bluuebunny/crossref_metadata_2025 huggingface dataset:
Claudin‐16 affects transcellular Cl− secretion in MDCK cells
Authors: Günzel Dorothee , Amasheh Salah , Pfaffenbach Sandra , Richter Jan F. , Kausalya P. Jaya , Hunziker Walter , Fromm Michael
Published: June 2009

Claudin‐16 (paracellin‐1) is a tight junction protein localized mainly in the thick ascending limb of Henle's loop and also in the distal nephron. Its defect causes familial hypomagnesaemia with hypercalciuria and nephrocalcinosis. This had been taken as an indication that claudin‐16 conveys paracellular Mg2+ and Ca2+ transport; however, evidence is still conflicting. We studied paracellular ion permeabilties as well as effects of claudin‐16 on the driving forces for passive ion movement. MDCK‐C7 cells were stably transfected with wild‐type (wt) and mutant (R146T, T233R) claudin‐16. Results indicated that paracellular permeability to Mg2+ but not to Ca2+ is increased in cells transfected with wt compared to mutant claudin‐16 and control cells. Increased basolateral Mg2+ concentration activated a transcellular Cl− current which was greatly enhanced in cells transfected with wt and T233R claudin‐16, as compared to R146T claudin‐16‐transfected or control cells. This current was triggered by the basolateral calcium‐sensing receptor causing Ca2+ release from internal stores, thus activating apical Ca2+‐sensitive Cl− channels and basolateral Ca2+‐sensitive K+ channels. Immunohistochemical data suggest that the Cl− channel involved is bestrophin. We conclude that claudin‐16 itself possesses only moderate paracellular Mg2+ permeability but governs transcellular Cl− currents by interaction with apical Ca2+‐activated Cl− channels, presumably bestrophin. As the transepithelial voltage generated by such a current alters the driving force for all ions, this may be the major mechanism to regulate Mg2+ and Ca2+ absorption in the kidney.
Potassium channel opening: a subtle two‐step
Authors: Upadhyay Sanjeev K. , Nagarajan P. , Mathew M. K.
Published: June 2009

Voltage‐gated K+ channels undergo a voltage‐dependent conductance change that plays a key role in modulating cellular excitability. While the Open state is captured in crystal structures of Kv1.2 and a chimeric Kv1.2/Kv2.1 channel, the Close state and the mechanism of this transition are still a subject of debate. Here, we propose a model based on mutagenesis combined with measurements of both ionic and gating currents which is consistent with the idea that the Open state is the default state, the energy of the electric field being used to keep the channel closed. Our model incorporates an ‘Activated state’ where the bulk of sensor movement is completed without channel opening. The model accounts for the well characterized electrophysiology of the ‘V2’ and ‘ILT’ mutations in Shaker, where sensor movement and channel opening occur over distinct voltage ranges. Moreover, the model proposes relatively small protein rearrangements in going from the Activated to the Open state, consistent with the rapid transitions observed in single channel records of Shaker type channels at zero millivolts.
Fractal Characterization of Slurry Eroded Surfaces at Different Impact Angles
Authors: Abouel-Kasem  , Al-Bukhaiti M. A. , Emara K. M. , Ahmed S. M.
Published: June 2009

In the present work, the topographical images of slurry erosion surfaces at different impact angles were quantified using fractal analysis. The study showed that the variation of fractal value of slope of linearized power spectral density with the impact angle is largely similar to the relationship between the erosion rate and the impact angle. Both the fractal value and erosion rate were maximum at 45 deg and 90 deg for ductile and brittle materials, respectively. It was found also that the variation of fractal values versus the impact angle has a general trend that does not depend on magnification factor. The fractal features to the eroded surfaces along different directions showed high directionality at oblique impact angle and were symmetrical at normal impact.
Simulation of Fretting Wear in Halfplane Geometries: Part 1—The Solution for Long Term Wear
Authors: Hills D. A. , Sackfield A. , Paynter R. J. H.
Published: June 2009

The final configuration of a cylindrical Hertzian contact, subject to oscillatory shear and undergoing wear, is studied. It is assumed that wear has proceeded for a long time, so that the final, modified contact is wholly adhered. It is shown that the extent of the final contact corresponds to that of the initial adhered region and the pressure distribution, and state of stress at the new contact edge are all derived, so that the environment in which cracks nucleate is well described.
Synthesis and Lubrication Characteristics of Aryloxycyclophosphazenes Substituted With Imidazolium
Authors: Li Jinlong , Zhou Feng , Feng Dapeng , Xia Yanqiu , Liu Weimin
Published: June 2009

A series of new aryloxycyclophosphazene derivatives substituted with imidazolium ionic liquids was synthesized. Their tribological properties were investigated on an Optimol SRV IV oscillating friction and wear tester in ambient condition. An electric field was imposed between the ball and disk to monitor the tribochemical reaction by means of “contact resistance.” These ionic liquids substituted cyclophosphazene derivatives present lower friction coefficient and wear volume loss than tetrakis-(3-trifluoromethylphenoxy)-bis(4-fluorophenoxy)cyclotriphosphazene. The polarity of ionic liquids is believed to provide strong adsorption to contact surfaces and can form a boundary lubricating film leading to friction and wear reductions. Introducing the ionic liquids to cyclophosphazene may be a new method to improve the tribological properties of cyclophosphazene derivatives.
Short Term Relaxation Modeling of Valve Stem Packings
Authors: Diany Mohammed , Bouzid Abdel-Hakim
Published: June 2009

