bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Entropy Based Method for Probabilistic Sensitivity Analysis
in Engineering Design
Authors: Liu Huibin , Chen Wei , Sudjianto Agus
Published: February 2006

In this paper, a new Probabilistic Sensitivity Analysis (PSA) approach based on the concept of relative entropy is proposed for design under uncertainty. The relative entropy based method evaluates the impact of a random variable on a design performance by measuring the divergence between two probability density functions of the performance response, obtained before and after the variation reduction of the random variable. The method can be applied both over the whole distribution of a performance response [called global response probabilistic sensitivity analysis (GRPSA)] and in any interested partial range of a response distribution [called regional response probabilistic sensitivity analysis (RRPSA)]. Such flexibility of our approach facilitates its use under various scenarios of design under uncertainty, for instance in robust design, reliability-based design, and utility optimization. The proposed method is applicable to both the prior-design stage for variable screening when a design solution is yet identified and the post-design stage for uncertainty reduction after an optimal design has been determined. The saddlepoint approximation approach is introduced for improving the computational efficiency of applying our proposed method. The proposed method is illustrated and verified by numerical examples and industrial design cases.
Optimal Synthesis of Compliant Mechanisms Using Subdivision and Commercial FEA
Authors: Hull Patrick V. , Canfield Stephen
Published: February 2006

The field of distributed-compliance mechanisms has seen significant work in developing suitable topology optimization tools for their design. These optimal design tools have grown out of the techniques of structural optimization. This paper will build on the previous work in topology optimization and compliant mechanism design by proposing an alternative design space parametrization through control points and adding another step to the process, that of subdivision. The control points allow a specific design to be represented as a solid model during the optimization process. The process of subdivision creates an additional number of control points that help smooth the surface (for example a C2 continuous surface depending on the method of subdivision chosen) creating a manufacturable design free of some traditional numerical instabilities. Note that these additional control points do not add to the number of design parameters. This alternative parametrization and description as a solid model effectively and completely separates the design variables from the analysis variables during the optimization procedure. The motivation behind this work is to create an automated design tool from task definition to functional prototype created on a CNC or rapid-prototype machine. This paper will describe the proposed compliant mechanism design process and will demonstrate the procedure on several examples common in the literature.
Kinematic Registration in 3D Using the 2D Reuleaux Method
Authors: Eberharter Johannes K. , Ravani Bahram
Published: February 2006

This paper presents a method for kinematic registration in three dimensions using a classical technique from two-dimensional kinematics, namely the Reuleaux method. In three dimensions the kinematic registration problem involves reconstruction of a spatial displacement from data on a minimum of three homologous points at two finitely separated positions of a rigid body. When more than the minimum number of homologous points are specified or when errors in specification of these points are considered, the problem becomes an over determined approximation problem. A computational geometric method is presented, resulting in a linear solution of the over determined system. The results have applications in robotics, manufacturing, and biomedical imaging. The paper considers the kinematic registration when minimal, over-determined, infinitesimal, and perturbed sets of homologous point data are given.
Modeling of Evolutionary Design Database
Authors: Xue D. , Yang H. , Tu Y. L.
Published: February 2006

This research introduces an evolutionary design database model to describe design requirements and design results developed at different design stages from conceptual design to detailed design. In this model, the evolutionary design database is represented by a sequence of worlds corresponding to the design descriptions at different design stages. The design requirements and design results in each world are modeled using a database representation scheme that integrates both geometric descriptions and nongeometric descriptions. In each world, only the differences with its ancestor world are recorded. When the design descriptions in one world are changed, these changes are then propagated to its descendant worlds automatically. Consistency of the design descriptions in descendant worlds is also checked when design descriptions in an ancestor world are changed. A case study is conducted to show the effectiveness of this evolutionary design database model.
Sensitivity Analysis of the Orthoglide: A Three-DOF Translational Parallel Kinematic Machine
Authors: Caro Stéphane , Wenger Philippe , Bennis Fouad , Chablat Damien
Published: February 2006

In this paper, two complementary methods are introduced to analyze the sensitivity of a three-degree-of-freedom (3-DOF) translational parallel kinematic machine (PKM) with orthogonal linear joints: the Orthoglide. Although these methods are applied to a particular PKM, they can be readily applied to 3-DOF Delta-Linear PKM such as ones with their linear joints parallel instead of orthogonal. On the one hand, a linkage kinematic analysis method is proposed to have a rough idea of the influence of the length variations of the manipulator on the location of its end-effector. On the other hand, a differential vector method is used to study the influence of the length and angular variations in the parts of the manipulator on the position and orientation of its end-effector. Besides, this method takes into account the variations in the parallelograms. It turns out that variations in the design parameters of the same type from one leg to another have the same effect on the position of the end-effector. Moreover, the sensitivity of its pose to geometric variations is a minimum in the kinematic isotropic configuration of the manipulator. On the contrary, this sensitivity approaches its maximum close to the kinematic singular configurations of the manipulator.
Design of High-Stiffness Five-Bar and Seven-Bar Linkage Structures by Using the Concept of Orthogonal Paths
Authors: Tong Shih -Hsi
Published: February 2006

