bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of Barometric Pressure Effects and Earth Tides from Observed Water Levels
Authors: Toll Nathanial J. , Rasmussen Todd C.
Published: October 2006

The effects of barometric pressure and earth tide changes are often observed in ground water level measurements. These disturbances can make aquifer test interpretation difficult by masking the small changes induced by aquifer testing at late times and great distances. A computer utility is now available that automatically removes the effects of barometric pressure and earth tides from water level observations using regression deconvolution. This procedure has been shown to remove more noise then traditional constant barometric efficiency techniques in both confined and unconfined aquifers. Instead of a single, instantaneous barometric efficiency, the procedure more correctly accounts for the lagged responses caused by barometric pressure and earth tide changes. Simultaneous measurements of water levels (or total heads) and nearby barometric pressures are required. As an additional option, the effects of earth tides can also be removed using theoretical earth tides. The program is demonstrated for two data sets collected at the Waste Isolation Pilot Plant, Carlsbad, New Mexico. The program is available free by request at http://www.hydrology.uga.edu/tools.html.
NMDA receptors trigger neurosecretion of 5‐HT within dorsal raphé nucleus of the rat in the absence of action potential firing
Authors: De Kock C. P. J. , Cornelisse L. N. , Burnashev N. , Lodder J. C. , Timmerman A. J. , Couey J. J. , Mansvelder H. D. , Brussaard A. B.
Published: October 2006

Activity and calcium‐dependent release of neurotransmitters from the somatodendritic compartment is an important signalling mechanism between neurones throughout the brain. NMDA receptors and vesicles filled with neurotransmitters occur in close proximity in many brain areas. It is unknown whether calcium influx through these receptors can trigger the release of somatodendritic vesicles directly, or whether postsynaptic action potential firing is necessary for release of these vesicles. Here we addressed this question by studying local release of serotonin (5‐HT) from dorsal raphé nucleus (DRN) neurones. We performed capacitance measurements to monitor the secretion of vesicles in giant soma patches, in response to short depolarizations and action potential waveforms. Amperometric measurements confirmed that secreted vesicles contained 5‐HT. Surprisingly, two‐photon imaging of DRN neurones in slices revealed that dendritic calcium concentration changes in response to somatic firing were restricted to proximal dendritic areas. This implied that alternative calcium entry pathways may dominate the induction of vesicle secretion from distal dendrites. In line with this, transient NMDA receptor activation, in the absence of action potential firing, was sufficient to induce capacitance changes. By monitoring GABAergic transmission onto DRN 5‐HT neurones in slices, we show that endogenous NMDA receptor activation, in the absence of postsynaptic firing, induced release of 5‐HT, which in turn increased the frequency of GABAergic inputs through activation of 5‐HT2receptors. We propose here that calcium influx through NMDA receptors can directly induce postsynaptic 5‐HT release from DRN neurones, which in turn may facilitate GABAergic input onto these cells.
Ca2+ release‐dependent hyperpolarizations modulate the firing pattern of juvenile GABA neurons in mouse substantia nigra pars reticulata in vitro
Authors: Yanovsky Yevgenij , Velte Simone , Misgeld Ulrich
Published: October 2006

A phasic activation of small‐conductance Ca2+‐dependent K+ channels (SK channels) underlies spike‐afterhyperpolarizations and spike‐independent, transient hyperpolarizations in juvenile substantia nigra neurons. Outward current pulses that cause the spike‐independent hyperpolarizations result from ryanodine receptor‐mediated Ca2+ release from intracellular stores. To study the modulation of excitability by the outward current pulses, we recorded from GABAergic pars reticulata neurons of mice at postnatal days 12–16. We induced a prolongation of SK channel open states by 1‐ethyl‐2‐benzimidazolinone (1‐EBIO). In addition to a prolongation of spike‐afterhyperpolarizations, 1‐EBIO (200 μm) potentiated outward current pulses by increasing their duration. Neurons were manipulated by current injection to display continuous or discontinuous discharge. Despite the prolongation of the outward current pulses by 1‐EBIO, continuous action potential discharge became more regular, although its frequency declined. Durations of silent periods (periods of >2× average interspike interval) increased. Caffeine (1 mm) further increased the duration of such silent periods. Caffeine, however, had no effect at short interspike intervals (<600 ms). Cyclopiazonic acid (10 μm) silenced discharge in 1‐EBIO, but discharge reappeared with the depletion of Ca2+ stores. We conclude that the modulation of excitability by an activation of SK channels through ryanodine receptor‐mediated release of Ca2+ critically depends on the frequency of discharge. Outward current pulses occur only if interspike intervals exceed the duration of spike‐afterhyperpolarizations. In this instance, the phasic, spike‐independent activation of SK channels supports pauses to interrupt autonomous discharge in juvenile GABAergic pars reticulata neurons.
High‐fat diet‐induced hepatic steatosis reduces glucagon receptor content in rat hepatocytes: potential interaction with acute exercise
Authors: Charbonneau Alexandre , Unson Cecilia G. , Lavoie Jean‐Marc
Published: October 2006

