bluuebunny/crossref_metadata_2025 huggingface dataset:
Clustering of
Helicobacter pylori
VacA in Lipid Rafts, Mediated by Its Receptor, Receptor-Like Protein Tyrosine Phosphatase β, Is Required for Intoxication in AZ-521 Cells
Authors: Nakayama Masaaki , Hisatsune Jyunzo , Yamasaki Eiki , Nishi Yoshito , Wada Akihiro , Kurazono Hisao , Sap Jan , Yahiro Kinnosuke , Moss Joel , Hirayama Toshiya
Published: November 2006

Helicobacter pylori
vacuolating cytotoxin, VacA, induces multiple effects on epithelial cells through different cellular events: one involves pore formation, leading to vacuolation, mitochondrial damage, and apoptosis, and the second involves cell signaling, resulting in stimulation of proinflammatory responses and cell detachment. Our recent data demonstrated that VacA uses receptor-like protein tyrosine phosphatase β (RPTPβ) as a receptor, of which five residues (QTTQP) at positions 747 to 751 are involved in binding. In AZ-521 cells, which mainly express RPTPβ, VacA, after binding to RPTPβ in non-lipid raft microdomains on the cell surface, is localized with RPTPβ in lipid rafts in a temperature- and VacA concentration-dependent process. Methyl-β-cyclodextrin (MCD) did not block binding to RPTPβ but inhibited translocation of VacA with RPTPβ to lipid rafts and all subsequent events. On the other hand, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), which disrupts anion channels, did not inhibit translocation of VacA to lipid rafts or VacA-induced activation of p38 mitogen-activated protein (MAP) kinase, but inhibited VacA internalization followed by vacuolation. Thus, p38 MAP kinase activation did not appear to be required for internalization. In contrast, phosphatidylinositol-specific phospholipase C (PI-PLC) inhibited translocation, as well as p38 MAP kinase/ATF-2 activation, internalization, and VacA-induced vacuolation. Neither NPPB nor PI-PLC affected VacA binding to cells and to its receptor, RPTPβ. Thus, receptor-dependent translocation of VacA to lipid rafts is critical for signaling pathways leading to p38 MAP kinase/ATF-2 activation and vacuolation.
Signal Transduction and Nuclear Responses in
Staphylococcus aureus-
Induced Expression of Human β-Defensin 3 in Skin Keratinocytes
Authors: Menzies Barbara E. , Kenoyer Aimee
Published: November 2006

The human β-defensin 3 (hBD-3) is an inducible epithelial peptide antibiotic that has potent antistaphylococcal activity. Infection of skin epithelial cells with viable
Staphylococcus aureus
, a common skin pathogen, induces increased gene expression of hBD-3 and other antimicrobial peptides. The aim of this study was to identify signaling pathways and nuclear responses that contribute to the gene expression of hBD-3 in primary human keratinocytes upon contact with
S. aureus
. Increased hBD-3 peptide was observed by immunofluorescence microscopy in keratinocytes exposed to
S. aureus
and to lipoteichoic acid (LTA). Both are ligands for the cell surface Toll-like receptor 2 (TLR2), and thus the contribution of TLR2 signaling in hBD-3 expression was examined. Functional inhibition of TLR2 prior to
S. aureus
stimulation significantly decreased hBD-3 mRNA levels by 37%, attesting to the involvement of this surface receptor in the initial recognition and downstream signaling for hBD-3 expression. Treatment of keratinocytes with a p38 mitogen-activated protein kinase (MAPK) inhibitor prior to either
S. aureus
or LTA stimulation was associated with reduced hBD-3 mRNA transcripts and peptide. We also propose a role for the MAPK-regulated transcriptional activating protein 1 in
S. aureus
-induced hBD-3 gene expression. Combined, these studies indicate a role for TLR2 signaling and MAPK activation in the upregulation of hBD-3 and demonstrate the innate immune capacity of skin keratinocytes under conditions of
S. aureus
challenge to enhance the local expression of this antistaphylococcal peptide antibiotic.
Immunogenicity of aYersinia pestisVaccine Antigen Monomerized by Circular Permutation
Authors: Chalton David A. , Musson Julie A. , Flick-Smith Helen , Walker Nicola , McGregor Alistair , Lamb Heather K. , Williamson E. Diane , Miller Julie , Robinson John H. , Lakey Jeremy H.
Published: November 2006

Caf1, a chaperone-usher protein fromYersinia pestis, is a major protective antigen in the development of subunit vaccines against plague. However, recombinant Caf1 forms polymers of indeterminate size. We report the conversion of Caf1 from a polymer to a monomer by circular permutation of the gene. Biophysical evaluation confirmed that the engineered Caf1 was a folded monomer. We compared the immunogenicity of the engineered monomer with polymeric Caf1 in antigen presentation assays to CD4 T-cell hybridomas in vitro, as well as in the induction of antibody responses and protection against subcutaneous challenge withY. pestisin vivo. In C57BL/6 mice, for which the majorH-2b-restricted immunodominant CD4 T-cell epitopes were intact in the engineered monomer, immunogenicity and protective efficacy were preserved, although antibody titers were decreased 10-fold. Disruption of anH-2d-restricted immunodominant CD4 T-cell epitope during circular permutation resulted in a compromised T-cell response, a low postvaccination antibody titer, and a lack of protection of BALB/c mice. The use of circular permutation in vaccine design has not been reported previously.
Up-Regulation of Gamma Interferon Receptor Expression Due toChlamydia-Toll-Like Receptor Interaction Does Not Enhance Signal Transducer and Activator of Transcription 1 Signaling
Authors: Shirey Kari Ann , Jung Joo-Yong , Carlin Joseph M.
Published: November 2006

