bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Performance, Mobility, and Agility of Multilegged Robots
Authors: Bowling Alan P.
Published: November 2006

Background. This article presents a method for describing the dynamic performance of multilegged robots. It involves examining how well the legged system uses ground contact to produce acceleration of its body; these abilities are referred to as its force and acceleration capabilities. These capabilities are bounded by actuator torque limits and the no-slip condition. Method of Approach. The approach followed here is based on the dynamic capability equations, which are extended to consider frictional ground contact as well as the changes in degrees-of-freedom that occurs as the robot goes into and out of contact with the ground. Results. The analysis describes the maximum translational and rotational accelerations of the main-body that are guaranteed to be achievable in every direction without causing slipping at the contact points or saturating an actuator. Conclusion. This analysis provides a description of the mobility and agility of legged robots. The method is illustrated using a hexapod as an example.
Fitting of Reference Surfaces for Engineering Surfaces by Nonlinear Least-Squares Technique
Authors: Kumar Jagadeesha , Shunmugam M. S.
Published: November 2006

Engineering surfaces comprise form and waviness errors, which are separated from the measured surface by establishing a reference surface that represents these errors. An attempt is made for the first time to fit a reference surface for simultaneous separation of form and waviness errors. A second-degree polynomial and a set of sinusoidal functions are taken as basis functions to represent form and waviness, respectively, and fitting is done using a nonlinear least-squares method. Different examples of surfaces are considered and a comparison is also made with 3D Gaussian filter to bring out the nature of reference surfaces obtained by the present fitting approach.
A Comprehensive Tool for Recovering 3D Models From 2D Photos With Wide Baselines
Authors: Lu Yuzhu , Smith Shana
Published: November 2006

Recovering 3D objects from 2D photos is an important application in the areas of computer vision, computer intelligence, feature recognition, and virtual reality. This paper describes an innovative and systematic method that integrates automatic feature extraction, automatic feature matching, manual revision, feature recovery, and model reconstruction into an effective and integrated 3D object recovery tool. The proposed method is a convenient and inexpensive way to recover 3D scenes and models directly from 2D photos. New automatic key-point selection and hierarchical matching algorithms were developed for matching 2D photos with wide baselines. The method uses a universal camera intrinsic matrix estimation technique to eliminate the need for camera calibration experiments. A new automatic texture-mapping algorithm was also developed for finding the best textures in 2D photos. The paper includes some examples and results to show the capabilities of the new method.
Velocity and Acceleration Cones for Kinematic and Dynamic Constraints on Omni-Directional Mobile Robots
Authors: Wu Jianhua , Williams Robert L. , Lew Jae
Published: November 2006

We consider the problems of kinematic and dynamic constraints, with actuator saturation and wheel slippage avoidance, for motion planning of a holonomic three-wheeled omni-directional robot. That is, the motion planner must not demand more velocity and acceleration at each time instant than the robot can provide. A new coupled non-linear dynamics model is derived. The novel concepts of Velocity and Acceleration Cones are proposed for determining the kinematic and dynamic constraints. The Velocity Cone is based on kinematics; we propose two Acceleration Cones, one for avoiding actuator saturation and the other for avoiding wheel slippage. The wheel slippage Acceleration Cone was found to dominate. In practical motion, all commanded velocities and accelerations from the motion planner must lie within these cones for successful motion. Case studies, simulations, and experimental validations are presented for our dynamic model and controller, plus the Velocity and Acceleration Cones.
Human Operator Performance Testing Using an Input-Shaped Bridge Crane
Authors: Khalid Attir , Huey John , Singhose William , Lawrence Jason , Frakes David
Published: November 2006

The payload oscillation inherent to all cranes makes it challenging for human operators to manipulate payloads quickly, accurately, and safely. An input-shaping controller was implemented on a large bridge crane at the Georgia Institute of Technology to reduce crane payload oscillation. The crane was used to study the performance of human operators as they drove the crane through obstacle courses. An image processing system was implemented to track the movement of the crane payload. Data from these experiments show that operators performed manipulation tasks faster, safer, and more effectively when input shaping was utilized to reduce payload sway.
A Multivariable and Multi-Objective Approach for the Control of Hot-Strip Mills
Authors: Cuzzola Francesco A.
Published: November 2006

The control of a hot strip rolling mill is quite a complex problem due to the presence of many simultaneous control tasks. This is the main motivation that spurred the major steel corporations to adopt more sophisticated control techniques based on multi-variable concepts. The main drawback of most multi-variable approaches is the lack of transparency of the resulting controller that, consequently, can turn out hard to tune on site. In this paper we solve the tuning problem by adopting a multi-objective control approach that allows explicitly taking into account the existence of actuator limitations and nonlinear dynamics. Furthermore, the application of the proposed control technique to a narrow hot strip mill is here described.
System-Level Model and Stochastic Optimal Control for a PEM Fuel Cell Hybrid Vehicle
Authors: Lin Chan-Chiao , Kim Min-Joong , Peng Huei , Grizzle Jessy W.
Published: November 2006

System-level modeling and control strategy development for a fuel cell hybrid vehicle (FCHV) are presented in this paper. A reduced-order fuel cell model is created to accurately predict the fuel cell system efficiency while retaining dynamic effects of important variables. The fuel cell system model is then integrated with a DC/DC converter, a Li-ion battery, an electric drive, and tire/vehicle dynamics to form an FCHV. In order to optimize the power management strategy of the FCHV, we develop a stochastic design approach based on the Markov chain modeling and stochastic dynamic programming (SDP). The driver demand is modeled as a Markov process to represent the future uncertainty under diverse driving conditions. The infinite-horizon SDP solution generates a stationary state-feedback control policy to achieve optimal power management between the fuel cell system and battery. Simulation results over different driving cycles are presented to demonstrate the effectiveness of the proposed stochastic approach.
Measurement and Modeling of Dynamic Rolling Friction in Linear Microball Bearings
Authors: Tan Xiaobo , Modafe Alireza , Ghodssi Reza
Published: November 2006

