bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Activity of
Acanthamoeba castellanii
on Human Platelets and Erythrocytes
Authors: Mattana A. , Alberti L. , Delogu G. , Fiori P. L. , Cappuccinelli P. 
Published: November 2008

ABSTRACT

The effect of
Acanthamoeba
on human platelets and erythrocytes has not been fully elucidated. This paper reports that cell-free supernatants prepared from
A. castellanii
can activate human platelets, causing both a significant increase in the cytosolic free-calcium concentration and platelet aggregation. In addition, we demonstrated that platelet activation depends on the activity of ADP constitutively secreted into the medium by trophozoites. This study also showed that
A. castellanii
can affect human red blood cells, causing hemolysis, and provided evidence that hemolysis occurs in both contact-dependent and contact-independent ways; there are differences in kinetics, hemolytic activity, and calcium dependency between the contact-dependent and contact-independent mechanisms. Partial characterization of contact-independent hemolysis indicated that ADP does not affect the plasma membrane permeability of erythrocytes and that heat treatment of amoebic cell-free supernatant abolishes its hemolytic activity. These findings suggest that some heat-labile molecules released by
A. castellanii
trophozoites are involved in this phenomenon. Finally, our data suggest that human platelets and erythrocytes may be potential cell targets during
Acanthamoeba
infection.
Klebsiella pneumoniaeIncreases the Levels of Toll-Like Receptors 2 and 4 in Human Airway Epithelial Cells
Authors: Regueiro Verónica , Moranta David , Campos Miguel A. , Margareto Javier , Garmendia Junkal , Bengoechea José A. 
Published: November 2008

ABSTRACTAirway epithelial cells act as the first barrier against pathogens. These cells recognize conserved structural motifs expressed by microbial pathogens via Toll-like receptors (TLRs) expressed on the surface. In contrast to the level of expression in lymphoid cells, the level of expression of TLR2 and TLR4 in airway epithelial cells is low under physiological conditions. Here we explored whetherKlebsiella pneumoniaeupregulates the expression of TLRs in human airway epithelial cells. We found that the expression of TLR2 and TLR4 by A549 cells and human primary airway cells was upregulated upon infection withK. pneumoniae. The increased expression of TLRs resulted in enhancement of the cellular response upon stimulation with Pam3CSK4 and lipopolysaccharide, which are TLR2 and TLR4 agonists, respectively.Klebsiella-dependent upregulation of TLR expression occurred via a positive IκBα-dependent NF-κΒ pathway and via negative p38 and p44/42 mitogen-activated protein kinase-dependent pathways. We showed thatKlebsiella-induced TLR2 and TLR4 upregulation was dependent on TLR activation. An isogenic capsule polysaccharide (CPS) mutant did not increase TLR2 and TLR4 expression. Purified CPS upregulated TLR2 and TLR4 expression, and polymyxin B did not abrogate CPS-induced TLR upregulation. Although no proteins were detected in the CPS preparation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and colloidal gold staining, we could not rule out the possibility that traces of protein in our CPS preparation could have been responsible, at least in part, for the TLR upregulation.
Dendritic Cell and NK Cell Reciprocal Cross Talk Promotes Gamma Interferon-Dependent Immunity to Blood-StagePlasmodium chabaudiAS Infection in Mice
Authors: Ing Rebecca , Stevenson Mary M. 
Published: November 2008

ABSTRACTDendritic cells (DCs) are important accessory cells for promoting NK cell gamma interferon (IFN-γ) production in vitro in response toPlasmodium falciparum-infected red blood cells (iRBC). We investigated the requirements for reciprocal activation of DCs and NK cells leading to Th1-type innate and adaptive immunity toP. chabaudiAS infection. During the first week of infection, the uptake of iRBC by splenic CD11c+DCs in resistant wild-type (WT) C57BL/6 mice was similar to that in interleukin 15−/−(IL-15−/−) and IL-12p40−/−mice, which differ in the severity ofP. chabaudiAS infection. DCs from infected IL-15−/−mice expressed costimulatory molecules, produced IL-12, and promoted IFN-γ secretion by WT NK cells in vitro as efficiently as WT DCs. In contrast, DCs from infected IL-12p40−/−mice exhibited alterations in maturation and cytokine production and were unable to induce NK cell IFN-γ production. Coculture of DCs and NK cells demonstrated that DC-mediated NK cell activation required IL-12 and, to a lesser extent, IL-2, as well as cell-cell contact. In turn, NK cells from infected WT mice enhanced DC maturation, IL-12 production, and priming of CD4+T-cell proliferation and IFN-γ secretion. Infected WT mice depleted of NK cells, which exhibit increased parasitemia, had impaired DC maturation and DC-induced CD4+Th1 cell priming. These findings indicate that DC-NK cell reciprocal cross talk is critical for control and rapid resolution ofP. chabaudiAS infection and provide in vivo evidence for the importance of this interaction in IFN-γ-dependent immunity to malaria.
Characterization of the Binding Specificity of K88ac and K88ad Fimbriae of EnterotoxigenicEscherichia coliby Constructing K88ac/K88ad Chimeric FaeG Major Subunits
Authors: Zhang Weiping , Fang Ying , Francis David H. 
Published: November 2008

