The principal objective of this project was to determine whether Hedera helix was distributed randomly or exhibited host preferences within Drayton Wood, Norwich. 200 random tree samples >10cm diameter were studied. Of these, the CBH (circumference breast height), bark texture, abundance of H. helix and growth form were recorded. The percentage of ground covered by H. helix around the base of the sample trees was also recorded. Finally, the distance of the sample trees from the outer reaches of the wood and canopy cover were measured.Hedera helix was not distributed over potential host trees homogenously, but exhibited host associations. Quercus robur, Crataegus monogyna and Pinus sylvestris tree species were found to have a higher abundance of H. helix than expected by chance, whereas Acer pseudoplatanus and Betula pendula were found to have less H. helix vines than expected. Furthermore juvenile and mature vines were not distributed equally. Acer pseudoplatanus hosted more juveniles and less adults than expected, whereas Quercus robur and Pinus sylvestris hosted less juveniles and more mature vines than expected. Vines were not distributed independently of host size. Those trees <100cm CBH had a lesser stem abundance than expected, whereas those vines >100cm CBH had a greater stem abundance than expected. Host preference was exhibited for those large CBH trees with rough bark as opposed to large CBH trees with smooth bark. There was a higher abundance of H. helix (ground and trunk cover) with distance from the edge. Ground cover was greater under those trees hosting H. helix than those not supporting H. helix.Light did not play a major role in the distribution and abundance of H. helix (ground cover and trunk cover).Key Words: host selectivity, host size, bark texture, ground cover, location, light.

Cyclodextrins are well known for their ability to encapsulate molecules and have captured the attention of scientists for many years. This ability alone makes cyclodextrins attractive for study, research, and applications in many fields including food, cosmetics, textiles, and the pharmaceutical industry. In this thesis, we specifically look at the ability of the three native cyclodextrins, alpha, beta, and gamma cyclodextrin (α-CD, β-CD, and γ-CD, respectively), to encapsulate the drug molecule, quinine, a small hydrophobic, lipophilic molecule used to treat malaria, leg cramps, and other similar conditions. This encapsulation process is driven by the molecular interactions, which have been studied by NMR techniques at different temperatures (288 K, 293 K, 298 K, 303 K, 308 K) and pH values (7.4, 11.5). These factors (temperature and pH) influence these molecular interactions, which in turn significantly affects the entire encapsulation process. Detailed studies of the influences of temperature and pH on the interactions that drive the encapsulation may suggest some new directions into designing controlled drug release processes. Results obtained throughout the course of this work indicate that β-CD is the best native cyclodextrin to bind quinine, and that binding is best at pH = 11.5. It was found that temperature does not significantly affect the binding affinity of quinine to either α-CD, β-CD, or γ-CD.

At Santa Margarita Ranch, California, oak mistletoe (Phoradendron villosum) parasitizes valley oak and blue oak but cannot be found growing on coast live oak despite its abundance and ability to parasitize coast live oak in other areas. It seems as though this species of mistletoe is specializing on certain host oak trees, but the mechanisms of this specialization are unknown. In order to investigate this pattern, we utilized a type of machine learning in GIS called supervised classification as well as a reciprocal transplant study in the field. The three species of oak trees were classified with 87% accuracy using drone imagery and 95% accuracy using open source NAIP imagery. This classification technique could be applied to the whole state of California as long as ground truth points for each species were collected. This could be extremely useful for large scale forest management projects and ecological questions. Unfortunately, the classifier was unsuccessful at distinguishing mistletoe from host and so the number of mistletoe on each host could not be quantified using this technique. The reciprocal transplant study involved collecting mistletoe fruit from individuals growing on each of the three hosts and experimentally applying them back onto all three hosts. This allowed us to test whether there are host races of mistletoe that specialize at growing on certain hosts. We found that seeds from each host origin germinated equally well regardless of where they were dispersed, and seeds survived best on coast live oak, regardless of where they originated from. Based on these results, there must be some mechanism, other than host races, that explains the lack of mistletoe on coast live oaks at Santa Margarita Ranch. Future projects should investigate whether evidence for host races can be found at a later stage of seedling development and the roll of bird dispersers in creating the pattern.

<p>  </p> <p>Predators and parasites are critical, interconnected members of the community and have the potential to influence host populations. Predators, in particular, can have direct and indirect impacts on disease dynamics. By removing hosts and their parasites, predators alter both host and parasite populations and ultimately shape disease transmission. Our ability to accurately predict disease dynamics requires understanding the ecological effects of predation on prey and host densities and its role in the coevolution of host resistance and parasite virulence. While the impact of predators on disease dynamics has received considerable attention, research has focused on selective predation on infected prey. There is, however, substantial evidence that some predators avoid infected prey, preferentially attacking uninfected individuals. Such different strategies of prey selectivity by predators modulate host-parasite interactions, changing the fitness payoffs both for hosts and their parasites. I use empirical results and theoretical predictions as a framework to discuss the mechanisms by which predation for infected versus uninfected individuals can affect disease dynamics. First, by integrating hypotheses from behavioral ecology and disease ecology, I outlined novel perspectives that complement the prevailing view of selective predation of infected individuals (Chapter 1). Then, exploring short-term ecological outcomes and long-term host-parasite coevolution, I investigated patterns of <em>Daphnia dentifera</em> host population densities and host susceptibility over several generations under different types of predation pressure, including selective predation on infected and uninfected individuals (Chapter 2). Finally, building on the results of this research, I developed a high school project-based lesson plan that facilitates the instruction of the nature of science, implementing on-going ecological research in activities to improve student learning based on a constructivist approach to learning (Chapter 3). Together this research highlights the differential ecological and evolutionary outcomes of host-parasite interactions under varying community contexts.</p>

