bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of macrofaunal assemblages and environmental heterogeneity on microphytobenthic production in experimental systems
Authors: Dyson Kirstie E , Bulling Mark T , Solan Martin , Hernandez-Milian Gema , Raffaelli David G , White Piran C.L , Paterson David M
Published: August 2007

Despite the complexity of natural systems, heterogeneity caused by the fragmentation of habitats has seldom been considered when investigating ecosystem processes. Empirical approaches that have included the influence of heterogeneity tend to be biased towards terrestrial habitats; yet marine systems offer opportunities by virtue of their relative ease of manipulation, rapid response times and the well-understood effects of macrofauna on sediment processes. Here, the influence of heterogeneity on microphytobenthic production in synthetic estuarine assemblages is examined. Heterogeneity was created by enriching patches of sediment with detrital algae (Enteromorpha intestinalis) to provide a source of allochthonous organic matter. A gradient of species density for four numerically dominant intertidal macrofauna (Hediste diversicolor,Hydrobia ulvae,Corophium volutator,Macoma balthica) was constructed, and microphytobenthic biomass at the sediment surface was measured. Statistical analysis using generalized least squares regression indicated that heterogeneity within our system was a significant driving factor that interacted with macrofaunal density and species identity. Microphytobenthic biomass was highest in enriched patches, suggesting that nutrients were obtained locally from the sediment–water interface and not from the water column. Our findings demonstrate that organic enrichment can cause the development of heterogeneity which influences infaunal bioturbation and consequent nutrient generation, a driver of microphytobenthic production.
Accumulation boundaries: codimension-two accumulation of accumulations in phase diagrams of semiconductor lasers, electric circuits, atmospheric and chemical oscillators
Authors: Bonatto Cristian , Gallas Jason Alfredo Carlson
Published: August 2007

We report high-resolution phase diagrams for several familiar dynamical systems described by sets of ordinary differential equations: semiconductor lasers; electric circuits; Lorenz-84 low-order atmospheric circulation model; and Rössler and chemical oscillators. All these systems contain chaotic phases with highly complicated and interesting
accumulation boundaries
, curves where networks of stable islands of regular oscillations with ever-increasing periodicities accumulate systematically. The experimental exploration of such codimension-two boundaries characterized by the presence of infinite
accumulation of accumulations
is feasible with existing technology for some of these systems.
Topological characterization of deterministic chaos: enforcing orientation preservation
Authors: Lefranc Marc , Morant Pierre-Emmanuel , Nizette Michel
Published: August 2007

The determinism principle, which states that dynamical state completely determines future time evolution, is a keystone of nonlinear dynamics and chaos theory. Since it precludes that two state space trajectories intersect, it is a core ingredient of a topological analysis of chaos based on a knot-theoretic characterization of unstable periodic orbits embedded in a strange attractor. However, knot theory can be applied only to three-dimensional systems. Still, determinism applies in any dimension. We propose an alternative framework in which this principle is enforced by constructing an orientation-preserving dynamics on triangulated surfaces and find that in three dimensions our approach numerically predicts the correct topological entropies for periodic orbits of the horseshoe map.
Low-dimensional chaos and wave turbulence in plasmas
Authors: Batista A.M , Caldas I.L , Lopes S.R , Viana R.L
Published: August 2007

Abstract

We investigated drift-wave turbulence in the plasma edge of a small tokamak by considering solutions of the Hasegawa–Mima equation involving three interacting modes in Fourier space. The resulting low-dimensional dynamics presented periodic as well as chaotic evolution of the Fourier-mode amplitudes, and we performed the control of chaotic behaviour through the application of a fourth resonant wave of small amplitude.
Recurrence plots for dynamical analysis of non-invasive mechanical ventilation
Authors: Letellier C , Rabarimanantsoa H , Achour L , Cuvelier A , Muir J.-F
Published: August 2007

Quantifiers were introduced to convert recurrence plots into a statistical analysis of dynamical properties. It is shown that the Shannon entropy, if properly computed, increases as the chaotic regime is developed as expected. Recurrence plots and a new estimator for the Shannon entropy are then used to identify asynchronisms in non-invasive mechanical ventilation. It is thus shown that the phase coherence—easily identified using a Shannon entropy—is relevant in the quality of the mechanical ventilation. In particular, some patients with chronic respiratory diseases or healthy subjects can have a high rate of asynchronisms but a regular breathing rhythm.
Searching chaos and coherent structures in the atmospheric turbulence above the Amazon forest
Authors: Campanharo A.S.L.O , Ramos F.M , Macau E.E.N , Rosa R.R , Bolzan M.J.A , Sá L.D.A
Published: August 2007

