bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gallinacin-3, an Inducible Epithelial β-Defensin in the Chicken
Authors: Zhao Chengquan , Nguyen Tung , Liu Lide , Sacco Randy E. , Brogden Kim A. , Lehrer Robert I. 
Published: July 2002

ABSTRACTGallinacin-3 and gallopavin-1 (GPV-1) are newly characterized, epithelial β-defensins of the chicken (Gallus gallus) and turkey (Meleagris gallopavo), respectively. In normal chickens, the expression of gallinacin-3 was especially prominent in the tongue, bursa of Fabricius, and trachea. It also occurred in other organs, including the skin, esophagus, air sacs, large intestine, and kidney. Tracheal expression of gallinacin-3 increased significantly after experimental infection of chickens withHaemophilus paragallinarum, whereas its expression in the tongue, esophagus, and bursa of Fabricius was unaffected. The precursor of gallinacin-3 contained a long C-terminal extension not present in the prepropeptide. By comparing the cDNA sequences of gallinacin-3 and GPV-1, we concluded that a 2-nucleotide insertion into the gallinacin-3 gene had induced a frameshift that read through the original stop codon and allowed the chicken propeptide to lengthen. The striking structural resemblance of the precursors of β-defensins to those of crotamines (highly toxic peptides found in rattlesnake venom) supports their homology, even though defensins are specialized to kill microorganisms and crotamines are specialized to kill much larger prey.
Shear Stress Prevents Fibronectin Binding Protein-Mediated
Staphylococcus aureus
Adhesion to Resting Endothelial Cells
Authors: Reddy Kesav , Ross Julia M. 
Published: July 2002

ABSTRACT

Fibronectin binding proteins (FnBP) on the surface of
Staphylococcus aureus
have previously been shown to mediate adherence of the organism to resting endothelial cells in static adhesion assays. However, in this study using well-defined flow assays, we demonstrate that physiologic levels of shear stress prevent FnBP-mediated adhesion of
S. aureus
8325-4 to resting endothelial cells. This result suggests that mechanical forces present in vivo may influence the ability of staphylococci to bind endothelial cell surfaces.
Requirement for Capsule in Colonization by
Streptococcus pneumoniae
Authors: Magee Ashalla D. , Yother Janet 
Published: July 2002

ABSTRACT

Nasopharyngeal colonization is a necessary first step in the pathogenesis of
Streptococcus pneumoniae
. Using isolates containing defined mutations in the
S. pneumoniae
capsule locus, we found that expression of the capsular polysaccharide is essential for colonization by the type 2 strain D39 and the type 3 strains A66 and WU2. Nonencapsulated derivatives of each of these strains were unable to colonize BALB/cByJ mice. Similarly, type 3 mutants that produced <6% of the parental amounts of capsule could not colonize. Capsule production equivalent to that of the parent strain was not required for efficient colonization, however, as type 3 mutants producing approximately 20% of the parental amounts of capsule colonized as effectively as the parent. This 80% reduction in capsule level had only a minimal effect on intraperitoneal virulence but caused a significant reduction in virulence via the intravenous route. In the X-linked immunodeficient CBA/N mouse, the type 3 mutant producing ∼20% of the parental amount of capsule (AM188) was diminished in its ability to cause invasive disease and death following intranasal inoculation. Following intravenous or intraperitoneal challenge, however, only extended survival times were observed. Our results demonstrate an additional role for capsule in the pathogenesis of
S. pneumoniae
and show that isolates producing reduced levels of capsule can remain highly virulent.
Complete DNA Sequence of
Yersinia enterocolitica
Serotype 0:8 Low-Calcium-Response Plasmid Reveals a New Virulence Plasmid-Associated Replicon
Authors: Snellings Norma J. , Popek Michael , Lindler Luther E. 
Published: July 2002