In prior work of the authors and co-workers, a vision-based system was developed for characterizing the tribological behavior of silicon-micromachined linear microball bearings. Plain difference methods introduce amplitude and/or phase distortion in computing the derivative signals (e.g., velocity and acceleration) based on the position snapshots. In this paper frequency-dependent amplitude and phase compensation algorithms are developed for both the forward difference and the central difference methods to retrieve without distortion the friction and the relative velocity between bearing elements. Processing of experimental data with these techniques reveals nonlinear, viscous frictional behavior in the bearing. A viscoelastic model based on a continuum of mass-spring-damper elements is then proposed for the ball-groove interaction. Numerical results show that this model captures the nonlinear velocity dependence of the rolling friction observed in experiments.
Measurement of Driver Steering Torque Using Electromyography
Authors: Pick Andrew J. , Cole David J.
Published: November 2006

This paper is concerned with developing a method to measure a driver’s muscle activation strategy during driving, to enable validation of a mathematical model. Electromyography (EMG) was successfully used to measure driver muscle activity. Regression analysis of the EMG data, measured from the right arm of one test subject, was used to determine the key muscles involved in generating steering torque. The significant muscles were found to be the mid and front deltoid, the sternal portion of the pectoralis major, and the triceps long head. Using the identified regression parameters and measured EMG from key muscles, forces generated by the driver at the rim of the steering wheel were predicted under isometric conditions. The method was further developed and measurements were taken from the left and right arms of eight test subjects. Using regression analysis a model that predicts steering torque from the EMG signals was generated. The method also allows co-contraction of opposing muscles to be identified during a dynamic steering maneuver. Muscle co-contraction is thought to be a significant control strategy employed by drivers, and is the subject of further work.
Evaluation of Nonlinear Dynamics Using Optimal Motion Planning
Authors: Herman Przemysław
Published: November 2006

The precise control of a manipulator depends on its velocity as well as on its configuration and dynamic properties. This paper presents some observations that can serve as a useful tool for identifying nonlinear ear effects in a manipulator. The tool is based on equations of motion being expressed in terms of inertial quasi-velocities (IQVs). They are rates containing both kinematic and mechanical parameters of the system. The presented approach gives a further insight into the manipulator motion. An analytical example shows the proposed strategy.
Interaction Between Secondaries in a Thermal-Hydraulic Network
Authors: Cai Weihua , Franco Walfre , Arimany Gregor , Sen Mihir , Yang K. T. , McClain Rodney L.
Published: November 2006

The design of one secondary loop of a complex network often neglects the effect that its operation has on the others. The present is a study of hydrodynamic and thermal interaction between secondaries in a thermal-hydraulic network as the system goes from one steady state to another. Experimental results are related to those derived from a mathematical model. The network consists of a primary and three secondary loops. There is a water-to-water heat exchanger on each secondary, with the cooling coming from the primary and the heating from a separate loop. A step change is introduced by manually actuating a valve in one of the secondaries, resulting in changes in the other loops also. The response time of the temperature is found to be an order of magnitude higher than that of the flow rate, which is again an order of magnitude higher than the pressure difference. The steady-state results show that there is significant interaction, and that it is dependent on the initial operating condition. The hydrodynamic and thermal responses are found to be very different.
On Multiloop Interaction and Relative and Bristol
Gains
Authors: Eitelberg Eduard
Published: November 2006

The relationship between multiloop design and Bristol gains of a multivariable plant is shown. The Bristol and relative gains are distinguished. The Bristol gains B characterize the plant and the relative gains Λ characterize the designed feedback system. It is Λ, not B, that determines the interaction in loop designs. Λ is equal to B in a loop only at frequencies where all other loop gains are much above 0dB, usually significantly below the respective loop gain crossover frequencies. Λ=1 in a loop at frequencies where all other loop gains are much below 0dB, usually significantly above the respective loop gain crossover frequencies. The transition of Λ in a loop from B to 1 in the important medium frequency range is one of the most interesting and under-researched aspects of loop design interaction.
A Sliding-Mode Antiswing Trajectory Control for Overhead Cranes With High-Speed Load Hoisting
Authors: Lee Ho-Hoon , Liang Yi , Segura Del
Published: November 2006

In this paper we propose a sliding-mode antiswing control for overhead cranes. The objective of this study is to realize an antiswing trajectory control with high-speed load hoisting. A sliding-mode antiswing trajectory control scheme is designed based on the Lyapunov stability theorem, where a sliding surface, coupling the trolley motion with load swing, is adopted for a direct damping control of load swing. The proposed control guarantees asymptotic stability while keeping all internal signals bounded. In association with a new antiswing motion planning scheme, the proposed control realizes a typical antiswing trajectory control in practice, allowing high-speed load-hoisting motion and sufficient damping of load swing. The proposed control is simple for a real-time implementation with high-frequency sampling. The effectiveness of the proposed control has been confirmed by experiments.
The Relationship between Quinolone Exposures and Resistance Amplification Is Characterized by an Inverted U: a New Paradigm for Optimizing Pharmacodynamics To Counterselect Resistance
Authors: Tam Vincent H. , Louie Arnold , Deziel Mark R. , Liu Weiguo , Drusano George L.
Published: November 2006