In this work, the possible chaotic nature of the atmospheric turbulence above a densely forested area in the Amazon region is investigated. To this end, we use high-resolution temperature data obtained during a micrometeorological measurement campaign in the Brazilian Amazonia. Estimates of the correlation dimension (
D
2
=3.50±0.05) and of the largest Lyapunov exponent (
λ
1
=0.050±0.002) suggest the existence of chaos in the atmospheric boundary layer. Our findings indicate that this low-dimensional chaotic dynamics is associated with the presence of the coherent structures within the boundary layer right above the canopy top and not with the atmospheric turbulence
per se
, as previously claimed.
A Bayesian Model for Ranking Hazardous Road Sites
Authors: Brijs Tom , Karlis Dimitris , Van den Bossche Filip , Wets Geert
Published: August 2007

Road safety has recently become a major concern in most modern societies. The identification of sites that are more dangerous than others (black spots) can help in better scheduling road safety policies. This paper proposes a methodology for ranking sites according to their level of hazard. The model is innovative in at least two respects. Firstly, it makes use of all relevant information per accident location, including the total number of accidents and the number of fatalities, as well as the number of slight and serious injuries. Secondly, the model includes the use of a cost function to rank the sites with respect to their total expected cost to society. Bayesian estimation for the model via a Markov chain Monte Carlo approach is proposed. Accident data from 519 intersections in Leuven (Belgium) are used to illustrate the methodology proposed. Furthermore, different cost functions are used to show the effect of the proposed method on the use of different costs per type of injury.
Combining Census and Registration Data to Estimate Detailed Elderly Migration Flows in England and Wales
Authors: Raymer James , Abel Guy , Smith Peter W. F.
Published: August 2007

A log-linear model is developed to estimate detailed elderly migration flows by combining data from the 2001 UK census and National Health Services patient register. After showing that the census and National Health Service migration flows can be reasonably combined, elderly migration flows between groupings of local authority districts by age, sex and health status for the 2000–2001 and 2003–2004 periods are estimated and then analysed to show how the patterns have changed. By combining registration data with census data, we can provide recent estimates of detailed elderly migration flows, which can be used for improvements in social planning or policy.
Romanticism and Forgery
Authors: Groom Nick
Published: August 2007

Several literary forgers emerged in the later eighteenth century: notably James Macpherson (Ossian), Thomas Chatterton (Thomas Rowley) and William Henry Ireland (the Shakespeare forger). These cases of literary forgery were highly controversial at the time, and had a lasting impact on the Romantic movement, particularly in the understanding of authenticity, inspiration and the figure of the poet, although by this time plagiarism, hoaxing and impersonation had superseded forgery – most clearly in the cases of Princess Caraboo, Joanna Southcott and the seduction of the Maid of Buttermere. Serious critical attention to both forgers and impostors has dramatically increased in recent years, with feminist, post‐colonial and psychoanalytic readings. Cases of writers of ‘fakelit’ also have serious implications for criticism today.
Cellular Effects of Reversed Amidines on
Trypanosoma cruzi
Authors: Silva C. F. , Meuser M. B. , De Souza E. M. , Meirelles M. N. L. , Stephens C. E. , Som P. , Boykin D. W. , Soeiro M. N. C.
Published: August 2007