ABSTRACT

The complete nucleotide sequence and organization of the
Yersinia enterocolitica
serotype 0:8 low-calcium-response (LCR) plasmid, pYVe8081, were determined. The 67,720-bp plasmid encoded all the genes known to be part of the LCR stimulon except for
ylpA
. Eight of 13 intact open reading frames of unknown function identified in pYVe8081 had homologues in
Yersinia pestis
plasmid pCD1 or in
Y. enterocolitica
serotype 0:9 plasmid pYVe227. A region of approximately 17 kbp showed no DNA identity to pCD1 or pYVe227 and contained six potential new genes, a possible new replicon, and two intact insertion sequence (IS) elements. One intact IS element, IS
Yen1
, was a new IS belonging to the IS
256
family. Several vestigial IS elements appeared different from the IS distribution seen in the other LCR plasmids. The RepA proteins encoded by
Y. enterocolitica
serotype 0:8 pYVeWA and pYVe8081 were identical. The putative pYVe8081 replicon showed significant homology to the IncL/M replicon of pMU407.1 but was only distantly related to the replicons of pCD1 and pYVe227. In contrast, the putative partitioning genes of pYVe8081 showed 97% DNA identity to the
spy/sopABC
loci of pCD1 and pYVe227. Sequence analysis suggests that
Yersinia
LCR plasmids are from a common ancestor but that
Y. enterocolitica
serotype 0:8 plasmid replicons may have evolved independently via cointegrate formation following a transposition event. The change in replicon structure is predicted to change the incompatibility properties of
Y. enterocolitica
serotype 0:8 plasmids from those of
Y. enterocolitica
serotype 0:9 and
Y. pestis
LCR plasmids.
Cytolethal Distending Toxin Demonstrates Genotoxic Activity in a Yeast Model
Authors: Hassane Duane C. , Lee Robert B. , Mendenhall Michael D. , Pickett Carol L. 
Published: July 2002

ABSTRACTCytolethal distending toxins (CDTs) are multisubunit proteins produced by a variety of bacterial pathogens that cause enlargement, cell cycle arrest, and apoptosis in mammalian cells. While their function remains uncertain, recent studies suggest that they can act as intracellular DNases in mammalian cells. Here we establish a novel yeast model for understanding CDT-associated disease. Expression of the CdtB subunit in yeast causes a G2/M arrest, as seen in mammalian cells. CdtB toxicity is not circumvented in yeast genetically altered to lack DNA damage checkpoint control or that constitutively promote cell cycle progression via mutant Cdk1, because CdtB causes a permanent type of damage that results in loss of viability. Finally, we establish that CDTs are likely to be potent genotoxins, as indicated by in vivo degradation of chromosomal DNA associated with expression of CdtB—suggesting that the varied distribution of CDT in bacteria implicates many human pathogens as possessors of genotoxic activity.
Vibrio cholerae
OmpU and OmpT Porins Are Differentially Affected by Bile
Authors: Wibbenmeyer Jamie A. , Provenzano Daniele , Landry Candice F. , Klose Karl E. , Delcour Anne H. 
Published: July 2002

ABSTRACT

OmpT and OmpU are pore-forming proteins of the outer membrane of
Vibrio cholerae
, a pathogen that colonizes the intestine and produces cholera. Expression of the
ompU
and
ompT
genes is under the regulation of ToxR, a transmembrane transcriptional activator that also controls expression of virulence factors. It was recently shown that bile stimulates the ToxR-mediated transcription of
ompU
and that
ompU
-expressing strains are more resistant to bile and anionic detergents than
ompT
-expressing cells. In order to further understand the role of the OmpT and OmpU porins in the ability of
V. cholerae
to survive and colonize the host intestine, we examined the outer membrane permeability of cells expressing only
ompU
or only
ompT
or both genes in the absence and in the presence of bile. By comparing various strains in terms of the rate of degradation of the β-lactam antibiotic cephaloridine by the periplasmic β-lactamase, we found that the permeation of the antibiotic through the outer membrane of OmpU-containing cells was slower than the permeation in OmpT-containing cells. In addition, the OmpU-mediated outer membrane permeability was not affected by external bile, while the OmpT-mediated antibiotic flux was reduced by bile in a concentration-dependent manner. Our results confirm that OmpT and OmpU provide a passageway for hydrophilic solutes through the outer membrane and demonstrate that bile might interfere with this traffic in OmpT-producing cells by functionally inhibiting the OmpT pore. The insensitivity of OmpU to bile may be due to its small pore size and may provide an explanation for the resistance of OmpU-producing cells to bile in vivo.
Serum Stimulates Growth of and Proteinase Secretion byAspergillus fumigatus
Authors: Gifford Anna H. T. , Klippenstein Jodine R. , Moore Margo M. 
Published: July 2002

