Biology

The Effect of Exogenous Fibroblast Growth Factor on Retinal Neuron Dendritic Development  in Xenopus laevis Tadpoles

Nathaniel Leachman, Paul Niemczewski, Sarah McFarlane, and Barbara Lom

Fibroblast growth factor-2 (FGF-2) is expressed in the developing tadpole visual system where it regulates retinal neuron fate as well as retinal ganglion cell (RGC) axon extension and target recognition.  Since both FGF-2 and FGF receptors are expressed during the period when RGCs elaborate their dendritic arbors in the retina, FGF-2 is spatially and temporally available to play a role in sculpting dendritic morphology. To determine if FGF-2 influences retinal ganglion cell dendritic arborization, exogenous FGF-2 or epidermal growth factor (EGF) were injected into developing retinae at the time of dendritic initiation.  RGC dendrites were allowed to develop, then their arbors were visualized by retrograde transport of rhodamine dextran to allow analysis of arbor morphology.  Results of this analysis indicate that FGF-2 treatment significantly enhanced the highest branch order of RGCs compared to both untreated and EGF-treated controls.  Further, FGF-2’s ability to enhance branch order occurred without a concomitant enhancement of primary dendrites.  Thus, FGF-2 may sculpt the morphology of developing RGC dendritic arbors.

The Effects of Urbanization and Habitat Fragmentation on Box Turtle (Terrapene carolina) Biology

Lauran M. Halpin and Michael E. Dorcas

            The eastern box turtle (Terrapene carolina) is commonly found in both developed and undeveloped areas.  However, little is known about the effects of urbanization and habitat fragmentation on box turtle biology.  We have initiated a study to determine the effects of urbanization on home range size, activity patterns, habitat use, morphology, sex ratios, reproduction, and ages of box turtles from developed and undeveloped areas in the Davidson, NC area.  Vital characteristics of all turtles will be measured and we will use radiotelemetry to monitor the movement and activity of 12 turtles from developed and undeveloped areas.  Each turtle will be tracked every 48 h for approximately three months.  Location data will be analyzed using Global Information Systems (GIS) to determine the activity patterns, habitat use, and home range size.  Initial results show a greater number of female box turtles than male box turtles in developed and undeveloped areas.  Box turtles captured in developed areas have greater mass and have slightly longer length than turtles found in undeveloped areas.  More old turtles have been found in undeveloped areas than in developed areas. 

The Effects of Habitat Disturbance on Stream-Dwelling Salamander Populations in the Piedmont of North Carolina

J.D. Willson and Michael Dorcas

With human populations increasing worldwide, habitat destruction and degradation is one of the greatest threats facing wildlife. In forested areas, creeks and small streams are often the first habitats affected by human development and pollution.  Because they have porous skin and live in both aquatic and terrestrial environments, stream-dwelling salamanders are particularly vulnerable to anthropogenic disturbances, and thus provide a particularly good model for examining the health of small streams in the Piedmont of North Carolina.   These salamanders are the most common stream-dwelling amphibians in the Piedmont and can be easily captured thus allowing accurate population estimates.  We examined the effects of habitat disturbance on salamander populations in ten different streams that vary in the amount and type of disturbed habitat they drain.  Salamanders were captured using both funnel traps and by systematic dipnetting.  Salamander density was found to be inversely proportional to the percentage of disturbed habitat in the stream drainage with two-lined salamanders more vulnerable to disturbance than dusky salamanders.  In addition, we found substantial differences between trapping and dipnetting in the ratio salamander life stages captured. Our findings suggest that habitat disturbance can have detrimental effects on salamander populations.  Thus, conservation efforts aimed at preserving these ecosystems must protect the entire stream drainage rather than just preserving the stream itself.

The Effects of Food Type on Specific Dynamic Action in the Chocoan Horned Frog (Ceratophrys cranwelli)                                               

M. Jason Todd, Kristine L. Grayson, William A. Hopkins¹, Robert E. Gatten, Jr.², and Michael E. Dorcas.

After feeding, many animals exhibit a large increase in their metabolic rates. This effect, termed Specific Dynamic Action (SDA), reflects the energetic cost of processing nutrients. Most studies have shown SDA to be greater in animals that eat infrequently, such as large pythons.  This cost of food processing has important implications for the nutritional benefits received from the prey that sit-and-wait predators consume.  To better understand the effects of nutritional content on SDA in a sit-and-wait predator, we measured the SDA of horned frogs, Ceratophrys cranwelli, after eating 10% of their body mass in earthworms or 10% of the their body mass in mice.   We measured their oxygen consumption using a flow through respirometry system (Oxymax, Columbus Instruments).  Additionally, we measured the nutritional content of newborn mice and earthworms.  Earthworms contained substantially lower levels of lipids and calories than newborn mice and the energy required to digest the low-quality diet (earthworms) was similar to the energy required to digest the high-quality diet (mice).  Our results indicate that, because a large increase SDA after eating is similar regardless of prey type, prey with a high energetic content should be favored over those with lower energetic benefits.

¹Savannah River Ecology Lab, Aiken SC, 29802; ²Dept. of Biology, University of North Carolina, Greensboro, NC 27412

Effects of Food Type on Mass Conversion Efficiency and Growth Rate in Choacan Horned Frogs, Ceratophrys cranwelli

Leslie Cook, Dan Pierce, William Hopkins, Robert Gatten, Michael E. Dorcas

            Mass conversion efficiency is an organism’s ability to convert the mass of its prey into body mass. To optimize energy gained, a predator must minimize the calories expended to capture and handle the prey and maximize gross calories per prey.  Because they are ectotherms, amphibians, in general, have high conversion efficiencies, especially those that are ambush predators who expend little energy in capturing prey.  In this study, we examined the effects of prey type on the growth rates and mass conversion efficiencies in juvenile horned frogs, Ceratophrys cranwelli.  We chose C. cranwelli because they represent a classic ambush predator and have served previously as model organisms in digestive studies.  Our objective was to compare the growth rate and mass conversion efficiencies of juvenile C. cranwelli when fed a low energy diet (earthworms) versus a high-energy diet (newborn mice).  We fed 15 frogs either mice or worms for six weeks and weighed them weekly.  We also measured the nutritional content of the mice and worms.  Our results tended to show that mouse fed frogs gained more mass than worm fed frogs.  The average conversion rate of frogs fed mice was 83.82% ± 14.38% (SE) while the average for frogs fed worms was 38.22% ± 25.55%.  Due to the apparent increased nutritional value of the mice, mouse fed frogs gained more mass and had an exponential growth rate. 

Demography and habitat associations of pond dwelling turtles in the western piedmont of North Carolina

Shane D. Lindsay and Michael E. Dorcas

Few studies have addressed intraspecific variation in life-history characteristics among habitats of varying quality.  We used an extensive mark-recapture study to compare semi-aquatic turtle populations among twelve ponds with varying cattle impact in the vicinity of Davidson, NC.  We compared turtles at a community level while testing for differences in morphology and reproduction among the ponds.  We found considerable variation in species composition and relative abundances among the ponds.  We also found that Kinosternon subrubrum (eastern mud turtle) size and body condition is inversely correlated with concentrations of nitrite/nitrate and ammonia and that K. subrubrum egg size is inversely correlated with concentrations of nitrite/nitrate and overall cattle impact. Chrysemys picta (painted turtle) morphology and egg size was not correlated with measured characteristics of water quality or with cattle impact.  Other species captured in this study include Chelydra serpentina (snapping turtles), Trachemys scripta (sliders), and Sternotherus odoratus (musk turtles).  Populations of these turtles were too small to allow statistical comparison.  While farm ponds provide aquatic habitat that would not otherwise exist, K. subrubrum may be negatively affected by the impact of cattle on these ponds.

The Effects of Leg Banding on Attractiveness and Reproductive Success of Male Zebra Finches (Taeniopygia guttata)

Lucy E. Kuykendall and Leisa M. Rossello

Previous studies have indicated that the level of the attractiveness of male zebra finches (Taeniopygia guttata) may be influenced by the number and color of plastic leg bands, and that this attractiveness directly influences the number of fledglings produced by a given male, and therefore his reproductive success (Burley, 1986; Burley, 1982).  Eight male zebra finches were banded and observed for 80 hours over two semesters in the aviary of the Davidson College animal facilities.  Observations focused on female proximity, courtship and nesting behavior, and reproductive success (based on the number of fledglings).  Following a Pearson Correlation analysis, nesting behavior and female proximity were significantly related; however, it was concluded that neither banding nor female proximity had a significant effect on reproductive success, contrary to both previous results and our own expectations.  It is possible that further studies with a larger sample size, including more males at each level of attractiveness, may indicate that proximity, as well as other forms of male time investment, are significantly related to the number of fledglings produced by each male.