We determined the relationship between garenoxacin exposure and quinolone-resistant subpopulations for three bacterial isolates in an in vitro hollow-fiber infection model. An “inverted-U” relationship was identified wherein resistant subpopulations rose initially and then declined with increasing exposure, until reaching a threshold that prevented resistance amplifications. Different targets for the area under the concentration-time curve over 24 h/MIC ratio were required for different bacteria.
Caenorhabditis elegans
as a Model To Determine Fitness of Antibiotic-Resistant
Salmonella enterica
Serovar Typhimurium
Authors: Paulander Wilhelm , Pennhag Alexandra , Andersson Dan I. , Maisnier-Patin Sophie
Published: November 2006

We used the ability of
Salmonella enterica
serovar Typhimurium to colonize the gut of
Caenorhabditis elegans
to measure the fitness costs imposed by antibiotic resistance mutations. The fitness costs determined in the nematode were similar to those measured in mice, validating its use as a simple host model to evaluate bacterial fitness.
Efficacy of Bacteriophage Therapy against Gut-Derived Sepsis Caused by
Pseudomonas aeruginosa
in Mice
Authors: Watanabe Ryohei , Matsumoto Tetsuya , Sano Go , Ishii Yoshikazu , Tateda Kazuhiro , Sumiyama Yoshinobu , Uchiyama Jumpei , Sakurai Shingo , Matsuzaki Shigenobu , Imai Shosuke , Yamaguchi Keizo
Published: November 2006

We evaluated the efficacy of bacteriophage (phage) therapy by using a murine model of gut-derived sepsis caused by
Pseudomonas aeruginosa
that closely resembles the clinical pathophysiology of septicemia in humans. Oral administration of a newly isolated lytic phage strain (KPP10) significantly protected mice against mortality (survival rates, 66.7% for the phage-treated group versus 0% for the saline-treated control group;
P
< 0.01). Mice treated with phage also had lower numbers of viable
P. aeruginosa
cells in their blood, liver, and spleen. The levels of inflammatory cytokines (tumor necrosis factor alpha TNF-α, interleukin-1β [IL-1β], and IL-6) in blood and liver were significantly lower in phage-treated mice than in phage-untreated mice. The number of viable
P. aeruginosa
cells in fecal matter in the gastrointestinal tract was significantly lower in phage-treated mice than in the saline-treated control mice. We also studied the efficacy of phage treatment for intraperitoneal infection caused by
P. aeruginosa
and found that phage treatment significantly improved the survival of mice, but only under limited experimental conditions. In conclusion, our findings suggest that oral administration of phage may be effective against gut-derived sepsis caused by
P. aeruginosa
.
In Vitro and In Vivo Activities of Chios Mastic Gum Extracts and Constituents against
Helicobacter pylori
Authors: Paraschos Sotirios , Magiatis Prokopios , Mitakou Sofia , Petraki Kalliopi , Kalliaropoulos Antonios , Maragkoudakis Petros , Mentis Andreas , Sgouras Dionyssios , Skaltsounis Alexios-Leandros
Published: November 2006

The extracts and pure major constituents of Chios mastic gum (resin of
Pistacia lentiscus
var.
chia
) were tested for their activities against
Helicobacter pylori
. A total mastic extract without polymer (TMEWP) was prepared after removal of the contained insoluble polymer in order to ameliorate solubility and enhance in vivo activity. Administration of TMEWP to
H. pylori
SS1-infected mice over the period of 3 months with an average dose of 0.75 mg/day led to an approximately 30-fold reduction in the
H. pylori
colonization (1.5 log CFU/g of tissue). However, no attenuation in the
H. pylori
-associated chronic inflammatory infiltration and the activity of chronic gastritis was observed. To further characterize potential active mastic constituents, the TMEWP was separated into an acidic and a neutral fraction. Both were extensively characterized by nuclear magnetic resonance and mass spectroscopy to elucidate the structure of the components contained within each fraction. After chromatographic separation, the acid fraction gave the major triterpenic acids, while the neutral fraction gave several triterpenic alcohols and aldehydes. Mastic extracts and isolated pure triterpenic acids were tested for in vitro activity against a panel of 11
H. pylori
clinical strains. The acid fraction was found to be the most active extract (minimum bactericidal concentration [MBC], 0.139 mg/ml), and the most active pure compound was isomasticadienolic acid (MBC, 0.202 mg/ml [0.443 mM]). Our results show that administration of TMEWP may be effective in reducing
H. pylori
colonization and that the major triterpenic acids in the acid extract may be responsible for such an activity.
Steady-State Pharmacokinetics of Micafungin and Voriconazole after Separate and Concomitant Dosing in Healthy Adults
Authors: Keirns J. , Sawamoto T. , Holum M. , Buell D. , Wisemandle W. , Alak A.
Published: November 2006

We assessed the pharmacokinetics and interactions of steady-state micafungin (Mycamine) or placebo with steady-state voriconazole in 35 volunteers. The 90% confidence intervals around the least-squares mean ratios for micafungin pharmacokinetic parameters and placebo-corrected voriconazole pharmacokinetic parameters were within the 80%-to-125% limits, indicating an absence of drug interaction.
Tolerance to the Glycopeptides Vancomycin and Teicoplanin in Coagulase-Negative Staphylococci
Authors: Bourgeois Ingrid , Pestel-Caron Martine , Lemeland Jean-Francois , Pons Jean-Louis , Caron Francois
Published: November 2006

