bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of Quinoxaline-2-Carboxylate 1,4-Di-
N
-Oxide Derivatives in Experimental Tuberculosis
Authors: Vicente Esther , Villar Raquel , Burguete Asunción , Solano Beatriz , Pérez-Silanes Silvia , Aldana Ignacio , Maddry Joseph A. , Lenaerts Anne J. , Franzblau Scott G. , Cho Sang-hyun , Monge Antonio , Goldman Robert C.
Published: July 2008

This study extends earlier reports regarding the in vitro efficacies of the 1,4-di-
N
-oxide quinoxaline derivatives against
Mycobacterium tuberculosis
and has led to the discovery of a derivative with in vivo efficacy in the mouse model of tuberculosis. Quinoxaline-2-carboxylate 1,4-di-
N
-oxide derivatives were tested in vitro against a broad panel of single-drug-resistant
M. tuberculosis
strains. The susceptibilities of these strains to some compounds were comparable to those of strain H
37
Rv, as indicated by the ratios of MICs for resistant and nonresistant strains, supporting the premise that 1,4-di-
N
-oxide quinoxaline derivatives have a novel mode of action unrelated to those of the currently used antitubercular drugs. Specific derivatives were further evaluated in a series of in vivo assays, including evaluations of the maximum tolerated doses, the levels of oral bioavailability, and the efficacies in a low-dose aerosol model of tuberculosis in mice. One compound, ethyl 7-chloro-3-methylquinoxaline-2-carboxylate 1,4-dioxide, was found to be (i) active in reducing CFU counts in both the lungs and spleens of infected mice following oral administration, (ii) active against PA-824-resistant
Mycobacterium bovis
, indicating that the pathway of bioreduction/activation is different from that of PA-824 (a bioreduced nitroimidazole that is in clinical trials), and (iii) very active against nonreplicating bacteria adapted to low-oxygen conditions. These data indicate that 1,4-di-
N
-oxide quinoxalines hold promise for the treatment of tuberculosis.
Cell Density and Cell Aging as Factors Modulating Antifungal Resistance ofCandida albicansBiofilms
Authors: Seneviratne C. J. , Jin L. J. , Samaranayake Y. H. , Samaranayake L. P.
Published: July 2008

Biofilm formation is a major virulence attribute ofCandidapathogenicity which contributes to higher antifungal resistance. We investigated the roles of cell density and cellular aging on the relative antifungal susceptibility of planktonic, biofilm, and biofilm-derived planktonic modes ofCandida. A reference and a wild-type strain ofCandida albicanswere used to evaluate the MICs of caspofungin (CAS), amphotericin B (AMB), nystatin (NYT), ketoconazole (KTC), and flucytosine (5FC). Standard, NCCLS, and European Committee on Antibiotic Susceptibility Testing methods were used for planktonic MIC determination.Candidabiofilms were then developed on polystyrene wells, and MICs were determined with a standard 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide assay. Subsequently, antifungal susceptibility testing was performed for greater inoculum concentrations and 24- and 48-h-old cultures of planktonicCandida. Furthermore,Candidabiofilm-derived planktonic cells (BDPC) were also subjected to antifungal susceptibility testing. The MICs for bothC.albicansstrains in the planktonic mode were low, although on increasing the inoculum concentration (up to 1 × 108cells/ml), a variable MIC was noted. On the contrary, forCandidabiofilms, the MICs of antifungals were 15- to >1,000-fold higher. Interestingly, the MICs for BDPC were lower and were similar to those for planktonic-mode cells, particularly those of CAS and AMB. Our data indicate that higher antifungal resistance ofCandidabiofilms is an intrinsic feature possibly related to the biofilm architecture rather than cellular density or cellular aging.
Surveillance for Neuraminidase Inhibitor Resistance among Human Influenza A and B Viruses Circulating Worldwide from 2004 to 2008
Authors: Sheu Tiffany G. , Deyde Varough M. , Okomo-Adhiambo Margaret , Garten Rebecca J. , Xu Xiyan , Bright Rick A. , Butler Eboneé N. , Wallis Teresa R. , Klimov Alexander I. , Gubareva Larisa V.
Published: July 2008

The surveillance of seasonal influenza virus susceptibility to neuraminidase (NA) inhibitors was conducted using an NA inhibition assay. The 50% inhibitory concentration values (IC50s) of 4,570 viruses collected globally from October 2004 to March 2008 were determined. Based on mean IC50s, A(H3N2) viruses (0.44 nM) were more sensitive to oseltamivir than A(H1N1) viruses (0.91 nM). The opposite trend was observed with zanamivir: 1.06 nM for A(H1N1) and 2.54 nM for A(H3N2). Influenza B viruses exhibited the least susceptibility to oseltamivir (3.42 nM) and to zanamivir (3.87 nM). To identify potentially resistant viruses (outliers), a threshold of a mean IC50value + 3 standard deviations was defined for type/subtype and drug. Sequence analysis of outliers was performed to identify NA changes that might be associated with reduced susceptibility. Molecular markers of oseltamivir resistance were found in six A(H1N1) viruses (H274Y) and one A(H3N2) virus (E119V) collected between 2004 and 2007. Some outliers contained previously reported mutations (e.g., I222T in the B viruses), while other mutations [e.g., R371K and H274Y in B viruses and H274N in A(H3N2) viruses) were novel. The R371K B virus outlier exhibited high levels of resistance to both inhibitors (>100 nM). A substantial variance at residue D151 was observed among A(H3N2) zanamivir-resistant outliers. The clinical relevance of newly identified NA mutations is unknown. A rise in the incidence of oseltamivir resistance in A(H1N1) viruses carrying the H274Y mutation was detected in the United States and in other countries in the ongoing 2007 to 2008 season. As of March 2008, the frequency of resistance among A(H1N1) viruses in the United States was 8.6% (50/579 isolates). The recent increase in oseltamivir resistance among A(H1N1) viruses isolated from untreated patients raises public health concerns and necessitates close monitoring of resistance to NA inhibitors.
Antimalarial Activity of a New Stilbene Glycoside from
Parthenocissus tricuspidata
in Mice
Authors: Park Won-Hwan , Lee Sung-Jae , Moon Hyung-In
Published: July 2008

