springposter 2005






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Biomedical Sciences Seminar Series

Spring 2005 Poster Presentation

April 29, 2005 at 1 pm

Physical Sciences Lobby
Jaqueline Sanchez, Rudy Victoria, Marjannie Eloi, Carlos Rodriguez, Gina Ramirez, Sandra Alvarez, Delia Gutierrez,, Danny Chagolla, Ana Gamboa, David Hernandez, Julia Andino, Veronica Barahona, Scott Barker, Stacie Dahl, Jessica Gonzalez, Dominique Rosete, James Nunnelley, Jorge Osuna, Sandra Wong, Carlos Martinez, Jean-Carlo Roncagliolo, Milton Medina

Poster #1

Jaqueline Sanchez
MBRS-RISE Undergraduate

Buffers are solutions designed to keep the pH constant by absorption of H+ or OH- ions added to it, in such a way that the initial conditions remain unaltered. Various buffers at certain pH's were used in dithionitrobenzoate (Ellman's reagent) analysis of thiol groups. The pH's used were 6.0, 7.0, 8.0, and 9.0. We used spectrophotometry measurements at 412 nm to monitor generation of the Nitro-thiobenzoate and found that the best pH for beta mercaptoethanol reactivity with dithionitrobenzoate (DTNB) was 8.0. We tested the sensitivity of the DTNB reagent and found that we could easily detect 3.6 x 10^ -5 M of free thiol and just barely 3.6 x 10^-6 M. With further ,analysis, it was determined that a concentration of 3.6 x 10^-7 M could not be detected. We next used DTNB to determine the number of cysteine thiols present on creatine kinase. We determined the concentration of creatine kinase by spectrometryabsorbance at 280 nm. Our study demonstrates that there is one reactive thiol present per creatine kinase molecule. This is what one expects from an analysis of the crystal structure, which shows that there is only one surface accessible thiol on the protein molecule. We will use the DTNB method to determine the extent of in vitro oxidation of proteins with thiol groups on their surfaces.


Poster #2

Multidimensional Analysis of Racial Identity and Racial Perceptions Among Asians
Rudy Victoria
Biomed Prep Scholar

Abstract: The purpose of this study was to examine the underlying racial experiences that shape the identity of Asian Americans using both a quantitative and qualitative methodological approach. 140 Asian Americans from a culturally diverse west coast university participated in this study (31% males, 69% females) and were administered an anonymous questionnaire. A content analysis of participants' description of their experiences in the U.S. revealed five racial identity themes: Denial, Group Pride, Difficult, and Integrated. Most participants elaborated on issues pertaining to racism, providing further validation for Helms's (1995) assertion that racial identity develops through socialization due to racial rather than ethnic experiences.


Poster #3

Expression of the Antimicrobial Polypeptide Lysozyme in Mice in Response to Salmonella Infection as Evaluated by Immunoblot
Marjannie Eloi
MBRS-RISE Graduate Student

Innate mucosal defense contributes to the body's natural defense against millions of potential pathogens that reach the small intestine daily. Specialized epithelial cells of the small intestine called Paneth cells are involved in this defense through the secretion of various antimicrobial (poly)peptides (AMP) including lysozyme. Lysozyme has dual functions as a peptidoglycan hydrolase activity and as a membrane perturbing amphipathic cationic peptide resulting in the destruction of bacteria cell wall and membranes, respectively. Despite the strong mucosal defenses of the small intestine, pathogenic microbes like Salmonella are able to overcome this barrier. Salmonella typi causes typhoid fever in humans, while Salmonella enterica serovar Typhimurium (ST) causes a typhoid fever-like infection in mice. Previous studies in Dr. Salzman's laboratory in collaboration with Dr. Porter's laboratory demonstrated that wild-type ST, but not mutant strains of ST effected a down regulation of lysozyme and cryptdins, another family of antimicrobial peptides, in mouse small intestine. Mice express two genes for lysozyme, P-lysozyme that is secreted by Paneth cells and M-lysozyme that is secreted by myeloid cells, white blood cells that are part of the innate immune defense and specialized in microbial killing. In a previous study (Salzman et al, 2003) which showed a down regulation of lysozyme following Salmonella infection of mice, it was not clear, which type of lysozyme was down regulated. A down regulation of P-lysozyme only would support the hypothesis that ST interferes locally with Paneth cells AMP production. On the other hand, a down regulation of M-lysozyme would suggest that ST exerts a much broader effect on intestinal immune defenses. In the laboratory of Dr. Salzman, mice were orally infected with a high dose of (1 x 108) ST. Eighteen hours post infection, the mice were sacrificed, their small intestine were removed and further processed for mRNA quantification in the Salzman laboratory. In the Porter laboratory analysis of protein quantitative immunoblotting of tissue extracts was done. We compare the lysozyme contents, and the relative lysozyme expression in myeloid cells versus Paneth cells within the different mouse groups. Since it has been shown for other intestinal pathogens that virulence factor expression and pathogenciticy can be temperature dependent, ST grown at 27C and at 37C was used in these studies. Based on our previous experience we hypothesize that a growth temperature of ST at 37C will cause an increase in virulence factors while lower incubation temperatures will not permit expression of ST virulence factors.