Tolerance to vancomycin and teicoplanin in 90 clinical isolates of coagulase-negative staphylococci (CoNS) was investigated by time-kill curve methodology. Only six strains, belonging to the
Staphylococcus lugdunensis
species, exhibited tolerance. The seven other
S. lugdunensis
strains tested displayed weak susceptibility to the bactericidal activity of glycopeptides compared to the other CoNS. These phenomena are of concern, since
S. lugdunensis
is recognized as one of the most pathogenic CoNS.
Development and Characterization of a Novel Single-Cycle Recombinant-Virus Assay To Determine Human Immunodeficiency Virus Type 1 Coreceptor Tropism
Authors: Whitcomb Jeannette M. , Huang Wei , Fransen Signe , Limoli Kay , Toma Jonathan , Wrin Terri , Chappey Colombe , Kiss Linda D. B. , Paxinos Ellen E. , Petropoulos Christos J.
Published: November 2006

Most human immunodeficiency virus type 1 (HIV-1) strains require either the CXCR4 or CCR5 chemokine receptor to efficiently enter cells. Blocking viral binding to these coreceptors is an attractive therapeutic target. Currently, several coreceptor antagonists are being evaluated in clinical trials that require characterization of coreceptor tropism for enrollment. In this report, we describe the development of an automated and accurate procedure for determining HIV-1 coreceptor tropism (Trofile) and its validation for routine laboratory testing. HIV-1 pseudoviruses are generated using full-length
env
genes derived from patient virus populations. Coreceptor tropism is determined by measuring the abilities of these pseudovirus populations to efficiently infect CD4
+
/U87 cells expressing either the CXCR4 or CCR5 coreceptor. Viruses exclusively and efficiently infecting CXCR4
+
/CD4
+
/U87 cells are designated X4-tropic. Conversely, viruses exclusively and efficiently infecting CCR5
+
/CD4
+
/U87 cells are designated R5-tropic. Viruses capable of infecting both CXCR4
+
/CD4
+
/U87 and CCR5
+
/CD4
+
/U87 cells are designated dual/mixed-tropic. Assay accuracy and reproducibility were established by evaluating the tropisms of well-characterized viruses and the variability among replicate results from samples tested repeatedly. The viral subtype, hepatitis B virus or hepatitis C virus coinfection, and the plasma viral load did not affect assay performance. Minority subpopulations with alternate tropisms were reliably detected when present at 5 to 10%. The plasma viral load above which samples can be amplified efficiently in the Trofile assay is 1,000 copies per ml of plasma. Trofile has been automated for high-throughput use; it can be used to identify patients most likely to benefit from treatment regimens that include a coreceptor inhibitor and to monitor patients on treatment for the emergence of resistant virus populations that switch coreceptor tropism.
Efficacy of Delayed Treatment with ST-246 Given Orally against Systemic Orthopoxvirus Infections in Mice
Authors: Quenelle Debra C. , Buller R. M. L. , Parker Scott , Keith Kathy A. , Hruby Dennis E. , Jordan Robert , Kern Earl R.
Published: November 2006

ST-246 was evaluated for activity against cowpox virus (CV), vaccinia virus (VV), and ectromelia virus (ECTV) and had an in vitro 50% effective concentration (EC
50
) of 0.48 μM against CV, 0.05 μM against VV, and 0.07 μM against ECTV. The selectivity indices were >208 and >2,000 for CV and VV, respectively. The in vitro antiviral activity of ST-246 was significantly greater than that of cidofovir, which had an EC
50
of 41.1 μM against CV and 29.2 μM against VV, with selectivity indices of >7 and >10, respectively. ST-246 administered once daily by oral gavage to mice infected intranasally with CV beginning 4 h or delayed until 72 h postinoculation was highly effective when given for a 14-day duration using 100, 30, or 10 mg/kg of body weight. When 100 mg/kg of ST-246 was administered to VV-infected mice, a duration of 5 days was sufficient to significantly reduce mortality even when treatment was delayed 24 h postinoculation. Viral replication in liver, spleen, and kidney, but not lung, of CV- or VV-infected mice was reduced by ST-246 compared to levels for vehicle-treated mice. When 100 mg/kg of ST-246 was given once daily to mice infected by the intranasal route with ECTV, treatment for 10 days prevented mortality even when treatment was delayed up to 72 h after viral inoculation. Viral replication in target organs of ECTV-infected mice was also reduced.
Estimating True Antimalarial Efficacy by Heteroduplex Tracking Assay in Patients with Complex
Plasmodium falciparum
Infections
Authors: Kwiek Jesse J. , Alker Alisa P. , Wenink Emily C. , Chaponda Marjorie , Kalilani Linda V. , Meshnick Steven R.
Published: November 2006

Heteroduplex tracking assays (HTAs) of
Plasmodium falciparum
merozoite surface protein 1 block-2 were used to assess complexity of infection and treatment efficacy in a trial of three antimalarial treatments in 141 Malawian pregnant women. An elevated complexity of infection (COI) was associated with anemia, parasite burden, and human immunodeficiency virus infection but was not associated with age or gravidity. Comparisons of HTA patterns before and after treatment allowed the classification of 20 of 30 (66%) recurrent episodes as either definite treatment failures or reinfections. An elevated COI was strongly associated with treatment failure (
P
= 0.003). An algorithm was developed to assign a probability of failure for the 10 indeterminate participants, some of whose infections shared a single variant of high prevalence (>10%). By summing these probabilities, treatment efficacy was estimated.
Diversity of Ampicillin Resistance Genes and Antimicrobial Susceptibility Patterns in
Haemophilus influenzae
Strains Isolated in Korea
Authors: Kim In-Suk , Ki Chang-Seok , Kim Sunjoo , Oh Won Sup , Peck Kyong Ran , Song Jae-Hoon , Lee Kyungwon , Lee Nam Yong
Published: November 2006