This paper presents a new approach for the synthesis of high-stiffness five-bar and seven- bar linkage structures based on the concept of orthogonal paths. The intersection point of two orthogonal paths is the location of a floating joint at which the motion is prevented to the maximum degree. Instead of analyzing link materials, deformations, and joint clearances, the approaches here provide designers with another way to obtain the geometrical configurations of five-bar and seven-bar linkage structures with high stiffness from a kinematic point of view. Two types of linkage structures, five-bar and seven-bar linkages, will be used for high-stiffness synthesis. The complete design procedures are presented for two different cases of each type.
Mechanical Design of a Robotic System for Automatic Installation of Magnetic Markers on the Roadway
Authors: James Randy , Ozkan Basar , Ravani Bahram
Published: February 2006

Magnetic markers embedded into the roadway pavements are used in Intelligent Transportation Systems to provide the reference signals necessary for guiding and controlling vehicles. This technology has already been implemented in several locations in California to provide driver assistance for snowplow operators in harsh winter environments. Installation of these magnetic markers into the roadway pavement is a tedious manual operation. In this paper, we present a novel design of a robotic system developed for installation of these magnetic markers into the roadway pavement. It is shown how dynamic modeling and simulation can be used with simple experimentation to develop a mechanical design of a robotic system to overcome undesirable effects of vibrations due to drilling the roadway. In addition, two new and innovative concepts are introduced in the design of a robotic system. One is the design of a roller-type traction drive to achieve linear motion that can be used in a gantry robotic system and the second is a self-alignment mechanism for proper insertion of magnetic markers that can be used for any insertion and assembly operations.
Modeling of a Fully Flexible 3PRS Manipulator for Vibration Analysis
Authors: Zhou Zili , Xi Jeff , Mechefske Chris K.
Published: February 2006

In this paper we provide a vibration analysis model and the modeling method for a fully flexible 3-Parallel-Revolute-joint-and-Spherical-joint (3PRS) manipulator—a sliding-leg tripod with flexible links and joints. A series of tripod configurations are set by rigid kinematics for simulation and experiment. All the links are modeled by finite elements: triangular membranes combined with bending plates for the moving platform and spatial beams for the legs. The joint complication is overcome by modeling the joint constraints as virtual springs. The nodal coordinates are statically condensed in order to validate the model. Using eigenvalue sensitivity analysis in terms of the condensed coordinates, the stiffness parameters of the joint virtual springs are adjusted in the experimental configurations until the acceleration frequency response functions (FRFs) from the calculation agree with the ones from the impact tests. The adjusted joint parameters are interpolated linearly into a series of configurations in simulation. The analysis shows that the model with the modified joints proposed in this paper is more effective than the conventional model with ideal joints for predicting the system natural frequencies and their variations against different tripod configurations. The good agreement between the simulation and the experiment at resonant peaks of the FRFs indicates the effectiveness of the modeling method.
Fourth-Order Kinematic Synthesis for Face-Milling Spiral Bevel Gears With Modified Radial Motion (MRM) Correction
Authors: Wang Pei-Yu , Fong Zhang-Hua
Published: February 2006

The use of a fourth-order motion curve is proposed by Stadtfeld and Gaiser to reduce the running noise of a bevel gear set recently. However, the methodology of synthesizing the tooth surfaces was not clearly shown in the literature. In this work, we proposed a methodology to synthesize the mating tooth surfaces of a face-milling spiral bevel gear set transmitting rotations with a predetermined fourth-order motion curve and contact path. A modified radial motion (MRM) correction in the machine plane of a computer numerical control (CNC) hypoid generator is introduced to modify the pinion tooth surface. With MRM correction, an arbitrary predetermined contact path on the pinion tooth surface with predetermined fourth-order motion curve can be achieved. Parameters of MRM correction are calculated according to the predetermined contact path and motion curve. As shown by the numerical examples, the contact path and the motion curve were obtained as expected by applying the MRM correction. The results of this work can be applied to the pinion, which is generated side-by-side (for example, fixed setting method, formate method, and Helixform method) and can be used as a basis for further study on the motion curve optimizations.
A New Proposal for Explicit Angle Calculation in Angular Contact Ball Bearing
Authors: Antoine J -F. , Abba G. , Molinari A.
Published: February 2006

In order to optimize the mechanical behavior of high speed rotors, it is useful to know the load-displacement law of the angular-contact ball bearing. The relationship between preload, speed, and contact angle is studied and a new analytical approach is proposed, giving explicitly and with good precision the contact angle versus preload and rotational speed for the special case of elastically preloaded high speed angular-contact ball bearing.
Mechanics and Sliding Friction in Belt Drives With Pulley Grooves
Authors: Kong Lingyuan , Parker Robert G.
Published: February 2006

The steady mechanics of a two-pulley belt drive system are examined where the pulley grooves, belt extension and wedging in the grooves, and the associated friction are considered. The belt is modeled as an axially moving string with the tangential and normal accelerations incorporated. The pulley grooves generate two-dimensional radial and tangential friction forces whose undetermined direction depends on the relative speed between belt and pulley along the contact arc. Different from single-pulley analyses, the entry and exit points between the belt spans and pulleys must be determined in the analysis due to the belt radial penetration into the pulley grooves and the coupling of the driver and driven pulley solutions. A new computational technique is developed to find the steady mechanics of a V-belt drive. This allows system analysis, such as speed/torque loss and maximum tension ratio. The governing boundary value problem (BVP) with undetermined boundaries is converted to a fixed boundary form solvable by a general-purpose BVP solver. Compared to flat belt drives or models that neglect radial friction, significant differences in the steady belt-pulley mechanics arise in terms of belt radial penetration, free span contact points, tension, friction, and speed variations.
A Note on the Waldron Construction for Transmission Angle Rectification
Authors: Chase Thomas R.
Published: February 2006

