Matching Items (98)
Description
Pathogenic Gram-negative bacteria employ a variety of molecular mechanisms to combat host defenses. Two-component regulatory systems (TCR systems) are the most ubiquitous signal transduction systems which regulate many genes required for virulence and survival of bacteria. In this study, I analyzed different TCR systems in two clinically-relevant Gram-negative bacteria, i.e., oral pathogen Porphyromonas gingivalis and enterobacterial Escherichia coli. P. gingivalis is a major causative agent of periodontal disease as well as systemic illnesses, like cardiovascular disease. A microarray study found that the putative PorY-PorX TCR system controls the secretion and maturation of virulence factors, as well as loci involved in the PorSS secretion system, which secretes proteinases, i.e., gingipains, responsible for periodontal disease. Proteomic analysis (SILAC) was used to improve the microarray data, reverse-transcription PCR to verify the proteomic data, and primer extension assay to determine the promoter regions of specific PorX regulated loci. I was able to characterize multiple genetic loci regulated by this TCR system, many of which play an essential role in hemagglutination and host-cell adhesion, and likely contribute to virulence in this bacterium. Enteric Gram-negative bacteria must withstand many host defenses such as digestive enzymes, low pH, and antimicrobial peptides (AMPs). The CpxR-CpxA TCR system of E. coli has been extensively characterized and shown to be required for protection against AMPs. Most recently, this TCR system has been shown to up-regulate the rfe-rff operon which encodes genes involved in the production of enterobacterial common antigen (ECA), and confers protection against a variety of AMPs. In this study, I utilized primer extension and DNase I footprinting to determine how CpxR regulates the ECA operon. My findings suggest that CpxR modulates transcription by directly binding to the rfe promoter. Multiple genetic and biochemical approaches were used to demonstrate that specific TCR systems contribute to regulation of virulence factors and resistance to host defenses in P. gingivalis and E. coli, respectively. Understanding these genetic circuits provides insight into strategies for pathogenesis and resistance to host defenses in Gram negative bacterial pathogens. Finally, these data provide compelling potential molecular targets for therapeutics to treat P. gingivalis and E. coli infections.
ContributorsLeonetti, Cori (Author) / Shi, Yixin (Thesis advisor) / Stout, Valerie (Committee member) / Nickerson, Cheryl (Committee member) / Sandrin, Todd (Committee member) / Arizona State University (Publisher)
Created2013
Description
The study of bacterial resistance to antimicrobial peptides (AMPs) is a significant area of interest as these peptides have the potential to be developed into alternative drug therapies to combat microbial pathogens. AMPs represent a class of host-mediated factors that function to prevent microbial infection of their host and serve as a first line of defense. To date, over 1,000 AMPs of various natures have been predicted or experimentally characterized. Their potent bactericidal activities and broad-based target repertoire make them a promising next-generation pharmaceutical therapy to combat bacterial pathogens. It is important to understand the molecular mechanisms, both genetic and physiological, that bacteria employ to circumvent the bactericidal activities of AMPs. These understandings will allow researchers to overcome challenges posed with the development of new drug therapies; as well as identify, at a fundamental level, how bacteria are able to adapt and survive within varied host environments. Here, results are presented from the first reported large scale, systematic screen in which the Keio collection of ~4,000 Escherichia coli deletion mutants were challenged against physiologically significant AMPs to identify genes required for resistance. Less than 3% of the total number of genes on the E. coli chromosome was determined to contribute to bacterial resistance to at least one AMP analyzed in the screen. Further, the screen implicated a single cellular component (enterobacterial common antigen, ECA) and a single transporter system (twin-arginine transporter, Tat) as being required for resistance to each AMP class. Using antimicrobial resistance as a tool to identify novel genetic mechanisms, subsequent analyses were able to identify a two-component system, CpxR/CpxA, as a global regulator in bacterial resistance to AMPs. Multiple previously characterized CpxR/A members, as well as members found in this study, were identified in the screen. Notably, CpxR/A was found to transcriptionally regulate the gene cluster responsible for the biosynthesis of the ECA. Thus, a novel genetic mechanism was uncovered that directly correlates with a physiologically significant cellular component that appears to globally contribute to bacterial resistance to AMPs.