By Etest determination of the susceptibilities of 229
Haemophilus influenzae
strains isolated in Korea to 10 antibiotics, the isolates were found to be antibiotic nonsusceptible in the following order: ampicillin (58.1%), trimethoprim-sulfamethoxazole (52%), cefaclor (41.1%), clarithromycin (25.8%), chloramphenicol (14.0%), amoxicillin-clavulanic acid (13.5%), meropenem (11.7%), cefixime (10.9%), cefuroxime (9.2%), and levofloxacin (1.3%). The prevalences of each resistance class were 23.6% for β-lactamase-negative ampicillin-susceptible (BLNAS) strains; 37.6% for strains with the TEM-1 type β-lactamase gene; 1.3% for strains with the ROB-1 type β-lactamase gene; 29.3% for the β-lactamase-negative ampicillin-resistant (BLNAR) strains with a mutation in the
ftsI
gene, which encodes PBP 3; and 8.3% for β-lactamase-positive amoxicillin-clavulanate-resistant (BLPACR) strains, which showed both resistance mechanisms (i.e., a β-lactamase gene and a mutation in the
ftsI
gene). The MIC
50
s of all β-lactams, including cephem and meropenem agents, for the BLNAR strains were two to three times higher than those for the BLNAS strains. This study confirms that the prevalence of BLNAR and BLPACR strains is relatively high and for the first time confirms the presence of
H. influenzae
strains carrying
bla
ROB-1
in Korea. Even though mutations in another gene(s) might be involved in β-lactam resistance, these results suggest that mutations in the
ftsI
gene are important for the development of resistance to β-lactams in
H. influenzae
strains in Korea.
In Vitro Antimalarial Activity of Azithromycin, Artesunate, and Quinine in Combination and Correlation with Clinical Outcome
Authors: Noedl Harald , Krudsood Srivicha , Leowattana Wattana , Tangpukdee Noppadon , Thanachartwet Wipa , Looareesuwan Sornchai , Miller Robert Scott , Fukuda Mark , Jongsakul Krisada , Yingyuen Kritsanai , Sriwichai Sabaithip , Ohrt Colin , Knirsch Charles
Published: November 2006

Azithromycin when used in combination with faster-acting antimalarials has proven efficacious in treating
Plasmodium falciparum
malaria in phase 2 clinical trials. The aim of this study was to establish optimal combination ratios for azithromycin in combination with either dihydroartemisinin or quinine, to determine the clinical correlates of in vitro drug sensitivity for these compounds, and to assess the cross-sensitivity patterns. Seventy-three fresh
P. falciparum
isolates originating from patients from the western border regions of Thailand were successfully tested for their drug susceptibility in a histidine-rich protein 2 (HRP2) assay. With overall mean fractional inhibitory concentrations of 0.84 (95% confidence interval [CI] = 0.77 to 1.08) and 0.78 (95% CI = 0.72 to 0.98), the interactions between azithromycin and dihydroartemisinin, as well as quinine, were classified as additive, with a tendency toward synergism. The strongest tendency toward synergy was seen with a combination ratio of 1:547 for the combination with dihydroartemisinin and 1:44 with quinine. The geometric mean 50% inhibitory concentration (IC
50
) of azithromycin was 2,570.3 (95% CI = 2,175.58 to 3,036.58) ng/ml. The IC
50
s for mefloquine, quinine, and chloroquine were 11.42, 64.4, and 54.4 ng/ml, respectively, suggesting a relatively high level of background resistance in this patient population. Distinct correlations (
R
= 0.53;
P
= 0.001) between quinine in vitro results and parasite clearance may indicate a compromised sensitivity to this drug. The correlation with dihydroartemisinin data was weaker (
R
= 0.34;
P
= 0.038), and no such correlation was observed for azithromycin. Our in vitro data confirm that azithromycin in combination with artemisinin derivatives or quinine exerts additive to synergistic interactions, shows no cross-sensitivity with traditional antimalarials, and has substantial antimalarial activity on its own.
Posaconazole Enhances the Activity of Amphotericin B against
Aspergillus
Hyphae In Vitro
Authors: Perkhofer Susanne , Lugger Helene , Dierich Manfred P. , Lass-Flörl Cornelia
Published: November 2006

The MICs and fractional inhibitory concentrations of posaconazole (POS) and voriconazole (VRZ), alone and in combination with amphotericin B (AMB), for the conidia and hyphae of 100
Aspergillus
isolates were evaluated. POS-AMB had more synergistic activity against hyphae (75% of isolates) than VRZ-AMB (37%) and significantly more synergistic activity against hyphae than against conidia (12%).
A Novel Nonnucleoside Analogue That Inhibits Human Immunodeficiency Virus Type 1 Isolates Resistant to Current Nonnucleoside Reverse Transcriptase Inhibitors
Authors: Zhang Zhijun , Xu Wen , Koh Yung-Hyo , Shim Jae Hoon , Girardet Jean-Luc , Yeh Li-Tain , Hamatake Robert K. , Hong Zhi
Published: November 2006

Nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) are important components of current combination therapies for human immunodeficiency virus type 1 (HIV-1) infection. However, their low genetic barriers against resistance development, cross-resistance, and serious side effects can compromise the benefits of the two current drugs in this class (efavirenz and nevirapine). In this study, we report a novel and potent NNRTI, VRX-480773, that inhibits viruses from efavirenz-resistant molecular clones and most NNRTI-resistant clinical HIV-1 isolates tested. In vitro mutation selection experiments revealed that longer times were required for viruses to develop resistance to VRX-480773 than to efavirenz. RT mutations selected by VRX-480773 after 3 months of cell culture in the presence of 1 nM VRX-480773 carried the Y181C mutation, resulting in a less-than-twofold increase in resistance to the compound. A virus containing the double mutation V106I-Y181C emerged after 4 months, causing a sixfold increase in resistance. Viruses containing additional mutations of D123G, F227L, and T369I emerged when the cultures were incubated with increasing concentrations of VRX-480773. Most of the resistant viruses selected by VRX-480773 are susceptible to efavirenz. Oral administration of VRX-480773 to dogs resulted in plasma concentrations that were significantly higher than those required for the inhibition of wild-type and mutant viruses. These results warrant further clinical development of VRX-480773 for the treatment of HIV infection in both NNRTI-naive and -experienced patients.
Isolation and Characterization of Human Immunodeficiency Virus Type 1 Resistant to the Small-Molecule CCR5 Antagonist TAK-652
Authors: Baba Masanori , Miyake Hiroshi , Wang Xin , Okamoto Mika , Takashima Katsunori
Published: November 2006

TAK-652, a novel small-molecule chemokine receptor antagonist, is a highly potent and selective inhibitor of CCR5-using (R5) human immunodeficiency virus type 1 (HIV-1) replication in vitro. Since TAK-652 is orally bioavailable and has favorable pharmacokinetic profiles in humans, it is considered a promising candidate for an entry inhibitor of HIV-1. To investigate the resistance to TAK-652, peripheral blood mononuclear cells were infected with the R5 HIV-1 primary isolate KK and passaged in the presence of escalating concentrations of the compound for more than 1 year. After 67 weeks of cultivation, the escape virus emerged even in the presence of a high concentration of TAK-652. This virus displayed more than 200,000-fold resistance to TAK-652 compared with the wild type. The escape virus appeared to have cross-resistance to the structurally related compound TAK-779 but retained full susceptibility to TAK-220, which is from a different class of CCR5 antagonists. Furthermore, the escape virus was unable to use CXCR4 as a coreceptor. Analysis for Env amino acid sequences of escape viruses at certain points of passage revealed that amino acid changes accumulated with an increasing number of passages. Several amino acid changes not only in the V3 region but also in other Env regions seemed to be required for R5 HIV-1 to acquire complete resistance to TAK-652.
Multistep Resistance Selection and Postantibiotic-Effect Studies of the Antipneumococcal Activity of LBM415 Compared to Other Agents
Authors: Kosowska-Shick Klaudia , Credito Kim L. , Pankuch Glenn A. , DeWasse Bonifacio , McGhee Pamela , Appelbaum Peter C.
Published: November 2006

LBM415 is a peptide deformylase inhibitor active against gram-positive bacterial species and some gram-negative species. In multiselection studies, LBM415 had low MICs against all
Streptococcus pneumoniae
strains tested, regardless of their genotype, and selected resistant clones after 14 to 50 days. MIC increases correlated with changes mostly in the
70
GXGXAAXQ
77
motif in peptide deformylase. The postantibiotic effect of LBM415 ranged from 0.3 to 1.4 h.
Leishmania donovani
Polyamine Biosynthetic Enzyme Overproducers as Tools To Investigate the Mode of Action of Cytotoxic Polyamine Analogs
Authors: Roberts Sigrid C. , Jiang Yuqui , Gasteier Judith , Frydman Benjamin , Marton Laurence J. , Heby Olle , Ullman Buddy
Published: November 2006

A number of anticancer and antiparasitic drugs are postulated to target the polyamine biosynthetic pathway and polyamine function, but the exact mode of action of these compounds is still being elucidated. To establish whether polyamine analogs specifically target enzymes of the polyamine pathway, a model was developed using strains of the protozoan parasite
Leishmania donovani
that overproduce each of the polyamine biosynthetic enzymes. Promastigotes overexpressing episomal constructs encoding ornithine decarboxylase (ODC),
S
-adenosylmethionine decarboxylase (ADOMETDC), or spermidine synthase (SPDSYN) revealed robust overproduction of the corresponding polyamine biosynthetic enzyme. Polyamine pools, however, were either unchanged or only marginally affected, implying that regulatory mechanisms must exist. The ODC, ADOMETDC, and SPDSYN overproducer strains exhibited a high level of resistance to difluoromethylornithine, 5′-{[(
Z
)-4-amino-2-butenyl]methylamino}-5′-deoxyadenosine, and
n
-butylamine, respectively, confirming previous observations that these agents specifically target polyamine enzymes. Conversely, augmented levels of polyamine biosynthetic enzymes did not affect the sensitivity of
L. donovani
promastigotes to pentamidine, berenil, and mitoguazone, drugs that were postulated to target the polyamine pathway, implying alternative and/or additional targets for these agents. The sensitivities of wild-type and overproducing parasites to a variety of polyamine analogs were also tested. The polyamine enzyme-overproducing lines offer a rapid cell-based screen for assessing whether synthetic polyamine analogs exert their mechanism of action predominantly on the polyamine biosynthetic pathway in
L. donovani
. Furthermore, the drug resistance engendered by the amplification of target genes and the overproduction of the encoded protein offers a general strategy for evaluating and developing therapeutic agents that target specific proteins in
Leishmania
.
Contribution of FliC to Epithelial Cell Invasion by Enterohemorrhagic
Escherichia coli
O113:H21
Authors: Luck Shelley N. , Badea Luminita , Bennett-Wood Vicki , Robins-Browne Roy , Hartland Elizabeth L.
Published: November 2006