Studies have revealed that high‐fat (HF) diets promote hyperglycaemia, whole‐body insulin resistance and non‐alcoholic fatty liver disease (NAFLD). Recently, hepatic glucagon resistance has been shown to occur in rats fed a HF diet. More precisely, diet‐induced obesity (DIO) reduces the number of hepatic plasma membrane glucagon receptors (GR), which results in a diminished response to glucagon during a hyperglucagonaemic clamp. The present study was undertaken to test the hypothesis that a HF‐DIO is associated with a desensitization and destruction of the hepatic GR. We also hypothesized that a single bout of endurance exercise would modify the GR cellular distribution under our DIO model. Male rats were either fed a standard (SD) or a HF diet for two weeks. Each group was subdivided into a non‐exercised (Rest) and an acute exercised (EX) group. The HF diet resulted in a reduction of total hepatic GR (55%) and hepatic plasma membrane GR protein content (20%). These changes were accompanied by a significant increase in endosomal and lysosomal GR content with the feeding of a HF diet. The reduction of GR plasma membrane as well as the increase in endosomal GR was strongly correlated with an increase of PKC‐α, suggesting a role of PKC‐α in GR desensitization. EX increased significantly PKC‐α protein content in both diets, suggesting a role of PKC‐α in EX‐induced GR desensitization. The present results suggest that liver lipid infiltration plays a role in reducing glucagon action in the liver through a reduction in total cellular and plasma membrane GR content. Furthermore, the GR desensitization observed in our in vivo model of HF diet‐induced hepatic steatosis and in EX individuals may be regulated by PKC‐α.
A New Stall-Onset Criterion for Low Speed Dynamic-Stall
Authors: Sheng W. , Galbraith R. A. McD. , Coton F. N.
Published: October 2006

The Beddoes/Leishman dynamic-stall model has become one of the most popular for the provision of unsteady aerofoil data embedded in much larger codes. The underlying modeling philosophy was that it should be based on the best understanding, or description, of the associated physical phenomena. Even though the model was guided by the flow physics, it requires significant empirical inputs in the form of measured coefficients and constants. Beddoes provided these for a Mach number range of 0.3–0.8. This paper considers one such input for a Mach number of 0.12, where, from the Glasgow data, it is shown that the current stall-onset criterion, and subsequent adjustments, yield problematic results. A new stall criterion is proposed and developed in the best traditions of the model. It is shown to be very capable of reconstructing the Glasgow’s data for stall onset both the ramp-up and oscillatory tests.
Individual Blade Pitch Control for the Controls Advanced Research Turbine (CART)
Authors: Stol Karl A. , Zhao Wenxin , Wright Alan D.
Published: October 2006

Pitching the individual blades of a horizontal-axis wind turbine allows control of asymmetric aerodynamic loads, which in turn influences structural loads in the nonrotating frame such as tower side-side bending. These loads are not easily controlled by traditional collective pitch algorithms. This paper presents the design of individual pitch control systems for implementation on the Controls Advanced Research Turbine (CART) in Colorado to verify controller performance for load attenuation. The control designs are based on linear time-periodic state-space models of the turbine and use optimal control methods for gain calculation. Comparisons are made between new individual pitch, new collective pitch, and baseline controller performance in both above rated and below rated wind conditions. Results from simulations show the potential of individual pitch to reduce tower side-side fatigue damage in above rated wind speeds (by 70% compared to baseline control) but with no improvement over collective pitch in below rated wind speeds. Fatigue load reductions in tower fore-aft, shaft torsion, and blade flap are also observed. From 13h of field testing, both collective and individual pitch controllers achieve a reduction in fatigue damage. However, the superior performance of individual pitch control observed in simulation was not verified by the field test results.
Active Flow Control in Circular and Transitioning S-duct Diffusers
Authors: Pradeep A. M. , Sullerey R. K.
Published: October 2006

Performance enhancement of three-dimensional S-duct diffusers by secondary flow and separation control using vortex generator jets is the objective of the current experimental investigation. Two different diffuser geometries namely, a circular diffuser and a rectangular—to—circular transitioning diffuser were studied. The experiments were performed in uniform inflow conditions at a Reynolds number of 7.8×105 and the performance evaluation of the diffusers was carried out in terms of static pressure recovery and quality (flow uniformity) of the exit flow. Detailed measurements that included total pressure, velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken and these results are presented here in terms of static pressure rise, distortion coefficient, total pressure loss coefficient, and the transverse velocity vectors at the duct exit. The use of vortex generator jets resulted in around 26% in total pressure loss and about 22% decrease in flow distortion coefficients in the circular and transitioning diffusers. The mass flow rate of the air injected through the VGJ was about 0.1% of the mass flow rate of the main flow for secondary flow control and about 0.06% of the main flow for separation control. The physical mechanism of the flow control devices used has been explored. The structure of the vortices generated by the control methods are presented in the form of smoke visualization images. The method of flow control used here is perceived to have applications in turbomachinery like turbines and compressors.
A Finite-volume Approach for Simulation of Liquid-column Separation in Pipelines
Authors: Chaiko Mark A.
Published: October 2006

