bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study on a Semimicroscopic Formulation of Inelastic Constitutive Equations of Polycrystalline Metals Subjected to a Large Deformation
Authors: Tokuda M. , Yamada K. , Havlicek F.
Published: October 2009

Work-hardening mechanisms of a polycrystalline metal significant in a large deformation range are different from those in a small strain range. That is, a texture development and an effect of grain shape change may be typical and important mechanisms in the large deformation process. In this paper, a set of inelastic constitutive equations incorporating two effects are derived theoretically on the basis of crystal plasticity.
Identification of Materials Parameters for Inelastic Constitutive Models Using Principles of Biologic Evolution
Authors: Mu¨ller D. , Hartmann G.
Published: October 2009

A new method for the identification of materials parameters of an inelastic constitutive model is described. The method is based on the principles of biologic evolution. The efficiency of this approach is demonstrated for Hart’s constitutive model. It is considered that the presented approach is not restricted to any specific model.
Materials Selection in Electromagnetic Launcher Design
Authors: Fahrenthold E. P.
Published: October 2009

The design of electromagnetic launchers includes a large materials selection component, with the use of available structural materials constrained by electrical performance considerations. Feasible material combinations for the composite structure are limited, with mechanical and thermo-electromagnetic simulations required to compare the performance of alternative designs. Numerical modeling studies suggest that next generation devices constructed for laboratory facilities or vehicular mounting may differ markedly in material composition, yet offer similar and significant structural improvements over conventional railgun designs.
A Direct Correlation of Strength With Impact Velocity in the Taylor Test
Authors: Gillis P. P. , Jones S. E.
Published: October 2009

This paper presents a method for analyzing the results of a Taylor impact test. From post-mortem measurements of final specimen length and final undeformed specimen length the dynamic material strength on impact, σo, is correlated with impact velocity, V, through the relation σo=−Y−BV2 where Y and B are presumed to be material constants. This relation provides a rate-dependent constitutive law that is potentially useful in situations such as rod penetration, for example.
Manufacturing System Design Considering Stochastic Product Evolution and Task Recurrence
Authors: Ko Jeonghan , Hu S. Jack
Published: October 2009

The conventional approaches to manufacturing system design and line balancing have often focused on a single generation of products, thus leading to new design or rebalancing when new products are introduced or different models are produced in the same line. As the life cycles of product models become shorter and shorter, this new product then new system-design approach is becoming increasingly ineffective due to too frequent production interruption. Therefore, effective solutions to system-design problems should consider the evolution of products over multiple generations and models, and this paper presents such new methods. Mixed-integer programming models are developed for (1) designing manufacturing system configurations that are cost effective for product evolution involving uncertainty and (2) maximizing the recurrences of manufacturing tasks on the same machines throughout product evolution. A decomposition-based solution procedure is also developed to reduce computational complexity. These new methods can provide a stable system-design solution enabling quick product launches with less line change-over for new or different products.
Performance of Al-6063 Primary and Secondary Billets Used in Hot Aluminum Extrusion
Authors: Akhtar S. S. , Arif A. F. M. , Yilbas B. S.
Published: October 2009

The service life of tooling plays an important part in the economics of the extrusion process. A number of causes are considered responsible for initiating damage to the dies before its designated life is reached. Apart from other factors such as die design and manufacturing, heat treatment, working conditions, etc, the performance of the die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die failure, based on microstructural investigation. A secondary (remelt) billet cast in-house at a local extrusion plant is compared with a primary (smelter) billet by applying different material characterization techniques, including optical microscopy, Vickers microhardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). It is observed that a secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, inclusions, and high hardness that can be associated with poor casting and homogenization practice. In view of present results, some suggestions during in-house billet preparation of secondary billets have been formulated for improved die service life.
Deformation Behaviors and Critical Parameters in Microscale Laser Dynamic Forming
Authors: Gao Huang , Ye Chang , Cheng Gary J.
Published: October 2009

Microscale laser dynamic forming (μLDF) is a novel microfabrication technique to introduce complex 3D profiles in thin films. This process utilizes pulse laser to generate plasma to induce shockwave pressure into the thin film, which is placed above a microsized mold. The strain rate in μLDF reaches 106–107 S−1. Under these ultrahigh strain rates in microscale, deformation behaviors of materials are very complicated and almost impossible to be measured in situ experimentally. In this paper, a finite element method model is built to simulate the μLDF process. An improved Johnson–Cook model was used to calculate the flow stress, and the Johnson–Cook failure criterion was employed to simulate failure during μLDF. The simulation results are validated by experiments, in which the deformation of Cu thin foils after μLDF experiments are characterized by scanning electron microscopy and compared with simulation results. With the verified model, the ultrafast μLDF process is generally discussed first. A series of numerical simulations are conducted to investigate the effects of critical parameters on deformation behaviors. These critical parameters include the ratio of the fillet radius to film thickness, the aspect ratio of mold, as well as laser intensities. The relationship of laser pulse energy and the deformation depth is also verified by a series of μLDF experiments.
Form Tolerance Evaluation of Toroidal Surfaces Using Particle Swarm Optimization
Authors: Wang Yong , Li Lin , Ni Jun , Huang Shuhong
Published: October 2009

