bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution and movement ofCaenorhabditis eleganson a thermal gradient
Authors: Yamada Yohko , Ohshima Yasumi 
Published: June 2003

SUMMARYTo analyze thermal responses of Caenorhabditis elegans in detail,distribution of a worm population and movement of individual worms were examined on a linear, reproducible and broad temperature gradient. Assay methods were improved compared with those reported previously to ensure good motility and dispersion of worms. Well-fed, wild-type worms distributed over a wide temperature range of up to 10°C, and, within this range, worms migrated in both directions of the gradient at similar frequencies without any specific response to the growth temperature in most cases. By contrast, worms migrated down the gradient if put in a region warmer than the warm boundary of distribution. The distribution range changed depending on the growth temperature and starvation, but active avoidance of a starvation temperature was not detected. These findings contradict previous hypotheses of taxis or migration to the growth temperature in association with food and instead indicate avoidance of a warm temperature. Our results favor a model for thermal response of C. elegans that postulates a single drive based on warm sensation rather than downward and upward drives in the physiological temperature range. Mutants in ttx-3, tax-2, tax-4 or egl-4genes showed abnormal thermal responses, suggesting that these genes are involved in warm avoidance. Laser ablation and gene expression studies suggest that AFD neurons are not important, and tax-4 expression in neurons other than AFD is required, for warm avoidance.
Chondrocyte apoptosis induced by collagen degradation: Inhibition by caspase inhibitors and IGF‐1
Authors: Lo Marvin Y. , Kim Hubert T. 
Published: June 2003

AbstractThe main objective of this study was to test the effectiveness of candidate apoptosis inhibitors in limiting chondrocyte apoptosis induced by collagen degradation. Primary human chondrocytes were isolated from normal articular cartilage and grown in monolayer culture. Collagenase was added to the cells in the presence and absence of caspase inhibitors and insulin like growth factor (IGF)‐1. The amount of chondrocyte apoptosis was measured using an enzyme linked immunosorbent assay for nucleosomes, a specific and quantitative measure of apoptosis. Chondrocyte apoptosis was induced by collagenase treatment in both a time and dose dependent manner. The non‐selective caspase inhibitor Z‐VAD, the caspase‐3 selective inhibitor Z‐DEVD, and the growth factor insulin like growth factor (IGF)‐1 inhibited chondrocyte apoptosis induced by collagenase treatment. The caspase‐1 selective inhibitor Z‐YVAD also blocked chondrocyte apoptosis under these conditions, in contrast to previous studies where caspase‐1 inhibition failed to block apoptosis induced by agents such as the topoisomerase inhibitor camptothecin. These data demonstrate that the response of chondrocytes to caspase inhibition may be dependent upon the specific stimulus that initiates apoptosis. Furthermore, these findings suggest that multiple pathways involving both the initiation and execution of programmed cell death are potential targets for chondrocyte apoptosis inhibition therapy. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Teichoic Acids Are Not Required forStreptococcus pneumoniaeandStaphylococcus aureusCell Walls To Trigger the Release of Tumor Necrosis Factor by Peripheral Blood Monocytes
Authors: Majcherczyk P. A. , Rubli E. , Heumann D. , Glauser M. P. , Moreillon P. 
Published: June 2003

ABSTRACTIn gram-negative bacteria, the outer membrane lipopolysaccharide is the main component triggering cytokine release from peripheral blood mononuclear cells (PBMCs). In gram-positive bacteria, purified walls also induce cytokine release, but stimulation requires 100 times more material. Gram-positive walls are complex megamolecules reassembling distinct structures. Only some of them might be inflammatory, whereas others are not. Teichoic acids (TA) are an important portion (≥50%) of gram-positive walls. TA directly interact with C3b of complement and the cellular receptor for platelet-activating factor. However, their contribution to wall-induced cytokine-release by PBMCs has not been studied in much detail. In contrast, their membrane-bound lipoteichoic acids (LTA) counterparts were shown to trigger inflammation and synergize with peptidoglycan (PGN) for releasing nitric oxide (NO). This raised the question as to whether TA are also inflammatory. We determined the release of tumor necrosis factor (TNF) by PBMCs exposed to a variety of TA-rich and TA-free wall fragments fromStreptocccus pneumoniaeandStaphylococcus aureus. TA-rich walls from both organisms induced measurable TNF release at concentrations of 1 μg/ml. Removal of wall-attached TA did not alter this activity. Moreover, purified pneumococcal and staphylococcal TA did not trigger TNF release at concentrations as high as ≥100 μg/ml. In contrast, purified LTA triggered TNF release at 1 μg/ml. PGN-stem peptide oligomers lacking TA or amino-sugars were highly active and triggered TNF release at concentrations as low as 0.01 μg/ml (P. A. Majcherczyk, H. Langen, et al., J. Biol. Chem. 274:12537-12543,1999). Thus, although TA is an important part of gram-positive walls, it did not participate to the TNF-releasing activity of PGN.
Control of the Oxidative Burst of Human Neutrophils by Staphylococcal Leukotoxins
Authors: Colin Didier A. , Monteil Henri 
Published: June 2003