The long term tightness performance of stuffing-box packings, used in valves, is conditioned by the capacity of its sealing material to maintain a contact pressure to a predetermined minimal threshold value. Due to the creep, this contact pressure decreases with time depending on the creep properties and the stiffness of the housing. Assessing relaxation is a key parameter in determining the tightness performance of a valve stem packing over time. An analytical model based on the packing viscoelastic behavior is developed to assess the contact pressures between the packing material and the stem and the housing and their variation with time. In parallel, an axisymmetric 2D finite element model was build to validate and support the analytical model. The valve stem packing relaxation performance is an important design parameter to consider when selecting compression packings.
Temperature and Water Vapor Pressure Effects on the Friction Coefficient of Hydrogenated Diamondlike Carbon Films
Authors: Dickrell Pamela L. , Argibay N. , Eryilmaz Osman L. , Erdemir Ali , Sawyer W. Gregory
Published: June 2009

Microtribological measurements of a hydrogenated diamondlike carbon film in controlled gaseous environments show that water vapor plays a significant role in the friction coefficient. These experiments reveal an initial high friction transient behavior that does not reoccur even after extended periods of exposure to low partial pressures of H2O and O2. Experiments varying both water vapor pressure and sample temperature show trends of a decreasing friction coefficient as a function of both the decreasing water vapor pressure and the increasing substrate temperature. Theses trends are examined with regard to first order gas-surface interactions. Model fits give activation energies on the order of 40 kJ/mol, which is consistent with water vapor desorption.
Study of Hydrostatic Mechanical Face Seals Operating in a Turbulent Rough Flow Regime
Authors: Brunetière Noël , Tournerie Bernard
Published: June 2009

The aim of this paper is to present a turbulence model that allows turbulent flows between smooth and/or rough walls to be dealt with. After analyzing available literature data, an improvement of the Elrod, Ng, and Pan turbulence model is proposed, taking into account the effect of wall asperities. This model is then applied to a hydrostatic mechanical seal that is rough on one face, operating in nonlaminar flow. The roughness is due to particle deposits occurring during the seal operation. As expected, the wall roughness leads to a decrease in leakage rate.
Material Property Identification and Sensitivity Analysis Using Micro-Indentation
Authors: Ge Long , Kim Nam H. , Bourne Gerald R. , Sawyer W. Gregory
Published: June 2009

Mechanical properties of materials in small-scale applications, such as thin coatings, are often different from those of bulk materials due to the difference in the manufacturing process. Indentation has been a convenient tool to study the mechanical properties in such applications. In this paper, a numerical technique is proposed that can identify the mechanical properties using optimization and evaluate the robustness of identified material properties using sensitivity analysis. First, two response surfaces are constructed for loading and unloading curves from the indentation experiment of a gold film on the silicon substrate. Unessential coefficients of the response surface are then removed based on the test statistics. Unlike the traditional methods of identification, the tip geometry of the indenter is included because its uncertainty significantly affects the results. In order to validate the accuracy and stability of the method, the sensitivity of the identified material properties with respect to each coefficient is analyzed. It turns out that the plastic hardening parameter is the most sensitive to the experimental data. In addition, all material parameters are sensitive to the coefficients of higher-order bases. However, their effects are diminished because the magnitudes of these coefficients are small.
Enhancement of Human Immunodeficiency Virus Type 1 Replication Is Not Intrinsic to All Polyanion-Based Microbicides
Authors: Sonza Secondo , Johnson Adam , Tyssen David , Spelman Tim , Lewis Gareth R. , Paull Jeremy R. A. , Tachedjian Gilda
Published: June 2009

Polyanion-based microbicides have been developed to prevent the sexual transmission of human immunodeficiency virus (HIV). Recent data suggest that polyanions have the capacity to enhance HIV type 1 (HIV-1) replication at threshold antiviral concentrations. Evaluation of the microbicide candidates SPL7013 and PRO 2000 revealed no specific enhancement of two CCR5 HIV-1 strains in human peripheral blood mononuclear cells compared to enfuvirtide (Fuzeon). The enhancement effect is likely to be a function of the assay conditions and is not an intrinsic property of these polyanions.
Assessment of the Effects of the Nitroimidazo-Oxazine PA-824 on Renal Function in Healthy Subjects
Authors: Ginsberg Ann M. , Laurenzi Martino W. , Rouse Doris J. , Whitney Karl D. , Spigelman Mel K.
Published: June 2009

The mechanism underlying a dose-dependent, reversible increase in serum creatinine (SC) caused by the administration of PA-824, a novel nitroimidazo-oxazine, was evaluated in 47 healthy male and female volunteers. Subjects were administered either 800 or 1,000 mg PA-824 or matching placebo once daily for 8 days. The following renal function parameters were determined before and during dosing and after a 7-day washout: SC, glomerular filtration rate (GFR; measured as the iohexol clearance), effective renal plasma flow (ERPF; measured as the para-amino hippurate clearance), filtration fraction (FF), creatinine clearance (CrCl), extraglomerular creatinine excretion (EGCE; defined as CrCl minus GFR), blood urea nitrogen (BUN), and uric acid (UA) levels. Eight days' administration of 800 or 1,000 mg PA-824 was associated with increased SC and a trend toward decreased CrCl and EGCE. SC, CrCl, and EGCE values returned to normal/baseline within 1 week's washout. GFR, ERPF, FF, BUN, and UA values were similar across groups during treatment and washout. The reversible increase in SC observed in this and earlier trials of PA-824, thus, did not appear to be the result of a pathological effect on renal function (as measured by GFR, ERPF, FF, BUN, or UA). Pharmacokinetic analyses confirmed that PA-824 exposures were similar to those in previous healthy-volunteer clinical studies. That EGCE declined maximally when drug levels were highest suggests that PA-824 causes creatinine levels to rise by inhibiting renal tubular creatinine secretion. Such an effect, considered clinically benign, has been described for several marketed drugs.
Identification and Biochemical Characterization of Small-Molecule Inhibitors ofClostridium botulinumNeurotoxin Serotype A
Authors: Roxas-Duncan Virginia , Enyedy Istvan , Montgomery Vicki A. , Eccard Vanessa S. , Carrington Marco A. , Lai Huiguo , Gul Nizamettin , Yang David C. H. , Smith Leonard A.
Published: June 2009