Toroidal surfaces are used in many machinery parts such as ball bearing races, bull nose and indexable endmills, continuously-variable transmissions, and enveloping worm gears. Torisity, the form tolerance of toroidal surfaces, plays an important role in mechanical design and quality control such as component functionality, assemblability, and interchangeability. Compared with simple forms, such as planes, spheres, cylinders, and cones, toroidal surfaces are more complex and the evaluation of torisity has not been thoroughly performed. This paper proposes a nonlinear approach to evaluate torisity information using particle swarm optimization (PSO). Three sets of PSO parameters are compared based on the least-squares objective function and minimum-zone objective function using toroidal geometry characteristics. The effectiveness and robustness of the PSO approaches are validated by experiments on simulated entire, outer, inner, thrust, and endmill toroidal surfaces, which appear in various machinery components. Compared with previous studies in torisity evaluation, the proposed approach is more efficient in the ability to provide the form tolerance and the surface profile information simultaneously. The proposed approach is also more consistent with the tolerance zone definition of ASME standard Y14.5M on dimensioning and tolerancing.
Development of a Novel Artifact as a Reference for Gear Pitch Measuring Instruments
Authors: Kondo Yohan , Sasajima Kazuyuki , Osawa Sonko , Sato Osamu , Komori Masaharu
Published: October 2009

The pitch accuracy of a gear is graded on the order of 0.1 μm in ISO 1328-1; therefore, it is necessary for gear measuring instruments (GMIs) to be able to measure gears with the required high accuracy. GMIs are evaluated by measuring a calibrated gear or a gearlike artifact. It is, however, difficult to obtain a measurement uncertainty of less than 0.1 μm. The reason for this difficulty is that a gear artifact has a form error and surface roughness, and that the measurement position on the gear face differs slightly from the calibrated position. In view of this situation, we propose a novel multiball artifact (MBA), which is composed of equally spaced pitch balls, a centering ball, and a datum plane. The pitch balls are assumed to act as gear teeth by calibrating the angular pitch between the centers of each pitch ball. The centering ball and the datum plane are used to set a reference axis of the virtual gear. We manufactured an MBA with the pitch balls arranged on a curvic coupling. The angular pitch deviation between the centers of each pitch ball was calibrated using a coordinate measuring machine (CMM) and adopting the multiple-orientation technique. A master gear was also calibrated for comparison. The measurement uncertainty for the cumulative angular pitch deviation was 0.45 arc sec for the MBA and 1.58 arc sec for the master gear. The MBA could be calibrated with small uncertainty compared with the master gear. After the calibration, a virtual gear of the MBA was built using the calibration value. The virtual gear was measured using the gear-measuring software on the CMM. The measurement value was equal within the range of uncertainty of calibration value. It is verified that the superiority of the MBA to the gear artifact is due to the following reasons: (1) The balls can be manufactured with an accuracy of several tens of nanometers. (2) The calibrated result for the MBA is almost independent of a probe-positioning error because the centers of each pitch ball can be measured at multiple points. (3) In setting the reference axis, the gear artifact generally uses a datum cylinder, in contrast, the MBA uses more accurate ball.
A Measure of the Information Loss for Inspection Point Reduction
Authors: Wärmefjord Kristina , Carlson Johan S. , Söderberg Rikard
Published: October 2009

Since the vehicle program in the automotive industry gets more and more extensive, the costs related to inspection increase. Therefore, there are needs for more effective inspection preparation. In many situations, a large number of inspection points are measured, despite the fact that only a small subset of points is needed. A method, based on cluster analysis, for identifying redundant inspection points has earlier been successfully tested on industrial cases. Cluster analysis is used for grouping the variables into clusters, where the points in each cluster are highly correlated. From every cluster only one representing point is selected for inspection. In this paper the method is further developed, and multiple linear regression is used for evaluating how much of the information is lost when discarding an inspection point. The information loss can be quantified using an efficiency measure based on linear multiple regression, where the part of the variation in the discarded variables that can be explained by the remaining variables is calculated. This measure can be illustrated graphically and that helps to decide how many clusters that should be formed, i.e., how many inspection points that can be discarded.
Correlation between Vancomycin MIC Values and Those of Other Agents against Gram-Positive Bacteria among Patients with Bloodstream Infections Caused by Methicillin-Resistant
Staphylococcus aureus
Authors: Patel N. , Lubanski P. , Ferro S. , Bonafede M. , Harrington S. , Evans A. , Stellrecht K. , Lodise T. P.
Published: October 2009

An increase in the distribution of vancomycin MIC values among methicillin (meticillin)-resistant
Staphylococcus aureus
(MRSA) isolates has been noted. It is postulated that the shift in vancomycin MIC values may be associated with a concurrent rise in the MIC values of other anti-MRSA agents. Scant data are available on the correlation between vancomycin MIC values and the MIC values of other anti-MRSA agents. This study examined the correlation between vancomycin MIC values and the MIC values of daptomycin, linezolid, tigecycline, and teicoplanin among 120 patients with bloodstream infections caused by MRSA at a tertiary care hospital between January 2005 and May 2007. For each included patient, the MIC values of the antibiotics under study were determined by the Etest method and were separated into the following two categories: day 1 (index) and post-day 1 (subsequent). For subsequent isolates, the MIC values for each antibiotic from the post-day 1 terminal isolate were used. Among the index isolates, there was a significant correlation (
P
value, <0.01) between the MIC values for vancomycin and daptomycin and between the MIC values for vancomycin and teicoplanin. The MIC values for daptomycin were significantly correlated with linezolid, tigecycline, and teicoplanin MIC values. Among the 48 patients with subsequent isolates, vancomycin MIC values were significantly correlated with MIC values for daptomycin, linezolid, and teicoplanin (ρ value of ≥0.38 for all comparisons). This study documented an association between vancomycin MIC values and the MIC values of other anti-MRSA antibiotics among patients with bloodstream infections caused by MRSA primarily treated with vancomycin.
Amiodarone and Miltefosine Act Synergistically against
Leishmania mexicana
and Can Induce Parasitological Cure in a Murine Model of Cutaneous Leishmaniasis
Authors: Serrano-Martín Xenón , Payares Gilberto , De Lucca Marisel , Martinez Juan Carlos , Mendoza-León Alexis , Benaim Gustavo
Published: October 2009

