Berook Alemayehu Forestville, MD University of Maryland, Baltimore County Sophomore Computer Engineering Faculty Advisor: Radu Sion, Assistant Professor Department of Computer Science
xKey: Identification Software Using Keystroke Dynamics Berook Alemayehu(1), Radu Sion(2) This paper deals with the application of keystroke dynamics to identify specific users of a computer. Biometrics is now the most popular method of user identification since it uses information about a person that cannot be stolen or copied. Using keystroke dynamics provides the protection that many biometrics offer while being relatively inexpensive compared to other methods of identification. The applications of keystroke dynamics we used were inter-key times (the time it took to type between keys) to identify a specific user. Here we show that our implementation and development of identification software that uses keystroke dynamics proves to be a very powerful biometric tool. (1)Department of Computer Science and Electrical Engineering, University of Maryland, Baltimore county, 1000 Hilltop Circle, Baltimore, MD 21250 (2)Department of Computer Science, Stony Brook University, Stony Brook, NY 11794-4400
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	Mozella Bell Campti, LA Southern University at Shreveport Junior Biology Faculty Advisor: Howard Crawford, Assistant Professor Department of Pharmacological Sciences
The role of PDX-1 in the regulation of MMP-7 gene expression in pancreatic cancer Mozella Bell(1), Howard Crawford(2) Pancreatic ductal adenocarinoma (PDAC) is an aggressive and devastating disease. It is characterized by invasiveness, rapid progression and profound resistance to treatment, resulting in a median survival of 6 months. PDX-1, a transcription factor, is essential to the early development of the pancreas. In an adult the PDX-1 gene is turned off stopping further formation of the pancreas. However, PDX-1 expression is reinitiated in PDAC cells. MMP-7, a protease, is not expressed in normal pancreatic cells, but is expressed in PDAC cells. Because both MMP-7 and PDX-1 are expressed in PDAC, we set out to test the hypothesis that PDX-1 positively regulates MMP-7 expression by activating the MMP-7 promoter. Our results show that PDX-1 does indeed increase MMP-7 promoter activity by approximately 12 fold. (1)Department of Biology, Southern University at Shreveport, 3050 Martin Luther King Drive, Shreveport, LA 71107 (2)Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651
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	Luis Cocka Silver Spring, MD University of Maryland,Baltimore County Sophomore Biochemistry Faculty Advisor: Gloria Viboud, Research Assistant Professor Department of Molecular Genetics and Microbiology
Analyzing pH6 Antigen-Mediated Adhesion in a Plasmid-Cured inv-Strain of Yersinia pseudotuberculosis Luis Cocka(1) , Kizzmekia Corbett(2), James Bliska(3), and Gloria Viboud(3) Yersinia pseudotuberculosis is an enteropahogenic bacterium that utilizes a type III secretion system to inhibit immune responses when sufficient adhesion to the host cell occurs. The pH6 antigen induces adhesion in Yersinia pseudotuberculosis at low pH and 37°C. The entire psa operon (psaEFABC) is necessary to produce a fully functional protein that shows considerable expression. Other transcriptional promoters have been found to produce pH6 antigen expression in the absence of psaEF. Primary Yersinia pseudotuberculosis adhesins, YadA and invasin, bind to the ß1-integrin receptor on the host cell triggering certain signaling responses. However, the pH6 antigen alone cannot induce integrin-mediated signaling because it does not have direct interaction with the ß1-integrin receptor. In this work we transformed a Yersinia strain (YP202) lacking its virulence plasmid (pYV-) and invasin (inv-) with two plasmids that encoded for the pH6 antigen. Two plasmids were used; pAY50 encodes for the entire psa operon and pAY66, which has a lacP promoter driving the expression of psaABC. YP202 and its derivatives expressing the pH6 antigen were grown under six different conditions to analyze expression, adhesion, and internalization. The expression of the pH6 antigen was detected by Western Blotting. The pH6 antigen showed more expression under optimal conditions, pH6 and 37°C. An uptake assay conducted on the Yersinia under the six conditions showed very good adhesion for the strains at pH6 and the pAY66 strain. Limited to no internalization was also observed. With the expression of the antigen and low percentage of internalization a premature conclusion can be stated that integrin mediated signaling is not apparent in a Yersinia strain pYV- and lacking invasin. (1)Department of Chemistry and Biochemistry, University of Maryland, Baltimore Country, 1000 Hilltop Circle, Baltimore, MD 21250 (2)Department of Biological Sciences, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (3)Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222
