for those on rapamycin and mice that were infected. For eosinophil count, the expected increase with H. bakeri infection depended on the interaction between infection, diet and time. As expected, body mass increased over time during the experiment. Mouse initial and final body mass was not affected by diet or infection. Food intake overtime was largely similar among experimental groups. Taken together, this experiment showed that ingestion of rapamycin greatly suppressed the ability of mice to clear a secondary exposure of an intestinal parasitic nematode. This result should be considered when developing rapamycin as an over-the-counter supplement.
2020-08-10T00:00:00ZThe Regulation of Dendritic Epidermal T Cell Function by C-C Motif Chemokine Ligand 20
http://hdl.handle.net/10211.3/217156
The Regulation of Dendritic Epidermal T Cell Function by C-C Motif Chemokine Ligand 20
Bshara-Corson, Savannah
The skin is the largest organ in the body and provides a first line of defense from foreign pathogens. Many different cell types within the skin work together to aid in wound repair when damage occurs. Dendritic epidermal T cells (DETC) play key roles in tissue repair by secreting growth factors, cytokines, and chemokines to facilitate keratinocyte proliferation and regulate inflammatory responses following tissue damage. Cellular receptors such as the γδ T cell receptor (TCR) are necessary for regulating DETC in vivo. C-C Chemokine Receptor 6 (CCR6) regulates dermal γδ T cell migration to the epidermis during tissue damage and infection, however, little is known about how this receptor works with the TCR to regulate DETC. Previous work in our laboratory identified CCR6 as a receptor that is downregulated by murine DETC during obesity and type 2 diabetes. The major ligand for CCR6 is C-C Motif Chemokine Ligand 20 (CCL20), which induces cellular migration. In this study, I investigated the role of CCR6 in regulating DETC function in the murine epidermis. DETC were harvested and stimulated in the presence or absence of CCL20 and anti-CD3 to determine how CCL20 regulates DETC cytokine and chemokine production using flow cytometry, Luminex analysis and immunofluorescent microscopy. Our studies indicate that CCR6 is expressed by DETC upon activation, allowing the identification of 3 subpopulations: CCR6- CD25-, CCR6- CD25+ and CCR6+ CD25+ cells. While dermal γδ T cells that express CCR6 show the ability to migrate toward CCL20, our data suggests that CCL20 prevents DETC from becoming migratory. Beyond migration, CCL20 stimulates DETC to produce several proinflammatory cytokines and chemokines including IP-10, IL-6, MIP-2 and Eotaxin. In addition, CCL20 costimulates TCR activation in DETC with the production of IL-2, IL-6, TNF-α, MCP-1, MIP-2 and Eotaxin along with several cytokines and chemokines at lower levels. Our studies validate that CCL20 induces TNF-α and IL-17A production by DETC which may play key roles in wound healing. Our findings indicate DETC express CCR6 upon TCR activation and CCL20 ligation can differentiate distinct subsets of DETC that may have Th17 functions. Future studies will be conducted on murine models with obesity and type 2 diabetes to discern how CCL20 is involved with proinflammatory cytokines in regards to wound healing.
2020-08-06T00:00:00Z