Leishmaniasis is parasitic disease that is an important problem of public health worldwide. Intramuscularly administered glucantime and pentostam are the most common drugs used for treatment of this disease, but they have significant limitations due to toxicity and increasing resistance. A recent breakthrough has been the introduction of orally administered miltefosine for the treatment of visceral, cutaneous, and mucocutaneous leishmaniasis, but the relative high cost and concerns about teratogenicity have limited the use of this drug. Searching for alternative drugs, we previously demonstrated that the antiarrhythmic drug amiodarone is active against
Leishmania mexicana
promastigotes and intracellular amastigotes, acting via disruption of intracellular Ca
2+
homeostasis (specifically at the mitochondrion and the acidocalcisomes of these parasites) and through inhibition of the parasite's de novo sterol biosynthesis (X. Serrano-Martín, Y. García-Marchan, A. Fernandez, N. Rodriguez, H. Rojas, G. Visbal, and G. Benaim, Antimicrob. Agents Chemother.
53:
1403-1410, 2009). In the present work, we found that miltefosine also disrupts the parasite's intracellular Ca
2+
homeostasis, in this case by inducing a large increase in intracellular Ca
2+
levels, probably through the activation of a plasma membrane Ca
2+
channel. We also investigated the in vitro and in vivo activities of amiodarone and miltefosine, used alone or in combination, on
L. mexicana
. It was found that the drug combination had synergistic effects on the proliferation of intracellular amastigotes growing inside macrophages and led 90% of parasitological cures in a murine model of leishmaniasis, as revealed by a PCR assay using a novel DNA sequence specific for
L. mexicana
.
Polyamine Transport as a Target for Treatment ofPneumocystisPneumonia
Authors: Liao Chung-Ping , Phanstiel Otto , Lasbury Mark E. , Zhang Chen , Shao Shoujin , Durant Pamela J. , Cheng Bi-Hua , Lee Chao-Hung
Published: October 2009

Polyamine levels are greatly increased in alveolar macrophages (AMs) duringPneumocystispneumonia (PCP), leading to increased production of H2O2, which causes AMs to undergo apoptosis. One of the mechanisms by which polyamine levels in AMs are elevated is enhanced uptake of exogenous polyamines. In this study, the possibility of targeting polyamine uptake as a treatment for PCP was examined. Four anthracene- and one benzene-polyamine conjugates that are potential polyamine transport inhibitors, includingN1-anthracen-9-ylmethyl-butane-1,4-diamine;N-(4-aminobutyl)-N-anthracen-9-ylmethylbutane-1,4-diamine;N-[4-(4-aminobutylamino)butyl]-N-anthracen-9-ylmethylbutane-1,4-diamine;N-(4-amino-butyl)-N′-(10-{[4-(4-amino-butylamino)butylamino]-methyl}anthracen-9-ylmethyl)butane-1,4-diamine (44-Ant-44); and benzene-polyamine conjugateN-(4-amino-butyl)-N′-(4-{[4-(4-amino-butylamino)butylamino]-methyl}benzyl)butane-1,4-diamine (44-Bn-44), were tested. Compounds 44-Ant-44 and 44-Bn-44 were found to have a very low toxicity to AMs in vitro and were evaluated for their therapeutic effect on PCP in vivo. Sprague-Dawley rats infected withP. cariniifor 28 days were intranasally instilled with 50 μl of a 1 mM solution of 44-Bn-44 or 44-Ant-44 every 2 days. Twenty-one days after initiation of the treatment, three to five rats from each group were sacrificed and examined for lung pathology, organism burden, and apoptosis of AMs. Both 44-Bn-44 and 44-Ant-44 reduced organism burdens; however, only 44-Ant-44 decreased the severity of the infection with reduced lung inflammation, increased clearance of exudates, increased air space, and decreased apoptosis of AMs. 44-Ant-44 also significantly prolonged the survival of treated animals. These results suggest that polyamine uptake is a potential target for treatment of PCP.
Novel Antiseptic Urinary Catheters for Prevention of Urinary Tract Infections: Correlation of In Vivo and In Vitro Test Results
Authors: Hachem Ray , Reitzel Ruth , Borne Agatha , Jiang Ying , Tinkey Peggy , Uthamanthil Rajesh , Chandra Jyotsna , Ghannoum Mahmoud , Raad Issam
Published: October 2009