A novel stilbene glycoside [piceid-(1→6)-β-
d
-glucopyranoside; PBG] from
Parthenocissus tricuspidata
was tested in vivo against
Plasmodium berghei
. PBG exhibited significant blood schizontocidal activity in a 4-day early infection, a repository evaluation, and an established infection, with a significant mean survival time comparable to that obtained with the standard drug, chloroquine (5 mg·kg
−1
·day
−1
).
Real-Time PCR and Statistical Analyses of
acrAB
and
ramA
Expression in Clinical Isolates of
Klebsiella pneumoniae
Authors: Ruzin Alexey , Immermann Frederick W. , Bradford Patricia A.
Published: July 2008

Clinical isolates of
Klebsiella pneumoniae
were tested for a correlation between tigecycline MIC and expression of
ramA
by using real-time PCR. At MICs of 4 and 8 μg/ml, the expression of
ramA
was statistically significantly different from MICs of 2 μg/ml or less, supporting the tigecycline susceptibility breakpoint of ≤2 μg/ml for
K. pneumoniae
.
Comparative In Vitro Anti-Hepatitis C Virus Activities of a Selected Series of Polymerase, Protease, and Helicase Inhibitors
Authors: Paeshuyse Jan , Vliegen Inge , Coelmont Lotte , Leyssen Pieter , Tabarrini Oriana , Herdewijn Piet , Mittendorfer Harald , Easmon Johnny , Cecchetti Violetta , Bartenschlager Ralf , Puerstinger Gerhard , Neyts Johan
Published: July 2008

We report here a comparative study of the anti-hepatitis C virus (HCV) activities of selected (i) nucleoside polymerase, (ii) nonnucleoside polymerase, (iii) α,γ-diketo acid polymerase, (iv) NS3 protease, and (v) helicase inhibitors, as well as (vi) cyclophilin binding molecules and (vii) alpha 2b interferon in four different HCV genotype 1b replicon systems.
The Commensal
Streptococcus salivarius
K12 Downregulates the Innate Immune Responses of Human Epithelial Cells and Promotes Host-Microbe Homeostasis
Authors: Cosseau Celine , Devine Deirdre A. , Dullaghan Edie , Gardy Jennifer L. , Chikatamarla Avinash , Gellatly Shaan , Yu Lorraine L. , Pistolic Jelena , Falsafi Reza , Tagg John , Hancock Robert E. W.
Published: July 2008

Streptococcus salivarius
is an early colonizer of human oral and nasopharyngeal epithelia, and strain K12 has reported probiotic effects. An emerging paradigm indicates that commensal bacteria downregulate immune responses through the action on NF-κB signaling pathways, but additional mechanisms underlying probiotic actions are not well understood. Our objective here was to identify host genes specifically targeted by K12 by comparing their responses with responses elicited by pathogens and to determine if
S. salivarius
modulates epithelial cell immune responses. RNA was extracted from human bronchial epithelial cells (16HBE14O- cells) cocultured with K12 or bacterial pathogens. cDNA was hybridized to a human 21K oligonucleotide-based array. Data were analyzed using ArrayPipe, InnateDB, PANTHER, and oPOSSUM. Interleukin 8 (IL-8) and growth-regulated oncogene alpha (Groα) secretion were determined by enzyme-linked immunosorbent assay. It was demonstrated that
S. salivarius
K12 specifically altered the expression of 565 host genes, particularly those involved in multiple innate defense pathways, general epithelial cell function and homeostasis, cytoskeletal remodeling, cell development and migration, and signaling pathways. It inhibited baseline IL-8 secretion and IL-8 responses to LL-37,
Pseudomonas aeruginosa
, and flagellin in epithelial cells and attenuated Groα secretion in response to flagellin. Immunosuppression was coincident with the inhibition of activation of the NF-κB pathway. Thus, the commensal and probiotic behaviors of
S. salivarius
K12 are proposed to be due to the organism (i) eliciting no proinflammatory response, (ii) stimulating an anti-inflammatory response, and (iii) modulating genes associated with adhesion to the epithelial layer and homeostasis.
S. salivarius
K12 might thereby ensure that it is tolerated by the host and maintained on the epithelial surface while actively protecting the host from inflammation and apoptosis induced by pathogens.
In Vivo Demonstration and Quantification of Intracellular
Bacillus anthracis
in Lung Epithelial Cells
Authors: Russell Brooke H. , Liu Qing , Jenkins Sarah A. , Tuvim Michael J. , Dickey Burton F. , Xu Yi
Published: July 2008

