Microbiology Commons^™

Abstract: The Role Of The Novel Diguanylate Cyclase Pg_0686 In Oxidative Stress Resistance In Porphyromonas Gingivalis W83, Alexia Danielle Ximinies

Loma Linda University Electronic Theses, Dissertations & Projects

The survival/ adaptation of Porphyromonas gingivalis to the inflammatory environment of the periodontal pocket requires an ability to overcome oxidative stress. Several functional classes of genes, depending on the severity and duration of the exposure, were induced in P. gingivalis under H2O2-induced oxidative stress, including the PG0686 gene which was upregulated ca. 10-fold. In addition, its upregulation was also observed in the presence of oxygen and nitric oxide. This study is aimed to further characterize the function of this gene in response to H2O2. PG_0686, annotated as a hypothetical protein of unknown function, is a 60 kDa protein with a …

The Role Of The Filifactor Alocis Hypothetical Protein Fa1654 In Oxidative Stress Resistance, Malissa Makaylia Mangar

Loma Linda University Electronic Theses, Dissertations & Projects

The survival/adaptation of Fillifactor alocis, a fastidious gram positive asaccharolytic anaerobe in the inflammatory environment of the periodontal pocket, requires an ability to overcome oxidative stress. Moreover, emerging observations suggest its pathogenic characteristics are highlighted by its capacity to survive in the oxidative-stress microenvironment of the periodontal pocket and its likely ability to modulate the microbial community dynamics. There is still a significant gap in our understanding of F. alocis mechanism of oxidative stress resistance and its impact on the virulence and pathogenicity of the microbial biofilm. The pathogenicity of F. alocis may be impacted by its response to oxidative …

Investigating The Role Of The Three N-Terminal Hamp Domains Of The Aer2 Chemoreceptor From Pseudomonas Aeruginosa, Selina Anaya

Loma Linda University Electronic Theses, Dissertations & Projects

Pseudomonas aeruginosa is a ubiquitous environmental bacterium and opportunistic human pathogen. It readily adapts to changing environmental conditions with the aid of 26 chemoreceptors that signal to four distinct chemosensory systems. The Aer2 chemoreceptor from P. aeruginosa is an O2 sensor implicated in stress responses, virulence and fine-tuning the chemotaxis (Che) system. Aer2 is the sole chemoreceptor of the Che2 chemosensory system, which forms complexes at the cell pole during stationary phase. Aer2 is soluble, yet membrane-associated and displays an unusual arrangement with its PAS sensing domain sandwiched between three N-terminal and two C-terminal HAMP domains. HAMP domains are widespread …

Chitosan As An Immune Modulator: Therapeutic Potential In Cerebral Amyloidopathies, Tanya Larissa Cupino

Loma Linda University Electronic Theses, Dissertations & Projects

Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA) are neurodegenerative diseases that are pathologically defined by accumulations of amyloid beta (Aβ) in the brain parenchyma and vascular walls, respectively. CAA comorbidity occurs in more than half of advanced AD cases. Aβ can activate complement, an enzymatic cascade that terminates in a cytolytic pore called membrane attack complex (MAC). Protectin (CD59) is a GPI-anchored glycoprotein that physically interrupts formation of MAC. At autopsy, individuals with AD and CAA have high levels of MAC and normal to low levels of CD59 in the tunica media of affected blood vessels. We proposed the …

Characterization Of Fgf-Mediated Sonic Hedgehog Expression During Limb Development, Billy A. Watson

Loma Linda University Electronic Theses, Dissertations & Projects

Crosstalk between Fibroblast Growth Factors (FGFs) and Sonic hedgehog (SHH) is essential for proper limb development; however, the molecular mechanisms involved in this process remain unclear. Via comparative transcriptome analysis and gene knockdown and overexpression studies, we identified the transcription factor Lim homeobox 2 (LHX2) as an intermediate in FGF-directed SHH expression. We determined that FGF signaling was necessary for LHX2 expression and demonstrated that LHX2 is a primary transcription target of FGF signaling through the RAS and AKT pathways. Additionally, loss of LHX2 in the distal limb results in decreased SHH expression and a truncated limb within 24 hours …