Burley, N. (1986). Influence of colour-banding on the conspecific preferences of zebra finches. Animal Behavior 30, 444-455.

Burley, N. (1982). Sexual selection for aesthetic traits in species with biparental care. American Naturalist, 127, 415-445.

Herpetofaunal Biodiversity of the Ramah Creek Conservation Easement
David A. Stroupe and Michael E. Dorcas

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 habitat’s 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.

Alterations in Target Levels of BDNF Impact Retinal Neuron Dendritic Arborization in Xenopus laevis Tadpoles

Adam French, Allan Leung, Susana Cohen-Cory, and Barbara Lom

Xenopus retinal ganglion cells (RGCs) express the neurotrophin brain-derived neurotrophic factor (BDNF) during dendritic arborization, as do the neurons that RGC axons innervate in the optic tectum. Thus, developing RGCs are simultaneously exposed to distinct sources of BDNF. We previously demonstrated that RGC axons and dendrites differentially respond to local alterations in BDNF. Tectal applications of exogenous BDNF rapidly enhanced RGC axon arbors, while retinal BDNF reduced dendritic arbors. To determine if BDNF signaling at the axon vs. dendritic terminal plays a role in the differential response of RGC axons and dendrites to BDNF, this study analyzed RGC arborization during alterations in tectal BDNF levels. Our results show that RGC dendrites extended significantly more branches within the retina when exogenous BDNF was applied to the tectum.  Correspondingly, neutralizing endogenous tectal BDNF with a function-blocking antibody significantly decreased RGC dendritic arbor complexity. Thus, retinal and tectal BDNF exert opposing influences on RGC dendritic arborization indicating that RGCs may differentially process signals from discrete BDNF sources to fine-tune dendritic morphology.

Use of Rapid, Chemiluminescent DNA Sequencing and Phenol-free RNA Isolation Protocols in the Undergraduate Curriculum

Christine Larned, David Wessner, Liz Nugent, Shannon Riedley, Karen Bernd, John McKillop.

The current emphasis on genomics, including the recently completed Human Genome Project and the whole genome sequencing of several microorganisms, illustrates how proficiency in DNA sequencing and gene expression studies are essential for continued study and research in biotechnology and medicine.  Unfortunately, most DNA sequencing protocols are expensive, time-consuming, and require either radioactive detection or an automated DNA sequencer.  Traditional RNA isolation techniques require the use of the toxic compound, phenol.  For these reasons, DNA sequencing and RNA isolation are usually precluded from undergraduate biology courses.  We recognized a need to develop DNA sequencing and RNA isolation protocols that can be incorporated into undergraduate course work.  We have developed a cost-effective, rapid, chemiluminescent DNA sequencing and detection protocol, in addition to a phenol-free RNA isolation protocol.  The DNA sequencing protocol uses a biotinylated primer.  The resulting fragments are separated on precast polyacrylamide gels using the NOVEX QuickPoint electrophoresis apparatus and then transferred to a nylon membrane. The DNA fragments then can be detected using streptavidin and alkaline phosphatase.  This entire protocol can be completed in two or three laboratory sessions.  Total RNA can be isolated from cells using the phenol-free Total RNA Safekit.  This protocol also can be completed within two laboratory sessions.  Using both of these protocols, students at Davidson College can investigate the sequence variation and expression of the isocitrate dehydrogenase gene (IDH) of E. coli, a unifying enzyme in our curriculum.  Using primers specific for the hypervariable 3’ end of the IDH gene, students can PCR amplify and sequence this segment of DNA from various isolates of E. coli.  The RNA isolation protocol allows students to investigate the expression of this gene.  These rapid DNA sequencing and RNA isolation protocols thus allow students in an undergraduate curriculum to develop a more complete picture of the molecular activity of a model gene.

Differing Herbicide Resistance Delimits Allelic Groups within the tip-1 Mutant Collection

Catherine M. Kizer and Dr. Karen Bernd, Davidson College Spring 2001

            Herbicides are important because they are used daily by many different consumers yet little is known about the specific mechanisms by which they work.  A group of Chlamydomonas strains have been identified containing two mutations; one that prevents proper translocation of cytochrome F into the thylakoid and a second mutation that suppresses the first. Identifying the number of different alleles represented in the tip1 collection is difficult to accomplish through genetic recombination so the number of alleles are being further characterized according to herbicide resistance. Certain strains in this collection have been found to have different resistances to the herbicide FPE. This study characterizes the strains according to their resistance to a second herbicide, Valor. A spectrophotometry based micro plate assay was used to determine the growth of each strain challenged with 0mM, 0.5 mM, or 1mM Valor.  Absorbance was measured at 750nm and data was collected twice a day for a minimum of one week. Based on resistance to Valor, at least 2 allelic groups are represented: one class has same resistance as wild type and the second class has increased resistance to Valor.  Comparison of this data with previous data of tip-1 mutant collection’s resistance to FPE, further subdivision of the classes was possible.  The two Valor-resistant strains, s21(+) and s120(+) form a subclass within those strains that also show increased resistance to FPE.  Thus the allelic groups represented is increased from at least 3 to at least 4.

Eastern Bluebirds as Environmental Indicators on North Carolina Golf Courses

David Lamar, Suzanne Moore, Meg Seifert, Mark Stanback, Ambrose Tuscano, Annie Welsh

Analysis of reproductive parameters of golf course nesting birds can provide valuable information on the biological effects of golfer and turf maintenance activities on course wildlife.  Because eastern bluebirds (Sialia sialis) nesting on fairways feed their young on insects collected primarily on managed turf, they may be vulnerable to the chemicals used there.  In 1999 and 2000, we monitored bluebird nests on golf courses and in control habitat for first egg date, clutch size, brood size, and nestling condition. Only for brood size did we detect significant effects of habitat type, with golf course broods being slightly smaller than non-golf broods.

Optimizing S. cerevisiae differential gene expression protocols for use in undergraduate laboratories.

J McKillop and K Bernd. Davidson College Davidson, NC

Understanding the transcription and expression of RNA is vital to understanding how cells function. Undergraduate laboratory courses usually avoid gene expression studies because RNA is unstable and its isolation and detection traditionally require the use of caustic and radioactive substances. We have optimized phenol-free RNA isolation, and non-radioactive Northern "dot blot" protocols for use in undergraduate laboratories. Recognizing the limitations of time, space, and experience that often confound lab exercises, these protocols allow the characterization of differential gene expression during the S. cerevisiae mating reaction. This work was funded by an Educational Enhancement grant through the North Carolina Biotechnology Center. 

Molecular Characterization of the Mouse Hepatitis Virus-A59 Receptor

Courtney S. Ewart and David R. Wessner

The cellular receptor is for mouse hepatitis virus A59 (MHV) is a murine biliary glycoprotein with two or four immunoglobulin-like extracytoplasmic domains.  MHV binds to the N-terminal domain (1) of this receptor between amino acids 34 and 52.  In the absence of domain 4 however, the virus no longer successfully infects cells.  An understanding of how other domains interact with the binding site on the receptor (MHVR) will add to current knowledge on virus-receptor interactions, and help in the quest to mimic viral infection pathways in order to develop powerful antiviral drugs.  Two chimeric constructs of MHVR, each containing the N-terminal domain and only one other domain, were used in this study.  One was a functioning receptor (MHVR 1,4) for MHV while the other was not (MHVR 1,2).  These MHVR constructs were spliced into a cloning vector.  Amino acid sequence analyses were made between MHVR (1,2) and (1,4).  Four point mutations were devised to turn 3 amino acids in domain 2 into amino acids from domain 4, in an attempt to make the non-functional receptor look more like the functional one.  Since domain 2 is slightly larger than domain 4, a deletion of 2 amino acids was also designed.  Once the mutations are completed and sequenced, the MHVR constructs will be cloned into mammalian vectors and expressed in a mammalian cell line.  These cells will then be infected with MHV and monitored for receptor activity through plaque assays.

Body Condition Within Eastern Bluebird Pairs: Mate Choice?

