Medicine and Health Sciences Commons^™

The Pseudomonas Aeruginosa Magnesium Transporter Mgte Inhibits Transcription Of The Type Iii Secretion System, Gregory G. Anderson, Timothy L. Yahr, Rustin R. Lovewell, George A. O'Toole

Dartmouth Scholarship

Pseudomonas aeruginosa is an opportunistic pathogen that causes life-long pneumonia in individuals with cystic fibrosis (CF). These long-term infections are maintained by bacterial biofilm formation in the CF lung. We have recently developed a model of P. aeruginosa biofilm formation on cultured CF airway epithelial cells. Using this model, we discovered that mutation of a putative magnesium transporter gene, called mgtE, led to increased cytotoxicity of P. aeruginosa toward epithelial cells. This altered toxicity appeared to be dependent upon expression of the type III secretion system (T3SS). In this study, we found that mutation of mgtE results in increased T3SS …

Interferon Regulatory Factor 3-Dependent Pathways Are Critical For Control Of Herpes Simplex Virus Type 1 Central Nervous System Infection, Vineet D. Menachery, Tracy J. Pasieka, David A. Leib

Dartmouth Scholarship

The initiation of the immune response at the cellular level relies on specific recognition molecules to rapidly signal viral infection via interferon (IFN) regulatory factor 3 (IRF-3)-dependent pathways. The absence of IRF-3 would be expected to render such pathways inoperative and thereby significantly affect viral infection. Unexpectedly, a previous study found no significant change in herpes simplex virus (HSV) pathogenesis in IRF-3^−/− mice following intravenous HSV type 1 (HSV-1) challenge (K. Honda, H. Yanai, H. Negishi, M. Asagiri, M. Sato, T. Mizutani, N. Shimada, Y. Ohba, A. Takaoka, N. Yoshida, and T. Taniguchi, Nature 434:772-777, 2005). In contrast, the …

The Importance Of Examining Movements Within The Us Health Caresystem: Sequential Logit Modeling, Chioun Lee, Stephanie L L. Ayers, Jennie Jacobs Kronenfeld, Jemima A. Frimpong, Patrick A. Rivers, Sam S. Kim

Dartmouth Scholarship

Utilization of specialty care may not be a discrete, isolated behavior but rather, a behavior of sequential movements within the health care system. Although patients may often visit their primary care physician and receive a referral before utilizing specialty care, prior studies have underestimated the importance of accounting for these sequential movements. The sample included 6,772 adults aged 18 years and older who participated in the 2001 Survey on Disparities in Quality of Care, sponsored by the Commonwealth Fund. A sequential logit model was used to account for movement in all stages of utilization: use of any health services (i.e., …

Primary Human Mammary Epithelial Cells Endocytose Hiv-1 And Facilitate Viral Infection Of Cd4+ T Lymphocytes, Stephanie M. Dorosko, Ruth I. Connor

Dartmouth Scholarship

The contribution of mammary epithelial cells (MEC) to human immunodeficiency virus type 1 (HIV-1) in breast milk remains largely unknown. While breast milk contains CD4(+) cells throughout the breast-feeding period, it is not known whether MEC directly support HIV-1 infection or facilitate infection of CD4(+) cells in the breast compartment. This study evaluated primary human MEC for direct infection with HIV-1 and for indirect transfer of infection to CD4(+) target cells. Primary human MEC were isolated and assessed for expression of HIV-1 receptors. MEC were exposed to CCR5-, CXCR4- and dual-tropic strains of HIV-1 and evaluated for viral reverse transcription …

The Staphylococcus-Specific Gene Rsr Represses Agr And Virulence In Staphylococcus Aureus, Sandeep Tamber, Dindo Reyes, Niles P. Donegan, Joseph D. Schwartzman, Ambrose L. Cheung, Guido Memmi

Dartmouth Scholarship

The expression of virulence factors in Staphylococcus aureus is tightly coordinated by a vast network of regulatory molecules. In this report, we characterize a genetic locus unique to staphylococci called rsr that has a role in repressing two key virulence regulators, sarR and agr. Using strain SH1000, we showed that the transcription of virulence effectors, such as hla, sspA, and spa, is altered in an rsr mutant in a way consistent with agr upregulation. Analysis of RNAIII expression of the agr locus in rsr and rsr-sarR mutants indicated that rsr likely contributes to agr expression independently …

Mononucleosis And Antigen-Driven T Cell Responses Have Different Requirements For Interleukin-2 Signaling In Murine Gammaherpesvirus Infection, Michael Molloy, Weijun Zhang, Edward Usherwood

Dartmouth Scholarship

Interleukin-2 (IL-2) has been implicated as being necessary for the optimal formation of primary CD8⁺ T cell responses against various pathogens. Here we have examined the role that IL-2 signaling plays in several aspects of a CD8⁺ T cell response against murine gammaherpesvirus 68 (MHV-68). Exposure to MHV-68 causes a persistent infection, along with infectious mononucleosis, providing a model for studying these processes in mice. Our study indicates that CD25 is necessary for optimal expansion of the antigen-specific CD8⁺ T cell response but not for the long-term memory response. Contrastingly, IL-2 signaling through CD25 is absolutely required …