Gamma interferon (IFN-γ)-induced indoleamine dioxygenase (IDO), which inhibits chlamydial replication by reducing the availability of tryptophan, is up-regulated by interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α). The mechanisms by which this occurs include an increase in the synthesis of interferon regulatory factor-1 as well as a nuclear factor-κB (NF-κB)-dependent increase in the expression of IFN-γ receptors (IFN-γR). AlthoughChlamydiais susceptible to IDO, it up-regulates IFN-γR expression to a greater degree than either IL-1β or TNF-α, perhaps through interaction with Toll-like receptors (TLR). The purpose of this study was to determine the mechanism by whichChlamydia psittaciup-regulates IFN-γR expression and evaluate this effect on IDO induction. Infection of HEK 293 cells withC. psittaciincreased IFN-γR expression only in cells expressing either TLR2 or TLR4 and the adaptor protein MD-2. In addition, up-regulation of IFN-γR expression inChlamydia-infected HeLa cells could be blocked either by neutralizing TLRs with anti-TLR2 and/or anti-TLR4 or by inhibiting NF-κB transactivation with a proteasome inhibitor. Although the newly expressed IFN-γR inChlamydia-infected cells were capable of binding IFN-γ, they did not enhance IFN-γ-induced IDO activity in a manner similar to those observed for IL-1β and TNF-α. Instead, IDO activation inChlamydia-infected cells was no different than that induced in uninfected cells, despite the increase in IFN-γR expression. Furthermore, the amount of IFN-γ-induced signal transducer and activator of transcription 1 (STAT-1) activation in infected cells paralleled that observed in uninfected cells, suggesting that STAT-1 activation by these newly expressed receptors was impaired.
Differences in the Growth of Paired Ugandan Isolates ofMycobacterium tuberculosiswithin Human Mononuclear Phagocytes Correlate with Epidemiological Evidence of Strain Virulence
Authors: Theus Sue A. , Cave M. Donald , Eisenach Kathleen , Walrath Jessica , Lee Hung , Mackay Wilma , Whalen Christopher , Silver Richard F.
Published: November 2006

Previous studies have suggested that isolates ofMycobacterium tuberculosisresponsible for tuberculosis outbreaks grow more rapidly within human mononuclear phagocytes than do other isolates. Clinical scenarios suggesting virulence of specificM. tuberculosisisolates are readily identified. Determination of appropriate “control” isolates for these studies is more problematic, but equally important for validating these assays and, ultimately, for identifying biologic differences betweenM. tuberculosisstrains that contribute to virulence. We utilized the database from a study of Ugandan tuberculosis patients and their household (HH) contacts to identifyM. tuberculosisisolates transmitted within HH and nontransmitted control isolates. Isolate pairs were evaluated from matched HH in each of three clinical scenarios: (i) coprevalent disease and no disease, (ii) incident disease and no disease, and (iii)M. tuberculosisinfection (purified protein derivative [PPD] positive) and no infection (PPD negative). Intracellular growth of paired organisms was determined in a blinded fashion using two models of intracellular infection in which we have previously demonstrated correlation between intracellular growth and strain virulence, primary human monocytes (MN) and THP-1 human macrophage-like cells. In both models, transmitted isolates from coprevalent disease HH displayed more rapid growth than nontransmitted control isolates. In the THP-1 model, this was also true of transmitted isolates from HH with incident disease and their controls. Differences in production of tumor necrosis factor alpha and interleukin-10 by matched isolates showed correlation with growth patterns in the THP-1 cells but not in MN. Paired isolates characterized in this manner may be of particular interest for further investigations of the virulence ofM. tuberculosis.
Expression ofPseudomonas aeruginosaToxin ExoS Effectively Induces Apoptosis in Host Cells
Authors: Jia Jinghua , Wang Yanping , Zhou Lei , Jin Shouguang
Published: November 2006

Pseudomonas aeruginosais an opportunistic bacterial pathogen that primarily infects immunocompromised individuals and patients with cystic fibrosis. Invasive strains ofP. aeruginosaare known to induce apoptosis at a high frequency in HeLa cells and in many other cell lines, a process that is dependent on the ADP-ribosylation (ADPRT) activity of a type III secreted protein ExoS. In our previous report, it was proposed thatP. aeruginosasecreting ExoS, upon infection, shuts down host cell survival signal pathways by inhibiting ERK1/2 and p38 activation, and it activates proapoptotic pathways through activation of JNK1/2, leading ultimately to cytochromecrelease and activation of caspases. In this study, we demonstrate that the expression of ExoS in HeLa cells by eukaryotic expression vector effectively caused apoptosis in an ADPRT activity-dependent manner, indicating that ExoS alone is sufficient to trigger apoptotic death of host cells independent of any other bacterial factors. By expressing an EGFP-ExoS fusion protein, we were able to directly correlate the death of HeLa cells with the presence of intracellular ExoS and further proved the dependence of this process on both JNK activation and mitochondrial proapoptotic event. The cellular pathway responsible for the ExoS-induced cytotoxicity appears to be well conserved, since the expression of the ADPRT-competent ExoS also induced rapid cell death in theDrosophila melanogasterS2 cell lines. The presented study not only highlights the ability of ExoS ADPRT to modulate host cell signaling, eventually leading to apoptosis, but also establishes ExoS as a valuable tool, in principle, for the elucidation of apoptosis mechanisms.
GliZ, a Transcriptional Regulator of Gliotoxin Biosynthesis, Contributes toAspergillus fumigatusVirulence
Authors: Bok Jin Woo , Chung DaWoon , Balajee S. Arunmozhi , Marr Kieren A. , Andes David , Nielsen Kristian Fog , Frisvad Jens C. , Kirby Katharine A. , Keller Nancy P.
Published: November 2006