Inhalational anthrax is initiated by the entry of
Bacillus anthracis
spores into the lung. A critical early event in the establishment of an infection is the dissemination of spores from the lung. Using in vitro cell culture assays, we previously demonstrated that
B. anthracis
spores are capable of entering into epithelial cells of the lung and crossing a barrier of lung epithelial cells without apparent disruption of the barrier integrity, suggesting a novel portal for spores to disseminate from the lung. However, in vivo evidence for spore uptake by epithelial cells has been lacking. Here, using a mouse model, we present evidence that
B. anthracis
spores are taken up by lung epithelial cells in vivo soon after spores are delivered into the lung. Immunofluorescence staining of thin sections of lungs from spore-challenged BALB/c mice revealed that spores were associated with the epithelial surfaces in the airway and the alveoli at 2 and 4 h postinoculation. Confocal analysis further indicated that some of the associated spores were surrounded by F-actin, demonstrating intracellular localization. These observations were further confirmed and substantiated by a quantitative method that first isolated lung cells from spore-challenged mice and then stained these cells with antibodies specific for epithelial cells and spores. The results showed that substantial amounts of spores were taken up by lung epithelial cells in vivo. These data, combined with those in our previous reports, provided powerful evidence that the lung epithelia were directly targeted by
B. anthracis
spores at early stages of infection.
Characterization of Complement Factor H Binding toYersinia enterocoliticaSerotype O:3
Authors: Biedzka-Sarek Marta , Jarva Hanna , Hyytiäinen Heidi , Meri Seppo , Skurnik Mikael
Published: July 2008

A number of bacteria bind factor H (FH), the negative regulator of the alternative complement pathway, to avoid complement-mediated killing. Here we show that a gram-negative enteric pathogen,Yersinia enterocoliticaserotype O:3, uses two virulence-related outer membrane (OM) proteins to bind FH. WithY. enterocoliticaO:3 mutant strains displaying different combinations of surface factors relevant to complement resistance, we demonstrated that the major receptor for FH is the OM protein YadA. Another OM protein, Ail, also contributes to FH binding provided that it is not blocked by distal parts of the lipopolysaccharide (i.e., the O antigen and the outer core hexasaccharide). Importantly, we demonstrated that surface-bound FH was functional; both YadA- and Ail-bound FH displayed cofactor activity for factor I-mediated cleavage of C3b. With truncated recombinant FH constructs, we located the binding site of Ail specifically to short consensus repeats 6 and 7 of FH, while YadA showed a novel type of FH-binding pattern and appears to bind FH throughout the entire FH molecule. We thus conclude thatY. enterocolitica, via YadA and Ail, recruits functionally active FH to its surface. FH binding appears to be an important mechanism of the complement resistance of this pathogen.
The Failure of Immune Response Evasion by Linear Plasmid 28-1-Deficient
Borrelia burgdorferi
Is Attributable to Persistent Expression of an Outer Surface Protein
Authors: Embers Monica E. , Alvarez Xavier , Ooms Tara , Philipp Mario T.
Published: July 2008

Infectivity and persistence by
Borrelia burgdorferi
, the etiologic agent of Lyme disease, rely stringently on regulatory events. Among these is the downregulation of lipoprotein antigen expression, exemplified by outer surface protein C (OspC), at the advent of specific immunity in the mammalian host.
B. burgdorferi
spirochetes that lack the linear plasmid 28-1 (lp28-1) succumb to the host's immune response. We thus explored the notion that these two phenomena were related—that lp28-1
−
organisms fail to downregulate
ospC
and thus are cleared following the appearance of anti-OspC antibody in the murine host. The lp-28-1
−
isolate and a wild-type (wt) isolate bearing the complete set of plasmids were grown in dialysis membrane chambers that were implanted into rat peritoneal cavities. Analysis of mRNA and protein from these cultures showed that OspC expression levels by lp28-1
−
organisms are abnormally high in vivo. A time course analysis of
ospC
expression in tissues following infection indicates also that temporal diminution of the dominant antigen OspC is impaired in lp28-1
−
spirochetes. Finally, passive transfer of monoclonal OspC-specific antibody into SCID mice 8 days postinfection cleared lp28-1
−
spirochetes, yet the wt organisms persisted in a majority of animals. These findings indicate that incomplete repression of OspC by lp28-1
−
organisms renders them susceptible to immune-mediated clearance. The lp28-1 plasmid must harbor one or more genes involved in OspC downregulation.
Inhibition of
Salmonella enterica
Serovar Typhimurium Motility and Entry into Epithelial Cells by a Protective Antilipopolysaccharide Monoclonal Immunoglobulin A Antibody
Authors: Forbes Stephen J. , Eschmann Marisa , Mantis Nicholas J.
Published: July 2008

Secretory immunoglobulin A (SIgA) antibodies directed against the O antigen of lipopolysaccharide (LPS) are the primary determinants of mucosal immunity to gram-negative enteric pathogens. However, the underlying mechanisms by which these antibodies interfere with bacterial colonization and invasion of intestinal epithelial cells are not well understood. In this study, we report that Sal4, a protective, anti-O5-specific monoclonal IgA, is a potent inhibitor of
Salmonella enterica
serovar Typhimurium flagellum-based motility. Using video light microscopy, we observed that Sal4 completely and virtually instantaneously “paralyzed” laboratory and clinical strains of serovar Typhimurium. Sal4-mediated motility arrest preceded and occurred independently of agglutination. Polyclonal anti-LPS IgG antibodies and F(ab)
2
fragments were as potent as was Sal4 at impeding bacterial motility, whereas monovalent Fab fragments were 5- to 10-fold less effective. To determine whether motility arrest can fully account for Sal4's protective capacity in vitro, we performed epithelial cell infection assays in which the requirement for flagellar motility in adherence and invasion was bypassed by centrifugation. Under these conditions, Sal4-treated serovar Typhimurium cells remained noninvasive, revealing that the monoclonal IgA, in addition to interfering with motility, has an effect on bacterial uptake into epithelial cells. Sal4 did not, however, inhibit bacterial uptake into mouse macrophages, indicating that the antibody interferes specifically with
Salmonella
pathogenicity island 1 (SPI-1)-dependent, but not SPI-1-independent, entry into host cells. These results reveal a previously unrecognized capacity of SIgA to “disarm” microbial pathogens on mucosal surfaces and prevent colonization and invasion of the intestinal epithelium.
Characteristics of Biofilm Formation byStreptococcus mutansin the Presence of Saliva
Authors: Ahn Sug-Joon , Ahn Sang-Joon , Wen Zezhang T. , Brady L. Jeannine , Burne Robert A.
Published: July 2008