A finite-volume approach, based on the MUSCL-Hancock method, is presented and applied to liquid-column separation transients in pipelines. In the mathematical model, sudden closure of a valve on the downstream end of a pipeline initiates the hydraulic transient, while a head tank maintains constant upstream pressure. The two-phase fluid is treated as a homogeneous mixture, and changes in fluid pressure are assumed to occur at constant entropy. Effects of pipe elasticity on wave propagation speed are included in the model by coupling the circumferential stress-strain relation for the pipe wall to the local fluid pressure. In regions of the domain where the solution is smooth, second-order accuracy is achieved by means of data reconstruction based on sloping-difference formulas. Slope limiting prevents the development of spurious oscillations in the neighborhood of steep wave fronts. Data reconstruction leads to a piece-wise linear representation of the solution, which is discontinuous across cell boundaries. In order to advance the solution in time, a Riemann problem is solved on each cell junction to obtain mass and momentum flux contributions. A splitting technique, which separates flux terms from gravity and frictional effects, allows the compatibility equations for the Riemann problem to be expressed as total differentials of fluid velocity and an integral that depends only on the fluid pressure. Predictions for large-amplitude pressure pulses caused by liquid-column separation and rejoining are compared against experimental data available in the literature. Amplitude and timing of the predicted pressure response shows reasonably good agreement with experimental data even when as few as 20–40 computational cells are used to describe axial variations in fluid conditions along a pipeline of approximately 35m in length. An advantage of the current method is that it does not give rise to spurious oscillations when grid refinement is performed. The presence of nonphysical oscillations has been a drawback of a commonly used method based on discrete vapor cavities and characteristic treatment of wave propagation.
A Computational and Experimental Investigation of the Human Thermal Plume
Authors: Craven Brent A. , Settles Gary S.
Published: October 2006

The behavior of the buoyant plume of air shed by a human being in an indoor environment is important to room ventilation requirements, airborne disease spread, air pollution control, indoor air quality, and the thermal comfort of building occupants. It also becomes a critical factor in special environments like surgery rooms and clean-rooms. Of the previous human thermal plume studies, few have used actual human volunteers, made quantitative plume velocity measurements, or considered thermal stratification of the environment. Here, a study of the human thermal plume in a standard room environment, including moderate thermal stratification, is presented. We characterize the velocity field around a human volunteer in a temperature-stratified room using particle image velocimetry (PIV). These results are then compared to those obtained from a steady three-dimensional computational fluid dynamics (CFD) solution of the Reynolds-averaged Navier-Stokes equations (RANS) using the RNG k‐ε two-equation turbulence model. Although the CFD simulation employs a highly simplified model of the human form, it nonetheless compares quite well with the PIV data in terms of the plume centerline velocity distribution, velocity profiles, and flow rates. The effect of thermal room stratification on the human plume is examined by comparing the stratified results with those of an additional CFD plume simulation in a uniform-temperature room. The resulting centerline velocity distribution and plume flow rates are presented. The reduction in plume buoyancy produced by room temperature stratification has a significant effect on plume behavior.
Experimental Investigation of the Flow Distribution Inside a Tubular Heat Exchanger
Authors: Faure Thierry M. , Lusseyran François , Gougat Pierre , Launay François
Published: October 2006

The velocity field inside a new concept of heat exchanger, which is a component of a high protons linear accelerator, is investigated experimentally in order to validate the design. A full scale facility with optical accesses is used for the measurements by particle image velocimetry. The choice of the technique is set by the three-dimensional and strongly unsteady structure of the flow. A filtering procedure is applied to the recorded images before processing the velocity field with an optical flow algorithm using dynamical programming. The distribution of the velocity between the different tubes of the heat exchanger shows a large scatter of flow rate between these tubes. In addition, the turbulence characteristics are presented.
Characterization of the Nonaerated Flow Region in a Stepped Spillway by PIV
Authors: Amador António , Sánchez-Juny Martí , Dolz Josep
Published: October 2006

The development of the roller-compacted concrete (RCC) as a technique of constructing dams and the stepped surface that results from the construction procedure opened a renewed interest in stepped spillways. Previous research has focused on studying the air-water flow down the stepped chute with the objective of obtaining better design guidelines. The nonaerated flow region enlarges as the flow rate increases, and there is a lack of knowledge on the hydraulic performance of stepped spillways at high velocities that undermines its use in fear of cavitation damage. In the present, study the developing flow region in a stepped channel with a slope 1v:0.8h is characterized using a particle image velocimetry technique. An expression for the growth of the boundary layer thickness is proposed based on the streamwise distance from the channel crest and the roughness height. The local flow resistance coefficient is calculated by application of the von Kármán integral momentum equation. The shear strain, vorticity, and swirling strength maps obtained from the mean velocity gradient tensor are presented. Also, the fluctuating velocity field is assessed. The turbulent kinetic energy map indicates the region near the pseudobottom (imaginary line joining two adjacent step edges) as the most active in terms of Reynolds stresses. The turbulence was found to be very intense with maximum levels of turbulence intensity from 0.40 to 0.65 measured near the pseudobottom. Finally, the quadrant analysis of the velocity fluctuations suggests the presence of strong outflows of fluid from the cavities as well as inflows into the cavities. It is conjectured that the mass transfer/exchange between cavities and main stream, play an important role in the high levels of turbulent energy observed.
Porphyromonas gingivalis galEIs Involved in Lipopolysaccharide O-Antigen Synthesis and Biofilm Formation
Authors: Nakao Ryoma , Senpuku Hidenobu , Watanabe Haruo
Published: October 2006