An integrated strategy that combined in silico screening and tiered biochemical assays (enzymatic, in vitro, and ex vivo) was used to identify and characterize effective small-molecule inhibitors ofClostridium botulinumneurotoxin serotype A (BoNT/A). Virtual screening was initially performed by computationally docking compounds of the National Cancer Institute (NCI) database into the active site of BoNT/A light chain (LC). A total of 100 high-scoring compounds were evaluated in a high-performance liquid chromatography (HPLC)-based protease assay using recombinant full-length BoNT/A LC. Seven compounds that significantly inhibited the BoNT/A protease activity were selected. Database search queries of the best candidate hit [7-((4-nitro-anilino)(phenyl)methyl)-8-quinolinol (NSC 1010)] were performed to mine its nontoxic analogs. Fifty-five analogs of NSC 1010 were synthesized and examined by the HPLC-based assay. Of these, five quinolinol derivatives that potently inhibited both full-length BoNT/A LC and truncated BoNT/A LC (residues 1 to 425) were selected for further inhibition studies in neuroblastoma (N2a) cell-based and tissue-based mouse phrenic nerve hemidiaphragm assays. Consistent with enzymatic assays, in vitro and ex vivo studies revealed that these five quinolinol-based analogs effectively neutralized BoNT/A toxicity, with CB 7969312 exhibiting ex vivo protection at 0.5 μM. To date, this is the most potent BoNT/A small-molecule inhibitor that showed activity in an ex vivo assay. The reduced toxicity and high potency demonstrated by these five compounds at the biochemical, cellular, and tissue levels are distinctive among the BoNT/A small-molecule inhibitors reported thus far. This study demonstrates the utility of a multidisciplinary approach (in silico screening coupled with biochemical testing) for identifying promising small-molecule BoNT/A inhibitors.
Continuous versus Intermittent Infusions of Ceftazidime for Treating Exacerbation of Cystic Fibrosis
Authors: Hubert Dominique , Le Roux Evelyne , Lavrut Thibaud , Wallaert Benoit , Scheid Philippe , Manach Dominique , Grenet Dominique , Sermet-Gaudelus Isabelle , Ramel Sophie , Cracowski Claire , Sardet Anne , Wizla Nathalie , Deneuville Eric , Garraffo Rodolphe
Published: June 2009

The present multicenter, randomized crossover study compared the safety and efficacy of continuous infusion with those of short infusions of ceftazidime in patients with cystic fibrosis. Patients with chronic
Pseudomonas aeruginosa
colonization received two successive courses of intravenous tobramycin and ceftazidime (200 mg/kg of body weight/day) for pulmonary exacerbation administered as thrice-daily short infusions or as a continuous infusion. The primary endpoint was the variation in the forced expiratory volume in 1 s (FEV
1
) during the course of antibiotic treatment. Sixty-nine of the 70 patients enrolled in the study received at least one course of antibiotic treatment. The improvement in FEV
1
at the end of therapy was not statistically different between the two treatment procedures (+7.6% after continuous infusion and +5.5% after short infusions) but was better after continuous ceftazidime treatment in patients harboring resistant isolates (
P
< 0.05). The interval between the course of antibiotic treatments was longer after the continuous infusion than after the short infusion of ceftazidime (
P
= 0.04). The mean serum ceftazidime concentration during the continuous infusion was 56.2 ± 23.2 μg/ml; the mean peak and trough concentrations during the short infusions were 216.3 ± 71.5 and 12.1 ± 8.7 μg/ml, respectively. The susceptibility profiles of the
P. aeruginosa
isolates remained unchanged and were similar for both regimens. Quality-of-life scores were similar whatever the treatment procedure, but 82% of the patients preferred the continuous-infusion regimen. Adverse events were not significantly different between the two regimens. In conclusion, the continuous infusion of ceftazidime did not increase its toxicity and appeared to be as efficient as short infusions in patients with cystic fibrosis as a whole, but it gave better results in patients harboring resistant isolates of
P. aeruginosa
.
Efficacy of Aerosol MP-376, a Levofloxacin Inhalation Solution, in Models of Mouse Lung Infection Due toPseudomonas aeruginosa
Authors: Sabet Mojgan , Miller Courtney E. , Nolan Thomas G. , Senekeo-Effenberger Kathy , Dudley Michael N. , Griffith David C.
Published: June 2009