Ian Kaplan, Meg Seifert, Mark Stanback, Ambrose Tuscano, Catherine Walsh

If female birds prefer mates of the highest genetic quality, but are constrained in their choice of partner by the choices of higher quality females, one would expect to observe a positive correlation between male and female condition within pairs.  Alternatively, within-pair similarity could be due to the fact that paired birds live on the same territory and share parental duties.  To address this, we measured eastern bluebird (Sialia sialis) condition during the chick-rearing phase using indices of current vs. past condition.  Mass and hematocrit both reflect nutritional and physiological condition at the time of capture.  Size-specific mass and particularly bilateral asymmetry presumably reflect the condition of the bird during feather growth in the prior year.  Mass and hematocrit showed significant correlations between male and female social mates.  Feather-based indices showed no correlation.

Nest Site Fidelity in Eastern Bluebirds: Predator vs. Parasite Avoidance

David Lamar, Suzanne Moore, Meg Seifert, Mark Stanback, Ambrose Tuscano, Annie Welsh

By nesting in cavities low to the ground, secondary cavity nesters increase the likelihood of detection by mammalian and reptilian predators. By reusing soiled nests, such birds incur the costs of nest ectoparasites.  By experimentally varying these two factors, we tested the relative importance of each to nest site fidelity in Eastern Bluebirds (Sialia sialis).  Choice experiments demonstrated that bluebirds avoid reusing soiled boxes (if also given a clean box) but prefer to reuse successful nest boxes (if they are clean).  Bluebirds also showed a significant preference for high (1.75 m) vs. low (1.5 m) boxes for their first nests of the year, suggesting sensitivity to predation risk.  For second nests, we forced bluebirds to choose between their successful soiled box and the unused box from their first nesting attempt.  Bluebirds reused soiled high boxes at a significantly higher rate than they reused soiled low boxes, suggesting that bluebirds are willing to incur the costs of parasitism in order to lessen susceptibility to predators.

Molecular Cloning of the no mitochondrial derivative Gene, which Affects Mitochondrial Aggregation during Spermatogenesis in Drosophila melanogaster

Fitz Sturgill and Karen G. Hales

Mitochondrial morphogenesis is critical to spermatid development and function in Drosophila melonogaster.  During meiosis I and II, mitochondria become evenly distributed along the extranuclear component of the meiotic spindle where they are separated into each daughter spermatid.  In addition, mitochondria aggregate, fuse and elongate along the flagellar axoneme, presumably to permit efficient delivery of ATP.  The no mitochondrial derivative (nmd) mutation was generated by introduction of the P-element P{ry-11} and results in non-aggregation of mitochondria affecting both mitochondrial segregation and elongation.  In order to identify the responsible protein affecting aggregation, an inverse PCR-based approach has been utilized to obtain DNA which flanks P{ry-11}.  Disruption of an unidentified locus by ry-11 is thought to be responsible for the nmd phenotype.  Therefore, the sequence of this cloned DNA should permit identification of the responsible gene for sequence analysis and/ or manufacture of a recombinant protein.

Characterizing Mitochondrial Morphogenesis Mutants Affecting Spermatogenesis in Drosophila melanogaster

Shaheen M. Counts, Ridling Waller, and Karen G. Hales

Drosophila spermatogenesis requires the production and organization of mitochondrial derivatives to carry out the differentiation of primary spermatocytes into functionally normal spermatids. Several genes have been identified that are essential to this process including fuzzy onions (fzo) and no mitochondrial derivative (nmd).   We suspect that many genes responsible for this process have not yet been identified.  In an effort to uncover these genes, we have characterized several mutant fly lines with abnormal mitochondrial derivatives, each with a unique set of malformities that we presume represent the effects of a single mutated gene.

Ethanol Resistant Mutants of Reovirus are General Stability Mutants

Erin E. McKinley

Previously, a set of unique mutants of reovirus type 3 strain Dearing (T3D) that exhibit increased resistance to ethanol were isolated.  Genetic studies showed that the increased ethanol resistance phenotype resulted from single nucleotide changes in the M2 gene segment, which encodes the major outer capsid protein m1 (Wessner and Fields. J. Virol. 67:2442-2447. 1993).  Because this protein is in the outer capsid, we hypothesized that these viruses may be general stability mutants.  To test this hypothesis, we examined both the phenol resistance and heat resistance of these viruses.  When T3DEt^r and T3D wild-type virions were exposed to either 1% phenol for 15 minutes or  55°C for 30 minutes, mutant viruses exhibited less inactivation than wild-type virus. These results indicate that the reovirus mutants initially selected for increased ethanol resistance may be classified as general stability mutants.  It is interesting that these viruses, which contain mutations in the M2 gene, exhibit altered heat resistance because a previous study showed that reovirus strain differences in heat resistance were associated with the S4 gene (Drayna and Fields.  J. Virol. 63:161-170. 1982).  This finding, then, confirms previous work that describes an interaction between the two outer capsid proteins encoded by the M2 and S4 genes (m1 and s3, respectively).  We hypothesize that the mutations identified in M2 alter m1:s3 interactions resulting in a strengthened outer capsid which confers a general stability to these viruses.

Chemistry

Biocompatability Issues of Polymeric Intraocular Implants

Dax Allred

As the primary sensory input for humans, it is not surprising that chemists, biologists, and engineers alike have joined forces to develop several devices designed to improve and even restore peoples’ vision.  Diseases such as myopia and cataracts -- both associated with aging -- have become an increasing concern as the average life expectancy continues to rise.  Polymeric intraocular implants have been designed over the past five decades and are now used to replace several regions of the eye such as the lens, cornea, and the sclera.  Other ocular implants include drug delivery systems and even a light sensitive microchip that will someday replace detached retinas.  The majority of the intraocular implants are made of poly(methyl methacrylate) (PMMA) or 2-hydroxyethyl methacrylate (HEMA).  The surface properties of these implants can be altered to improve their biocompatibility and reduce postoperative recovery times.

The Incorporation of Anti-microbial and Anti-viral Properties into Medical Polymers

Natalie Clayton

            During the medical care process, it is essential that a sterile environment be maintained as completely as possible in order to ward off unwanted infections.  Part of a growing area to help maintain these conditions is the invention and production of products, used in the medical field, that help to deter infections by possessing anti-bacterial and anti-viral properties.  There are three main ways in which these properties are imparted: 1) by altering the surface properties of the polymer to prevent adherence of microbes, 2) incorporating antibiotic molecules into the polymeric structure, and 3) placing a polymeric, antibiotic coating on the device.  The first has found to be the least promising as it is impossible for "zero adherence" to be obtained.  Here, the state of the current technology is evaluated in reference to incorporating anti-microbial molecules into the polymeric structure and coating the devices with an anti-microbial, polymeric layer.  Some of the compounds used and discussed include, silver, copper, buckministerfullerene, quaternary ammonium salts, nonoxynol-9, and certain medicinal antibiotics.

Treating Post-surgical Osteomyelitis : Comparing Antibiotic Delivery via Biodegradable and non-Biodegradable Polymeric Bead Placement

Adam Michael French

Osteomyelitis is an infection that can arise after an invasive orthopedic procedure is performed.  Poly(methyl methacrylate) (PMMA) beads have traditionally been used for the delivery of antibiotics to the site of infection.  Unfortunately, PMMA beads necessitate an additional surgery for removal after the antibiotic is eluted, increasing the possibility for further infection.  Recent experimentation with sponge collagen has shown that this delivery vehicle effectively degrades, but does not deliver therapeutic levels of antibiotics for a long duration.  The goal of new delivery systems is to effectively deliver antibiotics to the site of infection and degrade after the antibiotic is eluted.  Biodegradable polylactide (PGA)--polyglycolide (PLA) copolymer can be tailored to control the rate of polymer degradation and antibiotic elution, thus allowing researchers greater flexibility in designing better bactericidal regimens.

Polymer Scaffolds in Tissue Engineering

Sarah M. Hooper

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.

Transdermal Nicotine Patches

Amanda Johnson

Some drugs such as nicotine are best delivered to the circulatory system transdermally or through the skin.  The desired drug can be incorporated into a polymeric matrix that is stuck directly onto the skin and worn as a patch.  One advantage of the patch is that it keeps a constant level of the drug in the body for an extended period of time.  Patches are also convenient and easy to use. The following information on nicotine patches will be presented:  brands that are available on the market, the companies that make them, the cost to the consumer, and the materials used.