Gliotoxin is a nonribosomal peptide produced byAspergillus fumigatus. This compound has been proposed as anA. fumigatusvirulence factor due to its cytotoxic, genotoxic, and apoptotic properties. Recent identification of the gliotoxin gene cluster identified several genes (gligenes) likely involved in gliotoxin production, includinggliZ, encoding a putative Zn2Cys6binuclear transcription factor. Replacement ofgliZwith a marker gene (ΔgliZ) resulted in no detectable gliotoxin production and loss of gene expression of otherglicluster genes. Placement of multiple copies ofgliZin the genome increased gliotoxin production. Using endpoint survival data, theΔgliZand a multiple-copygliZstrain were not statistically different from the wild type in a murine pulmonary model; however, both the wild-type and the multiple-copygliZstrain were more virulent thanΔlaeA(a mutant reduced in production of gliotoxin and other toxins). A flow-cytometric analysis of polymorphonuclear leukocytes (PMNs) exposed to supernatants from wild-type,ΔgliZ, complementedΔgliZ, andΔlaeAstrains supported a role for gliotoxin in apoptotic but not necrotic PMN cell death. This may indicate that several secondary metabolites are involved inA. fumigatusvirulence.
Both Influenza-Induced Neutrophil Dysfunction and Neutrophil-Independent Mechanisms Contribute to Increased Susceptibility to a SecondaryStreptococcus pneumoniaeInfection
Authors: McNamee Lynnelle A. , Harmsen Allen G.
Published: November 2006

Since secondaryStreptococcus pneumoniaeinfections greatly increase the mortality of influenza infections, we determined the relative roles of neutrophil-dependent and -independent mechanisms in increased susceptibility toS. pneumoniaeduring influenza infection. Mice infected with influenza for 6 days, but not 3 days, showed a significant increase in susceptibility toS. pneumoniaeinfection compared to mice not infected with influenza. There was significant neutrophil accumulation in the lungs ofS. pneumoniae-infected mice regardless of whether or not they were infected with influenza for 3 or 6 days. Depletion of neutrophils in these mice resulted in increased susceptibility toS. pneumoniaein both the non-influenza-infected mice and mice infected with influenza for 3 days but not in the mice infected with influenza for 6 days, indicating that a prior influenza infection of 6 days may compromise neutrophil function, resulting in increased susceptibility to aS. pneumoniaeinfection. Neutrophils from the lungs of mice infected with influenza for 3 or 6 days exhibited functional impairment in the form of decreased phagocytosis and intracellular reactive oxygen species generation in response toS. pneumoniae. In addition, neutrophil-depleted mice infected with influenza for 6 days were more susceptible toS. pneumoniaethan neutrophil-depleted mice not infected with influenza, indicating that neutrophil-independent mechanisms also contribute to influenza-induced increased susceptibility toS. pneumoniae. Pulmonary interleukin-10 levels were increased in coinfected mice infected with influenza for 6 days but not 3 days. Thus, an influenza infection of 6 days increases susceptibility toS. pneumoniaeby both suppression of neutrophil function and by neutrophil-independent mechanisms such as enhanced cytokine production.
A Recombinant Attenuated
Salmonella enterica
Serovar Typhimurium Vaccine Encoding
Eimeria acervulina
Antigen Offers Protection against
E. acervulina
Challenge
Authors: Konjufca Vjollca , Wanda Soo-Young , Jenkins Mark C. , Curtiss Roy
Published: November 2006

Coccidiosis is a ubiquitous disease caused by intestinal protozoan parasites belonging to several distinct species of the genus
Eimeria
. Cell-mediated immunity (CMI) is critically important for protection against
Eimeria
; thus, our approach utilizes the bacterial type III secretion system (TTSS) to deliver an antigen directly into the cell cytoplasm of the immunized host and into the major histocompatibility complex class I antigen-processing pathway for induction of CMI and antigen-specific cytotoxic T-lymphocyte responses in particular. To accomplish this goal,
Eimeria
genes encoding the sporozoite antigen EASZ240 and the merozoite antigen EAMZ250 were fused to the
Salmonella enterica
serovar Typhimurium effector protein gene
sptP
in the parental pYA3653 vector, yielding pYA3657 and pYA3658, respectively. SptP protein is secreted by the TTSS of
Salmonella
and translocated into the cytoplasm of immunized host cells. The host strain chromosomal copy of the
sptP
gene was deleted and replaced by a reporter gene,
xylE
. The newly constructed vectors pYA3657 and pYA3658 were introduced into host strain χ8879 (Δ
phoP233
Δ
sptP1033
::
xylE
Δ
asdA16
). This strain is an attenuated derivative of the highly virulent strain UK-1. When strain χ8879(pYA3653) as the vector control and strain χ8879 harboring pYA3657 or pYA3658 were used to orally immunize day-of-hatch chicks, colonization of the bursa, spleen, and liver was observed, with peak titers 6 to 9 days postimmunization. In vitro experiments show that the EASZ240 antigen is secreted into the culture supernatant via the TTSS and that it is delivered into the cytoplasm of Int-407 cells by the TTSS. In vivo experiments indicate that both humoral and cell-mediated immune responses are induced in chickens vaccinated with a recombinant attenuated
Salmonella
serovar Typhimurium vaccine, which leads to significant protection against
Eimeria
challenge.
The Frequency of BDCA3-Positive Dendritic Cells Is Increased in the Peripheral Circulation of Kenyan Children with Severe Malaria
Authors: Urban Britta C. , Cordery Damien , Shafi Mohammed J. , Bull Peter C. , Newbold Christopher I. , Williams Thomas N. , Marsh Kevin
Published: November 2006

