bluuebunny/crossref_metadata_2025 huggingface dataset:
Using an Extended Kalman Filter for Rigid Body Pose Estimation
Authors: Halvorsen Kjartan , Söderström Torsten , Stokes Virgil , Lanshammar Håkan
Published: May 2005

Rigid body pose is commonly represented as the rigid body transformation from one (often reference) pose to another. This is usually computed for each frame of data without any assumptions or restrictions on the temporal change of the pose. The most common algorithm was proposed by Söderkvist and Wedin (1993, “Determining the Movements of the Skeleton Using Well-configured Markers,” J. Biomech., 26, pp. 1473–1477), and implies the assumption that measurement errors are isotropic and homogenous. This paper describes an alternative method based on a state space formulation and the application of an extended Kalman filter (EKF). State space models are formulated, which describe the kinematics of the rigid body. The state vector consists of six generalized coordinates (corresponding to the 6 degrees of freedom), and their first time derivatives. The state space models have linear dynamics, while the measurement function is a nonlinear relation between the state vector and the observations (marker positions). An analytical expression for the linearized measurement function is derived. Tracking the rigid body motion using an EKF enables the use of a priori information on the measurement noise and type of motion to tune the filter. The EKF is time variant, which allows for a natural way of handling temporarily missing marker data. State updates are based on all the information available at each time step, even when data from fewer than three markers are available. Comparison with the method of Söderkvist and Wedin on simulated data showed a considerable improvement in accuracy with the proposed EKF method when marker data was temporarily missing. The proposed method offers an improvement in accuracy of rigid body pose estimation by incorporating knowledge of the characteristics of the movement and the measurement errors. Analytical expressions for the linearized system equations are provided, which eliminate the need for approximate discrete differentiation and which facilitate a fast implementation.
Biomechanical Study Using Fuzzy Systems to Quantify Collagen Fiber Recruitment and Predict Creep of the Rabbit Medial Collateral Ligament
Authors: Ali A. F. , Reda Taha M. M. , Thornton G. M. , Shrive N. G. , Frank C. B.
Published: May 2005

In normal daily activities, ligaments are subjected to repeated loads, and respond to this environment with creep and fatigue. While progressive recruitment of the collagen fibers is responsible for the toe region of the ligament stress-strain curve, recruitment also represents an elegant feature to help ligaments resist creep. The use of artificial intelligence techniques in computational modeling allows a large number of parameters and their interactions to be incorporated beyond the capacity of classical mathematical models. The objective of the work described here is to demonstrate a tool for modeling creep of the rabbit medial collateral ligament that can incorporate the different parameters while quantifying the effect of collagen fiber recruitment during creep. An intelligent algorithm was developed to predict ligament creep. The modeling is performed in two steps: first, the ill-defined fiber recruitment is quantified using the fuzzy logic. Second, this fiber recruitment is incorporated along with creep stress and creep time to model creep using an adaptive neurofuzzy inference system. The model was trained and tested using an experimental database including creep tests and crimp image analysis. The model confirms that quantification of fiber recruitment is important for accurate prediction of ligament creep behavior at physiological loads.
A Structural Constitutive Model For Collagenous Cardiovascular Tissues Incorporating the Angular Fiber Distribution
Authors: Driessen Niels J. B. , Bouten Carlijn V. C. , Baaijens Frank P. T.
Published: May 2005

Accurate constitutive models are required to gain further insight into the mechanical behavior of cardiovascular tissues. In this study, a structural constitutive framework for cardiovascular tissues is introduced that accounts for the angular distribution of collagen fibers. To demonstrate its capabilities, the model is applied to study the biaxial behavior of the arterial wall and the aortic valve. The pressure–radius relationships of the arterial wall accurately describe experimentally observed sigma-shaped curves. In addition, the nonlinear and anisotropic mechanical properties of the aortic valve can be analyzed with the proposed model. We expect that the current model offers strong possibilities to further investigate the complex mechanical behavior of cardiovascular tissues, including their response to mechanical stimuli.
In Vitro Dynamic Strain Behavior of the Mitral Valve Posterior Leaflet
Authors: He Zhaoming , Ritchie Jennifer , Grashow Jonathan S. , Sacks Michael S. , Yoganathan Ajit P.
Published: May 2005

Knowledge of mitral valve (MV) mechanics is essential for the understanding of normal MV function, and the design and evaluation of new surgical repair procedures. In the present study, we extended our investigation of MV dynamic strain behavior to quantify the dynamic strain on the central region of the posterior leaflet. Native porcine MVs were mounted in an in-vitro physiologic flow loop. The papillary muscle (PM) positions were set to the normal, taut, and slack states to simulate physiological and pathological PM positions. Leaflet deformation was measured by tracking the displacements of 16 small markers placed in the central region of the posterior leaflet. Local leaflet tissue strain and strain rates were calculated from the measured displacements under dynamic loading conditions. A total of 18 mitral valves were studied. Our findings indicated the following: (1) There was a rapid rise in posterior leaflet strain during valve closure followed by a plateau where no additional strain (i.e., no creep) occurred. (2) The strain field was highly anisotropic with larger stretches and stretch rates in the radial direction. There were negligible stretches, or even compression (stretch<1) in the circumferential direction at the beginning of valve closure. (3) The areal strain curves were similar to the stretches in the trends. The posterior leaflet showed no significant differences in either peak stretches or stretch rates during valve closure between the normal, taut, and slack PM positions. (4) As compared with the anterior leaflet, the posterior leaflet demonstrated overall lower stretch rates in the normal PM position. However, the slack and taut PM positions did not demonstrate the significant difference in the stretch rates and areal strain rates between the posterior leaflet and the anterior leaflet. The MV posterior leaflet exhibited pronounced mechanically anisotropic behavior. Loading rates of the MV posterior leaflet were very high. The PM positions influenced neither peak stretch nor stretch rates in the central area of the posterior leaflet. The stretch rates and areal strain rates were significantly lower in the posterior leaflet than those measured in the anterior leaflet in the normal PM position. However, the slack and taut PM positions did not demonstrate the significant differences between the posterior leaflet and the anterior leaflet. We conclude that PM positions may influence the posterior strain in a different way as compared to the anterior leaflet.
In Vivo Muscle Stiffening Under Bone Compression Promotes Deep Pressure Sores
Authors: Gefen A. , Gefen N. , Linder-Ganz E. , Margulies S. S.
Published: May 2005