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	Kizzmekia Corbett Hillsborough, NC University of Maryland, Baltimore County Sophomore Biology Faculty Advisor: Gloria Viboud, Research Assistant Professor Department of Molecular Genetics and Microbiology
Creation of a YadA mutant to study type III secretion signaling in Yersinia pseudotuberculosis Kizzmekia Corbett(1), Luis Cocka(2), James Bliska(3), and Gloria Viboud(3) Yersinia pseudotuberculosis is gram-negative bacteria that cause gastroenteritis and lymphadenitis in humans. Yersinia pseudotuberculosis uses a type III secretion system (TTSS) to deliver effector proteins into host cells. When the bacteria bind to the host cell, the TTSS becomes activated and counteracts the host cell´s innate immune responses. The two main bacterial pathogens that mediate adhesion are invasin and yadA. YadA/invasinmediated adhesion engages ß1-integrin pathways that lead to Rho GTPase activation. A component of the TTSS´s translocation machinery, YopB, has been found to cause IL-8 production and pore formation. In wildtype Yersinia, this signaling is counteracted by the effector proteins that inhibit the host cell´s proinflammatory responses: YopE, YopH, and YopJ. Because YopE inhibits Rho GTPase activation in wild-type Yersinia, it is thought that YopB can also mediate the activation of Rho GTPases. To further understand the mechanisms by which YopB mediates pore formation and IL-8 production, we introduced a frame-shift mutation in the yadA gene into a Yersinia pseudotuberculosis strain that had mutations in YopE, YopH, YopJ, and invasin. The yadAfs mutation was mobilized to Yersinia using a suicide plasmid containing the sacB gene. The new strain, YP50, was obtained by selecting in sucrose plates. Because TTSS activation requires sufficient adhesion, a plasmid coding for another adhesin, pH 6 antigen, was inserted into YP50. The resulting strains, YP50/pAY50 and YP50/pAY66, showed good adhesive properties in HeLa cells. Upon testing for IL-8 production and pore formation, this strain will allow for the comprehensive study of whether the ß1-intergrin adhesion, mediated by YadA and invasin, is needed for YopB´s signaling to occur. (1)Department of Biological Sciences, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (2)Department of Chemistry and Biochemistry, University of Maryland, Baltimore Country, 1000 Hilltop Circle, Baltimore, MD 21250 (3)Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222
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	Ashley Dapremont New Orleans, LA Howard University Senior Psychology Faculty Advisor: Patricia Whitaker, Professor Department of Psychology
Mapping Socially Rewarding Circuitry in Autistic Brains Ashley Dapremont(1), Patricia M. Whitaker(2) Autism is a neurodevelopmental disorder related to dysfunction of the serotonergic system which causes a disruption of normal social and cognitive functioning. Serotonin coordinates the activities in the paraventricular nucleus of the hypothalamus (PVN) and the central nucleus of the amygdala (CN). Lack of serotonin in autistic children disrupt this entire interaction and prevent positive feelings about social interaction. It is predicted that the circuitry for socially rewarding behavior stems from serotonin cells which regulates both the PVN and the CN. We predicted that by developing a method to double stain for calcitonin gene-related peptide (CGRP) and oxytocin using Alkaline Phosphatase Substrate, we would obtain a clear map of this circuitry in the brain. The Alkaline Phosphatase Substrate was successfully used to double stain for CGRP and oxytocin. This staining was inconclusive for determining morphological detail but was necessary for colocalization. (1)Department of Psychology, Howard University, Washington, DC 20059 (2)Department of Psychology, Stony Brook University, Stony Brook, NY 11794-2500
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	Roberto Droz-Rosario Carolina, PR University of Puerto Rico at Rio Piedras Senior Biology Faculty Advisor: Stella Tsirka, Associate Professor Department of Pharmacological Sciences