Porphyromonas gingivalisis a crucial component of complex plaque biofilms that form in the oral cavity, resulting in the progression of periodontal disease. To elucidate the mechanism of periodontal biofilm formation, we analyzed the involvement of several genes related to the synthesis of polysaccharides inP. gingivalis. Gene knockoutP. gingivalismutants were constructed by insertion of anermF-ermAMcassette; among these mutants, thegalEmutant showed some characteristic phenotypes involved in the loss of GalE activity. As expected, thegalEmutant accumulated intracellular carbohydrates in the presence of 0.1% galactose and did not grow in the presence of galactose at a concentration greater than 1%, in contrast to the parental strain. Lipopolysaccharide (LPS) analysis indicated that the length of the O-antigen chain of thegalEmutant was shorter than that of the wild type. It was also demonstrated that biofilms generated by thegalEmutant had an intensity 4.5-fold greater than those of the wild type. Further, thegalEmutant was found to be significantly susceptible to some antibiotics in comparison with the wild type. In addition, complementation of thegalEmutation led to a partial recovery of the parental phenotypes. We concluded that thegalEgene plays a pivotal role in the modification of LPS O antigen and biofilm formation inP. gingivalisand considered that our findings of a relationship between the function of theP. gingivalis galEgene and virulence phenotypes such as biofilm formation may provide clues for understanding the mechanism of pathogenicity in periodontal disease.
A Newly Identified Leptospiral Adhesin Mediates Attachment to Laminin
Authors: Barbosa Angela S. , Abreu Patricia A. E. , Neves Fernanda O. , Atzingen Marina V. , Watanabe Mônica M. , Vieira Mônica L. , Morais Zenaide M. , Vasconcellos Sílvio A. , Nascimento Ana L. T. O.
Published: October 2006

Pathogenic leptospires have the ability to survive and disseminate to multiple organs after penetrating the host. Several pathogens, including spirochetes, have been shown to express surface proteins that interact with the extracellular matrix (ECM). This adhesin-mediated binding process seems to be a crucial step in the colonization of host tissues. This study examined the interaction of putative leptospiral outer membrane proteins with laminin, collagen type I, collagen type IV, cellular fibronectin, and plasma fibronectin. Six predicted coding sequences selected from the
Leptospira interrogans
serovar Copenhageni genome were cloned, and proteins were expressed, purified by metal affinity chromatography, and characterized by circular dichroism spectroscopy. Their capacity to mediate attachment to ECM components was evaluated by binding assays. We have identified a leptospiral protein encoded by LIC12906, named Lsa24 (leptospiral surface adhesin; 24 kDa) that binds strongly to laminin. Attachment of Lsa24 to laminin was specific, dose dependent, and saturable. Laminin oxidation by sodium metaperiodate reduced the protein-laminin interaction in a concentration-dependent manner, indicating that laminin sugar moieties are crucial for this interaction. Triton X-114-solubilized extract of
L. interrogans
and phase partitioning showed that Lsa24 was exclusively in the detergent phase, indicating that it is a component of the leptospiral membrane. Moreover, Lsa24 partially inhibited leptospiral adherence to immobilized laminin. This newly identified membrane protein may play a role in mediating adhesion of
L. interrogans
to the host. To our knowledge, this is the first leptospiral adhesin with laminin-binding properties reported to date.
The K1 Serotype Capsular Polysaccharide ofPorphyromonas gingivalisElicits Chemokine Production from Murine Macrophages That Facilitates Cell Migration
Authors: d'Empaire Gabriela , Baer Michael T. , Gibson Frank C.
Published: October 2006

Porphyromonas gingivalisis the principal organism associated with aggressive forms of generalized periodontal disease. Previous reports have suggested that encapsulatedP. gingivalisstrains are more virulent than unencapsulated strains; however, the contribution of capsular polysaccharide (CPS) to the virulence of this organism is poorly understood. Since periodontal disease presents with a complex inflammatory cell lesion comprised of neutrophils and monocytes, we cultured murine peritoneal macrophages with heat-killedP. gingivalisW83, CPS purified fromP. gingivalisstrain W83, and the seven known serotype-specificP. gingivalisCPS and assessed the ability of supernatant fluids produced by challenged macrophages to attract naïve inflammatory cells. We also defined JE/MCP-1, KC, MIP-2, and RANTES production in response to theP. gingivalisCPS antigens. We observed that supernatant fluids collected from macrophages incubated withP. gingivalisW83 and serotype K1 CPS stimulated the migration of naïve murine bone marrow-derived polymorphonuclear leukocytes in an in vitro cell migration chamber. CPS from W83 and the K1 serotype elicited potent chemokine secretion patterns for macrophages, while those specific to serotypes K2 to K7 were significantly less stimulatory. Reverse transcription-PCR and enzyme-linked immunosorbent assay revealed JE/MCP-1, KC, MIP-2, and RANTES expression from murine macrophages which had been challenged with purifiedP. gingivalisW83 CPS. Chemokine production appeared to be dependent on both the dose of and time of exposure toP. gingivalisW83 CPS. These data demonstrate that theP. gingivalisserotype K1 CPS elicits chemokine production from phagocytic cells. Furthermore, these data suggest that the host response to this antigen may contribute to the formation of the inflammatory cell lesion observed duringP. gingivalis-elicited periodontal disease.
Protection Elicited by Two Glutamine Auxotrophs of
Mycobacterium tuberculosis
and In Vivo Growth Phenotypes of the Four Unique Glutamine Synthetase Mutants in a Murine Model
Authors: Lee Sunhee , Jeon Bo-Young , Bardarov Svetoslav , Chen Mei , Morris Sheldon L. , Jacobs William R.
Published: October 2006