Aromatic diamidines represent a class of DNA minor groove-binding ligands that exhibit high levels of antiparasitic activity. Since the chemotherapy for Chagas' disease is still an unsolved problem and previous reports on diamidines and related analogues show that they have high levels of activity against
Trypanosoma cruzi
infection both in vitro and in vivo, our present aim was to evaluate the cellular effects in vitro of three reversed amidines (DB889, DB702, and DB786) and one diguanidine (DB711) against both amastigotes and bloodstream trypomastigotes of
T. cruzi
, the etiological agent of Chagas ' disease. Our data show that the reversed amidines have higher levels of activity than the diguanidine, with the order of trypanocidal activities being as follows: DB889 > DB702 > DB786 > DB711. Transmission electron microscopy analysis showed that the reversed amidines induced many alterations in the nuclear morphology, swelling of the endoplasmic reticulum and Golgi structures, and consistent damage in the mitochondria and kinetoplasts of the parasites. Interestingly, in trypomastigotes treated with the reversed amidine DB889, multiple axoneme structures (flagellar microtubules) were noted. Flow cytometry analysis confirmed that the treated parasites presented an important loss of the mitochondrial membrane potential, as revealed by a decrease in rhodamine 123 fluorescence. Our results show that the reversed amidines have promising activities against the relevant mammalian forms of
T. cruzi
and display high trypanocidal effects at very low doses. This is especially the case for DB889, which merits further in vivo evaluation.
Galanin Message-Associated Peptide Suppresses Growth and the Budded-to-Hyphal-Form Transition ofCandida albicans
Authors: Rauch Isabella , Lundström Linda , Hell Markus , Sperl Wolfgang , Kofler Barbara
Published: August 2007

The expression of the mRNA encoding galanin message-associated peptide (GMAP) in human keratinocytes is upregulated by lipopolysaccharides and exposure toCandida albicans. GMAP has growth-inhibiting activity againstC. albicansand inhibits the budded-to-hyphal-form transition, establishing GMAP as a possible new component of the innate immune system.
The Antifungal Polyketide Ambruticin Targets the HOG Pathway
Authors: Vetcher Leandro , Menzella Hugo G. , Kudo Toshiaki , Motoyama Takayuki , Katz Leonard
Published: August 2007

The polyketide ambruticin is an attractive candidate for drug development as an antifungal agent, but its mechanism of action has not yet been elucidated. Here we present evidence that ambruticin exerts its effect by targeting HOG, the osmotic stress control pathway, through Hik1, a group III histidine kinase.
Genetic Characteristics and Clonal Dissemination of β-Lactamase-Negative Ampicillin-ResistantHaemophilus influenzaeStrains Isolated from the Upper Respiratory Tract of Patients in Japan
Authors: Hotomi Muneki , Fujihara Keiji , Billal Dewan S. , Suzuki Kenji , Nishimura Tadao , Baba Shunkichi , Yamanaka Noboru
Published: August 2007

We evaluated the recent prevalence of antimicrobial-resistantHaemophilus influenzaeisolated from the upper respiratory tracts (URT) of patients in Japan. Mutations in theftsIgene, which encodes penicillin binding protein 3 (PBP3), and the clonal dissemination of the resistant strains were also investigated. A total of 264H. influenzaeisolates were collected from patients with URT infections. According to the criteria of the Clinical and Laboratory Standards Institute for the susceptibility ofH. influenzaeto ampicillin (AMP), the isolates were distributed as follows: 161 (61.0%) susceptible strains (MIC ≤ 1 μg/ml), 37 (14.0%) intermediately resistant strains (MIC = 2 μg/ml), and 66 (25.0%) resistant strains (MIC ≥ 4 μg/ml). According to PCR-based genotyping, 172 (65.1%) of the isolates had mutations in theftsIgene and were negative for the β-lactamase (bla) gene. These 172 isolates were thus defined as genetically β-lactamase-negative ampicillin-resistant (gBLNAR) strains. TheftsImutant group included 98 (37.1%) strains with group I/II mutations in the variable mutated region (group I/II gBLNAR) and 74 (28.0%) strains with group III mutations in the highly mutated region (group III gBLNAR). Eighty-seven (33.0%) of the isolates were genetically β-lactamase-negative ampicillin-susceptible (gBLNAS) strains. The group III gBLNAR strains showed resistance to β-lactams. Only five strains (1.9%) were positive for ablagene encoding TEM-type β-lactamase. The three clusters consisting of 16 strains found among the 61 BLNAR strains (MIC ≥ 4 μg/ml and without theblagene) showed identical or closely related DNA restriction fragment patterns. Those isolates were frequently identified among strains with a MIC to AMP of 16 μg/ml. The current study demonstrates the apparent dissemination and spread of a resistant clone ofH. influenzaeamong medical centers in Japan. The gBLNAR strains show a remarkable prevalence amongH. influenzaeisolates, with the prevalence increasing with time. This fact should be taken into account when treating URT infections.
2,N
6
-Disubstituted Adenosine Analogs with Antitrypanosomal and Antimalarial Activities
Authors: Rodenko Boris , van der Burg Alida M. , Wanner Martin J. , Kaiser Marcel , Brun Reto , Gould Matthew , de Koning Harry P. , Koomen Gerrit-Jan
Published: August 2007