Anti-Hiv Activity In Cervical-Vaginal Secretions From Hiv-Positive And -Negative Women Correlate With Innate Antimicrobial Levels And Igg Antibodies, Mimi Ghosh, John V. Fahey, Zheng Shen, Timothy Lahey, Susan Cu-Uvin, Zhijin Wu, Kenneth Mayer, Peter F. Wright, John C. Kappes, Christina Ochsenbauer, Charles R. Wira

Dartmouth Scholarship

Background: We investigated the impact of antimicrobials in cervicovaginal lavage (CVL) from HIV(+) and HIV(2) women on target cell infection with HIV. Since female reproductive tract (FRT) secretions contain a spectrum of antimicrobials, we hypothesized that CVL from healthy HIV(+) and (2) women inhibit HIV infection.

Methodology/Principal Findings: CVL from 32 HIV(+) healthy women with high CD4 counts and 15 healthy HIV(2) women were collected by gently washing the cervicovaginal area with 10 ml of sterile normal saline. Following centrifugation, anti- HIV activity in CVL was determined by incubating CVL with HIV prior to addition to TZM-bl cells. Antimicrobials and …

The Efficacy And Safety Of Insulin-Sensitizing Drugs In Hiv-Associated Lipodystrophy Syndrome: A Meta-Analysis Of Randomized Trials, Siddharth H. Sheth, Robin J. Larson

Dartmouth Scholarship

HIV-associated lipodystrophy syndrome (HALS) is characterized by insulin resistance, abnormal lipid metabolism and redistribution of body fat. To date, there has been no quantitative summary of the effects of insulin sensitizing-agents for the treatment of this challenging problem. We searched MEDLINE, the Cochrane Library, clinical trial registries, conference proceedings and references for randomized trials evaluating rosiglitazone, pioglitazone or metformin in patients with evidence of HALS (last update December 2009). Two reviewers independently abstracted data and assessed quality using a standard form. We contacted authors for missing data and calculated weighted mean differences (WMD) and 95% confidence intervals (CI) for each …

Role Of Pknb Kinase In Antibiotic Resistance And Virulence In Community-Acquired Methicillin-Resistant Staphylococcus Aureus Strain Usa300, S. Tamber, J. Schwartzman, A. L. Cheung

Dartmouth Scholarship

The regulation of cellular processes by eukaryote-like serine/threonine kinases is widespread in bacteria. In the last 2 years, several studies have examined the role of serine/threonine kinases in Staphylococcus aureus on cell wall metabolism, autolysis, and virulence, mostly in S. aureus laboratory isolates in the 8325-4 lineage. In this study, we showed that the pknB gene (also called stk1) of methicillin-resistant S. aureus (MRSA) strain COL and the community-acquired MRSA (CA-MRSA) strain USA300 is involved in cell wall metabolism, with the pknB mutant exhibiting enhanced sensitivity to β-lactam antibiotics but not to other classes of antibiotics, including aminoglycosides, ciprofloxacin, …

Cd4 T-Cell Suppression By Cells From Toxoplasma Gondii-Infected Retinas Is Mediated By Surface Protein Pd-L1, Elizabeth Charles, Sunil Joshi, John D. Ash, Barbara A. Fox

Dartmouth Scholarship

In the inflamed retina, CD4(+) T cells can cause retinal damage when they are not properly regulated. Since tissue expression of major histocompatibility complex (MHC) class II and costimulatory molecules is a key mechanism for regulating effector T cells, we tested the hypothesis that upregulation of these proteins in the retina contributes to the regulation of CD4 T cells. Here we report that in retinas infected with the protozoan parasite Toxoplasma gondii, MHC class II is upregulated on infiltrating leukocytes as well as on resident retinal cells, including photoreceptors. Flow cytometric analysis indicated that B7 costimulatory family members (CD80, CD86, …

Effect Of Calcium Supplements On Risk Of Myocardial Infarction And Cardiovascular Events: Meta-Analysis, Mark J. Bolland, Allison Avenell, John A. Baron, A. Grey

Dartmouth Scholarship

Objective: To investigate whether calcium supplements increase the risk of cardiovascular events.