The ability of
Plasmodium falciparum
-infected erythrocytes to adhere to host endothelial cells via receptor molecules such as ICAM-1 and CD36 is considered a hallmark for the development of severe malaria syndromes. These molecules are also expressed on leukocytes such as dendritic cells. Dendritic cells are antigen-presenting cells that are crucial for the initiation of adaptive immune responses. In many human diseases, their frequency and function is perturbed. We analyzed the frequency of peripheral blood dendritic cell subsets and the plasma concentrations of interleukin-10 (IL-10) and IL-12 in Kenyan children with severe malaria and during convalescence and related these parameters to the adhesion phenotype of the acute parasite isolates. The frequency of CD1c
+
dendritic cells in children with acute malaria was comparable to that in healthy controls, but the frequency of BDCA3
+
dendritic cells was significantly increased. Analysis of the adhesion phenotypes of parasite isolates revealed that adhesion to ICAM-1 was associated with the frequency of peripheral blood CD1c
+
dendritic cells, whereas the adhesion of infected erythrocytes to CD36 correlated with high concentrations of IL-10 and low concentrations of IL-12 in plasma.
Neutrophil Elastase, an Innate Immunity Effector Molecule, Represses Flagellin Transcription in
Pseudomonas aeruginosa
Authors: Sonawane Avinash , Jyot Jeevan , During Russell , Ramphal Reuben
Published: November 2006

Recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors triggers an innate immune response to colonizing or invading bacteria. Conversely, many bacteria have evolved mechanisms to dampen this response by downregulating the synthesis of such PAMPs. We have previously demonstrated that
Pseudomonas aeruginosa
growing in mucopurulent human respiratory mucus from cystic fibrosis patients represses the expression of its flagellin, a potent stimulant of the innate immune response. Here we demonstrate that this phenomenon occurs in response to the presence of neutrophil elastase in such mucus. Nonpurulent mucus from animals had no such repressive effect. Furthermore, lysed neutrophils from human blood reproduced the flagellin-repressive effect ex mucus and, significantly, had no effect on the viability of this organism. Neutrophil elastase, a component of the innate host defense system, has been described to be bactericidal for gram-negative bacteria and to degrade bacterial virulence factors. Thus, the resistance of
P. aeruginosa
to the bactericidal effect of neutrophil elastase, as well as this organism's ability to sense this enzyme's presence and downregulate the synthesis of a PAMP, may be the key factors in allowing
P. aeruginosa
to colonize the lungs. These findings demonstrate the dynamic nature of this bacterium's response to host defenses that ensures its success as a colonizer and also highlights the dual nature of defense molecules that confer advantages and disadvantages to both hosts and pathogens.
Lack of In Vitro and In Vivo Recognition of
Francisella tularensis
Subspecies Lipopolysaccharide by Toll-Like Receptors
Authors: Hajjar Adeline M. , Harvey Megan D. , Shaffer Scott A. , Goodlett David R. , Sjöstedt Anders , Edebro Helen , Forsman Mats , Byström Mona , Pelletier Mark , Wilson Christopher B. , Miller Samuel I. , Skerrett Shawn J. , Ernst Robert K.
Published: November 2006

Francisella tularensis
is an intracellular gram-negative bacterium that is highly infectious and potentially lethal. Several subspecies exist of varying pathogenicity. Infection by only a few organisms is sufficient to cause disease depending on the model system. Lipopolysaccharide (LPS) of gram-negative bacteria is generally recognized by Toll-like receptor 4 (TLR4)/MD-2 and induces a strong proinflammatory response. Examination of human clinical
F. tularensis
isolates revealed that human virulent type A and type B strains produced lipid A of similar structure to the nonhuman model pathogen of mice,
Francisella novicida. F. novicida
LPS or lipid A is neither stimulatory nor an antagonist for human and murine cells through TLR4 or TLR2. It does not appear to interact with TLR4 or MD-2, as it is not an antagonist to other stimulatory LPS. Consistent with these observations, aerosolization of
F. novicida
LPS or whole bacteria induced no inflammatory response in mice. These results suggest that poor innate recognition of
F. tularensis
allows the bacterium to evade early recognition by the host innate immune system to promote its pathogenesis for mammals.
Differential Role of CbpA and PspA in Modulation of In Vitro CXC Chemokine Responses of Respiratory Epithelial Cells to Infection with
Streptococcus pneumoniae
Authors: Graham Rikki M. A. , Paton James C.
Published: November 2006

Respiratory epithelial cells play an active part in the host response to respiratory pathogens, such as
Streptococcus pneumoniae
, by releasing chemokines responsible for neutrophil recruitment. In order to investigate the role of specific pneumococcal virulence factors in eliciting CXC chemokine responses, type II pneumocytes (A549) and nasopharyngeal cells (Detroit-562) were infected with
S. pneumoniae
D39 or mutants lacking choline-binding protein A (CbpA), pneumococcal surface protein A (PspA), or specific domains thereof. In response to wild-type D39, both A549 and Detroit-562 cells showed a significant increase in CXC chemokine mRNA and interleukin-8 protein. This response was increased twofold when a
cbpA
deletion mutant (ΔCbpA) was used, suggesting that CbpA inhibits CXC chemokine induction. All three N-terminal domains of CbpA are required for this effect, as in-frame deletion of the respective region of
cbpA
had the same effect on the CXC chemokine response as deletion of
cbpA
altogether. Infection with a
pspA
deletion mutant (ΔPspA) led to a twofold decrease in the CXC chemokine response of A549 but not Detroit-562 cells, compared to infection with D39 at 2 h. Thus, PspA appears to have the ability to stimulate early CXC chemokine release from A549 cells. Deletion of the region of
pspA
encoding the first N-terminal α-helical domain reduced the ability of
S. pneumoniae
to elicit a chemokine response to the same degree as deletion of
pspA
altogether. Thus, the N termini of CbpA and PspA exert differential effects on CXC chemokine induction in epithelial cells infected with
S. pneumoniae
.
Disruption of Tight Junctions and Induction of Proinflammatory Cytokine Responses in Colonic Epithelial Cells by
Campylobacter jejuni
Authors: Chen Ming L. , Ge Zhongming , Fox James G. , Schauer David B.
Published: November 2006