Polymers used in Heart Valve Substitutes

John Sheffield Kenyon

         Disease affecting the mitral, aortic, or pulmonary valves of the heart is lethal.  Valve replacements include biological tissue implants or mechanical prostheses, of which focus will be solely on the mechanical.  Mechanical valves are made primarily of polytetraflouroethylene (Teflon®), polyethylene tetraphthalate (Dacron®), polyoxymethylene (Delrin®), polysiloxane (Silastic®), or polyurethanes.  A clinically acceptable mechanical heart valve substitute must be hemocompatible and durable.  Hemodynamically, a valve should allow for minimal stagnant flow areas as well as minimal peripheral flow while maximizing valve washing of the surface to prevent thrombus formation.  Structurally, the valve should be designed to distribute stress uniformly, and not concentrate it in an area, since this could cause fatigue leading to total device failure (Frazier, KadipaÏaoglu, Parmis, et al.).  However, all five polymers used in mechanical prosthetic heart valves available on the market today will cause thrombus formation and calcification, to varying degrees, if not properly treated with anti-thrombotic substances.  Furthermore, some of the earlier designs caused excessive hemolysis.  This project attempts to explore the polymers used for various mechanical valves, synthesis of these polymers, their histories and drawbacks, as well as their desirable properties and application as biomaterials.  Furthermore, the future of heart valve replacement will be briefly discussed with a novel approach of using polymeric scaffolding to induce growth of tissue engineered valves which can replace the diseased valve as a type of autograft and hence escape rejection by the host’s immune system.

Polymers used in Time-release Oral Drug Delivery:  A General Overview and a Detailed Examination of the Oral Delivery of Oxycodone

Jacob McClean

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.

Polymers Used in Anterior Cruciate Ligament (ACL) Prosthetic Grafts

Michael J. Osgood

            Damage, tearing, and rupture of the anterior cruciate ligament (ACL) is a frequent result of injury to the knee.  This ligament is crucial for stability and proper function of the leg.  There are a variety of approaches for replacing the damaged ligament.  The most common procedures utilize autogenous grafts taken from other structures in the patient’s knee, namely the patellar tendon.  However, there are significant drawbacks associated with this procedure, especially length of recovery and initial graft weakness.  There are two alternative sources for ACL grafts: cadaver allografts and synthetic grafts.  These options are attractive because they are much less invasive.  A variety of synthetic grafts have been employed in ACL reconstruction.  The most common are woven and braided fibers of poly(ethylene terephthalate), poly(propylene), ultra high molecular weight poly(ethylene), and poly(tetrafluoroethylene).  However, their use has declined in recent years due to graft failure resulting from lack of abrasion and fatigue resistance of the polymer fibers.  Still, synthetic grafts are an attractive option for ACL reconstruction, and there are a variety of promising new polymer-based grafts, including scaffolds that allow in-growth of tissue, stents that surround and protect autografts, and complete prostheses.

The Application of Polyimides in High Temperature Matrix Composites and their Performance Characterization in Aerospace Environments

Ragy Ragheb

            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.

             End-Stage Renal Disease and the Polymers Used in Hemodialysis Membranes

Lang Robertson

The chemical composition of blood must be carefully controlled to successfully bring nutrients and oxygen to the body’s cells and carry toxic waste materials like urea from those cells.  The largest responsibility for maintaining the blood’s chemistry falls to the kidneys, which remove harmful low molecular weight particles (up to 60,000 Da) from the blood and regulate the blood’s ionic concentration, while keeping the essential particles in the blood.  Even in severely damaged kidneys, as long as at least ten percent of their functional units are working, kidneys can still effectively maintain the body’s chemistry.  Damage to the kidneys from end-stage renal disease is so extreme that a kidney transplant is the preferable means of restoring kidney function.  In chronic renal failure or if there is no successful transplant option, an artificial membrane system, like peritoneal dialysis or hemodialysis, is employed to perform in lieu of the kidneys to extend the patient’s life.

            Peritoneal dialysis uses the natural peritoneal cavity of the patient as the semi-permeable membrane to transport wastes and ions across the membrane.  Hemodialysis uses both natural and synthetic polymers as the membrane to filter the blood, allowing the removal of waste particles without excess water loss.  Even though all synthetic membranes have a surface reaction with blood, the goal is to create blood compatibility to reduce platelet adhesion and coagulation for effective filtration.  With a successful polymeric membrane, hemodialysis can function as effectively as a patient’s natural kidneys to control the chemical composition of the patient’s blood.

The Enhanced Interfacial Biocompatibility Between Living Cells and PMMA Modified with Phosphorylcholine in Corneal Contact Lens Applications

Adam T. Soto

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.

The Use of Polydioxanone in Pediatric Surgical Applications

Ellen P. Stilz

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.

Shape-Memory Polymers:  Biomedical Applications

Fitz Sturgill

Shape-memory polymers (SMPs) are polymeric materials that can be deformed to assume a desired shape but return to their original forms upon temperature alteration.  Depending on the material, heating or cooling produces a change in the physical properties of the polymer as it passes a characteristic transition temperature.  Cross-linking or crystallinity is responsible for the shape-memory of the material.  Polymer hydrogels, urethane block copolymers and polynorbornene are three examples of SMPs that are being developed for use as medical devices. SMPs offer increased biocompatibility and versatility over shape-memory alloys as orthodontic devices, endovascular implants and many other potential applications.

Variations of the Piloty Pyrrole Synthesis

Ross M. Boyce with Dr. Erland Stevens

            One of the less explored reactions involving [3,3]-sigmatropic rearrangements is the Piloty pyrrole synthesis.  This synthesis involves the thermal rearrangement of ketazines with acid catalyst to produce pyrroles, following a pathway similar to that of the well-documented Fischer indole synthesis.  Pyrroles are very useful organic molecules and are found in a variety of conducting organic polymers, to include polypyrroles and porphyrins.  The Piloty synthesis is extremely limited in its scope, as there are few literature syntheses other than those utilizing the azine of cyclohexanone.  We proposed that the limiting step in this pathway was the poor equilibrium resulting in the bis-ene-hydrazine and consequent [3,3]-sigmatropic rearrangement to the respective pyrrole.  We thus attempted to use acylating agents, such as phthaloyl dichloride and acetic anhydride, to make the bis-ene-hydrazine more stable.  Our results indicated that we were able to stabilize this intermediate, but this did not result in an increased product yield.  We concluded that these pathways are severely limited at this time.  On a separate note, we were able to successfully synthesize unsymmetric azines in high yield, in an effort to couple novel ketones to cyclohexanone.  This synthesis appears to be the first of its kind.  When these unsymmetric azines underwent the Piloty synthesis, the pyrrole product of a symmetric azine was found.  This result indicates that the unsymmetric and symmetric azines are in equilibrium.  Thus, the synthesis of pyrroles from unsymmetric pyrroles does not seem possible at this time, given the reaction temperatures required for the Piloty.

Example Reaction Scheme:

Synthesis of Heteroaryl Boronic Esters for Use in Suzuki Cross-Coupling Reactions

Amelia Fuller

Suzuki chemistry, a useful methodology for synthesis of cross-coupled biaryl (Ar-Ar’) targets with biological and material significance, can be adapted to include boronic esters as starting materials in addition to the more commonly used boronic acids.  These boronic esters may allow for use of the Suzuki reaction with heteroaryl compounds whose boronic acids are unstable. Metallation chemistry can be used to synthesize analogs to target heteroaryl boronic esters by reaction of the heteroaryl lithium with alternate, non-borate electrophiles.  Such reactions demonstrate the efficacy of the metallation methodology for heteroaryl compounds, including pyridine and imidazole derivatives.  Similar reactions substituting borate electrophiles were unsuccessful, both in the pyridine and imidazole systems and in literature systems.  These failed reactions evidence the need for further investigation of this methodology. 

Generalized metallation reaction for aryl boronic ester synthesis Synthesis of Aryl Boronic Esters from Aryl Diazonium Ions

Becky Dobrin and Dr. Erland Stevens

The Suzuki cross-coupling reaction requires an aryl boron reagent that can be prepared from an aryl halide.  A recent publication has reported the substitution of an aryl halide with an aryl diazonium ion in the preparation of the aryl boron reagent.  Because the logical precursors of heteroaryl diazonium ions are readily available and inexpensive, the diazonium ions may be an attractive alternative to the corresponding halides.  This is especially true for heterocyclic systems that have been poorly studied in comparison to carbocycles.  Our work initially followed literature procedures to establish our ability to employ the published examples.  We then attempted to apply the methodology to heterocyclic examples with little success.  A survey of the literature revealed almost no examples of heterocyclic diazonium ions of the type that we were targeting.  Our results and reasoning for the instability of heterocyclic diazonium ions will be presented.