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) strains expressing K88 (F4) fimbriae are the major cause of diarrhea in young pigs. Three antigenic variants of K88 fimbriae (K88ab, K88ac, and K88ad) have been identified among porcine ETEC strains. Each K88 fimbrial variant shows a unique pattern in binding to different receptors on porcine enterocytes. Such variant specificity in fimbrial binding is believed to be controlled by the major subunit (FaeG) of the K88 fimbriae, because the genes coding for the only other fimbrial subunit are identical among the three variants. Uniqueness in binding to host receptors may be responsible for differences in the virulence levels of porcine diarrhea disease caused by K88 ETEC strains. To better understand the relationships between the structure of FaeG proteins and fimbrial binding function, and perhaps virulence in disease, we constructed and expressed various K88ac/K88adfaeGgene chimeras and characterized the binding activity of each K88 chimeric fimbria. After verifying biosynthesis of the chimeric fimbriae, we examined their binding specificities in bacterial adherence assays by using porcine brush border vesicles that are specific to either the K88ac or K88ad fimbria. Results showed that each fimbria switched binding specificity to that of the reciprocal type when a peptide comprising amino acids 125 to 163 was exchanged with that of its counterpart. Substitutions of a single amino acid within this region negatively affected the binding capacity of each fimbria. These data indicate that the peptide including amino acids 125 to 163 of the FaeG subunit is essential for K88 variant-specific binding.
Characterization of the Mycobacterial NER System Reveals Novel Functions of theuvrD1Helicase
Authors: Güthlein Carolin , Wanner Roger M. , Sander Peter , Davis Elaine O. , Bosshard Martin , Jiricny Josef , Böttger Erik C. , Springer Burkhard 
Published: November 2008

ABSTRACTIn this study, we investigated the role of the nucleotide excision repair (NER) pathway in mycobacterial DNA repair.Mycobacterium smegmatislacking the NER excinuclease componentuvrBor the helicaseuvrD1gene and a double knockout lacking both genes were constructed, and their sensitivities to a series of DNA-damaging agents were analyzed. As anticipated, the mycobacterial NER system was shown to be involved in the processing of bulky DNA adducts and interstrand cross-links. In addition, it could be shown to exert a protective effect against oxidizing and nitrosating agents. Interestingly, inactivation ofuvrBanduvrD1significantly increased marker integration frequencies in gene conversion assays. This implies that in mycobacteria (which lack the postreplicative mismatch repair system) NER, and particularly the UvrD1 helicase, is involved in the processing of a subset of recombination-associated mismatches.
Genome-Wide Identification of H-NS-Controlled, Temperature-Regulated Genes in
Escherichia
coli
K-12
Authors: White-Ziegler Christine A. , Davis Talya R. 
Published: November 2008

ABSTRACT

DNA microarrays demonstrate that H-NS controls 69% of the temperature regulated genes in
Escherichia
coli
K-12. H-NS is shown to be a common regulator of multiple iron and other nutrient acquisition systems preferentially expressed at 37°C and of general stress response, biofilm formation, and cold shock genes highly expressed at 23°C.
Two Kdo-Heptose Regions Identified inHafnia alvei32 Lipopolysaccharide: the Complete Core Structure and Serological Screening of DifferentHafniaO Serotypes
Authors: Lukasiewicz Jolanta , Niedziela Tomasz , Jachymek Wojciech , Kenne Lennart , Lugowski Czeslaw 
Published: November 2008