ABSTRACT

The ability of staphylococcal two-component leukotoxins to induce an oxidative burst and/or to prime human polymorphonuclear cells (PMNs) was studied by using spectrofluorometry or flow cytometry. At sublytic concentrations, the HlgA-HlgB, HlgA-LukF-PV, LukS-PV-LukF-PV, and HlgC-LukF-PV combinations of leukotoxins, but not the LukS-PV-HlgB and HlgC-HlgB combinations, were able to induce H
2
O
2
production similar to the H
2
O
2
production induced by 1 μM
N
-formyl-Met-Leu-Phe (fMLP). In addition, when added at sublytic concentrations, all of the leukotoxin combinations primed PMNs for H
2
O
2
production induced by fMLP. Leukotoxin activation was dependent on the presence of Ca
2+
and was inhibited by wortmannin, an inhibitor of phosphatidylinositol 3-kinase, but not by
N
-methyl-
l
-arginine, an inhibitor of NO generation, which eliminates the possibility that NO plays a role in the action of leukotoxins. At higher concentrations, all leukotoxins inhibited H
2
O
2
production by PMNs activated by fMLP, phorbol 12-myristate 13-acetate (PMA), or the leukotoxins themselves. This inhibition was not related to the pore formation induced by leukotoxins. Intracellular release of H
2
O
2
induced by fMLP and PMA was not primed by leukotoxins but was inhibited. It seems that leukotoxin inhibition of H
2
O
2
release is independent of pore formation but secondary to an intracellular event, as yet unknown, triggered by leukotoxins.
Salmonella enterica
Serovar Typhimurium Expressing a Chromosomally Integrated Copy of the
Bacillus anthracis
Protective Antigen Gene Protects Mice against an Anthrax Spore Challenge
Authors: Garmory Helen S. , Titball Richard W. , Griffin Kate F. , Hahn Ulrike , Böhm Reinhard , Beyer Wolfgang 
Published: June 2003

ABSTRACT

Protective immunity against infection with
Bacillus anthracis
is almost entirely based on a response to the protective antigen (PA), the binding moiety for the two other toxin components. We cloned the PA gene into an auxotrophic mutant of
Salmonella enterica
serovar Typhimurium as a fusion with the signal sequence of the hemolysin (Hly) A gene of
Escherichia coli
to allow the export of PA via the Hly export system. To stabilize the export cassette, it was also integrated into the chromosome of the live
Salmonella
carrier. When
S
.
enterica
serovar Typhimurium with the chromosomally integrated PA gene was given intravenously to A/J mice, they developed high levels of antibody to PA. These mice were protected against intraperitoneal challenge with 100 or 1,000 50% lethal doses of
B
.
anthracis
strain STI. This work contributes to the development of a
Salmonella
-based orally delivered anthrax vaccine.
The Delta Subunit of RNA Polymerase Is Required for Virulence of
Streptococcus agalactiae
Authors: Jones Amanda L. , Needham Rachel H. V. , Rubens Craig E. 
Published: June 2003

ABSTRACT

Group B streptococci (GBS) remain the most significant bacterial pathogen causing neonatal sepsis, pneumonia, and meningitis in the United States despite the chemoprophylaxis strategies for preventing infection recommended by the Centers for Disease Control and Prevention. Using signature-tagged transposon mutagenesis to screen for novel virulence factors, we identified the
rpoE
gene as essential for development of sepsis in a neonatal rat model of GBS infection. An
rpoE
allelic replacement mutant displayed attenuated virulence in the sepsis model of infection identical to that of the transposon mutant, confirming linkage of the phenotype to the mutation in
rpoE
. The
rpoE
mutants also displayed increased sensitivity to killing in whole-blood bactericidal assays, which may explain the attenuated virulence. The mutants were otherwise phenotypically identical to the wild-type strain, including growth rate in plasma, indicating that a growth defect is not responsible for the attenuated virulence.
rpoE
is found only in gram-positive bacterial species and encodes the delta peptide, a subunit of RNA polymerase. Previous in vitro studies in other bacteria suggest that the delta peptide plays a role in maintaining transcriptional fidelity by blocking RNA polymerase binding at all but the strongest promoters, thereby inhibiting initiation of transcription. Despite the availability of
rpoE
mutants for several gram-positive bacterial species, a role for the peptide in vivo has not been defined, though it has been postulated that the delta peptide may be important for long-term survival in vitro or during growth phase transitions. Our data represent the first report of a phenotype relevant to virulence for
rpoE
mutants.
Differential Effect of p47phoxand gp91phoxDeficiency on the Course of Pneumococcal Meningitis
Authors: Schaper Manuela , Leib Stephen L. , Meli Damian N. , Brandes Ralf P. , Täuber Martin G. , Christen Stephan 
Published: June 2003