Campylobacter jejuni
is a leading cause of human enterocolitis and is associated with postinfectious complications, including irritable bowel syndrome and Guillain-Barré syndrome. However, the pathogenesis of
C. jejuni
infection remains poorly understood. Paracellular pathways in intestinal epithelial cells are gated by intercellular junctions (tight junctions and adherens junctions), providing a functional barrier between luminal microbes and host immune cells in the lamina propria. Here we describe alterations in tight junctions in intestinal epithelial monolayers following
C. jejuni
infection. Apical infection of polarized T84 monolayers caused a time-dependent decrease in transepithelial electrical resistance (TER). Immunofluorescence microscopy revealed a redistribution of the tight junctional transmembrane protein occludin from an intercellular to an intracellular location. Subcellular fractionation using equilibrium sucrose density gradients demonstrated decreased hyperphosphorylated occludin in lipid rafts, Triton X-100-soluble fractions, and the Triton X-100-insoluble pellet following apical infection. Apical infection with
C. jejuni
also caused rapid activation of NF-κB and AP-1, phosphorylation of extracellular signal-regulated kinase, Jun N-terminal protein kinase, and p38 mitogen-activated protein kinases, and basolateral secretion of the CXC chemokine interleukin-8 (IL-8). Basolateral infection with
C. jejuni
caused a more rapid decrease in TER, comparable redistribution of tight-junction proteins, and secretion of more IL-8 than that seen with apical infection. These results suggest that compromised barrier function and increased chemokine expression contribute to the pathogenesis of
C. jejuni
-induced enterocolitis.
The SecA2 Secretion Factor ofMycobacterium tuberculosisPromotes Growth in Macrophages and Inhibits the Host Immune Response
Authors: Kurtz Sherry , McKinnon Karen P. , Runge Marschall S. , Ting Jenny P.-Y. , Braunstein Miriam
Published: November 2006

The SecA protein is present in all bacteria, and it is a central component of the general Sec-dependent protein export pathway. An unusual property ofMycobacterium tuberculosisis the presence of two SecA proteins: SecA1, the essential “housekeeping” SecA, and SecA2, the accessory secretion factor. Here, we report that a ΔsecA2mutant ofM. tuberculosiswas defective for growth in the early stages of low-dose aerosol infection of C57BL/6 mice, a time during which the bacillus is primarily replicating in macrophages. Consistent with this in vivo phenotype, we found that the ΔsecA2mutant was defective for growth in macrophages from C57BL/6 mice. The ΔsecA2mutant was also attenuated for growth in macrophages from phox−/−mice and from NOS2−/−mice. These mice are defective in the reactive oxygen intermediate (ROI)-generating phagocyte oxidase and the reactive nitrogen intermediate (RNI)-generating inducible nitric oxide synthase, respectively. This indicated a role for SecA2 in the intracellular growth ofM. tuberculosisthat is independent of protecting against these ROIs or RNIs. Macrophages infected with the ΔsecA2mutant produced higher levels of tumor necrosis factor alpha, interleukin-6, RNI, and gamma interferon-induced major histocompatibility complex class II. This demonstrated a function forM. tuberculosisSecA2 in suppressing macrophage immune responses, which could explain the role of SecA2 in intracellular growth. Our results provide another example of a relationship betweenM. tuberculosisvirulence and inhibition of the host immune response.
Rapid Onset of Ulcerative Typhlocolitis in B6.129P2-IL10

tm1Cgn

(IL-10
−/−
) Mice Infected with
Helicobacter trogontum
Is Associated with Decreased Colonization by Altered Schaedler's Flora
Authors: Whary M. T. , Danon S. J. , Feng Y. , Ge Z. , Sundina N. , Ng V. , Taylor N. S. , Rogers A. B. , Fox J. G.
Published: November 2006

Infection with
Helicobacter trogontum
, a urease-positive helicobacter isolated from subclinically infected rats, was evaluated in B6.129P2-IL10

tm1Cgn

(interleukin-10
−/−
[IL-10
−/−
]) and C57BL/6 (B6) mice. In a first experiment, IL-10
−/−
mice naturally infected with
Helicobacter rodentium
had subclinical typhlocolitis but developed severe diarrhea and loss of body condition with erosive to ulcerative typhlocolitis within 1 to 3 weeks of experimental infection with
H. trogontum
. A second experiment demonstrated that helicobacter-free IL-10
−/−
mice dosed with
H. trogontum
also developed severe clinical signs and typhlocolitis within 2 to 4 weeks, whereas B6 mice colonized with
H. trogontum
were resistant to disease. In a third experiment, using helicobacter-free IL-10
−/−
mice, dosing with
H. trogontum
resulted in acute morbidity and typhlocolitis within 8 days. Acute typhlocolitis was accompanied by signs of sepsis supported by degenerative hemograms and recovery of
Escherichia coli
and
Proteus
spp. from the livers of infected mice. Quantitative PCR data revealed that
H. rodentium
and
H. trogontum
may compete for colonization of the lower bowel, as
H. trogontum
established higher colonization levels in the absence of
H. rodentium
(
P
< 0.003).
H. trogontum
-induced typhlocolitis was also associated with a significant decrease in the levels of colonization by five of eight anaerobes that comprise altered Schaedler's flora (
P
< 0.002). These results demonstrate for the first time that
H. rodentium
infection in IL-10
−/−
mice causes subclinical typhlocolitis and that infection with
H. trogontum
(with or without
H. rodentium
) induces a rapid-onset, erosive to ulcerative typhlocolitis which impacts the normal anaerobic flora of the colon and increases the risk of sepsis.
Dual Role of MyD88 in Rapid Clearance of Relapsing FeverBorreliaspp
Authors: Bolz Devin D. , Sundsbak Rhianna S. , Ma Ying , Akira Shizuo , Weis John H. , Schwan Tom G. , Weis Janis J.
Published: November 2006

