Matching Items (292)
Description
Rabies disease remains enzootic among raccoons, skunks, foxes and bats in the United States. It is of primary concern for public-health agencies to control spatial spread of rabies in wildlife and its potential spillover infection of domestic animals and humans. Rabies is invariably fatal in wildlife if untreated, with a non-negligible incubation period. Understanding how this latency affects spatial spread of rabies in wildlife is the concern of chapter 2 and 3. Chapter 1 deals with the background of mathematical models for rabies and lists main objectives. In chapter 2, a reaction-diffusion susceptible-exposed-infected (SEI) model and a delayed diffusive susceptible-infected (SI) model are constructed to describe the same epidemic process -- rabies spread in foxes. For the delayed diffusive model a non-local infection term with delay is resulted from modeling the dispersal during incubation stage. Comparison is made regarding minimum traveling wave speeds of the two models, which are verified using numerical experiments. In chapter 3, starting with two Kermack and McKendrick's models where infectivity, death rate and diffusion rate of infected individuals can depend on the age of infection, the asymptotic speed of spread $c^\ast$ for the cumulated force of infection can be analyzed. For the special case of fixed incubation period, the asymptotic speed of spread is governed by the same integral equation for both models. Although explicit solutions for $c^\ast$ are difficult to obtain, assuming that diffusion coefficient of incubating animals is small, $c^\ast$ can be estimated in terms of model parameter values. Chapter 4 considers the implementation of realistic landscape in simulation of rabies spread in skunks and bats in northeast Texas. The Finite Element Method (FEM) is adopted because the irregular shapes of realistic landscape naturally lead to unstructured grids in the spatial domain. This implementation leads to a more accurate description of skunk rabies cases distributions.
ContributorsLiu, Hao (Author) / Kuang, Yang (Thesis advisor) / Jackiewicz, Zdzislaw (Committee member) / Lanchier, Nicolas (Committee member) / Smith, Hal (Committee member) / Thieme, Horst (Committee member) / Arizona State University (Publisher)
Created2013
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
Bacteriophage (phage) are viruses that infect bacteria. Typical laboratory experiments show that in a chemostat containing phage and susceptible bacteria species, a mutant bacteria species will evolve. This mutant species is usually resistant to the phage infection and less competitive compared to the susceptible bacteria species. In some experiments, both susceptible and resistant bacteria species, as well as phage, can coexist at an equilibrium for hundreds of hours. The current research is inspired by these observations, and the goal is to establish a mathematical model and explore sufficient and necessary conditions for the coexistence. In this dissertation a model with infinite distributed delay terms based on some existing work is established. A rigorous analysis of the well-posedness of this model is provided, and it is proved that the susceptible bacteria persist. To study the persistence of phage species, a "Phage Reproduction Number" (PRN) is defined. The mathematical analysis shows phage persist if PRN > 1 and vanish if PRN < 1. A sufficient condition and a necessary condition for persistence of resistant bacteria are given. The persistence of the phage is essential for the persistence of resistant bacteria. Also, the resistant bacteria persist if its fitness is the same as the susceptible bacteria and if PRN > 1. A special case of the general model leads to a system of ordinary differential equations, for which numerical simulation results are presented.
ContributorsHan, Zhun (Author) / Smith, Hal (Thesis advisor) / Armbruster, Dieter (Committee member) / Kawski, Matthias (Committee member) / Kuang, Yang (Committee member) / Thieme, Horst (Committee member) / Arizona State University (Publisher)
Created2012
Description
In vertebrate outer retina, changes in the membrane potential of horizontal cells affect the calcium influx and glutamate release of cone photoreceptors via a negative feedback. This feedback has a number of important physiological consequences. One is called background-induced flicker enhancement (BIFE) in which the onset of dim background enhances the center flicker response of horizontal cells. The underlying mechanism for the feedback is still unclear but competing hypotheses have been proposed. One is the GABA hypothesis, which states that the feedback is mediated by gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter released from horizontal cells. Another is the ephaptic hypothesis, which contends that the feedback is non-GABAergic and is achieved through the modulation of electrical potential in the intersynaptic cleft between cones and horizontal cells. In this study, a continuum spine model of the cone-horizontal cell synaptic circuitry is formulated. This model, a partial differential equation system, incorporates both the GABA and ephaptic feedback mechanisms. Simulation results, in comparison with experiments, indicate that the ephaptic mechanism is necessary in order for the model to capture the major spatial and temporal dynamics of the BIFE effect. In addition, simulations indicate that the GABA mechanism may play some minor modulation role.
ContributorsChang, Shaojie (Author) / Baer, Steven M. (Thesis advisor) / Gardner, Carl L (Thesis advisor) / Crook, Sharon M (Committee member) / Kuang, Yang (Committee member) / Ringhofer, Christian (Committee member) / Arizona State University (Publisher)
Created2012
Enhancing motivation for physical activity to reduce fall risk among community dwelling older adults
Description
Unintentional falls among community dwelling older adults are a common, serious and potentially preventable public health problem. In the United States, the annual incidence of fall related injuries per 100,000 persons was 4,616 in 2001, rising to 5,252 in 2008. The annual incidence of fall related deaths per 100,000 persons was 29.3 in 2000, rising to 41.86 in 2006. Older adults are particularly vulnerable to falls as they age. Potential consequences include fractures, emergency room, hospital and nursing home admissions, dependence, confusion, immobilization, depression, and death. Significant modifiable fall risk factors include muscle weakness, gait problems, and balance problems. While researchers have demonstrated the positive effects of balance and leg-strengthening physical activities, the majority of older adults do not engage in them, and the rate of falls continues to increase. Older adults participate in regular physical activity and fitness activities less often than younger populations; disparities are greater among those who are poor and living in rural communities. While knowledge about causes, risk factors, and efficacious physical activity to prevent falls has grown exponentially in the last several decades, bridging the gap between research and practice continues to be a challenge. As a strategy to address the gap between research and practice, this feasibility study utilized a tested theory, the wellness motivation theory, to address motivation for behavioral change in combination with instruction for physical activities proven to reduce fall risk. The study sample included rural, community dwelling older adults at risk of falls. The study included an innovative mobile computer to measure physical activity behavior and to augment motivational content of the intervention. Specific aims of this feasibility study were to: (a) examine the acceptability, demand, and implementation of the wellness motivation intervention (WMI) as well as the technology augmenting the WMI; and (b) evaluate the efficacy of the WMI to influence awareness of social contextual resources, behavioral change processes, physical activity, and fall risk. The WMI delivered in combination with proven multicomponent balance and strength activities was feasible and effectively increased motivation for behavioral change (social support from friends, awareness of social contextual resources, behavioral change processes) and physical activity behavior, and decreased fall risk among rural, community-dwelling older adults at risk of falls in this study. This study is the first step in a program of research focusing on enhancing motivation for physical activity that reduces falls and frailty among older adults.
