bluuebunny/crossref_metadata_2025 huggingface dataset:
Translation and Adaptation of the Social Support Network Inventory in Brazil
Authors: De Paula Lima Elenice Dias Ribeiro , Norman Elizabeth M. , De Paula Lima Alexandre
Published: August 2005

Purpose:To describe the translation and adaptation of the Social Support Network Inventory (SSNI) to Brazilian Portuguese.

Methods:The SSNI is a widely used, reliable, and valid instrument, designed to measure social support among English‐speaking people. The questionnaire was translated and adapted to the Brazilian‐Portuguese language by the back‐translation method. The translated version was evaluated in a sample of 120 Brazilian women in treatment for breast cancer.

Findings and Conclusions:Internal consistency and construct validity were examined, and the psychometric properties of the translated instrument were good. The translated SSNI was easily understood by the respondents and did not present difficulty during the interviews. The Portuguese version of the SSNI is a valid instrument to assess social support among Portuguese‐speaking patients.
Cement Formulations in the Calcium Phosphate H2O–H3PO4–H4P2O7 System
Authors: Grover Liam M. , Gbureck Uwe , Wright Adrian J. , Barralet Jake E.
Published: August 2005

Despite numerous reports of calcium phosphate cement materials, a calcium cement that sets to form a matrix consisting of a pyrophosphate phase has not been reported. The formulation of such a material from the mixture of α‐tricalcium phosphate (TCP), β‐TCP, or tetracalcium phosphate with a solution containing pyro‐ and orthophosphoric acid is reported in this study. The effects of liquid and solid compositions on the setting times, compressive strengths and phase compositions of the resultant cements were investigated. It was found that cements could be produced that set to form up to 28 wt% dicalcium pyrophosphate, which appeared by comparison with Rietveld refinement and chemical methods to be entirely amorphous in nature. The solubilities of the different solid components were shown to have a marked effect on the composition of the cements. The strongest cement formulations exhibited compressive strengths comparable with those previously reported in the literature for brushite cements and set within clinically relevant time scales. This class of cement would appear to demonstrate potential as a bone replacement material.
Compaction as a Critical Factor for Success in the Sintering of Ultra‐Fine WC–Co Powders
Authors: Jung Jinkwan , Kang Shinhoo
Published: August 2005

Heat treatment of ultra‐fine WC–13Co powders was carried out prior to cold compaction, in an attempt to improve the sintered density. The findings indicate that a preheat treatment of ultra‐fine or nano‐sized powders significantly improves the densification process. This study showed that a low compacting pressure, <200 MPa, can be effectively used through this technique to retain ultra‐fine structure. The densification behavior of preheated powder was compared with the samples prepared by a conventional technique and explained with size distribution, standard deviation, and surface effect.
Synthesis and Dielectric Characterization of Potassium Niobate Tantalate Ceramics
Authors: Venkatesh J. , Sherman V. , Setter N.
Published: August 2005

The preparation and dielectric properties of potassium niobate tantalate (KTN) have been investigated with the aim of exploring the material's potential for ferroelectric tunable applications. The samples were prepared both by conventional sintering in air and by uniaxial hot pressing. A relative average density greater than 92% was obtained with both methods. An inhomogeneous Nb/Ta distribution was found in the samples prepared by both methods, but the inhomogeneity extent was lower in the hot‐pressed samples. While both sintering processes resulted in ceramics of lower transition temperatures in comparison with the reported results on single crystals, a relative up shift of the temperature (Tmax) at which the dielectric constant is maximum was found for hot‐pressed samples compared with that of samples sintered in air. All the samples exhibited strong frequency dispersion in dielectric properties. The effect of DC bias at room temperature was measured and modeled using the Landau–Devonshire model. It was found that the nonlinear coefficient β of KTN, which is important for tunable applications, is comparable with the value reported on KNbO3 and SrTiO3 single crystals. A dielectric tunability of 16% and 42% at room temperature was demonstrated under 20 kV/cm for the sintered and hot‐pressed ceramics, respectively. The loss tangent, low at megahertz frequencies, was augmented to 9%–17% at low gigahertz frequencies. This is believed to be related to the frequency dispersion observed in the ceramics because of charged defects.
The impact of nicotine on osseointegration
Authors: Balatsouka Dimitra , Gotfredsen Klaus , Lindh Christian H. , Berglundh Tord
Published: August 2005

Objectives: The aim of the present study was to analyze the effect of an enhanced systematic dose of nicotine on osseointegration of titanium implants.

Material and methods: Sixteen female rabbits received either nicotine (n=8) or saline (n=8) administered subcutaneously via mini‐osmotic pumps for 2 months. The pump delivered 6 μg/kg/min of nicotine for the animals in the test group. Blood was withdrawn and plasma cotinine levels were measured weekly. Thirty‐two titanium implants were inserted into the femur and tibia of all rabbits after 4 weeks and after 6 weeks of nicotine/placebo exposure. Thus, 2‐ and 4‐week healing groups were created. Biomechanical evaluation by (i) resonance frequency analysis test (RFA) on all implants after insertion and before sacrifice and (ii) removal torque test (RMT) on tibial implants before sacrifice was performed. All implants placed in the femur were processed to undecalcified ground sections. The percentage of bone‐to‐implant contact (BIC) and of bone area within the threads (BD‐i) were measured.

Results: No significant difference in RMT and RFA values was found between the test and the control group. Histomorphometric measurements of the BIC and the peri‐implant BD‐i showed no significant differences between the test and the control group after 2 or after 4 weeks.