Pressure sores (PS) in deep muscles are potentially fatal and are considered one of the most costly complications in spinal cord injury patients. We hypothesize that continuous compression of the longissimus and gluteus muscles by the sacral and ischial bones during wheelchair sitting increases muscle stiffness around the bone-muscle interface over time, thereby causing muscles to bear intensified stresses in relentlessly widening regions, in a positive-feedback injury spiral. In this study, we measured long-term shear moduli of muscle tissue in vivo in rats after applying compression (35 KPa or 70 KPa for 1∕4–2 h, N=32), and evaluated tissue viability in matched groups (using phosphotungstic acid hematoxylin histology, N=10). We found significant (1.8-fold to 3.3-fold, p<0.05) stiffening of muscle tissue in vivo in muscles subjected to 35 KPa for 30 min or over, and in muscles subjected to 70 KPa for 15 min or over. By incorporating this effect into a finite element (FE) model of the buttocks of a wheelchair user we identified a mechanical stress wave which spreads from the bone-muscle interface outward through longissimus muscle tissue. After 4 h of FE simulated motionlessness, 50%–60% of the cross section of the longissimus was exposed to compressive stresses of 35 KPa or over (shown to induce cell death in rat muscle within 15 min). During these 4 h, the mean compressive stress across the transverse cross section of the longissimus increased by 30%–40%. The identification of the stiffening-stress-cell-death injury spiral developing during the initial 30 min of motionless sitting provides new mechanistic insight into deep PS formation and calls for reevaluation of the 1 h repositioning cycle recommended by the U.S. Department of Health.
Use of Virtual, Interactive, Musculoskeletal System (VIMS) in Modeling and Analysis of Shoulder Throwing Activity
Authors: Lin Hwai-Ting , Nakamura Yasuo , Su Fong-Chin , Hashimoto Jun , Nobuhara Katsuya , Chao Edmund Y. S.
Published: May 2005

Our purpose in this study was to apply the virtual, interactive, musculoskeletal system (VIMS) software for modeling and biomechanical analysis of the glenohumeral joint during a baseball pitching activity. The skeletal model was from VIMS library and muscle fiber attachment sites were derived from the visible human dataset. The muscular moment arms and function changes are mainly due to the large humeral motion involved during baseball pitching. The graphic animation of the anatomic system using VIMS software is an effective tool to model and visualize the complex anatomical structure of the shoulder for biomechanical analysis.
Evaluation of a Particle Swarm Algorithm For Biomechanical Optimization
Authors: Schutte Jaco F. , Koh Byung-Il , Reinbolt Jeffrey A. , Haftka Raphael T. , George Alan D. , Fregly Benjamin J.
Published: May 2005

Optimization is frequently employed in biomechanics research to solve system identification problems, predict human movement, or estimate muscle or other internal forces that cannot be measured directly. Unfortunately, biomechanical optimization problems often possess multiple local minima, making it difficult to find the best solution. Furthermore, convergence in gradient-based algorithms can be affected by scaling to account for design variables with different length scales or units. In this study we evaluate a recently- developed version of the particle swarm optimization (PSO) algorithm to address these problems. The algorithm’s global search capabilities were investigated using a suite of difficult analytical test problems, while its scale-independent nature was proven mathematically and verified using a biomechanical test problem. For comparison, all test problems were also solved with three off-the-shelf optimization algorithms—a global genetic algorithm (GA) and multistart gradient-based sequential quadratic programming (SQP) and quasi-Newton (BFGS) algorithms. For the analytical test problems, only the PSO algorithm was successful on the majority of the problems. When compared to previously published results for the same problems, PSO was more robust than a global simulated annealing algorithm but less robust than a different, more complex genetic algorithm. For the biomechanical test problem, only the PSO algorithm was insensitive to design variable scaling, with the GA algorithm being mildly sensitive and the SQP and BFGS algorithms being highly sensitive. The proposed PSO algorithm provides a new off-the-shelf global optimization option for difficult biomechanical problems, especially those utilizing design variables with different length scales or units.
Stress Distribution in a Circular Membrane With a Central Fixation
Authors: Mori Daisuke , David Guido , Humphrey Jay D. , Moore James E.
Published: May 2005

Clinical interventions can change the mechanical environment of the tissues targeted for therapy. In order to design better procedures, it is important to understand cellular responses to altered mechanical stress. Rigid fixation is one example of a constraint imposed on living tissues as a result of implanted devices. This results in disturbed stress and strain fields, with potentially strong gradients. Herein, we numerically solve the governing nonlinear ordinary differential equation for the stress distribution in a finitely deformed anisotropic circular membrane with a concentric fixation by applying a zero-displacement condition at the inner circumference. Results show that rigid fixations yield distributions of stress and strain that are markedly different from tissue defects with traction-free boundaries. Moreover, the material anisotropy plays a significant role in the manner the stress redistributes regardless of the size of fixation. The present study will contribute to the design of experiments to determine cellular reactions involved in the failure of interventional treatments.
Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise
Authors: Davis Curt H. , Li Yonghong , McConnell Joseph R. , Frey Markus M. , Hanna Edward
Published: May 2005