Synthesis of Peptide Modules and Tuning Ligands for Light Harvesting Arrays

Kurt Hirsekorn

Alternative energy sources have become an important issue in the chemical world in recent times.  Mimicking the natural processes of our world can offer clean and efficient energy alternatives.  This research serves to further the knowledge and synthetic tools necessary to create an efficient light-harvesting array that can mimic photosynthesis.  Two separate projects have been explored.

The first project involves the synthesis and photochemical study of ruthenium and rhenium based light-harvesting chromophores.  Absorbance, emission, lifetime, and electrochemical data were acquired. Various systems involving modified biypridine ligands were analyzed and it has been determined that a new ligand, 4,4’-bis(pyrrolidinocarbonyl)-2,2’-bipyridine, contains electrochemical properties sufficient to tune the array for desired efficiencies.  In summary, the first project has served to characterize the energetics of various ligand systems and provide us a new direction for light-harvesting designs.

 The second project involves incorporating new synthetic methods of building the oligoproline backbone of the array.  Current methods, solid phase peptide synthesis, have been time and yield limiting.  This research has used a DCC (1,3-dicyclohexylcarbodiimide) coupling reagent to synthesize various oligoprolines.  As of now, only the two-residue peptide has been completely isolated and crystallized.  However, we have determined that for a desired 26-residue peptide, using the Pro₂ precursor will cut solid phase synthesis time in half and raise yields by 24%.

Electrochemical Studies of Crown Ether-Modified Conducting Organic Polymers

Emily Clark and Dr. Susan Hendrickson

We investigated the response of crown ether-modified organic conducting polymers to potassium ions.  Dibenzo-18-crown-6 molecules were incorporated into poly(N-methylpyrrole) films by entrapment during the formation of the films.  We found the response of the modified films to potassium ions to be inconsistent between films.  Although there was always a shift in the oxidative peak potential of about 30-50 mV, it was not in the same direction for all films.  However, each individual polymer film showed a reproducible shift in oxidative peak potential in the presence of potassium.  This shift was selective to potassium ions and somewhat proportional to the concentration of the potassium ions.  In addition, we were able to remove the potassium ions from the films, returning the oxidative potentials to the values observed in the absence of potassium.  Thus, our results indicate that crown ether-modified conducting polymer films show potential for application as reusable, ion-selective sensors and that crown ether molecules do not need to be covalently or ionically bonded to the polymer films to achieve this response.

The Synthesis and Characterization of an Anionic Derivative of Dibenzo-18-crown-6 Ether

Ragy Ragheb

Several strategies for constructing ion-selective electrodes are based upon ion-selective polymer films.  One strategy for imparting metal ion selectivity to a polymer is to incorporate a crown ether into the polymer.  The selectivity of the crown ether is controlled both by the inner diameter of the crown ether ring and the diameter of the metal ion.  For polymers possessing cationic sites, a crown ether bearing an anionic pendant group may be incorporated into the polymer by ion exchange.  The anionic dibenzo-18-crown-6 ether derivative was synthesized from methyl 3,4-dihydroxybenzoate and o-bis(5-chloro-3-oxa-1-pentyloxy)benzene following an unpublished procedure by W.S. Bryant and H.W. Gibson at Virginia Polytechnic Institute and State University.  This synthetic approach was a multi-step process, and the yields for the individual steps were low.

Synthesis of Piperazine Derivatives of Dilazep, a Nucleoside Transport Inhibitor

Erin Bailey and Dr. Christian Grattan

The objective of this project was to synthesize two derivatives of dilazep, a nucleoside transport inhibitor (NTI).  Nucleoside transport inhibitors are the focus of a new area of gene therapy research that has sprung from the study of anti-folate drugs, a class of anti-cancer drugs. With the combined use of anti-folate drugs and NTI’s, nucleotide biosynthesis could, in theory, be brought to a standstill in cancer cells causing a swift death to the cells.  The NTI’s that are available now for use are not very effective in doing this job in the body because they are either rendered ineffective in some way or because they are too toxic to be used as a drug.  So, there is a need to synthesize new NTI’s in the hope that they will have the desired pharmacological effectiveness and also a good pharmacological profile. 

In this project, a piperazine ring replaces the central ring of dilazep.  The number and position of methoxy groups on the aromatic capping groups was varied.  The effects of their placement on their ability to inhibit nucleoside transport will be studied by Dr. H. Trent Spencer, Assistant Professor of Biological Sciences at the University of South Carolina.  The dilazep derivative with two 2,6-dimethoxybenxoate substituents was approximately 80%.  The yield of the dilazep derivative with two 3,4,5-trimethoxybenz-oate substituents is unknown at this time.  This high yield is promising in the area of NTI synthesis that is plagued by low yields and difficulty in synthesis.

Real Chemistry: Designing a Relevant Experiment for the High School Lab

Jessie Brown, Dr. Ruth Beeston and Mr. Andrew Coates

To many beginning students of chemistry, chemistry remains a constant intangible, consisting only of numbers and symbols that follow a complex system of rules that are difficult to comprehend and even more challenging to relate to.  The goal of this research was to bring chemistry to a tangible level that high school students could appreciate by designing an experiment linking a familiar, interesting topic to the existing chemistry curriculum.  To achieve this end, two mini-experiments focusing on the chemistry of dyes were designed and implemented in two honors chemistry classes at Mooresville High School.  In the first part, students synthesized indigo, the dye used in jeans; and then, in the second part, they utilized test fabric identification dyes to explore dyeing properties and identify an unknown fabric sample. This experiment incorporated a wide range of first-year topics, including stoichiometry, enthalpy observations, oxidation-reduction chemistry, and polarity.

Isolation and Purification of Cholesterol from Artificial Gallstones

Emily Clark and Dr. Felix Carroll

A classic experiment in introductory organic chemistry laboratories is the extraction of cholesterol from human gallstones.  However, due to the dangers of handling human specimens, the experiment no longer meets the safety requirements necessary to be performed in an introductory laboratory.  In this project, an introductory organic laboratory experiment was designed that carries out the extraction and purification of cholesterol from synthetic gallstones.  The “gallstones” were made from cholesterol, glue, and coloring agents.  A two-day experiment was developed that involves an ether extraction of the cholesterol from the gallstones on the first day and purification of the cholesterol (via the dibromide) on the second day.  The cholesterol is brominated using a solution of bromine in acetic acid, and the resulting dibromide is reduced using zinc dust.  The experiment can be performed on microscale quantities using the laboratory equipment available to introductory organic students.  This laboratory procedure avoids the biological hazards of using real gallstones and illustrates many of the basic techniques used in organic chemistry. 

Construction of a N₂ Laser

Drew J Crawford and Dr. Durwin Striplin

            The goal of this project was to construct a working N₂ laser for possible future use in photochemical experiments for the 361/362 lab course.  The nitrogen laser emits photons at 337.1 nm in pulses lasting from about 4 ns to about 7 ns and has an “auto off” mechanism caused by the strong absorbance of 337.1 nm photons by an intermediate energy state of nitrogen.  The short duration makes the nitrogen laser useful for experimentation requiring an exact amount of short duration electromagnetic radiation. 

            A laser is created when high-energy electrons pass through a low-pressure nitrogen atmosphere.  This phenomenon is created with a pair of flat parallel capacitors and a Blumlein switching technique at about 20,000 Volts.  Components include a copper clad epoxy-resin circuit board approximately 0.016 in (0.004 cm) thick for capacitors, quarter inch Plexiglas and silicone sealant to create a low pressure chamber, UV transparent lenses to allow the laser pulse to escape the Plexiglas chamber, and a low current 20 kV power supply.  While it is possible to build a power supply, it is beyond the scope of this project and a suitable power supply was borrowed from the Davidson Physics Department.

The Synthesis and Characterization of Dilazep, a Nucleoside Transport Inhibitor, and its 2,6-Dimethoxy Benzoyl Derivative.

