bluuebunny/crossref_metadata_2025_split huggingface dataset:
Avian Risk Assessment: Effects of Perching Height and Detectability
Authors: Blumstein Daniel T. , Fernández‐Juricic Esteban , LeDee Olivia , Larsen Elisabeth , Rodriguez‐Prieto Iñaki , Zugmeyer Claire 
Published: April 2004

AbstractWe studied two components of predator risk assessment in birds. While many species are limited to seeking safety under cover or under ground, some birds can fly away from their predators and escape to trees. If birds in fact ‘feel’ safer (e.g. perceive less risk) in trees, we would expect them to tolerate closer approach by a potential terrestrial predator. Another component of safety is at which point the animal detects an approaching threat, which we expected to increase with eye size, assuming eye size is a surrogate for visual acuity. We used the distance birds moved away from an approaching human [flight initiation distance (FID)] as a metric to determine whether birds associated a lower risk of predation by being in trees, and we used the distance at which birds first displayed alert behaviors from an approaching human (alert distance) to determine if birds with larger eyes had higher detection distances. Although some species were affected by tree height, we found no clear pattern that birds assessed themselves to be at a lower risk of predation when they were ≥3 m above the ground compared with being <3 m above ground. In the 10 species for which height had any significant effect on FID, birds ≥3 m off the ground had greater FIDs in six species, but the remaining three species had the opposite response. While we found a significant positive relationship between eye size and alert distance in 23 species, the relationship was not present in a phylogenetic analysis using independent contrasts, which suggests that the apparent relationship was influenced strongly by the association between the studied species. Together, these results suggest that birds do not obviously associate being in a tree with safety, and that variations in visual acuity, per se, cannot be used as a general indicator of differences in alert distances, as previously suggested in the literature.
The Influence of Predator Sex on Chemically Mediated Antipredator Response in the Wolf SpiderPardosa milvina(Araneae: Lycosidae)
Authors: Lehmann Leilani M. , Walker Sean E. , Persons Matthew H. 
Published: April 2004

AbstractThe wolf spider,Pardosa milvina, reduces activity in the presence of chemical cues (silk and excreta) from a larger predatory wolf spider,Hogna helluo.Hognais sexually dimorphic in body size and males and females differ in their propensity to attack prey. Consequently, each sex may present different levels of risk toPardosa. We measured predation risk ofPardosain the presence of male or femaleHogna. We also assessedPardosaantipredator responses and survival in the presence or absence of previously deposited chemical cues from male or femaleHogna. In the absence of predator chemical cues,Pardosasurvived significantly longer in the presence of maleHognacompared with femaleHogna. We then assessedPardosasurvival in the presence of chemical cues from eachHognasex by placingPardosain containers previously occupied by a femaleHogna, a maleHogna, or noHogna(control). We then introduced a femaleHognainto each container and measured predation latency.Pardosasurvived significantly longer in the presence of female and male cues compared with the control treatment. Median survival time ofPardosawas over four times longer on substrates with femaleHognacues compared with male cues, but this difference was not statistically significant. We testedPardosaactivity levels in the presence of chemical cues from male or femaleHogna. BothHognasexes were maintained in separate containers after which we placed an adult femalePardosain one of the containers or a blank control container.Pardosasignificantly decreased activity in the presence of chemical cues from either sex relative to the control. Activity was lowest on substrates with femaleHognacues, but not significantly lower than on substrates with maleHognacues. Results suggest that chemical information from male or femaleHognasignificantly reducesPardosaactivity which results in increased survival.
The clinical home community: a model for community‐based education
Authors: Williams‐Barnard C. L. , Sweatt A. H. , Harkness G. A. , DiNapoli P. 
Published: April 2004

AbstractBackground:  Escalating health care costs, racial inequities and socioeconomic disparities have limited access for many to even the barest of health care services. The paradigm shift to a health promotion, disease prevention, and health restoration model within a community‐based framework demands greater integrated learning experiences for nursing students that are centred where clients live, work, and play.Aim:  To describe the process of developing, implementing and evaluating a rural New England University's experience of piloting a clinical home community model within its existing baccalaureate curriculum.Content:  The model describes how it is possible to break free from traditional acute care settings in hospitals and mental health institutions. Students are provided with maternal‐child and adult mental health experiences that are available in a targeted clinical home community setting where consumers are increasingly seeking health care. The concepts that directed curriculum revision from a traditional to a community‐based educational framework are discussed.Outcomes:  Strengths and limitations of the model are presented within the context of student, faculty and consumer partnerships. Implications for global development of the clinical home community model in nursing are proposed.
Local and Systemic Antibody Responses in Mice Immunized Intranasally with Native and Detergent-Extracted Outer Membrane Vesicles fromNeisseria meningitidis
Authors: Guthrie Terry , Wong Simon Y. C. , Liang Bin , Hyland Lisa , Hou Sam , Høiby E. Arne , Andersen Svein Rune 
Published: April 2004