Satellite radar altimetry measurements indicate that the East Antarctic ice-sheet interior north of 81.6°S increased in mass by 45 ± 7 billion metric tons per year from 1992 to 2003. Comparisons with contemporaneous meteorological model snowfall estimates suggest that the gain in mass was associated with increased precipitation. A gain of this magnitude is enough to slow sea-level rise by 0.12 ± 0.02 millimeters per year.
Patient-Specific Embryonic Stem Cells Derived from Human SCNT Blastocysts
Authors: Hwang Woo Suk , Roh Sung Il , Lee Byeong Chun , Kang Sung Keun , Kwon Dae Kee , Kim Sue , Kim Sun Jong , Park Sun Woo , Kwon Hee Sun , Lee Chang Kyu , Lee Jung Bok , Kim Jin Mee , Ahn Curie , Paek Sun Ha , Chang Sang Sik , Koo Jung Jin , Yoon Hyun Soo , Hwang Jung Hye , Hwang Youn Young , Park Ye Soo , Oh Sun Kyung , Kim Hee Sun , Park Jong Hyuk , Moon Shin Yong , Schatten Gerald
Published: May 2005

Patient-specific, immune-matched human embryonic stem cells (hESCs) are anticipated to be of great biomedical importance for studies of disease and development and to advance clinical deliberations regarding stem cell transplantation. Eleven hESC lines were established by somatic cell nuclear transfer (SCNT) of skin cells from patients with disease or injury into donated oocytes. These lines, nuclear transfer (NT)âhESCs, grown on human feeders from the same NT donor or from genetically unrelated individuals, were established at high rates, regardless of NT donor sex or age. NT-hESCs were pluripotent, chromosomally normal, and matched the NT patient's DNA. The major histocompatibility complex identity of each NT-hESC when compared to the patient's own showed immunological compatibility, which is important for eventual transplantation. With the generation of these NT-hESCs, evaluations of genetic and epigenetic stability can be made. Additional work remains to be done regarding the development of reliable directed differentiation and the elimination of remaining animal components. Before clinical use of these cells can occur, preclinical evidence is required to prove that transplantation of differentiated NT-hESCs can be safe, effective, and tolerated.
tRNA Actively Shuttles Between the Nucleus and Cytosol in Yeast
Authors: Takano Akira , Endo Toshiya , Yoshihisa Tohru
Published: May 2005

Previous evidence suggested that transfer RNAs (tRNAs) cross the nuclear envelope to the cytosol only once after maturing in the nucleus. We now present evidence for nuclear import of tRNAs in yeast. Several export mutants accumulate mature tRNAs in the nucleus even in the absence of transcription. Import requires energy but not the Ran cycle. These results indicate that tRNAs shuttle between the nucleus and cytosol.
The Size and Duration of the Sumatra-Andaman Earthquake from Far-Field Static Offsets
Authors: Banerjee P. , Pollitz F. F. , Bürgmann R.
Published: May 2005

The 26 December 2004 Sumatra earthquake produced static offsets at continuously operating GPS stations at distances of up to 4500 kilometers from the epicenter. We used these displacements to model the earthquake and include consideration of the Earth's shape and depth-varying rigidity. The results imply that the average slip was >5 meters along the full length of the rupture, including the ∼650-kilometer-long Andaman segment. Comparison of the source derived from the far-field static offsets with seismically derived estimates suggests that 25 to 35% of the total moment release occurred at periods greater than 1 hour. Taking into consideration the strong dip dependence of moment estimates, the magnitude of the earthquake did not exceed
M
w
= 9.2.
Role of Sialic Acid and Complex Carbohydrate Biosynthesis in Biofilm Formation by Nontypeable
Haemophilus influenzae
in the Chinchilla Middle Ear
Authors: Jurcisek Joseph , Greiner Laura , Watanabe Hiroshi , Zaleski Anthony , Apicella Michael A. , Bakaletz Lauren O.
Published: May 2005

Nontypeable
Haemophilus influenzae
(NTHI) is an important pathogen in respiratory tract infections, including otitis media (OM). NTHI forms biofilms in vitro as well as in the chinchilla middle ear, suggesting that biofilm formation in vivo might play an important role in the pathogenesis and chronicity of OM. We've previously shown that SiaA, SiaB, and WecA are involved in biofilm production by NTHI in vitro. To investigate whether these gene products were also involved in biofilm production in vivo, NTHI strain 2019 and five isogenic mutants with deletions in genes involved in carbohydrate biosynthesis were inoculated into the middle ears of chinchillas. The wild-type strain formed a large, well-organized, and viable biofilm; however, the
wecA
,
lsgB
,
siaA
,
pgm
, and
siaB
mutants were either unable to form biofilms or formed biofilms of markedly reduced mass, organization, and viability. Despite their compromised ability to form a biofilm in vivo,
wecA
,
lsgB
, and
siaA
mutants survived in the chinchilla, inducing culture-positive middle ear effusions, whereas
pgm
and
siaB
mutants were extremely sensitive to the bactericidal activity of chinchilla serum and thus did not survive. Lectin analysis indicated that sialic acid was an important component of the NTHI 2019 biofilm produced in vivo. Our data suggested that genes involved in carbohydrate biosynthesis and assembly play an important role in the ability of NTHI to form a biofilm in vivo. Collectively, we found that when modeled in a mammalian host, whereas biofilm formation was not essential for survivability of NTHI in vivo, lipooligosaccharide sialylation was indispensable.
Salmonella entericaSerovar Typhimurium Pathogenicity Island 2 Is Necessary for Complete Virulence in a Mouse Model of Infectious Enterocolitis
Authors: Coburn Bryan , Li Yuling , Owen David , Vallance Bruce A. , Finlay B. Brett
Published: May 2005