James H. Daniel, Jr. and Dr. Christian Grattan

            Gene therapy as a method of cancer treatment is a growing field of research with extraordinary potential.  Recently, antifolate drugs have been used in order to slow cancer cell growth and replication.  These drugs accomplish this by inhibiting enzymes that are dependent on cell folate concentrations, a substance necessary for cell growth.  Many cancer cells, however, have developed resistance to these drugs.  The cells achieve this by transporting nucleosides from the extracellular medium to within the cell, thus accounting for the cell’s inability to synthesize the molecules themselves.  In theory, developing nucleoside transport inhibitors to eliminate this nucleoside flow could potentially halt cancer cell growth when used in conjunction with antifolate drugs.

            It is our goal to synthesize and characterize dilazep, a known nucleoside transport inhibitor, and its 2,6-dimethoxy benzoyl derivative.  Each synthesis was carried out in two steps.  The first step involved the formation of a benzoic acid chloropropyl ester, and the second step was synthesizing the final product.  All four compounds synthesized were analyzed by taking ¹H NMR spectra.  By comparing each molecule’s spectrum to the spectra of the reaction starting materials, it was found that all four compounds were synthesized successfully with minimal starting material remaining.  The nucleoside transport inhibitor potentials of dilazep and its 2,6-dimethoxy benzoyl derivative will be tested in vitro and eventually in vivo by Dr. H. Trent Spencer, Assistant Professor of Biology at the University of South Carolina, Columbia.  The results of these tests will influence future research involving the synthesis of additional dilazep derivatives.

Synthesis of Celebrex Analogs:  An Undergraduate Organic Experiment

Kim D'Ardenne and Dr. Erland Stevens

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.  The details of our work will be presented.

The Investigation of Functional Group Reactivity in Suzuki Coupling Reactions

Heidi R. Hester and Dr. David Brown

The Suzuki cross coupling reaction was discovered in 1971 and involves carbon-carbon bond formation between halogenated aromatic compounds and boron-containing compounds.  The investigation focused on compounds containing electron-donating groups (4-bromophenol, 4-bromoanisole, and 4-bromotoluene) because of the absence of this type of functional group in literature.  Boronic acid derivatives were used as the Suzuki coupling partner.  By thin layer chromatography (TLC), it was found that none of the reactions produced any evidence of product.  The results confirm the lack of reactivity of electron-donating groups in Suzuki reactions.  With plans to make a polymer from 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and 1,4-pheylenediboronic acid, a model study was designed using DDQ with p-tolylboronic acid.  However, it became apparent by TLC that redox chemistry was occurring between the DDQ and the ethanol before the coupling could take place.  Dimethoxyethane was used in place of ethanol and as a result, a white solid was isolated.  After analysis, the solid was identified and shown to be unreacted p-tolylboronic acid.  The results lead to questions concerning the strength of DDQ as an oxidant, and the nature of Suzuki coupling reactions where any type of electron-donating group is present in the starting materials.  DDQ appears not to be a suitable coupling partner for Suzuki coupling reactions.

Quantum Mechanical Calculations of Bipyridine Derivatives

Tony Marino and Dr. Durwin Striplin

          Rhenium-bipyridine complexes are chromophores with properties similar to that of ruthenium trisbipyridine.  The ruthenium complexes are currently being studied in light-harvesting peptide research, and various bipyridine derivatives are being tested.  The purpose of this study is to use computational chemistry to determine what ligands would be useful candidates for experimental study.  Since these ligands are often difficult to synthesize, their excitation energies and reduction potentials would be helpful for researchers to decide whether or not to try to build them.  The computations can take a significant amount of time, and they are never truly accurate, so the information gained from the computations may not be worth the effort required.  Computational chemistry was used to determine the excitation energies and reduction potentials of bipyridine and three of its derivatives, one of which has already been studied, another of which is in the

process of being characterized, and the last of which has yet to be synthesized.  The results are compared to the experimental data for the previously characterized ligands, and a methodology is proposed to streamline future computational study of bipyridine ligands.

Development of a Chemistry 121 Laboratory to Determine the Solubility Product Constant of Silver Chloride Using Ion Chromatography

Megan O'Neill and Dr. Susan Hendrickson

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 (K_sp) of silver chloride.  Extensions of this lab demonstrating the common ion effect and activities were also studied. 

Synthesis and Characterization of a Light Harvesting Peptide and Its Ability to Form a Self-Assembled Monolayer on Gold Surfaces

Steven Reece and Dr. Durwin Striplin

The synthesis and characterization of a light harvesting peptide are described, and its ability to self-assemble onto gold surfaces for use as an electron acceptor in a water-splitting energy source is explored.  The peptide is proline based with an N-terminal cysteine residue and has a derivative of ruthenium tris-bipyridine attached as a chromophore.  Solid phase peptide synthesis (SPPS) was continued from previous research to attach a cysteine residue to the end of a Pro₇-Ru-Pro₅ existing peptide.  The Pro₇-Ru-Pro₅-Cys product was purified using high performance liquid chromatography (HPLC) and characterized using a ninhydrin test, ¹H NMR, and circular dichroism (CD) spectroscopy.  Proline helices exist in two forms; a proline I helix (3.3 residues per turn) exists in organic solvents and proline II helices (3.0 residues per turn) exist in aqueous solvents.  The rate of conversion from the proline I helix to proline II and vice versa was determined using the CD data.  Freshly polished gold electrodes along with sputtered gold slides were used to study the ability of the thiol group on the N-terminal cysteine residue to bond to gold surfaces.  Emission spectroscopy of the chromophore was used to study the coverage of the gold surface.  Unfortunately, it was determined that either the conformation of the cysteine residue or the ionic interactions of the chromophores on different peptides prevent the molecule from assembling onto the gold surface.

Synthesis and Characterization of 5-Methyl-2,2’-Bipyridine, an Asymmetrical Derivative of 2,2’-Bipyridine

Eric Salo, Dr. Ruth Beeston, and Dr. Durwin Striplin

The primary objective of this research project was to synthesize and characterize an asymmetrical 2,2’-bipyridine (bpy) derivative, 5-methyl-2,2’-bipyridine (5-mebpy).  This compound will be useful as a precursor for several research projects within the department.  Asymmetrical derivatives of bpy continue to be difficult to synthesize and two previous attempts to synthesize 5-mebpy in this department have proved to be unsuccessful.  However, a recent paper indicated the success of synthesizing asymmetrical bpy derivatives (Savage, S.A.; Smith, A.P.; Fraser, C.L.  J. Org. Chem.  1998, 63, 10048 – 10051). 

Following the procedure of the 1998 article, the Negishi coupling strategy proved to be a successful and effective method.  The Negishi coupling strategy involves the coupling of an aryl zinc halide and aryl triflate or halide with a palladium catalyst.  To obtain 5-mebpy, a three-step synthesis was performed.  The first step synthesized 5-methyl-2-pyridone, followed by the synthesis of 5-methyl-2-pyridyl triflate.  In the last step, 2-pyridyl zinc chloride and 5-methyl-2-pyridyl triflate were coupled using a palladium catalyst.  A yield as high as 79% of 5-mebpy was obtained.  This product is currently being used in continuing work on the synthesis of 1,3,5-tris(2,2’-bipyridin-5-yl)ethyl)benzene and 2,2’-bipyridine-5-carboxylic acid.

Organic Residue Analysis of Bronze Age Pottery Sherds by Gas Chromatography-Mass Spectrometry (GC-MS)

Eric Knoche, MeeSun Sim, Emily Snyder, Brent Wilson, and Dr. Ruth Beeston

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

Physics

Orbit Stability in Various Solar Systems

Benjamin A Sargent

In the mid-nineteenth century, Daniel Kirkwood noticed that at certain distances from the sun asteroids did not occur.  After plotting the asteroids’ orbital radii versus the number of asteroids found at these radii, certain gaps (now named Kirkwood gaps) emerged, which could be explained by the presence of the planet Jupiter.  If asteroids orbit in these gaps, they would orbit in resonance with Jupiter; meaning, they would orbit a certain integer number of times around the sun in the same amount of time Jupiter would orbit [a lesser] integer number of times.  Each successive interaction with Jupiter would pull the planet further outward to a larger, possibly more stable orbit or even out of the solar system altogether.  This paper presents a computational study of the Kirkwood gaps for various two-planet solar systems.