We generated four individual glutamine synthetase (GS) mutants (Δ
glnA1
, Δ
glnA2
, Δ
glnA3
, and Δ
glnA4
) and one triple mutant (Δ
glnA1EA2
) of
Mycobacterium tuberculosis
to investigate the roles of GS enzymes. Subcutaneous immunization with the Δ
glnA1EA2
and Δ
glnA1
glutamine auxotrophic mutants conferred protection on C57BL/6 mice against an aerosol challenge with virulent
M. tuberculosis
, which was comparable to that provided by
Mycobacterium bovis
BCG vaccination.
Interaction of a Neurotropic Strain ofBorrelia turicataewith the Cerebral Microcirculation System
Authors: Sethi Nilay , Sondey Marie , Bai Yunhong , Kim Kwang S. , Cadavid Diego
Published: October 2006

Relapsing fever (RF) is a spirochetal infection characterized by relapses of a febrile illness and spirochetemia due to the sequential appearance and disappearance of isogenic serotypes in the blood. The only difference between isogenic serotypes is the variable major outer membrane lipoprotein. In the absence of specific antibody, established serotypes cause persistent infection. Studies in our laboratory indicate that another consequence of serotype switching in RF is a change in neuroinvasiveness. As the next step to elucidate this phenomenon, we studied the interaction of the neurotropic Oz1 strain of the RF agentBorrelia turicataewith the cerebral microcirculation. During persistent infection of antibody-deficient mice, we found that serotype 1 entered the brain in larger numbers and caused more severe cerebral microgliosis than isogenic serotype 2. Microscopic examination revealed binding ofB. turicataeto brain microvascular endothelial cells in vivo. In vitro we found thatB. turicataeassociated with brain microvascular endothelial cells (BMEC) significantly more than with fibroblasts or arachnoidal cells. The binding was completely eliminated by pretreatment of BMEC with proteinase K. Using transwell chambers with BMEC barriers, we found that serotype 1 crossed into the lower compartment significantly better than serotype 2. Heat killing significantly reduced BMEC crossing but not binding. We concluded that the interaction ofB. turicataewith the cerebral microcirculation involves both binding and crossing brain microvascular endothelial cells, with significant differences among isogenic serotypes.
Neutralization or Absence of the Interleukin-23 Pathway Does Not Compromise Immunity to Mycobacterial Infection
Authors: Chackerian Alissa A. , Chen Shi-Juan , Brodie Scott J. , Mattson Jeanine D. , McClanahan Terrill K. , Kastelein Robert A. , Bowman Edward P.
Published: October 2006

Interleukin-23 (IL-23), a member of the IL-12 family, is a heterodimeric cytokine that is composed of the p40 subunit of IL-12 plus a unique p19 subunit. IL-23 is critical for autoimmune inflammation, in part due to its stimulation of the proinflammatory cytokine IL-17A. It is less clear, however, if IL-23 is required during the immune response to pathogens. We examined the role of IL-23 during
Mycobacterium bovis
BCG infection. We found that IL-23 reduces the bacterial burden and promotes granuloma formation when IL-12 is absent. However, IL-23 does not contribute substantially to host resistance when IL-12 is present, as the ability to control bacterial growth and form granulomata is not affected in IL-23p19-deficient mice and mice treated with a specific anti-IL-23p19 antibody. IL-23p19-deficient mice are also able to mount an effective memory response to secondary infection with BCG. While IL-23p19-deficient mice do not produce IL-17A, this cytokine is not necessary for effective control of infection, and antibody blocking of IL-17A in both wild-type and IL-12-deficient mice also has little effect on the bacterial burden. These data suggest that IL-23 by itself does not play an essential role in the protective immune response to BCG infection; however, the presence of IL-23 can partially compensate for the absence of IL-12. Furthermore, neutralization of IL-23 or IL-17A does not increase susceptibility to mycobacterial BCG infection.
The
dbpBA
Locus of
Borrelia burgdorferi
Is Not Essential for Infection of Mice
Authors: Shi Yanlin , Xu Qilong , Seemanapalli Sunita V. , McShan Kristy , Liang Fang Ting
Published: October 2006

The Lyme disease spirochete
Borrelia burgdorferi
expresses a broad array of adhesive molecules, including the decorin-binding proteins A and B (DbpA and DbpB), which are believed to play important roles in mammalian infection. The
dbpBA
locus was deleted; resulting mutants were able to infect both immunodeficient and immunocompetent mice, indicating that neither DbpA nor DbpB is essential for the infection of mammals, although the DbpAB deficiency may significantly attenuate infectivity potential.
Structure of the Expression Site Reveals Global Diversity in MSP2 (P44) Variants in
Anaplasma phagocytophilum
Authors: Barbet Anthony F. , Lundgren Anna M. , Alleman A. Rick , Stuen Snorre , Bjöersdorff Anneli , Brown Richard N. , Drazenovich Niki L. , Foley Janet E.
Published: October 2006