Salmonellaspecies cause a wide range of disease in multiple hosts.Salmonella entericaserovar Typhimurium causes self-limited intestinal disease in humans and systemic typhoid-like illness in susceptible mice. The prevailing dogma in murineS. entericaserovar Typhimurium pathogenesis is that distinct virulence mechanisms—Salmonellapathogenicity islands 1 and 2 (SPI1 and SPI2)—perform distinct roles in pathogenesis, the former being important for invasion and intestinal disease and the latter important for intracellular survival and systemic persistence and disease. Although evidence from bovine infections has suggested that SPI2 has a role in ileal disease, there is no evidence that SPI2 is important for inflammation in a disease that more closely recapitulates human colitis. UsingS. entericaserovar Typhimurium strains that lack functional type III secretion systems, we demonstrate that SPI2 is essential for complete virulence in murine infectious enterocolitis. Using a recently characterized murine model (M. Barthel,S. Hapfelmeier, L. Quintanilla-Martinez, M. Kremer, M. Rohde, M. Hogardt, K. Pfeffer, H. Russmann, and W. D. Hardt, Infect. Immun.71:2839-2858, 2003), we demonstrate that SPI1 mutants are unable to cause intestinal disease 48 h after infection and that SPI2-deficient bacteria also cause significantly attenuated typhlitis. We show that at the peak of inflammation in the cecum, SPI2 mutants induce diminished intercellular adhesion molecule 1 expression and neutrophil recruitment but that wild-type and mutantSalmonellaare similarly distributed in the lumen of the infected organ. Finally, we demonstrate that attenuation of intestinal inflammation is accompanied by resolution of typhlitis in the mutant, but not wild-type, infections. Collectively, these results indicate that SPI2 is needed for enterocolitis, as well as for systemic disease.
Comparison of
Salmonella
enterica
Serovar Typhimurium Colitis in Germfree Mice and Mice Pretreated with Streptomycin
Authors: Stecher Bärbel , Macpherson Andrew J. , Hapfelmeier Siegfried , Kremer Marcus , Stallmach Thomas , Hardt Wolf-Dietrich
Published: May 2005

Salmonella enterica
subspecies 1 serovar Typhimurium is a common cause of bacterial enterocolitis. Mice are generally protected from
Salmonella
serovar Typhimurium colonization and enterocolitis by their resident intestinal microflora. This phenomenon is called “colonization resistance” (CR). Two murine
Salmonella
serovar Typhimurium infection models are based on the neutralization of CR: (i) in specific-pathogen-free mice pretreated with streptomycin (StrSPF mice) antibiotics disrupt the intestinal microflora; and (ii) germfree (GF) mice are raised without any intestinal microflora, but their intestines show distinct physiologic and immunologic characteristics. It has been unclear whether the same pathogenetic mechanisms trigger
Salmonella
serovar Typhimurium colitis in GF and StrSPF mice. In this study, we compared the two colitis models. In both of the models
Salmonella
serovar Typhimurium efficiently colonized the large intestine and triggered cecum and colon inflammation starting 8 h postinfection. The type III secretion system encoded in
Salmonella
pathogenicity island 1 was essential in both disease models. Thus,
Salmonella
serovar Typhimurium colitis is triggered by similar pathogenetic mechanisms in StrSPF and GF mice. This is remarkable considering the distinct physiological properties of the GF mouse gut. One obvious difference was more pronounced damage and reduced regenerative response of the cecal epithelium in GF mice. Overall, StrSPF mice and GF mice provide similar but not identical models for
Salmonella
serovar Typhimurium colitis.
β2 Integrins Control the Severity of Murine Lyme Carditis
Authors: Guerau-de-Arellano Mireia , Alroy Joseph , Huber Brigitte T.
Published: May 2005

Infection of C57BL/6 (B6) mice with the Lyme disease spirocheteBorrelia burgdorferican result in development of arthritis and carditis.B. burgdorferiinduces expression of β2/CD18 integrins, adhesion molecules that mediate the firm adhesion of leukocytes to the endothelium necessary for cellular extravasation during inflammation. The important role of β2/CD18 integrins during extravasation suggests that these molecules play a role in the development of Lyme arthritis and carditis. The dependency of these inflammatory processes on the β2 integrins was investigated in CD18 hypomorph mice, which express low levels of CD18. The results indicate that CD18 deficiency did not abrogate development of Lyme arthritis or carditis. Moreover, it resulted in increased severity of Lyme carditis.B. burgdorferi-infected CD18 hypomorph mice showed an increased macrophage infiltration of the heart, while they produced lower levels of borreliacidal anti-B. burgdorferiantibodies compared to wild-type mice. In accordance with these results, we demonstrate that dendritic cells from CD18 hypomorph mice secrete higher levels of monocyte/macrophage chemoattractant protein 1 (MCP-1/CCL2) in response toB. burgdorferi. Similarly, we show by real-time PCR thatB. burgdorferi-infected hearts from CD18 hypomorph mice express increased levels of MCP-1 RNA compared to wild-type mice. Overall, our results indicate that β2 integrin deficiency does not abrogateB. burgdorferi-induced inflammation; rather, it results in increased recruitment of macrophages into theB. burgdorferi-infected heart, likely due to the increased expression of MCP-1 in this tissue. Thus, β2 integrins may play a regulatory role inB. burgdorferi-induced inflammation beyond mediating adhesion of leukocytes to the endothelium.
Changes in Lipopolysaccharide O Antigen Distinguish Acute versus Chronic
Leptospira interrogans
Infections
Authors: Nally Jarlath E. , Chow Emilie , Fishbein Michael C. , Blanco David R. , Lovett Michael A.
Published: May 2005