Pas Signaling Mechanisms In Aer And Aer2, Darysbel Garcia

Loma Linda University Electronic Theses, Dissertations & Projects

PAS domains are widespread signal sensors that share a conserved three-dimensional αβ fold that consists of a central β-sheet flanked by several α- helices. The aerotaxis receptor Aer from Escherichia coli and the Aer2 chemoreceptor from Pseudomonas aeruginosa both contain PAS domains. Aer senses oxygen (O2) indirectly via an FAD cofactor bound to its PAS domain, while Aer2 directly binds O2 to its PAS b-type heme cofactor. The Aer and Aer2 PAS domains both interact with a signal transduction domain known as a HAMP domain. The PAS-HAMP arrangement differs between Aer and Aer2, with Aer- PAS residing adjacent to its …

Comparative Studies Of Tslp And Il-7 In Normal Early Human Neonatal And Adult B Cell Development, Terry-Ann Milford

Loma Linda University Electronic Theses, Dissertations & Projects

Defining the role of cytokines in promoting human B cell development is important for understanding B cell leukemia and for developing strategies to restore B cell production that is lost during some therapies. The purpose of this study was to investigate the roles of the IL-7R ligands, thymic stromal lymphopoietin (TSLP) and IL- 7, in the early stages of normal postnatal and adult human B cell development. Using novel in vitro and in vivo model systems, we show that TSLP and IL-7 are able to expand B cell precursors individually and in combination from CB hematopoietic stem cells. In this …

The Use Of Surface Cytokines As Biomarkers In B Cell Mediated Autoimmune Diseases, Abby Jones Weldon

Loma Linda University Electronic Theses, Dissertations & Projects

RA and SLE are B cell-mediated autoimmune diseases dominated by autoantibodies that affect over 1.5 million Americans. Together RA and SLE contribute to over 29 billion in healthcare costs, therefore due to the high financial burden and physical toll of these diseases on the population, there is a critical need to effectively and efficiently diagnose and treat RA and SLE patients. The aim of our studies was to identify biomarkers and drug targets to improve the identification and treatment of RA and SLE patients. As discussed above, APRIL, BAFF and TSLP have been implicated in the pathogenesis of RA and …

Cd21 And Cd24 Co-Expression: A Translational Model Between Mouse And Human, Abigail Benitez

Loma Linda University Electronic Theses, Dissertations & Projects

Systemic Lupus Erythematosus and Rheumatoid Arthritis are B cell-mediated autoimmune diseases that afflict millions of people worldwide. B cell-targeted therapies for these diseases result in variable clinical outcomes. Thus, a need exists to better understand the dynamics of human B cell production and function. The mouse model has provided a foundation for understanding the mechanisms involved in human B cell development and autoimmune disease. However, differences in mouse and human B cells are not fully understood. Our work shows that the co-expression of CD21 and CD24, determined by 7-color flow cytometry, can be used to demarcate developmental subsets of B …

Retinoic Acid Regulation Of Thyroid Hormone Action In Bone Cells, Anjali Babbar

Loma Linda University Electronic Theses, Dissertations & Projects

Retinoic acid and thyroid hormone are known to play key roles in the regulation of endochondral ossification. However, the issue of whether these two hormones interact with each other to regulate bone functions remains to be established. We investigated how thyroid hormone and retinoic acid interact to regulate cells involved in endochondral bone formation. We demonstrate that thyroid hormone treatment stimulates differentiation of ATDC5 chondrocytes and promotes formation of mineralized nodules while retinoic acid treatment at high dose inhibits chondrocyte differentiation and formation of mineralized nodules. Furthermore, thyroid hormone induced mineralized nodule formation is inhibited by co-treatment with retinoic acid …