Graphical methods for synthesizing planar four-bar linkage motion generators to pass through two or three precision positions are well known. However, the practicality of these methods is limited by a high probability that the resulting linkages will suffer from kinematic defects. These may include change of circuit, change of branch or poor transmission angle. This technical brief distills earlier work of Waldron and associates (Chaung, J. C, Strong, R. T., and Waldron, K. J., 1981, J. Mech. Des., 103(3), pp. 657–664, Sun, J. W. H., and Waldron, K. J., 1981, Mech. Mach. Theory, 16(4), pp. 385–397, and Waldron, K. J., 1976, ASME J. Eng. Ind., 98(1), pp. 176–182) to an approachable procedure for controlling the transmission angle of four-bar linkages during synthesis. The procedure simultaneously eliminates the branch defect. It eliminates the circuit defect for some Grashof types but not others. The procedure is integrated with the established graphical synthesis methods by the addition of a few easily implemented substeps. The procedure is simple enough to be performed manually by undergraduates. Nevertheless, it is powerful enough to substantially improve the likelihood that the synthesized linkages will perform well when constructed. The procedure is explained in reference to an application.
Automation of Process Planning for Boring of Turned Components With Arbitrary Internal Geometry From a Semi-Finished Stock
Authors: Satish K Motipalli V. V. , Krishnaswami Prakash
Published: February 2006

This paper describes a novel method for automated process planning for boring of turned components with arbitrary internal geometry from a semi-finished stock. Earlier work has been reported on process planning for boring of components with monotonic internal geometry made from bar stock. This paper addresses the more general problem of process planning of parts with nonmonotonic internal geometry from arbitrary given the initial geometry, i.e., from a casting or from a semi-finished stock. With the algorithms developed, we are able to achieve full automation of all aspects of the process plan, including operations sequencing, parameter selection, numerical control (NC) code generation, etc. Thus, it becomes possible to go from design to NC code in a fully automated fashion. In the present work we focus on a tightly defined part family, which results in very simple but robust automation algorithms. This is in contrast to much of the reported work on automated process planning, which generally targets broad part families, leading to complex algorithms that fall short of complete design-to-NC automation.
Noncoding RNAs of Trithorax Response Elements Recruit
Drosophila
Ash1 to Ultrabithorax
Authors: Sanchez-Elsner Tilman , Gou Dawei , Kremmer Elisabeth , Sauer Frank
Published: February 2006

Homeotic genes contain cis-regulatory trithorax response elements (TREs) that are targeted by epigenetic activators and transcribed in a tissue-specific manner. We show that the transcripts of three TREs located in the
Drosophila
homeotic gene
Ultrabithorax
(
Ubx
) mediate transcription activation by recruiting the epigenetic regulator Ash1 to the template TREs. TRE transcription coincides with
Ubx
transcription and recruitment of Ash1 to TREs in
Drosophila
. The SET domain of Ash1 binds all three TRE transcripts, with each TRE transcript hybridizing with and recruiting Ash1 only to the corresponding TRE in chromatin. Transgenic transcription of TRE transcripts restores recruitment of Ash1 to
Ubx
TREs and restores
Ubx
expression in
Drosophila
cells and tissues that lack endogenous TRE transcripts. Small interfering RNA–induced degradation of TRE transcripts attenuates Ash1 recruitment to TREs and
Ubx
expression, which suggests that noncoding TRE transcripts play an important role in epigenetic activation of gene expression.
Structure of a DNA Glycosylase Searching for Lesions
Authors: Banerjee Anirban , Santos Webster L. , Verdine Gregory L.
Published: February 2006

DNA glycosylases must interrogate millions of base pairs of undamaged DNA in order to locate and then excise one damaged nucleobase. The nature of this search process remains poorly understood. Here we report the use of disulfide cross-linking (DXL) technology to obtain structures of a bacterial DNA glycosylase, MutM, interrogating undamaged DNA. These structures, solved to 2.0 angstrom resolution, reveal the nature of the search process: The protein inserts a probe residue into the helical stack and severely buckles the target base pair, which remains intrahelical. MutM therefore actively interrogates the intact DNA helix while searching for damage.
Cell Type Regulates Selective Segregation of Mouse Chromosome 7 DNA Strands in Mitosis
Authors: Armakolas Athanasios , Klar Amar J. S.
Published: February 2006

After chromosome replication, sister chromatid copies are generally thought to segregate randomly to daughter cells. However, sister chromatids differ in their DNA strands, with each chromatid inheriting one older strand that is paired to a newly synthesized strand. Genetic analysis with a homologous chromosome pair indicated nonrandom chromatid distribution in embryonic stem cells. Biased segregation pattern was also found in all 100 endoderm cells examined, but not in any of the 165 neuroectoderm cells. In contrast, the mesoderm, cardiomyocyte, and pancreatic cells exhibited a random mode of segregation. Strand distribution mechanisms regulated by cell type may have consequences for cellular differentiation and for evolving strategies for developmental mechanisms.
Bacterial Small-Molecule Signaling Pathways
Authors: Camilli Andrew , Bassler Bonnie L.
Published: February 2006