Anaplasma phagocytophilum
, a recently reclassified bacteria in the order
Rickettsiales
, infects many different animal species and causes an emerging tick-borne disease of humans. The genome contains a large number of related genes and gene fragments encoding partial or apparently full-length outer membrane protein MSP2 (P44). Previous data using strains isolated from humans in the United States suggest that antigenic diversity results from RecF-mediated conversion of a single MSP2 (P44) expression site by partially homologous donor sequences. However, whether similar mechanisms operate in naturally infected animal species and the extent of global diversity in MSP2 (P44) are unknown. We analyzed the structure and diversity of the MSP2 (P44) expression site in strains derived from the United States and Europe and from infections of different animal species, including wildlife reservoirs. The results show that a syntenic expression site is present in all strains of
A. phagocytophilum
investigated. This genomic locus contained diverse MSP2 (P44) variants in all infected animals sampled, and variants also differed at different time points during infection. Although similar variants were found among different populations of U.S. origin, there was little sequence identity between U.S. strain variants (including genomic copies from a completely sequenced U.S. strain) and expression site variants infecting sheep and dogs in Norway and Sweden. Finally, the possibility that combinatorial mechanisms can generate additional diversity beyond the basic donor sequence repertoire is supported by the observation of shared sequence blocks throughout the MSP2 (P44) hypervariable region in reservoir hosts. These data suggest similar genetic mechanisms for
A. phagocytophilum
variation in all hosts but worldwide diversity of the MSP2 (P44) outer membrane protein.
Globally Distributed Mycobacterial Fish Pathogens Produce a Novel Plasmid-Encoded Toxic Macrolide, Mycolactone F
Authors: Ranger Brian S. , Mahrous Engy A. , Mosi Lydia , Adusumilli Sarojini , Lee Richard E. , Colorni Angelo , Rhodes Martha , Small P. L. C.
Published: October 2006

Mycobacterium ulcerans
and
Mycobacterium marinum
are closely related pathogens which share an aquatic environment. The pathogenesis of these organisms in humans is limited by their inability to grow above 35°C.
M. marinum
causes systemic disease in fish but produces localized skin infections in humans.
M. ulcerans
causes Buruli ulcer, a severe human skin lesion. At the molecular level,
M. ulcerans
is distinguished from
M. marinum
by the presence of a virulence plasmid which encodes a macrolide toxin, mycolactone, as well as by hundreds of insertion sequences, particularly IS
2404
. There has been a global increase in reports of fish mycobacteriosis. An unusual clade of
M. marinum
has been reported from fish in the Red and Mediterranean Seas and a new mycobacterial species,
Mycobacterium pseudoshottsii
, has been cultured from fish in the Chesapeake Bay, United States. We have discovered that both groups of fish pathogens produce a unique mycolactone toxin, mycolactone F. Mycolactone F is the smallest mycolactone (molecular weight, 700) yet identified. The core lactone structure of mycolactone F is identical to that of
M. ulcerans
mycolactones, but a unique side chain structure is present. Mycolactone F produces apoptosis and necrosis on cultured cells but is less potent than
M. ulcerans
mycolactones. Both groups of fish pathogens contain IS
2404
. In contrast to
M. ulcerans
and conventional
M. marinum
, mycolactone F-producing mycobacteria are incapable of growth at above 30°C. This fact is likely to limit their virulence for humans. However, such isolates may provide a reservoir for horizontal transfer of the mycolactone plasmid in aquatic environments.
Human Monoclonal Antibodies Directed against Toxins A and B Prevent
Clostridium difficile
-Induced Mortality in Hamsters
Authors: Babcock Gregory J. , Broering Teresa J. , Hernandez Hector J. , Mandell Robert B. , Donahue Katherine , Boatright Naomi , Stack Anne M. , Lowy Israel , Graziano Robert , Molrine Deborah , Ambrosino Donna M. , Thomas William D.
Published: October 2006

Clostridium difficile
is the leading cause of nosocomial antibiotic-associated diarrhea, and recent outbreaks of strains with increased virulence underscore the importance of identifying novel approaches to treat and prevent relapse of
Clostridium difficile-
associated diarrhea (CDAD). CDAD pathology is induced by two exotoxins, toxin A and toxin B, which have been shown to be cytotoxic and, in the case of toxin A, enterotoxic. In this report we describe fully human monoclonal antibodies (HuMAbs) that neutralize these toxins and prevent disease in hamsters. Transgenic mice carrying human immunoglobulin genes were used to isolate HuMAbs that neutralize the cytotoxic effects of either toxin A or toxin B in cell-based in vitro neutralization assays. Three anti-toxin A HuMAbs (3H2, CDA1, and 1B11) could all inhibit the enterotoxicity of toxin A in mouse intestinal loops and the in vivo toxicity in a systemic mouse model. Four anti-toxin B HuMAbs (MDX-1388, 103-174, 1G10, and 2A11) could neutralize cytotoxicity in vitro, although systemic toxicity in the mouse could not be neutralized. Anti-toxin A HuMAb CDA1 and anti-toxin B HuMAb MDX-1388 were tested in the well-established hamster model of
C. difficile
disease. CDA1 alone resulted in a statistically significant reduction of mortality in hamsters; however, the combination treatment offered enhanced protection. Compared to controls, combination therapy reduced mortality from 100% to 45% (
P
< 0.0001) in the primary disease hamster model and from 78% to 32% (
P
< 0.0001) in the less stringent relapse model.
Tsetse Fly Saliva Accelerates the Onset ofTrypanosoma bruceiInfection in a Mouse Model Associated with a Reduced Host Inflammatory Response
Authors: Caljon Guy , Van Den Abbeele Jan , Stijlemans Benoît , Coosemans Marc , De Baetselier Patrick , Magez Stefan
Published: October 2006