ABSTRACTSerum contains iron-binding proteins, which inhibit the growth of most pathogenic microorganisms, including fungi. The purpose of this research was to investigate the effect of serum on growth of the opportunistic fungal pathogenAspergillus fumigatus. Supplementing minimal essential medium (MEM) with up to 80% human serum or up to 80% fetal bovine serum (FBS) stimulated growth and increased the amount ofA. fumigatusdry biomass approximately fourfold. In addition, a 100-fold increase in proteinase secretion, as measured by azocasein hydrolysis, was observed when 10% human serum or 10% FBS was added to MEM. The fungal proteinases secreted in serum-containing media were shown to degrade3H-labeled basal lamina proteins. The factor in serum that stimulated proteinase secretion was larger than 10 kDa and was 85% inactivated when the serum was heated for 30 min at 66°C. The proportions of proteinases of each catalytic class secreted byA. fumigatusin the presence of serum were different from the proportions secreted in media containing single proteins. Proteinase secretion did not result from increased protein concentration in the medium per se because bovine serum albumin (BSA) at a concentration equivalent to the concentration of serum produced only 20% of the proteinase activity per milligram (dry weight) that was produced by FBS. Addition of BSA plus 100 μM FeCl3to MEM resulted in the same level of growth as addition of serum, indicating that a combination of nutritional factors in serum may stimulate growth. However, the level of proteinase secretion was still only 30% of the level observed with FBS. These data indicate that serum does not inhibit the growth ofA. fumigatusand that the nutrients in serum result in high levels of proteinase secretion, potentially increasing the invasiveness of this species.
Increased CD8+-T-Cell Expression and a Type 2 Cytokine Pattern during the Muscular Phase ofTrichinellaInfection in Humans
Authors: Gomez Morales Maria Angeles , Mele Raffaella , Sanchez Massimo , Sacchini Daria , De Giacomo Marzia , Pozio Edoardo 
Published: July 2002

ABSTRACTCell-mediated immunity during the muscular phase ofTrichinellainfection in humans was studied. Cell proliferation, the phenotypic changes in the T-cell population, and expression and production of cytokines were examined by using peripheral blood mononuclear cells (PBMC) collected at different times postinfection from 10 individuals who had acquiredTrichinella spiralisand five individuals who had acquiredTrichinella britoviin two distinct outbreaks.T. spiralisandT. britovicrude worm extracts induced proliferation of PBMC fromT. spiralis- andT. britovi-infected donors. Cytokine gene expression showed a predominant type 2 pattern for the entire period of infection studied, although gamma interferon (IFN-γ) was expressed. Interleukin-2 (IL-2), IL-5, IL-10, and IFN-γ production was found in PBMC of all donors. There was a good correspondence between the cytokine expression and production patterns. Changes in PBMC composition, with a trend toward an increase in CD8+lymphocyte counts, were observed.
In Vivo Complementation of
ureB
Restores the Ability of
Helicobacter pylori
To Colonize
Authors: Eaton Kathryn A. , Gilbert Joanne V. , Joyce Elizabeth A. , Wanken Amy E. , Thevenot Tracy , Baker Patrick , Plaut Andrew , Wright Andrew 
Published: July 2002

ABSTRACT

The objective of this study was to determine (i) if complementation of
ureB
-negative
Helicobacter pylori
restores colonization and (ii) if urease is a useful reporter for promoter activity in vivo. Strains used were M6, M6Δ
ureB
, and 10 recombinant derivatives of M6 or M6Δ
ureB
in which urease expression was under the control of different
H. pylori
promoters. Mice were orally inoculated with either the wild type or one of the mutant strains, and colonization, in vivo urease activity, and extent of gastritis were determined. Of eight M6Δ
ureB
recombinants tested, four colonized mice. Of those, three had the highest in vitro urease activity of any of the recombinants, significantly different from that of the noncolonizing mutants. The fourth colonizing recombinant, with
ureB
under control of the
cag-15
promoter, had in vitro urease activity which did not differ significantly from the noncolonizing strains. In vivo, urease activities of the four colonizing transformants and the wild-type control were indistinguishable. There were no differences in gastritis or epithelial lesions between mice infected with M6 and those infected with the transformants. These results demonstrate that recovery of urease activity can restore colonizing ability to urease-negative
H. pylori
. They also suggest that
cag-15
is upregulated in vivo, as was previously suggested by demonstrating that it is upregulated upon contact with epithelial cells. Finally, our results suggest that total urease activity and colonization density do not contribute to gastritis due to
H. pylori.
Role of Cholesterol and the Ganglioside GM
1
in Entry and Short-Term Survival of
Brucella suis
in Murine Macrophages
Authors: Naroeni Aroem , Porte Françoise 
Published: July 2002