Progressive respiratory failure due toPseudomonas aeruginosais the leading cause of morbidity and mortality in patients with cystic fibrosis. The pulmonary delivery of antimicrobial agents provides high concentrations of drug directly to the site of infection and attains pharmacokinetic-pharmacodynamic indices exceeding those which can be achieved with systemic dosing. MP-376 is a new formulation of levofloxacin that enables the safe aerosol delivery of high concentrations of drug to pulmonary tissues. In vivo studies were conducted to demonstrate the efficacy of MP-376 in models of mouse pulmonary infection. The superiority of aerosol dosing over systemic dosing was demonstrated in models of both acute and chronic lung infection. In a model of acute lung infection, aerosol treatment with MP-376 once or twice daily reduced the lung bacterial load to a greater extent than aerosol tobramycin or aztreonam did when they were administered at similar or higher doses. The bacterial killing by aerosol MP-376 observed in the lung in the model of acute pulmonary infection translated to improved survival (P< 0.05). In a model of chronic pulmonary infection, aerosol MP-376 had antimicrobial effects superior to those of aztreonam (P< 0.05) and effects similar to those of tobramycin (P> 0.05). In summary, these data show that aerosol MP-376 has in vivo activity when it is used to treat acute and chronic lung infections caused byP. aeruginosa.
Resistance to Colistin in
Acinetobacter baumannii
Associated with Mutations in the PmrAB Two-Component System
Authors: Adams Mark D. , Nickel Gabrielle C. , Bajaksouzian Saralee , Lavender Heather , Murthy A. Rekha , Jacobs Michael R. , Bonomo Robert A.
Published: June 2009

The mechanism of colistin resistance (Col
r
) in
Acinetobacter baumannii
was studied by selecting in vitro Col
r
derivatives of the multidrug-resistant
A. baumannii
isolate AB0057 and the drug-susceptible strain ATCC 17978, using escalating concentrations of colistin in liquid culture. DNA sequencing identified mutations in genes encoding the two-component system proteins PmrA and/or PmrB in each strain and in a Col
r
clinical isolate. A colistin-susceptible revertant of one Col
r
mutant strain, obtained following serial passage in the absence of colistin selection, carried a partial deletion of
pmrB
. Growth of AB0057 and ATCC 17978 at pH 5.5 increased the colistin MIC and conferred protection from killing by colistin in a 1-hour survival assay. Growth in ferric chloride [Fe(III)] conferred a small protective effect. Expression of
pmrA
was increased in Col
r
mutants, but not at a low pH, suggesting that additional regulatory factors remain to be discovered.
Characterization of the Plasmid-Borne Quinolone Resistance Gene
qnrB19
in
S
almonella enterica
Serovar Typhimurium
Authors: Dionisi Anna Maria , Lucarelli Claudia , Owczarek Slawomir , Luzzi Ida , Villa Laura
Published: June 2009

A
qnrB19
gene variant, carried by an IncL/M-like plasmid, was detected in a multidrug
Salmonella enterica
serovar Typhimurium human strain with reduced susceptibility to ciprofloxacin. The genetic environment around the gene was fully sequenced (20 kb). A large gene cluster, containing the
aph
,
qnrB19
, and
bla
SHV-12
-like resistance genes, is inserted inside a Tn
3
transposon.
In Vitro Activity of Antifolate and Polymorphism in Dihydrofolate Reductase ofPlasmodium falciparumIsolates from the Kenyan Coast: Emergence of Parasites with Ile-164-Leu Mutation
Authors: Kiara Steven M. , Okombo John , Masseno Victor , Mwai Leah , Ochola Isabella , Borrmann Steffen , Nzila Alexis
Published: June 2009

We have analyzed the activities of the antifolates pyrimethamine (PM), chlorcycloguanil (CCG), WR99210, trimethoprim (TMP), methotrexate (MTX), and trimetrexate (TMX) against KenyanPlasmodium falciparumisolates adapted in vitro for long-term culture. We have also assessed the relationship between these drug activities and mutations in dihydrofolate reductase (dhfr), a domain of the gene associated with antifolate resistance. As expected, WR99210 was the most potent drug, with a median 50% inhibitory concentration (IC50) of <0.075 nM, followed by TMX, with a median IC50of 30 nM. The median IC50of CCG was 37.80 nM, and that of MTX was 83.60 nM. PM and TMP were the least active drugs, with median IC50s of 733.26 nM and 29,656.04 nM, respectively. We analyzed parasitedhfrgenotypes by the PCR-enzyme restriction technique. No wild-typedhfrparasite was found. Twenty-four of 33 parasites were triple mutants (mutations at codons 108, 51, and 59), and only 8/33 were double mutants (mutations at codons 108 and 51 or at codons 108 and 59). IC50s were 2.1-fold (PM) and 3.6-fold (TMP) higher in triple than in double mutants, though these differences were not statistically significant. Interestingly, we have identified a parasite harboring a mutation at codon 164 (Ile-164-Leu) in addition to mutations at codons 108, 51, and 59. This quadruple mutant parasite had the highest TMP IC50and was in the upper 10th percentile against PM and CCG. We confirmed the presence of this mutation by sequencing. Thus, TMX and MTX are potent againstP. falciparum, and quadruple mutants are now emerging in Africa.
oqxAB
Encoding a Multidrug Efflux Pump in Human Clinical Isolates of
Enterobacteriaceae
Authors: Kim Hong Bin , Wang Minghua , Park Chi Hye , Kim Eui-Chong , Jacoby George A. , Hooper David C.
Published: June 2009

The genes for multidrug efflux pump OqxAB, which is active on fluoroquinolones, were found in human clinical isolates on a plasmid in
Escherichia coli
and on the chromosome of
Klebsiella pneumoniae
. IS
26
-like sequences flanked the plasmid-mediated
oqxAB
genes, suggesting that they had been mobilized as part of a composite transposon.
Kinetics and Phenotype of Vaccine-Induced CD8+T-Cell Responses toToxoplasma gondii
Authors: Jordan Kimberly A. , Wilson Emma H. , Tait Elia D. , Fox Barbara A. , Roos David S. , Bzik David J. , Dzierszinski Florence , Hunter Christopher A.
Published: June 2009