ABSTRACTThe mouse humoral immune response toward native or detergent-extracted outer membrane vesicles (NOMVs and DOMVs, respectively) fromNeisseria meningitidiswas determined after intranasal immunization. Both preparations elicited high frequencies of NOMV-specific antibody-forming cells (AFCs) locally in the nasal associated lymphoid tissue (NALT) after three or four weekly doses. The diffuse NALT (D-NALT) contained ca. 10-fold more NOMV-specific AFCs than those observed in the mediastinal lymph node, spleen, and bone marrow. AFCs observed in the D-NALT were primarily immunoglobulin A positive (IgA+) and were maintained for at least 1 month. In contrast, the organized NALT (O-NALT) contained low numbers of AFCs, and the response was relatively short-lived. In other lymphoid tissues, AFCs producing various IgG subclasses and IgM were present with IgG2b-producing AFCs being dominant or codominant with IgA or IgG2a. In serum and in all of the tissues examined, with the exception of the NALT, NOMVs clearly induced a stronger antibody response and a broader range of antibody isotypes than DOMVs. The development of NOMV-specific AFCs in spleen and bone marrow after intranasal immunization was slow compared to intravenous immunization but, once established, the intranasally elicited responses increased steadily for at least 75 days. NOMV-specific antibodies induced via several routes of immunization had high bactericidal activities in serum. Our results indicated that intranasally administered OMVs induced strong local and systemic antibody responses in mice that were relatively long-lived.
Cloning and Characterization of the Gene Encoding the Major Cell-Associated Phospholipase A of
Legionella pneumophila
,
plaB
, Exhibiting Hemolytic Activity
Authors: Flieger Antje , Rydzewski Kerstin , Banerji Sangeeta , Broich Markus , Heuner Klaus 
Published: April 2004

ABSTRACT

Legionella pneumophila
, the causative agent of Legionnaires' disease, is an intracellular pathogen of amoebae, macrophages, and epithelial cells. The pathology of
Legionella
infections involves alveolar cell destruction, and several proteins of
L. pneumophila
are known to contribute to this ability. By screening a genomic library of
L. pneumophila
, we found an additional
L. pneumophila
gene,
plaB
, which coded for a hemolytic activity and contained a lipase consensus motif in its deduced protein sequence. Moreover,
Escherichia coli
harboring the
L. pneumophila plaB
gene showed increased activity in releasing fatty acids predominantly from diacylphospho- and lysophospholipids, demonstrating that it encodes a phospholipase A. It has been reported that culture supernatants and cell lysates of
L. pneumophila
possess phospholipase A activity; however, only the major secreted lysophospholipase A PlaA has been investigated on the molecular level. We therefore generated isogenic
L. pneumophila plaB
mutants and tested those for hemolysis, lipolytic activities, and intracellular survival in amoebae and macrophages. Compared to wild-type
L. pneumophila
, the
plaB
mutant showed reduced hemolysis of human red blood cells and almost completely lost its cell-associated lipolytic activity. We conclude that
L. pneumophila plaB
is the gene encoding the major cell-associated phospholipase A, possibly contributing to bacterial cytotoxicity due to its hemolytic activity. On the other hand, in view of the fact that the
plaB
mutant multiplied like the wild type both in U937 macrophages and in
Acanthamoeba castellanii
amoebae,
plaB
is not essential for intracellular survival of the pathogen.
Pattern of Cytokine Responses to Gram-Positive and Gram-Negative Commensal Bacteria Is Profoundly Changed when Monocytes Differentiate into Dendritic Cells
Authors: Karlsson Helen , Larsson Pia , Wold Agnes E. , Rudin Anna 
Published: April 2004