Relapsing feverBorreliaspp. undergo antigenic variation, achieve high levels in blood, and require rapid production of immunoglobulin M (IgM) for clearance. MyD88-deficient mice display defective clearance of many pathogens; however, the IgM response to persistent infection is essentially normal. Therefore, MyD88−/−mice provided a unique opportunity to study the effect of nonantibody, innate host defenses to relapsing feverBorrelia. Infected MyD88−/−mice harbored extremely high levels ofB. hermsiiin the blood compared to wild-type littermates. In the comparison of MyD88−/−mice and B- and T-cell-deficientscidmice, two features stood out: (i) bacterial numbers in blood were at least 10-fold greater in MyD88−/−mice thanscidmice, even though the production of IgM still occurred in MyD88−/−mice; and (ii) many of the MyD88−/−mice were able to exert partial clearance, although with delayed kinetics relative to wild-type mice, a feature not seen inscidmice. Further analysis revealed a delay in the IgM response to lipoproteins expressed by the original inoculum; however, by 6 days of infection antibodies were produced in MyD88−/−mice that could clear spirochetemia inscidmice. While these results indicated that the production of IgM was delayed in MyD88−/−mice, they also point to a second, antibody-independent role for MyD88 signaling in host defense to relapsing feverBorrelia. This second defect was apparent only when antibody levels were limiting.
Microneedle-Based Intradermal Delivery of the Anthrax Recombinant Protective Antigen Vaccine
Authors: Mikszta John A. , Dekker John P. , Harvey Noel G. , Dean Cheryl H. , Brittingham John M. , Huang Joanne , Sullivan Vincent J. , Dyas Beverly , Roy Chad J. , Ulrich Robert G.
Published: November 2006

The recombinant protective antigen (rPA) of
Bacillus anthracis
is a promising anthrax vaccine. We compared serum immunoglobulin G levels and toxin-neutralizing antibody titers in rabbits following delivery of various doses of vaccine by microneedle-based intradermal (i.d.) delivery or intramuscular (i.m.) injection using conventional needles. Intradermal delivery required less antigen to induce levels of antibody similar to those produced via i.m. injection during the first 2 weeks following primary and booster inoculation. This dose-sparing effect was less evident at the later stages of the immune response. Rabbits immunized i.d. with 10 μg of rPA displayed 100% protection from aerosol spore challenge, while i.m. injection of the same dose provided slightly lower protection (71%). Groups immunized with lower antigen doses were partially protected (13 to 29%) regardless of the mode of administration. Overall, our results suggest rPA formulated with aluminum adjuvant and administered to the skin by a microneedle-based device is as efficacious as i.m. vaccination.
Single Nucleotide Polymorphism in the Cytolethal Distending Toxin B Gene Confers Heterogeneity in the Cytotoxicity of
Actinobacillus actinomycetemcomitans
Authors: Nishikubo Shuichi , Ohara Masaru , Ikura Masae , Katayanagi Katsuo , Fujiwara Tamaki , Komatsuzawa Hitoshi , Kurihara Hidemi , Sugai Motoyuki
Published: November 2006

Clinical
Actinobacillus actinomycetemcomitans
produces cytolethal distending toxin (CDT) with titers ranging from 10
2
to 10
8
U/mg. Single nucleotide polymorphism analysis of the
cdt
gene in clinical isolates identified a variation of a single amino acid at residue 281 of CdtB, which significantly affected CDT toxicity by modulating the chromatin-degrading activity of CdtB.
High diversity of fungi recovered from the roots of mature tanoak (Lithocarpus densiflorus) in northern California
Authors: Bergemann S.E. , Garbelotto M.
Published: November 2006

We collected mature tanoak ( Lithocarpus densiflorus (Hook. & Arn.) Rehder) roots from five stands to characterize the relative abundance and taxonomic richness of root-associated fungi. Fungi were identified using polymerase chain reaction (PCR), cloning, and sequencing of internal transcribed spacer (ITS) and 28S rDNA. A total of 382 cloned PCR inserts were successfully sequenced and then classified into 119 taxa. Of these taxa, 82 were basidiomycetes, 33 were ascomycetes, and 4 were zygomycetes. Thirty-one of the ascomycete sequences were identified as Cenococcum geophilum Fr. with overall richness of 22 ITS types. Other ascomycetes that form mycorrhizal associations were identified including Wilcoxina and Tuber as well as endophytes such as Lachnum , Cadophora , Phialophora , and Phialocephela . The most abundant mycorrhizal groups were Russulaceae ( Lactarius , Macowanites , Russula ) and species in the Thelephorales ( Bankera , Boletopsis , Hydnellum , Tomentella ). Our study demonstrates that tanoak supports a high diversity of ectomycorrhizal fungi with comparable species richness to that observed in Quercus root communities.
Energy balance, organellar redox status, and acclimation to environmental stress
Authors: Wilson Kenneth E. , Ivanov Alexander G. , Öquist Gunnar , Grodzinski Bernard , Sarhan Fathey , Huner Norman P.A.
Published: November 2006

In plants and algal cells, changes in light intensity can induce intrachloroplastic and retrograde regulation of gene expression in response to changes in the plastoquinone redox status. We review the evidence in support of the thesis that the chloroplast acts as a general sensor of cellular energy imbalance sensed through the plastoquinone pool. Alteration in cellular energy balance caused by chloroplast or mitochondrial metabolism can induce intracellular signalling to affect chloroplastic and nuclear gene expression in response, not only to light intensity, but to a myriad of abiotic stresses. In addition, this chloroplastic redox sensing also appears to have a broader impact, affecting long-distance systemic signalling related to plant growth and development. The organization of the respiratory electron transport chains of mitochondria and heterotrophic prokaryotes is comparable to that of chloroplast thylakoid membranes, and the redox state of the respiratory ubiquinone pool is a well-documented cellular energy sensor. Thus, modulation of electron transport component redox status by abiotic stress regulates organellar as well as nuclear gene expression. From the evidence presented, we suggest that the photosynthetic and respiratory machinery in prokaryotic and eukaryotic organisms have a dual function: primary cellular energy transformation, and global environmental sensing.
Stem and leaf growth of alpine sun and prairie shade ecotypes of Stellaria longipes under different photoperiods: role of ethylene
Authors: Walton Linda J. , Kurepin Leonid V. , Reid David M. , Chinnappa C.C.
Published: November 2006

