bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallel and Serial Neural Mechanisms for Visual Search in Macaque Area V4
Authors: Bichot Narcisse P. , Rossi Andrew F. , Desimone Robert
Published: April 2005

To find a target object in a crowded scene, a face in a crowd for example, the visual system might turn the neural representation of each object on and off in a serial fashion, testing each representation against a template of the target item. Alternatively, it might allow the processing of all objects in parallel but bias activity in favor of those neurons that represent critical features of the target, until the target emerges from the background. To test these possibilities, we recorded neurons in area V4 of monkeys freely scanning a complex array to find a target defined by color, shape, or both. Throughout the period of searching, neurons gave enhanced responses and synchronized their activity in the gamma range whenever a preferred stimulus in their receptive field matched a feature of the target, as predicted by parallel models. Neurons also gave enhanced responses to candidate targets that were selected for saccades, or foveation, reflecting a serial component of visual search. Thus, serial and parallel mechanisms of response enhancement and neural synchrony work together to identify objects in a scene. To find a target object in a crowded scene, a face in a crowd for example, the visual system might turn the neural representation of each object on and off in a serial fashion, testing each representation against a template of the target item. Alternatively, it might allow the processing of all objects in parallel but bias activity in favor of those neurons that represent critical features of the target, until the target emerges from the background. To test these possibilities, we recorded neurons in area V4 of monkeys freely scanning a complex array to find a target defined by color, shape, or both. Throughout the period of searching, neurons gave enhanced responses and synchronized their activity in the gamma range whenever a preferred stimulus in their receptive field matched a feature of the target, as predicted by parallel models. Neurons also gave enhanced responses to candidate targets that were selected for saccades, or foveation, reflecting a serial component of visual search. Thus, serial and parallel mechanisms of response enhancement and neural synchrony work together to identify objects in a scene.
Learning from the Past to Forge a Future
Authors: Muller Peter
Published: April 2005

Up Against the Sprawl
Public Policy and the Making of Southern California.
Jennifer Wolch, Manuel Pastor Jr., and Peter Dreier, Eds.
. University of Minnesota Press, Minneapolis, 2004. 423 pp. $74.95. ISBN 0-8166-4297-4. Paper, $24.95. ISBN 0-8166-4298-2.

Examining the sprawling evolution of Los Angeles, the contributors argue that government agencies and public policies--on the local, state, and federal levels--dictated many aspects of the region's growth and can help shape future changes in the metropolis.
Survival and Replication of Clinical
Mycobacterium tuberculosis
Isolates in the Context of Human Innate Immunity
Authors: Janulionis Ernestas , Sofer Carolina , Schwander Stephan K. , Nevels Denarra , Kreiswirth Barry , Shashkina Elena , Wallis Robert S.
Published: April 2005

The initial host response to
Mycobacterium tuberculosis
is driven by innate immunity. For this study, we examined the ability of 18 recent clinical isolates and 5 reference strains to survive and replicate in the context of host innate immunity by using whole blood culture. Six healthy tuberculin-negative volunteers served as subjects. H
37
Ra showed the least capacity to replicate of any of the strains tested, decreasing in viability 1.3 log CFU during 72 h of whole blood culture, whereas H
37
Rv increased 0.32 log. Clinical isolates varied greatly in their ability to replicate in blood cells, ranging from −0.4 to +0.8 log (
P
< 0.001). Four showed significantly more growth than H
37
Rv, and one showed significantly reduced growth. Host mechanisms for restricting intracellular mycobacterial growth were more effective during the first 24 h of whole blood culture than during the 24- to 72-h period. Certain mycobacterial isolates appeared preferentially able to withstand host defenses during each of these intervals. Although there was relatively more homogeneity among subjects than among strains, one of the six subjects showed a reduced capacity to restrict intracellular mycobacterial growth due to a defect expressed during the first 24 h of culture. Our findings indicate substantial variability in the capacity of clinical tuberculosis isolates to replicate in host cells in the face of innate host immunity.
Molecular Cloning and Characterization of Three β-Defensins from Canine Testes
Authors: Sang Yongming , Ortega M. Teresa , Blecha Frank , Prakash Om , Melgarejo Tonatiuh
Published: April 2005

Mammalian β-defensins are small cationic peptides possessing broad antimicrobial and physiological activities. Because dogs are particularly resilient to sexually transmitted diseases, it has been proposed that their antimicrobial peptide repertoire might provide insight into novel antimicrobial therapeutics and treatment regimens. To investigate this proposal, we cloned the full-length cDNA of three canine β-defensin isoforms (cBD-1,-2, and-3) from canine testicular tissues. Their predicted peptides share identical N-terminal 65-amino-acid residues, including the β-defensin consensus six-cysteine motif. The two longer isoforms,cBD-2and-3, possess 4 and 34 additional amino acids, respectively, at the C terminus. To evaluate the antimicrobial activity of cBD, a 34-amino-acid peptide derived from the shared mature peptide region was synthesized. Canine β-defensin displayed broad antimicrobial activity against gram-positive bacteria (Listeria monocytogenesandStaphylococcus aureus; MICs of 6 and 100 μg/ml, respectively), gram-negative bacteria (Escherichia coli,Klebsiella pneumoniae, andNeisseria gonorrhoeae; MICs of 20 to 50, 20, and 50 μg/ml, respectively), and yeast (Candida albicans; MIC of 5 to 50 μg/ml) and lower activity againstUreaplasma urealyticumandU. canigenitalium(MIC of 200 μg/ml). Antimicrobial potency was significantly reduced at salt concentrations higher than 140 mM. All three canine β-defensins were highly expressed in testis. In situ hybridization indicated thatcBD-1was expressed primarily in Sertoli cells within the seminiferous tubules. In contrast,cBD-2was located primarily within Leydig cells. The longest isoform,cBD-3, was detected in Sertoli cells and to a lesser extent in the interstitium. The tissue-specific expression and broad antimicrobial activity suggest that canine β-defensins play an important role in host defense and other physiological functions of the male reproductive system.
Intranasal Vaccination Induces Protective Immunity against Intranasal Infection with VirulentFrancisella tularensisBiovar A
Authors: Wu Terry H. , Hutt Julie A. , Garrison Kristin A. , Berliba Lyudmila S. , Zhou Yan , Lyons C. Rick
Published: April 2005