Assessment of tPA expression interfering constructs in mouse glioma GL 261 and human breast cancer MDA 231cell lines. Roberto M. Droz-Rosario(1), Iordanis Gravanis(2), Diandra Ayala(2), Stella E. Tsirka(2) Tissue plasminogen activator (tPA) is a secreted protease (Gravanis, et al. 2005) that mediates biochemical reactions inducing extracellular matrix degradation associated with degenerative diseases. It has also been found that tPA intervenes in the activation of microglia, the immunocompetent cells of the CNS parenchyma, after a trauma has occurred. Upon activation, microglia synthesize and secrete more tPA, so an amplifying effect is observed. To study the role and functions of tPA, we decided to decrease the levels of tPA using RNA interference. We used the following RNAi constructs, pEGFP H1x2 i3 and H1x2 i4, H1x2 i1 and H1x2 i2, that interfere with tPA expression in the mouse glioma cell line GL 261 and human breast cancer cells MDA 231, respectively. To determine the effectiveness of the constructs in knocking down the expression of tPA, we transfected the constructs into the cells and selected for the stable expression of the constructs using antibiotic resistance selection. We then isolated DNA and RNA, and employed PCR, RT- PCR, Electrophoresis, Western Blotts, Amidolytic, Proteolytic and Zymographic Assays to assess RNA, protein and tPA enzymatic activity levels. Preliminary results demonstrate that the currently used RNAi constructs are not completely effective in suppressing tPA expression. Development of new siRNA constructs using corresponding primers is required to achieve knocking down of tPA in cells to obtain a better understanding of tPA interaction with components of established models for cancer and degenerative diseases. (1)Department of Biology, University of Puerto Rico at Rio Piedras, Rio Piedras, PR 00931 (2)Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651
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	Tracey Evans Deer Park, NY SUNY Old Westbury Incoming PhD Student Chemistry Faculty Advisor: John Mak, Associate Professor Marine Sciences Research Center
Preliminary Study of Long-Chained (C6 and up) Hydrocarbon Produced from Thalassiosira pseudonana Phytoplankton Tracey Evans(1), John Mak(2) Our study looks at long-chained hydrocarbons (C6 and up) produced by dissolved organic compounds (DOC) released by phytoplankton. These hydrocarbons combined with other ambient air particles to form aerosols. Aerosols are known to cause poor visibility, health problems, and climate changes. The study conducted with the use of a mass spectrometer was done to detect and determine the presence of these hydrocarbons in the overhead air space of two tanks. One tank contained filtered pond water with phytoplankton while the second contained only filtered pond water. Both tanks were placed in the sun to activate any photochemical reaction to release these hydrocarbons which were then collected on Tenax TA. The Tenax TA was then placed on the preconcentration system and heated to 180°C that desorbed any hydrocarbons and sent them thru two traps submerged in liquid nitrogen. All collected hydrocarbons were then sent onto the gas chromatography system where it was heated from 50°C to 150°C in a 10 degree per minute ramp then left at 150°C for five minutes. As the sample came off the GC column it went onto the Quadrupole mass spectrum system for analysis. Study resulted in the observation of hydrocarbons being seen on the mass spectrum from phytoplankton. The next step is quantitative analysis to determine the hydrocarbons which were seen with the use of know spectrums. (1)Department of Chemistry, SUNY College at Old Westbury, PO Box 210, Old Westbury, NY 11568-0210 (2)Marine Sciences Research Center, Stony Brook University, Stony Brook, NY 11794-5000
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	Nadia Gomez Hyattsville, MD Stony Brook University Senior Mechanical Engineering Faculty Advisor: J. Carlos Rojo, Assistant Profesosr Department of Materials Science and Engineering
Nucleation and Growth of GaN Nanostructures by Chemical Vapor Deposition Nadia Gomez(1), Joan Carvajal(2) and J. Carlos Rojo(2) Gallium nitride (GaN) nanostructures ranging from nanowires to nanoporous particles have been synthesized using a chemical vapor deposition (CVD) approach. The nucleation and growth of these nanostructures on silicon and boron nitride (BN) substrates have been carried out for different flows of ammonia (NH3) [50 - 100 sccm] and temperatures [750° C – 900° C] at a constant pressure of 15 torr. Varying the time of each experiment has allowed for the analysis of the growth patterns evolution of these nanostructures. The direct reaction of NH3 and gallium under varying conditions results in two main different crystal morphologies depending on the substrate choice and operational conditions. GaN nanowires grow on both BN and silicon substrates with diameters that range from 15 to 60 nm depending on the distance from the source of Ga. In addition, 1-2 µm size particles with nanoporous structures have also been successfully grown on boron nitride (BN) substrates. Nanoporous structures were never observed on silicon (Si) dipped in the catalyst, nickel nitrite ((Ni (N0-3) 2)). The obtained results were examined using scanning electron microscopy (SEM). (1)Deparment of Mechanical Engineering, Stony Brook University, Stony Brook, NY 11794-2300 (2)Department of Materials Science, Stony Brook University, Stony Brook, NY 11794-2275