ABSTRACT

Brucella
species are gram-negative, facultative intracellular bacteria that infect humans and animals. These organisms can survive and replicate within a membrane-bound compartment inside professional and nonprofessional phagocytic cells. Inhibition of phagosome-lysosome fusion has been proposed as a mechanism for intracellular survival in both types of cells. We have previously shown that the maturation inhibition of the
Brucella
-containing phagosome appears to be restricted at the phagosomal membrane, but the precise molecular mechanisms and factors involved in this inhibition have yet to be identified. Interestingly, recent studies have revealed that caveolae or lipid rafts are implicated in the entry of some microorganisms into host cells and mediate an endocytic pathway avoiding fusion with lysosomes. In this study, we investigated the role of cholesterol and the ganglioside GM
1
, two components of lipid rafts, in entry and short-term survival of
Brucella suis
in murine macrophages, by using cholesterol-sequestering (filipin and β-methyl cyclodextrin) and GM
1
-binding (cholera toxin B) molecules. Our results suggest that lipid rafts may provide a portal for entry of
Brucella
into murine macrophages under nonopsonic conditions, thus allowing phagosome-lysosome fusion inhibition, and provide further evidence to support the idea that the phagosome maturation inhibition is restricted at the phagosomal membrane.
Differences in Innate Immune Responses (In Vitro) to HeLa Cells Infected with Nondisseminating Serovar E and Disseminating Serovar L2 ofChlamydia trachomatis
Authors: Dessus-Babus Sophie , Darville Toni L. , Cuozzo Francis P. , Ferguson Kaethe , Wyrick Priscilla B. 
Published: July 2002

ABSTRACTThe inflammatory response associated withChlamydia trachomatisgenital infections is thought to be initiated by the release of proinflammatory cytokines from infected epithelial cells. This study focuses on the interactions betweenC. trachomatis-infected HeLa cells and immune cells involved in the early stages of infection, i.e., neutrophils and macrophages. First, we showed that the expression of interleukin-11 (IL-11), an anti-inflammatory cytokine mainly active on macrophages, was upregulated at the mRNA level in the genital tracts of infected mice. Second, incubation of differentiated THP-1 (dTHP-1) cells or monocyte-derived macrophages (MdM) with basal culture supernatants fromC. trachomatisserovar E- or serovar L2-infected HeLa cells resulted in macrophage activation with a differential release of tumor necrosis factor alpha (TNF-α) and upregulation of indoleamine 2,3-deoxygenase (IDO) but not of Toll-like receptor 2 and 4 mRNA expression. Third, coculture of infected HeLa cells with dTHP-1 cells resulted in a reduction in chlamydial growth, which was more dramatic for serovar E than for L2 and which was partially reversed by the addition of anti-TNF-α antibodies for serovar E or exogenous tryptophan for both serovars but was not reversed by the addition of superoxide dismutase or anti-IL-8 or anti-IL-1β antibodies. A gamma interferon-independent IDO mRNA upregulation was also detected in dTHP-1 cells from infected cocultures. Lastly, with a two-stage coculture system, we found that (i) supernatants from neutrophils added to the apical side of infected HeLa cell cultures were chlamydicidal and induced MdM to express antichlamydial activity and (ii) although polymorphonuclear leukocytes released more proinflammatory cytokines in response to serovar E- than in response to L2-infected cells, MdM were strongly activated by serovar L2 infection, indicating that the early inflammatory response generated with a nondisseminating or a disseminating strain is different.
Reevaluation of the Role of
HWP1
in Systemic Candidiasis by Use of
Candida albicans
Strains with Selectable Marker
URA3
Targeted to the
ENO1
Locus
Authors: Sundstrom Paula , Cutler Jim E. , Staab Janet F. 
Published: July 2002

ABSTRACT

Previous evaluation of
HWP1
in systemic candidiasis in CBA/J mice was done with
Candida albicans
strains with differing genetic locations of
URA3
as a result of Ura-blaster mutagenesis. In this study, the presence of
HWP1
and the location of
URA3
contributed to the severity of murine systemic candidiasis in BALB/c mice.
Cytokines Induce Indoleamine 2,3-Dioxygenase Expression in Human Atheroma-Associated Cells: Implications for PersistentChlamydophila pneumoniaeInfection
Authors: Sakash Jessica B. , Byrne Gerald I. , Lichtman Andrew , Libby Peter 
Published: July 2002