The Role Of The Pituitary-Adrenal Axis In G-Csf Therapy After Neonatal Hypoxia-Ischemia, Mélissa Stéphanie Charles

Loma Linda University Electronic Theses, Dissertations & Projects

Several reports indicate that the activity of the hypothalamic-pituitary-adrenal axis (HPA) as measured by the increased level of adrenocorticotropic hormone (ACTH), and corticosterone is increased after a brain insult. These hormones are the effectors secreted respectively by the pituitary and adrenal glands. It has been shown that the down-regulation of corticosterone levels can improve detrimental outcomes associated with ischemic brain injuries. Neonatal hypoxia-ischemia (HI) is a devastating perinatal event with a grim prognosis and limited therapeutic strategies. In recent studies, granulocyte-colony stimulating factor (G-CSF) has shown promise in neonatal HI investigations by improving neuromotor function and reducing apoptosis in the …

Splice Factor Sfrs6: Regulation By P53 And Effect On Il-24 Splicing, Erin L. Schmidt

Loma Linda University Electronic Theses, Dissertations & Projects

Alternative splicing of RNA transcripts is emerging as a major mechanism for expanding the proteome. Splice pattern changes are found in numerous diseases and cancers, indicating the importance of tight control over this process. While the mechanism of splicing has been described in detail, it is less clear how a cell is able to modify its splicing patterns in response to different conditions. Our lab previously demonstrated that DNA damage can induce SFRS6, the gene coding for splicing factor SRp55, thereby leading to changes in the splicing patterns of several target genes related to survival and apoptosis. We also …

Fetal Programming By Nicotine Increases Cardiac Susceptibility To Ischemic Injury, Jennifer Charlotte Alexie Lawrence

Loma Linda University Electronic Theses, Dissertations & Projects

Fetal programming is the area of study that focuses on the prenatal origins of adult onset disorders. Previous studies have associated an adverse prenatal environment with the onset of physiologic and metabolic diseases during adulthood. Fetal malnutrition, hypoxia, and exposure to drugs - such as cocaine and nicotine - have been associated with adult disease states. Cigarette smoking is the number one cause of preventable death in the developed world. Among the many dangerous chemicals found in tobacco products is nicotine, the compound responsible for the addictive nature of tobacco use. Nicotine use during pregnancy is a known cause of …

Regulation Of Pim1 Under Hypoxia In Prostate Cancer, Eva Sahakian

Loma Linda University Electronic Theses, Dissertations & Projects

A defining characteristic of solid tumors is the capacity to divide and spread under conditions of nutrient deprivation and limited oxygen availability. These microenvironmental stresses arise from structural abnormalities in tumor vessels that lead to aberrant microcirculation. Hypoxia acts as a physiological “selection pressure” in the progression of cancer by activating pathways and enhancing the expression of specific genes in tumor cells which eventually diminish their apoptotic potential. Ultimately, hypoxic microenvironment functions as a “stress factor”, selecting cells with the ability to survive and divide under anoxic conditions. The members of the PIM family of cytoplasmic serine threonine kinases are …

Structural Dynamics And Signaling Roles Of The Aer Pas And F1 Regions, Asharie J. Campbell

Loma Linda University Electronic Theses, Dissertations & Projects

The Aer aerotaxis receptor in Escherichia coli mounts such a rapid response to redox that E. coli changes its swimming behavior within 100 ms after an oxygen pulse. This receptor is a membrane-bound homodimer, and it monitors internal energy (redox) via an FAD cofactor bound to a cytoplasmic N-terminal PAS domain. Understanding PAS sensing is important, as PAS domains comprise a superfamily of more than 25,000 members from all kingdoms. This study focused on the Aer N-terminal PAS sensor, as well as the region tethering it to the membrane anchor, known as the F1. Previous genetic studies on these regions …

