Davidson Science on Display
May 14, 2001
Dozens of young Davidson scientists displayed the results of their research at the annual year-end Student Research Symposium recently. Their 62 projects in biology, chemistry, physics, and psychology were summarized and professionally mounted on posters that were displayed throughout the Watson Life Sciences Building and Dana Science Building. Students stood by their posters and explained their work to friends and faculty who circulated through the displays. Summarizing research on posters gives students a convenient way of presenting their findings, and is the most common means of presenting work at scientific meetings. Their work represented efforts conducted as part of classroom assignments, independent study projects, and collaborative research with faculty members. Some students had already presented their work at scientific meetings, and some of it will be published in science journals. The symposium highlights the importance Davidson places on undergraduate research as a pedagogy for learning, and provided students with a means of sharing their accomplishments with others. Some of the students and the abstracts of their projects are listed below:
Synthesis of Celebrex Analogs: An Undergraduate Organic Experiment
The goal of this project was to design a Chemistry 202 lab for the synthesis of Celebrex analogs. Celebrex is a newly introduced anti-inflammatory drug with selective enzyme inhibiting capabilities. We followed the procedures outlined in a paper recently published by Searle scientists in the Journal of Medicinal Chemistry. This paper listed several possible routes to synthesize Celebrex analogs. Criteria for this synthesis lab include reproducibility, high yields, and crystallinity of products in addition to a specified length of the experiment. This multi-step synthesis reinforces the concepts of carbonyl chemistry, aromaticity, and heterocyclic chemistry while meeting the criteria for undergraduate laboratory reactions. First, we discerned which reactions listed in the paper could be run easily and quickly in an undergraduate lab. After examining several unsuccessful reactions, we found that acetophenone derivatives react readily with amide acetals. Condensation of these products with an aryl hydrazine affords Celebrex analogs.
Development of a Chemistry 121 Laboratory to Determine the Solubility Product Constant of Silver Chloride Using Ion Chromatography
The purpose of this project was to design a student laboratory experiment for Chemistry 121 that would investigate the solubility properties of silver chloride, a highly insoluble inorganic salt, using ion chromatography. Ion chromatography is an important method of analysis used in analytical chemistry. The Dionex ion chromatograph used in the Chemistry 121 course can detect the presence of anions in solution and quantify the concentrations using calibration curves. This method of analysis was used to determine the solubility product constant (Ksp) of silver chloride. Extensions of this lab demonstrating the common ion effect and activities were also studied.
Polymer Scaffolds in Tissue Engineering
The shortage of organ donations leaves many patients with end stage organ failure with no solution and left on long waiting lists each year. Alternate means of treatment are beginning to be researched, specifically tissue engineering of functional organs. Polymer scaffolds have been designed that provide a three dimensional support for cells to proliferate and differentiate into a functioning tissue. This scaffold is a foundation for tissue growth, but also biodegrades in the body once the tissue is functional in the body and has its own cellular support. The polymeric materials concentrated on for use as scaffolds are poly(glycolic acid), poly(L-lactic acid), and mainly their copolymer (PLGA). The copolymer degradation rate can be tailored by varying the concentration of each monomer to acquire a desirable time to biodegrade. The scaffold must have a large enough surface area to allow sufficient room for cell attachment that is required for tissue growth. The formation of pores in the polymer increases sites for cell attachment, and the pore size and porosity can be controlled to give the structure varying physical characteristics such as strength and elasticity. The pores are interconnected to allow for essential nutrient and gas exchange for all cells in the scaffold. These characteristics are required for a tissue to grow and differentiate into a functioning organ. This technology has been applied to engineering of bone, cartilage, liver, and bladder tissues, and is a promising new solution to organ failure.