ABSTRACTThis study shows that vascular smooth muscle cells express significantly higher levels of gamma interferon-inducible indoleamine 2,3-dioxygenase (IDO) activity than endothelium or mononuclear cells. Since IDO activity is linked to persistentChlamydophila pneumoniaeinfection, our results suggest that smooth muscle cells may be an important reservoir of that organism in atherosclerosis.
Conjugative Junctions in RP4-Mediated Mating of
Escherichia coli
Authors: Samuels A. Lacey , Lanka Erich , Davies Julian E. 
Published: July 2002

ABSTRACT

The physical association of bacteria during conjugation mediated by the IncPα plasmid RP4 was investigated.
Escherichia coli
mating aggregates prepared on semisolid medium were ultrarapidly frozen using copper block freezing, followed by freeze substitution, thin sectioning, and transmission electron microscopy. In matings where the donor bacteria contained conjugative plasmids, distinctive junctions were observed between the outer membranes of the aggregates of mating cells. An electron-dense layer linked the stiffly parallel outer membranes in the junction zone, but there were no cytoplasmic bridges nor apparent breaks in the cell walls or membranes. In control experiments where the donors lacked conjugative plasmids, junctions were not observed. Previous studies have shown that plasmid RP4 carries operons for both plasmid DNA processing (Tra1) and mating pair formation (Tra2). In matings where donor strains carried Tra2 only or Tra2 plus the pilin-processing protease TraF, junctions were found but they were shorter and more interrupted than the wild type. If the donor strain had the pilin gene knocked out (
trbC
), junctions were still found. Thus, it appears that the electron-dense layer between the outer membranes of the conjugating cells is not composed of pilin.
Role of the
Azotobacter vinelandii
Nitrogenase-Protective Shethna Protein in Preventing Oxygen-Mediated Cell Death
Authors: Maier R. J. , Moshiri F. 
Published: July 2002

ABSTRACT

Azotobacter vinelandii
strains lacking the nitrogenase-protective Shethna protein lost viability upon carbon-substrate deprivation in the presence of oxygen. This viability loss was dependent upon the N
2
-fixing status of cultures (N
2
-fixing cells lost viability, while non-N
2
-fixing cells did not) and on the ambient O
2
level. Supra-atmosheric O
2
tensions (40% partial pressure) decreased the viable cell number of the mutant further, and the mutant had a slightly higher spontaneous mutation frequency than the wild type in the high-O
2
conditions. Iron starvation conditions, which resulted in fourfold-reduced superoxide dismutase levels, were also highly detrimental to the viability of the protective protein mutants, but these conditions did not affect the viability of the wild-type strain. Nitrogenase or other powerful reductants associated with N
2
fixation may be sources of damaging partially reduced oxygen species, and the production of such species are perhaps minimized by the Shethna protein.
Chromosomal and Extrachromosomal Synthesis of Exfoliative Toxin from
Staphylococcus hyicus
Authors: Sato Hisaaki , Watanabe Takao , Higuchi Kohichi , Teruya Kuniaki , Ohtake Ayumi , Murata Yasuko , Saito Hiroshi , Aizawa Chikara , Danbara Hirofumi , Maehara Nobutoshi 
Published: July 2002

ABSTRACT

Evidence for the existence of two molecular species of exfoliative toxin (ET) synthesized by
Staphylococcus hyicus
(SHET) under chromosomal and plasmid control is presented. Serological evidence that these molecular species of toxins are distinct from each other is given. The molecular weights of SHET from plasmidless strain P-1 (SHETA) and from plasmid-carrying strains P-10 and P-23 (SHETB) were almost equal. Both of the serotypes of SHET exhibited exfoliation in 1-day-old chickens. The plasmid-cured (P
−
) substrains (P-23C1 and P-23C2) of
S. hyicus
P-23 did not cause exfoliation in 1-day-old chickens, whereas P
−
substrains (P-10C1 and P-10C2) of strain P-10 caused exfoliation, but they decreased their exfoliative activity. These findings suggest that SHETB was synthesized along with SHETA by strain P-10, whereas the P-23 strain synthesized SHETB alone. The plasmid-carrying strain (P-23) as well as the plasmidless strain (P-1) exhibited the typical clinical signs of exudative epidermitis in pigs. However, plasmid-cured (P
−
) substrains of P-23 (P23C1 and P23C2) did not exhibit the typical clinical signs of exudative epidermitis. These findings suggest that SHETA is synthesized under chromosomal control and SHETB is synthesized under plasmid control and that SHET-producing strains can be divided into three groups: SHETA-producing strains, SHETB-producing strains, and strains producing both toxins.