Localization And Expression Of The Aer Receptor In Escherichia Coli, Daniel Salcedo

Loma Linda University Electronic Theses, Dissertations & Projects

In Escherichia coli, chemotactic movement towards an energetically-favorable environment is mediated by five transmembrane chemoreceptors. These sensory proteins respond to numerous environmental signals, including amino acids, sugars, and pH. The aerotaxis receptor, Aer, is an intracellular sensor that responds to oxygen concentration and other parameters affecting cellular energy levels. Bacterial chemotaxis receptors form dimeric signaling units that organize into tetramers and hexamers and form large clusters at the cell poles. A cluster arrangement could increase receptor sensitivity by lateral communication between dimers, thus amplifying the signal from one dimer. We have shown that Aer forms dimers, trimer of dimers, …

Contribution Of Ledgf/P75 To Prostate Cancer Chemoresistance, Melanie Mediavilla-Varela

Loma Linda University Electronic Theses, Dissertations & Projects

Prostate cancer (PCa) is the second leading cause of male cancer death in the United States, and is considered a health disparity because of its disproportionate incidence and mortality in African American (AA) males. A major challenge in PCa treatment is its recurrence into hormone refractory prostate cancer (HRPC). Docetaxel is the standard of care for first line chemotherapy to HRPC. Unfortunately, most patients ultimately manifest resistance to DTX and succumb to the disease. Circumventing DTX resistance in HRPC will require better understanding of the mechanisms by which this drug kills prostate tumor cells, and the genes that promote this …

Effect Of Short Exposure Of Naoci/Edta On E. Faecalis In Extracted Human Teeth, Rylan N. Gustafson

Loma Linda University Electronic Theses, Dissertations & Projects

The purpose of this project was to study the antibacterial effect of the short exposure of 5.25% NaOCl and 17% EDTA on eight strains of Enterococcus faecalis in extracted human teeth. The crowns of 240 single rooted teeth were removed and the canals were instrumented to ISO 0.36. The canals were irrigated with 5.25% NaOCl and 17% EDTA, autoclaved and separated into eight groups of 30 teeth consisting of 20 experimental teeth, 5 positive and 5 negative controls. Each group was inoculated with one of eight different strains of E. faecalis in BHl broth and incubated for four weeks. The …

Oxidative Stress-Mediated Anticancer Activity Of Novel Ahr Modulators Af & 5f203, Lancelot S. Mclean

Loma Linda University Electronic Theses, Dissertations & Projects

Estrogen receptor positive (ER+) breast cancer tends to respond to anti-estrogen agents such as Tamoxifen. Approximately 40% of ER+ breast cancer is resistant to these agents and those that initially respond often acquire resistance. Estrogen receptor negative (ER-) breast cancer remains largely unresponsive to these agents. It is therefore vital to discover drugs that are potent in both forms of breast cancer. Aminoflavone, (5-amino-2, 3-fluorophenyl)-6,8-difluoro-7-methyl-4H-l-benzopyran-4-one; AF; NSC 686288) and 5F203, (2-[-Amino-3-methy phenyl]-5-flurobenzothiazole) are novel anticancer candidate agents that display potent in vitro and in vivo anti-proliferative activity against select human tumor cells with a unique anticancer activity profile in the …

Novel Binding Domains Mediate Binding Of Hpv 16 E6 To Fadd And Procaspase 8, Sandy S. Tungteakkhun

Loma Linda University Electronic Theses, Dissertations & Projects

To evade the host response to infection, viruses have developed means to survive and propagate. HPV 16, a causative agent of cervical cancer and of some cases of oropharyngeal cancers, is one example. We have reported that the early viral protein E6 binds to proteins necessary for propagation of the apoptotic signal following receptor/ligand interactions, such as those mediated by FADD DED and procaspase 8 DED. E6 expression leads to the dose-dependent accelerated degradation of FADD and the protection of E6-expressing cells from Fas-induced apoptosis. Surprisingly, the splice isoforms of E6, E6_large and E6*, affect the stability of procaspase …