The inhalation ofFrancisella tularensisbiovar A causes pneumonic tularemia associated with high morbidity and mortality rates in humans. Exposure toF. tularensisusually occurs by accident, but there is increasing awareness thatF. tularensismay be deliberately released in an act of bioterrorism or war. The development of a vaccine against pneumonic tularemia has been limited by a lack of information regarding the mechanisms required to protect against this disease. Vaccine models forF. tularensisin inbred mice would facilitate investigations of the protective mechanisms and significantly enhance vaccine development. Intranasal vaccination with the attenuated live vaccine strain (LVS) ofF. tularensisreproducibly protected BALB/c mice, but not C57BL/6 mice, against intranasal and subcutaneous challenges with a virulent clinical isolate ofF. tularensisbiovar A (NMFTA1). The resistance of LVS-vaccinated BALB/c mice to intranasal NMFTA1 challenge was increased 100-fold by boosting with live NMFTA1 but not with LVS. The protective response was specific forF. tularensisand required both CD4 and CD8 T cells. The vaccinated mice appeared outwardly healthy for more than 2 months after NMFTA1 challenge, even though NMFTA1 was recovered from more than half of the vaccinated mice. These results show that intranasal vaccination induces immunity that protects BALB/c mice from intranasal infection byF. tularensisbiovar A.
Use of In Vivo-Induced Antigen Technology for Identification of
Escherichia coli
O157:H7 Proteins Expressed during Human Infection
Authors: John Manohar , Kudva Indira T. , Griffin Robert W. , Dodson Allen W. , McManus Bethany , Krastins Bryan , Sarracino David , Progulske-Fox Ann , Hillman Jeffrey D. , Handfield Martin , Tarr Phillip I. , Calderwood Stephen B.
Published: April 2005

Using in vivo-induced antigen technology (IVIAT), a modified immunoscreening technique that circumvents the need for animal models, we directly identified immunogenic
Escherichia coli
O157:H7 (O157) proteins expressed either specifically during human infection but not during growth under standard laboratory conditions or at significantly higher levels in vivo than in vitro. IVIAT identified 223 O157 proteins expressed during human infection, several of which were unique to this study. These in vivo-induced (ivi) proteins, encoded by ivi genes, mapped to the backbone, O islands (OIs), and pO157. Lack of in vitro expression of O157-specific ivi proteins was confirmed by proteomic analysis of a mid-exponential-phase culture of
E. coli
O157 grown in LB broth. Because ivi proteins are expressed in response to specific cues during infection and might help pathogens adapt to and counter hostile in vivo environments, those identified in this study are potential targets for drug and vaccine development. Also, such proteins may be exploited as markers of O157 infection in stool specimens.
PavA ofStreptococcus pneumoniaeModulates Adherence, Invasion, and Meningeal Inflammation
Authors: Pracht Daniela , Elm Christine , Gerber Joachim , Bergmann Simone , Rohde Manfred , Seiler Marleen , Kim Kwang S. , Jenkinson Howard F. , Nau Roland , Hammerschmidt Sven
Published: April 2005

Pneumococcal adherence and virulence factor A (PavA) is displayed to the cell outer surface ofStreptococcus pneumoniaeand mediates pneumococcal binding to immobilized fibronectin. PavA, which lacks a typical gram-positive signal sequence and cell surface anchorage motif, is essential for pneumococcal virulence in a mouse infection model of septicemia. In this report the impact of PavA on pneumococcal adhesion to and invasion of eukaryotic cells and on experimental pneumococcal meningitis was investigated. In the experimental mouse meningitis model, the virulence of thepavAknockout mutant ofS. pneumoniaeD39, which did not show alterations of subcellular structures as indicated by electron microscopic studies, was strongly decreased. Pneumococcal strains deficient in PavA showed substantially reduced adherence to and internalization of epithelial cell lines A549 and HEp-2. Similar results were obtained with human brain-derived microvascular endothelial cells and human umbilical vein-derived endothelial cells. Attachment and internalization of pneumococci were not significantly affected by preincubation or cocultivations of pneumococci with anti-PavA antisera. Pneumococcal adherence was also not significantly affected by the addition of PavA protein. Complementation of thepavAknockout strain with exogenously added PavA polypeptide did not restore adherence of the mutant. These data suggest that PavA affects pneumococcal colonization by modulating expression or function of important virulence determinants ofS. pneumoniae.
Pneumocystis cariniiActivates the NF-κB Signaling Pathway in Alveolar Epithelial Cells
Authors: Wang Jing , Gigliotti Francis , Maggirwar Sanjay , Johnston Carl , Finkelstein Jacob N. , Wright Terry W.
Published: April 2005