ContributorsWeatherspoon-Griffin, Natasha (Author) / Shi, Yixin (Thesis advisor) / Clark-Curtiss, Josephine (Committee member) / Misra, Rajeev (Committee member) / Nickerson, Cheryl (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2013
Description
Food system and health characteristics were evaluated across the last Waorani hunter-gatherer group in Amazonian Ecuador and a remote neighboring Kichwa indigenous subsistence agriculture community. Hunter-gatherer food systems like the Waorani foragers may not only be nutritionally, but also pharmaceutically beneficial because of high dietary intake of varied plant phytochemical compounds. A modern diet that reduces these dietary plant defense phytochemicals below levels typical in human evolutionary history may leave humans vulnerable to diseases that were controlled through a foraging diet. Few studies consider the health impact of the recent drastic reduction of plant phytochemical content in the modern global food system, which has eliminated essential components of food because they are not considered "nutrients". The antimicrobial and anti-inflammatory nature of the food system may not only regulate infectious pathogens and inflammatory disease, but also support beneficial microbes in human hosts, reducing vulnerability to chronic diseases. Waorani foragers seem immune to certain infections with very low rates of chronic disease. Does returning to certain characteristics of a foraging food system begin to restore the human body microbe balance and inflammatory response to evolutionary norms, and if so, what implication does this have for the treatment of disease? Several years of data on dietary and health differences across the foragers and the farmers was gathered. There were major differences in health outcomes across the board. In the Waorani forager group there were no signs of infection in serious wounds such as 3rd degree burns and spear wounds. The foragers had one-degree lower body temperature than the farmers. The Waorani had an absence of signs of chronic diseases including vision and blood pressure that did not change markedly with age while Kichwa farmers suffered from both chronic diseases and physiological indicators of aging. In the Waorani forager population, there was an absence of many common regional infectious diseases, from helminthes to staphylococcus. Study design helped control for confounders (exercise, environment, genetic factors, non-phytochemical dietary intake). This study provides evidence of the major role total phytochemical dietary intake plays in human health, often not considered by policymakers and nutritional and agricultural scientists.
ContributorsLondon, Douglas (Author) / Tsuda, Takeyuki (Thesis advisor) / Beezhold, Bonnie L (Committee member) / Hruschka, Daniel (Committee member) / Eder, James (Committee member) / Arizona State University (Publisher)
Created2012
Description
This dissertation is intended to tie together a body of work which utilizes a variety of methods to study applied mathematical models involving heterogeneity often omitted with classical modeling techniques. I posit three cogent classifications of heterogeneity: physiological, behavioral, and local (specifically connectivity in this work). I consider physiological heterogeneity using the method of transport equations to study heterogeneous susceptibility to diseases in open populations (those with births and deaths). I then present three separate models of behavioral heterogeneity. An SIS/SAS model of gonorrhea transmission in a population of highly active men-who-have-sex-with-men (MSM) is presented to study the impact of safe behavior (prevention and self-awareness) on the prevalence of this endemic disease. Behavior is modeled in this examples via static parameters describing consistent condom use and frequency of STD testing. In an example of behavioral heterogeneity, in the absence of underlying dynamics, I present a generalization to ``test theory without an answer key" (also known as cultural consensus modeling or CCM). CCM is commonly used to study the distribution of cultural knowledge within a population. The generalized framework presented allows for selecting the best model among various extensions of CCM: multiple subcultures, estimating the degree to which individuals guess yes, and making competence homogenous in the population. This permits model selection based on the principle of information criteria. The third behaviorally heterogeneous model studies adaptive behavioral response based on epidemiological-economic theory within an $SIR$ epidemic setting. Theorems used to analyze the stability of such models with a generalized, non-linear incidence structure are adapted and applied to the case of standard incidence and adaptive incidence. As an example of study in spatial heterogeneity I provide an explicit solution to a generalization of the continuous time approximation of the Albert-Barabasi scale-free network algorithm. The solution is found by recursively solving the differential equations via integrating factors, identifying a pattern for the coefficients and then proving this observed pattern is consistent using induction. An application to disease dynamics on such evolving structures is then studied.
ContributorsMorin, Benjamin (Author) / Castillo-Chavez, Carlos (Thesis advisor) / Hiebeler, David (Thesis advisor) / Hruschka, Daniel (Committee member) / Suslov, Sergei (Committee member) / Arizona State University (Publisher)
Created2012
Description
Hepatitis C virus (HCV) is a globally prevalent infection which is a main contributor to the global burden of liver disease. Due to its ability to establish a chronic infection, and the lack of usefulness of traditional neutralizing antibody vaccine design in producing a protective immune response, a preventative vaccine has been notoriously difficult to produce. To overcome this, a vaccine using non-structural protein 3 (NS3) as a target to elicit a T cell specific immune response is thought to be a possible strategy for eliciting a protective immune response against hepatitis C infection. In this paper, a recombinant strain of measles virus (MV) that expresses HCV NS3 protein was analyzed. The replication fitness of this recombinant virus also indicates that this construct replicates at a higher rate than parental measles strain. It is also demonstrated through western blot analysis of protein expression and immunofluorescence that this recombinant virus expresses both the inserted HCV NS3 protein, as well as native measles proteins.