Poster #4

Perceived Personal Control and its relationship to anxiety: Report from Sri Lanka
Carlos Rodriguez
MBRS-RISE Graduate Student

Research has clearly established that exposure to violence results in a host of negative psychological outcomes. However, trauma exposure alone does not account for differences between youth who develop Psychopathology and those who do not. Other factors such as perceptions of control may mediate and moderate psychological outcomes. In turn, perceived personal control may differ depending upon gender and religious affiliation, and may be greatly impacted by exposure to war. In the present study the relationship between, perceived personal control, exposure to violence and anxiety was studied among school children in Sri Lanka. Participants were recruited from Jaffna, a city in the north greatly effected by a 20-year ethnic strife, and Colombo, the commercial capital and the seat of influence and economy in the south. We hypothesized that there would be significant differences in perceptions of personal control based on religious affiliation, gender, and region, and that perceived personal control, exposure to violence, gender and religions affiliation would be significantly associated with anxiety. A survey was completed by 780 school children (mean age = 13.3 years) from 6th through 13th grade, from Jaffna and Colombo (females = 65%). Overall 54% of the group endorsed perceiving a sense of personal control. Analyses of group differences revealed no significant based on religion and gender. However there was a significant difference between regions, with fewer youth from Jaffna endorsing perceptions of personal. Regression analyses revealed that perceived personal control, exposure to violence, and religious affiliation but not gender significantly contributed to anxiety scores. Together the variables explained for 15% of the variance in anxiety scores. Perceived sense of personal control was more predictive of anxiety than exposure to violence. The results support a developmental psychopathology model, which suggest that proximal and distal factors other than the traumatic event can mediate, or moderate the relationship between trauma exposure and psychological outcomes.


Poster #5

Preparation of Building Blocks for Tetraamino-Adamantane Dendrimers
Gina Ramirez
MBRS-RISE Undergraduate



Poster #6

Synergistic Activity between Lysozyme and Fatty Acids:
A Novel Mechanism of Innate Immunity
Sandra Alvarez
MBRS-RISE Undergraduate

Abstract: Innate immunity plays a major role in preventing bacterial invasions through our mucosal surfaces. Among the key factor are antimicrobial (poly) peptides (AMPs), amphipathic molecules with a positive net charge and membrane disrupting activity. AMPs such as defensins and lysozyme can directly kill microorganisms by binding to the anionic cell membrane of bacteria and then embedding their hydrophobic domains into the bacterial target membrane. Lysozyme is also well known for its enzymatic, peptidoglycan hydrolyzing activity. However, mucosal secretions contain also lipids and even though there have been reports on the antimicrobial activity of lipids and altered lipid profiles in certain chronic infections such as cystic fibrosis (CF), lipids have not yet been investigated as integral components of host defense. Reportedly, CF patients who suffer from chronic lung infections with Pseudomonas aeruginosa have lower concentrations of the free fatty acids linoleic and docosahexaenoic acid, but not a reduction of AMPs. We hypothesized that AMPs and fatty acids may act synergistically against P. aeruginosa and employed a fluorescence based metabolic assays to measure the accumulated metabolic activity of P. aeruginosa in the presence or absence of lysozyme or human beta-defensin HBD-1 and/or selected free fatty acids for 20 hours in a saline supplemented phosphate buffer. Our data show that docosahexaenoic acid act synergistically with lysozyme against P. aeruginosa supporting that lipids play an important role in host defense.