The Application of Polyimides in High Temperature Matrix Composites and their Performance Characterization in Aerospace Environments
Polyimides are strong and very heat and chemical resistant polymers. Because of these characteristics, they often replace glass and metals in many demanding industrial applications. One such application are polymer matrix composites used in aeronautical applications in and around jet and rocket engines. With polymers such as polyimides, polymer matrix composites have become advantageous because of their lightweight, high strength and stiffness, and thus their reduced need for machining. Aerospace applications involve combined stress, time, temperature, moisture, chemical and atmospheric service environment exposures on the performance of polymer matrix composites. Current studies are being performed on aerospace durability of various potential polyimide resin systems. The goal of this project is to better understand the ability to tailor the high temperature.
The Use of Polydioxanone in Pediatric Surgical Applications
Polymeric material decisions for use in pediatric surgical applications must take into account the developing immune system as well as the physical growth of the patient. In response to these concerns, the use of polydioxanone--a derivative of the glycolide family--has been examined in various pediatric applications such as an absorbable suture material and a component of absorbable prosthetic ring for valvular replacement. Studies of polydioxanone in pediatric applications have found this biomaterial exhibits good handling properties, less intense inflammatory response, and excellent biocompatability with reliable absorption. These factors contribute to its preferred use in applications that require a combination of extended support and absorption as well as sensitivity to pediatric needs.
The Enhanced Interfacial Biocompatibility Between Living Cells and PMMA Modified with Phosphorylcholine in Corneal Contact Lens Applications
Visual acuity, which is a discomfort of the eye due to the extended wearing of contact lenses, may be the result of calcium and protein deposits on the lens surface. These deposits contribute to cell adhesion to the lens. It is known that a polymeric substance with hydrophilic surface properties resists the interaction with and deposition of proteins and lipids from the surrounding biological environment, thus inhibiting the overall adhesion of cells to the lens. Through the surface modification of PMMA by the use of a plasma glow discharge technique, a thin film of substrate containing desired functional groups can be bound to the surface. It has been discovered that by incorporating phosphorylcholine into the substrate, the relative rate of cell adhesion on the lens is greatly reduced. Phosphorylcholine is a component of a naturally occurring difatty-acid derivative, lecithin, which is found to be immunologically inert. Phosphorylcholine is very polar and therefore hydrophilic due to the phosphoric acid groups that are deprotonated at biological pH. These findings indicate that through the phosphorylcholine surface modification of PMMA, biocompatibility of the corneal lenses is markedly improved due to reduced cell adhesion to lens.
Quantum Transitions of Cesium and Rubidium Via Non Linear Laser Spectroscopy
Nonlinear laser spectroscopy was used to study electronic transitions in Cesium and Rubidium atoms. A powerful Nd-YAG pulsed laser was frequency doubled to produce high-energy green light, which was used to pump a tunable dye laser. This light was then focused on a collection of Cesium atoms. The intense laser light is capable of inducing multi-photon absorption through an intermediate energy level. The ionized atoms produced a current allowing us to measure the S and D energy levels from n=11 to approximately n=40. We measured the nonlinear relationship between the power of the laser and the intensity of the signal. We also observed how the density of the Cesium affected the measured current. In a second experiment, we measured the hyperfine splitting of atomic energy levels due to interaction of the magnetic dipole moment of the nucleus and the orbital moment of valence electrons. A tunable diode laser emitted light that was directed through a cell containing the isotopes Rubidium 85 and Rubidium 87. We measured the splitting between nuclear angular momentum quantum number I= 1/2 and I=3/2 in the 5S1/2 ground state as the laser was tuned across these absorption energies. Because of the motion of the atoms, we concluded that Doppler broadening masked all other hyperfine structure.