Conclusion: Nicotine exposure for a short period of time even in a high dose did not have a significant impact on implant osseointegration in rabbits.
Platelet‐rich plasma influence on human osteoblasts growth
Authors: Ferreira Cimara Fortes , Carriel Gomes Márcia Cristina , Filho José Scarso , Granjeiro José Mauro , Oliveira Simões Cláudia Maria , Magini Ricardo de Souza
Published: August 2005

Objective: The influence of progressively high concentrations of platelet‐rich plasma (PRP) on human osteoblast hFOB1.19 proliferation was evaluated.

Material and methods: The PRP was obtained from a human source. Two experiments were conducted. In the first one, PRP was diluted to 50%, 25%, 12.5% and 6.125% (v/v) with culture medium (Modified Eagle's Medium (MEM) : Ham's F12 Medium (HAM‐F12%) and 1% antibiotics–antimicotic) supplemented with 10% of fetal bovine serum (FBS). In the second experiment, all conditions were identical except for the absence of FBS in the culture medium.

Results: The results of the osteoblast proliferation test were higher when stimulated by the 50% PRP dilution, with or without FBS. A further study is suggested to determine if concentrations above 50% could cause higher rates of osteoblast proliferation. In this study, the results were not statistically different (P<0.05) with 12.5% and 6.125% PRP dilutions. Additionally, it was shown that FBS is not necessary for PRP‐mediated induction of osteoblast proliferation.

Conclusion: This study concluded that PRP promotes osteoblast proliferation and suggested its clinical application to bone graft procedures in implant dentistry.
Positive effect of early loading on implant stability in the bi‐cortical guinea‐pig model
Authors: De Smet Els , Jaecques Siegfried , Vandamme Katleen , Vander Sloten Jos , Naert Ignace
Published: August 2005

Abstract: Loading, early after implant placement, has gained rapid interest in dentistry. Primary implant stability, as e.g. defined by resonance frequency instrumentation, has been isolated as a predicator when immediate and early implant loading is applied. The aim of this study was to investigate the effect of early (after 7 days) mechanical loading on the establishment of osseointegration by means of resonance frequency analysis (RFA). Percutaneous titanium implants were installed in both tibiae of 10 guinea‐pigs. One week after implant installation, one implant (test) was loaded daily for 6 weeks, while the contra‐lateral served as the unloaded one (control). A sinusoidally varying bending moment was applied at a frequency of 3 Hz and a force amplitude of 5 N, for 1800 cycli. Resonance frequency was measured at implant installation and from then on weekly using the RFA‐device (Osstell®). Contrary to control implants, that showed a decrease in stability 1 week after installation, reaching a minimum at 3 weeks (−200 Hz), test implants showed a progressive increase in stability over time. After 6 weeks, the mean resonance frequency of test and control implants reached the same values. As confirmed by recent literature, early loading does not have to endanger the establishment of osseointegration of titanium implants. On the contrary, controlled loading is beneficial to maintain the implant stability during the early critical healing period as determined by RFA‐measurements.
Demographische Entwicklung der Bevölkerung
Authors: Diepgen Thomas L.
Published: August 2005

Im Laufe des letzten Jahrhunderts hat die mittlere Lebenserwartung in Deutschland um rund 30 Jahre zugenommen. Prognosen sagen voraus, dass die mittlere Lebenserwartung weiter steigen wird. Nicht nur die Zahl der Älteren, sondern auch ihr Anteil an der Bevölkerung haben zugenommen und werden weiter zunehmen. Dies hat erhebliche gesundheitspolitische und ‐ökonomische Konsequenzen. Die Auswirkungen des Alterns der Bevölkerung betrifft auch, ja vielleicht sogar in besonderem Maße die Dermatologie. Erstens nehmen manche Hauterkrankungen ohnehin mit dem Alter aufgrund der langjährigen Kumulation exogener Belastungsfaktoren zu, zweitens betrifft der Alterungsprozess in besonderem Maße das Hautorgan und drittens hat ein gesellschaftlicher Wandel in der Bevölkerung stattgefunden, der die Grenze zwischen behandlungsbedürftiger Hautveränderung und gesellschaftlich akzeptiertem kosmetischen Hautproblem stark verschoben hat. Die zu erwartenden demographischen Veränderungen bei gleichzeitig im Allgemeinen schlechten dermatologischen Versorgungssituation des alten Menschen wird eine wichtig gesundheitspolitische Herausforderung auch für die Dermatologie darstellen.
Mechanisms of target‐cell specific short‐term plasticity at Schaffer collateral synapses onto interneurones versus pyramidal cells in juvenile rats
Authors: Sun Hua Yu , Lyons Susan A. , Dobrunz Lynn E.
Published: August 2005