ContributorsWoell, Dana Marie (Author) / Reyes del Valle, Jorge (Thesis director) / Nickerson, Cheryl (Committee member) / Julik, Emily (Committee member) / Barrett, The Honors College (Contributor) / Department of Chemistry and Biochemistry (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2015-05
Description
Due to persistent undernutrition in India and the increased demands placed on a woman’s body during childbearing and lactation, the Indian government has implemented a program to provide supplemental nutrition packets to women in rural India. This study examines the factors influencing uptake of nutritional packets by lactating mothers in southern, rural Rajasthan. Women were recruited from 65 villages in Rajasthan, India (n=149, minimum of 2 per village) to evaluate the relationship of nutrition packet uptake and two factors--education levels and distance to the health center.
Level of education had little impact on whether or not women received the nutrition packet. Of those women with no education, 63.1% received the packet. Of those with any education, 63.9% got the packet.
In contrast, distance was strongly correlated with whether or not women received the packet. For example, of the women living within 200 meters of the health center, 93.2% received a nutrition packet. Of the women living between 250 meters and one kilometer of the health center, 68.4% received a nutrition packet. Of the women living over one kilometer from the health center, only 25% received a nutrition packet. The relationship between uptake of packets and women’s perception of distance to the health center was also explored. Out of 50 women who did not receive the packet, all of the women who said there was no health center in their village did live more than one kilometer from a health center. Of the women who lived between 250 meters and one kilometer from the health center, 40% felt it was too far. Of the women who lived more than a kilometer from the health center, 66.7% felt it was too far and 29.6% said there was no health center in their village. Again, it does not appear that ‘too far’ is just a default reason for women, but that actual distance, more so than education, is a major contributing factor in their ability to take the nutrition packet. These findings suggest that improving access to supplemental nutrition packets at the village level may increase uptake by the women.
Level of education had little impact on whether or not women received the nutrition packet. Of those women with no education, 63.1% received the packet. Of those with any education, 63.9% got the packet.
In contrast, distance was strongly correlated with whether or not women received the packet. For example, of the women living within 200 meters of the health center, 93.2% received a nutrition packet. Of the women living between 250 meters and one kilometer of the health center, 68.4% received a nutrition packet. Of the women living over one kilometer from the health center, only 25% received a nutrition packet. The relationship between uptake of packets and women’s perception of distance to the health center was also explored. Out of 50 women who did not receive the packet, all of the women who said there was no health center in their village did live more than one kilometer from a health center. Of the women who lived between 250 meters and one kilometer from the health center, 40% felt it was too far. Of the women who lived more than a kilometer from the health center, 66.7% felt it was too far and 29.6% said there was no health center in their village. Again, it does not appear that ‘too far’ is just a default reason for women, but that actual distance, more so than education, is a major contributing factor in their ability to take the nutrition packet. These findings suggest that improving access to supplemental nutrition packets at the village level may increase uptake by the women.
ContributorsJeffers, Eva Marie (Author) / Hruschka, Daniel (Thesis director) / Maupin, Jonathan (Committee member) / Cook, Jeffrey (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2015-05
Description
Clean water for drinking, food preparation, and bathing is essential for astronaut health and safety during long duration habitation of the International Space Station (ISS), including future missions to Mars. Despite stringent water treatment and recycling efforts on the ISS, it is impossible to completely prevent microbial contamination of onboard water supplies. In this work, we used a spaceflight analogue culture system to better understand how the microgravity environment can influence the pathogenesis-related characteristics of Burkholderia cepacia complex (Bcc), an opportunistic pathogen previously recovered from the ISS water system. The results of the present study suggest that there may be important differences in how this pathogen can respond and adapt to spaceflight and other low fluid shear environments encountered during their natural life cycles. Future studies are aimed at understanding the underlying mechanisms responsible for these phenotypes.