Organic Residue Analysis of Bronze Age Pottery Sherds by Gas Chromatography-Mass Spectrometry (GC-MS)
Chemical analysis of organic matter found in various archaeological relics, such as soil, human remains and pottery containers, can be used to deduce clues about the cultural and economic pursuits of ancient populations. In particular, ceramic artifacts are especially useful for study because the organic residues are well preserved, as they can be absorbed into the ceramic matrix. Lipids and other organic matter can be extracted from the pottery sherds and subjected to GC-MS analysis to separate and identify organic residues in the sherds. In this experiment, we analyzed organic components that were contained in pottery artifacts from the early Minoan site of Chrysokamino on the northeast coast of Crete, as well as those from other Bronze Age sites. Each pottery sherd was ground, extracted with organic solvents, treated to convert fatty acids to more volatile esters and evaporated before the extract was subjected to GC-MS analysis. Many peaks on the chromatograms were successfully identified, but very few were representative of organic matter typically found in pottery sherds. Many of the peaks observed were contaminant peaks such as plasticizers and silyl derivatives; however, we were able to identify organic components such as benzophenone and camphor in some sherds, but other components are yet to be identified. In addition, the development of this procedure will enable the analysis of more pottery sherds in the future.
Herpetofaunal Biodiversity of the Ramah Creek Conservation Easement
Reptiles and amphibians compose a large portion of the biodiversity in almost every habitat in the southeastern United States. Therefore, the status of the amphibians and reptiles can often be used as an indicator of habitat quality. Many reptile and amphibian declines have been documented over the past ten years, and habitat destruction is often the main reason for these declines. Proper land management is the key to preserving habitat, and knowledge of the habitatıs biodiversity is the first step in this process. The purpose of our project is to document the biodiversity of reptiles and amphibians on the Ramah Creek Conservation Easement Area, east of Huntersville. To effectively document as many species as possible, we have employed a variety of techniques such as minnow traps, coverboards, and general searches of the area. The Ramah Creek Conservation Easement potentially has fifty-two species of amphibians and reptiles, and thus far, twenty species have been observed/captured on the easement. Especially important are the wetlands that serve as breeding grounds for many frogs and toads in addition to marbled salamandesr and red-spotted newts. This summer I will continue to document various amphibians and reptiles of the area, and evaluate the status of the timber rattlesnake (Crotalus horridus) on the easement.
The Effects of AIT-082 on Behavioral Recovery in Unilateral Entorhinal Cortex Lesion Induced Memory Loss in Rats: An Alzheimer's Disease Model
Alzheimer's disease is a devastating neurological disorder marked by a progressive decline in the function of memory. Unilateral entorhinal cortex lesions in rats serve as an excellent model of Alzheimer's disease because these animals exhibit the same type of memory impairments as those associated with Alzheimer's disease. In addition, the sprouting responses to this type of lesion are involved in different extents to behavioral recovery. AIT-082 is a drug that has been found to facilitate the production of molecules known to promote neuronal recovery after injury, yet unlike these molecules in can cross the blood-brain barrier. AIT-082 has also been found to improve behavior in mice with age-related memory deficits. The current study tests AIT-082's ability to improve behavioral recovery in rats on a Y-maze task following a right unilateral entorhinal cortex lesion. Results indicate that AIT-082 serves as a factor during the time course of recovery. The drug was also seen as a factor mediating behavioral recovery during the physiologically significant testing days 6-12 (8-14 post-lesion) which corresponds in time to the behaviorally significant synaptic sprouting of the crossed temporodentate pathway. AIT-082 also improved behavior over saline control, and was not different from sham control, in the number of days necessary to reach behavioral criterion performance post-surgery. Therefore, AIT-082 appears to be mildly effective in improving working memory in mild to moderate cases of an Alzheimer's disease model. Future studies should focus on the exact mechanisms by which AIT-082 exhibits its neuroprotective and memory enhancement effects.
