Biology Honors Papers

The Role of CXCL7 in the CXCR2 Angiogenesis Cascade

George David — Fri, 18 May 2012 09:42:52 PDT

Habitat Use and Specialization of Foraging Bats in New Jersey

Erica Fischer — Fri, 18 May 2012 09:42:51 PDT

Transcriptional Regulation of Notch target E(spl)mγ by Tramtrack69 and Putzig in Drosophila melanogaster

Emily Hunter — Fri, 18 May 2012 09:42:50 PDT

Effects of a NITREX Permeable Reactive Barrier on Groundwater Chemistry, Primary Production, and Benthic Infaunal Abundance

Kenly Hiller — Tue, 31 May 2011 11:56:07 PDT

Quantitative assessment of Atlantic bluefin tuna depth patterns in the Gulf of Maine, 2008-2009

Thomas Howd — Tue, 31 May 2011 11:56:05 PDT

Reasoning about communication by rhesus macaques (Macaca mulatta)

Christopher Krupenye — Tue, 31 May 2011 11:56:04 PDT

A Method to Quantify Muscle Atrophy in a Rodent Model of Facial Nerve Injury

Julie Weinberg — Tue, 31 May 2011 11:56:02 PDT

Mechanism of cold acclimation in the salt marsh amphipod Orchestia grillus

Nicholas Woolf — Tue, 31 May 2011 11:56:00 PDT

Natural Ice-Nucleating Bacteria Increase the Freezing Tolerance of the Intertidal Bivalve Geukensia demissa

Alexander M. McCorkle — Sat, 16 May 2009 08:07:40 PDT

Instead of avoiding freezing, freeze tolerant invertebrates actively initiate controlled ice nucleation at relatively high sub-zero temperatures in extracellular compartments. Most produce proteinaceous ice-nucleators in their hemolymph, however the intertidal bivalve mollusc Geukensia demissa lacks this ability. Instead it utilizes at least one strain of ice-nucleation active (INA) bacteria, Pseudomonas fulva, present in seawater, to induce crystallization in the pallial fluid that fills its mantle cavity. In this study, two additional INA bacteria strains were isolated from the palial fluid of Geukensia demissa: Psychrobacter sp. and Shewanella sp. The ice-nucleation activity of both strains was characterized and Psychrobacter was found to consistently induce nucleation at temperatures 1-3°C higher than Shewanella. Based on 16S rRNA sequencing, neither of these bacteria have yet been identified. The effects of Psychrobacter on the freeze tolerance of summer-acclimatized Geukensia were assessed and compared to the freeze tolerance of winter-acclimatized specimens. This assessment was accomplished through whole-organism death experiments involving 12-hour periods of exposure to sub-zero temperatures and cell viability tests using a LIVE/DEAD sperm viability kit (Molecular Probes, Inc, Eugene, OR). Adding INA bacteria to summer-acclimatized Geukensia reduced their LT50 from -12.5°C to -15.0°C. The LT50 of winter-acclimatized specimens was determined to be -16.5°C. This result may be explained by the presence of cryoprotectants and multiple strains of bacteria in the winter-acclimatized specimens. Gill cell viability tests resulted in an average of 12% greater damage in summer-acclimatized Geukensia without added bacteria at -13.5°C, but no significant differences at -10°C and -15°C. This study is, to our knowledge, the first time that a bacterium has been shown to increase the survival of a freeze tolerant animal.

Regulation of E(spl) Gene Expression During Development

Morgan L. Maeder — Fri, 11 Aug 2006 11:45:43 PDT

The Notch pathway, a crucial developmental signaling system, acts to direct the fates of individual cells in many organisms and has also been implicated in a wide range of human diseases. Notch signaling plays a vital role in cell fate decisions in almost every tissue type ranging from the skin to the nervous and vascular systems. Aberrant Notch signaling has been implicated as a cause of many diseases, including a variety of cancers. Activation of the Notch receptor releases a Notch intracellular domain into the nucleus, where it binds with a transcription factor, Suppressor of Hairless (Su(H))to create an active complex which upregulates expression of target genes. In Drosophila the primary targets of Notch activation are the Enhancer of Split [E(spl)] genes. The E(spl) genes encode a family of basic-helix-loop-helix (bHLH) transcription factors, which exhibit overlapping functions throughout developmental stages. In order to determine the mechanisms through which E(spl) gene expression is controlled, I used three approaches to study E(spl) regulation. First, Bioinformatics analysis of the upstream regulatory regions of the E(spl) genes reveals binding sites for transcription factors that may act to regulate E(spl) gene expression. Evolutionary conservation of sites in the regulatory region lends support to their importance in the regulation of gene expression. Second, Real Time PCR quantification of the expression of three E(spl) genes at different stages of Drosophila metamorphosis suggest roles for some of these genes. Third, a reporter vector with the upstream region of one of the E(spl) genes cloned upstream of the firefly luciferase gene was constructed and used in Drosophila tissue culture experiments to further analyze the regulation of gene expression. Results from these three approaches will help to better understand the process of gene regulation and to characterize the mechanisms involved in controlling gene expression. Specific understanding of Notch target genes will elucidate how the Notch pathway functions in both normal and disease cells.

Analysis of the Upstream Regulatory Region of the Enhancer of Split m7 gene in Drosophila

Bryanne E. Robson — Tue, 08 Aug 2006 07:51:38 PDT

The Notch pathway is one of the vital signaling pathways used during Drosophila development. Present in many organisms and extensively studied in D. melanogaster, this pathway serves to transduce signals between neighboring developing cells and inhibits neuronal differentiation by lateral inhibition. The primary targets of Notch are the Enhancer of split (E(spl)) genes. Although the upstream regulatory regions of the E(spl) genes contain biding sites for Suppressor of Hairless, Proneural, and E(spl) proteins, their expression patterns are not identical. There is a hidden complexity in the regulatory regions of these genes that may help explain the conservation of the overall organization of the E(spl) complex between different species of Drosophila. We are interested in determining what is responsible for this variation in expression, and have investigated these genes using different approaches. First, using the upstream regulatory sequence of D. melanogaster and D. pseudoobscura as reference sequences, we compared the upstream regions of the E(spl) m7 gene to D. simulans, D. sechellia, D. yakuba, D. erecta, D. ananassae, D. persimilis, D. grimshawi, D. virilis, and D. mojavensis using BLAT (Kent 2002) and EvoPrinter (Odenwald et al. 2005) applications. Second, we isolated and sequenced part of the regulatory region of D. pseudoobscura m7 to confirm previous published results and gain more insight on the functionality of the region. The differences and similarities in upstream sequences of the E(spl) genes are being used as a tool to help further determine if functions of these genes are conserved. This approach will give insight into which regulatory sites are essential to proper Drosophila development after millions of years of species divergence.