Urinary catheters are widely used for hospitalized patients and are often associated with high rates of urinary tract infection. We evaluated in vitro the antiadherence activity of a novel antiseptic Gendine-coated urinary catheter against several multidrug-resistant bacteria. Gendine-coated urinary catheters were compared to silver hydrogel-coated Foley catheters and uncoated catheters. Bacterial biofilm formation was assessed by quantitative culture and scanning electron microscopy. These data were further correlated to an in vivo rabbit model. We challenged 31 rabbits daily for 4 days by inoculating the urethral meatus with 1.0 × 10
9
CFU streptomycin-resistant
Escherichia coli
per day. In vitro, Gendine-coated urinary catheters reduced the CFU of all organisms tested for biofilm adherence compared with uncoated and silver hydrogel-coated catheters (
P
< 0.004). Scanning electron microscopy analysis showed that a thick biofilm overlaid the control catheter and the silver hydrogel-coated catheters but not the Gendine-coated urinary catheter. Similar results were found with the rabbit model. Bacteriuria was present in 60% of rabbits with uncoated catheters and 71% of those with silver hydrogel-coated catheters (
P
< 0.01) but not in those with Gendine-coated urinary catheters. No rabbits with Gendine-coated urinary catheters had invasive bladder infections. Histopathologic assessment revealed no differences in toxicity or staining. Gendine-coated urinary catheters were more efficacious in preventing catheter-associated colonization and urinary tract infections than were silver hydrogel-coated Foley catheters and uncoated catheters.
Prevalence and Clonal Characterization of
Streptococcus pyogenes
Clinical Isolates with Reduced Fluoroquinolone Susceptibility in Spain
Authors: Montes Milagrosa , Tamayo Esther , Orden Beatriz , Larruskain Julián , Perez-Trallero Emilio
Published: October 2009

The aim of this study was to determine the prevalence and characteristics of non-fluoroquinolone (FQ)-susceptible
Streptococcus pyogenes
isolates and to study their mechanisms of resistance. We performed a prospective prevalence study with 468 isolates collected from 2005 to 2007 and a retrospective study that was based on the examination of existing data collected from 1999 to 2008. The retrospective study included data for isolates with high-level resistance (HR) to ciprofloxacin (MIC ≥ 32 μg/ml) (HR isolates) and isolates with the same
emm
types as those reported in the literature with low-level resistance (LR) to ciprofloxacin (MICs, 2 to 8 μg/ml) (LR isolates,
n
= 205). Genetic characterization of the isolates was performed by means of
emm
typing and multilocus sequence typing. The prevalence of LR ranged from 1.9% in 2005 to 30.8% in 2007. This increase was mainly due to the circulation of an
emm
6 subtype (
emm
6.4) that represented 77.1% of the LR isolates in 2007. Notably, another
emm
6 subtype, also detected in 2007 (
emm
6.37), showed coresistance to 14- and 15-membered macrolides mediated by the
mefA
gene. Only three HR isolates were detected (isolates
emm
68.1/ST247/T3,13,B3264,
emm
77/ST399/T28, and
emm
28/ST52/T28), and all were identified in the retrospective study. Overall, the 673 isolates represented 25
emm
types. All LR isolates were clustered into two
emm
types:
emm
6 (six
emm
6 subtypes) and
emm
75. All the 156
emm
6 isolates had LR, harbored the Ser79/Ala mutation in the
parC
gene product, and had the same sequence type (ST), ST382. Most (21/33) of the
emm
75 isolates had LR, showed the Ser79/Phe plus Asp91/Asn double mutation in the
parC
gene product, and were ST150. The Asp91/Asn mutation by itself did not confer resistance to FQs.
Long-Lasting Enfuvirtide Carrier Pentasaccharide Conjugates with Potent Anti-Human Immunodeficiency Virus Type 1 Activity
Authors: Huet Thierry , Kerbarh Olivier , Schols Dominique , Clayette Pascal , Gauchet Cécile , Dubreucq Guy , Vincent Loïc , Bompais Heidi , Mazinghien Romain , Querolle Olivier , Salvador Arnaud , Lemoine Jérôme , Lucidi Bruno , Balzarini Jan , Petitou Maurice
Published: October 2009

Enfuvirtide (also known as Fuzeon, T-20, or DP-178) is an antiretroviral fusion inhibitor which prevents human immunodeficiency virus type 1 (HIV-1) from entering host cells. This linear 36-mer synthetic peptide is indicated, in combination with other antiretroviral agents, for the treatment of HIV-1-infected individuals and AIDS patients with multidrug-resistant HIV infections. Although enfuvirtide is an efficient anti-HIV-1 drug, its clinical use is limited by a short plasma half-life, i.e., approximately 2 h, which requires twice-daily subcutaneous injections, often resulting in skin sensitivity reaction side effects at the injection sites. Ultimately, 80% of patients stop enfuvirtide treatment within 6 months because of these side effects. We report on the development of long-lasting enfuvirtide conjugates by the use of the site-specific conjugation of enfuvirtide to an antithrombin-binding carrier pentasaccharide (CP) through polyethylene glycol (PEG) linkers of various lengths. These conjugates showed consistent and broad anti-HIV-1 activity in the nanomolar range. The coupling of the CP to enfuvirtide only moderately affected the in vitro anti-HIV-1 activity in the presence of antithrombin. Most importantly, one of these conjugates, enfuvirtide-PEG12-CP (EP40111), exhibited a prolonged elimination half-life of more than 10 h in rat plasma compared to the half-life of native enfuvirtide, which was 2.8 h. On the basis of the pharmacokinetic properties of antithrombin-binding pentasaccharides, the anticipated half-life of EP40111 in humans would putatively be about 120 h, which would allow subcutaneous injection once a week instead of twice daily. In conclusion, EP40111 is a promising compound with strong potency as a novel long-lasting anti-HIV-1 drug.
Metronidazole Resistance in
Prevotella
spp. and Description of a New
nim
Gene in
Prevotella baroniae
Authors: Alauzet C. , Mory F. , Teyssier C. , Hallage H. , Carlier J. P. , Grollier G. , Lozniewski A.
Published: October 2009