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	Nilsson Holguin Queens, NY Trinity College Incoming PhD Student Biomedical Engineering Faculty Advisor: Partap Khalsa, Associate Professor Department of Biomedical Engineering
Development of a scaling relationship to extrapolate neurophysiological data from feline to human spines during lateral bending. Nilsson Holguin1(1), Allyson Ianuzzi(2), Partap S. Khalsa(2) Rationale: Low back pain (LBP) is an epidemic in the U.S., with more than 80% of the adult populationexperiencing a severe episode during their lifetime. An etiology of LBP is the facet joint capsule (FJC), which is the ligament that encapsulates the bony, articulating joints of the spine. The lumbar FJC is innervated with mechanically sensitive neurons and functions to provide both proprioceptive and nociceptive (i.e., pain) information to the central nervous system. For ethical reasons, it is not possible to directly measure the responses of human FJC afferents, hence animal models are utilized. However, the neurophysiological data from a cat model cannot be directly extrapolated to humans because the relationship between the biomechanics of the two species is unknown. Therefore, the broad aim of this project is to develop a scaling relationship, based on the biomechanics between cat and human lumbar spines, for use in extrapolating neurophysiological data from cat to human. Methods: Human (n=3) and cat (n=6) cadaveric lumbar spines were received, measured, potted and actuated in lateral bending (LB).The parameters measured were the yield force, torque (M) at L5-S1 in humans and L7-S1 in cats, moment of inertia (I) of the lumbar disc, and intervertebral angulations which was used to calculate the torsional joint stiffness (E). The radii of curvature (µ) of the spine specimens during LB at the torque limit were calculated as: µ = EI/M, and compared using regression techniques. If proven statistically viable, the radius of curvature would be used as a method of scaling the torque limits. Results: A comparison of linear regression lines did not detect a significant difference (p= 0.84) between the cat and human data, suggesting that the way in which the radii of curvature (µ) change in both species is similar. The overall coincidence of the relationship had a low correlation when the data was pooled (R² = 0.07). The fit was significantly improved by comparing the data separately (p=0.05). The radius of curvature relationship (µ) was well correlated in the cat spines (R² = 0.73) but less so in the human spines (R² =0.25 ). Discussion and Conclusions: The data suggest that while the radii of curvature (µ) of both species are not significantly different, one relationship alone cannot be used for both species, as the combined R² and p value suggest. This could be due to a difference in the curvature in the neutral posture between the species. However, if the difference in neutral position is introduced, a single relationship could be used to describe both data when the geometries of the specimens are introduced as a method for comparison. Future studies will include collecting data from additional human spines, which should improve the fit. The current study, along with further studies, will aid in the understanding and formulation of a scaling relationship between human and cat spines under LB and allow neurophysiological data from cats to be used to project how human nociceptors and mechanoreceptors respond to analogous biomechanical motions. (1) Department of Biomedical Engineering, Trinity College, Hartford, CT 06106 (2) Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794-8018
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	Aluta Khanyile Bronx, NY Stony Brook University Junior Pharmacology Faculty Advisor: Howard Crawford, Assistant Professor Department of Pharmacological Sciences