Although it is presynaptic, short‐term plasticity has been shown at some synapses to depend upon the postsynaptic cell type. Previous studies have reported conflicting results as to whether Schaffer collateral axons have target‐cell specific short‐term plasticity. Here we investigate in detail the short‐term dynamics of Schaffer collateral excitatory synapses onto CA1 stratum radiatum interneurones versus pyramidal cells in acute hippocampal slices from juvenile rats. In response to three stimulus protocols that invoke different forms of short‐term plasticity, we find differences in some but not all forms of presynaptic short‐term plasticity, and heterogeneity in the short term plasticity of synapses onto interneurones. Excitatory synapses onto the majority of interneurones had less paired‐pulse facilitation than synapses onto pyramidal cells across a range of interpulse intervals (20–200 ms). Unlike synapses onto pyramidal cells, synapses onto most interneurones had very little facilitation in response to short high‐frequency trains of five pulses at 5, 10 and 20 Hz, and depressed during trains at 50 Hz. However, the amount of high‐frequency depression was not different between synapses onto pyramidal cells versus the majority of interneurones at steady state during 2–10 Hz trains. In addition, a small subset of interneurones (approximately 15%) had paired‐pulse depression rather than paired‐pulse facilitation, showed only depression in response to the high‐frequency five pulse trains, and had more steady‐state high‐frequency depression than synapses onto pyramidal cells or the majority of interneurones. To investigate possible mechanisms for these differences in short‐term plasticity, we developed a mechanistic mathematical model of neurotransmitter release that explicitly explores the contributions to different forms of short‐term plasticity of the readily releasable vesicle pool size, release probability per vesicle, calcium‐dependent facilitation, synapse inactivation following release, and calcium‐dependent recovery from inactivation. Our model fits the responses of each of the three cell groups to the three different stimulus protocols with only two parameters that differ with cell group. The model predicts that the differences in short‐term plasticity between synapses onto CA1 pyramidal cells and stratum radiatum interneurones are due to a higher initial release probability per vesicle and larger readily releasable vesicle pool size at synapses onto interneurones, resulting in a higher initial release probability. By measuring the rate of block of NMDA receptors by the open channel blocker MK‐801, we confirmed that the initial release probability is greater at synapses onto interneurones versus pyramidal cells. This provides a mechanism by which both the initial strength and the short‐term dynamics of Schaffer collateral excitatory synapses are regulated by their postsynaptic target cell.
Experimental Analysis of Cracked Rotor
Authors: Zhou Tong , Sun Zhengce , Xu Jianxue , Han Weihua
Published: August 2005

The dynamic behavior of a cracked rotor has been theoretically analyzed by many researchers. In this paper, an experimental confirmation of the theoretical results is sought, especially for the nonlinear dynamic behavior of the cracked rotor. The crack in the rotor was simulated by a real fatigue crack, instead of a narrow slot. It can be seen from the orbit and spectrum of the rotor’s center that the effect of the crack becomes obvious only if the crack is deep enough. The experimental result conforms to theoretical analysis very well.
A Thermodynamic Model of Membrane Humidifiers for PEM Fuel Cell Humidification Control
Authors: Chen Dongmei , Peng Huei
Published: August 2005

Maintaining proper membrane humidity is crucial to ensure optimal operation of a polymer electrolyte membrane fuel cell system. A membrane humidifier using the fuel cell exhaust gas to humidify the dry air is studied in this paper. We first develop a thermodynamic model, which captures the crucial dynamic variables of the humidifier, including the pressure, flow rate, temperature, and relative humidity of the air flow. Steady-state simulations are then conducted to optimize the humidifier design. Subsequently, dynamic simulations are performed to predict the behavior of the humidifier during transient operations typical for automotive applications. A simple proportional controller was designed to control the humidifier operation.
Dynamic Modeling of Residual-Affected Homogeneous Charge Compression Ignition Engines with Variable Valve Actuation
Authors: Shaver Gregory M. , Gerdes J. Christian , Roelle Matthew J. , Caton Patrick A. , Edwards Christopher F.
Published: August 2005

One practical method for achieving homogeneous charge compression ignition (HCCI) in internal combustion engines is to modulate the valves to trap or reinduct exhaust gases, increasing the energy of the charge, and enabling autoignition. Controlling combustion phasing with valve modulation can be challenging, however, since any controller must operate through the chemical kinetics of HCCI and account for the cycle-to-cycle dynamics arising from the retained exhaust gas. This paper presents a simple model of the overall HCCI process that captures these fundamental aspects. The model uses an integrated Arrhenius rate expression to capture the importance of species concentrations and temperature on the ignition process and predict the start of combustion. The cycle-to-cycle dynamics, in turn, develop through mass exchange between a control volume representing the cylinder and a control mass modeling the exhaust manifold. Despite its simplicity, the model predicts combustion phasing, pressure evolution and work output for propane combustion experiments at levels of fidelity comparable to more complex representations. Transient responses to valve timing changes are also captured and, with minor modification, the model can, in principle, be extended to handle a variety of fuels.
Automatic Loop Shaping of Structured Controllers Satisfying QFT Performance
Authors: Yaniv O. , Nagurka M.
Published: August 2005

This paper presents a robust noniterative algorithm for the design of controllers of a given structure satisfying frequency-dependent sensitivity specifications. The method is well suited for automatic loop shaping, particularly in the context of Quantitative Feedback Theory (QFT), and offers several advantages, including (i) it can be applied to unstructured uncertain plants, be they stable, unstable or nonminimum phase, (ii) it can be used to design a satisfactory controller of a given structure for plants which are typically difficult to control, such as highly underdamped plants, and (iii) it is suited for design problems incorporating hard restrictions such as bounds on the high-frequency gain or damping of a notch filter. It is assumed that the designer has some idea of the controller structure appropriate for the loop shaping problem.
Late Cenozoic Moisture History of East Africa
Authors: Trauth Martin H. , Maslin Mark A. , Deino Alan , Strecker Manfred R.
Published: August 2005

Lake sediments in 10 Ethiopian, Kenyan, and Tanzanian rift basins suggest that there were three humid periods at 2.7 to 2.5 million years ago (Ma), 1.9 to 1.7 Ma, and 1.1 to 0.9 Ma, superimposed on the longer-term aridification of East Africa. These humid periods correlate with increased aridity in northwest and northeast Africa and with substantial global climate transitions. These episodes could have had important impacts on the speciation and dispersal of mammals and hominins, because a number of key events, such as the origin of the genus
Homo
and the evolution of the species
Homo erectus
, took place in this region during that time.
Bright X-ray Flares in Gamma-Ray Burst Afterglows
Authors: Burrows D. N. , Romano P. , Falcone A. , Kobayashi S. , Zhang B. , Moretti A. , O'Brien P. T. , Goad M. R. , Campana S. , Page K. L. , Angelini L. , Barthelmy S. , Beardmore A. P. , Capalbi M. , Chincarini G. , Cummings J. , Cusumano G. , Fox D. , Giommi P. , Hill J. E. , Kennea J. A. , Krimm H. , Mangano V. , Marshall F. , Mészáros P. , Morris D. C. , Nousek J. A. , Osborne J. P. , Pagani C. , Perri M. , Tagliaferri G. , Wells A. A. , Woosley S. , Gehrels N.
Published: August 2005