Pneumocystis cariniipneumonia (PcP) is a clinically important infection of immunocompromised patients. Although the interaction ofPneumocystiswith the alveolar epithelium has been well documented, very little information regarding the epithelial response toPneumocystisis currently available. In order to studyPneumocystis-epithelium interactions, a murine cell line derived specifically from an alveolar epithelial cell (AEC) was utilized. The coculture of murine AECs with mousePneumocystisinduced a dose- and time-dependent release of the CXC chemokine MIP-2. Importantly, the specific removal ofPneumocystisfrom the preparation, or the pretreatment of AECs with sulfasalazine, a potent and specific inhibitor of NF-κB, nearly completely abrogated the chemokine response toPneumocystis. Since the murine MIP-2 promoter contains consensus κB binding sequences, the ability ofPneumocystisto stimulate NF-κB signaling in AECs was examined.Pneumocystisstimulation of an AEC line stably transfected with a κB-dependent reporter construct triggered the NF-κB signaling pathway and reporter production. These data were confirmed in gel shift assays, providing direct evidence thatPneumocystisinduced the nuclear translocation of the p50/p65 heterodimeric form of NF-κB. Maximal NF-κB activation was dependent upon direct contact with viablePneumocystisorganisms. These data demonstrate thatPneumocystisactivates NF-κB signaling in AECs and establish a reporter cell line for studying NF-κB activation in AECs. Given the global regulatory functions of the NF-κB family, these findings suggest thatPneumocystisdirectly alters AEC gene expression in a manner that promotes pulmonary immune and inflammatory responses.
Cross-Reactive Surface Epitopes on Chondroitin Sulfate A-AdherentPlasmodium falciparum-Infected Erythrocytes Are Associated with Transcription ofvar2csa
Authors: Elliott Salenna R. , Duffy Michael F. , Byrne Timothy J. , Beeson James G. , Mann Emily J. , Wilson Danny W. , Rogerson Stephen J. , Brown Graham V.
Published: April 2005

Malaria in pregnancy is associated with placental accumulation ofPlasmodium falciparum-infected erythrocytes (IE) that adhere to chondroitin sulfate A (CSA). Adhesion is mediated byP. falciparumerythrocyte membrane protein 1 (PfEMP1), a variant parasite protein expressed on the surface of IE and encoded byvargenes. Rabbit antiserum was generated against the CSA-adherentP. falciparumline CS2, in which the dominantvartranscribed isvar2csa, a relatively conservedvargene that has been associated with CSA adhesion. Anti-CS2 recognized genetically distinct CSA-adherentP. falciparumlines but not CD36-adherent parent lines. Reactivity with anti-CS2 correlated with the level of adhesion to CSA. Fluorescence-activated cell sorting according to binding of anti-CS2 showed reactivity was associated with CSA adhesion and transcription ofvar2csa. These data are consistent with the hypothesis thatvar2csaencodes a PfEMP1 expressed on the surface of IE, which mediates adhesion to CSA and is relatively conserved between genetically distinct strains ofP. falciparum.
Effects of Oligopeptide Permease in Group A Streptococcal Infection
Authors: Wang Chih-Hung , Lin Chia-Yu , Luo Yueh-Hsia , Tsai Pei-Jane , Lin Yee-Shin , Lin Ming T. , Chuang Woei-Jer , Liu Ching-Chuan , Wu Jiunn-Jong
Published: April 2005

The oligopeptide permease (Opp) of group A streptococci (GAS) is a membrane-associated protein and belongs to the ATP-binding cassette transporter family. It is encoded by a polycistronic operon containingoppA,oppB,oppC,oppD, andoppF. The biological function of these genes in GAS is poorly understood. In order to understand more about the effects of Opp on GAS virulence factors, anoppAisogenic mutant was constructed by using an integrative plasmid to disrupt theoppoperon and confirmed by Southern blot hybridization. No transcript was detected in theoppAisogenic mutant by Northern blot analysis and reverse transcriptase PCR. The growth curve for theoppAisogenic mutant was similar to that for wild-type strain A-20. TheoppAisogenic mutant not only decreased the transcription ofspeB,speX, androfAbut also increased the transcription ofspeF,sagA(streptolysin S-associated gene A),slo(streptolysin O),pel(pleotrophic effect locus), anddppA(dipeptide permease). No effects on the transcription ofemm,sda,speJ,speG,rgg, andcsrRwere found. The phenotypes of theoppAmutant were restored by theoppArevertant and by the complementation strain. TheoppAmutant caused less mortality and tissue damage than the wild-type strain when inoculated into BALB/c mice via an air pouch. Based on these data, we suggest that theoppoperon plays an important role in the pathogenesis of GAS infection.
Characterization of the Major Secreted Zinc Metalloprotease- Dependent Glycerophospholipid:Cholesterol Acyltransferase, PlaC, of
Legionella pneumophila
Authors: Banerji Sangeeta , Bewersdorff Mayte , Hermes Björn , Cianciotto Nicholas P. , Flieger Antje
Published: April 2005