Bacteria use diverse small molecules for extra- and intracellular signaling. They scan small-molecule mixtures to access information about both their extracellular environment and their intracellular physiological status, and based on this information, they continuously interpret their circumstances and react rapidly to changes. Bacteria must integrate extra- and intracellular signaling information to mount appropriate responses to changes in their environment. We review recent research into two fundamental bacterial small-molecule signaling pathways: extracellular quorum-sensing signaling and intracellular cyclic dinucleotide signaling. We suggest how these two pathways may converge to control complex processes including multicellularity, biofilm formation, and virulence. We also outline new questions that have arisen from recent studies in these fields.
Comment on "On the Regulation of Populations of Mammals, Birds, Fish, and Insects" I
Authors: Getz Wayne M. , Lloyd-Smith James O.
Published: February 2006

Sibly
et al
. (Reports, 22 July 2005, p. 607) concluded that density dependence acts far below the carrying capacity in most animal populations. We argue that the authors confused discrete and continuous models, that their best-fit models cannot explain observed oscillations, and that their estimation procedures appear biased. They also neglected trophic and migratory processes, which we demonstrate could underlie their empirical findings.
Molecular Linkage Between the Kinase ATM and NF-κB Signaling in Response to Genotoxic Stimuli
Authors: Wu Zhao-Hui , Shi Yuling , Tibbetts Randal S. , Miyamoto Shigeki
Published: February 2006

The transcription factor NF-κB modulates apoptotic responses induced by genotoxic stress. We show that NF-κB essential modulator (NEMO), the regulatory subunit of IκB kinase (IKK) (which phosphorylates the NF-κB inhibitor IκB), associates with activated ataxia telangiectasia mutated (ATM) after the induction of DNA double-strand breaks. ATM phosphorylates serine-85 of NEMO to promote its ubiquitin-dependent nuclear export. ATM is also exported in a NEMO-dependent manner to the cytoplasm, where it associates with and causes the activation of IKK in a manner dependent on another IKK regulator, a protein rich in glutamate, leucine, lysine, and serine (ELKS). Thus, regulated nuclear shuttling of NEMO links two signaling kinases, ATM and IKK, to activate NF-κB by genotoxic signals.
Response to Comments on "On the Regulation of Populations of Mammals, Birds, Fish, and Insects"
Authors: Sibly Richard M. , Barker Daniel , Denham Michael C. , Hone Jim , Pagel Mark
Published: February 2006

The technical comments by Getz and Lloyd-Smith, Ross, and Doncaster focus on specific aspects of our analysis and estimation and do not demonstrate any results opposing our key conclusion—that, contrary to what was previously believed, the relation between a population's growth rate (
pgr
) and its density is generally concave.
Microheterogeneity of Singlet Oxygen Distributions in Irradiated Humic Acid Solutions
Authors: Latch Douglas E. , McNeill Kristopher
Published: February 2006

Singlet oxygen (
1
O
2
) is a highly reactive species formed through solar irradiation of organic matter in environmental waters. Implicated in a range of reactions, it has proven difficult to quantify its spatial distribution in natural waters. We assessed the microheterogeneous distribution of
1
O
2
in irradiated solutions containing chromophoric dissolved organic matter (CDOM) by using molecular probes of varying hydrophobicity. The apparent
1
O
2
concentrations ([
1
O
2
]
app
), measured by recently developed hydrophobic trap-and-trigger chemiluminescent probe molecules, were orders of magnitude higher than those measured by the conventional hydrophilic probe molecule furfuryl alcohol. The differential [
1
O
2
]
app
values measured by these probes reflect a steep concentration gradient between the CDOM macromolecules and the aqueous phase. A detailed kinetic model based on the data predicts probabilistic
1
O
2
distributions under different solvent conditions.
Effects of Solar Flares on the Ionosphere of Mars
Authors: Mendillo Michael , Withers Paul , Hinson David , Rishbeth Henry , Reinisch Bodo
Published: February 2006

All planetary atmospheres respond to the enhanced x-rays and ultraviolet (UV) light emitted from the Sun during a flare. Yet only on Earth are observations so continuous that the consequences of these essentially unpredictable events can be measured reliably. Here, we report observations of solar flares, causing up to 200% enhancements to the ionosphere of Mars, as recorded by the Mars Global Surveyor in April 2001. Modeling the altitude dependence of these effects requires that relative enhancements in the soft x-ray fluxes far exceed those in the UV.
Comment on "On the Regulation of Populations of Mammals, Birds, Fish, and Insects" III
Authors: Doncaster C. Patrick
Published: February 2006

Stochasticity in time series explains concave responses of per capita growth rate to population size. The gradients with the natural log of population size have more biological importance because they measure strength of density compensation. Its weakening with increasing body size across taxa (Sibly
et al
., Reports, 22 July 2005, p. 607) is consistent with slower responses in ascent than descent toward carrying capacity. Time series therefore suggest that populations of large-bodied animals underfill their environments.
Dendritic Cell Apoptosis in the Maintenance of Immune Tolerance
Authors: Chen Min , Wang Yui-Hsi , Wang Yihong , Huang Li , Sandoval Hector , Liu Yong-Jun , Wang Jin
Published: February 2006