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.
Salmonella enterica
Serotype Typhimurium Fimbrial Proteins Serve as Antigens during Infection of Mice
Authors: Humphries Andrea , DeRidder Sandra , Bäumler Andreas J.
Published: August 2005

The
Salmonella enterica
serotype Typhimurium genome contains 13 operons with homology to fimbrial gene sequences. Here we investigated the role of 11 serotype Typhimurium fimbrial proteins, including FimA, AgfA (CsgA), BcfA, StbA, SthA, LpfA, PefA, StdA, StcA, StiA, and StfA, as antigens during the infection of genetically resistant mice (CBA). Upon the growth of serotype Typhimurium in standard laboratory broth culture, only the expression of FimA could be detected by Western blot analysis. The infection of mice with serotype Typhimurium grown in broth culture, followed by at least one subsequent infection, resulted in seroconversion of animals to FimA, AgfA, BcfA, StbA, SthA, LpfA, PefA, StdA, StcA, StiA, and StfA positivity. Most animals seroconverted to only a subset of these fimbrial antigens. The immunization of mice with glutathione
S
-transferase (GST)-FimA, GST-AgfA, GST-BcfA, GST-StbA, GST-SthA, GST-LpfA, GST-PefA, GST-StdA, GST-StcA, GST-StiA, and GST-StfA fusion proteins resulted in reduced fecal shedding of serotype Typhimurium during a challenge compared to that by a control group immunized with purified GST protein. Collectively, these data suggest that the expression of serotype Typhimurium fimbrial antigens is induced during the infection of mice.
Involvement of Fractalkine/CX3CL1 Expression by Dendritic Cells in the Enhancement of Host Immunity against
Legionella pneumophila
Authors: Kikuchi Toshiaki , Andarini Sita , Xin Hong , Gomi Kazunori , Tokue Yutaka , Saijo Yasuo , Honjo Tasuku , Watanabe Akira , Nukiwa Toshihiro
Published: August 2005

Legionnaires' disease is clinically manifested as severe pneumonia caused by
Legionella pneumophila
. However, the dendritic cell (DC)-centered immunological framework of the host defense against
L. pneumophila
has not been fully delineated. For this study, we focused on a potent chemoattractant for lymphocytes, fractalkine/CX3CL1, and observed that the fractalkine expression of DCs was somewhat up-regulated when they encountered
L. pneumophila
. We therefore hypothesized that fractalkine expressed by
Legionella
-capturing DCs is involved in the induction of T-cell-mediated immune responses against
Legionella
, which would be enhanced by a genetic modulation of DCs to overexpress fractalkine. In vivo immunization-challenge experiments demonstrated that DCs modified with a recombinant adenovirus vector to overexpress fractalkine (AdFKN) and pulsed with heat-killed
Legionella
protected immunized mice from a lethal
Legionella
infection and that the generation of in vivo protective immunity depended on the host lymphocyte subsets, including CD4
+
T cells, CD8
+
T cells, and B cells. Consistent with this, immunization with AdFKN/
Legionella
/DC induced significantly higher levels of serum anti-
Legionella
antibodies of several isotypes than those induced by control immunizations. Further analysis of spleen cells from the immunized mice indicated that the AdFKN/
Legionella
/DC immunization elicited Th1-dominated immune responses to
L. pneumophila
. These observations suggest that fractalkine may play an important role in the DC-mediated host defense against intracellular pathogens such as
L. pneumophila
.
Porphyromonas gingivalisFimbria-Dependent Activation of Inflammatory Genes in Human Aortic Endothelial Cells
Authors: Chou Hsin-Hua , Yumoto Hiromichi , Davey Michael , Takahashi Yusuke , Miyamoto Takanari , Gibson Frank C. , Genco Caroline A.
Published: August 2005

Epidemiological and pathological studies have suggested that infection with the oral pathogenPorphyromonas gingivaliscan potentiate atherosclerosis and human coronary heart disease. Furthermore, infection with invasive, but not noninvasiveP. gingivalishas been demonstrated to accelerate atherosclerosis in apolipoprotein E-deficient (ApoE−/−) mice and to accelerate local inflammatory responses in aortic tissue. In the present study, using high-density oligonucleotide microarrays, we have defined the gene expression profile of human aortic endothelial cells (HAEC) after infection with invasive and noninvasiveP. gingivalis. After infection of HAEC with invasiveP. gingivalisstrain 381, we observed the upregulation of 68 genes. Genes coding for the cytokines Gro2 and Gro3; the adhesion molecules intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule (VCAM)-1, and ELAM-1 (E-selectin); the chemokine interleukin-8 (IL-8); and the proinflammatory molecules IL-6 and cyclooxygenase-2 were among the most highly upregulated genes inP. gingivalis381-infected HAEC compared to uninfected HAEC control. Increased mRNA levels for signaling molecules, transcriptional regulators, and cell surface receptors were also observed. Of note, only 4 of these 68 genes were also upregulated in HAEC infected with the noninvasiveP. gingivalis fimAmutant. Reverse transcription-PCR, enzyme-linked immunosorbent assay, and fluorescence-activated cell sorting analysis confirmed the expression of ICAM-1, VCAM-1, E-/P-selectins, IL-6, and IL-8 in HAEC infected with invasiveP. gingivalis. We also demonstrated that increased expression of ICAM-1 and VCAM-1 in aortic tissue of ApoE−/−mice orally challenged with invasiveP. gingivalisbut not with the noninvasiveP. gingivalis fimAmutant by immunohistochemical analysis. Taken together, these results demonstrate thatP. gingivalisfimbria-mediated invasion upregulates inflammatory gene expression in HAEC and in aortic tissue and indicates that invasiveP. gingivalisinfection accelerates inflammatory responses directly in the aorta.
Cable Pili and the 22-Kilodalton Adhesin Are Required for
Burkholderia cenocepacia
Binding to and Transmigration across the Squamous Epithelium
Authors: Urban Teresa A. , Goldberg Joanna B. , Forstner Janet F. , Sajjan Umadevi S.
Published: August 2005