Tsetse flies (Glossinasp.) are the vectors that transmit African trypanosomes, protozoan parasites that cause human sleeping sickness and veterinary infections in the African continent. These blood-feeding dipteran insects deposit saliva at the feeding site that enables the blood-feeding process. Here we demonstrate that tsetse fly saliva also accelerates the onset of aTrypanosoma bruceiinfection. This effect was associated with a reduced inflammatory reaction at the site of infection initiation (reflected by a decrease of interleukin-6 [IL-6] and IL-12 mRNA) as well as lower serum concentrations of the trypanocidal cytokine tumor necrosis factor. Variant-specific surface glycoprotein-specific antibody isotypes immunoglobulin M (IgM) and IgG2a, implicated in trypanosome clearance, were not suppressed. We propose that tsetse fly saliva accelerates the onset of trypanosome infection by inhibiting local and systemic inflammatory responses involved in parasite control.
Road traffic noise and hypertension
Authors: Leon Bluhm Gösta , Berglind Niklas , Nordling Emma , Rosenlund Mats
Published: October 2006

Background:It has been suggested that noise exposure increases the risk of hypertension. Road traffic is the dominant source of community noise exposure.

Objective:To study the association between exposure to residential road traffic noise and hypertension in an urban municipality.

Methods:The study population comprised randomly selected subjects aged 19–80 years. A postal questionnaire provided information on individual characteristics, including diagnosis of hypertension. The response rate was 77%, resulting in a study population of 667 subjects. The outdoor equivalent traffic noise level (Leq 24 h) at the residence of each individual was determined using noise-dispersion models and manual noise assessments. The individual noise exposure was classified in units of 5 dB(A), from <45 dB(A) to >65 dB(A).

Results:The odds ratio (OR) for hypertension adjusted for age, smoking, occupational status and house type was 1.38 (95% confidence interval (CI) 1.06 to 1.80) per 5 dB(A) increase in noise exposure. The association seemed stronger among women (OR 1.71; 95% CI 1.17 to 2.50) and among those who had lived at the address for >10 years (OR 1.93; 95% CI 1.29 to 2.83). Analyses of categorical exposure variables suggested an exposure–response relationship. The strongest association between exposure to traffic noise and hypertension was found among those with the least expected misclassification of true individual exposure, as indicated by not having triple-glazed windows, living in an old house and having the bedroom window facing a street (OR 2.47; 95% CI 1.38 to 4.43).

Conclusion:The results of our study suggest an association between exposure to residential road traffic noise and hypertension.
GAPLESS COLOR–FLAVOR LOCKED PHASE IN QUARK AND HYBRID STARS
Authors: LAVAGNO A. , PAGLIARA G.
Published: October 2006

We study the effects of the gapless color–flavor locked (gCFL) phase on the equation of state of strongly interacting matter in the range of baryonic chemical potential involved in a compact star. We analyze the possibility of a phase transition from hadronic matter to gCFL quark matter and we discuss, for different values of the strange quark mass and diquark coupling strength, the existence of a gCFL phase in quark or hybrid stars. The mass–radius relation and the structure of compact stars containing the gCFL phase are shown and the physical relevance of this superconducting phase inside a stellar object is also discussed.
CASIMIR EFFECT FOR THE MASSLESS DIRAC FIELD IN TWO-DIMENSIONAL REISSNER–NORDSTRÖM SPACE–TIME
Authors: GAO XIN-QIN , ZHU JIAN-YANG
Published: October 2006

In this paper, the two-dimensional Reissner–Nordström black hole is considered as a system of the Casimir type. In this background, the Casimir effect for the massless Dirac field is discussed. The massless Dirac field is confined between two "parallel plates" separated by a distance L and there is no particle current drilling through the boundaries. The vacuum expectation values of the stress tensor of the massless Dirac field at infinity are calculated separately in the Boulware state, the Hartle–Hawking state and the Unruh state.
STRONG COUPLING EXPANSION FOR GENERAL RELATIVITY
Authors: FRASCA MARCO
Published: October 2006

Strong coupling expansion is computed for the Einstein equations in vacuum in the Arnowitt–Deser–Misner (ADM) formalism. The series is given by the duality principle in perturbation theory as presented in M. Frasca, Phys. Rev. A58, 3439 (1998). An example of application is also given for a two-dimensional model of gravity expressed through the Liouville equation showing that the expansion is not trivial and consistent with the exact solution, in agreement with the general analysis. Application to the Einstein equations in vacuum in the ADM formalism shows that the space–time near singularities is driven by space homogeneous equations.
SELF EXCITING THRESHOLD INTEREST RATES MODELS
Authors: DECAMPS MARC , GOOVAERTS MARC , SCHOUTENS WIM
Published: October 2006

In this paper, we study a new class of tractable diffusions suitable for model's primitives of interest rates. We consider scalar diffusions with scale s′(x) and speed m(x) densities discontinuous at the level x*. We call that family of processes Self Exciting Threshold (SET) diffusions. Following Gorovoi and Linetsky [18], we obtain semi-analytical expressions for the transition density of SET (killed) diffusions. We propose several applications to interest rates modeling. We show that SET short rate processes do not generate arbitrage possibilities and we adapt the HJM procedure to forward rates with discontinuous scale density. We also extend the CEV and the shifted-lognormal LIBOR market models. Finally, the models are calibrated to the US market. SET diffusions can also be used to model stock price, stochastic volatility, credit spread, etc.
LENGTH, AREA AND VOLUME COMPUTATION IN HOMOGENEOUS COORDINATES
Authors: SKALA VACLAV
Published: October 2006

Many problems solved in computer graphics, computer vision, visualization etc. require fast and robust computation of an area of a triangle or volume of a tetrahedron. These very often used algorithms are well known and robust if vertices coordinates of triangles or tetrahedrons are given in Euclidean coordinates. The homogeneous coordinates are often used for the representation of geometric transformations. They enable us to represent translation, rotation, scaling and projection operations in a unique way and handle them properly. Today's graphics hardware based on GPU offers very high computational power using pixel shaders and fragment shaders not only for graphical elements processing, but also for general computation using GPU as well.