Apoptosis in the immune system is critical for maintaining self-tolerance and preventing autoimmunity. Nevertheless, inhibiting apoptosis in lymphocytes is not alone sufficient to break self-tolerance, suggesting the involvement of other cell types. We investigated whether apoptosis in dendritic cells (DCs) helps regulate self-tolerance by generating transgenic mice expressing the baculoviral caspase inhibitor, p35, in DCs (DC-p35). DC-p35 mice displayed defective DC apoptosis, resulting in their accumulation and, in turn, chronic lymphocyte activation and systemic autoimmune manifestations. The observation that a defect in DC apoptosis can independently lead to autoimmunity is consistent with a central role for these cells in maintaining immune self-tolerance.
Anthropogenic and Natural Influences in the Evolution of Lower Stratospheric Cooling
Authors: Ramaswamy V. , Schwarzkopf M. D. , Randel W. J. , Santer B. D. , Soden B. J. , Stenchikov G. L.
Published: February 2006

Observations reveal that the substantial cooling of the global lower stratosphere over 1979–2003 occurred in two pronounced steplike transitions. These arose in the aftermath of two major volcanic eruptions, with each cooling transition being followed by a period of relatively steady temperatures. Climate model simulations indicate that the space-time structure of the observed cooling is largely attributable to the combined effect of changes in both anthropogenic factors (ozone depletion and increases in well-mixed greenhouse gases) and natural factors (solar irradiance variation and volcanic aerosols). The anthropogenic factors drove the overall cooling during the period, and the natural ones modulated the evolution of the cooling.
Coherent Sign Switching in Multiyear Trends of Microbial Plankton
Authors: Li William K. W. , Harrison W. Glen , Head Erica J. H.
Published: February 2006

Since the 1990s, phytoplankton biomass on the continental shelf of Nova Scotia and in the Labrador Sea has undergone sustained changes in the spring and fall, which are accompanied by changes in bacterioplankton that are dampened in amplitude but coherent in the direction of change. A reversal of trend in biomass change, so-called sign switching, occurs both in time and in space. Thus, whenever (spring or fall) and wherever (Scotian Shelf or Labrador Sea) phytoplankton increase or decrease, so also does bacterioplankton. This tandem sign switch indicates coupling of the trophic levels at a multiyear time scale and contributes to an ecological fingerprint of systemwide forcing.
Ecology Beginning with the Botanists
Authors: Slack Nancy
Published: February 2006

The Evolution of American Ecology, 1890-2000
.
By Sharon E. Kingsland
. Johns Hopkins University Press, Baltimore, MD, 2005. 325 pp. $50, £33.50. ISBN 0-8018-8171-4.

The author explores the course of ecology in the United States from its origins in the 1890s through the changing intellectual and cultural environments of the 20th century.
X-ray Flares from Postmerger Millisecond Pulsars
Authors: Dai Z. G. , Wang X. Y. , Wu X. F. , Zhang B.
Published: February 2006

Recent observations support the suggestion that short-duration gamma-ray bursts are produced by compact star mergers. The x-ray flares discovered in two short gamma-ray bursts last much longer than the previously proposed postmerger energy-release time scales. Here, we show that they can be produced by differentially rotating, millisecond pulsars after the mergers of binary neutron stars. The differential rotation leads to windup of interior poloidal magnetic fields and the resulting toroidal fields are strong enough to float up and break through the stellar surface. Magnetic reconnection–driven explosive events then occur, leading to multiple x-ray flares minutes after the original gamma-ray burst.
Roaming Mars
Authors: Rowan Linda
Published: February 2006

Roving Mars
.
By George Butler
. Walt Disney Pictures, Burbank, CA, 2006. An IMAX film, 40 minutes. http://disney.go.com/disneypictures/rovingmars

Blending images from the Mars rovers and digital animation, the film takes viewers along as Spirit and Opportunity roam the red planet's surface.
Helicobacter pyloriInduces IκB Kinase α Nuclear Translocation and Chemokine Production in Gastric Epithelial Cells
Authors: Hirata Yoshihiro , Maeda Shin , Ohmae Tomoya , Shibata Wataru , Yanai Ayako , Ogura Keiji , Yoshida Haruhiko , Kawabe Takao , Omata Masao
Published: February 2006

NF-κB is an important transcriptional factor that is involved in multiple cellular responses, such as inflammation and antiapoptosis. IκB kinase α (IKKα) and IKKβ, which are critical regulators of NF-κB activity, possess various mechanisms for NF-κB activation. This variability in NF-κB signaling may be associated with distinct inflammatory responses in specific cell types. The gastric pathogenHelicobacter pyloriis known to activate NF-κB. However, the role of IKK inH. pyloriinfection remains unclear. In this report, we show thatH. pyloriactivates both IKKα and IKKβ in gastric cancer cells and enhances NF-κB signaling in distinct manners. We found that IKKβ acted as an IκBα kinase duringH. pyloriinfection, whereas IKKα did not.H. pyloriinduced IKKα nuclear translocation in time-, multiplicity of infection-, andcagpathogenicity island-dependent manners. In contrast, p100 processing, which is a known IKKα activity induced by several cytokines, was not induced byH. pylori. Both IKKs were responsible for chemokine secretion by infected cells. However, the antiapoptotic effect ofH. pyloriwas merely transduced by IKKβ. Microarray analysis and real-time PCR indicated that both IKKs were involved in the transcriptional activation of genes associated with inflammation, antiapoptosis, and signal transduction. Our results indicate thatH. pyloriactivates NF-κB via both IKKα and IKKβ using distinct mechanisms. IKKα nuclear translocation induced byH. pyloriis indispensable for appropriate inflammatory responses but not for antiapoptosis, which suggests a critical role for IKKα in gastritis development.
Interleukin-5 (IL-5) Augments the Progression of Liver Fibrosis by Regulating IL-13 Activity
Authors: Reiman Rachael M. , Thompson Robert W. , Feng Carl G. , Hari Danielle , Knight Rachel , Cheever Allen W. , Rosenberg Helene F. , Wynn Thomas A.
Published: February 2006

