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Biomedical Sciences Seminar Series

Winter 2009 Poster Presentation
February 6, 2009 at 1 pm
Physical Sciences Lobby

Poster #1- Yanett Roman

Epistatic analysis of the dyrk1b gene in the Nodal signaling pathway
Yanett Roman

The Nodal signaling pathway is essential for normal vertebrate development. The Nodal signaling pathway plays essential roles in the formation and specification of the mesoderm and endoderm, neural patterning of the anterior-posterior axis and the specification of left-right asymmetry. The Nodal ligands nodal-related 1 (ndr1) and nodal-related 2 (ndr2), the Nodal antagonists lefty1 (lft1) and lefty2 (lft2), as well as the mesoderm marker goosecoid (gsc), are all downstream targets of Nodal signaling. Previously, we demonstrated that the dual-specificity tyrosine-regulated kinase 1b (dyrk1b) gene is required for expression of lft1 and lft2 (lft1/2) in zebrafish embryos. Likewise, dyrk1b knockdown animals had an expanded expression of gsc, suggesting an increased amount of signaling through the Nodal pathway. These data indicate that dyrk1b acts as a negative regulator in the Nodal signaling pathway. Interestingly, preliminary data on the expression of the Nodal ligands ndr1 and ndr2 suggest a slight decrease in ndr2 expression in dyrk1b knockdown animals. Therefore, we hypothesize that dyrk1b functions upstream of ndr2 and lft1/2. To test that hypothesis, we will perform an epistasis experiment where ndr2 is overexpressed in a dyrk1b knockdown animal. Overexpression of ndr2 is known to cause overexpression of lft1/2. If our hypothesis is correct, overexpression of ndr2 should rescue lft1/2 expression in dyrk1b knockdown animals. Conversely, if ndr2 overexpression does not rescue lft1/2 expression in dyrk1b knockdown animals this latter result would support a role for dyrk1b in lft1/2 expression downstream of ndr2 in the Nodal signaling pathway.


Poster #2-Saray Felix

Effects of Amino Acid Substitutions in the F Protein of Sendai Virus on F Protein Cleavability and Plaque Formation of the Virus
Saray Felix

Sendai virus is a negative, non-segmented, enveloped RNA virus that belongs to the Paramyxoviridae family. Wild-type Sendai virus causes a localized respiratory tract infection in mice, while its variant, F1-R causes a systemic infection. Two determinants have been correlated with the pantropic phenotype of F1-R. One determinant is the enhanced cleavability of the fusion protein, attributed to two or more mutations in the F gene. The enzyme capable of cleaving wt F is found only in the lungs; cleavage is required for viral infectivity. Enhanced cleavability of F1-R F allows F1-R to replicate in different organs. Another determinant is bipolar budding, attributed to two mutations in the M gene. Bipolar budding of F1-R allows the virus to gain access to the bloodstream through basement membrane release where it can disseminate and cause a systemic infection. A revertant of F1-R virus containing an F115 amino acid reversion to wt sequence was isolated; it no longer had enhanced cleavability of F or cause a systemic infection in mice. It was originally hypothesized that F115 mutations along with the two M gene mutations were needed for F1-R pathogenicity. Upon testing the hypothesis, results suggested that one or more of the other amino acid substitutions in the fusion protein are required for the enhanced cleavability of F1-R F and the pantropism of F1-R. This study will test the hypothesis that F115 and F116 amino acid substitutions in F1-R F will confer enhanced cleavability on F1-R F. With site-directed mutagenesis F116 amino acid substitution (Arg to Lys) will be inserted on pRGV-1 (contains F115 gene mutation) to generate pRGV-8. Using reverse genetics RGV-8 will be created and studied in tissue culture with and without trypsin. Mutagenesis protocol suggests DNA concentrations between 10-50 ng. The 19.2 kb plasmid is unstable and replicates slowly due to its large size, therefore larger concentrations were tested. Previous concentrations tested have been either low (10 ng dsDNA) or possibly high (100-250 ng dsDNA). Our results thus far indicate that the pRGV-1 plasmid concentrations (ng) need to be sufficiently high in order to obtain efficient results and high yield after mutagenesis.  