Nonduplicate clinical isolates of
Prevotella
spp. recovered from patients hospitalized between 2003 and 2006 in two French tertiary-care teaching hospitals were investigated for their susceptibility to metronidazole and the presence of
nim
genes. Of the 188 strains tested, 3 isolates displayed reduced susceptibility to metronidazole after 48 h of incubation, while 27 additional isolates exhibited heterogeneous resistance after prolonged incubation; all 30 of the isolates were
nim
negative. Among the remaining 158 isolates, 7
nim
-positive isolates were detected. All of these strains were identified as
Prevotella baroniae
by 16S rRNA gene sequence analysis and contained a new
nim
gene, named
nimI
, as determined by DNA sequence analysis. Chromosomal localization of this single-copy gene was demonstrated in all clinical isolates as well as in type strain
P. baroniae
DSM 16972 by using Southern hybridization. No known associated insertion sequence elements were detected upstream of the
nimI
gene in any of the
nim
-positive strains by PCR mapping. After prolonged exposure to metronidazole, stable resistant subpopulations could be selected in
nimI
-positive
Prevotella
isolates (
n
= 6) as well as in
nim-
negative
Prevotella
isolates (
n
= 6), irrespective of their initial susceptibility to this antibiotic. This study is the first description of a new nitroimidazole resistance gene in
P. baroniae
which seems to be silent and which might be intrinsic in this species. Moreover, our findings highlight the fact that high-level resistance to metronidazole may be easily induced in both
nim
-positive and
nim
-negative
Prevotella
sp. strains.
Novel Approach for Comparing the Abilities of Quinolones To Restrict the Emergence of Resistant Mutants during Quinolone Exposure
Authors: Malik Muhammad , Hoatam Gerard , Chavda Kalyan , Kerns Robert J. , Drlica Karl
Published: October 2009

An agar-plate assay was adapted to examine aspects of quinolone structure that restrict the emergence of quinolone-mediated quinolone resistance. When
Escherichia coli
was applied to agar containing nalidixic acid, the number of quinolone-resistant mutants arising during incubation was decreased by raising the drug concentration and by mutations expected to block the induction of the SOS response (
recA
,
lexA
); the mutant number was increased by a mutator mutation (
ung
). The examination of four related fluoroquinolones then revealed that a C-8 methoxy group and an
N
-ethyl piperazine substituent at C-7 reduced mutant acquisition more effectively than C-8 H and C-7
C
-ethyl piperazine groups. The fluoroquinolone that was most effective at restricting mutant acquisition was the most active when lethal activity was measured on agar plates or in liquid medium (as minimal bactericidal concentration). It also exhibited the lowest ratio of mutant MIC to wild-type MIC when it was tested with a set of isogenic gyrase mutants, and it had a low mutant prevention concentration (MPC) relative to MIC. However, a low MPC was less likely to be important in restricting the induced mutant accumulation because a fluoroquinolone
N
-ethyl piperazine substituent was more effective than a
C
-ethyl piperazine substituent at reducing mutant accumulation but was less effective at lowering the MPC. An 8-methoxy-quinazoline-2,4-dione was also effective at restricting the accumulation of resistant mutants on agar. Collectively, these data characterize a simple assay for detection of drug-mediated resistance that is sensitive to the structures of GyrA inhibitors. The assay provides a new method for screening quinolones and quinolone-like molecules that complements MPC-based tests for restricting the emergence of resistance.
Inhibition of Erythrocyte Invasion andPlasmodium falciparumMerozoite Surface Protein 1 Processing by Human Immunoglobulin G1 (IgG1) and IgG3 Antibodies
Authors: Lazarou Maria , Patiño José A. Guevara , Jennings Richard M. , McIntosh Richard S. , Shi Jianguo , Howell Steven , Cullen Eilish , Jones Tarran , Adame-Gallegos Jaime R. , Chappel Jonathan A. , McBride Jana S. , Blackman Michael J. , Holder Anthony A. , Pleass Richard J.
Published: October 2009

Antigen-specific antibodies (Abs) to the 19-kDa carboxy-terminal region ofPlasmodium falciparummerozoite surface protein 1 (MSP119) play an important role in protective immunity to malaria. Mouse monoclonal Abs (MAbs) 12.10 and 12.8 recognizing MSP119can inhibit red cell invasion by interfering with MSP1 processing on the merozoite surface. We show here that this ability is dependent on the intact Ab since Fab and F(ab′)2fragments derived from MAb 12.10, although capable of binding MSP1 with high affinity and competing with the intact antibody for binding to MSP1, were unable to inhibit erythrocyte invasion or MSP1 processing. The DNA sequences of the variable (V) regions of both MAbs 12.8 and 12.10 were obtained, and partial amino acid sequences of the same regions were confirmed by mass spectrometry. Human chimeric Abs constructed by using these sequences, which combine the original mouse V regions with human γ1 and γ3 constant regions, retain the ability to bind to both parasites and recombinant MSP119, and both chimeric human immunoglobulin G1s (IgG1s) were at least as good at inhibiting erythrocyte invasion as the parental murine MAbs 12.8 and 12.10. Furthermore, the human chimeric Abs of the IgG1 class (but not the corresponding human IgG3), induced significant NADPH-mediated oxidative bursts and degranulation from human neutrophils. These chimeric human Abs will enable investigators to examine the role of human Fcγ receptors in immunity to malaria using a transgenic parasite and mouse model and may prove useful in humans for neutralizing parasites as an adjunct to antimalarial drug therapy.
The Secreted Esterase of Group AStreptococcusIs Important for Invasive Skin Infection and Dissemination in Mice
Authors: Zhu Hui , Liu Mengyao , Sumby Paul , Lei Benfang
Published: October 2009