ABSTRACTHafnia alvei, a gram-negative bacterium, is an opportunistic pathogen associated with mixed hospital infections, bacteremia, septicemia, and respiratory diseases. Various 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo)-containing fragments different from known structures of core oligosaccharides were previously found among fractions obtained by mild acid hydrolysis of someH. alveilipopolysaccharides (LPSs). However, the positions of these segments in the LPS structure were not known. Analysis of de-N,O-acylated LPS by nuclear magnetic resonance spectroscopy and mass spectrometry allowed the determination of the location of a Kdo-containing trisaccharide in the structure ofH. alveiPCM 32 LPS. It was established that the trisaccharide {l-α-d-Hepp-(1→4)-[α-d-Galp6OAc-(1→7)]-α-Kdop-(2→} is an integral part of the outer-core oligosaccharide ofH. alvei32 LPS. The very labile ketosidic linkage between →4,7)-α-Kdopand →2)-Glcpin the core oligosaccharide was identified. Screening for this Kdo-containing trisaccharide was performed on the group of 37 O serotypes ofH. alveiLPSs using monospecific antibodies recognizing the structure. It was established that this trisaccharide is a characteristic component of the outer-core oligosaccharides ofH. alvei2, 32, 600, 1192, 1206, and 1211 LPSs. The weaker cross-reactions with LPSs of strains 974, 1188, 1198, 1204, and 1214 suggest the presence of similar structures in these LPSs, as well. Thus, we have identified new examples of endotoxins among those elucidated so far. This type of core oligosaccharide deviates from the classical scheme by the presence of the structural Kdo-containing motif in the outer-core region.
1,3-Propanediol Dehydrogenase fromKlebsiella pneumoniae: Decameric Quaternary Structure and Possible Subunit Cooperativity
Authors: Marçal David , Rêgo Ana Toste , Carrondo Maria Arménia , Enguita Francisco J. 
Published: November 2008

ABSTRACTKlebsiella pneumoniaeis a nosocomial pathogen frequently isolated from opportunistic infections, especially in clinical environments. In spite of its potential pathogenicity, this microorganism has several metabolic potentials that could be used in biotechnology applications.K. pneumoniaeis able to metabolize glycerol as a sole source of carbon and energy. 1,3-Propanediol dehydrogenase is the core of the metabolic pathway for the use of glycerol. We have determined the crystallographic structure of 1,3-propanediol dehydrogenase, a type III Fe-NAD-dependent alcohol dehydrogenase, at 2.7-Å resolution. The structure of the enzyme monomer is closely related to that of other alcohol dehydrogenases. The overall arrangement of the enzyme showed a decameric structure, formed by a pentamer of dimers, which is the catalytic form of the enzyme. Dimers are associated by strong ionic interactions that are responsible for the highly stable in vivo packing of the enzyme. Kinetic properties of the enzyme as determined in the article would suggest that this decameric arrangement is related to the cooperativity between monomers.
The Ether-Cleaving Methyltransferase System of the Strict Anaerobe
Acetobacterium dehalogenans
: Analysis and Expression of the Encoding Genes
Authors: Schilhabel Anke , Studenik Sandra , Vödisch Martin , Kreher Sandra , Schlott Bernhard , Pierik Antonio Y. , Diekert Gabriele 
Published: November 2008

ABSTRACT

Anaerobic
O
-demethylases are inducible multicomponent enzymes which mediate the cleavage of the ether bond of phenyl methyl ethers and the transfer of the methyl group to tetrahydrofolate. The genes of all components (methyltransferases I and II, CP, and activating enzyme [AE]) of the vanillate- and veratrol-
O
-demethylases of
Acetobacterium dehalogenans
were sequenced and analyzed. In
A. dehalogenans
, the genes for methyltransferase I, CP, and methyltransferase II of both
O
-demethylases are clustered. The single-copy gene for AE is not included in the
O
-demethylase gene clusters. It was found that AE grouped with COG3894 proteins, the function of which was unknown so far. Genes encoding COG3894 proteins with 20 to 41% amino acid sequence identity with AE are present in numerous genomes of anaerobic microorganisms. Inspection of the domain structure and genetic context of these orthologs predicts that these are also
r
eductive
a
ctivases for
c
orrinoid
e
nzymes (RACEs), such as carbon monoxide dehydrogenase/acetyl coenzyme A synthases or anaerobic methyltransferases. The genes encoding the
O
-demethylase components were heterologously expressed with a C-terminal
Strep
-tag in
Escherichia coli
, and the recombinant proteins methyltransferase I, CP, and AE were characterized. Gel shift experiments showed that the AE comigrated with the CP. The formation of other protein complexes with the
O
-demethylase components was not observed under the conditions used. The results point to a strong interaction of the AE with the CP. This is the first report on the functional heterologous expression of acetogenic phenyl methyl ether-cleaving
O
-demethylases.
Spatial Clustering of the Curlin Secretion Lipoprotein Requires Curli Fiber Assembly
Authors: Epstein Elisabeth Ashman , Reizian Margeaux A. , Chapman Matthew R. 
Published: November 2008