Enterohemorrhagic
Escherichia coli
(EHEC) O113:H21 can invade epithelial cells. In this study, we found that invasion but not adherence was inhibited by anti-FliC
H21
specific antibodies. In addition, deletion of

fliC
H21

from EHEC O113:H21 resulted in an eightfold decrease in invasion that was restored upon transcomplementation with

fliC
H21

but not with

fliC
H6

. These results suggested that FliC plays an important role in the pathogenesis of infections caused by EHEC O113:H21 by allowing bacteria to penetrate the intestinal epithelium.
Susceptibility of Prostate Epithelial Cells toChlamydia muridarumInfection and Their Role in Innate Immunity by Recruitment of Intracellular Toll-Like Receptors 4 and 2 and MyD88 to the Inclusion
Authors: Mackern-Oberti Juan Pablo , Maccioni Mariana , Cuffini Cecilia , Gatti Gerardo , Rivero Virginia E.
Published: November 2006

AlthoughChlamydiainfections are widespread throughout the world, data about immunopathogenesis of genitourinary tract infections in males are very limited. In the present work we present an in vitro model of male genital tract-derived epithelial cells, more precisely prostate epithelial cells (PEC), to analyze if they are susceptible and able to respond toChlamydia muridaruminfection. Our results demonstrate that rat PEC are susceptible toC. muridaruminfection and respond to this pathogen by up-regulating different proinflammatory cytokine and chemokine genes that could participate in the recruitment and local activation of immune cells, therefore influencing innate and adaptive immune responses duringChlamydiainfection. Moreover, we analyzed the expression of Toll-like receptor 4 (TLR4), TLR2, and related molecules on PEC and the effect ofC. muridaruminfection on their expression. Our results demonstrate that PEC express significant levels of TLR4, CD14, TLR2, and the adaptor molecule MyD88 and up-regulate these proteins in response toC. muridaruminfection. Indeed, TLR4, CD14, TLR2, and the adaptor MyD88 are specifically recruited to the vicinity of the bacterial inclusion, suggesting that these TLRs are actively engaged in signaling from this intracellular location in these cells. This is, to our knowledge, the first time that an in vitro model of infection withChlamydiaof male tract-derived epithelial cells has been achieved, and it provides the opportunity to determine how these cells respond and participate in modulating innate and adaptive immune response duringChlamydiainfections.
The Translocated
Salmonella
Effector Proteins SseF and SseG Interact and Are Required To Establish an Intracellular Replication Niche
Authors: Deiwick Jörg , Salcedo Suzana P. , Boucrot Emmanuel , Gilliland Sarah M. , Henry Thomas , Petermann Nele , Waterman Scott R. , Gorvel Jean-Pierre , Holden David W. , Méresse Stéphane
Published: November 2006

The facultative intracellular pathogen
Salmonella enterica
causes a variety of diseases, including gastroenteritis and typhoid fever. Inside epithelial cells,
Salmonella
replicates in vacuoles, which localize in the perinuclear area in close proximity to the Golgi apparatus. Among the effector proteins translocated by the
Salmonella
pathogenicity island 2-encoded type III secretion system, SifA and SseG have been shown necessary but not sufficient to ensure the intracellular positioning of
Salmonella
vacuoles. Hence, we have investigated the involvement of other secreted effector proteins in this process. Here we show that SseF interacts functionally and physically with SseG but not SifA and is also required for the perinuclear localization of
Salmonella
vacuoles. The observations show that the intracellular positioning of
Salmonella
vacuoles is a complex phenomenon resulting from the combined action of several effector proteins.
2,3-Butanediol Synthesis and the Emergence of the
Vibrio cholerae
El Tor Biotype
Authors: Yoon Sang Sun , Mekalanos John J.
Published: November 2006

Vibrio cholerae
is an aquatic bacterium that causes the severe diarrheal disease cholera.
V. cholerae
strains of the O1 serogroup exist as two biotypes, classical and El Tor. Toxigenic strains of the El Tor biotype emerged to cause the seventh pandemic of cholera in 1961 and subsequently displaced strains of the classical biotype both in the environment and as a cause of cholera within a decade. The factors that drove emergence of the El Tor biotype and the displacement of the classical biotype are unknown. Here, we show a unique difference in carbohydrate metabolism between these two biotypes. When grown with added carbohydrates, classical biotype strains generated a sharp decrease in medium pH, resulting in loss of viability. However, growth of El Tor biotype strain N16961 was enhanced due to its ability to produce 2,3-butanediol, a neutral fermentation end product, and suppress the accumulation of organic acids. An N16961 mutant (SSY01) defective in 2,3-butanediol synthesis showed the same defect in growth that classical biotype strains show in media rich in carbohydrates. Importantly, the SSY01 mutant was attenuated in its ability to colonize the intestines of infant mice, suggesting that host carbohydrates may be available to
V. cholerae
within the intestinal environment. Similarly, the SSY01 mutant failed to develop biofilms when utilizing
N
-acetyl-
d
-glucosamine as a carbon source. Because growth on
N
-acetyl-
d
-glucosamine likely reflects the ability of a strain to grow on chitin in certain aquatic environments, we conclude that the strains of classical biotype are likely defective compared to those of El Tor in growth in any environmental niche that is rich in chitin and/or other metabolizable carbohydrates. We propose that the ability to metabolize sugars without production of acid by-products might account for the improved evolutionary fitness of the
V. cholerae
El Tor biotype compared to that of the classical biotype both as a global cause of cholera and as an environmental organism.
Ascaris suum-Derived Products Suppress Mucosal Allergic Inflammation in an Interleukin-10-Independent Manner via Interference with Dendritic Cell Function
Authors: McConchie Brittany W. , Norris Hillary H. , Bundoc Virgilio G. , Trivedi Shweta , Boesen Agnieszka , Urban Joseph F. , Keane-Myers Andrea M.
Published: November 2006