Leptospirosis is the most geographically widespread zoonotic disease in the world. A severe pulmonary form of leptospirosis (SPFL) is being recognized with increased frequency. We have reported that human SPFL isolates of
Leptospira
cause acute lethal infection with prominent pulmonary hemorrhage in guinea pigs. We have found that the same SPFL strains cause asymptomatic infection and chronic renal shedding in rats, where infection is restricted to the renal tubules. To address the antigenic composition of host tissue-derived
Leptospira
(HTL), motile leptospires were purified from guinea pig liver by centrifugation on Percoll density gradients and compared to Percoll-purified in vitro-cultivated
Leptospira
(IVCL). The lipopolysaccharide O antigen (Oag) content of guinea pig liver-derived HTL was markedly reduced compared to that of IVCL, as demonstrated both by immunoblotting with a monoclonal antibody that was serovar specific for Oag and by periodate-silver staining. Confocal microscopy of HTL in guinea pig liver and kidney with the Oag-specific monoclonal antibody provided further evidence that diminution of the Oag content occurred in situ during lethal infection. In contrast, the Oag content of HTL in chronically infected rat renal tubules was indistinguishable from that of IVCL. These findings suggest that there may be regulation of Oag synthesis by
Leptospira
specific to the animal host infected. The hypothesis that the Oag content is related to whether lethal infection or chronic renal tubular colonization occurs remains to be tested.
Glucosyltransferases of Viridans Streptococci Are Modulins of Interleukin-6 Induction in Infective Endocarditis
Authors: Shun Chia-Tung , Lu Shih-Yu , Yeh Chiou-Yueh , Chiang Chung-Pin , Chia Jean-San , Chen Jen-Yang
Published: May 2005

The glucosyltransferases (GTFs) of viridans streptococci, common pathogens of infective endocarditis, are extracellular proteins that convert sucrose into exopolysaccharides and glucans. GTFs B, C, and D of
Streptococcus mutans
are modulins that induce, in vitro and in vivo, the production of cytokines, in particular interleukin-6 (IL-6), from monocytes. The roles of
S. mutans
GTFs in infectivity and inflammation in situ were tested in a rat experimental model of endocarditis. No significant differences in infectivity, in terms of 95% infective dose and densities of bacteria inside vegetations, were observed between laboratory strain GS-5 and two clinical isolates or isogenic mutant NHS1DD, defective in the expression of GTFs. In aortic valves and surrounding tissues, IL-6 was detected by Western blots and immunostaining 24 h after GS-5 infection, was maintained over 72 h, and was followed by production of tumor necrosis factor alpha but not IL-1β. Animals infected with NHS1DD showed markedly lower levels of IL-6 (less than 5% of that of parental GS-5-infected rats), while tumor necrosis factor alpha was unaffected. In contrast, animals infected with NHR1DD, another isogenic mutant expressing only GtfB, showed a much smaller reduction (down to 56%). These results suggest that GTFs are specific modulins that act during acute inflammation, inducing IL-6 from endothelial cells surrounding the infected valves without affecting bacterial colonization in vegetations, and that IL-6 might persist in chronic inflammation in endocarditis.
Direct Activation of Human Endothelial Cells by
Plasmodium falciparum
-Infected Erythrocytes
Authors: Viebig Nicola K. , Wulbrand Ulrich , Förster Reinhold , Andrews Katherine T. , Lanzer Michael , Knolle Percy A.
Published: May 2005

Cytoadherence of
Plasmodium falciparum
-infected erythrocytes (PRBC) to endothelial cells causes severe clinical disease, presumably as a of result perfusion failure and tissue hypoxia. Cytoadherence to endothelial cells is increased by endothelial cell activation, which is believed to occur in a paracrine fashion by mediators such as tumor necrosis factor alpha (TNF-α) released from macrophages that initially recognize PRBC. Here we provide evidence that PRBC directly stimulate human endothelial cells in the absence of macrophages, leading to increased expression of adhesion-promoting molecules, such as intercellular adhesion molecule 1. Endothelial cell stimulation by PRBC required direct physical contact for a short time (30 to 60 min) and was correlated with parasitemia. Gene expression profiling of endothelial cells stimulated by PRBC revealed increased expression levels of chemokine and adhesion molecule genes. PRBC-stimulated endothelial cells especially showed increased expression of molecules involved in parasite adhesion but failed to express molecules promoting leukocyte adhesion, such as E-selectin and vascular cell adhesion molecule 1, even after challenge with TNF-α. Collectively, our data suggest that stimulation of endothelial cells by PRBC may have two effects: prevention of parasite clearance through increased cytoadherence and attenuation of leukocyte binding to endothelial cells, thereby preventing deleterious immune reactivity.
p47 GTPases RegulateToxoplasma gondiiSurvival in Activated Macrophages
Authors: Butcher Barbara A. , Greene Robert I. , Henry Stanley C. , Annecharico Kimberly L. , Weinberg J. Brice , Denkers Eric Y. , Sher Alan , Taylor Gregory A.
Published: May 2005