Multiple studies have established that the ability of CD8+T cells to act as cytolytic effectors and produce gamma interferon is important in mediating resistance to the intracellular parasiteToxoplasma gondii.To better understand the generation of the antigen-specific CD8+T-cell responses induced byT. gondii, mice were immunized with replication-deficient parasites that express the model antigen ovalbumin (OVA). Class I tetramers specific for SIINFEKL were used to track the OVA-specific endogenous CD8+T cells. The peak CD8+T-cell response was found at day 10 postimmunization, after which the frequency and numbers of antigen-specific cells declined. Unexpectedly, replication-deficient parasites were found to induce antigen-specific cells with faster kinetics than replicating parasites. The generation of optimal numbers of antigen-specific CD8+effector T cells was found to require CD4+T-cell help. At 7 days following immunization, antigen-specific cells were found to be CD62Llow, KLRG1+, and CD127low, and they maintained this phenotype for more than 70 days. Antigen-specific CD8+effector T cells in immunized mice exhibited potent perforin-dependent OVA-specific cytolytic activity in vivo. Perforin-dependent cytolysis appeared to be the major cytolytic mechanism; however, a perforin-independent pathway that was not mediated via Fas-FasL was also detected. This study provides further insight into vaccine-induced cytotoxic T-lymphocyte responses that correlate with protective immunity toT. gondiiand identifies a critical role for CD4+T cells in the generation of protective CD8+T-cell responses.
Influenza A Virus Neuraminidase Enhances Meningococcal Adhesion to Epithelial Cells through Interaction with Sialic Acid-Containing Meningococcal Capsules
Authors: Rameix-Welti Marie-Anne , Zarantonelli Maria Leticia , Giorgini Dario , Ruckly Corinne , Marasescu Monica , van der Werf Sylvie , Alonso Jean-Michel , Naffakh Nadia , Taha Muhamed-Kheir
Published: June 2009

The underlying mechanisms of the epidemiological association between influenza virus infections andNeisseria meningitidisinvasive infections are not fully understood. Here we report that adhesion ofN. meningitidisto human Hec-1-B epithelial cells is enhanced by influenza A virus (IAV) infection. A potential role of the viral neuraminidase (NA) in facilitating meningococcal adhesion to influenza virus-infected epithelial cells was examined. Expression of a recombinant IAV NA in Hec-1-B human epithelial cells increased the adhesion of strains ofN. meningitidisbelonging to the sialic acid-containing capsular serogroups B, C, and W135 but not to the mannosamine phosphate-containing capsular serogroup A. Adhesion enhancement was not observed with an inactive NA mutant or in the presence of an NA inhibitor (zanamivir). Furthermore, purified IAV NA was shown to cleave sialic acid-containing capsular polysaccharides ofN. meningitidis. On the whole, our findings suggest that a direct interaction between the NA of IAV and the capsule ofN. meningitidisenhances bacterial adhesion to cultured epithelial cells, most likely through cleavage of capsular sialic acid-containing polysaccharides. A better understanding of the association between IAV and invasive meningococcal infections should help to set up improved control strategies against these seasonal dual viral-bacterial infections.
Streptococcus pneumoniaeAutolysis Prevents Phagocytosis and Production of Phagocyte-Activating Cytokines
Authors: Martner Anna , Skovbjerg Susann , Paton James C. , Wold Agnes E.
Published: June 2009

Streptococcus pneumoniaeis a major pathogen in humans. The pathogenicity of this organism is related to its many virulence factors, the most important of which is the thick pneumococcal capsule that minimizes phagocytosis. Another virulence-associated trait is the tendency of this bacterium to undergo autolysis in stationary phase through activation of the cell wall-bound amidase LytA, which breaks down peptidoglycan. The exact function of autolysis in pneumococcal pathogenesis is, however, unclear. Here, we show the selective and specific inefficiency of wild-typeS. pneumoniaefor inducing production of phagocyte-activating cytokines in human peripheral blood mononuclear cells (PBMC). Indeed, clinical pneumococcal strains induced production of 30-fold less tumor necrosis factor (TNF), 15-fold less gamma interferon (IFN-γ), and only negligible amounts of interleukin-12 (IL-12) compared with other closely relatedStreptococcusspecies, whereas the levels of induction of IL-6, IL-8, and IL-10 production were similar. If pneumococcal LytA was inactivated by mutation or by culture in a medium containing excess choline, the pneumococci induced production of significantly more TNF, IFN-γ, and IL-12 in PBMC, whereas the production of IL-6, IL-8, and IL-10 was unaffected. Further, adding autolyzed pneumococci to intact bacteria inhibited production of TNF, IFN-γ, and IL-12 in a dose-dependent manner but did not inhibit production of IL-6, IL-8, and IL-10 in response to the intact bacteria. Fragments from autolyzed bacteria inhibited phagocytosis of intact bacteria and reduced the in vitro elimination of pneumococci from human blood. Our results suggest that fragments generated by autolysis of bacteria with reduced viability interfere with phagocyte-mediated elimination of live pneumococci.
Antigen-Specific Memory B-Cell Responses to
Vibrio cholerae
O1 Infection in Bangladesh
Authors: Harris Aaron M. , Bhuiyan M. Saruar , Chowdhury Fahima , Khan Ashraful I. , Hossain Azim , Kendall Emily A. , Rahman Atiqur , LaRocque Regina C. , Wrammert Jens , Ryan Edward T. , Qadri Firdausi , Calderwood Stephen B. , Harris Jason B.
Published: June 2009