Eosinophils are frequently found in increased numbers in a variety of chronic fibrotic diseases; however, their role in the development of hepatic fibrosis has not been dissected in vivo. Here, we used interleukin-5 (IL-5) knockout (KO) mice to determine whether eosinophils contribute to the progressive liver fibrosis that develops in response to chronicSchistosoma mansoniinfection. Although infection intensities were similar in C57BL/6 and IL-5 KO mice, the average size of granulomas was significantly smaller in both acutely and chronically infected IL-5 KO mice. Their granulomas were also completely devoid of eosinophils. In addition, the knockout mice displayed over a 40% reduction in hepatic fibrosis by week 16 postinfection. The reduced fibrosis was associated with increased production of the antifibrotic cytokine gamma interferon. Moreover, although IL-13 production did not decrease consistently in the absence of IL-5, IL-13-triggered responses were substantially reduced in the granulomatous tissues. This was confirmed by analyzing the expression of several genes associated with alternative macrophage activation, including arginase 1, Fizz-1, and YM-1. Importantly, all of these IL-13-regulated genes have been linked with the mechanisms of wound healing and fibrosis. In addition to IL-5 polarizing the antigen-specific CD4+Th2 cell response, we found that granuloma eosinophils were themselves a significant source of IL-13. Thus, by producing profibrotic mediators and polarizing the Th2 response, these findings illustrate both direct and indirect roles for eosinophils and IL-5 in the pathogenesis of schistosomiasis-induced liver fibrosis. Thus, inhibiting the activity of IL-5 or eosinophils may prove effective for a variety of chronic fibrotic diseases.
Human Dendritic Cells followingAspergillus fumigatusInfection Express the CCR7 Receptor and a Differential Pattern of Interleukin-12 (IL-12), IL-23, and IL-27 Cytokines, Which Lead to a Th1 Response
Authors: Gafa Valérie , Lande Roberto , Gagliardi Maria Cristina , Severa Martina , Giacomini Elena , Remoli Maria Elena , Nisini Roberto , Ramoni Carlo , Di Francesco Paolo , Aldebert Delphine , Grillot Renée , Coccia Eliana M.
Published: February 2006

Aspergillus fumigatusis the most prevalent airborne fungal pathogen and causes fatal invasive aspergillosis in immunocompromised patients. Given the essential role of dendritic cells (DC) in initiating and regulating immune responses, we investigated the impact ofA. fumigatusconidial infection on human DC.A. fumigatusconidia were rapidly internalized and induced the release of tumor necrosis factor alpha within the first 8 h. AfterA. fumigatusinfection, the majority of DC underwent full maturation, although CCR7 expression was observed only in DC that had internalized the conidia. Additionally, the analysis of regulatory cytokines showed that infected DC simultaneously produced interleukin-12p70 (IL-12p70) and significant amounts of IL-10. IL-10 neutralization was not able to further increase IL-12p70 production from infected DC. Whereas the central role of IL-12 in the generation of Th1 cells has long been appreciated, recently two other members of the IL-12 family, IL-23 and IL-27, were reported to play important roles in the regulation of gamma interferon (IFN-γ) production from naïve and memory T cells.A. fumigatus-infected DC were also able to express high levels of IL-23p19 and low levels of IL-27p28 at later stages of infection. According to this expression pattern,A. fumigatus-infected DC were able to prime IFN-γ production of naïve T cells. Thus, this study on the expression of the new IL-12 family members controlling the Th1 response sheds light on a novel aspect of the contribution of DC to anti-Aspergillusimmunity.
Mutual Enhancement of Virulence by Enterotoxigenic and Enteropathogenic
Escherichia coli
Authors: Crane John K. , Choudhari Shilpa S. , Naeher Tonniele M. , Duffey Michael E.
Published: February 2006

Enterotoxigenic
Escherichia coli
(ETEC) and enteropathogenic
E. coli
(EPEC) are common causes of diarrhea in children in developing countries. Dual infections with both pathogens have been noted fairly frequently in studies of diarrhea around the world. In previous laboratory work, we noted that cholera toxin and forskolin markedly potentiated EPEC-induced ATP release from the host cell, and this potentiated release was found to be mediated by the cystic fibrosis transmembrane conductance regulator. In this study, we examined whether the ETEC heat-labile toxin (LT) or the heat-stable toxin (STa, also known as ST) potentiated EPEC-induced ATP release. We found that crude ETEC culture filtrates, as well as purified ETEC toxins, did potentiate EPEC-induced ATP release in cultured T84 cells. Coinfection of T84 cells with live ETEC plus EPEC bacteria also resulted in enhanced ATP release compared to EPEC alone. In Ussing chamber studies of chloride secretion, adenine nucleotides released from the host by EPEC also significantly enhanced the chloride secretory responses that were triggered by crude ETEC filtrates, purified STa, and the peptide hormone guanylin. In addition, adenosine and LT had additive or synergistic effects in inducing vacuole formation in T84 cells. Therefore, ETEC toxins and EPEC-induced damage to the host cell both enhance the virulence of the other type of
E. coli
. Our in vitro data demonstrate a molecular basis for a microbial interaction, which could result in increased severity of disease in vivo in individuals who are coinfected with ETEC and EPEC.
Molecular Characterization of Serine-, Alanine-, and Proline-Rich Proteins of
Trypanosoma cruzi
and Their Possible Role in Host Cell Infection
Authors: Baida Renata C. P. , Santos Márcia R. M. , Carmo Mirian S. , Yoshida Nobuko , Ferreira Danielle , Ferreira Alice Teixeira , El Sayed Najib M. , Andersson Bjorn , da Silveira José Franco
Published: February 2006