The Notch-1 pathway affects the expression of Matrix Metalloproteinase-7 in Pancreatic cancer Aluta Khanyile, Howard Crawford The expression of MMP-7 is seen in the early stages of pancreatic tumor progression. MMP-7 is found in significant amounts in 99‰ of patients suffering from pancreatic cancer. Notch, a protein that is critical for cell fate decisions and differentiation, has also been found to be significant in the formation of pancreatic cancer. Notch acts as a transcription factor via its interaction with the DNA-binding protein, CBF. We set out to test the hypothesis that MMP-7 is regulated by Notch. EBNA-2 is an adenoviral protein that activates promoter regions that have CBF binding sites. SUH-L is a mammalian protein that inhibits promoter regions that have CBF binding sites. By overexpressing EBNA-2 and SUH-L with a MMP-7 promoter/reporter construct we found that SUH-L has the ability to turn down the MMP-7 promoter, whereas EBNA-2 had no effect. While these data are consistent with Notch being a possible regulator of MMP-7 expression, the ineffectiveness of EBNA-2 needs to be examined further. Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651
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	Rachel A. Matundan Queens, NY College of Mount St. Vincent Incoming PhD Student Biochemistry Faculty Advisor: Caroline Kisker, Associate Professor Department of Pharmacological Sciences
Determining the active site divalent cation coordination for the C-terminal endonuclease domain of UvrC Rachel A. Matundan(1), James J. Truglio(2),Caroline Kisker(2) The nucleotide excision repair (NER) mechanism involves the recognition and repair of many types of damaged DNA present in both eukaryotic and prokaryotic cells. In prokaryotes the three main proteins involved are UvrA, UvrB and UvrC. UvrA and UvrB are responsible for recognition of the damage, whereas the proper function of UvrC is imperative to the repair process because it involves the catalytic domains necessary for the incision of the damaged genetic material. The structure of the C-terminal endonuclease domain of UvrC (amino acids 339-557 of UvrC from Thermotoga maritima) has been recently solved by x-ray crystallography. The active site is similar to that of RNAse H suggesting a similar enzyme mechanism. The active site pocket contains four highly conserved residues: D367, D405, D429 and H488. In the crystal structure, a Mn2+ ion is bound solely to H488. Mutation of this residue to Ala, Asp or Glu results in a UvrC variant that is still partially active but significantly impaired compared to wildtype UvrC. In this study, we sought to determine the crystal structures of mutants H488E and H488A in context of the UvrC C-terminal domain to obtain detailed information about the role of this residue in catalysis. (1)Department of Biochemistry, College of Mount Saint Vincent, Riverdale, NY 10471 (2)Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651
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	Rosemary Orhue Bronx, NY Stony Brook University Senior Biology, Sociology Faculty Advisor: Robert S. Haltiwanger, Professor Department of Biochemistry and Cell Biology
Are O-Glucose Modifications Important for the Mouse Notch1 Signaling Pathway? Rosemary Orhue(1), Dr. Robert Haltiwanger (2), Dr. Aleksandra Nita-Lazar (2) Complex carbohydrates play important roles in regulating signal transduction during development. Notch, a protein located at the plasma membrane that is responsible for significant cell fate decisions, is modified by sugars and these sugars affect its signaling pathway. Defects in Notch cause devastating diseases such as T-cell leukemia, CADASIL, and congenital heart defects. Notch has thirty-six tandem epidermal growth factor (EGF) repeats in its extracellular domain, many of which have sites where O-glucose sugars are attached through glycosylation. To determine if O-glucose modifications are important for Notch signaling, mutations were made at specific highly conserved EGF repeats (10,13, 14,16 and 27) containing O-glucose sites to prevent O-glucose modifications. Cos-7 cells were transfected with wild type or mutant Notch, co-cultured with ligand and control cells, and evaluated in signaling assays to determine if O-glucose was important for Notch to function. Here we show that when the O-glucose site at EGF repeat 27 was mutated, delta-activated Notch signaling decreased, while Jagged-activated Notch signaling remained the same. (1)Department of Biology, Stony Brook University, Stony Brook, NY 11794-5110 (2)Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215
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	Mayra B. Pastore-Patel Martinez, CA San Francisco State University Senior Biochemistry Faculty Advisor: Guangwei Du, Research Scientist Department of Pharmacological Sciences
