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- Title
- THE STRUCTURAL AND FOLDING CHARACTERISTICS OF THE PLASMID-ENCODED TOXIN FROM ENTEROAGGREGATIVE ESCHERICHIA COLI.
- Creator
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Scaglione, Patricia, Teter, Kenneth, University of Central Florida
- Abstract / Description
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Plasmid-encoded toxin (Pet) from enteroaggregative Escherichia coli is a member of the autotransporter subfamily termed SPATE (serine protease autotransporters of Enterobacteriaceae). Autotransporters, which are the most common Gram-negative secreted virulence factors, contain three functional domains: an amino terminal leader sequence, a mature protein or passenger domain, and a carboxy-terminal β domain. The leader sequence targets the protein to the periplasmic space and the β...
Show morePlasmid-encoded toxin (Pet) from enteroaggregative Escherichia coli is a member of the autotransporter subfamily termed SPATE (serine protease autotransporters of Enterobacteriaceae). Autotransporters, which are the most common Gram-negative secreted virulence factors, contain three functional domains: an amino terminal leader sequence, a mature protein or passenger domain, and a carboxy-terminal β domain. The leader sequence targets the protein to the periplasmic space and the β domain then forms a β-barrel pore in the outer membrane of the bacterium which allows the passenger domain to enter the external milieu. In some cases the passenger domain is cleaved from the β-barrel at the extracellular surface to release a soluble toxin. This is thought to be a self-contained process that does not require chaperones or ATP for folding and export of the passenger domain. Pet produces cytotoxic effects through cleavage of its target, the actin-binding protein α- fodrin. Pet is secreted into the extracellular environment, but its target lies within the cytosol. To reach its target, Pet moves from the cell surface to the ER where it triggers ER-associated degradation (ERAD) to enter the cytosol. ERAD is a normal cellular process in which improperly folded proteins are exported from the ER to the cytosol for degradation. Other toxins that utilize this pathway are AB toxins such as cholera toxin (CT) and ricin. The A subunits of these toxins are thermally unstable, and this facilitates their ERAD-dependent translocation into the cytosol. Pet, however, is not an AB toxin. We predict that thermal unfolding is not the mechanism Pet employs to exploit ERAD. It was necessary to purify the toxin first in order to study the structural properties and ER export of Pet. Surprisingly, purified Pet eluted as two close peaks by size exclusion chromatography. Both peaks were Pet as demonstrated through immunoblotting. The folding efficiency of autotransporters has not been extensively elucidated, and based on our purification results, we hypothesized that there is inefficiency in the folding of autotransporters, specifically Pet. A toxicity assay showed that Pet peak one did not display cytopathic activity while Pet peak two did. CD and fluorescence spectroscopy measurements also detected structural differences between the two variants of Pet and demonstrated that Pet peak one was an unfolded variant of Pet peak two. Native gel electrophoresis and biophysical measurements indicated that Pet peak one did not exist as a dimer or aggregate. Our results indicate there are two forms of Pet, and thus the folding process of autotransporters appears to be inherently inefficient. Active Pet (peak two) was used for further biophysical measurements and biochemical assays. Circular dichroism and fluorescence spectroscopy showed that the secondary and tertiary structures of Pet are maintained at physiological temperature, 37°C. Thermal unfolding of Pet occurred at temperatures above 50°C. Fluorescence quenching of Pet was also performed and demonstrated that, at 37°C, there are solvent-exposed aromatic amino acids. The slight structural alterations to Pet at physiological temperature as well as the exposed hydrophobic residues could trigger ERAD. In addition, a modeled structure of Pet revealed a hydrophobic loop which is surface-exposed and a likely target for toxin-ERAD interactions. The data suggests that translocation of Pet mediated by ERAD can occur by a mechanism different from certain AB toxins. An open, hydrophobic conformation likely triggers ERAD, but may also contribute to poor folding.
Show less - Date Issued
- 2008
- Identifier
- CFE0002399, ucf:47761
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002399
- Title
- BLOODLINES.
- Creator
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toner, Pamela, Bartkevicius, Jocelyn, University of Central Florida
- Abstract / Description
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"Bloodlines" is a collection of personal essays that focus on the process of remembering, imagining, and reflecting on the past through the lens of a perpetually shifting present. They consider situations ranging from mental and physical illnesses, from cancer to alcohol addiction, to career changes, to the often dysfunctional and displaced family ties that distance and adulthood have not severed. In "Searching," I write the narrative of the ongoing search for my birthmother, and how the...
Show more"Bloodlines" is a collection of personal essays that focus on the process of remembering, imagining, and reflecting on the past through the lens of a perpetually shifting present. They consider situations ranging from mental and physical illnesses, from cancer to alcohol addiction, to career changes, to the often dysfunctional and displaced family ties that distance and adulthood have not severed. In "Searching," I write the narrative of the ongoing search for my birthmother, and how the search complicates the relationship with my adoptive mother, who always feared she'd lose me. Similarly, "Of Flesh and Blood" recounts and negotiates how hereditary and environmental factors have shaped my identity. Loss and betrayal are weaved throughout "Flight Patterns" when I trace the links between relationships among my family and my pets. In "Signs and Stars" and "Seeing Stars," I search for ways of dealing with my cancer diagnosis and alcoholism, weaving through my past as I fight for recovery. By exploring the subjective nature of memory and circumstance through sensory, expositional, structural, and even written documentation, I have attempted to capture what is, for me, the tenuous hold on intertwined moments in time by creating a palimpsest of perspectives.