The cytokine gamma interferon (IFN-γ) is critical for resistance toToxoplasma gondii. IFN-γ strongly activates macrophages and nonphagocytic host cells to limit intracellular growth ofT. gondii; however, the cellular factors that are required for this effect are largely unknown. We have shown previously that IGTP and LRG-47, members of the IFN-γ-regulated family of p47 GTPases, are required for resistance to acuteT. gondiiinfections in vivo. In contrast, IRG-47, another member of this family, is not required. In the present work, we addressed whether these GTPases are required for IFN-γ-induced suppression ofT. gondiigrowth in macrophages in vitro. Bone marrow macrophages that lacked IGTP or LRG-47 displayed greatly attenuated IFN-γ-induced inhibition ofT. gondiigrowth, while macrophages that lacked IRG-47 displayed normal inhibition. Thus, the ability of the p47 GTPases to limit acute infection in vivo correlated with their ability to suppress intracellular growth in macrophages in vitro. Using confocal microscopy and sucrose density fractionation, we demonstrated that IGTP largely colocalizes with endoplasmic reticulum markers, while LRG-47 was mainly restricted to the Golgi. Although both IGTP and LRG-47 localized to vacuoles containing latex beads, neither protein localized to vacuoles containing liveT. gondii. These results suggest that IGTP and LRG-47 are able to regulate host resistance to acuteT. gondiiinfections through their ability to inhibit parasite growth within the macrophage.
Immunohistological Characterization of Macrophage Migration Inhibitory Factor Expression inPlasmodium falciparum-Infected Placentas
Authors: Chaisavaneeyakorn Sujittra , Lucchi Naomi , Abramowsky Carlos , Othoro Caroline , Chaiyaroj Sansanee C. , Shi Ya Ping , Nahlen Bernard L. , Peterson David S. , Moore Julie M. , Udhayakumar Venkatachalam
Published: May 2005

Previously, we have shown that macrophage migration inhibitory factor (MIF) was highly elevated in the placental intervillous blood (IVB) ofPlasmodium falciparum-infected women. Here, we compared the expression of MIF in placental tissues obtained fromP. falciparum-infected and -uninfected women. Immunoperoxidase staining showed a consistent pattern of MIF expression in syncytiotrophoblasts, extravillous trophoblasts, IVB mononuclear cells, and amniotic epithelial cells, irrespective of their malaria infection status. Cytotrophoblast, villous stroma, and Hofbauer cells showed focal staining. Only amniotic epithelial and IVB mononuclear cells fromP. falciparum-infected placentas exhibited significantly higher level of MIF expression than uninfected placentas. Stimulation of syncytilized human trophoblast BeWo cells withP. falciparum-infected erythrocytes that were selected to bind these cells resulted in significant increases in MIF secretion, whereas control erythrocytes, lipopolysaccharides, and synthetic β-hematin had minimal effect. These findings suggest that placental malaria modulates MIF expression in different placental compartments.
An RNA Vaccine Based on Recombinant Semliki Forest Virus Particles Expressing the Cu,Zn Superoxide Dismutase Protein of
Brucella abortus
Induces Protective Immunity in BALB/c Mice
Authors: Oñate Angel A. , Donoso Gabriel , Moraga-Cid Gustavo , Folch Hugo , Céspedes Sandra , Andrews Edilia
Published: May 2005

We constructed infectious but replication-deficient Semliki Forest virus (SFV) particles carrying recombinant RNA encoding
Brucella abortus
Cu,Zn superoxide dismutase (SOD). The recombinant SFV particles (SFV-SOD particles) were then evaluated for their ability to induce a T-cell immune response and to protect BALB/c mice against a challenge with
B. abortus
2308. Intraperitoneal injection of mice with recombinant SFV-SOD particles did not lead to the induction of SOD-specific antibodies, at least until week 6 after immunization (the end of the experiment). In vitro stimulation of splenocytes from the vaccinated mice with either recombinant Cu,Zn SOD (rSOD) or crude
Brucella
protein resulted in a T-cell proliferative response and the induction of gamma interferon secretion but not interleukin-4. In addition, the splenocytes exhibited significant levels of cytotoxic T-lymphocyte activity against
Brucella
-infected cells. The SFV-SOD particles, but not the control virus particles, induced a significant level of protection in BALB/c mice against challenge with
B. abortus
virulent strain 2308. These findings indicated that an SFV-based vector carrying the SOD gene has potential for use as a vaccine to induce resistance against
B. abortus
infections.
Skin Test Performed with Highly PurifiedMycobacterium tuberculosisRecombinant Protein Triggers Tuberculin Shock in Infected Guinea Pigs
Authors: Reece Stephen T. , Stride Nicole , Ovendale Pamela , Reed Steven G. , Campos-Neto Antonio
Published: May 2005

Tuberculin shock due to inoculation ofMycobacterium tuberculosisantigens in patients with tuberculosis is a serious syndrome originally described over 100 years ago by Robert Koch. Here, we present experimental evidence that a singleM. tuberculosisrecombinant protein, CFP-10, triggers this syndrome. Intradermal inoculation of CFP-10 elicits inM. tuberculosis-infected mice high levels of serum tumor necrosis factor alpha and causes tuberculin shock in infected guinea pigs characterized by hypothermia and death within 6 to 48 h after the antigen inoculation. Autopsies of these animals revealed intense polycythemia and hemorrhagic patches in the lung parenchyma, a pathological observation consistent with tuberculin shock. These results point to the possible occurrence of tuberculin shock in sensitive individuals inoculated with highly purifiedM. tuberculosisrecombinant proteins as vaccine candidates or skin test reagents.
A Newly Discovered Mycobacterial Pathogen Isolated from Laboratory Colonies of
Xenopus
Species with Lethal Infections Produces a Novel Form of Mycolactone, the
Mycobacterium ulcerans
Macrolide Toxin
Authors: Mve-Obiang Armand , Lee Richard E. , Umstot Edward S. , Trott Kristin A. , Grammer Timothy C. , Parker John M. , Ranger Brian S. , Grainger Robert , Mahrous Engu A. , Small P. L. C.
Published: May 2005