Role of Phospholipase D in Actin Cytoskeletal Reorganization of Epithelium Cells Mayra B. Pastore-Patel(1), Michael A. Frohman(2) and Guangwei Du(2) Phospholipase D (PLD) is involved in many intra/extra-cellular signaling transduction processes. The signaling relay is achieved through the production phosphatidic acid (PA) and choline from phosphodiester hydrolysis of phosphatidylcholine. There are two PLD isoforms in mammalian cells, PLD1 and PLD2. PLD activity has been reported to be involved in epithelium cell tumorogenesis, but the mechanism remains unclear. One possibility consists of promoting cytoskeletal rearrangement. Epithelium cells connect to one another through cellular junctions such as adherens and tight junctions. An important change that occurs in cancerous cells is their lost of cell-cell attachment through cytoskeletal remodeling. My current project was to investigate the potential role of PLD1 and PLD2 in actin cytoskeletal rearrangement during tumor progression. The function of PLD in NMuMG epithelium cells was explored through overexpression and downregulation of the individual isoforms. First, I examined the subcellular localization of each protein using EGFP-tagged-PLD expression constructs, and assayed changes in cell-cell tight junctions as a consequence of the overexpression. My results revealed that PLD1 localizes to the perinuclear region and PLD2 to the plasma membrane, consistent with previous reports in other cell types. However, there is not enough evidence to conclude PLD overexpression alters actin cytoskeleton. To downregulate PLD expression, I adapted a new RNA interference (RNAi) technology. This technology uses short hairpin RNA (shRNA) expressed as a fusion with the human microRNA- 30 (mir-30) precursors and driven by a CMV promoter. To date, several constructs expressing PLD1 or PLD2 shRNA have been assayed with Western Blotting after transient cell transfection. Subsequent analysis allowed me to conclude that shRNAs successfully downregulated the protein's overexpression. My next step is to generate tetracycline-regulated constructs, using pTRE-Tight and PIRES2-EGFP, and producing RNAi to induce downregulation of PLD. (1)Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Ave, San Francisco, CA 94132 (2)Department of Pharmacological Sciences and The Center for Developmental Genetics, Stony Brook University, Stony Brook, NY 11794-5140
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	Kestrel Perez Bridgehampton, NY Southampton College Incoming PhD Student Marine Biology Faculty Advisor: Stephan Munch, Assistant Professor Marine Sciences Research Center
Estimating Heritability in the Atlantic Silverside (Menidia menidia) Kestrel Perez(1), Stephan B. Munch(2) Larval fish can face strong positive selection for fast growth as rapid growth leading to a larger size earlier is beneficial to survival. Environmental factors are commonly known to influence larval growth rates, however little is understood about how parental genotype affects variation in a phenotypic offspring trait, such as length. To investigate the level of heritability in growth rate variation, we created 55 families of Atlantic silversides (Menidia menidia) by strip- spawning adults. All environmental conditions were held constant to ensure minimal growth rate variation due to environmental factors. We measured lengths of larvae at 1, 5, 10, and 24 days post hatch. An estimate of heritability was determined from growth rate variation among full sib and half sib families. The maximum likelihood estimate of heritability (h²) was 0.07 with a 95‰ confidence limit from 0 to 0.55. The mean Bayesian estimate of heritability (E (h²/data) was 0.21 (σ (h²/data) = 0.16) which corresponds with the expected result for organisms facing positive selection. This estimate of heritability in Atlantic silversides has important implications for better understanding larval growth. (1)Department of Marine Biology, Southampton College, Southampton, NY 11968 (2)Marine Sciences Research Center, Stony Brook University, Stony Brook, NY 11794-5000
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	Kacey-Ann Thompson Queens, NY SUNY Old Westbury Junior Biology Faculty Advisor: Caroline Kisker, Associate Professor Department of Pharmacological Sciences