ABSTRACTThe normal gastrointestinal bacterial flora is crucial for the maturation of acquired immunity via effects on antigen-presenting cells (APCs). Here we investigated how two types of APCs, monocytes and dendritic cells (DCs), react to different bacterial strains typical of the commensal intestinal microflora. Purified human monocytes and monocyte-derived DCs were stimulated with UV-inactivated gram-positive (Lactobacillus plantarumandBifidobacterium adolescentis) and gram-negative (Escherichia coliandVeillonella parvula) bacterial strains. Monocytes produced higher levels of interleukin 12p70 (IL-12p70) and tumor necrosis factor (TNF), as detected by an enzyme-linked immunosorbent assay, in response toL. plantarumthan in response toE. coliandV. parvula. In contrast, DCs secreted large amounts of IL-12p70, TNF, IL-6, and IL-10 in response toE. coliandV. parvulabut were practically unresponsive toL. plantarumandB. adolescentis. The lack of a response to the gram-positive strains correlated with lower surface expression of Toll-like receptor 2 (TLR2) on DCs than on monocytes. The surface expression of TLR4 on DCs was undetectable when it was analyzed by flow cytometry, but blocking this receptor decreased the TNF production in response toV. parvula, indicating that TLR4 is expressed at a low density on DCs. Gamma interferon increased the expression of TLR4 on DCs and also potentiated the cytokine response to the gram-negative strains. Our results indicate that when monocytes differentiate into DCs, their ability to respond to different commensal bacteria dramatically changes, and they become unresponsive to probiotic gram-positive bacteria. These results may have important implications for the abilities of different groups of commensal bacteria to regulate mucosal and systemic immunity.
Engulfment ofNeisseria gonorrhoeae: Revealing Distinct Processes of Bacterial Entry by Individual Carcinoembryonic Antigen-Related Cellular Adhesion Molecule Family Receptors
Authors: McCaw Shannon E. , Liao Edward H. , Gray-Owen Scott D. 
Published: April 2004

ABSTRACTIndividualNeisseria gonorrhoeaecolony opacity-associated (Opa) protein variants can bind up to four different carcinoembryonic antigen-related cellular adhesion molecule (CEACAM) receptors. Most human cells encountered by gonococci express a combination of CEACAM receptors, thereby complicating the elucidation of intracellular signaling pathways triggered by individual receptors. Here, we compare the process of bacterial engulfment by a panel of stably transfected HeLa epithelial cell lines expressing each CEACAM receptor in isolation. CEACAM1 and CEACAM3 each contain proteinaceous transmembrane and cytoplasmic domains; however, the processes of neisserial uptake mediated by these receptors differ with respect to their susceptibilities to both tyrosine kinase inhibitors and the actin microfilament-disrupting agent cytochalasin D. Neisserial uptake mediated by glycosylphosphatidylinositol (GPI)-anchored CEACAM5 and CEACAM6 was not significantly affected by any of a broad spectrum of inhibitors tested. However, cleavage of the GPI anchor by phosphatidylinositol-specific phospholipase C reduced bacterial uptake by HeLa cells expressing CEACAM5, consistent with a single zipper-like mechanism of uptake mediated by this receptor. Regardless of the CEACAM receptor expressed, internalized gonococci were effectively killed by a microtubule-dependent process that required acidification of the bacterium-containing phagosome. Given the phase-variable nature of neisserial Opa proteins, these results indicate that the mechanism of bacterial engulfment and the cellular response to gonococcal infection depend on both the receptor specificities of the neisserial Opa protein variants expressed and the spectrum of CEACAM receptors present on target cells, each of which determines the combination of receptors ultimately engaged.
Proteolytic Processing of theMycoplasma hyopneumoniaeCilium Adhesin
Authors: Djordjevic Steven P. , Cordwell Stuart J. , Djordjevic Michael A. , Wilton Jody , Minion F. Chris 
Published: April 2004