Interactions between salivary agglutinin and the adhesin P1 ofStreptococcus mutanscontribute to bacterial aggregation and mediate sucrose-independent adherence to tooth surfaces. We have examined biofilm formation byS. mutansUA159, and derivative strains carrying mutations affecting the localization or expression of P1, in the presence of fluid-phase or adsorbed saliva or salivary agglutinin preparations. Whole saliva- and salivary agglutinin-induced aggregation ofS. mutanswas adversely affected by the loss of P1 and sortase (SrtA) but not by the loss of trigger factor (RopA). Fluid-phase salivary agglutinin and, to a lesser extent, immobilized agglutinin inhibited biofilm development byS. mutansin the absence of sucrose, and whole saliva was more effective at decreasing biofilm formation than salivary agglutinin. Inhibition of biofilm development by salivary agglutinin was differently influenced by particular mutations, with the P1-deficient strain displaying a greater inhibition of biofilm development than the SrtA- or RopA-deficient strains. As expected, biofilm-forming capacities of all strains in the presence of salivary preparations were markedly enhanced in the presence of sucrose, although biofilm formation by the mutants was less efficient than that by the parental strain. Aeration strongly inhibited biofilm development, and the presence of salivary components did not restore biofilm formation in aerated conditions. The results disclose a potent ability of salivary constituents to moderate biofilm formation byS. mutansthrough P1-dependent and P1-independent pathways.
Outer Membrane Antigens of the UropathogenProteus mirabilisRecognized by the Humoral Response during Experimental Murine Urinary Tract Infection
Authors: Nielubowicz Greta R. , Smith Sara N. , Mobley Harry L. T.
Published: July 2008

Proteus mirabilis, a gram-negative bacterium, is a frequent cause of complicated urinary tract infections in those with functional or anatomical abnormalities or those subject to long-term catheterization. To systematically identify surface-exposed antigens as potential vaccine candidates, proteins in the outer membrane fraction of bacteria were separated by two-dimensional gel electrophoresis and subjected to Western blotting with sera from mice experimentally infected withP. mirabilis. Protein spots reactive with sera were identified by mass spectrometry, which in conjunction with the newly completed genome sequence ofP. mirabilisHI4320, was used to identify surface-exposed antigens. Culture conditions that may mimic in vivo conditions more closely than Luria broth (growth in human urine and under iron limitation and osmotic stress) were also used. Thirty-seven antigens to which a humoral response had been mounted, including 23 outer membrane proteins, were identified. These antigens are presumably expressed during urinary tract infection. Protein targets that are both actively required for virulence and antigenic may serve as protective antigens for vaccination; thus, five representative antigens were selected for use in virulence studies. Strains ofP. mirabiliswith mutations in three of the corresponding genes (the PMI0047 gene,rafY, andfadL) were not attenuated in the murine model of urinary tract infection. Putative iron acquisition proteins PMI0842 and PMI2596, however, both contribute to fitness in the urinary tract and thus emerge as vaccine candidates.
Effects of
Clostridium perfringens
Beta-Toxin on the Rabbit Small Intestine and Colon
Authors: Vidal Jorge E. , McClane Bruce A. , Saputo Juliann , Parker Jaquelyn , Uzal Francisco A.
Published: July 2008

Clostridium perfringens
type B and type C isolates, which produce beta-toxin (CPB), cause fatal diseases originating in the intestines of humans or livestock. Our previous studies demonstrated that CPB is necessary for type C isolate CN3685 to cause bloody necrotic enteritis in a rabbit ileal loop model and also showed that purified CPB, in the presence of trypsin inhibitor (TI), can reproduce type C pathology in rabbit ileal loops. We report here a more complete characterization of the effects of purified CPB in the rabbit small and large intestines. One microgram of purified CPB, in the presence of TI, was found to be sufficient to cause significant accumulation of hemorrhagic luminal fluid in duodenal, jejunal, or ileal loops treated for 6 h with purified CPB, while no damage was observed in corresponding loops receiving CPB (no TI) or TI alone. In contrast to the CPB sensitivity of the small intestine, the colon was not affected by 6 h of treatment with even 90 μg of purified CPB whether or not TI was present. Time course studies showed that purified CPB begins to induce small intestinal damage within 1 h, at which time the duodenum is less damaged than the jejunum or ileum. These observations help to explain why type B and C infections primarily involve the small intestine, establish CPB as a very potent and fast-acting toxin in the small intestines, and confirm a key role for intestinal trypsin as an innate intestinal defense mechanism against CPB-producing
C. perfringens
isolates.
Immunological Dominance of
Trypanosoma cruzi
Tandem Repeat Proteins
Authors: Goto Yasuyuki , Carter Darrick , Reed Steven G.
Published: July 2008

Proteins with tandem repeat (TR) domains have been found in various protozoan parasites, often acting as targets of B-cell responses. However, the extent of the repeats within
Trypanosoma cruzi
, the causative agent of Chagas’ disease, has not been examined well. Here, we present a systematic survey of the TR genes found in
T. cruzi
, in comparison with other organisms. Although the characteristics of TR genes varied from organism to organism, the presence of genes having large TR domains was unique to the trypanosomatids examined, including
T. cruzi
. Sequence analyses of
T. cruzi
TR genes revealed their divergency; they do not share such characteristics as sequence similarity or biased cellular location predicted by the presence of a signal sequence or transmembrane domain(s). In contrast,
T. cruzi
TR proteins seemed to possess significant antigenicity. A number of previously characterized
T. cruzi
antigens were detected by this computational screening, and several of those antigens contained a large TR domain. Further analyses of the
T. cruzi
genome demonstrated that previously uncharacterized TR proteins in this organism may also be immunodominant. Taken together,
T. cruzi
is rich in large TR domain-containing proteins with immunological significance; it is worthwhile further analyzing such characteristics of TR proteins as the copy number and consensus sequence of the repeats to determine whether they might contribute to the biological variability of
T. cruzi
strains with regard to induced immunological responses, host susceptibility, disease outcomes, and pathogenicity.
Salmonella enterica
Serovar Typhimurium NiFe Uptake-Type Hydrogenases Are Differentially Expressed In Vivo
Authors: Zbell Andrea L. , Maier Susan E. , Maier Robert J.
Published: July 2008