ABSTRACTGram-negative bacteria assemble functional amyloid surface fibers called curli. CsgB nucleates the major curli subunit protein, CsgA, into a self-propagating amyloid fiber on the cell surface. The CsgG lipoprotein is sufficient for curlin transport across the outer membrane and is hypothesized to be the central molecule of the curli fiber secretion and assembly complex. We tested the hypothesis that the curli secretion protein, CsgG, was restricted to certain areas of the cell to promote the interaction of CsgA and CsgB during curli assembly. Here, electron microscopic analysis of curli-producing strains showed that relatively few cells in the population contacted curli fibers and that curli emanated from spatially discrete points on the cell surface. Microscopic analysis revealed that CsgG was surface exposed and spatially clustered around curli fibers. CsgG localization to the outer membrane and exposure of the surface domain were not dependent on any othercsg-encoded protein, but the clustering of CsgG required thecsg-encoded proteins CsgE, CsgF, CsgA, and CsgB. CsgG formed stable oligomers in all thecsgmutant strains, but these oligomers were distinct from the CsgG complexes assembled in wild-type cells. Finally, we found that efficient fiber assembly was required for the spatial clustering of CsgG. These results suggest a new model where curli fiber formation is spatially coordinated with the CsgG assembly apparatus.
The Flat-Ribbon Configuration of the Periplasmic Flagella of
Borrelia burgdorferi
and Its Relationship to Motility and Morphology
Authors: Charon Nyles W. , Goldstein Stuart F. , Marko Michael , Hsieh Chyongere , Gebhardt Linda L. , Motaleb M. Abdul , Wolgemuth Charles W. , Limberger Ronald J. , Rowe Nancy 
Published: November 2008

ABSTRACT

Electron cryotomography was used to analyze the structure of the Lyme disease spirochete,
Borrelia burgdorferi
. This methodology offers a new means for studying the native architecture of bacteria by eliminating the chemical fixing, dehydration, and staining steps of conventional electron microscopy. Using electron cryotomography, we noted that membrane blebs formed at the ends of the cells. These blebs may be precursors to vesicles that are released from cells grown in vivo and in vitro. We found that the periplasmic space of
B. burgdorferi
was quite narrow (16.0 nm) compared to those of
Escherichia coli
and
Pseudomonas aeruginosa
. However, in the vicinity of the periplasmic flagella, this space was considerably wider (42.3 nm). In contrast to previous results, the periplasmic flagella did not form a bundle but rather formed a tight-fitting ribbon that wraps around the protoplasmic cell cylinder in a right-handed sense. We show how the ribbon configuration of the assembled periplasmic flagella is more advantageous than a bundle for both swimming and forming the flat-wave morphology. Previous results indicate that
B. burgdorferi
motility is dependent on the rotation of the periplasmic flagella in generating backward-moving waves along the length of the cell. This swimming requires that the rotation of the flagella exerts force on the cell cylinder. Accordingly, a ribbon is more beneficial than a bundle, as this configuration allows each periplasmic flagellum to have direct contact with the cell cylinder in order to exert that force, and it minimizes interference between the rotating filaments.
YtxR Acts as an Overriding Transcriptional Off Switch for the
Yersinia enterocolitica
Ysc-Yop Type 3 Secretion System
Authors: Axler-DiPerte Grace L. , Hinchliffe Stewart J. , Wren Brendan W. , Darwin Andrew J. 
Published: November 2008