A library of 2,N
6
-disubstituted adenosine analogs was synthesized and the analogs were tested for their antiprotozoal activities. It was found that 2-methoxy and 2-histamino and
N
6
-
m
-iodobenzyl substitutions generally produced analogs with low levels of antiprotozoal activity. The best antiplasmodial activity was achieved with large aromatic substitutions, such as
N
6
-2,2-diphenylethyl and naphthylmethyl, which could indicate a mechanism of action through aromatic stacking with heme in the digestive vacuole of
Plasmodium
spp. The activities against
Trypanosoma cruzi
trypomastigotes and
Leishmania donovani
amastigotes were generally low; but several analogs, particularly those with cyclopentylamino substitutions, displayed potent activities against
Trypanosoma brucei rhodesiense
and
T. b. brucei
bloodstream forms in vitro. The most active were 2-cyclopentylamino-
N
6
-cyclopentyladenosine (compound NA42) and 2-cyclopentylamino-
N
6
-cyclopentyladenine (compound NA134), with the nucleobase an order of magnitude more potent than the nucleoside, at 26 ± 4 nM. It was determined that the mode of action of these purines was trypanostatic, with the compounds becoming trypanocidal only at much higher concentrations. Those 2,N
6
-disubstituted purines tested for their effects on purine transport in
T. b. brucei
displayed at best a moderate affinity for the transporters. It is highly probable that the large hydrophobic substitutions, which bestow high calculated octanol-water coefficient values on the analogs, allow them to diffuse across the membrane. Consistent with this view, the analogs were as effective against a
T. b. brucei
strain lacking the P2 nucleoside transporter as they were against the parental strain. As the analogs were not toxic to human cell lines, the purine analogs are likely to act on a trypanosome-specific target.
A Cysteine Protease Inhibitor Cures Chagas' Disease in an Immunodeficient-Mouse Model of Infection
Authors: Doyle Patricia S. , Zhou Yuan M. , Engel Juan C. , McKerrow James H.
Published: August 2007

Chagas' disease, caused by the parasite
Trypanosoma cruzi
, remains the leading cause of cardiopathy in Latin America with about 12 million people infected. Classic clinical manifestations derive from infection of muscle cells leading to progressive cardiomyopathy, while some patients develop megacolon or megaesophagus. A very aggressive clinical course including fulminant meningoencephalitis has been reported in patients who contract Chagas' disease in the background of immunodeficiency. This includes patients with human immunodeficiency virus infection as well as patients receiving immunosuppressive therapy for organ transplant. Currently, only two drugs are approved for the treatment of Chagas' disease, nifurtimox and benznidazole. Both have significant limitations due to common and serious side effects as well as limited availability. A promising group of new drug leads for Chagas' disease is cysteine protease inhibitors targeting cruzain, the major protease of
T. cruzi
. The inhibitor
N
-methyl-Pip-F-homoF-vinyl sulfonyl phenyl (
N
-methyl-Pip-F-hF-VSφ) is in late-stage preclinical development. Therefore, the question arose as to whether protease inhibitors targeting cruzain would have efficacy in Chagas' disease occurring in the background of immunodeficiency. To address this question, we studied the course of infection in recombinase-deficient (Rag1
−/−
) and normal mice infected with
T. cruzi
. Infections localized to heart and skeletal muscle in untreated normal animals, while untreated Rag1
−/−
mice showed severe infection in all organs and predominantly in liver and spleen. Treatment with the dipeptide
N
-methyl-Pip-F-hF-VSφ rescued immunodeficient animals from lethal Chagas' infection. The majority (60 to 100%) of inhibitor-treated Rag1
−/−
mice had increased survival, negative PCR, and normal tissues by histopathological examination.
Complete Nucleotide Sequence of the pCTX-M3 Plasmid and Its Involvement in Spread of the Extended-Spectrum β-Lactamase GeneblaCTX-M-3
Authors: Gołębiewski M. , Kern-Zdanowicz I. , Zienkiewicz M. , Adamczyk M. , Żyliǹska J. , Baraniak A. , Gniadkowski M. , Bardowski J. , Cegłowski P.
Published: August 2007