Mechanisms Of T Helper Cell Modulation In A Simulated Space Radiation Environment, Asma Rizvi

Loma Linda University Electronic Theses, Dissertations & Projects

Exposure to solar particle events (SPEs) poses the most serious threat to astronaut health. Due to this radiation environment, exploration of the solar system beyond Earth’s orbit entails many risks for the crew on these deep space missions. Depression or dysfunction of the immune system is a major concern due to its high radio-sensitivity; potential consequences include overwhelming infection, development of cancer, fibrosis, and poor wound healing. Astronauts are also exposed to low dose/low dose rate (LDR) radiation. A three month stay at the international space station exposes them to ~ 0.05 Gy of radiation.

C57BL/6 mice received LDR gamma-radiation …

The Effect Of Radiation And Repeated Sub-Culturing On Tgf-Β1 Signaling In Frtl-5 Cells, Cheryl G. Burrell

Loma Linda University Electronic Theses, Dissertations & Projects

From our ongoing in vitro studies using the Fisher Rat Thyroid cell line-5 (FRTL-5) we recorded accelerated growth, reduced follicularization and reduction in thyroxin release that occurred as the cells were repeatedly sub-cultured. We also recorded that these changes occurred earlier and more rapidly following radiation exposure. We determined that TGF-β1 production increased under both conditions. We hypothesized that alteration in the TGF-β1 signaling pathway contributed to the changes observed in the cellular properties of FRTL-5 cells. Our objective was to examine some of the players in the TGF-β1 signaling pathway to determine whether radiation and/or repeated subculturing promoted changes …

Radiation-Induced Increases In Pkc Modulate Integrin Expression And Contribute To Fibrotic Changes, Pinal Rushikesh Pandya

Loma Linda University Electronic Theses, Dissertations & Projects

The sequences of events in fibrosis are similar to those in wound healing; however, the normal termination and resolution stages do not take place. The initial cellular response following ionizing radiation involves accumulation of the ECM (extracellular matrix) including collagen, fibronectin and the interaction of many growth factors (cytokines) with their receptors. There are a number of unanswered questions regarding many aspects of radiation-induced fibrosis, including the initial triggers and physical changes that initiate the process. We have confirmed that elevated pKC and other cellular changes following radiation are similar to those found at sites of inflammation. This information leads …

An In Vitro Model Of Ovarian Cancer: Studying The Effects Of Talc And Pycnogenol®, Amber Renée Buz'zard

Loma Linda University Electronic Theses, Dissertations & Projects

Ovarian cancer is the sixth most common cancer and accounts for more deaths than any other cancer of the female reproductive system. The American Cancer Society has suggested that poor diet, talc and industrial pollutants may increase the risk of developing ovarian cancer. Talc is ubiquitous and concern is raised about its safety, role as a possible carcinogen and known ability to cause irritation and inflammation. Due to the silent nature of ovarian cancer, chemoprevention is a high priority. The most useful chemopreventive compounds will inhibit, delay or reverse carcinogenesis, and can be taken for long periods of time with …

Synergism Of Gingipains In Endothelial Cell Adhesion Disruption And Apoptosis, Shaun Michellee Sheets

Loma Linda University Electronic Theses, Dissertations & Projects

The presence of Porphyromonas gingivalisin the periodontal pocket and the high levels of gingipain activity detected in gingival crevicular fluid could implicate a role for gingipains in the destruction of the highly vascular periodontal tissue. To explore the effects of these proteases on endothelial cells, we exposed bovine coronary artery endothelial cells (BCAEC) and human microvascular endothelial cells (HMVEC) to gingipain-active extracellular protein preparations and/or purified gingipains from P. gingivalis. Treated cells exhibited a rapid loss of cell adhesion properties that was followed by apoptotic cell death. Cleavage of N- and VE-cadherin and integrin (31 was observed in immunoblots …