Poster #7

Peer Relationships Among Latino College Students: Obstacles or Sources of Support?
Delia M. Gutierrez

MBRS-RISE Graduate Student

Abstract:Surveys with 67 Latino college students (50 female, 17 male) showed that having more friends in college is positively associated with college self-efficacy and adjustment even when controlling for high-school GPA. Although friends in college was also related to college GPA, this relationship was mediated by high school GPA.


Poster #8

Optimizing the Binding Site of a Novel Photo-reversible Calcium Chelator
David Hernandez
MBRS-RISE Graduate Student

Abstract: Many efforts have been made in understanding oscillations in cytosolic calcium concentration, but few have explored the effect of these oscillations on their targets at the molecular level.  Our laboratory is currently designing molecules with a photochromic switch that would be able to encapsulate and release Ca2+ in response to light.  These molecules, pictured below, would then be used to study the Ca2+ oscillations in vitro or in vivo.  Form B is hypothesized to have a significantly lower Ca2+ affinity than form A.  That is, multiple convergent ligands should be necessary in order for the molecule to bind Ca2+ selectively and strongly.  In order to test this hypothesis, control molecules resembling form B have been synthesized and characterized.  Dissociation constants for Mg2+, Ca2+ and Sr2+ were determined by UV-vis titration, and compared to those of form A.  These results will guide the design of future generations of photoswitches.   


Poster #9

The Effect of Robotic Training on BDNF mRNA Expression and Hindlimb Stepping in
the Spinally Transected Rat
Sandra Wong
MBRS-RISE Undergraduate

Abstract:Studies have shown that treadmill training improves stepping ability in spinally transected animals and there is evidence that the improved stepping is accounted by training-induced plasticity in the lumbar spinal neurons. Our overall objective was to enhance the effectiveness of treadmill training using a robotic device to train the hindlimbs of adult, spinally transected (ST) rats to step and study the effects of robotic training on BDNF mRNA expression in the lumbar spinal cord. A commercially available robotic device (Robomedica Inc.) was used to train the hindlimbs during a step cycle. Robotic arms attached to the ankles were programmed to move the hindpaw in a trainer-determined trajectory pattern during each training session (20 minutes/day, 5 days/week). To determine if these improvements in stepping were associated with biochemical changes in the lumbar spinal cord, we will next use non-radioactive in situ hybridization to study the distribution of BDNF and mRNA. If training results in an increased distribution of BDNF mRNA in spinal neurons, it would indicate a possible role for neurotrophins in the training-induced plasticity that occurs following ST.


Poster #10

CdTe Quantum Dots as Photosensitizer Carriers
Ana Soledad Gamboa
MBRS-RISE Graduate Student

Abstract:Sensitizers deposited on the surfaces of thiol-capped CdTe quantum dots were synthesized and have shown to effectively generate singlet oxygen through the process of photosensitization. These results suggest that CdTe quantum dots have potential as a useful vehicle for the delivery of photosensitizer agents in photodynamic therapy.


Poster #11

Probing Interaction of Solvents with SB-C18
Chromatographic Column Material Using Xe-129 NMR
Danny Chagolla
MBRS-RISE Graduate


Poster #12

Synthesis and Purification of the Heterogeneous Catalyst Precursor
James Nunnelley
MBRS-RISE Undergraduate

Abstract: Synthesis of enantioselective catalysts necessitates effective synthesis and purification of precursors. Effective catalysts are usually very strong Lewis acids and must remain in an environment that contains little to no moisture or oxygen. Since this is also the case with most of the precursors, a great challenge to this endeavor is to purify the crude product without introducing moisture or oxygen into the system. Three attempts to synthesize and purify Tetrakisdimethylzirconium(IV) precursor complexes are discussed, in this study. Sublimation of saw a 43.4% yield; air-contaminated, dry extraction saw a 0% yield; and air-sensitive dry extraction saw 80% yield.