Burkholderia cenocepacia
strains expressing both cable (Cbl) pili and the 22-kDa adhesin bind to cytokeratin 13 (CK13) strongly and invade squamous epithelium efficiently. It has not been established, however, whether the gene encoding the adhesin is located in the
cbl
operon or what specific contribution the adhesin and Cbl pili lend to binding and transmigration or invasion capacity of
B. cenocepacia
. By immunoscreening an expression library of
B. cenocepacia
isolate BC7, we identified a large gene (
adhA
) that encodes the 22-kDa adhesin. Isogenic mutants lacking expression of either Cbl pili (
cblA
or
cblS
mutants) or the adhesin (
adhA
mutant) were constructed to assess the individual role of Cbl pili and the adhesin in mediating
B. cenocepacia
binding to and transmigration across squamous epithelium. Relative to the parent strain, mutants of Cbl pili showed reduced binding (50%) to isolated CK13, while the adhesin mutant showed almost no binding (0 to 8%). Mutants lacking either cable pili or the adhesin were compromised in their ability to bind to and transmigrate across the squamous epithelium compared to the wild-type strain, although this deficiency was most pronounced in the
adhA
mutant. These results indicate that both Cbl pili and the 22-kDa adhesin are necessary for the optimal binding to CK13 and transmigration properties of
B. cenocepacia
.
Iron Acquisition from Transferrin by
Candida albicans
Depends on the Reductive Pathway
Authors: Knight Simon A. B. , Vilaire Gaston , Lesuisse Emmanuel , Dancis Andrew
Published: August 2005

Host-pathogen interactions that alter virulence are influenced by critical nutrients such as iron. In humans, free iron is unavailable, being present only in high-affinity iron binding proteins such as transferrin. The fungal pathogen
Candida albicans
grows as a saprophyte on mucosal surfaces. Occasionally it invades systemically, and in this circumstance it will encounter transferrin iron. Here we report that
C. albicans
is able to acquire iron from transferrin. Iron-loaded transferrin restored growth to cultures arrested by iron deprivation, whereas apotransferrin was unable to promote growth. By using congenic strains, we have been able to show that iron uptake by
C. albicans
from transferrin was mediated by the reductive pathway (via
FTR1
). The genetically separate siderophore and heme uptake systems were not involved.
FRE10
was required for a surface reductase activity and for efficient transferrin iron uptake activity in unbuffered medium. Other reductase genes were apparently up-regulated in medium buffered at pH 6.3 to 6.4, and the
fre10
−/−
mutant had no effect under these conditions. Experiments in which transferrin was sequestered in a dialysis bag demonstrated that cell contact with the substrate was required for iron reduction and release. The requirement of
FTR1
for virulence in a systemic infection model and its role in transferrin iron uptake raise the possibility that transferrin is a source of iron during systemic
C. albicans
infections.
The
Aspergillus fumigatus
Siderophore Biosynthetic Gene
sidA
, Encoding
l
-Ornithine
N
5
-Oxygenase, Is Required for Virulence
Authors: Hissen Anna H. T. , Wan Adrian N. C. , Warwas Mark L. , Pinto Linda J. , Moore Margo M.
Published: August 2005

Aspergillus fumigatus
is the leading cause of invasive mold infection and is a serious problem in immunocompromised populations worldwide. We have previously shown that survival of
A. fumigatus
in serum may be related to secretion of siderophores. In this study, we identified and characterized the
sidA
gene of
A. fumigatus
, which encodes
l
-ornithine
N
5
-oxygenase, the first committed step in hydroxamate siderophore biosynthesis.
A. fumigatus sidA
codes for a protein of 501 amino acids with significant homology to other fungal
l
-ornithine
N
5
-oxygenases. A stable Δ
sidA
strain was created by deletion of
A. fumigatus sidA
. This strain was unable to synthesize the siderophores
N
′,
N
",
N
‴-triacetylfusarinine C (TAF) and ferricrocin. Growth of the Δ
sidA
strain was the same as that of the wild type in rich media; however, the Δ
sidA
strain was unable to grow in low-iron defined media or media containing 10% human serum unless supplemented with TAF or ferricrocin. No significant differences in ferric reduction activities were observed between the parental strain and the Δ
sidA
strain, indicating that blocking siderophore secretion did not result in upregulation of this pathway. Unlike the parental strain, the Δ
sidA
strain was unable to remove iron from human transferrin. A rescued strain (Δ
sidA + sidA
) was constructed; it produced siderophores and had the same growth as the wild type on iron-limited media. Unlike the wild-type and rescued strains, the Δ
sidA
strain was avirulent in a mouse model of invasive aspergillosis, indicating that
sidA
is necessary for
A. fumigatus
virulence.
Mannheimia haemolytica
Leukotoxin Induces Apoptosis of Bovine Lymphoblastoid Cells (BL-3) via a Caspase-9-Dependent Mitochondrial Pathway
Authors: Atapattu Dhammika N. , Czuprynski Charles J.
Published: August 2005