Legionella pneumophila
, an intracellular pathogen causing a severe pneumonia, possesses distinct lipolytic activities which have not been completely assigned to specific enzymes so far. We cloned and characterized a gene,
plaC
, encoding a protein with high homology to PlaA, the major secreted lysophospholipase A of
L. pneumophila
and to other hydrolytic enzymes belonging to the GDSL family. Here we show that
L. pneumophila plaC
mutants possessed reduced phospholipase A and lysophospholipase A activities and lacked glycerophospholipid:cholesterol acyltransferase activity in their culture supernatants. The mutants' reduced phospholipase A and acyltransferase activities were complemented by reintroduction of an intact copy of
plaC
. Additionally,
plaC
conferred increased lysophospholipase A and glycerophospholipid:cholesterol acytransferase activities to recombinant
Escherichia coli
. Furthermore, PlaC was shown to be another candidate exported by the
L. pneumophila
type II secretion system and was activated by a factor present in the bacterial culture supernatant dependent on the zinc metalloprotease. Finally, the role of
plaC
in intracellular infection of
Acanthamoeba castellanii
and U937 macrophages with
L. pneumophila
was assessed, and
plaC
was found to be dispensable. Thus,
L. pneumophila
possesses another secreted lipolytic enzyme, a protein with acyltransferase, phospholipase A, and lysophospholipase A activities. This enzyme is distinguished from the previously characterized phospholipases A and lysophospholipases A by its capacity not only to cleave fatty acids from lipids but to transfer them to cholesterol. Cholesterol is an important compound of eukaryotic membranes, and an acyltransferase might be a tool for host cell modification to fit the needs of the bacterium.
Escherichia coli
K1 RS218 Interacts with Human Brain Microvascular Endothelial Cells via Type 1 Fimbria Bacteria in the Fimbriated State
Authors: Teng Ching-Hao , Cai Mian , Shin Sooan , Xie Yi , Kim Kee-Jun , Khan Naveed Ahmed , Di Cello Francescopaolo , Kim Kwang Sik
Published: April 2005

Escherichia coli
K1 is a major gram-negative organism causing neonatal meningitis.
E. coli
K1 binding to and invasion of human brain microvascular endothelial cells (HBMEC) are a prerequisite for
E. coli
penetration into the central nervous system in vivo. In the present study, we showed using DNA microarray analysis that
E. coli
K1 associated with HBMEC expressed significantly higher levels of the
fim
genes compared to nonassociated bacteria. We also showed that
E. coli
K1 binding to and invasion of HBMEC were significantly decreased with its
fimH
deletion mutant and type 1 fimbria locked-off mutant, while they were significantly increased with its type 1 fimbria locked-on mutant.
E. coli
K1 strains associated with HBMEC were predominantly type 1 fimbria phase-on (i.e., fimbriated) bacteria. Taken together, we showed for the first time that type 1 fimbriae play an important role in
E. coli
K1 binding to and invasion of HBMEC and that type 1 fimbria phase-on
E. coli
is the major population interacting with HBMEC.
Extracellular Carbohydrate-Containing Polymers of a Model Biofilm-Producing Strain,
Staphylococcus epidermidis
RP62A
Authors: Sadovskaya Irina , Vinogradov Evgueny , Flahaut Sigrid , Kogan Grigorij , Jabbouri Saïd
Published: April 2005

Staphylococcus aureus
and coagulase-negative staphylococci, primarily
Staphylococcus epidermidis
, are recognized as a major cause of nosocomial infections associated with the use of implanted medical devices. It has been established that clinical isolates often produce a biofilm, which is involved in adherence to biomaterials and provides enhanced resistance of bacteria against host defenses and antibiotic treatments. It has been thought that the staphylococcal biofilm contains two polysaccharides, one responsible for primary cell adherence to biomaterials (polysaccharide/adhesin [PS/A]) and an antigen that mediates bacterial aggregation (polysaccharide intercellular adhesin [PIA]). In the present paper we present an improved procedure for preparation of PIA that conserves its labile substituents and avoids contamination with by-products. Based on structural analysis of the polysaccharide antigens and a thorough overview of the previously published data, we concluded that PIA from
S. epidermidis
is structurally identical to the recently described poly-β-(1→6)-
N
-acetylglucosamine from PS/A-overproducing strain
S. aureus
MN8m. We also show that another carbohydrate-containing polymer, extracellular teichoic acid (EC TA), is an essential component of
S. epidermidis
RP62A biofilms. We demonstrate that the relative amounts of extracellular PIA and EC TA produced depend on the growth conditions. Moderate shaking or static culture in tryptic soy broth favors PIA production, while more EC TA is produced in brain heart infusion medium.
The Vaccine Candidate
Vibrio cholerae
638 Is Protective against Cholera in Healthy Volunteers
Authors: García Luis , Jidy Manuel Díaz , García Hilda , Rodríguez Boris L. , Fernández Roberto , Año Gemma , Cedré Bárbara , Valmaseda Tania , Suzarte Edith , Ramírez Margarita , Pino Yadira , Campos Javier , Menéndez Jorge , Valera Rodrigo , González Daniel , González Irma , Pérez Oliver , Serrano Teresita , Lastre Miriam , Miralles Fernando , del Campo Judith , Maestre Jorge Luis , Pérez José Luis , Talavera Arturo , Pérez Antonio , Marrero Karen , Ledón Talena , Fando Rafael
Published: April 2005