We previously reported the isolation of a novel protein gene family, termed SAP (serine-, alanine-, and proline-rich protein), from
Trypanosoma cruzi
. Aided by the availability of the completed genome sequence of
T. cruzi
, we have now identified 39 full-length sequences of SAP, six pseudogenes and four partial genes. SAPs share a central domain of about 55 amino acids and can be divided into four groups based on their amino (N)- and carboxy (C)-terminal sequences. Some SAPs have conserved N- and C-terminal domains encoding a signal peptide and a glycosylphosphatidylinositol anchor addition site, respectively. Analysis of the expression of SAPs in metacyclic trypomastigotes by two-dimensional electrophoresis and immunoblotting revealed that they are likely to be posttranslationally modified in vivo. We have also demonstrated that some SAPs are shed into the extracellular medium. The recombinant SAP exhibited an adhesive capacity toward mammalian cells, where binding was dose dependent and saturable, indicating a possible ligand-receptor interaction. SAP triggered the host cell Ca
2+
response required for parasite internalization. A cell invasion assay performed in the presence of SAP showed inhibition of internalization of the metacyclic forms of the CL strain. Taken together, these results show that SAP is involved in the invasion of mammalian cells by metacyclic trypomastigotes, and they confirm the hypothesis that infective trypomastigotes exploit an arsenal of surface glycoproteins and shed proteins to induce signaling events required for their internalization.
Antigen-Responsive CD4+T Cells from C3H Mice Chronically Infected withLeishmania amazonensisAre Impaired in the Transition to an Effector Phenotype
Authors: Ramer Amanda E. , Vanloubbeeck Yannick F. , Jones Douglas E.
Published: February 2006

C3HeB/FeJ mice challenged withLeishmania majordevelop a polarized Th1 response and subsequently heal, whereasLeishmania amazonensischallenge leads to chronic lesions with high parasite loads at 10 weeks postinfection. In this study, a comparison of draining lymph node cells fromL. amazonensis- andL. major-infected mice at 10 weeks postinfection showed equivalent percentages of effector/memory phenotype CD44hiCD4+T cells producing interleukin-2 (IL-2) and proliferating after antigen stimulation. However, these cells isolated fromL. amazonensis-infected mice were not skewed toward either a Th1 or Th2 phenotype in vivo, as evidenced by their unbiased Th1/Th2 transcription factor mRNA profile. In vivo antigen stimulation with added IL-12 failed to enhance gamma interferon (IFN-γ) production of CD4+T cells fromL. amazonensis-infected mice. Antigen stimulation of CD4+T cells fromL. amazonensis-infected mice in vitro in the presence of IL-12 resulted in production of only 10 to 15% of the IFN-γ produced by T cells fromL. major-infected mice under identical conditions. These results suggest that the CD4+T-cell response during chronicL. amazonensisinfection is limited during the transition from an early activated CD4+T-cell population to an effector cell population and demonstrate that these T cells have an intrinsic defect beyond the presence or absence of IL-12 during antigen stimulation.
The Frequency ofChlamydia trachomatisMajor Outer Membrane Protein-Specific CD8+T Lymphocytes in Active Trachoma Is Associated with Current Ocular Infection
Authors: Holland Martin J. , Faal Nkoyo , Sarr Isatou , Joof Hassan , Laye Mass , Cameron Ewen , Pemberton-Pigott Frederick , Dockrell Hazel M. , Bailey Robin L. , Mabey David C. W.
Published: February 2006

Chlamydia-specific cytotoxic T lymphocytes are able to control model infections but may be implicated in disease pathogenesis. HLA-A2 peptide tetramers toChlamydia trachomatismajor outer membrane protein 258-266 (MOMP258-266) and MOMP260-268 were used to characterize HLA class I-restricted CD8+T cells in Gambian children aged 4 to 15 years with clinical signs of active trachoma and/or infection withC. trachomatis. The frequencies of circulating HLA-A2 tetramer binding cells (TBC) were determined in whole blood samples by flow cytometric analysis. Initial screening of subjects with an anti-HLA-A2 antibody confirmed the presence of either HLA-A2 or HLA-A28. These were subsequently further divided by molecular subtyping. TheC. trachomatis-specific HLA-A2 peptide tetramers were able to bind T cells with receptors from subjects which were restricted by either the HLA-A2 or the HLA-A28 restriction element. In this population, the median value ofC. trachomatis-specific CD8+T cells was 0.02%, with frequencies of up to 3.71% of CD8+T cells reactive with a single tetramer in a minority of subjects. TBC were detected more often in subjects who were infected at the ocular surface, and their presence was associated with infection episodes of longer duration. Detection ofC. trachomatis-specific TBC was not associated with the presence of disease or with the estimated load of ocularC. trachomatisinfection at the time of sample collection. High frequencies ofC. trachomatis-specific cells did not predict subsequent appearance or resolution of the clinical disease signs of active trachoma.
CD40 Restrains In Vivo Growth ofToxoplasma gondiiIndependently of Gamma Interferon
Authors: Subauste Carlos S. , Wessendarp Matthew
Published: February 2006