Plant ecotypes of Stellaria longipes Goldie from competitive, shade-adapted prairie habitat and less competitive, nonshaded alpine habitat were subjected to shortened or extended photoperiod conditions. Increasing daylength was positively correlated to increased stem elongation in both ecotypes. Leaf length and area for shade (prairie) plants was significantly altered with increased photoperiods, whereas sun (alpine) plants exhibited minimal leaf expansion in response to increased photoperiod. Increased ethylene evolution in the alpine genotype during rapid stem elongation and extended photoperiods suggests that ethylene plays a growth regulatory role in this sun-adapted genotype. The prairie genotype evolved less ethylene during these same periods, indicating either a diminished requirement for elevated ethylene to effect elongation and leaf expansion responses or possibly increased ethylene sensitivity because of interactions with other hormones, such as gibberellin or auxin. The sun genotype consistently produced more ethylene than the shade genotype under all photoperiod treatments. We conclude that photoperiod alters stem elongation and leaf expansion responses; similar trends were observed for extended photoperiods as were observed for shaded conditions, specifically low light intensity (photosynthetically active radiation) conditions. Further, ethylene levels altered during these responses, especially in sun-adapted alpine plants, which suggests that ethylene is involved in these growth responses.
SURFACE CHARACTERIZATION OF Ni-Ti ALLOY MODIFIED BY ISOTHERMAL OXIDATION
Authors: SUGAWARA HIROKATSU , GOTO HIROTAKE , KOMOTORI JUN
Published: November 2006

In order to improve the corrosion resistance of Ni - Ti alloys, mechanically polished Ni - Ti alloys discs were subjected to isothermal oxidation (TO) treatment in N 2-20vol.% O 2 at temperatures ranging from 300 to 800°C. TO-treated surfaces were then analyzed by Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), and X-ray electron spectroscopy (XPS). Electrochemical corrosion tests and wear tests were carried out. Ni - Ti alloys exhibited different oxidation behavior depending on the treatment temperatures. An almost Ni free layer was observed on the surface layer of the specimens treated at temperatures 500°C and above. TO-treated specimens showed a higher corrosion resistance compared to that of the untreated sample, and a higher wear resistance. Consequently, TO-treatment produced an almost nickel free smooth protective oxide layer, which might contribute to good biocompatibility.
ISOTHERMAL OXIDATION BEHAVIOR OF THE DIRECTIONALLY SOLIDIFIED Ni-BASED SUPERALLOY DZ951 AT 900, 1000 AND 1100°C
Authors: HUANG L. , GUAN H. R. , SUN X. F. , WANG Y. L.
Published: November 2006

The isothermal oxidation behavior of directionally solidified Ni -base superalloy DZ951 at 900, 1000 and 1100°C were investigated. Oxidized alloy was characterized by SEM, EDAX, XRD. A subparabolic time dependence ( n = 0.18 at 900°C and n = 0.08 at 1000°C) of the oxide growth rate was determined at relatively low temperature, while alloy nearly followed parabolic law at 1100°C ( n = 0.42). The severe composition segregation, which resulted from the solidification process, led to the formation of different scale on the dendritic and interdendritic regions at 900°C, however, this difference disappeared after oxidation at 1000 and 1100°C for long time. Furthermore, faceted and needle-shaped AlN precipitates developed in the alloy subsurface region after oxidation at 1100°C for 200h, while no internal corrosion products were found in 900 and 1000°C tests.
THE EFFECT OF COATING THICKNESS ON FATIGUE PROPERTIES OF STEEL THERMALLY SPRAYED WITH Ni-BASED SELF-FLUXING ALLOY
Authors: AKEBONO HIROYUKI , KOMOTORI JUN , SUZUKI HIDETO
Published: November 2006

The Thermal spraying is one of the most popular surface coating techniques. To achieve the most efficient use of this technique in practice, it is very important to clarify the fatigue properties of steel coated with a thermal spray coating. In this study, to clarify the effects of coating thickness on the fatigue properties of the steel substrate, three types of sprayed specimens with different coating thickness (0.2, 0.5 and 1.0mm) were prepared and fatigue tests were carried out. Coating thickness strongly affected the fatigue properties; the thinner the coating thickness, the higher the fatigue strength. Fatigue crack propagation behaviors were observed. Accordingly the fatigue cracks propagated through many defects on the coated surface. The sizes and number of the coating defects were determined by coating thickness; the thicker the coating thickness, the larger the defect and number. Therefore, the sprayed specimens with thinner coatings indicated higher fatigue strength. Furthermore, estimations of the fatigue strength were performed by using Murakami's equation. The fatigue strengths of thermal spray coated specimens were estimated by three parameters; (i) maximum size of coating defects estimated by statistics of extreme value, (ii) hardness of the matrix and (iii) volume fraction of coating defects.
CONTROL OF SURFACE MODIFIED LAYER ON METALLIC BIOMATERIALS BY AN ADVANCED ELID GRINDING SYSTEM (EG-X)
Authors: MIZUTANI MASAYOSHI , KOMOTORI JUN , KATAHIRA KAZUTOSHI , OHMORI HITOSHI
Published: November 2006