Cholera, caused by
Vibrio cholerae
, is a noninvasive dehydrating enteric disease with a high mortality rate if untreated. Infection with
V. cholerae
elicits long-term protection against subsequent disease in countries where the disease is endemic. Although the mechanism of this protective immunity is unknown, it has been hypothesized that a protective mucosal response to
V. cholerae
infection may be mediated by anamnestic responses of memory B cells in the gut-associated lymphoid tissue. To characterize memory B-cell responses to cholera, we enrolled a cohort of 39 hospitalized patients with culture-confirmed cholera and evaluated their immunologic responses at frequent intervals over the subsequent 1 year. Memory B cells to cholera antigens, including lipopolysaccharide (LPS), and the protein antigens cholera toxin B subunit (CTB) and toxin-coregulated pilus major subunit A (TcpA) were enumerated using a method of polyclonal stimulation of peripheral blood mononuclear cells followed by a standard enzyme-linked immunospot procedure. All patients demonstrated CTB, TcpA, and LPS-specific immunoglobulin G (IgG)and IgA memory responses by day 90. In addition, these memory B-cell responses persisted up to 1 year, substantially longer than other traditional immunologic markers of infection with
V. cholerae
. While the magnitude of the LPS-specific IgG memory B-cell response waned at 1 year, CTB- and TcpA-specific IgG memory B cells remained significantly elevated at 1 year after infection, suggesting that T-cell help may result in a more durable memory B-cell response to
V. cholerae
protein antigens. Such memory B cells could mediate anamnestic responses on reexposure to
V. cholerae
.
Identification of Specific and Universal Virulence Factors in
Burkholderia cenocepacia
Strains by Using Multiple Infection Hosts
Authors: Uehlinger Susanne , Schwager Stephan , Bernier Steve P. , Riedel Kathrin , Nguyen David T. , Sokol Pamela A. , Eberl Leo
Published: June 2009

Over the past few decades, strains of the
Burkholderia cepacia
complex have emerged as important pathogens for patients suffering from cystic fibrosis. Identification of virulence factors and assessment of the pathogenic potential of
Burkholderia
strains have increased the need for appropriate infection models. In previous studies, different infection hosts, including mammals, nematodes, insects, and plants, have been used. At present, however, the extent to which the virulence factors required to infect different hosts overlap is not known. The aim of this study was to analyze the roles of various virulence factors of two closely related
Burkholderia cenocepacia
strains, H111 and the epidemic strain K56-2, in a multihost pathogenesis system using four different model organisms, namely,
Caenorhabditis elegans
,
Galleria mellonella
, the alfalfa plant, and mice or rats. We demonstrate that most of the identified virulence factors are specific for one of the infection models, and only three factors were found to be essential for full pathogenicity in several hosts: mutants defective in (i) quorum sensing, (ii) siderophore production, and (iii) lipopolysaccharide biosynthesis were attenuated in at least three of the infection models and thus may represent promising targets for the development of novel anti-infectives.
Streptococcus gordonii
Modulates
Candida albicans
Biofilm Formation through Intergeneric Communication
Authors: Bamford Caroline V. , d'Mello Anita , Nobbs Angela H. , Dutton Lindsay C. , Vickerman M. Margaret , Jenkinson Howard F.
Published: June 2009

The fungus
Candida albicans
colonizes human oral cavity surfaces in conjunction with a complex microflora.
C. albicans
SC5314 formed biofilms on saliva-coated surfaces that in early stages of development consisted of ∼30% hyphal forms. In mixed biofilms with the oral bacterium
Streptococcus gordonii
DL1, hyphal development by
C. albicans
was enhanced so that biofilms consisted of ∼60% hyphal forms. Cell-cell contact between
S. gordonii
and
C. albicans
involved
Streptococcus
cell wall-anchored proteins SspA and SspB (antigen I/II family polypeptides). Repression of
C. albicans
hyphal filament and biofilm production by the quorum-sensing molecule farnesol was relieved by
S. gordonii
. The ability of a
luxS
mutant of
S. gordonii
deficient in production of autoinducer 2 to induce
C. albicans
hyphal formation was reduced, and this mutant suppressed farnesol inhibition of hyphal formation less effectively. Coincubation of the two microbial species led to activation of
C. albicans
mitogen-activated protein kinase Cek1p, inhibition of Mkc1p activation by H
2
O
2
, and enhanced activation of Hog1p by farnesol, which were direct effects of streptococci on morphogenetic signaling. These results suggest that interactions between
C. albicans
and
S. gordonii
involve physical (adherence) and chemical (diffusible) signals that influence the development of biofilm communities. Thus, bacteria may play a significant role in modulating
Candida
carriage and infection processes in the oral cavity.
Impact of Preexisting Vector-Specific Immunity on Vaccine Potency: Characterization ofListeria monocytogenes-Specific Humoral and Cellular Immunity in Humans and Modeling Studies Using Recombinant Vaccines in Mice
Authors: Leong Meredith L. , Hampl Johannes , Liu Weiqun , Mathur Shruti , Bahjat Keith S. , Luckett William , Dubensky Thomas W. , Brockstedt Dirk G.
Published: June 2009