A Comparison of Algorithms for Computing Fourier Series

Patten Priestley

The Fourier series was developed in the early 1800’s by Joseph Fourier to represent a periodic function as the sum of trigonometric terms.  This paper presents a study of the computational efficiency of  two algorithms for the calculation  of these terms.  The first computation uses direct integration by Fourier’s original method.  The second computation uses the modern Cooley-Tukey transformation known as the FFT.  The FFT is equivalent but faster.  In theory, this makes the FFT a better method but it has drawbacks that the original Fourier method does not have.

Hyperfine Atomic Structure in Rubidium 85 and 87

Laura M. Cupples

Atomic absorption and emission spectra are due to space quantization in the atom.  Discrete energy states are uniquely identified by sets of quantum numbers describing the wave function and angular momentum of the electrons.  Even further spectral line splitting occurs due to the interaction between the magnetic field induced by the electrons and the magnetic moment of the nucleus.  This spectral splitting is called hyperfine structure.    We examined the hyperfine structure of two Rubidium isotopes - Rb85 and Rb87 using a tunable diode laser.  The laser frequency was swept over the interval containing the spectral lines for the 5P1/2 to 5S1/2 transitions.  Due to various broadening effects, most notably Doppler broadening due to the motion of the Rb atoms, individual lines within these hyperfine peaks are washed out.  These lines can be resolved using a second saturating beam of the same frequency, traveling in the opposite direction from the original beam.  Using this technique, narrow spectral lines were observed and identified.  The intensity of these absorption and emission lines, along with the cross sectional area of the laser itself, can be used to determine the effective cross sectional area of the Rb atoms.  Changes in laser intensity due to absorption were measured at each of the four main hyperfine spectral peaks using a power meter, and the atomic cross section was calculated.

Quantum Transitions of Cesium and Rubidium via Non Linear Laser Spectroscopy

J. Meghan Carroll

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.

Radiative Recombination in Lattice-mismatched InGaAs/InAsP Heterostructures

Emmett Weindruch

Over the past fifty years, semiconductors have been at the forefront of almost every electronic revolution. Their use in diodes, transistors, computers, and lasers form the core of almost every modern technology. The usefulness of semiconductors, however, depends directly on how well we know their behavior. One of the most important properties of a semiconductor is the form of energy that is released when an electron relaxes from the semiconductor’s conduction band to its valence band. While the total amount of energy always remains the same, it can be released as either light or heat. This experiment studied the recombination processes of electrons in InGaAs/InAsP semiconductor heterostructures. These processes are critical factors in knowing the efficiency of many optical semiconductor devices. By exciting the heterostructure (which was cooled to 77 K) with a diode laser, we could measure the intensity of the luminescence emitted as a function of excitation power. These measurements allowed us to see the gradual transition between luminescent recombination and defect recombination, in which the semiconductor emits lower levels of light. We repeated this procedure for several different heterostructure samples, all with varying degrees of lattice-mismatch. This mismatch plays an important role in determining when defect recombination becomes the dominant type of relaxation in the sample. We present preliminary results on how the transition between defect-dominated and radiative recombination depends on lattice-mismatch.

Psychology

Self-Presentational Strategies in Job Interview Settings

Eric P. Arnold

Little, if any, current research addresses the topic of deception as a part of self-presentational strategies in job interview settings.  This study examined such behaviors by interviewing students at the University of Massachusetts for a job as a research assistant.  Participants were randomly placed into one of three categories and told the job they were applying for required someone friendly, competent, or someone that presented him/herself “well.”   Lies were then evaluated in terms of the type of lie told (exaggerations, subtle lies, and outright lies) and lie focus (self or other) based on methods established by Kashy and DePaulo (1996).   Thirty-seven of fifty-six applicants told at least one lie, the significant majority of which were subtle lies.  Dishonest statements from the participant also significantly focused on themselves.  Contrary to expectations, participants’ knowledge of the ideal applicant from a job description did not have an influence on the number or types of lies told.  These interviews were also evaluated by an independent group of students at Davidson College to see if the type of job each participant was applying for could be identified.  This portion of the experiment aimed to provide insight into whether the applicants’ knowledge of the job description would result in other behavioral changes and if these differences would be noticeable to independent observers.  Results showed that indeed there were no significant, noticeable changes in the applicants’ behavior regardless of the number of lies told during the interview.

The Effects of Local Nerve Growth Factor Synthesis on Septodentate Sprouting Following a Unilateral Entorhinal Cortex Lesion in Rats.

Jennifer L. Caldwell, Melanie Majure ’00, and Dr. Julio Ramirez (mentor)

Unilateral lesions of the entorhinal cortex (UECX), causing denervation of approximately 90% of synapses in the outer 2/3 of the molecular layer of the ipsilateral dentate gyrus (DG), induce rapid and significant reorganization of circuitry, or sprouting.  Nerve growth factor (NGF) is a specialized endogenous protein that enhances neurite outgrowth and cell survival in developing neurons of cholinergic neurons of the basal forebrain.  Exogenous NGF administration has been implicated in the regulation of septodentate sprouting.  Sprague-Dawley rats (n=11) were injected with 1) recombinant adeno-associated viral vector (rAAV) expressing NGF and green fluorescent protein (GFP), 2) rAAV expressing GFP, or 3) saline in the DG.  Fourteen days post-injection the animals received right UECX electrolytic lesions.  Four days post-lesion, the animals were sacrificed and hippocampal tissue was examined for GFP fluorescence and septodentate sprouting response.  Optical densitometric analyses revealed a two-fold increase in acetylcholinesterase (AChE)-positive fibers (a marker for cholinergic fibers) in the ipsilateral outer molecular layer of the dorsal DG in rats receiving the NGF expressing rAAV.  No significant increase was found in the ventral DG.  Thus, local NGF synthesis enhances the sprouting response of the septodentate pathway in the ipsilateral outer molecular layer of the DG following a rUECX.     

The Effects Of Low And Intermediate Efficacy Mu Opioids On Cocaine Enhanced Locomotion

Christopher Craig

Past research has shown that the effects of cocaine on locomotor activity are enhanced in rats that are pretreated with full opioid agonists (Cunningham et al 1997; Waddell and Holtzman, 1998), but attenuated in rats pretreated with opioid antagonists (Houdi et al, 1989). There have, however, been very few studies that have thoroughly investigated the interactions between cocaine and partial opioid agonists. Due to this lack of research it is unclear what role, if any, an opioid’s agonist/antagonist profile plays in these interactions. This study was designed in an attempt to close this gap by looking at partial opioid agonists in combination with cocaine – and examine the role of an opioid’s intrinsic efficacy in these interactions. Consistent with previous findings, the full agonist levorphanol dose-dependently enhanced the effects of cocaine, whereas naloxone dose-dependently attenuated the effects of cocaine (Andrews & Holtzman, 1987; Cunningham et al, 1997; Dettmar et al, 1978; Houdi et al, 1989). Novel findings showed that the partial opioid agonists buprenorphine, butorphanol, and nalbuphine all produced dose-dependent increases in the effects of cocaine, whereas nalorphine neither enhanced nor attenuated the locomotor effects of cocaine.  These findings suggest that an opioid’s ability to modulate the effects of cocaine is mediated, in part, by the opioid’s relative intrinsic efficacy at the mu receptor.

Ketamine And Flunitrazepam Interactions: The Effects Of Special K And Rohypnol On Motor Performance In Rats

Christopher Craig

Ketamine (Special K) and flunitrazepam (Rohypnol, Roofies) are popular recreational drugs that are commonly used at raves and in other club settings.  Both of these drugs have also been identified as agents that may be used in some types of sexual assaults (i.e., date-rape scenarios).  Because of their potential to be co-administered, it is becoming increasingly important to understand the interactions between these drugs under a variety of experimental conditions.  The purpose of this study was to examine the interactions between ketamine and flunitrazepam in an animal model of motor performance.  Ten male, Long-Evans rats were trained to run on a rotorod treadmill rotating at 16 rpm, and motor performance was measured as the latency for each rat to fall from the apparatus.  Following behavioral training, the effects of ketamine and flunitrazepam on motor performance were examined alone and in combination with one another.  When administered alone, each drug produced dose-dependent decreases in motor performance.  When ketamine and flunitrazepam were administered in combination with one another, the effects of the combination were much less than predicted, given the effects of each drug when administered alone.  These data suggest that ketamine and flunitrazepam have mutual antagonistic properties on motor activity.

Is the Word-Length Effect Due to Decay or Interference?