The Effects of Exercise, Intrinsic Efficacy, and Nociceptive Intensity on Opioid Antinociception in a Rodent Tail Withdrawal Assay
Endurance exercise has been clinically shown to increase blood plasma levels of -endorphin, an endogenous neurotransmitter active at opioid receptors and capable of producing antinociceptive effects. The purpose of this study was to examine the influence of exercise, intrinsic efficacy, and nociceptive intensity on the antinociceptive effects of mu opioids in a warm-water tail withdrawal procedure. Subjects in this experiment were 12 Long-Evans rats, randomly assigned to either exercise (n=6) or sedentary groups (n=6). All housing conditions were identical between the two groups except that exercise rats were given free access to a running wheel inside their cages. In a warm-water, tail-withdrawal procedure, rats were restrained and the latencies to remove their tails from low (50° C) and high (55° C) temperature water were recorded following cumulative doses of high efficacy (morphine, levorphanol), intermediate efficacy (buprenorphine), and low efficacy (butorphanol, nalbuphine) opioids. At baseline, excercising rats showed significantly greater tail-withdrawal latencies than sendentary rats. Exercise rats were also less sensitive to the antinociceptive effects of all opioids tested than sedentary rats, and these differences were most pronounced when low efficacy drugs were tested. In drug combination tests, butorphanol and nalbuphine functioned as antagonists under conditions in which they failed to produce maximal antinociceptive effects when administered alone. When housing conditions were reversed, sensitivity to the antinociceptive effects of buprenorphine was enhanced in previously exercising rats and reduced in previously sedentary rats. Collectively, these data suggest that endogenous opioid release induced by chronic exercise led to the development of tolerance to the effects of a variety of mu opioids.
Polymers used in Time-release Oral Drug Delivery: A General Overview and a Detailed Examination of the Oral Delivery of Oxycodone
This is a review of oral drug delivery and the polymers employed to achieve time-release delivery. A brief general history of time-release oral drug delivery through polymer matrices will be included in order to provide background on the topic. A summary of the different factors that contribute to time-release characteristics will be evaluated, including typical polymers used, morphology of drug tablets, and kinetics of drug release. Current advanced systems used for oral drug delivery will be presented, including hydrophilic amorphous polymers, microcrystalline cellulose, ethylcellulose, hydrocolloid drug delivery with late burst release, and glassy polymers in hydrophilic matrices. There will be a focused examination of the oral time-released delivery of oxycodone. Oxycodone, marketed as Oxycontin®, is a potent opiod analgesic prescribed to patients with chronic pain. Oxycodone, delivered through its polymeric coating, provides pain relief for up to twelve hours, a unique and heavily desired characteristic for patients with chronic pain. A detailed description of the polymers used, the production of the tablets, and the pharmacokinetics of drug release will be presented.
Female Body Size as a Function of Race on Television Sitcoms
Is there a difference among the body sizes of African and Anglo American characters on evening television sitcoms? Little research as focused on the answer to this question. This study is important, because it bridges the gap in the current literature on body image and body size and explores new prospects in psychology. Several studies have concluded that, compared to Anglo American women, African American women accept a larger ideal body size, report greater body satisfaction, and are less likely to engage in dieting to lose weight. The present study investigated the body sizes of African American and Anglo American female characters on television sitcoms. Using a numerical scale, two raters assessed the body sizes of each television character. As hypothesized, this study discovered a difference in body size between African American and Anglo American female characters. The raters scored the African American characters higher than the Anglo American characters, illustrating that on television sitcoms, the female African American characters have a larger body size than the female Anglo American characters. This study suggests that body size of female characters on television sitcoms is congruent with the idealized body size of the race of the character, suggesting different aesthetic standards and ideals across different ethnic backgrounds. Television is perpetuating an ideal of thinness to Anglo American women, which could influence body image and rates of eating disorders among Anglo American women.
Davidson is a highly selective independent liberal arts college for 1,600 students. Since its establishment in 1837, the college has graduated 23 Rhodes Scholars and is consistently ranked among the top liberal arts colleges in the country by U.S. News and World Report magazine. Davidson recently launched "Let Learning Be Cherished," a $250 million campaign in support of student financial assistance, academic resources, and community life.