Mycobacterium ulcerans
, the causative agent of Buruli ulcer, produces a macrolide toxin, mycolactone A/B, which is thought to play a major role in virulence. A disease similar to Buruli ulcer recently appeared in United States frog colonies following importation of the West African frog,
Xenopus tropicalis
. The taxonomic position of the frog pathogen has not been fully elucidated, but this organism, tentatively designated
Mycobacterium liflandii
, is closely related to
M. ulcerans
and
Mycobacterium marinum
, and as further evidence is gathered, it will most likely be considered a subspecies of one of these species. In this paper we show that
M. liflandii
produces a novel plasmid-encoded mycolactone, mycolactone E.
M. liflandii
contains all of the genes in the mycolactone cluster with the exception of that encoding CYP140A2, a putative p450 monooxygenase. Although the core lactone structure is conserved in mycolactone E, the fatty acid side chain differs from that of mycolactone A/B in the number of hydroxyl groups and double bonds. The cytopathic phenotype of mycolactone E is identical to that of mycolactone A/B, although it is less potent. To further characterize the relationship between
M. liflandii
and
M. ulcerans
, strains were analyzed for the presence of the RD1 region genes,
esxA
(ESAT-6) and
esxB
(CFP-10). The
M. ulcerans
genome strain has a deletion in RD1 and lacks these genes. The results of these studies show that
M. liflandii
contains both
esxA
and
esxB
.
Immunoglobulin-Regulated Expression ofBorrelia burgdorferiOuter Surface Protein A In Vivo
Authors: Hodzic Emir , Tunev Stefan , Feng Sunlian , Freet Kim J. , Barthold Stephen W.
Published: May 2005

Borrelia burgdorferi, the agent of Lyme disease, down-regulates outer surface protein A (OspA), which is abundantly expressed in ticks, during infection of the mammalian host. In this study we examined the signals that may be responsible for maintaining the OspA-negative state of spirochetes during infection. Transcription ofospAmRNA was found in tissues of C3H-severe combined immunodeficient (C3H-scid) mice, but not immunocompetent C3H mice, inoculated with culturedB. burgdorferi, tick-borne spirochetes, and host-adapted spirochetes. Transcription was more frequent at 4 weeks than at 1 week. Transcription was present at the host-tick interface as early as 24 h after tick attachment but declined at 48 and 72 h. Thus,ospAmRNA transcription in distant tissues and at later times in C3H-scidmice is probably due to up-regulation during infection. Adoptive lymphocyte transfer from naïve C3H mice to infected C3H-scidmice resulted in OspA seroconversion, confirming OspA expression in the host. Passive transfer of normal mouse serum, immunoglobulin M (IgM) from normal mouse serum, or IgG from normal mouse serum into infected C3H-scidmice resulted in down-regulation ofospA, but transfer of normal mouse serum depleted of immunoglobulin did not influenceospAmRNA transcription. Collectively, our results indicate thatospAmRNA transcription in the host is regulated by nonspecific immunoglobulin, which may be a natural antibody.
Nitric Oxide Detoxification Systems Enhance Survival of
Neisseria meningitidis
in Human Macrophages and in Nasopharyngeal Mucosa
Authors: Stevanin TÂnia M. , Moir James W. B. , Read Robert C.
Published: May 2005

Nitric oxide (NO) contributes to mammalian host defense by direct microbicidal activity and as a signaling molecule of innate immune responses. Macrophages produce NO via the inducible NO synthase (iNOS). The genome of
Neisseria meningitidis
includes two genes,
norB
(encoding nitric oxide reductase) and
cycP
(encoding cytochrome
c′
), both of which detoxify NO in pure cultures of
N. meningitidis
. We show here that
norB
, and to a lesser extent
cycP
, enhance survival of
N. meningitidis
within primary human macrophages. Furthermore, accumulation of lysosome-associated membrane protein 1 (LAMP-1) is modified in phagosomes containing an isogenic
norB
mutant of
N. meningitidis
compared to the wild type. The survival enhancement conferred by
norB
and
cycP
is ablated by pretreatment of macrophages with the nitric oxide synthase inhibitor
N
(G)-monomethyl-
l
-arginine (L-NMMA). Despite this evidence that NO detoxification confers advantage, we find, using a highly sensitive chemiluminescence technique, that human macrophage-associated [NO] is low even after activation by lipopolysaccharide and interferon alpha. Furthermore, wild-type
N. meningitidis
further depletes cell-associated NO during phagocytosis by an active mechanism and survives relatively poorly in the presence of L-NMMA, suggesting that the wild-type organism may utilize NO for optimal survival during intracellular life. The natural habitat of
N. meningitidis
is the human nasopharynx. Using a nasopharyngeal mucosa organ culture system, we show that mutants lacking
norB
and
cycP
also survive poorly in nasopharyngeal tissue compared to wild-type
N. meningitidis
. These findings indicate that the meningococcus requires active NO detoxification systems for optimal survival during experimental nasopharyngeal colonization and processing by human phagocytic cells.
Common and Unique Gene Expression Signatures of Human Macrophages in Response to Four Strains ofMycobacterium aviumThat Differ in Their Growth and Persistence Characteristics
Authors: Blumenthal Antje , Lauber Jörg , Hoffmann Reinhard , Ernst Martin , Keller Christine , Buer Jan , Ehlers Stefan , Reiling Norbert
Published: May 2005