Crystal Structure of Xanthine Dehydrogenase Variants from Rhodobacter Capsulatus Kacey-Ann Thompson(1), Jennifer Doebbler(2), Caroline Kisker(2) The oxidation of hypoxanthine to xanthine followed by the oxidation of xanthine to uric acid is catalyzed by Xanthine Dehydrogenase (XDH). The enzyme is inhibited by the clinical drug allopurinol, which becomes oxidized to alloxanthine and cannot be further oxidized, thus acting as a tight inhibitor. Mutations at one of the two key electron transfer residues, E232Q or E730Q hinders the functionally-important electron transfer mechanism, as does the exchange of tungsten for the molybdenum in the cofactor, and prevents the enzyme from turning over the substrate. Crystal structures of the XDH variants (E232Q, E730Q, and the Tungsten derivative) having either hypoxanthine or xanthine bound to them, will give a clearer illustration of how the enzyme functions, as well as giving further insight to developing a new and safer clinical drug to treat hyperuricemia, that is, the build up of uric acid. Pseudo two-dimensional diamond shaped XDH variant crystals were grown by vapor diffusion and soaked in hypoxanthine or xanthine solutions. These crystals were taken to the National Synchrotron Light Source at Brookhaven National Laboratory for x-ray diffraction analysis. We were unable to determine the crystal structure as the crystals did not give sufficient diffraction results, however future attempts are in progress. (1)Department of Biological Sciences, SUNY College at Old Westbury, PO Box 210, Old Westbury, NY 11568-0210 (2)Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11795-5115
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	Wasnard Victor Westbury, NY Columbia University Incoming Master´s Student Biomedical Engineering Faculty Advisor: Stefan Judex, Assistant Professor Department of Biomedical Engineering
An Automated Method for Quantification of Trabecular Bone Architecture via Micro-Computed Tomography Wasnard Victor(1) Stefan Judex(2) INTRODUCTION: Quantification of trabecular bone architecture is essential for the study, diagnosis, and ultimate treatment of bone disease. A state-of-the-art method for bone analysis is micro-computed tomography. As the number of bones to scan increases, bone analysis can become a lengthy process. Trabecular bone must be separated from cortical bone to distinctly analyze its quantity and microarchitecture by manually contouring each slice, in a cumbersome manner. The goal of this study was to modify the Image Processing Language (IPL) program of the Scanco micro-ct system to automatically segment trabecular bone from cortical bone faster than the manual way. MATERIALS AND METHODS: Two-dimensional bone slices of the metaphyseal region of the femur from female mice were obtained via a micro-ct scanner (vivaCT 40, Scanco Medical, Switzerland) from a genetic bone study¹. IPL was used to construct three-dimensional images of the bone and provide quantitative data. Both manual and automatic segmentation procedures were performed for a basis of comparison. For the automatic segmentation, different parameters for a Gauss kernel filter such as standard deviation, and support, were varied to obtain optimal bone architecture. RESULTS: Each high resolution bone scan consisted of 144 slices for each bone. For these 144 slices the separation of trabecular bone from cortical bone by manually drawing contour lines for each slice took approximately one hour. Analysis of the mice consisted of three different bone scans for the left and right femur, totaling 864 scans, resulting in six hours for manual segmentation per mice. For the automatic segmentation, on the other hand, a contour line was drawn for the first slice and then iterated forward through the slices. This iteration process took approximately thirty minutes, resulting in three hours for automatic segmentation per mice. The automatic segmentation produced best results when segmentation parameters were increased from default values of 2 and 4 to a standard deviation value of 50, and support value of 14 respectively. As the values increased, more trabecular bone regions were visualized, and the images produced by the manual and automatic segmentation procedures became more comparable. Increasing these values too far pass 50 and 14 however, overestimated the amount of cortical bone, and we visualized less trabecular bone. DISCUSSION: In this study an automated method for segmenting bone was investigated as a means to quantify trabecular bone architecture faster than current manual methods of segmentation. Results indicate that certain parameters for automatic segmentation can realize comparable segmentation to that of current manual methods. However, quantified data via automatic segmentation must be investigated further. (1)Department of Biomedical Engineering, Columbia University, New York, NY 10027-8904 (2)Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794-2580 ¹Gene Expression Patterns in Bone After 4 Days of Hind-limb Unloading in Two Inbred Strains of Mice. Zhong N.