Poster #3- Deisy Contreras

Role of Protein Kinase-A and Casein Kinase Pathways in Candida albicans Resistance to Antimicrobial Peptides

Abstract: Candida albicans is considered to be an imperfect fungus frequently encountered as a commensal organism of the human digestive system and vaginal tract as well as in other warm-blooded animals (Scherer and Magee, 1990). C. albicans has the ability to propagate in two distinct morphological patterns, either as a mycelium or as a yeast cell (Pla et al., 1996). Candida is able to cause a variety of infections, which depend on the overall nature of the infected host. Therefore, C. albicans causes opportunistic infections, which means that the agent becomes infectious when there is some change in the environment of the body that will allow the organism to grow out of control resulting in candidiasis. As one of the major players in innate immunity, antimicrobial peptides are known to have a strong effect on a majority of bacteria, fungi and viruses (Braff et al., 2005). Antimicrobial peptides are classified as small cationic polypeptides that hinder the growth and spread of microorganisms. Histatins (Hsts) and defensins, which contribute the innate host defense against candidiasis and other fungal infections are a source of alternative therapeutic agents. The yck2 gene is part of the Casein Kinase 1pathway, which has been known to play a role in the phosphorylation, which in turn allows for the ubiquitination and internalization of yeast pheromone receptor (Hicke et al., 1998) along with other cellular functions. It’s main role has been seen in cellular morphogenesis. Now, cka2 gene is a subunit of the casein kinase 2 (CK2) pathway which share similar properties to its CK1 counterpart. According to studies, the CKA2 also plays an important role in the adherence and penetration of C. albicans into oral epithelial or endothelial cells(Chiang et al., 2007) It is required for C. albicans to cause maximal damage to both oral epithelial and endothelial cells (Chiang et al., 2007). Two isoforms of the Ras-protein kinase A pathway include both the TPK1 and TPK2, which seem to play an important role in the morphological transition from yeast to hyphal formation seen in C. albicans (Park et al., 2005). Studies have shown that a deletion of both genes within the organism appears to be lethal, but the presence of either full functioning gene is enough to substantiate growth of the organism in the yeast phase of its life cycle. The SSD1 gene in C. albicans seems to act as a suppressor of the regulatory and catalytic subunits of the protein kinase pathways (Chen and Rosamond 1998; Gank et al., 2008). Our hypothesis is to see if these 3 protein Kinase genes (yck2, tpk1, tpk2, cka2 )are involved in SSD1 related protamine sensitivity. To test our hypothesis, we first screened for fungal protamine susceptibility to test for the each of the mutated phenotypes listed in Table 1. For the hypersusceptible-protamine strains, SSD1 gene fragments were PCR quantified using real time PCR (RT-PCR, with special focus on the relative quantification of the expression level of the gene as it relates to the different mutated phenotypes. The RNA extraction and RT-PCR were completed using the specified protocol RiboPure™ Yeast Rapid RNA isolation kit and the RETROscript® Kit purchased from Ambion. The final portion of the experiment included the overexpression of the SSD1 gene against the different mutated phenotypic strains and re-test for Protamine susceptibility using the procedure described in detailed in the Methods section of the poster.

Poster #4-Danilo Santamaria

Sensibility Analysis and Optimization of Heat Exchangers

Abstract: Although heat exchangers are useful in a variety of different fields, they have yet to meet the desired needs. In order to meet the needs, a new design must be modeled to optimize the heat exchanger. The main goal of this model is to increase the heat transfer rate and minimize the pressure drop of the heat exchanger. To achieve this optimized heat exchanger, one must determine the performance of the exchanger under different conditions and geometries. Both computer software and mathematical methods will be used to determine the best design that will optimize the heat exchanger. Comsol multiphysics software will be used to model the heat exchanger and the NTU method will be used to calculate the effectiveness of the design.  