Here we report the nucleotide sequence of pCTX-M3, a highly conjugative plasmid that is responsible for the extensive spread of the gene coding for the CTX-M-3 extended-spectrum β-lactamase in clinical populations of the familyEnterobacteriaceaein Poland. The plasmid belongs to the IncL/M incompatibility group, is 89,468 bp in size, and carries 103 putative genes. BesidesblaCTX-M-3, it also bears theblaTEM-1,aacC2, andarmAgenes, as well as integronicaadA2,dfrA12, andsul1, which altogether confer resistance to the majority of β-lactams and aminoglycosides and to trimethoprim-sulfamethoxazole. The conjugal transfer genes are organized in two blocks,traandtrb, separated by a spacer sequence where almost all antibiotic resistance genes and multiple mobile genetic elements are located. OnlyblaCTX-M-3, accompanied by an ISEcp1element, is placed separately, in a DNA fragment previously identified as a fragment of theKluyvera ascorbatachromosome. On the basis of sequence analysis, we speculate that pCTX-M3 might have arisen from plasmid pEL60 from plant pathogenErwinia amylovoraby acquiring mobile elements with resistance genes. This suggests that plasmids of environmental bacterial strains could be the source of those plasmids now observed in bacteria pathogenic for humans.
Multiple Antibiotics Exert Delayed Effects against the
Plasmodium falciparum
Apicoplast
Authors: Dahl Erica L. , Rosenthal Philip J.
Published: August 2007

Several classes of antibiotics exert antimalarial activity. The mechanisms of action of antibiotics against malaria parasites have been unclear, and prior studies have led to conflicting results, in part because they studied antibiotics at suprapharmacological concentrations. We examined the antimalarial effects of azithromycin, ciprofloxacin, clindamycin, doxycycline, and rifampin against chloroquine-resistant (W2) and chloroquine-sensitive (3D7)
Plasmodium falciparum
strains. At clinically relevant concentrations, rifampin killed parasites quickly, preventing them from initiating cell division. In contrast, pharmacological concentrations of azithromycin, ciprofloxacin, clindamycin, and doxycycline were relatively inactive against parasites initially but exerted a delayed death effect, in which the progeny of treated parasites failed to complete erythrocytic development. The drugs that caused delayed death did not alter the distribution of apicoplasts into developing progeny. However, the apicoplasts inherited by the progeny of treated parasites were abnormal. The loss of apicoplast function became apparent as the progeny of antibiotic-treated parasites initiated cell division, with the failure of schizonts to fully mature or for erythrocyte rupture to take place. These findings explain the slow antimalarial action of multiple antibiotics.
Artemisinin-Resistant Mutants of
Toxoplasma gondii
Have Altered Calcium Homeostasis
Authors: Nagamune Kisaburo , Moreno Silvia N. J. , Sibley L. David
Published: August 2007

Artemisinin is a plant sesquiterpene lactone that has become an important drug for combating malaria, especially in regions where resistance to other drugs is widespread. While the mechanism of action is debated, artemisinin has been reported to inhibit the sarcoplasmic endoplasmic reticulum Ca
2+
ATPase (SERCA) in the malaria parasite. Artemisinin is also effective against
Toxoplasma
in vitro and in vivo, although it is less potent and, hence, is generally not used therapeutically to treat toxoplasmosis. To explore the mechanism of action, we generated chemically derived mutants of
Toxoplasma gondii
that were resistant to growth inhibition by this compound in vitro. Three artemisinin-resistant (ART
r
) mutant clones that differed in their sensitivities in vitro by three- to fivefold compared with that of the wild-type parasites were obtained. ART
r
mutants were cross-resistant to other derivatives of artemisinin, the most potent of which was artemisone. Resistance was not due to molecular alterations or differences in the expression of SERCA or other putative targets, such as proteins that code for multidrug resistance or translationally controlled tumor protein. ART
r
mutants were resistant to the induction of protein secretion from micronemes, a calcium-dependent process that is triggered by artemisinin. ART
r
mutants were not cross-resistant to secretion induced by thapsigargin but were more sensitive and were unable to regulate cytoslic calcium following treatment with this compound. These studies implicate calcium homeostasis in the mechanism of action of artemisinins against apicomplexan parasites.
Comparative Analysis of IncHI2 Plasmids Carrying
bla
CTX-M-2
or
bla
CTX-M-9
from
Escherichia coli
and
Salmonella enterica
Strains Isolated from Poultry and Humans
Authors: Fernández Aurora García , Cloeckaert Axel , Bertini Alessia , Praud Karine , Doublet Benoît , Weill François-Xavier , Carattoli Alessandra
Published: August 2007