Mannheimia haemolytica
is a key pathogen in the bovine respiratory disease complex. It produces a leukotoxin (LKT) that is an important virulence factor, causing cell death in bovine leukocytes. The LKT binds to the β
2
integrin CD11a/CD18, which usually activates signaling pathways that facilitate cell survival. In this study, we investigated mechanisms by which LKT induces death in bovine lymphoblastoid cells (BL-3). Incubation of BL-3 cells with a low concentration of LKT results in the activation of caspase-3 and caspase-9 but not caspase-8. Similarly, the proapoptotic proteins Bax and BAD were significantly elevated, while the antiapoptotic proteins Bcl-2, Bcl
XL
and Akt-1 were downregulated. Following exposure to LKT, we also observed a reduction in mitochondrial cytochrome
c
and corresponding elevation of cytosolic cytochrome
c
, suggesting translocation from the mitochondrial compartment to the cytosol. Consistent with this observation, tetramethylrhodamine ethyl ester perchlorate staining revealed that mitochondrial membrane potential was significantly reduced. These data suggest that LKT induces apoptosis of BL-3 cells via a caspase-9-dependent mitochondrial pathway. Furthermore, scanning electron micrographs of mitochondria from LKT-treated BL-3 cells revealed lesions in the outer mitochondrial membrane, which are larger than previous reports of the permeability transition pore through which cytochrome
c
is usually released.
Role of FliF and FliI of
Listeria monocytogenes
in Flagellar Assembly and Pathogenicity
Authors: Bigot Armelle , Pagniez Hélène , Botton Eléonore , Fréhel Claude , Dubail Iharilalao , Jacquet Christine , Charbit Alain , Raynaud Catherine
Published: August 2005

Flagellar structures have been shown to participate in virulence in a variety of intestinal pathogens. Here, we have identified two potential flagellar genes of
Listeria monocytogenes
: lmo0713, encoding a protein similar to the flagellar basal body component FliF, and lmo0716, encoding a protein similar to FliI, the cognate ATPase energizing the flagellar export apparatus. Expression of
fliF
and
fliI
appears to be downregulated at 37°C, like that of
flaA
, encoding flagellin. By constructing two chromosomal deletion mutants, we show that inactivation of either
fliF
or
fliI
(i) abolishes bacterial motility and flagella production, (ii) impairs adhesion and entry into nonphagocytic epithelial cells, and (iii) also reduces uptake by bone marrow-derived macrophages. However, the Δ
fliF
and Δ
fliI
mutations have only a minor impact on bacterial virulence in the mouse model, indicating that the flagellar secretion apparatus itself is not essential for survival in this animal model. Finally, among 100 human clinical isolates of
L. monocytogenes
tested, we found 20 strains still motile at 37°C. Notably, all these strains adhered less efficiently than strain EGD-e to Caco-2 cells at 37°C but showed no defect of intracellular multiplication. These data suggest that expression of the flagella at 37°C might hinder optimal adhesion to epithelial cells but has no impact on intracytosolic survival of
L. monocytogenes
.
Characterization of Novel Staphylococcal Enterotoxin-Like Toxin Type P
Authors: Omoe Katsuhiko , Imanishi Ken'ichi , Hu Dong-Liang , Kato Hidehito , Fugane Yoshitaku , Abe Yohei , Hamaoka Shoji , Watanabe Yutaka , Nakane Akio , Uchiyama Takehiko , Shinagawa Kunihiro
Published: August 2005

We investigated the biological properties of a novel staphylococcal enterotoxin (SE)-like toxin type P (SElP). SElP induced a substantial proliferative response and the production of cytokines interleukin-2, gamma interferon, tumor necrosis factor alpha, and interleukin-4 from human T cells when administered at a concentration of 0.4 pM (0.01 ng/ml) or more. The expression of major histocompatibility complex class II molecules on accessory cells was required for T-cell stimulation by SElP. SElP selectively stimulated a vast number of human T cells bearing receptors Vβ 5.1, 6, 8, 16, 18, and 21.3. These results indicated that SElP acts as a superantigen. SElP proved to be emetic in the house musk shrew emetic assay, although at a relatively high dose (50 to 150 μg/animal). A quantitative assay of SElP production with 30Staphylococcus aureusstrains harboringselpshowed that 60% of these strains produced significant amounts of SElP in vitro. All 10 strains carryingsebandselpproduced SEB but not SElP, suggesting the inactivation of theselplocus inS. aureusstrains with a particularsegene constitution.
Borrelia burgdorferiOrganisms Lacking Plasmids 25 and 28-1 Are Internalized by Human Blood Phagocytes at a Rate Identical to That of the Wild-Type Strain
Authors: Al-Robaiy Samiya , Knauer Jens , Straubinger Reinhard K.
Published: August 2005