Osteoporosis is a major cause of morbidity and mortality in older people. Calcium supplements margin- ally reduce the risk of fracture, and most guidelines recommend adequate calcium intake as an integral part of the prevention or treatment of osteoporosis. Consequently, calcium supplements are commonly used by people over the age of 50. Observational stu- dies suggest that high calcium intake might protect against vascular disease, and the findings are consis- tent with those of interventional studies of calcium sup- plements thatshow improvementin some vascular risk factors. In contrast, …

Pseudomonas Aeruginosa Evasion Of Phagocytosis Is Mediated By Loss Of Swimming Motility And Is Independent Of Flagellum Expression, Eyal Amiel, Rustin R. Lovewell, George A. O'Toole, Deborah A. Hogan, Brent Berwin

Dartmouth Scholarship

Pseudomonas aeruginosa is a pathogenic Gram-negative bacterium that causes severe opportunistic infections in immunocompromised individuals; in particular, severity of infection with P. aeruginosa positively correlates with poor prognosis in cystic fibrosis (CF) patients. Establishment of chronic infection by this pathogen is associated with downregulation of flagellar expression and of other genes that regulate P. aeruginosa motility. The current paradigm is that loss of flagellar expression enables immune evasion by the bacteria due to loss of engagement by phagocytic receptors that recognize flagellar components and loss of immune activation through flagellin-mediated Toll-like receptor (TLR) signaling. In this work, we employ bacterial …

Optimal Bone Strength And Mineralization Requires The Type 2 Iodothyronine Deiodinase In Osteoblasts, J. H. D. Bassett, Alan Boyde, Peter G. T. Howell, Richard H. Bassett, Thomas M. Galliford, Marta Archanco, Holly Evans, Michelle A. Lawson, Peter Croucher, Donald L. St. Germain, Valerie A. Galton, Graham R. Williams

Dartmouth Scholarship

Hypothyroidism and thyrotoxicosis are each associated with an increased risk of fracture. Although thyroxine (T4) is the predominant circulating thyroid hormone, target cell responses are determined by local intracellular availability of the active hormone 3,5,3'-L-triiodothyronine (T3), which is generated from T4 by the type 2 deiodinase enzyme (D2). To investigate the role of locally produced T3 in bone, we characterized mice deficient in D2 (D2KO) in which the serum T3 level is normal. Bones from adult D2KO mice have reduced toughness and are brittle, displaying an increased susceptibility to fracture. This phenotype is characterized by a 50% reduction in bone …

Renin-Angiotensin System Activation Correlates With Microvascular Dysfunction In A Prospective Cohort Study Of Clinical Sepsis, Kevin C. Doerschug, Angela S. Delsing, Gregory A. Schmidt, Alix Ashare

Dartmouth Scholarship

Microvascular dysregulation characterized by hyporesponsive vessels and heterogeneous bloodflow is implicated in the pathogenesis of organ failure in sepsis. The renin-angiotensin system (RAS) affects the microvasculature, yet the relationships between RAS and organ injury in clinical sepsis remain unclear. We tested our hypothesis that systemic RAS mediators are associated with dysregulation of the microvasculature and with organ failure in clinical severe sepsis.

Structure Of Vibrio Cholerae Toxt Reveals A Mechanism For Fatty Acid Regulation Of Virulence Genes, Michael J. Lowden, Karen Skorupski, Maria Pellegrini, Michael G. Chiorazzo, Ronald K. Taylor, F. Jon Kull

Dartmouth Scholarship

Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerae. In order for V. cholerae to cause disease, it must produce two virulence factors, the toxin-coregulated pilus (TCP) and cholera toxin (CT), whose expression is controlled by a transcriptional cascade culminating with the expression of the AraC-family regulator, ToxT. We have solved the 1.9 A resolution crystal structure of ToxT, which reveals folds in the N- and C-terminal domains that share a number of features in common with AraC, MarA, and Rob as well as the unexpected presence of a buried 16-carbon fatty acid, cis-palmitoleate. The finding that …

Crystal Structure Of The Cystic Fibrosis Transmembrane Conductance Regulator Inhibitory Factor Cif Reveals Novel Active-Site Features Of An Epoxide Hydrolase Virulence Factor, Christopher D. Bahl, Christophe Morisseau, Jennifer M. Bomberger, Bruce A. Stanton, Bruce D. Hammock, George A. O'Toole, Dean R. Madden

Dartmouth Scholarship

Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other alpha/beta hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-A resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across the …

Progressive Changes In Microglia And Macrophages In Spinal Cord And Peripheral Nerve In The Transgenic Rat Model Of Amyotrophic Lateral Sclerosis, David J. Graber, William F. Hickey, Brent T. Harris

Dartmouth Scholarship

The role of neuroinflammation in motor neuron death of amyotrophic lateral sclerosis (ALS) is unclear. The human mutant superoxide dismutase-1 (hmSOD1)-expressing murine transgenic model of ALS has provided some insight into changes in microglia activity during disease progression. The purpose of this study was to gain further knowledge by characterizing the immunological changes during disease progression in the spinal cord and peripheral nerve using the more recently developed hmSOD1 rat transgenic model of ALS. Using immunohistochemistry, the extent and intensity of tissue CD11b expression in spinal cord, lumbar nerve roots, and sciatic nerve were evaluated in hmSOD1 rats that were …