Salmonella enterica
serovar Typhimurium, a common enteric pathogen, possesses three NiFe uptake-type hydrogenases. The results from mouse infection studies suggest that the H
2
oxidation capacity provided by these hydrogenases is important for virulence. Since the three enzymes are similar in structure and function, it may be expected that they are utilized under different locations and times during an infection. A recombination-based method to examine promoter activity in vivo (RIVET) was used to determine hydrogenase gene expression in macrophages, polymorphonuclear leukocyte (PMN)-like cells, and a mouse model of salmonellosis. The
hyd
and
hya
promoters showed increased expression in both murine macrophages and human PMN-like cells compared to that in the medium-only controls. Quantitative reverse transcription-PCR results suggested that
hyb
is also expressed in phagocytes. A nonpolar
hya
mutant was compromised for survival in macrophages compared to the wild type. This may be due to lower tolerance to acid stress, since the
hya
mutant was much more acid sensitive than the wild type. In addition,
hya
mutant cells were internalized by macrophages the same as wild-type cells. Mouse studies (RIVET) indicate that
hyd
is highly expressed in the liver and spleen early during infection but is expressed poorly in the ileum in infected animals. Late in the infection, the
hyd
genes were expressed at high levels in the ileum as well as in the liver and spleen. The
hya
genes were expressed at low levels in all locations tested. These results suggest that the hydrogenases are used to oxidize hydrogen in different stages of an infection.
The Absence of Cutaneous Lymph Nodes Results in a Th2 Response and Increased Susceptibility toLeishmania majorInfection in Mice
Authors: Ehrchen Jan M. , Roth Johannes , Roebrock Kirsten , Varga Georg , Domschke Wolfram , Newberry Rodney , Sorg Clemens , Müller-Tidow Carsten , Sunderkötter Cord , Kucharzik Torsten , Spahn Thomas W.
Published: July 2008

Lymph nodes (LNs) are important sentinel organs where antigen-presenting cells interact with T cells to induce adaptive immune responses. In cutaneous infection of mice withLeishmania major, resistance depends on the induction of a T-helper-cell-1 (Th1)-mediated cellular immune response in draining, peripheral LNs. We investigated whether draining, peripheral LNs are absolutely required for resistance againstL. majorinfection. We investigated the course of experimental leishmaniasis in wild-type (wt) mice lacking peripheral LNs (pLNs), which we generated by in utero blockade of membrane-bound lymphotoxin, and in mice lacking pLNs or all LNs due to genetic deletion of lymphotoxin ligands or receptors. wt mice of the resistant C57BL/6 strain without local skin-draining LNs were still able to generate specific T-cell responses, but this yielded Th2 cells. This switch to a Th2 response resulted in severe systemic infection. We also confirmed these results with mice lacking pLNs due to genetic depletion of lymphotoxin-β. The complete absence of LNs due to a genetic depletion of the lymphotoxin-β receptor also resulted in a marked deterioration of disease and a Th2 response. Thus, in the absence of pLNs, anL. major-specific Th2 response is induced in the remaining secondary lymphoid organs, such as the spleen and non-skin-draining LNs. This indicates a critical requirement for pLNs to induce protective Th1 immunity and suggests that whether Th1 or Th2 priming to the same antigen occurs depends on the site of the primary antigen recognition.
EFFICIENT DESIGN OF RESIDUAL-BASED STABILIZATION TECHNIQUES FOR THE THREE FIELDS DOMAIN DECOMPOSITION METHOD
Authors: BERTOLUZZA SILVIA , FALLETTA SILVIA , MANZINI GIANMARCO
Published: July 2008

We consider a class of residual-based stabilization schemes (including the one using wavelets) for the three fields formulation of domain decomposition of elliptic boundary value problems. These schemes can be incorporated in the plain three fields formulation as an a posteriori correction that is performed at each iteration of the numerical resolution process. The crucial point is that this approach does not require any modification to the sub-domain solvers. This fact makes it possible to design an efficient numerical algorithm that solves the discrete problem resulting from the stabilized method. We demonstrate the effectiveness of this approach by several numerical experiments that also show the low computational complexity of the stabilized method and its good dependence on the stabilization parameter.
DECAY PROPERTY OF REGULARITY-LOSS TYPE AND NONLINEAR EFFECTS FOR DISSIPATIVE TIMOSHENKO SYSTEM
Authors: IDE KENTARO , KAWASHIMA SHUICHI
Published: July 2008

We consider the initial value problem for a nonlinear version of the dissipative Timoshenko system. This syetem verifies the decay property of regularity-loss type. To overcome this difficulty caused by the regularity-loss property, we employ the time weighed L2 energy method which is combined with the optimal L2 decay estimates for lower order derivatives of solutions. Then we show the global existence and asymptotic decay of solutions under smallness and enough regularity conditions on the initial data. Moreover, we show that the solution approaches the linear diffusion wave expressed in terms of the superposition of the heat kernels as time tends to infinity.
ON NON-NEWTONIAN FLUIDS WITH A PROPERTY OF RAPID THICKENING UNDER DIFFERENT STIMULUS
Authors: GWIAZDA PIOTR , ŚWIERCZEWSKA-GWIAZDA AGNIESZKA
Published: July 2008