Lyme borreliosis caused byBorrelia burgdorferiis a persistent infection capable of withstanding the host's vigorous immune response. Several reports have shown that the spirochete's linear plasmids 25 and 28-1 are essential for its infectivity. In this context, it was proposed thatBorrelia burgdorferiorganisms control their uptake by macrophages and polymorphonuclear leukocytes (PMNs) through plasmid-encoded proteins and that this mechanism confers resistance to phagocytosis. To investigate this proposal, a precise flow-cytometry-based method with human blood was used to study the impact of the plasmids 25 and 28-1 onB. burgdorfericlearance over 150 min and to investigate whether low-passage organisms are more resistant to phagocytosis than high-passageB. burgdorferi. Exposure of human blood PMNs or blood monocytes to fluorescein isothiocyanate-labeledB. burgdorferiB31 organisms lacking the linear plasmids 25, 28-1, or both revealed that all spirochete populations were internalized at the same rate as the wild-type borrelia parent strain B31. Moreover, no differences in phagocytosis kinetics were detected when low- or high-passage wild-typeB. burgdorferiB31 or N40 were cocultured with blood cells. Plasmid loss and probable associated surface protein changes due to serial in vitro propagation ofB. burgdorferido not affect the resistance of these organisms to internalization by phagocytic cells. In particular, we found no evidence for a plasmid-controlled (lp25 and lp28-1) resistance ofB. burgdorferito phagocytosis by leukocytes of the host's innate immune system.
Cholera Toxin Induces a Transient Depletion of CD8+Intraepithelial Lymphocytes in the Rat Small Intestine as Detected by Microarray and Immunohistochemistry
Authors: Flach Carl-Fredrik , Lange Stefan , Jennische Eva , Lönnroth Ivar , Holmgren Jan
Published: August 2005

Cholera toxin (CT), besides causing intestinal hypersecretion after intragastric administration or during cholera infection, affects a multitude of regulatory mechanisms within the gut mucosal network, including T cells. By use of microarray screening, real-time PCR, and immunohistochemistry, we demonstrate here a rapid depletion of jejunal CD8+intraepithelial lymphocytes (IEL) in rats after intragastric CT challenge. This depletion may depend on CT-induced migration of IEL, since it was associated with a progressive decrease of CD8+cells in the epithelium and a contemporary transient increase of such cells, preferentially at the base of the villi, in the lamina propria. A significant decrease in the total number of villous CD8+cells at 6 and 18 h after CT challenge was detected; this possibly reflects an efflux from the jejunal mucosa. The kinetics of the CD8+IEL demonstrate the return to normal intraepithelial position at original numbers already 72 h after the single CT dose. The induced migration seems to be dependent on the enzymatic A-subunit of CT, since challenge with neither sorbitol nor CT B-subunit did mimic the effects of CT on CD8+IEL. Furthermore, a decrease in the level of both RANTES transcript and protein was detected, most likely as a consequence of the CT-induced migration of CD8+IEL. These results point to a complex interaction between CT, epithelial cells, and IEL, resulting in a disturbance of the gut homeostasis, which might have relevance for the strong immunomodulatory effects of intragastrically administered CT.
Bacteroides fragilis-Derived Lipopolysaccharide Produces Cell Activation and Lethal Toxicity via Toll-Like Receptor 4
Authors: Mancuso Giuseppe , Midiri Angelina , Biondo Carmelo , Beninati Concetta , Gambuzza Maria , Macrì Daniele , Bellantoni Antonella , Weintraub Andrej , Espevik Terje , Teti Giuseppe
Published: August 2005

Bacteroides fragilis, which is part of the normal intestinal flora, is a frequent cause of serious disease, especially in diabetic and surgical patients. In these conditions,B. fragilislipopolysaccharide (LPS) is likely to play a major pathophysiologic role.B. fragilisLPS is structurally different from classical enterobacterial LPS, whose biological activities are mediated by Toll-like receptor 4 (TLR4) activation. The ability ofB. fragilisLPS to activate TLR4 and TLR2 was investigated here, since evidence on this issue is scarce and controversial. Each of four different protein-freeB. fragilisLPS preparations could induce interleukin-8 responses in cells cotransfected with TLR4/CD14/MD2 but not TLR4/CD14 alone. Two of the preparations also induced cytokine production in cells cotransfected with TLR2/CD14 or in peritoneal macrophages from TLR4 mutant C3H/HeJ mice. Both of these activities, however, were lost after repurification with a modified phenol reextraction procedure. Importantly, all preparations could induce endotoxic shock in TLR2-deficient mice, but not in TLR4 mutant C3H/HeJ mice. Consistent with these findings, anti-TLR4 and anti-CD14, but not anti-TLR2, antibodies could inhibitB. fragilisLPS-induced cytokine production in human monocytes. Collectively, these results indicate thatB. fragilisLPS signals via a TLR4/CD14/MD2-dependent pathway, and it is unable to activate TLR2. Moreover, our data document the occurrence of TLR2-activating contaminants even in highly purifiedB. fragilisLPS preparations. This may explain earlier contradictory findings on the ability ofB. fragilisLPS to activate cells in the absence of functional TLR4. These data may be useful to devise strategies to prevent the pathophysiologic changes observed duringB. fragilissepsis and to better understand structure-activity relationships of LPS.
Mutations Affecting Peptidoglycan Acetylation in
Neisseria gonorrhoeae
and
Neisseria meningitidis
Authors: Dillard Joseph P. , Hackett Kathleen T.
Published: August 2005

