Organizational Unit:
Undergraduate Research Opportunities Program
Undergraduate Research Opportunities Program
Permanent Link
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
ArchiveSpace Name Record
Publication Search Results
Now showing
1 - 8 of 8
-
ItemLateral gene transfer of pandemic Vibrio parahaemolyticus genomic island genes(Georgia Institute of Technology, 2008-12-15) Silberger, Daniel JamesVibrio parahaemolyticus is an emerging enteric pathogen. The O3:K6 serotype has become pandemic, and the genome has been sequenced for the RIMD2210633 strain of this serotype (20). The thermostabile direct hemolysin (tdh), thermostabile related hemolysin (trh), and two distinct Type III Secretion Systems (T3SS) have been implicated in virulence. Deletion studies have determined that the T3SS alone are sufficient to induce eukaryotic cell apoptosis. The T3SS loci are found within two separate genomic islands. Because genomic islands are known to be disseminated by Lateral Gene Transfer (LGT), we examined the distribution of the pandemic genomic island genes among clinical and environmental V. parahaemolyticus isolates and also among closely-related environmental Vibrio spp. using primers designed to amplify hemolysins and T3SS effectors previously characterized for V. parahaemolyticus strain RIMD2210633 (23). We also examined the distribution of a hypothetical bacteriocin, encoded by vpa1263, within another genomic island that is similar to the bacteriocins produced by Escherichia coli. Preliminary screens for the bacteriocin gene suggest that many clinical strains and some environmental strains contain vpa1263. PCR screens for the T3SS effector genes have shown that 22% of closely-related environmental Vibrio spp. contain at least one T3SS1 or one T3SS2 effector gene. Sequencing of housekeeping genes is ongoing to confirm these findings.
-
ItemDensity-dependent Stiffness in Petiole Biomechanics(Georgia Institute of Technology, 2008-05-05) Wilson, ChristinaMorphological features of plants vary with increasing size. This relationship between different physical characteristics and size is referred to as allometry. Recently allometric research focused on plants and in particular plant leaves due to their importance in nutrient flow and gas exchange. Allometric plant research aims to enhance our understanding of the ontogeny of plants and offers a tool for ecological modeling. Previous allometric models have glanced over the influence of biomechanics on leaf form and function. This research will test if density-dependent stiffness of petioles is variable or if it scales with leaf mass. In order to test the variance of stiffness in leaf petioles, Young s modulus (E) was measured by modeling the petioles as simply loaded beams. Young s modulus was shown to vary among different species, even those of the same genus. Density-dependent stiffness varied with leaf size for some herbaceous species but not for other woody tree species. Future research should investigate the biomechanical role of a possible redistribution of structural tissue and how this rearrangement would affects petiole stiffness and overall petiole function.
-
ItemRotifer Ecotoxicology: Behavioral Avoidance of Toxicants(Georgia Institute of Technology, 2008-05-05) Weigel, Emily G.Previous rotifer ecotoxicology studies have shown varied effects of sublethal concentrations of hormones and metals on species but have largely ignored toxicant effects on behavior. Given the importance of chemical cues for mating, grazing, and predator avoidance, the phenomenon of behavioral response to pollutants is a critical topic impacting rotifer survival and reproduction. Dual- and tri-chamber test slides similar to Y-tubes were developed to test rotifer behavioral responses to sublethal concentrations of several toxicants. Rotifers were placed in a start chamber between a control chamber and test chamber containing a toxicant, and after fifteen minutes, rotifer distribution in all chambers was recorded. No significant distributional effects were observed for cadmium (2μg/L), pentochlorophenol (2μg/L), flutamide (8μg/L) nor progesterone (8μg/L). Significant deviation from a random distribution was recorded for selenium (2μg/L), lead (8μg/L), and rotifer conditioned medium. In addition, significant avoidance was found for copper (2μg/L) and mercury (0.2μg/L), even in tests with the start chamber containing the toxicant. These data suggest that rotifers can detect and avoid certain toxicants at sublethal levels. Avoidance often occurs at levels below published lethal concentrations (LC50s) on which many water quality criteria are based. Avoidance can alter rotifer survival and reproduction, leading to reductions in rotifer abundance and energy transfer to higher trophic levels.
-
ItemFörster Resonance Energy Transfer and Fluorescence Quenching Based Low-density Lipoprotein Probes for Visualizing Transcytosis(Georgia Institute of Technology, 2008-05-05) Fay, Nicole C.Transcytosis is the process by which macromolecules are transported across a polarized cell. It is one of the main methods of nutrient absorption from the blood stream as well as the only means past the blood brain barrier. Insight into the transcytic route has enormous medical potential where drug delivery methods stand to be significantly optimized. Despite the importance of this fundamental biological process, the mechanism of transcytosis is not well understood. Previously, fluorescence microscopy has allowed the tracking of fluorescently labeled low-density lipoprotein (LDL) intracellularly. However, this labeled LDL is not able to distinguish LDL particles undergoing transcytosis versus degradation. LDL is an ideal cargo for observing intracellular processes due to its vital role in transporting cholesterol for cell membrane fluidity. In order to differentiate transcytosis from degradation, I have produced two probes sensitive to degradation. The two probes are based on the principles of 1.) Förster resonance energy transfer (FRET) and 2.) fluorescence quenching. LDL degradation of the FRET-based or the fluorescence-quenching-based probe results in a significant increase in fluorescent activity. I have used several methods to assess the functionality of these probes including fluorescence measurements of detergent and enzyme degradations, SDS-PAGE analysis of degradations, and in vivo flow cytometry. Additionally, I have optimized the growth conditions for maintaining polarity in a cell line (MDCK) known to undergo transcytosis. The time and location of LDL degradation in a cell can be resolved through the use of these probes. Future work includes single-particle tracking of LDL as it is being degraded versus actively transcytosing across a cell layer. This process is critical to understanding transcytosis as well as LDL regulation in the human body.
