The need for effective treatment of traumatic bone defects has increased in both military and domestic settings. A possible solution has been to utilize nanofibers as a scaffold for the purpose of facilitating regeneration of bone. This study seeks to develop a designer nanofiber-based bone repair device that is capable of delivering drugs while facilitating regeneration of the bone. Towards this goal, we evaluated a panel of nanofiber compositions consisting of poly(lactic-co-glycolic acid)(PLGA), hydroxyapatite (HA), collagen and antibiotics for in vitro cytotoxicity, cellular proliferation, migration and osteoblast differentiation. All assays were carried out using the human embryonic palatal mesenchyme (HEPM) stemcell line under conditions of glucocorticoid differentiation. Cell viability was measured as a function of metabolic ATP production. Confocal and light microscopy was used to evaluate cellular adherence and migration on nanofiber matrices. Finally, as a positive indicator of osteoblast differentiation, osteocalcin (OCN) gene expression was evaluated via RT-PCR. All nanofiber compositions tested support active proliferation. Cell viability, reported as a percent of the non-nanofiber control, ranged from 36-89%. With the exception of nanofibers containing the antibiotic tobramycin, relative proliferation levels were similar among all nanofibers, indicating that differences in chemical additions to the PGLA nanofibers were not likely to be the sole reason for the reduced proliferation of cells on nanofibers. Confocal microscopy revealed migration of adherent cells throughout the nanofiber matrix and these cells were positive for osteoblast differentiation. Future directions include a pilot study for nanofiber safety and efficacy in a rabbit model for bone repair.
Biological and Environmental Sciences, University of Tennessee at Chattanooga, Chattanooga, TN.
Integrating Chemotaxis and Thermotaxis in Caenorhabditis elegans
In wild-type Caenorhabditis elegans an attraction has been shown toward the thermal temperature that the worms were cultivated, as well as a wide variety of chemical attractants including almond extract. By presenting the worms with two simultaneous stimulants, chemical and thermal, which are detected by separate neurons, the synapses and pathways that the worms use to make a choice regarding a stimulus can be examined. We have found that the worms are strongly attracted crylophilically to their cultivation temperature, if it can be found on the plate, and are otherwise strongly attracted to the chemical attractant (almond extract). Interestingly, the worms were unable to move both thermophilically (up the temperature gradient) and toward the almond extract (chemical attractant used). This is interesting because it points to the importance of the AWC neuron and also the ability of one sensation to override the other.
156 • Cristina M. Caldwell1, Michele Elmore2, Julie Ballenger3, Kevin S. Burgess3
Examining the Genetic Structure in a Hybrid Zone of Rare Georgia Pitcher Plants (Sarracenia Spp.)
Hybridization has been shown to have negative impacts on rare plant populations. Specifically, asymmetrical introgression can lead to the loss of rare parental taxa via genetic assimilation into the genomes of more abundant congeners. Less is known, however, about the occurrence of introgression between parental taxa that do not differ in abundance. Pitcher plants belonging to the genus Sarracenia are insectivorous plants endemic to North America. Eight of the nine species within the genus are concentrated in the southeastern United States, where they are threatened primarily by habitat degradation. Here, we investigate the potential occurrence of introgressive hybridization in sympatric populations of Sarracenia rubra (sweet pitcher plant) and Sarracenia psittacina (parrot pitcher plant), two species that are listed as threatened within the state of Georgia. Currently we are using DNA barcode markers to confirm the genetic identity of parental taxa as well as determine the parentage of putative hybrids. Furthermore, microsatellite analyses will be used to establish hybrid indices that will provide novel insight into the process of introgressive hybridization occurring between these two rare species.
1 Environmental Science Program, Columbus State University; 2 The Nature Conservancy, Fort Benning Field Office; 3 Dept of Biology, Columbus State University
157 • Matthew A. Heard, Robert Grammer
Innate Versus Learned Response to Bacillus thuringiensis and Isoamyl Alcohol as Modeled by Olfactory Chemotaxis Response in Caenorhabditis elegans
Caenorhabditis elegans has been shown to exhibit innate positive chemotactic responses to chemicals as well as bacterial attractants. C. elegans can be classically conditioned with the coupling of starvation in the presence of the odorant and known attractant isoamyl alcohol. The nematode learns to associate the isoamyl alcohol with starvation and deviates away from the chemical. C. elegans normally shows an innate, positive response to Bacillus thuringiensis. Through this method, the strength of innate and learned responses can be compared. In the presence of isoamyl alcohol and Bacillus thuringiensis, a positive or negative response to the mixture on the plate will reveal which stimulus induces a stronger chemotactic response. It was hypothesized that the nematodes will show a higher response to the isoamyl alcohol because it will have just been conditioned to show a negative response to one of the attractants.