Vibrio cholerae
638 is a living candidate cholera vaccine strain attenuated by deletion of the CTXΦ prophage from C7258 (O1, El Tor Ogawa) and by insertion of the
Clostridium thermocellum
endoglucanase A gene into the hemagglutinin/protease coding sequence. This vaccine candidate was previously found to be well tolerated and immunogenic in volunteers. This article reports a randomized, double-blind, placebo-controlled trial conducted to test short-term protection conferred by 638 against subsequent
V. cholerae
infection and disease in volunteers in Cuba. A total of 45 subjects were enrolled and assigned to receive vaccine or placebo. The vaccine contained 10
9
CFU of freshly harvested 638 buffered with 1.3% NaHCO
3
, while the placebo was buffer alone. After vaccine but not after placebo intake, 96% of volunteers had at least a fourfold increase in vibriocidal antibody titers, and 50% showed a doubling of at least the lipopolysaccharide-specific immunoglobulin A titers in serum. At 1 month after vaccination, five volunteers from the vaccine group and five from the placebo group underwent an exploratory challenge study with 10
9
CFU of ΔCTXΦ attenuated mutant strain
V. cholerae
81. Only two volunteers from the vaccine group shed strain 81 in their feces, but none of them experienced diarrhea; in the placebo group, all volunteers excreted the challenge strain, and three had reactogenic diarrhea. An additional 12 vaccinees and 9 placebo recipients underwent challenge with 7 × 10
5
CFU of virulent strain
V. cholerae
3008 freshly harvested from a brain heart infusion agar plate and buffered with 1.3% NaHCO
3
. Three volunteers (25%) from the vaccine group and all from the placebo group shed the challenge agent in their feces. None of the 12 vaccinees but 7 volunteers from the placebo group had diarrhea, and 2 of the latter exhibited severe cholera (>5,000 g of diarrheal stool). These results indicate that at 1 month after ingestion of a single oral dose (10
9
CFU) of strain 638, volunteers remained protected against cholera infection and disease provoked by the wild-type challenge agent
V. cholerae
3008. We recommend that additional vaccine lots of 638 be prepared under good manufacturing practices for further evaluation.
Cytolethal Distending Toxin (CDT)-Negative
Campylobacter jejuni
Strains and Anti-CDT Neutralizing Antibodies Are Induced during Human Infection but Not during Colonization in Chickens
Authors: AbuOun Manal , Manning Georgina , Cawthraw Shaun A. , Ridley Anne , Ahmed If H. , Wassenaar Trudy M. , Newell Diane G.
Published: April 2005

The cytolethal distending toxin (CDT) of
Campylobacter jejuni
was detectable, using an in vitro assay, in most but not all of 24 strains tested. The reason for the absence of toxin activity in these naturally occurring CDT-negative
C. jejuni
strains was then investigated at the genetic level. CDT is encoded by three highly conserved genes,
cdtA
,
-B
, and -
C
. In the CDT-negative strains, two types of mutation were identified. The CDT activities of
C. jejuni
strains possessing both types of mutation were successfully complemented with the functional genes of
C. jejuni
11168. The first type of mutation comprised a 667-bp deletion across
cdtA
and
cdtB
and considerable degeneration in the remainder of the
cdt
locus. Using a PCR technique to screen for this deletion, this mutation occurred in fewer than 3% of 147 human, veterinary, and environmental strains tested. The second type of mutation involved at least four nonsynonymous nucleotide changes, but only the replacement of proline with serine at CdtB position 95 was considered important for CDT activity. This was confirmed by site-directed mutagenesis. This type of mutation also occurred in fewer than 3% of strains as determined using a LightCycler biprobe assay. The detection of two CDT-negative clinical isolates raised questions about the role of CDT in some cases of human campylobacteriosis. To determine if anti-CDT antibodies are produced in human infection, a toxin neutralization assay was developed and validated using rabbit antisera. Pooled human sera from infected patients neutralized the toxin, indicating expression and immunogenicity during infection. However, no neutralizing antibodies were detected in colonized chickens despite the expression of CDT in the avian gut as indicated by reverse transcription-PCR.
Small-Molecule Inhibitors Specifically Targeting Type III Secretion
Authors: Nordfelth R. , Kauppi A. M. , Norberg H. A. , Wolf-Watz H. , Elofsson M.
Published: April 2005

The type III secretion (TTS) system is used by several animal and plant pathogens to deliver effector proteins into the cytosol of the eukaryotic target cell as a strategy to evade the defense reactions elicited by the infected organism. The fact that these systems are highly homologous implies that novel antibacterial agents that chemically attenuate the pathogens via a specific interaction with the type III secretion mechanism can be identified. A number of small organic molecules having this potential have recently been identified (A. M. Kauppi, R. Nordfelth, H. Uvell, H. Wolf-Watz, and M. Elofsson, Chem. Biol. 10:241-249, 2003). Using different reporter gene constructs, we showed that compounds that belong to a class of acylated hydrazones of different salicylaldehydes target the TTS system of
Yersinia pseudotuberculosis
. One of these compounds, compound 1, was studied in detail and was found to specifically block Yop effector secretion under in vitro conditions by targeting the TTS system. In this respect the drug mimics the well-known effect of calcium on Yop secretion. In addition, compound 1 inhibits Yop effector translocation after infection of HeLa cells without affecting the eukaryotic cells or the bacteria. A HeLa cell model that mimics in vivo conditions showed that compound 1 chemically attenuates the pathogen to the advantage of the eukaryotic cell. Thus, our results show proof of concept, i.e., that small compounds targeting the TTS system can be identified, and they point to the possible use of TTS inhibitors as a novel class of antibacterial agents.
CD40 Signaling in Macrophages Induces Activity against an Intracellular Pathogen Independently of Gamma Interferon and Reactive Nitrogen Intermediates
Authors: Andrade Rosa M. , Portillo Jose-Andres C. , Wessendarp Matthew , Subauste Carlos S.
Published: April 2005