ABSTRACTMycoplasma hyopneumoniaeis an economically significant swine pathogen that colonizes the respiratory ciliated epithelial cells. Cilium adherence is mediated by P97, a surface protein containing a repeating element (R1) that is responsible for binding. Here, we show that the cilium adhesin is proteolytically processed on the surface. Proteomic analysis of strain J proteins identified cleavage products of 22, 28, 66, and 94 kDa. N-terminal sequencing showed that the 66- and 94-kDa proteins possessed identical N termini and that the 66-kDa variant was generated by cleavage of the 28-kDa product from the C terminus. The 22-kDa product represented the N-terminal 195 amino acids of the cilium adhesin preprotein, confirming that the hydrophobic leader signal sequence is not cleaved during translocation across the membrane. Comparative studies ofM. hyopneumoniaestrain 232 showed that the major cleavage products of the cilium adhesin are similar, although P22 and P28 appear to be processed further in strain 232. Immunoblotting studies using antisera raised against peptide sequences within P22 and P66/P94 indicate that processing is complex, with cleavage occurring at different frequencies within multiple sites, and is strain specific. Immunogold electron microscopy showed that fragments containing the cilium-binding site remained associated with the cell surface whereas cleavage products not containing the R1 element were located elsewhere. Not all secreted proteins undergo multiple cleavage, however, as evidenced by the analysis of the P102 gene product. The ability ofM. hyopneumoniaeto selectively cleave its secreted proteins provides this pathogen with a remarkable capacity to alter its surface architecture.
Importance of the Ornibactin and Pyochelin Siderophore Transport Systems in
Burkholderia cenocepacia
Lung Infections
Authors: Visser M. B. , Majumdar S. , Hani E. , Sokol P. A. 
Published: April 2004

ABSTRACT

Previously,
orbA
, the gene encoding the outer membrane receptor for ferric-ornibactin, was identified in
Burkholderia cenocepacia
K56-2, a strain which produces ornibactin, salicylic acid, and negligible amounts of pyochelin. A K56-2
orbA
mutant was less virulent than the parent strain in a rat agar bead infection model. In this study, an
orbA
mutant of
B. cenocepacia
Pc715j which produces pyochelin in addition to ornibactin and salicylic acid was constructed. The gene encoding the outer membrane receptor for ferric-pyochelin (
fptA
) was also identified. An
fptA
mutant was constructed in Pc715j and shown to be deficient in [
59
Fe]pyochelin uptake. A 75-kDa iron-regulated protein was identified in outer membrane preparations of Pc715j that was absent in outer membrane preparations of Pc715j
fpt
A::tp. Pc715j
fptA
::tp and Pc715j
orbA
::tp produced smaller amounts of their corresponding siderophores. Both Pc715j
orbA
::tp and Pc715j
fptA
::tp were able to grow in iron starvation conditions in vitro. In the agar bead model, the Pc715j
orbA
::tp mutant was cleared from the lung, indicating that the pyochelin uptake system does not compensate for the absence of a functional ornibactin system. Pc715j
fptA
::tp persisted in rat lung infections in numbers similar to those of the parent strain, indicating that the ferric-ornibactin uptake system could compensate for the defect in ferric-pyochelin uptake in vivo. These studies suggest that the ornibactin uptake system is the most important siderophore-mediated iron transport system in
B. cenocepacia
lung infections.
Partial Analysis of the Genomes of Two Nontypeable
Haemophilus influenzae
Otitis Media Isolates
Authors: Munson Robert S. , Harrison Alistair , Gillaspy Allison , Ray William C. , Carson Matt , Armbruster David , Gipson Jenny , Gipson Mandy , Johnson Linda , Lewis Lisa , Dyer David W. , Bakaletz Lauren O. 
Published: April 2004

ABSTRACT

In 1995, The Institute for Genomic Research completed the genomic sequence of a rough derivative of
Haemophilus influenzae
serotype d, strain KW20. This sequence, though extremely useful in understanding the basic biology of
H. influenzae
, has yet to provide significant insight into our understanding of disease caused by nontypeable
H. influenzae
(NTHI), because serotype d strains are not generally pathogens. In contrast, NTHI strains are frequently mucosal pathogens and are the primary pathogens of chronic otitis media as well as a significant cause of acute otitis media in children. Thus, it is of great importance to further understand their biology. We used a DNA-based microarray approach to identify genes present in a clinical isolate of NTHI that were absent from strain Rd. We also sequenced the genome of a second NTHI isolate from a child with chronic otitis media to threefold coverage and then used an array of bioinformatics tools to identify genes present in this NTHI strain but absent from strain Rd. These methods were complementary in approach and results. We identified, in both strains, homologues of
H. influenzae lav
, an autotransported protein of unknown function;
tnaA
, which encodes tryptophanase; as well as a homologue of
Pasteurella multocida tsaA
, which encodes an alkyl peroxidase that may play a role in protection against reactive oxygen species. We also identified a number of putative restriction-modification systems, bacteriophage genes and transposon-related genes. These data provide new insight that complements and extends our ongoing analysis of NTHI virulence determinants.
Cdc42 and the Actin-Related Protein/Neural Wiskott-Aldrich Syndrome Protein Network Mediate Cellular Invasion by
Cryptosporidium parvum
Authors: Chen Xian-Ming , Huang Bing Q. , Splinter Patrick L. , Orth James D. , Billadeau Daniel D. , McNiven Mark A. , LaRusso Nicholas F. 
Published: April 2004