ABSTRACT

The
Yersinia enterocolitica
YtxR protein is a LysR-type transcriptional regulator that induces expression of the
ytxAB
locus, which encodes a putative ADP-ribosylating toxin. The
ytxR
and
ytxAB
genes are not closely linked in the
Y. enterocolitica
chromosome, and whereas
ytxR
is present in all sequenced
Yersinia
spp., the
ytxAB
locus is not. These observations suggested that there might be other YtxR-regulon members besides
ytxAB
and prompted us to investigate coregulated genes and gene products by using transcriptional and proteomic approaches. Microarray and reverse transcription-PCR analysis showed that YtxR strongly activates expression of the
yts2
locus, which encodes a putative type 2 secretion system, as well as several uncharacterized genes predicted to encode extracytoplasmic proteins. Strikingly, we also discovered that under Ysc-Yop type 3 secretion system-inducing conditions, YtxR prevented the appearance of Yop proteins in the culture supernatant. Microarray and
lacZ
operon fusion analysis showed that this was due to specific repression of
ysc-yop
gene expression. YtxR was also able to repress VirF-dependent Φ(
yopE-lacZ
) and Φ(
yopH-lacZ
) expression in a strain lacking the virulence plasmid, which suggested a direct repression mechanism. This was supported by DNase I footprinting, which showed that YtxR interacted with the
yopE
and
yopH
control regions. Therefore, YtxR is a newly identified regulator of the
ysc-yop
genes that can act as an overriding off switch for this critical virulence system.
Genome Sequence of the Probiotic Bacterium
Bifidobacterium animalis
subsp.
lactis
AD011
Authors: Kim Jihyun F. , Jeong Haeyoung , Yu Dong Su , Choi Sang-Haeng , Hur Cheol-Goo , Park Myeong-Soo , Yoon Sung Ho , Kim Dae-Won , Ji Geun Eog , Park Hong-Seog , Oh Tae Kwang 
Published: November 2008

ABSTRACT

Bifidobacterium animalis
subsp.
lactis
is a probiotic bacterium that naturally inhabits the guts of most mammals, including humans. Here we report the complete genome sequence of
B. animalis
subsp.
lactis
AD011 that was isolated from an infant fecal sample. Biological functions encoded in a single circular chromosome of 1,933,695 bp, smallest among the completely sequenced bifidobacterial genomes, are suggestive of their probiotic functions, such as utilization of bifidogenic factors and a variety of glycosidic enzymes and biosynthesis of polysaccharides.
The impact of temporary employment and job tenure on work-related sickness absence
Authors: Tompa E , Scott-Marshall H , Fang M 
Published: November 2008

Objectives:To investigate the impact of temporary employment and job tenure on work-related sickness absence of 1 week or more.Methods:A longitudinal analysis was undertaken of the time to work-related sickness absence from the start of a job using the Canadian Survey of Labour and Income Dynamics. The sample consisted of 4777 individuals who experienced 7953 distinct job episodes and 167 absences. There were 114 488 person-job-month observational units. The major variables of interest in this study were a variable identifying whether the job was temporary or permanent, and tenure on the job.Results:Individuals in temporary jobs were as likely to have a work-related sickness absence as individuals in permanent jobs. Individuals with job tenure of 4–6 months were 64% less likely to have an absence than individuals with longer tenures. Individuals in a union were more likely to have an absence. Firm size was not associated with absence.Conclusions:Previous studies have suggested that temporary employment and job tenure are associated with work-related health risk exposures and the ability to take a sickness absence, but these studies have not considered the nature of the employment contract in a longitudinal framework. This analysis did not find temporary employment to be associated with differential absence rate after controlling for tenure, prior health status, and several other individual and job characteristics. Short tenure is negatively related to the probability of work-related sickness absence, union membership is positively related, and firm size is not related to this variable.
Depression in primary care: three key challenges
Authors: Lester H , Howe A 
Published: November 2008

AbstractThe recognition and treatment of depression is a challenging area of clinical practice, especially in primary care where there are many patients with various presentations and a multitude of causes for distress. The prevalence of depression is increasing, and it is predicted to become second only to ischaemic heart disease as a cause of morbidity worldwide. Fortunately, the research evidence on effective approaches is increasing. This article looks at how we can best identify, treat and understand the perspectives of people with depression who are seen in primary care.Simple questionnaires can provide effective screening in generalist settings, particularly when targeting high-risk groups such as those with cardiovascular comorbidity or recurrent unexplained symptoms. Guidelines now exist for use of antidepressants and cognitive behavioural therapy for mild to moderate depression, although the latter needs effective policy implementation in clinical practice to maximise its impact for patients. However, there is also consistent evidence from service users that people with depression want individualised care which takes into account their preferences and concerns, even if this entails departure from guidelines. Adherence to treatment is low in many studies, and remodelling of services can easily lead to gaps in consistent approaches to personal care.The research challenges for the future include clarification of which patient groups merit proactive screening, how to enhance adherence, and the relative merits and outcomes of pharmacological versus behavioural therapies. Changes in policy and service configuration can improve or destabilise effective care, but high-quality and flexible intervention with patients with mild to moderate depression is likely to be cost-effective in view of the high prevalence and disease burden of this distressing problem.