We have previously demonstrated that protection from allergic inflammation byAscaris suuminfection was characterized by a global increase in interleukin-10 (IL-10) and the development of protective CD4+/CD25+T cells (L. Schopf, S. Luccioli, V. Bundoc, P. Justice, C. C. Chan, B. J. Wetzel, H. H. Norris, J. F. Urban, Jr., and A. Keane-Myers, Investig. Ophthalmol. Vis. Sci.46:2772-2780, 2005). Here, we usedA. suumpseudocoelomic fluid (PCF) in lieu of infection to define molecular mechanisms of allergic protection in a mouse model of allergic inflammation. Mice were sensitized with ragweed (RW) and PCF (RW/PCF), PCF alone, or RW alone and then challenged intratracheally, intranasally, and supraocularly with RW. Histological examination of the eyes and lungs, analysis of the bronchoalveolar lavage fluid (BALF), and characterization of ex vivo cytokine responses were performed to determine allergic inflammatory responses. RW/PCF-treated mice had suppressed allergic immune responses compared to mice given RW alone. To investigate whether IL-10 was involved in PCF-mediated allergic protection, similar experiments were performed using mice genetically deficient for IL-10. Persistent protection from allergic disease was observed in the absence of IL-10, indicating the primary mechanism of PCF protection is IL-10 independent. Ex vivo and in vitro analysis of PCF-treated dendritic cells (DC) demonstrated reduced activation receptor expression and cytokine production in response to either RW or lipopolysaccharide stimulation. These findings extend previous studies that showed infection withA. suumalters expression of allergic disease and suggest that PCF can contribute to this effect by interference with DC function.
Oral Immunization withAcanthamoeba castellaniiMannose-Binding Protein Ameliorates Amoebic Keratitis
Authors: Garate M. , Alizadeh H. , Neelam S. , Niederkorn J. Y. , Panjwani N.
Published: November 2006

Acanthamoeba castellaniimannose-binding protein (MBP) mediates adhesion of the amoebae to corneal epithelial cells, a key first step in the pathogenesis ofAcanthamoebakeratitis (AK), a devastating corneal infection. In the present study, we demonstrate that oral immunization with recombinant MBP ameliorates AK in a hamster animal model and that this protection is associated with the presence of elevated levels of anti-MBP immunoglobulin A in the tear fluid of the immunized animals.
Identification and Characterization of a Novel ABC Iron Transport System,
fit
, in
Escherichia coli
Authors: Ouyang Zhiming , Isaacson Richard
Published: November 2006

A putative ABC transporter,
fit
, with significant homology to several bacterial iron transporters was identified in
Escherichia coli
. The
E. coli fit
system consists of six genes designated
fitA
,
-B
,
-C
,
-D
,
-E
, and -
R
. Based on DNA sequence analysis,
fit
encodes an outer membrane protein (FitA), a periplasmic binding protein (FitE), two permease proteins (FitC and -D), an ATPase (FitB), and a hypothetical protein (FitR). Introduction of the
E. coli fit
system into
E. coli
strain K-12 increased intracellular iron content and transformed bacteria were more sensitive to streptonigrin, which suggested that
fit
transports iron in
E. coli
. Expression of
fit
was studied using a
lacZ
reporter assay. A functional, bidirectional promoter was identified in the intergenic region between genes
fitA
and
fitB.
The expression of the
E. coli fit
system was found to be induced by iron limitation and repressed when Fe
2+
was added to minimal medium. Several
fit
mutants were created in
E. coli
using an in vitro transposon mutagenesis strategy. Mutations in
fit
did not affect bacterial growth in iron-restricted media. Using a growth promotion test, it was found that
fit
was not able to transport enterobactin, ferrichrome, transferrin, and lactoferrin in
E. coli
.
Mac-1+Cells Are the Predominant Subset in the Early Hepatic Lesions of Mice Infected withFrancisella tularensis
Authors: Rasmussen John W. , Cello Jeronimo , Gil Horacio , Forestal Colin A. , Furie Martha B. , Thanassi David G. , Benach Jorge L.
Published: November 2006

The cell composition of early hepatic lesions of experimental murine tularemia has not been characterized with specific markers. The appearance of multiple granulomatous-necrotic lesions in the liver correlates with a marked increase in the levels of serum alanine transferase and lactate dehydrogenase.Francisella tularensis, detected by specific antibodies, can be first noted by day 1 and becomes associated with the lesions by 5 days postinoculation. These lesions become necrotic, with some evidence of in situ apoptosis. The lesions do not contain B, T, or NK cells. Rather, the lesions are largely composed of two subpopulations of Mac-1+cells that are associated with the bacteria. Gr-1+Mac-1+immature myeloid cells and major histocompatibility complex class II-positive (MHC-II+) Mac-1+macrophages were the most abundant cell phenotypes found in the granuloma and are likely major contributors in controlling the infection in its early stages. Our findings have shown that there is an early development of hepatic lesions whereF. tularensiscolocalizes with both Gr-1+Mac-1+and MHC-II+Mac-1+cells.