Classification of pathogenic species according to the distinct host transcriptional responses that they elicit may become a relevant tool for microarray-based diagnosis of infection. Individual strains ofMycobacterium avium, an opportunistic pathogen in humans, have previously been shown to differ in terms of growth and persistence. In order to cover a wide spectrum of virulence, we selected fourM. aviumisolates (2151SmO, 2151SmT, SE01, TMC724) that have distinct intramacrophage replication characteristics and cause differential activation in human macrophages. Following infection with each of these strains, the expression of 12,558 genes in human macrophages was systematically analyzed by microarray technology. Fifty genes (including genes encoding proinflammatory cytokines, chemokines, signaling, and adhesion molecules) were differentially expressed more than twofold in response to all of theM. aviumisolates investigated and therefore constitute a common macrophage signature in response toM. avium. The magnitude of regulation of most of these genes was directly correlated with the host cell-activating capacity of the particularM. aviumstrain. The regulation of a number of genes not previously associated with mycobacterial infections was apparent; these genes included genes encoding lymphocyte antigen 64 and myosin X. In addition, individual response patterns typical for someM. aviumisolates could be defined by the pronounced upregulation of interleukin-12p40 (IL-12p40) (in the case of 2151SmO) or the specific upregulation of SOCS-1 and IL-10 (in the case of SE01) in macrophages. TMC724, a strain of avian origin, could not be classified by any one of these schemes, possibly indicating the limits of pathogen categorization solely by immune response signatures.
The SrtA Sortase of
Streptococcus agalactiae
Is Required for Cell Wall Anchoring of Proteins Containing the LPXTG Motif, for Adhesion to Epithelial Cells, and for Colonization of the Mouse Intestine
Authors: Lalioui Lila , Pellegrini Elisabeth , Dramsi Shaynoor , Baptista Marina , Bourgeois Nadege , Doucet-Populaire Florence , Rusniok Christophe , Zouine Mohamed , Glaser Philippe , Kunst Frank , Poyart Claire , Trieu-Cuot Patrick
Published: May 2005

Streptococcus agalactiae
(group B streptococcus [GBS]) is the leading cause of neonatal pneumonia, sepsis, and meningitis. An in silico genome analysis indicated that GBS strain NEM316 encodes 35 proteins containing an LPXTG motif which are thought to be covalently linked to the peptidoglycan by an enzyme called sortase. The role of these cell wall-anchored proteins in GBS pathogenesis was evaluated on a global level by inactivating the
srtA
gene. This gene encodes the major sortase SrtA that anchors most of the LPXTG-containing proteins. We chose the C5a peptidase (ScpB) and Alp2, an abundant immunogenic protein, as prototypical LPXTG-containing proteins. As expected, the SrtA knockout mutant was unable to anchor the C5a peptidase (ScpB) and Alp2 to the cell wall. Complementation with plasmid-borne
srtA
inserted into the chromosome restored the correct surface localization of both ScpB and Alp2. Interestingly, the SrtA mutant was impaired for binding to the major extracellular matrix components fibronectin and fibrinogen and displayed a significant reduction in adherence to human (A549, HeLa, and Caco-2) and murine (L2) epithelial cells compared to the parental wild-type strain. Surprisingly, the inactivation of
srtA
had no effect on the virulence of the type III strain of GBS in a neonatal rat model (measured by the 50% lethal dose and lung colonization) but strongly impaired the capacity of the strain to colonize the intestines of gnotobiotic mice in a competition assay. These results demonstrate that LPXTG-containing proteins are involved in cell adhesion and GBS persistence in vivo.
Inactivation of
Streptococcus
gordonii
SspAB Alters Expression of Multiple Adhesin Genes
Authors: Zhang Yongshu , Lei Yu , Nobbs Angela , Khammanivong Ali , Herzberg Mark C.
Published: May 2005

SspA and SspB (antigen I/II family proteins) can bind
Streptococcus
gordonii
to other oral bacteria and also to salivary agglutinin glycoprotein, a constituent of the salivary film or pellicle that coats the tooth. To learn if SspA and SspB are essential for adhesion and initial biofilm formation on teeth,
S. gordonii
DL1 was incubated with saliva-coated hydroxyapatite (sHA) for 2 h in Todd-Hewitt broth with 20% saliva to develop initial biofilms. Sessile cells attached to sHA, surrounding planktonic cells, and free-growing cells were recovered separately. Free-growing cells expressed more
sspA
-specific mRNA and
sspB
-specific mRNA than sessile cells. Free-growing cells expressed the same levels of
sspA
and
sspB
as planktonic cells. Surprisingly, an SspA
−
SspB
−
mutant strain showed 2.2-fold greater biofilm formation on sHA than wild-type
S. gordonii
DL1. To explain this observation, we tested the hypothesis that inactivation of
sspA
and
sspB
genes altered the expression of other adhesin genes during initial biofilm formation in vitro. When compared to wild-type cells, expression of
scaA
and
abpB
was significantly up-regulated in the SspA
−
SspB
−
strain in sessile, planktonic, and free-growing cells. Consistent with this finding, ScaA antigen was also overexpressed in planktonic and free-growing SspA
−
SspB
−
cells compared to the wild type. SspA/B adhesins, therefore, were strongly suggested to be involved in the regulation of multiple adhesin genes.