ABSTRACTBacterial meningitis is a severe inflammatory disease of the central nervous system and is characterized by massive infiltration of granulocytes into the cerebrospinal fluid (CSF). To assess the role of NADPH oxidase-derived reactive oxygen species (ROS) in pneumococcal meningitis, mice deficient in either the gp91 subunit (essential for functioning of the phagocyte enzyme) or the p47 subunit (essential for functioning of homologous enzymes in nonphagocytic cells) were intracisternally infected with liveStreptococcus pneumoniae, and defined disease parameters were measured during the acute stage of infection. While none of the parameters measured (including CSF bacterial titers) were significantly different in gp91−/−and wild-type mice, the infection in p47−/−mice was associated with significantly increased inflammation of the subarachnoid and ventricular space, disruption of the blood-brain barrier, and the presence of interleukin-1β, tumor necrosis factor alpha, and matrix metalloproteinase 9 in the cortex. These changes were associated with ∼10-fold-higher CSF bacterial titers in p47−/−mice than in wild-type mice (P< 0.001). In contrast to infection with live bacteria, the inflammatory response, including CSF leukocytosis, was significantly attenuated in p47−/−mice (but not gp91−/−mice) challenged with a fixed number of heat-inactivated pneumococci. Impairment of the host defense appeared to be responsible for the higher bacterial titers in p47−/−mice. Therefore, these results indicate that ROS generated by a gp91-independent NADPH oxidase(s) are important for establishing an adequate inflammatory response to pneumococcal CSF infection.
Nuclear Factor κB Protects against Host Cell Apoptosis during
Rickettsia rickettsii
Infection by Inhibiting Activation of Apical and Effector Caspases and Maintaining Mitochondrial Integrity
Authors: Joshi Suresh G. , Francis Charles W. , Silverman David J. , Sahni Sanjeev K. 
Published: June 2003

ABSTRACT

Apoptotic host cell death is a critical determinant in the progression of microbial infections and outcome of resultant diseases. The potentially fatal human infection caused by
Rickettsia rickettsii,
the etiologic agent of Rocky Mountain spotted fever, involves the vascular endothelium of various organ systems of the host. Earlier studies have shown that survival of endothelial cells (EC) during this infection depends on their ability to activate the transcription factor nuclear factor κB (NF-κB). Here, we investigated the involvement of caspase cascades and associated signaling pathways in regulation of host cell apoptosis by NF-κB. Infection of cultured human EC with
R. rickettsii
with simultaneous inhibition of NF-κB induced the activation of apical caspases 8 and 9 and also the executioner enzyme, caspase 3, whereas infection alone had no significant effect. Inhibition of either caspase-8 or caspase-9 with specific cell-permeating peptide inhibitors caused a significant decline in the extent of apoptosis, confirming their importance. The peak caspase-3 activity occurred at 12 h postinfection and led to cleavage of poly(ADP-ribose) polymerase, followed by DNA fragmentation and apoptosis. However, the activities of caspases 6 and 7, other important downstream executioners, remained unchanged. Caspase-9 activation was mediated through the mitochondrial pathway of apoptosis, as evidenced by loss of transmembrane potential and cytoplasmic release of cytochrome
c.
These findings suggest that activation of NF-κB is required for maintenance of mitochondrial integrity of host cells and protection against infection-induced apoptotic death by preventing activation of caspase-9- and caspase-8-mediated pathways. Targeted inhibition of NF-κB may therefore be exploited to enhance the clearance of infections with
R. rickettsii
and other intracellular pathogens with similar survival strategies.
Virulence Factors and Clonal Relationships among
Escherichia coli
Strains Isolated from Broiler Chickens with Cellulitis
Authors: de Brito Benito Guimarães , Gaziri Luiz Carlos J. , Vidotto Marilda C. 
Published: June 2003