Virulence factors regulated by the CovRS/CsrRS two-component gene regulatory system contribute to the invasive diseases caused by group AStreptococcus(GAS). To determine whether thestreptococcalsecretedesterase (Sse), an antigen that protects against subcutaneous GAS infection, is one of these virulence factors, we investigated the phenotype of a nonpolarssedeletion mutant strain (Δsse). In addition, we examined the effects ofcovSmutation onsseexpression. As assessed using a mouse model of subcutaneous infection, the virulence of the Δssestrain is attenuated and the overall pathology is reduced. Furthermore, GAS was detected in the blood and spleens from mice subcutaneously infected with the parental strain, whereas mice subcutaneously infected with the Δssestrain had no GAS present in their blood and spleens. The ability of the mutant to survive in the subcutis of mice appeared to be compromised. The growth of the Δssestrain in rich and chemically defined media and nonimmune human blood and sera was slower than that of the wild-type strain. Complementation restored the phenotype of the Δssestrain to that of the wild-type strain. The wild-type, Δsse, and complement strains had no detectable SpeB activity. Expression of Sse is negatively controlled by CovRS. These findings suggest that Sse is a CovRS-regulated virulence factor that is important for the virulence of GAS in subcutaneous infection and plays an important role in severe soft tissue infections and systemic dissemination of GAS from the skin.
Saliva Enables the Antimicrobial Activity of LL-37 in the Presence of Proteases of
Porphyromonas gingivalis
Authors: Gutner Michal , Chaushu Stella , Balter Daniela , Bachrach Gilad
Published: October 2009

Proteolysis is a common microbial virulence mechanism that enables the destruction of host tissue and evasion from host defense mechanisms. Antimicrobial peptides, also known as host defense peptides, are effector molecules of the innate immunity that demonstrate a broad range of antimicrobial and immunoregulatory activities. Deficiency of the human LL-37 antimicrobial peptide was previously correlated with severe periodontal disease.
Porphyromonas gingivalis
, the major pathogen associated with periodontitis, is highly proteolytic. In this study,
P. gingivalis
was found capable of degrading LL-37 by utilizing its arginine-specific gingipains. Saliva collected from volunteers with a healthy periodontium protected LL-37 from proteolysis by
P. gingivalis.
Salivary protection of LL-37 was heat resistant and specific and enabled LL-37 to inhibit growth of
Escherichia coli
in the presence of the
P. gingivalis
proteases. Previously, saliva and other body fluids have been shown to inhibit the antimicrobial activity of LL-37. Here we demonstrate that at a cost of a small reduction in the bactericidal activity of LL-37, saliva enables the antibacterial activity of LL-37 despite the presence of proteases secreted by the main periodontopathogen.
Molecular Characterization of EmABP, an Apolipoprotein A-I Binding Protein Secreted by the
Echinococcus multilocularis
Metacestode
Authors: Bernthaler Peter , Epping Kerstin , Schmitz Gerd , Deplazes Peter , Brehm Klaus
Published: October 2009

Cestodes are unable to synthesize de novo most of their own membrane lipids, including cholesterol, and have to take them up from the host during an infection. The underlying molecular mechanisms are so far unknown. Here we report the identification and characterization of a novel gene, Em
abp
, which is expressed by larval stages and adults of the fox tapeworm
Echinococcus multilocularis
. The encoded protein, EmABP, displays significant homologies to apolipoprotein A-I binding protein (AI-BP) of mammalian origin and to metazoan YjeF_N domain proteins. Like mammalian AI-BP, EmABP carries an export-directing signal sequence which is absent in predicted AI-BP orthologs from the related flatworms
Schistosoma japonicum
and
Schmidtea mediterranea
. Using a specific antibody and immunoprecipitation techniques, we demonstrate that EmABP is secreted into the extraparasitic environment and into the hydatid fluid of in vitro-cultivated metacestode vesicles. Furthermore, we show that apolipoprotein A-I (apoA-I), a major constituent of cholesterol-transporting high-density lipoproteins, is present in hydatid fluid. By pulldown experiments, we demonstrate that recombinantly expressed, purified EmABP interacts with purified human apoA-I and is able to precipitate apoA-I from human serum. On the basis of these features and the suggested function of AI-BP in cholesterol transport in higher eukaryotes, we propose a role for EmABP in cholesterol and lipid uptake mechanisms of larval
E. multilocularis
.
The Long-Lived Nature of
Clostridium perfringens
Iota Toxin in Mammalian Cells Induces Delayed Apoptosis
Authors: Hilger Hanna , Pust Sascha , von Figura Guido , Kaiser Eva , Stiles Bradley G. , Popoff Michel R. , Barth Holger
Published: October 2009

Mono-ADP ribosylation of actin by bacterial toxins, such as
Clostridium perfringens
iota or
Clostridium botulinum
C2 toxins, results in rapid depolymerization of actin filaments and cell rounding. Here we report that treatment of African green monkey kidney (Vero) cells with iota toxin resulted in delayed caspase-dependent death. Unmodified actin did not reappear in toxin-treated cells, and enzyme-active toxin was detectable in the cytosol for at least 24 h. C2 toxin showed comparable, long-lived effects in cells, while a C2 toxin control lacking ADP-ribosyltransferase activity did not induce cell death. To address whether the remarkable stability of the iota and C2 toxins in cytosol was crucial for inducing cell death, we treated cells with C/SpvB, the catalytic domain of
Salmonella enterica
SpvB. Although C/SpvB also mono-ADP ribosylates actin as do the iota and C2 toxins, cells treated with a cell-permeating C/SpvB fusion toxin became rounded but recovered and remained viable. Moreover, unmodified actin reappeared in these cells, and ADP-ribosyltransferase activity due to C/SpvB was not detectable in the cytosol after 24 h, a result most likely due to degradation of C/SpvB. Repeated application of C/SpvB prevented recovery of cells and reappearance of unmodified actin. In conclusion, a complete but transient ADP ribosylation of actin was not sufficient to trigger apoptosis, implying that long-term stability of actin-ADP-ribosylating toxins, such as iota and C2, in the cytosol is crucial for inducing delayed, caspase-dependent cell death.
Persistent Infection Contributes to Heterologous Protective Immunity against Fatal Ehrlichiosis
Authors: Thirumalapura Nagaraja R. , Crossley Emily C. , Walker David H. , Ismail Nahed
Published: October 2009