Recombinant live-attenuatedListeria monocytogenesis currently being developed as a vaccine platform for treatment or prevention of malignant and infectious diseases. The effectiveness of complex biologic vaccines, such as recombinant viral and bacterial vectors, can be limited by either preexisting or vaccine-induced vector-specific immunity. We characterized the level ofL. monocytogenes-specific cellular and humoral immunity present in more than 70 healthy adult subjects as a first step to understanding its possible impact on the efficacy ofL. monocytogenes-based vaccines being evaluated in early-phase clinical trials. SignificantL. monocytogenes-specific humoral immunity was not measured in humans, consistent with a lack of antibodies in mice immunized with wild-typeL. monocytogenes. Cellular immune responses specific for listeriolysin O, a secreted bacterial protein required for potency ofL. monocytogenes-derived vaccines, were detected in approximately 60% of human donors tested. In mice, while wild-typeL. monocytogenesdid not induce significant humoral immunity, attenuatedL. monocytogenesvaccine strains induced high-titerL. monocytogenes-specific antibodies when given at high doses used for immunization. Passive transfer ofL. monocytogenes-specific antiserum to naïve mice had no impact on priming antigen-specific immunity in mice immunized with a recombinantL. monocytogenesvaccine. In mice with preexistingL. monocytogenes-specific immunity, priming of naïve T cells was not prevented, and antigen-specific responses could be boosted by additional vaccinations. For the first time, our findings establish the level ofL. monocytogenes-specific cellular immunity in healthy adults, and, together with modeling studies performed with mice, they support the scientific rationale for repeatedL. monocytogenesvaccine immunization regimens to elicit a desired therapeutic effect.
Inhibition of
Staphylococcus epidermidis
Biofilm Formation by Rabbit Polyclonal Antibodies against the SesC Protein
Authors: Shahrooei Mohammad , Hira Vishal , Stijlemans Benoit , Merckx Rita , Hermans Peter W. M. , Van Eldere Johan
Published: June 2009

Several well-studied proteins with defined roles in
Staphylococcus epidermidis
biofilm formation are LPXTG motif-containing proteins. Here, we investigate the possible use of the LPXTG motif-containing protein SesC (
S
. epidermidis
surface protein C; accession no. NP_765787) as a target for antibodies to prevent biofilm formation. In vitro and in a in vivo rat model of catheter infection, gene and protein expression analysis showed that SesC is expressed more strongly in biofilm-associated cells than in planktonic cells and is expressed particularly during the late phase of in vivo biofilm formation. Polyclonal rabbit antibodies raised against SesC reduced the fibrinogen-binding ability of
S. epidermidis
RP62A and
Staphylococcus aureus
RN4220 transformants expressing SesC, inhibited in vitro biofilm formation by
S. epidermidis
strains 10b and 1457, and significantly reduced the numbers of bacteria in a 1-day-old in vivo biofilm (
P
< 0.001, one-way analysis of variance). Our findings revealed that SesC is a promising target for prevention and treatment of
S. epidermidis
biofilms because it affects both the primary attachment and biofilm accumulation phases. The precise role of SesC in biofilm formation remains to be identified.
Loa loaMicrofilariae Evade Complement Attack In Vivo by Acquiring Regulatory Proteins from Host Plasma
Authors: Haapasalo Karita , Meri Taru , Jokiranta T. Sakari
Published: June 2009

Loa loais a filarial nematode that infects humans. The adults live in subcutaneous tissues and produce microfilariae that live for several weeks in the blood circulation in order to be transmitted to another person via blood meals of a dipterian vector. As microfilariae live in continuous contact with plasma, it is obvious that they evade the complement system. We studied markers of complement activation and signs of complement regulation onLoa loamicrofilariae in vivo. The microfilariae were isolated from anticoagulated blood samples of aLoa loa-infected Caucasian patient. C1q and some mannose-binding lectin but only a limited amount of C3b or C4b fragments and practically no C5 or C5b-9 were present on the microfilariae. The covalently microfilaria-bound C3 and C4 depositions were mainly inactive iC3b, C3c, and iC4b fragments indicating that microfilariae had regulated complement activation in vivo. Also, in vitro deposition of C3b onto the microfilariae upon serum exposure was limited. The patient-isolated microfilariae were found to carry the host complement regulators factor H and C4b-binding protein on the outermost layer, so called sheath. The microfilaria-bound factor H was functionally active. Binding of the complement regulators to the microfilariae was confirmed in vitro using125I-labeled factor H and C4b-binding protein. In conclusion, our study shows thatLoa loamicrofilariae block complement activation and acquire the host complement regulators factor H and C4b-binding protein in blood circulation. This is the first time that binding of complement regulators onto nonviral pathogens has been demonstrated to occur in humans in vivo.
Association between passive jobs and low levels of leisure-time physical activity: the Whitehall II cohort study
Authors: Gimeno D , Elovainio M , Jokela M , De Vogli R , Marmot M G , Kivimäki M
Published: June 2009

Background:

There is mixed evidence on the association between psychosocial work exposures (ie, passive jobs) and physical activity, but previous studies did not take into account the effect of cumulative exposures nor did they examine different trajectories in exposure. We investigated whether exposure to passive jobs, measured three times over an average of 5 years, is associated with leisure-time physical activity (LTPA).

Methods:

Data were from working men (n = 4291) and women (n = 1794) aged 35–55 years who participated in the first three phases of the Whitehall II prospective cohort. Exposure to passive jobs was measured at each phase and LTPA at phases 1 and 3. Participants were categorised according to whether or not they worked in a passive job at each phase, leading to a scale ranging from 0 (non-passive job at all three phases) to 3 (passive job at all three phases). Poisson regression with robust variance estimates were used to assess the prevalence ratios of low LTPA.

Results:

An association was found in men between exposure to passive jobs over 5 years and low LTPA at follow-up, independently of other relevant risk factors. The prevalence ratio for low LTPA in men was 1.16 (95% CI 1.01 to 1.33) times greater for employees with three reports of passive job than for those who had never worked in passive jobs. No association was observed in women.

Conclusion:

This study provides evidence that working in passive jobs may encourage a passive lifestyle in men.
Population-based asbestosis surveillance in British Columbia
Authors: Gan W Q , Demers P A , McLeod C B , Koehoorn M
Published: June 2009

Objectives:

To investigate the use of multiple health data sources for population-based asbestosis surveillance in British Columbia, Canada.