ABSTRACT

In this study, we compared
Escherichia coli
isolates from chickens with avian cellulitis with those from feces of healthy chickens. Cellulitis-derived strains presented phenotypic and genotypic characteristics of greater virulence than did the fecal isolates. Phylogenetic analysis by repetitive extragenic palindromic-PCR showed that, in agreement with their virulence characteristics, the cellulitis isolates form two clonal groups distinct from the fecal isolates.
Transforming Growth Factor α Binds to
Trypanosoma cruzi
Amastigotes To Induce Signaling and Cellular Proliferation
Authors: Alexander A. Deloris , Villalta Fernando , Lima Maria F. 
Published: June 2003

ABSTRACT

Macrophages secrete transforming growth factor α (TGF-α) to trigger proliferation of cancer cells. Here, we report a new role for TGF-α in modulating the direct cellular proliferation of a parasitic protozoan,
Trypanosoma cruzi
. Amastigotes present two classes of receptors for TGF-α with different binding affinities.
125
I-TGF-α binding was competed by an excess of cold epidermal growth factor and TGF-α but not by an irrelevant molecule. Upon binding of TGF-α to amastigotes, the ligand is internalized, inducing trypanosome tyrosine phosphorylation of 90- and 87-kDa proteins and increasing DNA synthesis and proliferation of amastigotes. Furthermore, exposure of macrophages to TGF-α induced increased amastigote proliferation. These results describe a novel mechanism used by amastigotes to regulate their proliferation mediated by a TGF-α-dependent signal transduction pathway.
Modification of
Pseudomonas aeruginosa
Interactions with Corneal Epithelial Cells by Human Tear Fluid
Authors: Fleiszig Suzanne M. J. , Kwong Mary S. F. , Evans David J. 
Published: June 2003

ABSTRACT

Both cytotoxic and invasive strains of
Pseudomonas aeruginosa
can damage corneal epithelial cells in vitro, but neither can infect healthy corneas in vivo. We tested the hypothesis that whole human tear fluid can protect corneal epithelia against
P. aeruginosa
virulence mechanisms. Cultured corneal epithelial cells were inoculated with 10
6
CFU of one of 10 strains of
P. aeruginosa
(five cytotoxic, five invasive)/ml with or without reflex tear fluid collected from the conjunctival sacs of human volunteers. Cytotoxicity was assessed by observation of trypan blue staining and measurement of lactate dehydrogenase release; invasion was quantified by using gentamicin survival assays. Tear fluid retarded growth of only 50% of the
P. aeruginosa
strains (three of five invasive strains, two of five cytotoxic strains) yet protected corneal cells against invasion by or cytotoxicity of 9 of 10 strains. The only strain resistant to the tear cytoprotective effects was susceptible to tear bacteriostatic activity. Dilution of tear fluid threefold significantly reduced cytoprotection, while bacteriostatic activity prevailed with dilutions beyond 100-fold. Sulfacetamide (1 mg/ml) with bacteriostatic activity matching that of tear fluid was less cytoprotective than tear fluid (80% protection with tear fluid, 48% with sulfacetamide). Video microscopy revealed bacterial chain formation in both tear fluid and sulfacetamide, but tear fluid also blocked bacterial swimming motility. After prolonged tear contact, bacteria regained normal growth rates, swimming motility, and cytotoxic activity, suggesting a breakdown of protective tear factors. Boiled tear fluid lost bacteriostatic activity and effects on bacterial motility but retained cytoprotective function. These results suggest that human tear fluid can protect corneal epithelial cells against
P. aeruginosa
virulence mechanisms in a manner not dependent upon bacteriostatic activity or effects on bacterial motility. Whether overlapping tear film components are involved in these defense functions is to be determined.
Development of DNA Vaccines against Hemolytic-Uremic Syndrome in a Murine Model
Authors: Capozzo Alejandra V. E. , Creydt Virginia Pistone , Dran Graciela , Fernández Gabriela , Gómez Sonia , Bentancor Leticia V. , Rubel Carolina , Ibarra Cristina , Isturiz Martín , Palermo Marina S. 
Published: June 2003