Human monocytotropic ehrlichiosis (HME), an emerging and often life-threatening tick-transmitted disease, is caused by the obligately intracellular bacterium
Ehrlichia chaffeensis
. HME is modeled in C57BL/6 mice using
Ehrlichia muris
, which causes persistent infection, and
Ixodes ovatus Ehrlichia
(IOE), which is either acutely lethal or sublethal depending on the dose and route of inoculation. A persistent primary
E. muris
infection, but not a sublethal IOE infection, protects mice against an ordinarily lethal secondary IOE challenge. In the present study, we determined the role of persistent infection in maintenance of protective memory immune responses.
E. muris-
infected mice were treated with doxycycline or left untreated and then challenged with an ordinarily lethal dose of IOE. Compared to
E. muris
-primed mice treated with doxycycline, untreated mice persistently infected with
E. muris
had significantly greater numbers of antigen-specific gamma interferon-producing splenic memory T cells, significant expansion of CD4
+
CD25
+
T regulatory cells, and production of transforming growth factor β1 in the spleen. Importantly,
E. muris
-primed mice treated with doxycycline showed significantly greater susceptibility to challenge infection with IOE compared to untreated mice persistently infected with
E. muris
. The study indicated that persistent ehrlichial infection contributes to heterologous protection by stimulating the maintenance of memory T-cell responses.
C3H Male Mice with Severe Combined Immunodeficiency Cannot Clear a Urethral Infection with a Human Serovar of
Chlamydia trachomatis
Authors: Pal Sukumar , Sarcon Annahita K. , de la Maza Luis M.
Published: October 2009

The pathogenesis of an infection of the male genitourinary tract of mice with a human serovar of
Chlamydia trachomatis
has not been characterized. To establish a new model, we inoculated C3H/HeN (
H-2

k

) mice in the meatus urethra with
C. trachomatis
serovar D. To determine the 50% infectious dose (ID
50
), male mice were inoculated with doses ranging from 10
2
to 10
6
inclusion-forming units (IFU). The mice were euthanized 10 days post infection (p.i.), and the urethra, bladder, epididimydes, and testes were cultured for
Chlamydia
. Positive cultures were obtained from the urethra, urinary bladder, and epididimydes, and the ID
50
was determined to be 5 × 10
4
IFU/mouse. Subsequently, to characterize the course of the infection, wild-type (WT) and C3H animals with severe combined immunodeficiency (SCID animals) were inoculated with 10
6
IFU/mouse (20 times the ID
50
). In the WT mice, the infection peaked in the second week, and by 42 days p.i., it was cleared. In contrast, most of the SCID mice continued to have positive cultures at 60 days p.i.
C. trachomatis
-specific antibodies were first detected in WT animals' sera at 21 days p.i. and increased until 42 days p.i. The immunoglobulin G2a (IgG2a) titers were 32-fold higher than those of IgG1, indicative of a Th1-biased immune response. A lymphoproliferative assay using splenocytes showed a significant cell-mediated immune response in the WT mice. As expected, no humoral or cell-mediated immune responses were observed in the SCID animals. In conclusion, inoculation of WT male mice in the meatus urethra with a human serovar of
C. trachomatis
resulted in a limited infection mainly localized to the lower genitourinary tract. On the other hand, SCID animals could not clear the infection, suggesting that in male mice, the adaptive immune response is necessary to control an infection with a
C. trachomatis
human serovar.
Spa15 ofShigella flexneriIs Secreted through the Type III Secretion System and Prevents Staurosporine-Induced Apoptosis
Authors: Faherty Christina S. , Maurelli Anthony T.
Published: October 2009

Shigella flexneriis a gram-negative, facultative intracellular pathogen that invades the colonic epithelium and causes bacillary dysentery. We previously demonstrated thatS. flexneriinhibits staurosporine-induced apoptosis in infected epithelial cells and that a ΔmxiEmutant is unable to inhibit apoptosis. Therefore, we hypothesized that an MxiE-regulated gene was responsible for protection of epithelial cells from apoptosis. Analysis of all MxiE-regulated genes yielded no mutants that lacked the ability to prevent apoptosis. Spa15, which is defined as a type III secretion system chaperone, was analyzed since it associates with MxiE. A Δspa15mutant was unable to prevent staurosporine-induced apoptosis. C-terminal hemagglutinin-taggedspa15was secreted byS. flexneriwithin 2 h in the Congo red secretion assay, and secretion was dependent on the type III secretion system. Spa15 was also secreted byShigellain infected epithelial cells, as verified by immunofluorescence analysis. Spa15 secretion was decreased in the ΔmxiEmutant, which demonstrates why this mutant is unable to prevent staurosporine-induced apoptosis. Our data are the first to show that Spa15 is secreted in a type III secretion system-dependent fashion, and the absence of Spa15 in the Δspa15mutant results in the loss of protection from staurosporine-induced apoptosis in epithelial cells. Thus, Spa15 contributes to the intracellular survival ofShigellaby blocking apoptosis in the infected host cell.
CD23 Mediates Antimycobacterial Activity of Human Macrophages
Authors: Mossalayi M. Djavad , Vouldoukis Ioannis , Mamani-Matsuda Maria , Kauss Tina , Guillon Jean , Maugein Jeanne , Moynet Daniel , Rambert Jérôme , Desplat Vanessa , Mazier Dominique , Vincendeau Philippe , Malvy Denis
Published: October 2009