Poster #5-Eric Cabral

Eliminating background noise in cell phones using the Matched Filter

Author: Eric Cabral Abstract: There has been some level of research done to eliminate background noise while using a cell phone with various techniques such as using two microphones or using time frequency filters. However, the results of their research have not been perfected to eliminate the background noise. This research will consist of learning the theory of the matched filter, how to implement it and use LabVIEW to design and test the matched filter with several  


Poster #6-Henry Valle

Synthesis and Characterization of Dendrimer Based Novel Next Generation MRI Contrast Agents Using Adamantane (GdIII) Complexes

Abstract: In situations where there is insufficient image contrast to adequately differentiate anatomy or pathology in magnetic resonance imaging (MRI), a contrast agent is administered that usually incorporates a paramagnetic metal (most commonly gadolinium). There is a need for improved contrast agents. Most of the currently available MRI contrast agents suffer from all or most of the following limitations: 1) they are able to complex and exchange only one water molecule at a time; 2) it is difficult to control the solubility of their complexes; 3) it is difficult to control the bio-distribution of these complexes; 4) most of the existing small molecule MRI contrast agents are mononuclear, bearing each only one metal nucleus to assist in water relaxation. The work proposed here is the preparation of next-generation MRI contrast agents, small molecules that will bear 2, 3, And 4 metal centers, and bear functionality that will allow for control of bio-distribution and solubility in biological fluids.


Poster #7- Paul Harris

Improving the giant magnetoresistance effect by forming a natural insulating barrier for a spin-tunneling device

Abstract: Most if not all electronics are still based on a system that is driven by the charge of the electron rather than its spin characteristics. This quantum property known as the "spin", has lead to an emerging field of electronics called Spintronics. The orientation of the spin of the electrical carriers allows Spintronics to read, write and store information [1]. Spintronics plays an important role in Magnetic Random Access Memory (MRAM), which is an avenue for the future of electronic devices. MRAM is believed to be a fast nonvolatile memory device and is suppose to have a high density of dynamic RAM (DRAM). Some of flaws seen in DRAM is that it loses data when the power is turned off, which will be remedied with the incorporation of MRAM into technologies. MRAM is one of the many applications to this project. The current research in this field is mainly focused on the exploration of new materials able to transport a coherent spin to distances up to 10²-10³ nm [2]. Our research focus will be on spin polarized transport through an insulator by using electrodes in lithographically patterned nanostructures. The giant magnetoresistance (GMR) effect can be observed in magnetic thin films, which are composed of ferromagnetic layers and nonmagnetic material as a spacer. The ferromagnetic material that will be used in our research is La0.7Sr0.3MnO3 (LSMO), which is nearly half metallic with a very high spin polarization at Fermi Surface. When the ferromagnetic layers are parallel they have a low resistance as opposed to when they are antiparallel. With an applied magnetic field the direction of the magnetization can be altered. Therefore it is the aim of this project is to have a spin polarized transport through an insulator using a half metallic manganite as a spin injector and to observe a magnetoresistance (MR) effect at room temperature.  


Poster #8-Rosa Padilla

A Methodology to Analyze a Cryogenic Application during Laser Therapy

Cryogen spray cooling (CSC) is an effective method that reduces skin damage during laser therapy in vascular lesions. The objective of this study is to develop a methodology that can be used to analyze the inverse heat conduction problem that arises in cryogenic applications during laser treatments. Heat removal will be quantified with an algorithm that will be developed to solve an inverse heat conduction problem with internal temperature measurements made within the skin. This study offers the importance in arriving with realistic solutions from our boundary conditions, once known; it can be used to develop medical devices that could promote safer laser treatments.  