The paper concerns the model of a flow of non-Newtonian fluid with nonstandard growth conditions of the Cauchy stress tensor. Contrary to standard power-law type rheology, we propose the formulation with the help of the spatially-dependent convex function. This framework includes e.g. rapidly shear thickening and magnetorheological fluids. We provide the existence of weak solutions. The nonstandard growth conditions yield the analytical formulation of the problem in generalized Orlicz spaces. Basing on the energy equality, we exploit the tools of Young measures.
PROPAGATION OF SINGULARITIES IN THE SOLUTIONS TO THE BOLTZMANN EQUATION NEAR EQUILIBRIUM
Authors: DUAN RENJUN , LI MENG-RONG , YANG TONG
Published: July 2008

This paper is about the propagation of the singularities in the solutions to the Cauchy problem of the spatially inhomogeneous Boltzmann equation with angular cutoff assumption. It is motivated by the work of Boudin–Desvillettes on the propagation of singularities in solutions near vacuum. It shows that for the solution near a global Maxwellian, singularities in the initial data propagate like the free transportation. Precisely, the solution is the sum of two parts in which one keeps the singularities of the initial data and the other one is regular with locally bounded derivatives of fractional order in some Sobolev space. In addition, the dependence of the regularity on the cross-section is also given.
HOMOGENIZATION OF HAMILTON–JACOBI EQUATIONS: NUMERICAL METHODS
Authors: ACHDOU YVES , CAMILLI FABIO , CAPUZZO DOLCETTA ITALO
Published: July 2008

We study approximation strategies for the limit problem arising in the homogenization of Hamilton–Jacobi equations. They involve first an approximation of the effective Hamiltonian then a discretization of the Hamilton–Jacobi equation with the approximate effective Hamiltonian. We give a global error estimate which takes into account all the parameters involved in the approximation.
NEW LEVELS AND TRANSITIONS IN 72Ge OBSERVED IN THE 72As(β++EC)72Ge DECAY
Authors: SHEN SHUIFA , LI YAN , GU JIAHUI , XU FURONG , WEN TINGDUN , LIU YIBAO , YANG YAXIN
Published: July 2008

The decay of 72 As has been investigated by means of γ-ray spectroscopy. The 72 As nuclei were produced through the 72 Ge (p, n)72 As reaction. The Compton-suppressed spectrometer and high-purity Ge detectors have been used in singles and in coincidence modes respectively to study γ-rays in the β++ EC decay of 72 As to 72 Ge . 79 γ-rays, among which 3 were observed for the first time, were reported. A decay scheme of 72 As including 1 new level is proposed that accommodates 77 of these transitions. Tentative spin and parity assignments are suggested for a number of levels according to the log ft values and γ-branching ratios.
NEUTRON EMISSION SPECTRA AND LEVEL DENSITY OF HOT ROTATING 132Sn
Authors: AGGARWAL MAMTA
Published: July 2008

The neutron emission spectrum of the highly excited compound nuclear system 132 Sn is investigated at high spin. The doubly magic nucleus 132 Sn undergoes a shape transition at high angular momentum which affects the nuclear level density and neutron emission probability considerably. The interplay of temperature, shape, deformation and rotational degrees of freedom and their influence on neutron emission is emphasized. We predict an enhancement of nucleonic emission at those spins where the nucleus suffers a transition from a spherical to deformed shape.
A STUDY OF 97Mo FROM THE (t, p) REACTION
Authors: RAHMAN M. A. , CHOWDHURY M. S.
Published: July 2008

The 97 Mo nucleus has been studied with the reaction 95 Mo (t, p) 97 Mo using a multichannel magnetic spectrograph. The isotopically enriched thin target 95 Mo was bombarded with the 12 MeV triton beam obtained from the tandem Van de Graaff accelerator at the Atomic Weapon Research Establishment, Aldermaston. Proton spectra are obtained at 12 different angles from 5° to 87.5° at an interval of 7.5° and are detected in nuclear emulsion plates. Forty-eight levels in the energy range from 0.000 to 3.189 MeV have been observed. Absolute differential cross-sections for these levels have been measured. The angular distributions are compared with the theoretical distorted-wave Born approximation calculations to determine L and Jπ values. The nuclear properties of 97 Mo are compared with previous experimental results and model predictions.
THE GENERATION MODEL AND THE ELECTROWEAK CONNECTION
Authors: ROBSON B. A.
Published: July 2008

The "electroweak connection", which forms one of the cornerstones of the Standard Model of particle physics, is formulated within the framework of the Generation Model. It is shown that the electroweak connection can be derived assuming that the weak interactions are effective interactions rather than fundamental interactions, arising from a U(1) × SU(2) local gauge invariance, which is spontaneously broken by a Higgs field.
HIGHER TWIST EFFECTS IN PHOTON–PHOTON COLLISIONS
Authors: AHMADOV A. I. , BOZTOSUN I. , SOYLU A. , DADASHOV E. A.
Published: July 2008

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-pT single pseudoscalar and vector mesons inclusive production cross section in two-photon collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients a2 and a4 have been extracted from the CLEO data, Braun–Filyanov pion wave function, the asymptotic and the Chernyak–Zhitnitsky wave functions are all used in the calculations. For ρ-meson we used the Ball–Braun wave function. The results of the calculations reveal that the high twist cross sections, the ratio R, the dependence transverse momentum pT and the rapidity y of meson in the Φ CLEO (x, Q2) wave function case is very close to the Φ asy (x) asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.
BOUND-STATES OF A SEMI-RELATIVISTIC EQUATION FOR THE ${\cal PT}$-SYMMETRIC GENERALIZED HULTHÉN POTENTIAL BY THE NIKIFOROV–UVAROV METHOD
Authors: IKHDAIR SAMEER M. , SEVER RAMAZAN
Published: July 2008