Engagement of surface receptors contributes to the antimicrobial activity of human immune cells. We show here that infection of human monocyte-derived macrophages (MDM) with liveMycobacterium aviuminduced the expression of CD23 on their membrane. Subsequent cross-linking of surface CD23 by appropriate ligands induced a dose-dependent antibacterial activity of MDM and the elimination of most infected cells. The stimulation of inducible nitric oxide synthase-dependent generation of NO from MDM after CD23 activation played a major role during their anti-M. aviumactivity. CD23 activation also induced tumor necrosis factor alpha (TNF-α) production from MDM. Mycobacteria reduction was partially inhibited by the addition of neutralizing anti-TNF-α antibody to cell cultures without affecting NO levels, which suggested the role of this cytokine for optimal antimicrobial activity. Finally, interleukin-10, a Th2 cytokine known to downregulate CD23 pathway, is shown to decrease NO generation and mycobacteria elimination by macrophages. Therefore, (i) infection withM. aviumpromotes functional surface CD23 expression on human macrophages and (ii) subsequent signaling of this molecule contributes to the antimicrobial activity of these cells through an NO- and TNF-α-dependent pathway. This study reveals a new human immune response mechanism to counter mycobacterial infection involving CD23 and its related ligands.
Retrograde crossing stent placement strategies at the basilar apex for the treatment of wide necked aneurysms: reconstructive and deconstructive opportunities
Authors: Pride G L , Welch B , Novakovic R , Rickert K , White J , Dutton-Johnson K , Samson D , Purdy P
Published: October 2009

Neck remodeling devices such as the Neuroform or Enterprise greatly facilitate the endovascular treatment of wide necked basilar apex aneurysms. The complex anatomy of the basilar apex affords opportunity for antegrade, multiple crossing and retrograde device placement strategies to facilitate coil embolization. A retrograde approach is possible in the presence of a posterior communicating artery large enough to allow device navigation. Our experience with a retrograde device placement strategy in three patients is reported. In two patients, device positioning extended from one P1 segment of the posterior cerebral artery to the other across the basilar apex. In one patient, device positioning extended from the P1 segment of the posterior cerebral artery across the basilar apex into the opposite superior cerebellar artery. All patients underwent reconstructive or deconstructive uncomplicated coil embolization after device placement with stable aneurysm occlusion on follow-up angiography. In appropriate anatomic situations, retrograde stent placement across the basilar apex through a posterior communicating artery may represent a preferred strategy for wide necked basilar apex aneurysms.
Thirty day results of 227 consecutive carotid stent procedures performed in carotid stenting clinical trials
Authors: Heck D
Published: October 2009

Background and purpose

As evidence accumulates that carotid artery stenting (CAS) is a durable and effective procedure for stroke prevention, the utility of the procedure hinges on the perioperative risk. The perioperative risk of CAS procedures has historically been higher than carotid endarterectomy in most clinical trials. The perioperative risk of the series presented here is lower than any previously reported in the context of a clinical trial.

Methods

Data were collected prospectively from 227 consecutive elective CAS procedures by a single neurointerventionalist performed as part of carotid stenting clinical trials as per the trial protocols, which included randomized trials of “average risk” patients and non-randomized trials of “high risk” patients. The primary outcome measures were 30 day stroke and death, and in most cases 30 day myocardial infarction (MI) also.

Results

Follow-up was 100%. There were no deaths. There was one technical failure. The overall 30 day stroke/death/MI rate was 5/226 (2.2%). There was one MI. The 30 day stroke and death rate for symptomatic patients was 2.5% and for asymptomatic patients 1.4%. Two of the four strokes occurred in vascular territories separate from the target carotid artery.

Conclusions

The perioperative CAS complications in this series were well below the 6% for symptomatic patients and 3% for asymptomatic patients currently recommended based on historic carotid endarterectomy data. Carotid stenting can be performed safely in the community, provided there are experienced interventionalists and proper patient selection.
THEORETICAL STUDIES ON THE EXTRINSIC DEFECTS OF MONTMORILLONITE IN SOFT ROCK
Authors: HE MAN-CHAO , FANG ZHI-JIE , ZHANG PING
Published: October 2009

Using the first-principles methods, we study the formation energetics and charge doping properties of the extrinsic substitutional defects in montmorillonite. Especially, we choose Be , Mg , Ca , Fe , Cr , Mn , Cu , Zn as extrinsic defects to substitute for Al atoms. By systematically calculating the impurity formation energies and transition energy levels, we find that all Group II defects introduce the relative shallow transition energy levels in montmorillonite. Among them, Mg Al has the shallowest transition energy level at 0.10 eV above the valence band maximum. The transition-elemental defects Fe Al , Cr Al , and Mn Al are found to have relatively low formation energies, suggesting their easy formation in montmorillonite under natural surrounding conditions. Our calculations show that the defects Cu Al and Zn Al have high formation energies, which exclude the possibility of their formation in montmorillonite.