ABSTRACT

Cryptosporidium parvum
invasion of epithelial cells involves host cell membrane alterations which require a remodeling of the host cell actin cytoskeleton. In addition, an actin plaque, possibly associated with the dense-band region, forms within the host cytoplasm at the host-parasite interface. Here we show that Cdc42 and RhoA, but not Rac1, members of the Rho family of GTPases, are recruited to the host-parasite interface in an in vitro model of human biliary cryptosporidiosis. Interestingly, activation of Cdc42, but not RhoA, was detected in the infected cells. Neural Wiskott-Aldrich syndrome protein (N-WASP) and p34-Arc, actin-regulating downstream effectors of Cdc42, were also recruited to the host-parasite interface. Whereas cellular expression of a constitutively active mutant of Cdc42 promoted
C. parvum
invasion, overexpression of a dominant negative mutant of Cdc42, or depletion of Cdc42 mRNA by short interfering RNA-mediated gene silencing, inhibited
C. parvum
invasion. Expression of the WA fragment of N-WASP to block associated actin polymerization also inhibited
C. parvum
invasion. Moreover, inhibition of host cell Cdc42 activation by dominant negative mutation inhibited
C. parvum
-associated actin remodeling, membrane protrusion, and dense-band formation. In contrast, treatment of cells with a Rho inhibitor, exoenzyme C3, or cellular overexpression of dominant negative mutants of RhoA and Rac1 had no effect on
C. parvum
invasion. These data suggest that
C. parvum
invasion of target epithelia results from the organism's ability to activate a host cell Cdc42 GTPase signaling pathway to induce host cell actin remodeling at the attachment site.
Porcine Choroid Plexus Epithelial Cells InduceStreptococcus suisBacteriostasis In Vitro
Authors: Adam Rüdiger A. , Tenenbaum Tobias , Valentin-Weigand Peter , Laryea Maurice , Schwahn Bernd , Angelow Susanne , Galla Hans-Joachim , Däubener Walter , Schroten Horst 
Published: April 2004

ABSTRACTThe involvement of the choroid plexus in host defense during bacterial meningitis is unclear. Aiming to elucidate possible antibacterial mechanisms, we stimulated primary porcine choroid plexus epithelial cells (pCPEC) with proinflammatory cytokines and challenged them with variousStreptococcus suisstrains. In the supernatant of gamma interferon (IFN-γ)-stimulated pCPEC, streptococcal growth was markedly suppressed. Costimulation with tumor necrosis factor alpha enhanced this bacteriostatic effect, while supplementation ofl-tryptophan completely eliminated it. We also demonstrate that an activation of indoleamine 2,3-dioxygenase in the pCPEC seems to be responsible for the IFN-γ-induced bacteriostasis. This supports the hypothesis of an active role of the choroid plexus in host defense against bacterial meningitis.
Osteology and myology of the cephalic region and pectoral girdle of Schilbe mystus and comparison with other schilbids, with comments on the monophyly and phylogenetic relationships of the Schilbidae (Teleostei: Siluriformes)
Authors: Diogo Rui , Chardon Michel , Vandewalle Pierre 
Published: April 2004

Abstract
The cephalic and pectoral girdle structures of Schilbe mystus are described and compared with those of other schilbids, as well as several other non-schilbid catfishes, as the foundation for a discussion on the monophyly and the phylogenetic relationships of the Schilbidae. Our observations and comparisons suggest that the family Schilbidae is a monophyletic group, defined, at least, by three autapomorphies, namely: 1) the adductor mandibulae A2 is lateral to the A1-Ost; 2) the posterior margin of the horizontal portion of Meckel's cartilage is situated further beyond the coronoid process; 3) the adductor mandibulae Aω is visible in a lateral view of the cephalic region. With respect to the phylogenetic relationships of the Schilbidae, our observations and comparisons support a close relationship between this family and the Pangasiidae.