The biocompatibility of titanium implants with different surface properties is investigated. We prepared three types of specimens, one ground by the newly developed ELID grinding system, another ground by conventional ELID grinding, and the other polished by SiO 2 powder. These surfaces were characterized and, the number of cell and cytotoxicity in in-vitro were measured. Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscope (TEM) revealed that the modified ELID system can create a significantly thick oxide layer and a diffused oxide layer, and also can control the thickness of a modified layer. The results of cell number and cytotoxicity showed that the sample ground by the modified system had the highest biocompatibility. This may have been caused by improvement of chemical properties due to a surface modified layer. The above results suggest that this newly developed ELID grinding system can create the desirable surface properties. Consequently, this system appears to offer significant future promise for use in biomaterials and other engineering components.
Co/Cu INTERFACE ELECTRONIC STRUCTURES STUDY FROM FIRST-PRINCIPLES
Authors: SHANG JIAXIANG , ZHAO XIAODAN , ZHANG YUE , XU HUIBIN
Published: November 2006

The electronic structures of Co/Cu interface have been calculated by first-principles method based on local spin density approximation. Models 3 Co/xCu ( x =1-8 monolayers) with different Cu layer thickness are investigated. The results show that the oscillation of the density of states near the Fermi surface with the Cu spacer thickness has been observed and the period of oscillation is about 6 atom layers, which has a good agreement with the corresponding experiments. We also discuss the spin polarization and magnetic resistance with the change of Cu layers thickness. Further analysis shows majority spin states near the Fermi surface played a key role in giant magnetoresistance (GMR).
MORPHOLOGY CONTROLLING AND OPTICAL CHARACTERIZATION OF ZnO NANOMATERIALS
Authors: LV YUZHEN , LI CHUNPING , CHE PING , GUO LIN , XU HUIBIN
Published: November 2006

Wurtzite ZnO nanomaterials including nanoparticles, nanocolumns and nanorods were successfully synthesized by a solution route. Concentrations of modifying reagent and differences of solvent employed in the synthetic process can effectively adjust the morphologies of the as-grown products. Photoluminescence measurements of the ZnO nanocolumns and nanorods have been carried out at room temperature. A sharp Ultraviolet emission at 386 nm and a weak visible emission centered at 515 nm were observed in the PL spectrum of the nanocolumns, while a UV emission of the nanorods was observed at 377 nm.
INFLUENCE OF THE SiO AND SiON BUFFER LAYER ON IZO THIN FILMS DEPOSITED ON PET BY INCLINATION OPPOSITE TARGET TYPE DC MAGNETRON SPUTTERING METHOD
Authors: QIU ZHIYONG , SHIN DO-HOON , NAKADA KENJI , MURAKAMI RI-ICHI , YOON HAN-KI
Published: November 2006

IZO films were deposited onto polyethylene terephthalate (PET) substrate at room temperature by the inclination opposite target type DC magnetron sputtering equipment. In this paper, SiO or SiON thin films of about 20nm thickness were introduced as buffer layers between the IZO thin films and the PET substrate. Electrical resistivity, transmittance and surface uniformity properties were investigated. It is clear that the film surface roughness of multilayer thin films was less than that of IZO monolayer thin films. The surface average roughness ( Ra ) of the multilayer film with 230nm IZO layer thickness was about 1.6nm, and that of IZO monolayer film was 2.4nm. All of the multilayer samples had high optical transmittance (about 90%) in the visible region. Of particular note, the transmittance of multilayer films was slightly higher than that of monolayer films when the IZO layer was thicker than 200nm. High electrical conductivity was also achieved with thick films.
PREPARATION OF 1-3 CONNECTIVITY COMPOSITE FILMS OF WELL-ALIGNED ZnO WHISKER ARRAYS WITH AN ORGANIC RESIN
Authors: ZHANG YUE , ZHANG XUE-CHUAN , WANG SHU-BING
Published: November 2006

Zinc oxide whisker arrays well-aligned along [0001] direction have been grown on the substrates of glass and single crystal silicon by atmospheric metal organic chemical vapor deposition method (MOCVD). The SEM observation indicated that the whiskers were quite uniform in length and diameter. The whisker arrays were very dense, and the gap among the whiskers was less than 1 μm. The array materials were proposed as the component to prepare 1-3 piezoelectric composite film in-situ. Epoxy resin was used as the matrix materials. The key points to prepare the composites are how to make the resin enter the array and control a suitable thickness of the resin films. Several approaches were studied. The results showed that the best was the vertical sucking method. The SEM observations indicated that the thickness was well controlled as almost same as the length of the whiskers, and the resin perfectly entered the array without pore. The 1-3 piezoelectric composite film has great potential applications in micro sensor and actuator arrays.
LOW TEMPERATURE IN-SITU STRESS MEASUREMENT OF W/Cu COMPOSITE BY NEUTRON DIFFRACTION
Authors: NISHIDA MASAYUKI , MUSLIH M. RIFAI , IKEUCHI YASUKAZU , MINAKAWA NOBUAKI , HANABUSA TAKAO
Published: November 2006

The internal stresses in the continuous tungsten-fiber reinforced copper-matrix composite were examined by the Neutron stress measurement method. The Neutron diffraction apparatus ND1, which is abbreviated from the Neutron Diffraction system No.1 designed and manufactured by the National Nuclear Energy Agency in Indonesia (Badan Tenage Nuklir Nasional, BATAN), was used in the present study. The most common 3-axes measurement method with Hooke's equation was used to measure stresses in the both of tungsten-fiber and copper-matrix. The tungsten-fiber became the situation of heavy 110 priority orientation. The other hand, copper-matrix became the large crystal grain. Thermal stress alterations caused form low temperature cycling was measured by in-situ stress measurement method making use of a cryostat system. The thermal residual stresses of tungsten-fiber and copper-matrix in longitudinal direction were compressive and tensile state respectively. Results of in-situ thermal stress measurement were agreed with a calculated result of simple elastic theory qualitatively.