Past literature on transnational repression underscore the significant gap in examining how the relationship between the origin country and the host country influences instances of transnational repression. To fill this gap, this study is bringing in the neglected role of democratic host states by exploring: Why do certain democratic host states encounter significant incidents of transnational repression on their soil while others do not? This essay demystifies the concept of "relationship" and examines whether states, driven by their self-interest, tend to "overlook" transnational repression. This exploration involves testing the hypothesis: An observed comprehensive relationship between the host and origin countries leads to increased transnational repression as the host country tends to “overlook” these incidents. Through a Structured Focused Comparison, the originating country Russia, and the hosting countries Switzerland and the United Kingdom are compared. The findings do not fully support the hypothesis. However, several intriguing discoveries are found that need further investigation.

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The threat from infectious diseases dates as far back as prehistoric times. Pathogens continue to pose serious challenges to human health. The emergence and spread of diseases such as HIV/AIDS, Severe Acute Respiratory Syndrome (SARS), avian influenza, and the threats of bioterrorism have made infectious diseases major public health concerns. Despite many successes in the discovery of anti-infective medications, the treatment of infectious diseases faces serious challenges, which include (i) the emergence and reemergence of infectious pathogens, (ii) the ability of pathogens to adapt and develop resistance to drugs, and (ii) a shortage in the development and discovery of new anti-infective drugs. Host-Oriented Broad-Spectrum (HOBS) treatments have the promising potential to alleviate these problems. The HOBS treatment paradigm focuses on finding drug targets in human host that are simultaneously effective against a wide variety of infectious agents and toxins. In this dissertation, we present a computational approach to predict HOBS treatments by integrative analysis of three types of data, namely, (a) gene expression data representing host responses upon infection by a pathogen, (b) annotations of genes to pre-defined biological pathways and processes, and (iii) genes that are targets of known drugs. Our methods combine gene set-level enrichment with biclustering. We applied our approach to a compendium of gene expression data sets derived from host cells exposed to bacterial or to fungal pathogens, to functional annotation data from multiple databases, and to drug targets from DrugBank. We present putative host drug targets and drugs with extensive support in the literature for their potential to treat multiple bacterial and fungal infections. These results showcase the potential of our computational approach to predict HOBS drug targets that may be effective against two or more pathogens. Our study takes a clean-slate approach that promises to yield unsuspected or unknown associations between pathogens and biological processes, and thus discern candidate gene/proteins to be further probed as HOBS targets. Furthermore, by focusing on host responses to pathogens as captured by transcriptional data, our proposed approach stimulates host-oriented drug target identification, which has potential to alleviate the problem of drug resistance. / Ph. D.

Thesis advisor: Tim van Opijnen / Although vaccines and antibiotics have been historically successful in combating bacterial infections, limited vaccine coverage and the rise of antibiotic resistance emphasize the need to develop alternative, broadly effective, and/or targeted treatment strategies to reduce the health burden of bacterial infections. Rather than relying on therapeutics solely targeting the bacterial pathogen, such as standard antibiotics, therapies that simultaneously focus on host responses are emerging. In this thesis, we propose 'host-informed therapies' (HITs) in two categories: those that aid patients with fully functional immune systems and those that aid patients with perturbed immune processes, as promising alternative or adjunctive treatment strategies for bacterial infections. The host-pathogen interaction during infection is a highly dynamic process between diverse bacterial pathogens and hosts with varying degrees of susceptibility. Systems biology approaches have provided an understanding of host-pathogen parameters globally through the detection of putative biomarkers for diagnosis and identification of critical interactions to discover novel drug targets. However, there remains a gap in understanding bacterial pathogenesis in the context of designing novel host-informed therapies. Here, we use Streptococcus pneumoniae, the gram-positive pathogen responsible for the majority of bacterial respiratory tract infections worldwide, as a case study to: (1) Generate a genome-wide map of bacterial immune (complement) evasion targets to design novel host-informed therapies, (2) generate a dual host/pathogen transcriptome map to identify signatures of infection outcome, and (3) validate signatures of bacterial antibiotic tolerance in a mouse lung infection model. Overall, this work exemplifies how systems biology methods can elucidate the intricacies of bacterial pathogenesis but, more importantly, aid in the target identification, validation, and design of antibacterial host-informed therapies. / Thesis (PhD) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.