Methods:

Provincial health insurance registration records, workers’ compensation records, hospitalisation records, and outpatient medical service records were linked using individual-specific study identifiers. The study population was restricted to individuals ⩾15 years of age living in the province during 1992–2004.

Results:

1170 new asbestosis cases were identified from 1992 to 2004 for an overall incidence rate of 2.82 (men: 5.48, women: 0.23) per 100 000 population; 96% of cases were male and average (SD) age was 69 (10) years. Although the annual number of new cases increased by 30% during the surveillance period (β = 2.36, p = 0.019), the observed increase in annual incidence rates was not significant (β = 0.02, p = 0.398). Workers’ compensation, hospitalisation and outpatient databases identified 23%, 48% and 50% of the total new cases, respectively. Of the new cases, 82% were identified through single data sources, 10% were only recorded in the workers’ compensation records, and 36% only in each of the hospitalisation and outpatient records. 84% of hospitalisation cases and 83% of outpatient cases were not included in the workers’ compensation records. The three data sources showed different temporal trends in the annual number of new cases and annual incidence rates.

Conclusions:

Single data sources were not sufficient to identify all new cases, thus leading to serious underestimations of the true burden of asbestosis. Integrating multiple health data sources could provide a more complete picture in population-based surveillance of asbestosis and other occupational diseases.
COSMIC CONSTRAINT ON RICCI DARK ENERGY MODEL
Authors: XU LIXIN , LI WENBO , LU JIANBO
Published: June 2009

In this paper, a holographic dark energy model, dubbed Ricci dark energy, is confronted with cosmological observational data from type Ia Supernovae (SN Ia), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB). By using maximum likelihood method, we found that Ricci dark energy model is a viable candidate of dark energy model with the best fit parameters: Ωm0 = 0.34 ± 0.04, α = 0.38 ± 0.03 with 1σ error. Here, α is a dimensionless parameter related to Ricci dark energy ρR and Ricci scalar R, i.e. ρR ∝ αR.
THE MSSM WITH LARGE GLUINO MASS
Authors: ANDREEV YU. M. , KRASNIKOV N. V. , TOROPIN A. N.
Published: June 2009

We study the Minimal Supersymmetric Standard Model (MSSM) with large gluino mass [Formula: see text]. In particular, we discuss the LHC supersymmetry discovery signatures with [Formula: see text], n ≥ 0 for the MSSM with large gluino mass. We show that for some relations among squark and neutralino masses leptonic signatures with [Formula: see text], n ≥ 1 do not allow to discover supersymmetry at the LHC and the only supersymmetry discovery signature is the signature with no [Formula: see text]. Moreover, for LSP mass close to squark masses the LHC discovery potential for this signature is strongly reduced.
COMPOUND DIVERSITY FUNCTIONS FOR ENSEMBLE SELECTION
Authors: KO ALBERT HUNG-REN , SABOURIN ROBERT , DE SOUZA BRITTO ALCEU
Published: June 2009

An effective way to improve a classification method's performance is to create ensembles of classifiers. Two elements are believed to be important in constructing an ensemble: (a) the performance of each individual classifier; and (b) diversity among the classifiers. Nevertheless, most works based on diversity suggest that there exists only weak correlation between classifier performance and ensemble accuracy. We propose compound diversity functions which combine the diversities with the performance of each individual classifier, and show that there is a strong correlation between the proposed functions and ensemble accuracy. Calculation of the correlations with different ensemble creation methods, different problems and different classification algorithms on 0.624 million ensembles suggests that most compound diversity functions are better than traditional diversity measures. The population-based Genetic Algorithm was used to search for the best ensembles on a handwritten numerals recognition problem and to evaluate 42.24 million ensembles. The statistical results indicate that compound diversity functions perform better than traditional diversity measures, and are helpful in selecting the best ensembles.
NONSTATIONARY DE SITTER COSMOLOGICAL MODELS
Authors: IBOHAL NG
Published: June 2009

This paper proposes a class of nonstationary de Sitter, rotating and nonrotating, solutions to Einstein's field equations with a cosmological term of variable function Λ*(u). It is found that the space–time of the rotating nonstationary de Sitter model is algebraically special in the Petrov classification of the gravitational field with a null vector, which is a geodesic, shear-free, expanding as well as nonzero twist. However, that of the nonrotating nonstationary model is conformally flat, with nonempty space.
The ins and outs of home networking
Authors: Grinter Rebecca E. , Edwards W. Keith , Chetty Marshini , Poole Erika S. , Sung Ja-Young , Yang Jeonghwa , Crabtree Andy , Tolmie Peter , Rodden Tom , Greenhalgh Chris , Benford Steve
Published: June 2009

Householders are increasingly adopting home networking as a solution to the demands created by the presence of multiple computers, devices, and the desire to access the Internet. However, current network solutions are derived from the world of work (and initially the military) and provide poor support for the needs of the home. We present the key findings to emerge from empirical studies of home networks in the UK and US. The studies reveal two key kinds of work that effective home networking relies upon: one, the technical work of setting up and maintaining the home network, and the other, the collaborative and socially organized work of the home which the network is embedded in and supports. The two are thoroughly intertwined and rely upon one another for their realization, yet neither is adequately supported by current networking technologies and applications. Explication of the “work to make the home network work” opens up the design space for the continued integration of the home network in domestic life and elaboration of future support. Key issues for development include the development of networking facilities that do not require advanced networking knowledge, that are flexible and support the local social order of the home and the evolution of its routines, and which ultimately make the home network visible and accountable to household members.