Neisseria gonorrhoeae
acetylates its cell wall peptidoglycan (PG) at the C-6 position on
N
-acetylmuramic acid. To understand the effects of PG acetylation on PG metabolism and release of PG fragments, we have made mutations in the genes responsible for PG acetylation. An insertion mutation in a putative PG acetylase gene (designated
pacA
) resulted in loss of PG acetylation as detected by a high-performance liquid chromatography-based assay. Sequence analysis of a naturally occurring nonacetylating strain revealed the presence of a 26-bp deletion in
pacA
. Introduction of the deletion mutation into wild-type gonococci resulted in lack of acetylation, and the phenotype was complemented by the addition of a wild-type copy of
pacA
at a distant location on the chromosome. Mutations were also introduced into three genes downstream of
pacA
. The gene directly downstream of
pacA
was required for acetylation and was designated
pacB
, whereas the next two genes were not required. Sequences highly similar to
pacA
and
pacB
were also found in
N. meningitidis
and
N. lactamica
strains, and an insertion in the meningococcal
pacA
eliminated PG acetylation. Phenotypic analyses of an
N. gonorrhoeae pacA
mutant did not show any decrease in lysozyme resistance or serum resistance, and the release of PG fragments during growth was unchanged. However, purified PG from the wild-type strain was significantly more resistant to the action of human lysozyme than was PG purified from the
pacA
mutant. Interestingly, the
pacA
mutant was more sensitive to EDTA, a compound known to trigger autolysis.
Interaction of
Bartonella henselae
with Endothelial Cells Promotes Monocyte/Macrophage Chemoattractant Protein 1 Gene Expression and Protein Production and Triggers Monocyte Migration
Authors: McCord Amy M. , Burgess Andrew W. O. , Whaley Melissa J. , Anderson Burt E.
Published: August 2005

Bacillary angiomatosis (BA), one of the many clinical manifestations resulting from infection with the facultative intracellular bacterium
Bartonella henselae
, is characterized by angiogenic lesions. Macrophages have been identified as important effector cells contributing to the angiogenic process during
B. henselae
infection by infiltrating BA lesions and secreting vascular endothelial growth factor. Monocyte-macrophage chemoattractant protein 1 (MCP-1) recruits macrophages to sites of inflammation. In this study, we investigated the ability of
B. henselae
to upregulate MCP-1 gene expression and protein production in the human microvascular endothelial cell line HMEC-1. MCP-1 mRNA was induced at 6 and 24 h after treatment with bacteria, whereas protein production was elevated at 6, 24, and 48 h. This induction was not dependent on the presence of bacterial lipopolysaccharide or endothelial cell toll-like receptor 4. However, MCP-1 production was dependent on NF-κB activity. Outer membrane proteins of low molecular weight were able to upregulate MCP-1 production. Furthermore, supernatants from
B. henselae
-infected HMEC-1 were able to induce chemotaxis of THP-1 monocytes. These data suggest a mechanism by which the macrophage effector cell is recruited to the endothelium during
B. henselae
infection and then contributes to bacterial-induced angiogenesis.
Humoral and Cell-Mediated Adaptive Immune Responses Are Required for Protection againstBurkholderia pseudomalleiChallenge and Bacterial Clearance Postinfection
Authors: Healey Gareth D. , Elvin Stephen J. , Morton Margaret , Williamson E. Diane
Published: August 2005

Burkholderia pseudomallei, the causative agent of melioidosis, is a gram-negative bacillus endemic to areas of southeast Asia and northern Australia. Presently, there is no licensed vaccine forB. pseudomalleiand the organism is refractive to antibiotic therapy. The bacterium is known to survive and multiply inside both phagocytic and nonphagocytic host cells and may be able to spread directly from cell to cell. Current vaccine delivery systems are unlikely to induce the correct immune effectors to stimulate a protective response to the organism. In this study, we have developed a procedure to utilize dendritic cells as a vaccine delivery vector to induce cell-mediated immune responses toB. pseudomallei. Dendritic cells were produced by culturing murine bone marrow progenitor cells in medium containing granulocyte-macrophage colony-stimulating factor and tumor necrosis factor alpha. Purified dendritic cells were pulsed with heat-killed whole-cellB. pseudomalleiand used to immunize syngeneic mice. Strong cellular immune responses were elicited by this immunization method, although antibody responses were low. Booster immunizations of either a second dose of dendritic cells or heat-killedB. pseudomalleiwere administered to increase the immune response. Immunized animals were challenged with fully virulentB. pseudomallei, and protection was demonstrated in those with strong humoral and cell-mediated immunity. These results indicate the importance of both cell-mediated and humoral immune mechanisms in protection against intracellular pathogens.
Environmental Regulation and Virulence Attributes of the Ysa Type III Secretion System of
Yersinia enterocolitica
Biovar 1B
Authors: Venecia Krista , Young Glenn M.
Published: August 2005

Pathogenic biovars of
Yersinia enterocolitica
maintain the well-studied plasmid-encoded Ysc type III secretion (TTS) system, which has a definitive role in virulence.
Y. enterocolitica
biovar 1B additionally has a distinct chromosomal locus, the
Yersinia
secretion apparatus pathogenicity island (YSA PI) that encodes the Ysa TTS system. The signals to which the Ysa TTS system responds and its role in virulence remain obscure. This exploratory study was conducted to define environmental cues that promote the expression of Ysa TTS genes and to define how the Ysa TTS system influences bacterium-host interactions. Using a genetic approach, a collection of
Y. enterocolitica
Ysa TTS mutants was generated by mutagenesis with a transposon carrying promoterless
lacZYA
. This approach identified genes both within and outside of the YSA PI that contribute to Ysa TTS. Expression of these genes was regulated in response to growth phase, temperature, NaCl, and pH. Additional genetic analysis demonstrated that two regulatory genes encoding components of the YsrR-YsrS (
ysrS
) and RcsC-YojN-RcsB (
rcsB
) phosphorelay systems affect the expression of YSA PI genes and each other. The collection of Ysa TTS-defective transposon mutants, along with other strains carrying defined mutations that block Ysa and Ysc TTS, was examined for changes in virulence properties by using the BALB/c mouse model of infection. This analysis revealed that the Ysa TTS system impacts the ability of
Y. enterocolitica
to colonize gastrointestinal tissues. These results reveal facets of how
Y. enterocolitica
controls the function of the Ysa TTS system and uncovers a role for the Ysa TTS during the gastrointestinal phase of infection.