Gamma interferon (IFN-γ) is the major inducer of classical activation of macrophages. Classically activated mouse macrophages acquire antimicrobial activity that is largely dependent on the production of reactive nitrogen intermediates. However, protection against important intracellular pathogens can take place in the absence of IFN-γ and nitric oxide synthase 2 (NOS2). UsingToxoplasma gondiias a model, we investigated if CD40 signaling generates mouse macrophages with effector function against an intracellular pathogen despite the absence of priming with IFN-γ and lack of production of reactive nitrogen intermediates. CD40-stimulated macrophages acquired anti-T. gondiiactivity that was not inhibited by a neutralizing anti-IFN-γ monoclonal antibody but was ablated by the neutralization of tumor necrosis factor alpha (TNF-α). Moreover, while the induction of anti-T. gondiiactivity in response to CD40 stimulation was unimpaired in macrophages from IFN-γ−/−mice, macrophages from TNF receptor 1/2−/−mice failed to respond to CD40 engagement. In contrast to IFN-γ-lipopolysaccharide, CD40 stimulation did not induce NOS2 expression and did not trigger production of reactive nitrogen intermediates. NeitherNG-monomethyl-l-arginine nor diphenyleneiodonium chloride affected the induction of anti-T. gondiiactivity in response to CD40. Finally, macrophages from NOS2−/−mice acquired anti-T. gondiiactivity in response to CD40 stimulation that was similar to that of macrophages from wild-type mice. These results demonstrate that CD40 induces the antimicrobial activity of macrophages against an intracellular pathogen despite the lack of two central features of classically activated macrophages: priming with IFN-γ and production of reactive nitrogen intermediates.
TheBartonella vinsoniisubsp.arupensisImmunodominant Surface Antigen BrpA Gene, Encoding a 382-Kilodalton Protein Composed of Repetitive Sequences, Is a Member of a Multigene Family Conserved amongBartonellaSpecies
Authors: Gilmore Robert D. , Bellville Travis M. , Sviat Steven L. , Frace Michael
Published: April 2005

Bartonellaproteins that elicit an antibody response during an infection are poorly defined; therefore, to characterize antigens recognized by the host, aBartonellagenomic expression library was screened with serum from an infected mouse. This process led to the discovery of aBartonella vinsoniisubsp.arupensisgene encoding a 382-kDa protein, part of a gene family encoding large proteins, each containing multiple regions of repetitive segments. The genes were termedbrpAto-C(bartonellarepeatprotein) and bore significant similarity to genes encoding the BadA adhesin protein and members of the variably expressed outer membrane protein family of proteins fromBartonella henselaeandBartonella quintana, respectively.
A Hypothetical Protein of
Streptococcus mutans
Is Critical for Biofilm Formation
Authors: Brown Thomas A. , Ahn Sang-Joon , Frank Roslyn N. , Chen Yi-Ywan M. , Lemos José A. , Burne Robert A.
Published: April 2005

Inactivation of the Smu0630 gene of
Streptococcus mutans
resulted in dramatic decreases in biofilm formation, regardless of the carbohydrate source. The Smu0630 protein contained numerous interesting features, including a possible signal sequence and two conserved regions of repeated sequences. Smu0630 may represent a potential target for novel therapeutics.
Requirement of MgtC for
Brucella suis
Intramacrophage Growth: a Potential Mechanism Shared by
Salmonella enterica
and
Mycobacterium tuberculosis
for Adaptation to a Low-Mg
2+
Environment
Authors: Lavigne Jean-Philippe , O'Callaghan David , Blanc-Potard Anne-Béatrice
Published: April 2005

A
Brucella suis mgtC
mutant is defective for growth within macrophages and in low-Mg
2+
medium. These phenotypes are strikingly similar to those observed with
mgtC
mutants from
Salmonella enterica
and
Mycobacterium tuberculosis
, two other pathogens that proliferate within phagosomes. MgtC appears as a remarkable virulence factor that would have been acquired by distantly related intracellular pathogens to contribute to the adaptation to a low-Mg
2+
environment in the phagosome.
Interleukin-15 Enhances Innate and Adaptive Immune Responses to Blood-Stage Malaria Infection in Mice
Authors: Ing Rebecca , Gros Philippe , Stevenson Mary M.
Published: April 2005

Compared to C57BL/6 wild-type mice, interleukin-15−/−(IL-15−/−) mice showed delayed clearance ofPlasmodium chabaudiAS infection, lower type 1 cytokine production, impaired dendritic cell and NK cell functions, and lower titers of malaria-specific antibodies. Thus, IL-15 supports early control and timely resolution of blood-stage malaria through promotion of Th1-dependent innate and adaptive immune responses.
Conversion of
Staphylococcus epidermidis
Strains from Commensal to Invasive by Expression of the
ica
Locus Encoding Production of Biofilm Exopolysaccharide
Authors: Li Hualin , Xu Lin , Wang Jianping , Wen Yumei , Vuong Cuong , Otto Michael , Gao Qian
Published: April 2005

To test if biofilm formation in
Staphylococcus epidermidis
is dependent on the polysaccharide intercellular adhesin, whose biosynthesis is driven by the
ica
locus, a plasmid containing the
ica
locus was transferred to three
ica
-negative strains. Using in vitro biofilm assays and a rat central venous catheter infection model, we confirmed the importance of the
ica
locus for biofilm production and pathogenesis of
S. epidermidis
.
Reappraisal of the Cambrian glauconite-bearing Anse Maranda Formation, Quebec Appalachians: from deep-sea turbidites to clastic shelf deposits
Authors: Longuépée Hugues , Cousineau Pierre A
Published: April 2005

The Cambrian Anse Maranda Formation is a glauconite-bearing clastic succession within the Quebec Reentrant. It is part of the Appalachians Humber Zone, particularly of the shale  feldspathic sandstone assemblage, which represents the rift-to-drift deposits of the Laurentian margin. The massive sandstones of the Anse Maranda were originally interpreted as the proximal turbidites of a deep-sea fan. The occurrence of glauconite and the high degree of bioturbation, which give the sandstones a massive aspect, suggest a different depositional environment. Detailed ichnology and lithofacies descriptions indicate that the Anse Maranda predominantly represents shelf sediments deposited in storm-influenced environment and that intense bioturbation destroyed most of the sedimentary structures. The paleo geographic reconstruction suggests that the Anse Maranda was deposited seaward of a headland identified as the Montmorency Promontory, along a narrow shelf with an irregular topography. Some coeval turbidites of similar composition were deposited in the deeper sub-basins. This reconstruction allows for sustained sediment-starved conditions to be maintained for more than 10 Ma and to produce anomalously thick glauconite-bearing succession. The bioturbation has influenced the diagenetic evolution of the Anse Maranda Formation. The laminated sandstones and burrows were cemented by early calcite, while the microporosity of the bioturbated sandstones lasted longer and permitted the formation of a muddy pseudomatrix.
UPb zircon geochronology and Nd isotope geochemistry of Proterozoic granitoids in the western Churchill Province: intrusive age pattern and Archean source domains
Authors: Breemen O van , Peterson T D , Sandeman H A
Published: April 2005