ContributorsMcMahon, Siobhan (Author) / Fleury, Julie (Thesis advisor) / Belyea, Michael (Committee member) / Shearer, Nelma (Committee member) / Wyman, Jean (Committee member) / Hekler, Eric (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
I conducted a qualitative, comparative study on the nursing education systems in the United Kingdom and the United States, focusing on two universities—Arizona State University in Phoenix, Arizona and Leeds Beckett University in Leeds, England. The goals of my thesis included comparing the educational, economic, and cultural aspects of the countries and how those aspects impact nursing students on both sides of the pond. The educational and economic aspects were compared by utilizing existing literature and open data sources such as the university websites and publications from comparative education journals, while the cultural differences were evaluated by conducting short, one-on-one interviews with students enrolled in the Adult Health courses at both universities. The findings from the interviews were transcribed and coded, and findings from the sites were compared. While there is an extensive amount of research published regarding comparative education, there has not been much published comparing these developed countries. While there is a significant difference in the structure and cost of the nursing programs, there are more similarities than differences in culture between nursing students interviewed in the US and those interviewed in the UK.
ContributorsTahiliani, Shreja (Author) / Hagler, Debra (Thesis director) / Allen, Angela (Committee member) / Arizona State University. College of Nursing & Healthcare Innovation (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The goal of this creative project is to explain the different roles of advanced practice nursing as well as the role of a registered nurse. Advanced practice nursing roles include Certified Nurse Practitioner, Certified Registered Nurse Anesthetist, Certified Clinical Nurse Specialist, and Certified Nurse Midwife. The role of the registered nurse is included in this website because this role is the foundation for becoming an advanced practice nurse and is an equally important role. The target audience for the website is potential nursing students, current nursing students, and licensed nurses who desire to advance their career and are looking for more information about each role. This comprehensive website includes the scope of practice, salary, educational programs, and an interview with a nurse in each role. The description of each advanced practice role includes audio and visual aids to appeal to different types of learners. In depth education regarding advanced practice nursing roles will make current and future nurses more aware of the endless possibilities of a career in nursing. Nurses provide education to patients every day, but there is rarely adequate education provided to nurses regarding their profession or professional advancement opportunities. Nursing is a patient-focused career and sometimes nurses forget to focus on their own personal growth while caring for others. This one-stop website promotes nurse to nurse education by thoroughly explaining each advanced practice role. All of the information in this website is publically available through the internet and this website is meant solely for educational purposes.
ContributorsThompson, Rachel (Co-author) / Banchik, Jennifer (Co-author) / Peterson, Katherine (Thesis director) / Kriz, Lindsey (Committee member) / Spahr, Nancy (Committee member) / School of Community Resources and Development (Contributor) / School of Social Transformation (Contributor) / Arizona State University. College of Nursing & Healthcare Innovation (Contributor) / T. Denny Sanford School of Social and Family Dynamics (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
Colorectal cancer (CRC) is the third most prevalent form of cancer in both genders and second highest cause of cancer-related death in the United States. Despite the availability of preventative CRC screening, Latinos as a group are of particular concern for CRC as they tend to have a lower screening rate, contributing to the possibility of late-stage diagnosis or even death. However, little is known about the perceptions of CRC screening and factors which contribute to beliefs about CRC in Latinos. Most studies are quantitative and rarely include a qualitative approach focusing on cultural aspects and communication with physicians. The purpose of this study was to explore participants' perceived facilitators and barriers to CRC screening, as well as perspectives on physician recommendation and fatalism, using a qualitative approach. A convenience and snowball sampling were used to collect the data. Eight English-speaking Latino individuals (M age=56 years; 75% female) in the Phoenix, Arizona area were invited to 60-90 minute in-depth interviews on perceptions of the colorectal cancer screening process. Ten major themes emerged from the interviews: (1) lacking awareness and knowledge of CRC screening, (2) attitude toward CRC and screening, (3) availability of preventive care, (4) physician trust, (5) fear, (6) desire for increased information, (7) personal learning, (8) lifestyle factors, (9) cultural impact, and (10) willingness to change lifestyle. Results indicated varying levels of perceived knowledge of colorectal cancer, little perceived risk of diagnosis, desire for more information, and a high level of physician trust. Implications for nursing included increased need for CRC screening educational resources, as well as further investigation of the influence of fatalistic belief in CRC screening compliance for the Latino population.
ContributorsMagdaleno, Claire Rose (Author) / Kim, Sunny (Thesis director) / McNulty, Julie (Committee member) / Arizona State University. College of Nursing & Healthcare Innovation (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12