This paper presents simple methods for the area of a triangle and the volume of a tetrahedron computation if vertices are given in homogeneous coordinates without the need to use the division operation for vertices coordinates transformation from the homogeneous coordinates to the Euclidean coordinates. Area or volume computation is transferred to the cross product computation that is fast, simple, and robust and can be supported in hardware or implemented on GPU that uses vector operations with homogeneous coordinates natively. The presented formula can be used directly for Euclidean representation just setting w equal to 1.
A NEW NOISE REMOVING ALGORITHM
Authors: BI DONG-LIANG , GUO WEI , XU AI-DONG
Published: October 2006

In this paper, we propose a new algorithm for removing Gaussian noise from natural images while preserving important details for further processing. Similar patches appear frequently in an image. Our algorithm is based on this high redundancy in natural images. Our initial step is to perform an image segmentation by a constrained quad-tree-split-and-merge technique. Then for each patch, using an extended SSD, we identify all similar patches in the image and recalculate the patch by summing up a weighted copy of each similar patch. Since the mean of white noise is zero, the final image will be noise free and important details are preserved. Experimental comparisons of Wiener Filter, Wavelet Threshold Methods and our method will be carried out by using different types of images. The result shows that our method is more efficient in both noise removing and detail preserving.
Adenosine inhibits cytosolic calcium signals and chemotaxis in hepatic stellate cells
Authors: Hashmi Ardeshir Z. , Hakim Wyel , Kruglov Emma A. , Watanabe Azuma , Watkins William , Dranoff Jonathan A. , Mehal Wajahat Z.
Published: October 2006

Adenosine is produced during cellular hypoxia and apoptosis, resulting in elevated tissue levels at sites of injury. Adenosine is also known to regulate a number of cellular responses to injury, but its role in hepatic stellate cell (HSC) biology and liver fibrosis is poorly understood. We tested the effect of adenosine on the cytosolic Ca2+ concentration, chemotaxis, and upregulation of activation markers in HSCs. We showed that adenosine did not induce an increase in the cytosolic Ca2+ concentration in LX-2 cells and, in addition, inhibited increases in the cytosolic Ca2+ concentration in response to ATP and PDGF. Using a Transwell system, we showed that adenosine strongly inhibited PDGF-induced HSC chemotaxis in a dose-dependent manner. This inhibition was mediated via the A2a receptor, was reversible, was reproduced by forskolin, and was blocked by the adenylate cyclase inhibitor 2,5-dideoxyadenosine. Adenosine also upregulated the production of TGF-β and collagen I mRNA. In conclusion, adenosine reversibly inhibits Ca2+ fluxes and chemotaxis of HSCs and upregulates TGF-β and collagen I mRNA. We propose that adenosine provides 1) a “stop” signal to HSCs when they reach sites of tissue injury with high adenosine concentrations and 2) stimulates transdifferentiation of HSCs by upregulating collagen and TGF-β production.
AT1 receptors in the nucleus tractus solitarii mediate the interaction between the baroreflex and the cardiac sympathetic afferent reflex in anesthetized rats
Authors: Wang Wei-Zhong , Gao Lie , Pan Yan-Xia , Zucker Irving H. , Wang Wei
Published: October 2006

The cardiac “sympathetic afferent” reflex (CSAR) has been reported to increase sympathetic outflow and depress baroreflex function via a central angiotensin II (ANG II) mechanism. In the present study, we examined the role of ANG II type 1 (AT1) receptors in the nucleus tractus solitarii (NTS) in mediating the interaction between the CSAR and the baroreflex in anesthetized rats. We examined the effects of bilateral microinjection of AT1 receptor antagonist losartan (100 pmol) into the NTS on baroreflex control of renal sympathetic nerve activity (RSNA) before and after CSAR activation by epicardial application of capsaicin (0.4 μg). Using single-unit extracellular recording, we further examined the effects of CSAR activation on the barosensitivity of barosensitive NTS neurons and the effects of intravenous losartan (2 mg/kg) on CSAR-induced changes in activity of NTS barosensitive neurons. Bilateral NTS microinjection of losartan significantly attenuated the increases in arterial pressure, heart rate, and RSNA evoked by capsaicin but also markedly ( P < 0.01) reversed the CSAR-induced blunted baroreflex control of RSNA (Gainmax from 1.65 ± 0.10 to 2.22 ± 0.11%/mmHg). In 17 of 24 (70.8%) NTS barosensitive neurons, CSAR activation significantly ( P < 0.01) inhibited the baseline neuronal activity and attenuated the neuronal barosensitivity. In 11 NTS barosensitive neurons, intravenous losartan effectively ( P < 0.01) normalized the decreased neuronal barosensitivity induced by CSAR activation. In conclusion, blockade of NTS AT1 receptors improved the blunted baroreflex during CSAR activation, suggesting that the NTS plays an important role in processing the interaction between the baroreflex and the CSAR via an AT1 receptor-dependent mechanism.