Hudsonian tectonism in the western Churchill Province of Canada encompassed two periods of granitic plutonism. The Hudson suite plutons represent xenocryst-rich, mainly monzogranitic, near-minimum melts emplaced near their source region in thickened middle crust; the Nueltin syenogranites and Pitz rhyolites were generated by intrusion of basalt into extending crust. Zircons from four Nueltin suite samples and 20 Hudson suite samples were analysed by UPb SHRIMP techniques. Intrusion of the Hudson suite lasted ca. 50 million years, from 1845 to 1795 Ma, with a peak around 1825 Ma, and the Nueltin suite from 1765 to 1750 Ma, following a ca. 30-million-year period of magmatic quiescence. A marked contrast in Th/U ratios was found in igneous zircon from Hudson suite samples south (Th/U = 0.066) and north (Th/U = 1.07) of the northern margin of the Central Hearne domain and is attributed to a difference in the nature of the melting process, with the lower values representing ultrametamorphism and the higher values representing bulk melting resulting from contact with mafic igneous magma. Whole-rock Nd isotopic measurements, with average ε143Nd near 10, indicate a dominant late Archean crustal component in both suites of granites, reflected by numerous inherited zircon ages between 2720 and 2650 Ma in Hudson granites. Further south, along the Manitoba border, inherited zircons of 35003000 Ma, together with previously published UPb data on gneisses and ca. 3 Ga TDM model ages of Hudson granites, indicate the presence of middle to early Archean crust.
A new description of the skull ofDyrosaurus phosphaticus(Thomas, 1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene of North Africa
Authors: Jouve Stéphane
Published: April 2005

Dyrosaurus phosphaticus (Thomas 1893) has been described several times, but the poor preservation and the incomplete preparation of the material left this species inadequately described. Further preparation of a specimen referred to this species now allows a complete description of the braincase and its various cranial nerves. Dyrosaurid taxonomy is mainly based on mandibular characters and the complete description of the skull of D. phosphaticus, and comparison with the other known species of the family enables enhancement of other taxonomic characters. An emended diagnosis is given for D. phosphaticus, the only known species of this genus. With this new description, new characteristics that enable comparisons with other crocodyliforms are available. The presence of a distinct anterolateral postorbital process is observed in dyrosaurs, Elosuchus, Terminonaris robusta, some Goniopholis, and, although smaller, in Sarcosuchus imperator. In the dyrosaurids D. phosphaticus and Rhabdognathus, the postorbital participates largely in the dorsal margin of the infratemporal fenestra, as in Elosuchus, S. imperator, and Thalattosuchia. The laterodorsal position of the lateral eustachian foramen in dyrosaurids is similar to those of Elosuchus and thalattosuchians. These characters are not shared by Stolokrosuchus lapparenti (included in the family Elosuchidae with Elosuchus), suggesting that without clear phylogenetic analysis, the creation of the Elosuchidae was premature. A preliminary phylogenetic analysis based on comparisons of D. phosphaticus with other dyrosaurids shows that Phosphatosaurus gavialoides and Sokotosuchus ianwilsoni are the most primitive dyrosaurids, and Rhabdognathus is more closely related to Hyposaurus than to D. phosphaticus.
Empirical model for predicting a catchment-scale metric of surface water transit time in streams
Authors: Van Nieuwenhuyse Erwin E
Published: April 2005

Estimates of average water velocity (vw) extracted from tracer dye studies (vdye) or calculated from velocitydischarge relationships at continuous-flow gauges (vgage) were combined with catchment area (A) and other readily available data for 111 streams throughout the conterminous United States. The resulting data set (n = 305) represented broad ranges of A (65  62 419 km2), mainstem length (Lmax, 15.6867 km), slope (S, 0.1411.5 m·km1), and daily average discharge (Q, 0.09634 m3·s1). A catchment-scale metric of surface water transit time (Tw, Lmaxvdye1) ranged from 0.3 to 40 days, averaging 7.2 days. A bivariate regression model using log10 A and log10 Q explained 83% of the variation in log10 Tw and predicted Tw with an average precision of ±49%. By contrast, a previously published model based on hydraulic geometry relationships overestimated Tw by 100%. Application of my model to five streams nested in a ninth-order (ω = 9) catchment indicated that under dry (September) and wet (March), long-term (19542001) median flow conditions, vw increased with Q (vw ∝ Q0.3) as far downstream as ω = 8 and then remained constant or declined. The slope of this longitudinal vwQ relationship was three times greater than the expected value. Longitudinal velocity gradients in many streams may thus be much steeper than commonly assumed.
Can vessel monitoring system data also be used to study trawling intensity and population depletion? The example of Australia's northern prawn fishery
Authors: Deng Roy , Dichmont Cathy , Milton David , Haywood Mick , Vance David , Hall Natasha , Die David
Published: April 2005