The one-dimensional semi-relativistic equation has been solved for the [Formula: see text]-symmetric generalized Hulthén potential. The Nikiforov–Uvarov (NU) method which is based on solving the second-order linear differential equations by reduction to a generalized equation of hypergeometric type, is used to obtain exact energy eigenvalues and corresponding eigenfunctions. We have investigated the positive and negative exact bound states of the s-states for different types of complex generalized Hulthén potentials.
ANALYTICAL SOLUTIONS TO BRAJINSKII'S EQUATIONS FOR NUCLEAR FUSION PLASMA BY USING ICF METHOD
Authors: HOSSEINIMOTLAGH S. N.
Published: July 2008

Brajinskii's equations are the fundamental relations governing the behavior of the plasma produced during a fusion reaction, especially ICF plasma. These equations contains six partial differentials coupled together. In this paper we have tried to give analytical solutions to these equations using a one-dimensional method. Laplace transform technique is the main tool to do that with an arbitrary boundary and initial conditions for some special cases.
LOWER BOUNDS FOR THE ENERGY OF A MANY-BODY MODEL
Authors: PACHECO A. F. , SAÑUDO J.
Published: July 2008

The well known and analytically solvable Lipkin–Meshkov–Glick model was devised to test several many-body approximation approaches used in nuclear physics. Here, we use this model to illustrate a method that sets lower bounds for the ground state energy of a quantum Hamiltonian. The idea of the method consists of dividing the Hamiltonian into identical groups of terms that represent subdivisions in the particle population of the system, and then to make an appropriate use of the ground energy of one of these groups. The bounds clearly improve as the size of these groups increases.
AXIOMATIC FOUNDATIONS FOR THE PRINCIPLE OF ENTROPY INCREASE
Authors: ZHANG QI-REN
Published: July 2008

We show that the principle of entropy increase may be exactly founded on a few axioms valid not only for quantum and classical statistics, but also for a wide range of statistical processes.
MEDIUM EFFECT OF NUCLEON–NUCLEON CROSS SECTION ON THE ISOSCALING PARAMETER α
Authors: LIU JIAN YE , HAO HUAN FENG , ZUO WEI , LEE XI GUO
Published: July 2008

The medium effect of in-medium nucleon–nucleon cross section [Formula: see text] on the isoscaling parameter α is investigated for two couples of central nuclear reactions 40 Ca +48 Ca and 60 Ca +48 Ca ; 112 Sn +112 Sn and 124 Sn +124 Sn at beam energy region from 40 to 60 MeV/nucleon with isospin dependent quantum molecular dynamics. It is found that there is the obvious medium effect of [Formula: see text] on the isoscaling parameters α. The mechanism for the medium effect of [Formula: see text] on α is investigated.
POPULATION OF MULTI-QUARK STATES IN EXOTIC MULTIPLETS AND THERMALIZATION IN ULTRA-RELATIVISTIC HEAVY ION COLLISIONS
Authors: SCHERER STEFAN , BLEICHER MARCUS , HAUSSLER STEPHANE , STÖCKER HORST
Published: July 2008

The recent discussion about experimental evidence for pentaquark states has revitalized the interest in exotic hadrons. If such states really exist, it is natural to assume that they will be formed at the late hadronization stage of ultra-relativistic heavy ion collisions, given the success of quark recombination models in the description of hadronization. Here, we apply the qMD model to study the formation of color neutral exotic multi-quark clusters at hadronization. We search for color neutral clusters made up of up to six color charges, respectively. We thus obtain estimates for the numbers and phase space distributions of exotic hadronic states produced by clustering in heavy ion collisions, including the members of the pentaquark multiplets. We obtain particle abundances that are smaller than thermal model predictions. Moreover, the results obtained in recombination from ultra-relativistic heavy ion collisions can be compared to the estimates based on equal population of the corresponding multiplets, and to results from fully thermalized systems. We find that the distribution of exotic hadrons from recombination over large multiplets provides a sensitive signal for thermalization and decorrelation of the initial, non-equilibrium state of the collision.
HYPER-SPHERICAL HARMONICS AND ANHARMONICS IN m-DIMENSIONAL SPACE
Authors: SHOJAEI M. R. , RAJABI A. A. , HASANABADI H.
Published: July 2008

In quantum mechanics the hyper-spherical method is one of the most well-established and successful computational tools. The general theory of harmonic polynomials and hyper-spherical harmonics is of central importance in this paper. The interaction potential V is assumed to depend on the hyper-radius ρ only where ρ is the function of the Jacobi relative coordinate x1, x2,…, xn which are functions of the particles' relative positions.
CONFORMATIONAL STUDY OF CITRATES ADSORBED ON GOLD NANOPARTICLES USING FOURIER TRANSFORM INFRARED SPECTROSCOPY
Authors: WULANDARI PRIASTUTI , LI XINHENG , TAMADA KAORU , HARA MASAHIKO
Published: July 2008

We investigated the structure of citrates adsorbed on Au nanoparticles ( AuNPs ) synthesized by the Frens method by Fourier transformed infrared spectroscopy (FTIR). We found that physisorbed citrates are stable enough to stay on the surface of AuNPs during purification. The FT-IR spectra of citrates on AuNPs are quite uniquely different from bulk citrates, suggesting the formation of coordination bond between carboxylate group and gold. The shifts of carboxylate vibration modes on AuNPs are larger than that on flat Au substrates, as expected from the stronger dipole field on AuNPs compared with that on flat substrates.
COLLISIONAL EFFECT OF THE SOLVENT ON THE OPTICAL RESPONSES OF A TWO-LEVEL SYSTEM
Authors: MASTRODOMENICO A. , GORAYEB M. , PAZ J. L.
Published: July 2008