Poster #9-Laura Martinez


Laura E. Martinez

MyoD is a muscle-specific transcription regulator and one of the earliest markers of myogenic commitment. It is transcribed from one of a family of four myogenesis determination genes, each of which induces myogenesis when expressed from a transgene in cultured non-muscle cells. P53, a tumor suppressor known to regulate cell cycle checkpoints and apoptosis, contributes to initiation of skeletal muscle differentiation in cultured cells but does not induce myogenesis independently of myogenic regulatory factors (MRFs). We propose and others have proposed that p53 acts as a backup for MyoD, but no one has tested this hypothesis. A corollary to this proposition is that p53 and MyoD must have some activities in regulating muscle development in common. My specific aim is to identify a suite of genome-wide regulatory activities shared by p53 and MyoD in cultured cells. Using gene transfer, our laboratory will create two cell lines that are genetically identical except that one is p53 null and MyoD positive, and the other is MyoD null and p53 positive. We will activate either p53 or MyoD, expose cells to medium used to induce myogenesis and assay for expected changes in each line. I worked with the MyoD positive cell line. Microscopic examination will be used to assess myotube formation. To confirm MyoD activity if myotubes are not observed, expression of several genes known to be activated by MyoD will be analyzed by reverse transcriptase-PCR. Once activity of MyoD was confirmed, cDNA from the MyoD cell line was prepared for analysis by a commercial microarray service to identify transcripts that are up-regulated or down-regulated by activity of MyoD in the absence of p53. A parallel study conducted by another graduate student in our laboratory identified the transcripts that are up- or down-regulated by p53 in the absence of MyoD using the other cell line. Comprehensive analysis of both transcriptomes will identify genes for which transcript accumulation is up- or down-regulated in common in the two cell lines. In this manner, we will identify candidates for redundant regulation of transcript levels by p53 for MyoD. The significance of these genes with respect to myogenesis will be investigated by literature search, and bioinformatically.  

Poster #10-Erika Garcia

Development of Sifel-based Microfluidic Devices Utilizing Electrophoretic Techniques for Chemical Separations

Department of Chemistry and Biochemistry, California State University, Los Angeles A current problem in microfluidics is that the main polymer used to fabricate microfluidic devices (MDs), poly(dimethylsiloxane) (PDMS), is not very compatible with most organic solvents. Known fluorinated polymers are more chemically robust yet are difficult to use in MD fabrication especially when using multilayer soft lithography (MSL). In this study, we describe the fabrication of microfluidic chips using a perfluoropolyether (Sifel) in a single monolithic layer. Sifel-based MDs were used for the separation of molecules in mixed organic/aqueous solvents using electrophoretic techniques. Separation and detection of a mixture containing two fluorescent compounds, fluorescein and 5,6-dicarboxy fluorescein, was carried out using a fiber-optics fluorescence set-up. Elution repeatability and detector linearity was tested by injecting single component samples and detecting the injections with the fluorescence detector. This work will develop useful analytical techniques for the analysis of bimolecular separations.  


Poster #11-Carla Cueva

Phenotypic and Genetic Characterization of Clinical Isolates of Acinetobacter baumannii from California Correctional Facilities

Acinetobacter baumannii has emerged as an important bacterial pathogen because of its acquired resistance to multiple antibiotics commonly used to treat A. baumannii infections over the past decades. Much work has been done to characterize clinical isolates of this species from hospitals world wide. However, no reports have been published which describe characteristics of A. baumannii isolates obtained from inmates of correctional facilities. To determine the phenotypic and genetic characteristics of A. baumannii isolates, we performed antibiotic susceptibility testing of 20 isolates from correctional facilities in California and subsequently evaluate their genetic relationships using pulse-field gel electrophoresis analysis. For susceptibility testing, broth microdilution method was used to determine minimal inhibitory concentrations (MIC) of 18 antibiotics against these 20 isolates. Genomic DNA was isolated and digested with restriction endonuclease Apa I. Digested genomic DNA fragments were separated using a BioRad CHEF-DRIII system. Our results indicated that 2 of the 20 A. baumannii clinical isolates exhibited multidrug resistance. The rest remain susceptible to these 18 antibiotics. Additionally, pulsed-field gel electrophoresis indicated that 8 isolates showed distinct genotypic profiles. Using antibiotic susceptibility testing and molecular typing, we intend to obtain a correlation between antibiotic resistance and genetic characteristics in these clinical isolates of A. baumannii. This relationship may aid clonal analysis of clinical bacterial pathogens based on antibiotic susceptibility and fingerprinting profiling.  