We explore the potential of using data from Australia's northern prawn fishery (NPF) vessel monitoring system(s) (VMS) to examine trawl track, trawling intensity, and stock depletion due to trawling. We simulate VMS data by subsampling global positioning system (GPS) fixes from the NPF fishing vessels at different polling intervals to examine their accuracy in describing trawl tracks. The results of the simulations suggest that VMS data with polling intervals longer than 30 min cannot accurately estimate trawl tracks. The analysis of high-polling-frequency VMS data collected in four (later reduced to three) 6 nautical mile × 6 nautical mile grids that historically received high levels of fishing effort showed that trawling was not random and some areas were trawled up to 28 times in the tiger prawn fishing season and the impact varied among years. The results of a catch-depletion analysis suggest that fishery catch-per-unit-effort and cumulative catch may not be proportional to overall target-species biomass in areas with highly aggregated trawl effort. The VMS data also showed a large number of trawls can occur in productive areas and that trawling impacts on benthos may be quite marked.
Colonization of Phaseolus vulgaris nodules by Agrobacterium-like strains
Authors: Mhamdi Ridha , Mrabet Moncef , Laguerre Gisèle , Tiwari Ravi , Aouani Mohamed Elarbi
Published: April 2005

Non-nodulating Agrobacterium-like strains identified among root nodule isolates of common bean were labeled with gusA, a reporter gene encoding β-glucuronidase (GUS). Bean plants were then co-inoculated with an infective Rhizobium strain and labeled transconjugants of Agrobacterium-like strains. Blue staining of nodules showed that Agrobacterium-like strains were able to colonize these symbiotic organs. Isolation and characterization by restriction fragment length polymorphism analysis of PCR-amplified 16S rRNA genes revealed a mixed population of Rhizobium and Agrobacterium-like strains in all nodules showing GUS activity. PCR amplification of the nifH gene and nodulation tests did not show any evidence of acquisition of symbiotic gene by lateral transfer from Rhizobium to Agrobacterium-like strains. Moreover, these strains were able to invade mature nodules. Based on sequencing of the 16S rRNA gene, one of these Agrobacterium-like strains showed 99.4% sequence similarity with Agrobacterium bv. 1 reference strains and 99% similarity with an Agrobacterium bv. 1 strain isolated from Acacia mollisima in Senegal. Agrobacterium tumefaciens C58 and the disarmed variant AT123 did not show any ability to colonize nodules. Co-inoculation of bean seeds with Agrobacterium and Rhizobium strains did not enhance nodulation and plant yield under controlled conditions.Key words: Agrobacterium, co-inoculation, gusA gene, nodule colonization, Rhizobium.
Serial passage of the opportunistic pathogen Aspergillus flavus through an insect host yields decreased saprobic capacity
Authors: Scully Lisa R , Bidochka Michael J
Published: April 2005

To study the early stages of the effect of host restriction on pathogen evolution, we subjected the opportunistic fungus Aspergillus flavus to a serial propagation scheme, whereby insect-virulent conidia were selected for repeated passage through an insect host (Galleria mellonella larvae) for 5 generations. Of the 35 lineages promulgated through this scheme, there were no consistent changes in virulence, which was measured by percent mortality of the larvae. There were, however, increases in the number of conidia on the insect cadavers (9 of 35 lineages) and decreases in the number of days between death and the appearance of fungal growth on the cadavers (4 of 35 lineages). Notably, most of the lineages (28 of 35 lineages) demonstrated a statistically significant decrease in the diameter of the colonies subcultured onto artificial media, indicating a decreased ability to grow saprobically. Conversely, most of the A. flavus cultures successively grown on agar media (9 of 10 lineages) exhibited no change in colony diameter after 15 rounds of subculturing. Propagation of the opportunist A. flavus through the insect host G. mellonella resulted in a diminished capacity to grow on an alternate substrate, while maintaining or increasing its ability to use the host as a nutrient supply.Key words: Aspergillus flavus, insect pathogen, Galleria mellonella, serial propagation, emerging diseases.
Characterization of aerobic and anaerobic vegetative growth of the food-borne pathogen Bacillus cereus F4430/73 strain
Authors: Rosenfeld Eric , Duport Catherine , Zigha Assia , Schmitt Philippe
Published: April 2005

The Gram-positive bacterium Bacillus cereus is a facultative anaerobe that is still poorly characterized metabolically. In this study, the aerobic vegetative growth and anaerobic vegetative growth of the food-borne pathogen B. cereus F4430/73 strain were compared with those of the genome-sequenced ATCC14579 strain using glucose and glycerol as fermentative and nonfermentative carbon sources, respectively. Uncontrolled batch cultures on several defined media showed that B. cereus strains had high amino acid or pyruvate requirements for anaerobic fermentative growth. In addition, growth performance was considerably improved by maintaining the pH of the culture medium near neutrality. Spectra of fermentation by-products were typically (per mole of glucose) 0.2–0.4 acetate, 1.1–1.4 L-lactate, 0.3–0.4 formate, and 0.05–0.2 ethanol with only traces of succinate, pyruvate, and 2,3-butanediol. These spectra were drastically changed in the presence of 20 mmol nitrate·L–1, which stimulated anaerobic growth. During anaerobic and aerobic respiration, the persistent production of acetate and other by-products indicated overflow metabolisms. This was especially true in glucose-grown cells for which respiratory complex III made only a minor contribution to growth. Surprisingly, oxygen uptake rates linked to the cytochrome c and quinol branches of the respiratory chain were maintained at high levels in anaerobic, respiring, or fermenting cells. Growth and metabolic features of B. cereus F4430/73 are discussed using biochemical and genomic data.Key words: Bacillus cereus, growth, defined media, fermentation, respiration.