-
ItemSustained Delivery of Thermally Stabilized chABC by Lipid Microtubules(Georgia Institute of Technology, 2008-05-05) Kumar, NathanOur knowledge of spinal cord injury repair is broadening with the developing technology for nerve regeneration and drug delivery. In this paper we discuss the current capabilities for spinal cord repair as well as those that are in development. We develop protocols for determining the thermal stability of chondroitinase ABCI and its ability to be implanted into a microtubule-hydrogel drug delivery vehicle as well as the release profile that results from this implantation. After the use of sodium dodecyl electrophoresis, we determined that the disaccharide trehalose has the capacity to thermally stabilize our therapeutic enzyme in vitro. We also determined that the microtubules are effective for sustaining the release of our enzyme while the hydrogel is effective for localizing its effects. The deactivation profile was experimentally quantified to allow for complete diffusion of our enzyme over the course of a two-week implantation. Our thermally stabilized enzyme and drug delivery system can be used for the purpose of facilitating nerve regeneration at the site of an injury.
-
ItemRotifer Ecotoxicology: Behavioral Avoidance of Toxicants(Georgia Institute of Technology, 2008-05-05) Weigel, Emily GracePrevious rotifer ecotoxicology studies have shown varied effects of sublethal concentrations of hormones and metals on species but have largely ignored toxicant effects on behavior. Given the importance of chemical cues for mating, grazing, and predator avoidance, the phenomenon of behavioral response to pollutants is a critical topic impacting rotifer survival and reproduction. Dual- and tri-chamber test slides similar to Y-tubes were developed to test rotifer behavioral responses to sublethal concentrations of several toxicants. Rotifers were placed in a start chamber between a control chamber and test chamber containing a toxicant, and after fifteen minutes, rotifer distribution in all chambers was recorded. No significant distributional effects were observed for cadmium (2μg/L), pentochlorophenol (2μg/L), flutamide (8μg/L) nor progesterone (8μg/L). Significant deviation from a random distribution was recorded for selenium (2μg/L), lead (8μg/L), and rotifer conditioned medium. In addition, significant avoidance was found for copper (2μg/L) and mercury (0.2μg/L), even in tests with the start chamber containing the toxicant. These data suggest that rotifers can detect and avoid certain toxicants at sublethal levels. Avoidance often occurs at levels below published lethal concentrations (LC50s) on which many water quality criteria are based. Avoidance can alter rotifer survival and reproduction, leading to reductions in rotifer abundance and energy transfer to higher trophic levels.
-
Item[PSI+] Prion Induction within the Yeast Saccharomyces Genera(Georgia Institute of Technology, 2008-05-05) Gyoneva, StefkaPrions are self-perpetuating protein aggregates that cause neurodegenerative diseases in mammals and carry heritable traits in yeast. Yeast [PSI+] prion is the prion isoform of Sup35 protein, an essential translation termination factor. The [PSI+] prion state can be induced in [psi-] cells by the overexpression of the full-length Sup35 protein, or only a certain portion of the protein. However, this induction requires the presence of a second yeast prion known as [PIN+]. While [PSI+] is present in lab cultures of S. cerevisiae, it has not been reported in any other Saccharomyces species. In this study, we attempted to induce [PSI+] in S. paradoxus and S. bayanus, two close relatives of S. cerevisiae. As non-cerevisiae species of Saccharomyces lack other known prions, we employed a new induction approach based on the overproduction of a chimeric protein composed of portions of Sup35 and Human Progesterone Receptor 6.6 (HPR6.6). This construct can induce [PSI+] in the absence of other endogenous prions. We next engineered S. paradoxus and S. bayanus strains with markers that allowed for prion studies in these species. The novel Sup35-HPR6.6 fusion constructs led to [PSI+] induction in S. paradoxus, the sister species of S. cerevisiae, but not in the more distantly related S. bayanus. We also showed that the prion isoform of Sup35 from S. paradoxus, previously known to produce only unstable prions in the heterologous S. cerevisiae system, can generate mitotically stable prions in the homologous S. paradoxus system. Finally, we propose a model which explains the possible role of the Sup35 and HPR6.6 fusion constructs in [PIN+]-independent [PSI+] induction.
-
ItemChemical manipulation of dental patterning in Malawi cichlids(Georgia Institute of Technology, 2008-05-05) Bloomquist, Ryan F.A dynamic model for odontogenesis is lacking. Cichlids serve as superior organisms for studies in tooth development because of diversity in tooth shape, size, number, number of rows, all of which undergo continuous replacement, as well as the possession of a second set of toothed jaws, within the posterior pharynx. Through in situ hybridization we have characterized basic patterns of odontogenesis in cichlids that are conserved throughout vertebrates. We have used the teratogens cyclopamine and SU5402 to reduce the function of Shh and Fgf protein, respectively with a time and dose dependence. Cyclopamine trials indicate that Shh is necessary to pattern the dentition and that its expression in the first tooth is essential, as is its interaction with tooth spacing genes in the initiation of a periodic pattern mechanism. Members of the Fgf family are required for proper replacement cycles, possibly through stem cell interactions.