Poster #13

Triquinoxiline and Diquinoxaline Incorporated Crown Ethers
Jorge Osuna

Abstract: The synthesis of crown ethers had made a significant impact on the study of supramolecular chemistry since Charles Peterson first studied the cation-complexation properties of crown ethers in the mid-1960's.  Incorporation of a crown ether into a variety of scaffolds can modify the shape of the crown ether.  Thus, the cation-binding ability and selectivity of a given crown ether can be affected.  We report here the synthesis of tri and diquinoxaline cavitand incorporated crown ethers.


Poster #14

Jean-Carlo Roncagliolo

Abstract: Site-directed mutagenesis is a valuable tool that can be used in elucidating structure-function relationships in proteins. This technique was employed to investigate the regulatory properties of phosphoenolpyruvate carboxylase (PEPc) from maize. PEPc is an essential photosynthetic enzyme in C4 plants, whose function is to incorporate carbon dioxide into organic molecules during photosynthesis. The mutation introduced was the replacement of a charge group (lysine), with a polar group (glutamine) at residue 189. The mutants' response to known activators such as glycine, and glucose-6-phosphate, and inhibitors such as malate were tested using enzyme kinetic assays. Results obtained include a 7-fold reduction in the affinity of the mutant for the inhibitor malate, a 6-fold decreased affinity of the mutant for the activator glucose-6-phosphate and a dramatic reduction in the maximum activation caused by glycine. This research was supported by NIH-MARC grant T364GM08228.

Poster #15

Adenosine-Cavitand Hybrid Molecules
Jessica Gonzalez
MBRS-RISE Undergraduate

Abstract: Biological systems exhibit exquisite selectivity in the recognition process. Preorganization and cooperativeness of functional groups often play a crucial role in biological reactions. The inherent preorganization and synthetic modularity of resorcin[4]arene cavitands make them promising building blocks for constructing multifunctional enzyme models. There has been increasing interest in developing biologically active synthetic receptors or enzyme mimics based on the resorcin[4]arene cavitand. We report here the synthesis and characterization of the first resorcin[4]arene cavitand-adenosine nucleoside hybrid and preliminary solubility information in preparation for conformational and binding studies.


Poster #16

Quinoxaline Cavitand Incorporating Crown Ethers
Carlos Martinez
MBRS-RISE Undergraduate

Abstract: Crown ethers have a long history in host-guest chemistry. They bind metal ions as well as ammonium cations. Tetraquinoxaline cavitands are vase-shaped molecular containers which undergo a drastic conformational change to a kite-shaped molecule with no cavity under the appropriate conditions. Our group reported in 2004 a new procedure to synthesize tri- and diquinoxaline cavitands.

We have now incorporated crown ethers into either the triquinoxaline cavitand (one crown), or the diquinoxaline cavitand (two crowns). The crowns contain either 4, 5 or 6 oxygen atoms. The synthesis of five new crown ether cavitands and their conformational studies will be reported.


Poster #17

Mass Characterization of Halogens in Air at Atmospheric Pressure
Stacie Dahl
Beckman Scholar

Abstract: .We have developed a new interface for use with a commercially available ion-trap mass spectrometer equipped with atmospheric pressure chemical ionization (APCI-MS). The new interface uses a mechanical pump to draw gaseous analyte through a glass manifold and into the corona discharge area of the APCI-MS. This novel method of delivering a gaseous sample at atmospheric pressure directly to the MS has been used to obtain real-time measurements of Br2 and Cl2 over synthetic seawater ice. The ion intensity of a halogen gas measured by the MS is affected by both the pumping rate and the position of the glass manifold. The MS signals for Br2 are linear in the 0.1 to 10.6 ppbv range, and the estimated 3 sigma detection limit is 20 pptv. The MS signals for Cl2 are linear in the 0.2 to 25 ppbv range, and the estimated 3 sigma detection limit is 1 ppbv. This lab-based technique is suitable to be the basis for a portable field-based design. Such a design, a miniaturized instrument, will help elucidate the role of seawater snow and ice surfaces on the photochemical production of Br2 and Cl2 in the high Arctic.