CD40-CD154 interaction is pivotal for resistance against numerous pathogens. However, it is not known if this pathway can also enhance in vivo resistance in gamma interferon (IFN-γ)-deficient hosts. This is an important question because patients and mice with defects in type 1 cytokine response can control a variety of pathogens. While blockade of endogenous CD154 resulted in a remarkable increase in parasite load in IFN-γ−/−mice infected withToxoplasma gondii, in vivo administration of a stimulatory anti-CD40 monoclonal antibody markedly reduced parasite load. This latter effect took place even in T-cell-depleted mice and was accompanied by induction of macrophage toxoplasmacidal activity. CD40 stimulation restrictedT. gondiireplication independently of STAT1, p47 GTPases, and nitric oxide. In vivo CD40 ligation enhanced tumor necrosis factor alpha (TNF-α) production byT. gondii-infected macrophages. In addition, CD40 stimulation required the presence of TNF receptor 2 to reduce parasite load in vivo. These results suggest that CD40-CD154 interaction regulates IFN-γ-independent mechanisms of host protection through induction of macrophage antimicrobial activity and modulation of TNF-α signaling.
Biofilm Formation by
Moraxella catarrhalis
In Vitro: Roles of the UspA1 Adhesin and the Hag Hemagglutinin
Authors: Pearson Melanie M. , Laurence Cassie A. , Guinn Sarah E. , Hansen Eric J.
Published: February 2006

Mutant analysis was used to identify
Moraxella catarrhalis
gene products necessary for biofilm development in a crystal violet-based assay involving 24-well tissue culture plates. The wild-type
M. catarrhalis
strains that formed the most extensive biofilms in this system proved to be refractory to transposon mutagenesis, so an
M. catarrhalis
strain was constructed that was both able to form biofilms in vitro and amenable to transposon mutagenesis. Chromosomal DNA from the biofilm-positive strain O46E was used to transform the biofilm-negative strain O35E; transformants able to form biofilms were identified and subjected to transposon-mediated mutagenesis. Biofilm-negative mutants of these transformants were shown to have a transposon insertion in the
uspA1
gene. Nucleotide sequence analysis revealed that the biofilm-positive transformant T14 contained a hybrid O46E-O35E
uspA1
gene, with the N-terminal 155 amino acids being derived from the O46E UspA1 protein. Transformant T14 was also shown to be unable to express the Hag protein, which normally extends from the surface of the
M. catarrhalis
cell. Introduction of a wild-type O35E
hag
gene into T14 eliminated its ability to form a biofilm. When the hybrid O46E-O35E
uspA1
gene from T14 was used to replace the
uspA1
gene of O35E, this transformant strain did not form a biofilm. However, inactivation of the
hag
gene did allow biofilm formation by strain O35E expressing the hybrid O46E-O35E
uspA1
gene product. The Hag protein was shown to have an inhibitory or negative effect on biofilm formation by these
M. catarrhalis
strains in the crystal violet-based assay.
Binding of Vitronectin by theMoraxella catarrhalisUspA2 Protein Interferes with Late Stages of the Complement Cascade
Authors: Attia Ahmed S. , Ram Sanjay , Rice Peter A. , Hansen Eric J.
Published: February 2006

ManyMoraxella catarrhalisstrains are resistant to the bactericidal activity of normal human serum (NHS). The UspA2 protein of the serum-resistant strain O35E has previously been shown to be directly involved in conferring serum resistance on this strain. Testing of 11 additional serum-resistantM. catarrhaliswild-type isolates and theiruspA1anduspA2mutants showed that theuspA1mutants of all 11 strains were consistently serum resistant and that theuspA2mutants of these same 11 strains were always serum sensitive. Analysis of complement deposition on four different serum-resistantM. catarrhalisstrains and their serum-sensitiveuspA2mutants showed that, for three of these four strain sets, the wild-type and mutant strains bound similar amounts of early complement components. In contrast, there was a significant reduction in the amount of the polymerized C9 on the wild-type strains relative to that on theuspA2mutants. These same three wild-type strains bound more vitronectin than did theiruspA2mutants. UspA2 proteins from these three strains, when expressed inHaemophilus influenzae, bound vitronectin and conferred serum resistance on this organism. Furthermore, vitronectin-depleted NHS exhibited bactericidal activity against these same three serum-resistant wild-type strains; addition of purified vitronectin to this serum restored serum resistance. In contrast, binding of the complement regulator C4b-binding protein by theM. catarrhalisstrains used in this study was found to be highly variable and did not appear to correlate with the serum-resistant phenotype. These results indicate that binding of vitronectin by UspA2 is involved in the serum resistance ofM. catarrhalis; this represents the first example of vitronectin-mediated serum resistance on a microbe.