ContributorsKang, Bianca Younseon (Author) / Nickerson, Cheryl (Thesis director) / Barrila, Jennifer (Committee member) / Ott, Mark (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
2015 marks the deadline for the UN Millennium Development Goal 5 to reduce global maternal mortality rate (MMR) by 75% since 1990. As of 2015, MMR has only been reduced by 45%. Many international organizations claim that more medically trained midwives can meet global maternal health care needs. This study investigates two major questions. What is the role of midwives in diverse international maternal healthcare contexts? How do midwives in these different contexts define their roles and the barriers to providing the best care for women? From May to August 2015, I conducted over 70 interviews with midwives in Netherlands, Sweden, Rwanda, Bangladesh, Australia and Guatemala, interviewing between 6 and 13 midwives from each country. The majority of midwives defined their roles as supporting women's individual capacities and power through normal birth, and knowing when to refer when high-risk complications arise. Although thematic barriers vary by country, midwives in all countries believed that maternal healthcare can be improved by increased collaboration between midwives and other health care professionals, better access to culturally appropriate services, and greater public awareness of the role of midwives.
ContributorsCarson, Anna Elizabeth (Author) / Hruschka, Daniel (Thesis director) / Maupin, Jonathan (Committee member) / School of International Letters and Cultures (Contributor) / School of Human Evolution and Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
How are perceptions of morality and disgust regarding meat consumption related to each other? Which factor is more salient in determining one's willingness to eat the meat of a specific animal? How do these answers vary across religious groups? This study investigates the ways that concepts like morality and disgust are related to food preferences and hopes to shed light on the mechanisms that enforce culturally sanctioned food taboos. The study compares 4 groups of people in the U.S.: Christians (n = 39), Hindus (n = 29), Jews (n = 23), and non-religious people (n = 63). A total of 154 participants were given surveys in which they rated their feelings about eating various animals. Data from Christian and non-religious groups exhibited similar patterns such as a high likelihood of eating a given animal when starving, while results from Jews and Hindus were consistent with their religion's respective food taboos. Despite these differences, morality and disgust are strongly correlated with one another in almost all instances. Moreover, morality and disgust are almost equally important considerations when determining willingness to eat when starving.
ContributorsParekh, Shaili Rajul (Author) / Hruschka, Daniel (Thesis director) / Jacobs, Mark (Committee member) / Barrett, The Honors College (Contributor) / School of Nutrition and Health Promotion (Contributor) / School of Human Evolution and Social Change (Contributor) / Hugh Downs School of Human Communication (Contributor)
Created2014-12
Description
The United States is experiencing an increase in the prevalence and influence of complementary and alternative medicine (CAM) in patient healthcare, reflecting the increasingly positive public and professional attitudes on the use of CAM therapies. Despite the growing presence of CAM in U.S. healthcare, there are still many barriers to integration. This study aims to reveal the attitudes of conventional, integrative and CAM practitioners concerning the major challenges of CAM's integration, explore their proposed solutions, and reveal any discrepancies in these attitudes among different types of practitioners. Twenty-eight practitioners were interviewed on the challenges in the five facets of CAM's integration: integration into hospitals, integration into medical schools, insurance coverage for CAM, licensing & regulation of CAM practitioners, and clinical research in CAM. The overall positive attitudes on the benefits of CAM's integration support previous research on the subject; however, the conventional practitioners were unable to extend these benefits to real-world application, and they were unaware of many of the challenges facing CAM's integration. The CAM practitioners attributed many of the problems facing integration to the inability of CAM's philosophy to comply with the current ideology of medical academia, health insurance model, and laws that govern the licensing and regulation of medical practitioners. The CAM and integrative practitioners perceived there to be a large resistance from conventional practitioners, specifically concerning the integration of CAM into education, providing insurance coverage for CAM, and the licensing and regulation of CAM practitioners. They attributed this to a perceived lack of research on safe and effective treatments in CAM. The conventional practitioner responses reflected this weariness of treatment effectiveness in their responses. However, the CAM and integrative practitioners believed these claims to be largely inaccurate, and constructed by the influence and manipulation of large-scale medical corporations and organizations. The participants believed that more evidence-based research in CAM, and increased public awareness in CAM therapies will force conventional practitioners to increase their knowledge in CAM, helping to alleviate their fears and skepticism of CAM therapies. By easing these concerns, dialogue can occur among practitioners of different modalities that will help to ensure a smooth integration of CAM and will raise the quality of patient healthcare by providing safe and effective resources for alternate forms of treatment.
ContributorsJohnston, Shantele Hanna Lee (Author) / Hruschka, Daniel (Thesis director) / Hurlbut, Ben (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2014-05