Poster #18

The Characterization of Silica Gel Supported Zirconium(IV) complexes
Veronica Barahona
MBRS-RISE Undergraduate

Abstract:The immobilization of chiral complexes supported on silica gel to form a heterogeneous chiral Lewis acid catalyst is our main focus. Currently, the reaction between silica gel and tetrakis(dimethylamido)zirconium(IV) is been used as an intermediate between silica gel and the silica gel supported chiral complex. Silica gel has different numbers of surface hydroxide groups that are sensitive to temperature. The elemental analysis of the products gives us a direct understanding of the actual coordination that Zr will have when immobilized. Our results indicate that when silica gel is dried at 125C, Zr(N(CH3)4 (I) loses three amido ligands to form three µ-oxo bonds to the silica gel surface, as confirmed by C/H/N analysis and solid state 13C and 29Si NMR. The remaining amido ligand reacts with phenethyl alcohol at room temperature. The solid state NMR spectrum of silica gel supported phenylethyl alcohol zirconium(IV) (II) shows results consistent with this process, although some amido ligands remain un-reacted. Our current work focuses on the effectiveness of (II) as a catalyst for the [4+2] cycloaddition, and the effect that variant temperatures have on silica gel coordination modes.


Poster #19

Quinoxaline Cavitand Incorporating Crown Ethers
Scott Barker
MBRS-RISE Undergraduate

Abstract:Crown ethers have a long history in host-guest chemistry. They bind metal ions as well as ammonium cations. Tetraquinoxaline cavitands are vase-shaped molecular containers which undergo a drastic conformational change to a kite-shaped molecule with no cavity under the appropriate conditions. Our group reported in 2004 a new procedure to synthesize tri- and diquinoxaline cavitands.

We have now incorporated crown ethers into either the triquinoxaline cavitand (one crown), or the diquinoxaline cavitand (two crowns). The crowns contain either 4, 5 or 6 oxygen atoms. The synthesis of five new crown ether cavitands and their conformational studies will be reported.


 Poster #20

Mutations in the M and F Genes of Sendai Virus Variants Allow the Viruses
to Cause Systemic Infections in Mice
Milton Medina

Abstract: Sendai virus (SeV) serves as the prototype of the paramyxoviridae family, which includes many human viruses and as such there is much that can be learned from it that may become relevant to the study of human pathogens. Wild-type (wt) Sendai virus (SeV) causes a pneumotropic infection in mice, while a variant of SeV, F1-R, causes a pantropic infection. The first determinant correlated with F1-R's unusual behavior is related to the cleavage of the viral fusion (F) protein, a necessary step for viral fusion and entry into the host cell. Wt F protein is cleaved at amino acid 116 by Tryptase Clara, which is only found in lung epithelium. In contrast, F1-R's F protein is cleavable by ubiquitous proteases. F1-R F has six different amino acid changes including one at amino acid 115 (Arg to Pro), which has been shown to contribute to the enhanced cleavability of F1-R. The second is related to the budding behavior of the virus. Wt virus buds predominantly from the apical domain of polarized cells while F1-R buds in a bipolar fashion. Thus, in the bronchial epithelia, some virus is released into the basement membrane where it can presumably gain quick access to the bloodstream for dissemination. When F1-R's matrix (M) protein was individually expressed in tissue culture, the microtubule network of the cell was disrupted leading to bipolar transport of F and bipolar budding of the virus. Two amino-acid substitutions at residues 128 (Asp to Gly) and 210 (Ile to Thr) in the M protein of F1-R may be responsible for this. A "reverse genetics" recovery system was used to generate mutant viruses with the defined mutations in the M gene (D128G, I210T) and F gene (G63V, N104S, R115P, R116K, Q279K, N555K) and these experiments are designed to test their tropism in vivo. wt-SeV and RGV-1 which contains one substitution in the F protein are expected to produce a solely pneumotropic infection while F1-R and RGV-0 containing substitutions in both the F and M proteins are expected to produce a pantropic infection. Although RGV-7 contains both of the M substitutions as well as the one adjacent to the cleavage site in F, tissue culture studies determined that it fails to undergo multiple cycles of replication or form plaques in LLC-MK2 cells without trypsin and therefore only cause a pneumotropic infection. Data obtained via hemagglutination assay confirms that, as expected, wt-SeV, RGV-7 and RGV1 were found solely in the lungs while F1-R and RGV-0 and were found both in the lungs as well as other tissues of the infected mice.

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