The optical properties of a two-level molecular system immersed in a thermal reservoir and irradiated by an electromagnetic field were studied using the optical stochastic Bloch equations. The effect of the solvent is modeled as a stochastical shift of the system's Bohr frequency and the electromagnetic field includes both pump and probe fields. The resulting analytical expressions were studied by means of two and three dimensional graphics of the optical properties as a function of the pump-frequency detuning factor and the strength of the noise source.
EFFECT OF MgO DOPING ON COERCIVE FIELD IN LiNbO3 CRYSTALS
Authors: SEN P. , SISODIA N. , CHOUBEY R. K. , KAR S. , BARTWAL K. S.
Published: July 2008

The theoretically calculated values of coercive field in doped and undoped Lithium niobate (LN) crystals show vast disparity with the available experimental data. Based on the double well potential model, we have calculated the effect of MgO doping as well as the effect of Li / Nb ratio on the coercive field in LN crystals. The theoretical results are well in agreement with the experimental observations.
A GRAM SCALE SYNTHESIS OF MONODISPERSED SILVER NANOPARTICLES CAPPED BY CARBOXYLATES AND THEIR LIGAND EXCHANGE
Authors: KEUM CHANG-DAE , ISHII NORIYUKI , MICHIOKA KANAE , WULANDARI PRIASTUTI , TAMADA KAORU , FURUSAWA MASAHIKO , FUKUSHIMA HITOSHI
Published: July 2008

In this paper, we report a simple yet powerful synthetic method for obtaining monodispersed silver nanoparticles by direct thermal decomposition of two materials — one is silver acetate as a source of the metal core and the other is myristic acid as a capping agent. The reaction was performed at 250°C, the boiling point of myristic acid, without additional solvent. The nucleation and growth of the particles were monitored by dynamic light scattering in order to optimize the reaction time. By this simple procedure, we could obtain uniformly sized Ag nanoparticles with the average diameter of 4.8 ± 0.1 nm. Although the particles were synthesized at high temperature, the ligand exchange between myristates and alkanethiolates can be achieved at room temperature. Significant characteristics of Ag nanoparticles attributed to localized surface plasmons were investigated.
NEW CLASS OF BRIGHT SPATIAL SOLITONS OBTAINED BY HIROTA'S METHOD FROM GENERALIZED COUPLED MODE EQUATIONS OF NONLINEAR OPTICAL BRAGG GRATING
Authors: ALATAS H. , KANDI A. A. , ISKANDAR A. A. , TJIA M. O.
Published: July 2008

We have demonstrated by Hirota's bilinear method the existence of a new class of bright spatial soliton solutions from the same model of nonlinear optical Bragg grating considered previously by another group of researchers. The explicit expressions obtained from these soliton profiles are distinctly different from the previous results and offer a much more flexible choice of physical parameters for device design. It was further shown that the present formulation provides a classification scheme incorporating previous results as special cases of different parameter sets. Finally, due to the diffraction effect, these solitons were shown to exhibit a certain degree of instability in their perturbed profiles as they propagate along the grating.
COMPACT AND EFFICIENT Er–Yb-DOPED FIBER AMPLIFIER
Authors: DIMYATI K. , HARUN S. W. , MUHD-YASSIN S. Z. , ABD-RAHMAN M. K. , AHMAD H.
Published: July 2008

A compact and efficient optical amplifier is demonstrated using an erbium–ytterbium-doped fiber amplifier (EYDFA) with a double-pass configuration. It uses only 3 m of doped fiber with 20 mW pump power. This forward-pumped amplifier achieves a maximum low signal gain of 37 dB and a corresponding noise figure of 5.5 dB. Compared with the backward-pumping double-pass EYDFA, the gain obtained is 7 dB higher, with a lower noise figure of 5.5 dB. In addition, the gain obtained in this study is 17 dB higher than that of a conventional forward-pumping single-pass amplifier, while its noise figure is only 0.5 dB higher. These results show that the forward-pumped double-pass design holds great promise in the development of practical and cost-efficient optical amplifiers which can be pumped by using LEDs or low cost laser diodes.
SYNTHESIS OF Mn-DOPED ZnS AND THE DOPANT-INDUCED PHOTOLUMINESCENCE PROPERTY
Authors: THUY NGUYEN MINH , SAM DO THI , THI TRAN MINH , KHOI NGUYEN THE
Published: July 2008

In this paper, we present our study of optical properties of ZnS and ZnS : Mn at 0–12 at. % concentration Mn 2+ prepared by the wet chemical method. All the resulting ZnS samples are of the single phase with sphalerite crystal structure. The average particle size is about 5–10 nm. The photoluminescence intensity of samples is shown to increase with increasing Mn concentration, reaching a maximum at the solid solubility limit of Mn 2+ in ZnS .
Spontaneous Plasticity of Multineuronal Activity Patterns in Activated Hippocampal Networks
Authors: Usami Atsushi , Matsuki Norio , Ikegaya Yuji
Published: July 2008

Using functional multineuron imaging with single-cell resolution, we examined how hippocampal networks by themselves change the spatiotemporal patterns of spontaneous activity during the course of emitting spontaneous activity. When extracellular ionic concentrations were changed to those that mimicked in vivo conditions, spontaneous activity was increased in active cell number and activity frequency. When ionic compositions were restored to the control conditions, the activity level returned to baseline, but the weighted spatial dispersion of active cells, as assessed by entropy-based metrics, did not. Thus, the networks can modify themselves by altering the internal structure of their correlated activity, even though they as a whole maintained the same level of activity in space and time.