Kim Dobey, Dr. Kristi Multhaup, Jennifer L. Frymiare and Julia M. Philpott

Memory span tasks typically require participants to immediately recall a list of items in the order presented.  Participants typically recall more items from lists of short words (e.g., dog, sky) than from lists of long words (e.g., radio, gorilla).  This word-length effect (WLE) has long been attributed to a decay mechanism (e.g., Baddeley, 1990).  Recently Nairne, Neath, and Serra (1997) argued that proactive interference underlies the WLE rather than decay.  If Nairne et al. are correct, there should be no WLE in the first block of trials; the WLE should not increase over trials; and older adults should show a greater WLE than younger adults because they are more sensitive to interference.  Undergraduates and healthy older adults (n = 20/group) learned nonverbal filler tasks and were then presented with a series of word lists on a computer at a 1.5 s rate.  Immediately after a list was presented, participants recalled the words in the presentation order.  There were five blocks of four lists; blocks were separated by nonverbal filler tasks.  Young adults showed a WLE in block 1.  Older adults did not show a larger WLE, nor a larger WLE over across blocks than younger adults.  These data suggest that interference may not be the only mechanism that underlies the WLE.

Age-Related Differences to the Antinociceptive Effects of Kappa Opioids and an Examination of their Interactions with Spiradoline

Adam French

There is little research examining age-related differences to the antinociceptive effects of kappa opioids. The purpose of this investigation is to examine related differences in sensitivity to the antinociceptive effects of three high efficacy kappa opioids (U50,488, U69,593, and spiradoline) and two opioids possessing low efficacy at the kappa receptor (nalbuphine and butorphanol) in young (3 months) and aged rats (21 months). U50,488, U69,593, butorphanol, and nalbuphine were also combined with spiradoline to examine their agonist/antagonist properties at the kappa receptor. Antinociception was assessed in a warm-water tail-withdrawal procedure, in which tail-withdrawal latencies were measured at 50^o (low stimulus intensity) and 55^o (high stimulus intensity) C water. Aged rats were more sensitive to the antinociceptive effects of all five drugs at both nociceptive stimulus intensities. In drug combination tests, U50,488 and U69,593 increased the effects of spiradoline, shifting its curve upward and to the left. When combined with spiradoline, nalbuphine and butorphanol acted as agonists under some conditions, while acting as  antagonists under other conditions. These results show a robust and consistent trend with aged rats being more sensitive than young rats to the antinociceptive effects of kappa opioids. 

The Effects of AIT-082 on Behavioral Recovery and Septodentate Sprouting After Bilateral Entorhinal Cortex Lesions

J. Taylor Herbert

Alzheimer’s disease is marked by a progressive decline in memory functioning and bilateral degeneration of the entorhinal cortex, among other areas.  Rats with entorhinal lesions exhibit behavioral deficits in Y-maze learned alternation tasks that test the types of memory lost in Alzheimer’s disease patients.  The entorhinal cortex projects to the hippocampus, and after entorhinal lesions in rats, several projections from other brain areas reorganize and reinnervate the hippocampus.  Furthermore, after unilateral entorhinal lesions, sprouting from the contralateral entorhinal cortex seems to mediate behavioral recovery.  After bilateral entorhinal lesions, the septodentate pathway from the medial septum also sprouts to the hippocampus, although this pathway may or may not be necessary for behavioral recovery after bilateral lesions.  AIT-082 is a drug that mimics the effects of several naturally occurring molecules in the brain that promote neuron survival and recovery after injury, and it improves behavioral performance in mice with age-related deficits.  The current study tests whether AIT-082 can enhance sprouting from the septodentate pathway and/or improve behavioral recovery on Y-maze tasks in rats after bilateral entorhinal cortex lesions.  The results of this study do not indicate that AIT-082 significantly enhances septodentate sprouting or behavioral recovery in rats with bilateral entorhinal cortex lesions.  Nevertheless, AIT-082 may have other effects that slow down the neural degeneration and loss of memory seen in Alzheimer’s disease.  Future research should focus on AIT-082’s neuroprotective properties and model in which entorhinal cortex degeneration is not complete. 

The Effects of Dimenhydrinate on Mood and Cognitive Performance

Jacob McClean

Diminehydrinate, the active ingredient in Dramamine, is a first generation anti-histamine used for its antiemetic and antivertigo properties. This study examined how dimenhydrinate affects mood and cognition in healthy volunteers.  Eleven Davidson College students enrolled in the Behavioral Pharmacology course volunteered to participate in the study. All participants were randomly assigned under double blind conditions in a within-subject design to receive 50 mg dimenhydrinate and placebo on two separate occasions.  Dimenhydrinate’s effects on mood were tested via a mood questionnaire in which the participants were asked to respond to questions regarding their current mood state on a 7 point Likert scale.  Cognitive performance was evaluated using the Digit Symbol Substitution Test (DSST) and a free recall test.  A repeated-measures ANOVA revealed a significant drug x time increase in drowsiness but there were no other main effects for any other mood or cognitive measure.  Thus, dimenhydrinate had a sedative effect, but did not impair cognitive performance at the dose administered.

Female Body Size as a Function of Race on Television Sitcoms

Laura K. McDonnell

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.

The Prevalence of Social Anxiety Disorder in a Nicotine-Dependent Population

E. Kiernan McGorty

The present study assessed the prevalence of social anxiety disorder (SAD) and its effect on smoking behaviors in nicotine-dependent smokers enrolled in a cessation clinic.  Forty-two participants completed the Social Phobia Scale, Social Interaction Anxiety Scale, and a smoking and quitting history questionnaire.  A significantly greater prevalence of SAD was found among nicotine-dependent smokers (39%) as compared to the general population.  The SAD group smoked more cigarettes per day over their smoking career and during their heaviest smoking period and scored higher on the Zung Self-Rating Depression Scale and State-Trait Anxiety Inventory than the nonSAD group.  The two groups did not differ in their cessation success at 30, 90, 180, and 365 days.  Because of the high prevalence of SAD among nicotine-dependent smokers and some evidence that their smoking behaviors are more dangerous, doctors should be conscious of the possible presence of SAD in their smoking patients.

The Effects of AIT-082 on Behavioral Recovery in Unilateral Entorhinal Cortex Lesion Induced Memory Loss in Rats: An Alzheimer’s Disease Model

Aaron J. Patton

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 Delay Intervals and Personality on Time-based and Event-based Prospective Memory

Kerry Sugrue

Prospective memory involves our ability to remember to do things in the future.  Einstein and McDaniel (1990) proposed a distinction between two types of prospective memory tasks—event based tasks, which require one to do something after some sort of external event or cue arrives (e.g., remembering to give a message to a friend upon seeing him); and time-based tasks, which require one to do something after a certain passage of time (e.g., remembering to take a medication in 4 hours).  The effects of delay intervals (the time between intention formation and intention performance) and a personality variable of action control orientation (Kuhl, 1990) on time-based and event-based prospective memory was investigated.  Thirty-eight undergraduates (25 female) were assigned to a time- or event-based condition; all participants experienced both short (3 min) and long (12 min) delay intervals.  Participants were asked to press a touchpad while watching movies after a passage of time (time-based) or whenever a particular scene occurred (event-based).  Prospective memory performance was significantly better for event-based than time-based tasks.  Time-based performance was significantly more accurate with 3 min than 12 min intervals; event-based performance showed the same trend, although the data did not reach significance.  There was no significant relationship between action control orientation and prospective memory performance.

Does Studying to Music Improve Performance on Reading Comprehension for Certain Personalities?

Ida Wainschel

The purpose of this experiment was to examine the effects of classical music on reading comprehension test performance for introverted and extraverted personality styles.  Participants were 37 psychology students at Davidson College who received course credit or favorable acknowledgement from their professor for their participation.  The experiment was conducted under four conditions (studying to music or in silence; and testing to music or in silence), designed to simulate a typical study-test pattern, an evening study phase followed 12 hr later by a testing phase.  The original hypotheses were that test performance and studying would be directly influenced by a context-dependency effect (where the two matching conditions would facilitate performance and the two mismatched conditions would not), and that personality style (introvert-extravert) and music would interact on performance.  These hypotheses were not confirmed.  However, there was evidence that familiarity with the background music significantly predicts performance, and evidence that listening to fast-tempo (about 100 bpm) background music indirectly improves performance by increasing reading speed in study conditions.

The Effects of Exercise, Intrinsic Efficacy, and Nociceptive Intensity on Opioid Antinociception in a Rodent Tail Withdrawal Assay

David L. Yancey

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.

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