Poster #12-Jopey Contreras

Chronic Unpredictable Stress and its Effect on mRNA/BDNF and mRNA/GAP-43 Expression in the Hippocampus

It has been found that when the body is put under chronic unpredictable stress it can lead to considerable neuronal damage. It does so by reducing the expression of Brain Derived Neurotropic Factor (BDNF) and Growth Associated Protein 43 (Gap-43), both of which are located in the hippocampus. These proteins are known for supporting the survival of existing neurons and promoting the growth of new neurons (Altar, 1999; Lindsay et al., 1994). To combat this neurodegeneration, our study set out to determine if a neuron enhancing effect could be observed in experimental conditions using a chronic unpredictable stress model paired with physical exercise. Male rats were split into a control group and two experimental groups. The two experimental groups were subjected to various stressful situations (tail suspension, food/water deprivation, prolonged exposure to light, submergence in water, whole body restraint, etc). One experimental group will be allowed voluntary wheel running so that we can observe whether there is a supported growth in BDNF and Gap-43 as a result of the exercise. Using In Situ Hybridization to analyze BDNF/mRNA levels and Gap-43 expression, our results are expected to show some neuronal degeneration in the hippocampal area (C1, C2, CA3 and dendate gyrus) amongst the stress-only rat group. We also expect to see supported growth in BDNF amongst the rats that received exercise as a treatment.  


Poster #13- Maura Palacios

Phylogeography of the Caribbean ostracode, Skogsbergia lerneri, based on nuclear histone gene sequences

Ostracods are small crustaceans that exist in most aquatic environments. Skogsbergia lerneri is a marine cypridinid ostracode that is distributed widely throughout the Caribbean. A morphological and mitochondrial study of Skogsbergia from the U.S. Virgin Islands and Puerto Rico confirmed the existence of a separate cryptic species, S. crenulata, described by Poulsen in 1962. Previous studies using 16S rRNA and cytochrome oxidase I mitochondrial genes found large genetic divergences between populations throughout the Caribbean, which may represent several cryptic species. This study uses Histone 3 nuclear gene sequences to confirm previous mtDNA findings and improve resolution of the phylogeny of cryptic species of Skogsbergia in the Caribbean. Preliminary H3 results suggest that H3 is better than mtDNA for resolving relationships of Skogsbergia lineages, H3 clade structure is consistent with mtDNA clade structure, but more individuals need to be sequenced for H3 before conclusions can be made about the number of cryptic species of Skogsbergia in the Caribbean.  

Poster #14- Adrian Esqueda

The discovery of novel inhibitory compounds against human apurinic endonuclease 1 (APE1) in vitro.

Human apurinic endonuclease 1 (APE1) belongs to endonuclease family involved in the base excision pathway. APE1 is an enzyme that repairs damaged or mismatched bases in DNA by removing the base, leaving a sugar phosphate residue. APE-1 has been shown to be overexpressed in specific cancers including colon making it an ideal target for the development of new anti-cancer drugs. In combination with alkylating and oxidizing agents, it has been shown that inhibition of APE1 in cancer cells leads to a high degree of DNA damage eventually leading to apoptosis. Using an enzymatic assay and gel electrophoresis, training sets of compounds designed with an abasic DNA fragment as the template are tested for inhibition of APE1 activity.  

Caridad Wilson
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