ABSTRACTShiga toxin type 2 (Stx2) produced byEscherichia coliO:157H7 can cause hemolytic-uremic syndrome in children, a disease for which there is neither a vaccine nor an effective treatment. This toxin consists of an enzymatically active A subunit and a pentameric B subunit responsible for the toxin binding to host cells, and also found to be immunogenic in rabbits. In this study we developed eukaryotic plasmids expressing the B subunit gene of Stx2 (pStx2B) and the B subunit plus the gene coding for the A subunit with an active-site deletion (pStx2ΔA). Transfection of eukaryotic cells with these plasmids produced proteins of the expected molecular weight which reacted with specific monoclonal antibodies. Newborn and adult BALB/c mice immunized with two intramuscular injections of each plasmid, either alone or together with the same vector expressing the granulocyte and monocyte colony-stimulating factor (pGM-CSF), elicited a specific Th1-biased humoral response. The effect of pGM-CSF as an adjuvant plasmid was particularly notable in newborn mice and in pStx2B-vaccinated adult mice. Stx2-neutralizing activity, evaluated in vitro on VERO cell monolayers, correlated with in vivo protection. This is the first report using plasmids to induce a neutralizing humoral immune response against the Stx2.
Immune Responses Induced by theLeishmania(Leishmania)donovaniA2 Antigen, but Not by the LACK Antigen, Are Protective against ExperimentalLeishmania(Leishmania)amazonensisInfection
Authors: Coelho Eduardo Antonio Ferraz , Tavares Carlos Alberto Pereira , Carvalho Fernando Aécio Amorim , Chaves Karina Figueiredo , Teixeira Kadima Nayara , Rodrigues Rafaela Chitarra , Charest Hugues , Matlashewski Greg , Gazzinelli Ricardo Tostes , Fernandes Ana Paula 
Published: June 2003

ABSTRACTLeishmania amazonensisis one of the major etiologic agents of a broad spectrum of clinical forms of leishmaniasis and has a wide geographical distribution in the Americas, which overlaps with the areas of transmission of many otherLeishmaniaspecies. The LACK and A2 antigens are shared by variousLeishmaniaspecies. A2 was previously shown to induce a potent Th1 immune response and protection againstL. donovaniinfection in BALB/c mice. LACK is effective againstL. majorinfection, but no significant protection againstL. donovaniinfection was observed, in spite of the induction of a potent Th1 immune response. In an attempt to select candidate antigens for an American leishmaniasis vaccine, we investigated the protective effect of these recombinant antigens (rLACK and rA2) and recombinant interleukin-12 (rIL-12) againstL. amazonensisinfection in BALB/c mice. As expected, immunization with either rA2-rIL-12 or rLACK-rIL-12 induced a robust Th1 response prior to infection. However, only the BALB/c mice immunized with rA2-rIL-12 were protected against infection. Sustained gamma interferon (IFN-γ) production, high levels of anti-A2 antibodies, and low levels of parasite-specific antibodies were detected in these mice after infection. In contrast, mice immunized with rLACK-rIL-12 displayed decreased levels of IFN-γ and high levels of both anti-LACK and parasite-specific antibodies. Curiously, the association between rA2 and rLACK antigens in the same vaccine completely inhibited the rA2-specific IFN-γ and humoral responses and, consequently, the protective effect of the rA2 antigen againstL. amazonensisinfection. We concluded that A2, but not LACK, fits the requirements for a safe vaccine against American leishmaniasis.
Inflammatory Cytokine Response to
Vibrio vulnificus
Elicited by Peripheral Blood Mononuclear Cells from Chronic Alcohol Users Is Associated with Biomarkers of Cellular Oxidative Stress
Authors: Powell Jan L. , Strauss Kathy A. , Wiley Cynthia , Zhan Min , Morris J. Glenn 
Published: June 2003

ABSTRACT

Vibrio vulnificus
is the leading cause of death in the United States associated with the consumption of raw seafood, particularly oysters. In epidemiological studies, primary septicemia and inflammation-mediated septic shock caused by
V
.
vulnificus
is strongly associated with liver disease, often in the context of chronic alcohol abuse. The present study was undertaken to determine whether clinical biomarkers of liver function or cellular oxidative stress are associated with peripheral blood mononuclear cell inflammatory cytokine responses to
V
.
vulnificus
. Levels of interleukin-1β (IL-1β), IL-6, IL-8, and tumor necrosis factor alpha elicited in response to
V
.
vulnificus
and measured in cell supernatants were not associated with the liver biomarkers aspartate aminotransferase (AST) or alanine aminotransferase (ALT) or the AST/ALT ratio. In contrast, reduced glutathione (GSH) levels were associated with the release of all four cytokines (IL-1β [
R
2
= 0.382;
P
= 0.006], IL-6 [
R
2
= 0.393;
P
= 0.005], IL-8 [
R
2
= 0.487;
P
= 0.001], and TNF-α [
R
2
= 0.292;
P
= 0.021]). Those individuals with below-normal GSH levels produced significantly less proinflammatory cytokines in response to
V
.
vulnificus
. We hypothesize that persons with markers for cellular oxidative stress have increased susceptibility to
V
.
vulnificus
septicemia.