Membrane Organization And Multimeric Interactions Of The Aer Receptor In E. Coli, Divya Dashrathkumar Amin

Loma Linda University Electronic Theses, Dissertations & Projects

Escherichia coli swims toward niches ideal for generating maximum energy by monitoring the environment with the aerotaxis sensor, Aer. This receptor has an N-terminal PAS domain, which is a sensor module present in a variety of proteins from all kingdoms of life (including humans). To date, the mechanism of signaling from a PAS sensor domain to a single signaling receiver domain has not been resolved. In Aer, the PAS sensor is separated from the signaling region by a membrane anchor. Most "transmembrane prediction" programs forecast a single membrane span for this membrane anchor, but such a topology is inconsistent our …

Influence Of Human Papillomavirus 16 E6 On Trail-Mediated Apoptosis, Theodore O. Garnett

Loma Linda University Electronic Theses, Dissertations & Projects

Viruses have developed sophisticated strategies to evade host defenses and facilitate the production and spread of progeny. HPV 16, whose immune evasion activities can contribute to cervical cancer, is a prime example of such a virus. In this study, we examined the influence of HPV 16 E6 on TRAIL-induced FADD-dependent and -independent pathways in two cellular models: HCT116 colon carcinoma cells and U2OS osteosarcoma cells. We show that transfection of the HPV 16 E6 oncogene into HCT116 cells provides protection from TRAIL-mediated apoptosis. Additionally, we demonstrate that the protection provided by E6 is dose-dependent because higher levels of E6 provide …

Identification And Characterization Of A Selective Inhibitor Of The Pim-1 Kinase, Sheldon Levon Holder

Loma Linda University Electronic Theses, Dissertations & Projects

The PIM-1 kinase is a serine/threonine kinase that has been implicated in the development of many human cancers, including leukemias, lymphomas, and prostate cancer. We have endeavored to identify and characterize a selective inhibitor of the PIM- 1 kinase. Such an inhibitor would have utility as a laboratory tool for the study of PIM-1 kinase function and as a template for the design of molecular therapeutics for diseases in which PIM-1 kinase activity is dysregulated.

Using phage display techniques we identified the peptide, HGVKKRPHNPYG, as a probable pseudosubstrate of the PIM-1 kinase with inhibitory activity in the low micromolar range …

Oxygen Sensing By The Aer And Tsr Receptors Of Escherichia Coli, Jessica Claire Edwards

Loma Linda University Electronic Theses, Dissertations & Projects

Escherichia coli senses the oxygen concentration of its environment via the Aer and Tsr receptors, and swims to an oxygen concentration that provides optimal energy generation. Aer and Tsr do not sense oxygen per se but, sense the internal energy state via the electron transport system (ETS) in a previously unidentified mechanism. Proton motive force (PMF) and electron flow were proposed as possible sensory signals but, distinguishing between the two was not possible, previously, in live, motile cells. I differentiated PMF from electron flow by creating a series of ETS mutant strains that express ternary combinations of i) aerotaxis receptors, …

Mechanisms Of Virulence Regulation In Porphyromonas Gingivalis W83, Elaine Ann-Marie Vanterpool

Loma Linda University Electronic Theses, Dissertations & Projects

The expression of extracellular proteolytic activities is highly regulated in both prokaryotic and eukaryotic systems. This regulation can occur at multiple levels including expression of the protease genes, secretion, processing of an inactive secreted precursor to its active form and/or the posttranslational glycosylation of the proteins. These regulatory mechanisms are vital to ensure that expression is tightly controlled. Porphyromonas gingivalis has been associated with adult periodontitis and in the development of many systematic diseases. The major virulence factors of P. gingivalis, the gingipains, are responsible for pathogenesis including degradation of complement and immunoglobulin, inactivation of cytokines and their receptors, …