Show less - Date Issued
- 2006
- Identifier
- CFE0001053, ucf:46819
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001053
- Title
- Determining the Feasibility of using Micro Simulation to asses safety of Pedestrian Crossings.
- Creator
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Darius, Jenner, Radwan, Essam, Abou-Senna, Hatem, Abdel-Aty, Mohamed, University of Central Florida
- Abstract / Description
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For the past several decades, pedestrian safety has been an oncoming issue that has thrown the area of transportation engineering into a frenzy. Pedestrian safety has become predominantly one of the leading causes of fatalities in traffic accidents. Florida has been reported as one of the leading states in pedestrian fatalities with 2.56 fatality rate per 100,000 population and about 20 percent of all traffic fatalities in the state of Florida. Nonetheless, as research is being done and...
Show moreFor the past several decades, pedestrian safety has been an oncoming issue that has thrown the area of transportation engineering into a frenzy. Pedestrian safety has become predominantly one of the leading causes of fatalities in traffic accidents. Florida has been reported as one of the leading states in pedestrian fatalities with 2.56 fatality rate per 100,000 population and about 20 percent of all traffic fatalities in the state of Florida. Nonetheless, as research is being done and hypotheses are being calibrated and produced, there has to be a way of measuring and determining the number of pedestrian-to-vehicle conflicts without having to yet apply the system on the field without further validation. Moreover, pedestrian-to-vehicle conflicts have been a rising issue in correlation to the pedestrian fatalities. The fact that the highway safety manual has limited information about crash modification functions for pedestrian and that pedestrian fatality is a rare event, it is worthwhile identifying and adopting surrogate safety measures for pedestrian. Thus, having the capability to analyze various surrogate safety measures within the confines of micro simulation would be a great contribution to real-world application. As a result, the purpose of this thesis is to determine the feasibility of using micro simulation to assess safety of pedestrian crossings using specifically VISSIM and SSAM. During this study, a great deal of data extraction was taken from videotapes collected at nine various intersections, each with its own environmental and geometrical factors. Various parameters were taken from the different sites in order to calibrate and validate VISSIM and SSAM. The parameters included traffic and pedestrian volumes, walking speeds, crossing times, signal timings, and pedestrian-to-vehicle conflicts. During this study, an extensive amount of analysis testing was done in order to obtain the optimum threshold within various combinations of thresholds that would define the pedestrian-to-vehicle conflicts. The analysis was initiated for the time to collision (TTC) and post encroachment time (P.E.T) thresholds. This is done so that the typical scenario of an intersection can be analyzed and comparisons can be made efficiently between observed and simulated conflicts. There were 55 combinations of TTC and PET thresholds produced that were also statistically calculated using the mean absolute percent error (MAPE) in order to determine the most efficient threshold for all 9 intersections. Calibration also was done for parameters in VISSIM that included the safety distance factor (SDF) and the Add-stop distance to assess the sensitivity of these parameters in computing the number of pedestrian-to-vehicle conflicts. These thresholds and factors were used for further validation and assessment of the feasibility of the SSAM and VISSIM model. Data results displayed that the simulated conflicts and the observed conflicts illustrated reasonable correlation. However, even with the feasibility of VISSIM and SSAM being validated, there still are questions that arise pertaining to whether VISSIM and other micro simulation can assess real-world driver behavior and the unpredictability of driver maneuvering. More research with more intersections are recommended to be done.
Show less - Date Issued
- 2016
- Identifier
- CFE0006526, ucf:51379
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006526
- Title
- Dog Ownership as a Catalyst of Conflict and Relationship Maintenance in Romantic Relationships.
- Creator
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Elrick, Ashley, Weger, Harry, Miller, Ann, Hastings, Sally, University of Central Florida
- Abstract / Description
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Pets are a common aspect of life for many Americans. In 2012, 36.5% of American household owned dogs and 30.4% owned cats (American Veterinary Medical Foundation, 2012). The purpose on this study was to explore the influence of dog ownership on romantic relationships. Specifically, this thesis investigates how dog ownership acts as a catalyst of relational maintenance and conflict behavior in interactions about the couple's dog. No prior research has been conducted on the role dogs' play in...
Show morePets are a common aspect of life for many Americans. In 2012, 36.5% of American household owned dogs and 30.4% owned cats (American Veterinary Medical Foundation, 2012). The purpose on this study was to explore the influence of dog ownership on romantic relationships. Specifically, this thesis investigates how dog ownership acts as a catalyst of relational maintenance and conflict behavior in interactions about the couple's dog. No prior research has been conducted on the role dogs' play in enacting relational maintenance or conflict in romantic relationships, so it is unclear if there is an influence to the these behaviors. This study asks how dog ownership might act as a centripetal force pulling the relationship together (e.g. relational maintenance) and/or as a centrifugal force pushing the partners apart (e.g. conflict). A total of 379 participants were recruited through social media to complete a short online survey. The survey asked questions on the romantic relationship, dog ownership, conflict regarding the dog, relational maintenance activities regarding the dog, and demographics. The majority of participants reported engaging in 8 of the 24 relational maintenance activities (")often(") or (")always(") and 3 of the 30 conflict topics occurred at least one or more times. Satisfaction with the romantic relationship associated positively with partial weak and negligible correlations to the relational maintenance activities and one negligible association with a conflict topic. A thematic analysis provides details on the short answers participants provided. The results shows that dogs do provide couples opportunities for relational maintenance but also are the source of conflict. This research is the start to understanding the role of dog ownership within romantic relationship. While each couple and dog may produce different influences on the relationship, this study is the start for the investigation and provides guidance for future research.
Show less - Date Issued
- 2014
- Identifier
- CFE0005328, ucf:50533
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005328
- Title
- EVALUATING THE PERFORMANCE OF ANIMAL SHELTERS: AN APPLICATION OF DATA ENVELOPMENT ANALYSIS.
- Creator
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Heyde, Brandy, Reilly, Charles, University of Central Florida
- Abstract / Description
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The focus of this thesis is the application of data envelopment analysis to understand and evaluate the performance of diverse animal welfare organizations across the United States. The results include identification of the most efficient animal welfare organizations, at least among those that post statistics on their operations, and a discussion of various partnerships that may improve the performance of the more inefficient organizations. The Humane Society of the United States estimates...
Show moreThe focus of this thesis is the application of data envelopment analysis to understand and evaluate the performance of diverse animal welfare organizations across the United States. The results include identification of the most efficient animal welfare organizations, at least among those that post statistics on their operations, and a discussion of various partnerships that may improve the performance of the more inefficient organizations. The Humane Society of the United States estimates that there are 4000 - 6000 independently-run animal shelters across the United States, with an estimated 6-8 million companion animals entering them each year. Unfortunately, more than half of these animals are euthanized. The methods shared in this research illustrate how data envelopment analysis may help shelters improve these statistics through evaluation and cooperation. Data envelopment analysis (DEA) is based on the principle that the efficiency of an organization depends on its ability to transform its inputs into the desired outputs. The result of a DEA model is a single measure that summarizes the relative efficiency of each decision making unit (DMU) when compared with similar organizations. The DEA linear program defines an efficiency frontier with the most efficient animal shelters that are put into the model that "envelops" the other DMUs. Individual efficiency scores are calculated by determining how close each DMU is to reaching the frontier. The results shared in this research focus on the performance of 15 animal shelters. Lack of standardized data regarding individual animal shelter performance limited the ability to review a larger number of shelters and provide more robust results. Various programs are in place within the United States to improve the collection and availability of individual shelter performance. Specifically, the Asilomar Accords provide a strong framework for doing this and could significantly reduce euthanasia of companion animals if more shelters would adopt the practice of collecting and reporting their data in this format. It is demonstrated in this research that combining performance data with financial data within the data envelopment analysis technique can be powerful in helping shelters identify how to better deliver results. The addition of data from other organizations will make the results even more robust and useful for each shelter involved.
Show less - Date Issued
- 2008
- Identifier
- CFE0002101, ucf:47557
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002101
- Title
- The Interspecies Family: Attitudes and Narratives.
- Creator
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Owens, Nicole, Grauerholz, Liz, Sikorska, Elzbieta, Jasinski, Jana, University of Central Florida
- Abstract / Description
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Families are conceptualized and accomplished in increasingly diverse ways in the 21st century. A constructionist framework was utilized to examine a widespread contemporary family form, the interspecies family. This mixed-method approach relied on both quantitative survey data and qualitative interview data. First, survey data from the 2006 Constructing the Family Survey were analyzed to understand who in America counts pets as family. Many social demographics were associated and predicted...
Show moreFamilies are conceptualized and accomplished in increasingly diverse ways in the 21st century. A constructionist framework was utilized to examine a widespread contemporary family form, the interspecies family. This mixed-method approach relied on both quantitative survey data and qualitative interview data. First, survey data from the 2006 Constructing the Family Survey were analyzed to understand who in America counts pets as family. Many social demographics were associated and predicted counting pets as family but gender was one of the strongest associations. However, marital status moderated the relationship between gender and counting pets as family at a statically significant level. Men who are currently or have ever been married are less likely to count pets as family than never married men. Second, I conducted 32 semi-structured, in-depth interviews with 39 people during 2014-2015 in Central Florida to understand how people who count their cats and dogs as family members narrate this process. Narrative strategies documenting exactly how cats and dogs become family members within interspecies family narratives include: time-related narratives, timeless narratives, and patchwork narratives. Additionally, all participants considered their cats and dogs family but only some of them felt like pet-parents. Narratives of childless participants are compared with narratives of parents to examine the impact of family form on the construction of pet parenting narratives. Implications for the family change literature are discussed.
Show less - Date Issued
- 2015
- Identifier
- CFE0005984, ucf:50780
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005984