Salmonella enterica bla
CTX-M-2
and
bla
CTX-M-9
plasmid backbones from isolates from Belgium and France were analyzed. The
bla
CTX-M-2-
plasmids from both human and poultry isolates were related to the IncHI2 pAPEC-O1-R plasmid, previously identified in the United States in avian
Escherichia coli
strains; the
bla
CTX-M-9
plasmids were closely related to the IncHI2 R478 plasmid.
Hemolysin and the Multifunctional Autoprocessing RTX Toxin Are Virulence Factors during Intestinal Infection of Mice with
Vibrio cholerae
El Tor O1 Strains
Authors: Olivier Verena , Haines G. Kenneth , Tan Yanping , Satchell Karla J. Fullner
Published: August 2007

The seventh cholera pandemic that started in 1961 was caused by
Vibrio cholerae
O1 strains of the El Tor biotype. These strains produce the pore-forming toxin hemolysin, a characteristic used clinically to distinguish classical and El Tor biotypes. Even though extensive in vitro data on the cytolytic activities of hemolysin exist, the connection of hemolysin to virulence in vivo is not well characterized. To study the contribution of hemolysin and other accessory toxins to pathogenesis, we utilized the model of intestinal infection in adult mice sensitive to the actions of accessory toxins. In this study, we showed that 4- to 6-week-old streptomycin-fed C57BL/6 mice were susceptible to intestinal infection with El Tor strains, which caused rapid death at high doses. Hemolysin had the predominant role in lethality, with a secondary contribution by the multifunctional autoprocessing RTX (MARTX) toxin. Cholera toxin and hemagglutinin/protease did not contribute to lethality in this model. Rapid death was not caused by increased dissemination due to a damaged epithelium since the numbers of CFU recovered from spleens and livers 6 h after infection did not differ between mice inoculated with hemolysin-expressing strains and those infected with non-hemolysin-expressing strains. Although accessory toxins were linked to virulence, a strain defective in the production of accessory toxins was still immunogenic since mice immunized with a multitoxin-deficient strain were protected from a subsequent lethal challenge with the wild type. These data suggest that hemolysin and MARTX toxin contribute to vaccine reactogenicity but that the genes for these toxins can be deleted from vaccine strains without affecting vaccine efficacy.
Six Genes Are Preferentially Transcribed by the Circulating and Sequestered Forms ofPlasmodium falciparumParasites That Infect Pregnant Women
Authors: Francis Susan E. , Malkov Vladislav A. , Oleinikov Andrew V. , Rossnagle Eddie , Wendler Jason P. , Mutabingwa Theonest K. , Fried Michal , Duffy Patrick E.
Published: August 2007

In areas of stable malaria transmission, susceptibility toPlasmodium falciparummalaria increases during first pregnancy. Women become resistant to pregnancy malaria over successive pregnancies as they acquire antibodies against the parasite forms that sequester in the placenta, suggesting that a vaccine is feasible. Placental parasites are antigenically distinct and bind receptors, like chondroitin sulfate A (CSA), that are not commonly bound by other parasites. We used whole-genome-expression analysis to find transcripts that distinguish parasites of pregnant women from other parasites and employed a novel approach to define and adjust for cell cycle timing of parasites. Transcription of six genes was substantially higher in both placental parasites and peripheral parasites from pregnant women, and each gene encodes a protein with a putative export sequence and/or transmembrane domain. This cohort of genes includesvar2csa, a member of the variant PfEMP1 gene family previously implicated in pregnancy malaria, as well as five conserved genes of unknown functions. Women in East Africa acquire antibodies over successive pregnancies against a protein encoded by one of these genes,PFD1140w, and this protein shows seroreactivity similar to that of VAR2CSA domains. These findings suggest that a suite of genes may be important for the genesis of the placental binding phenotype ofP. falciparumand may provide novel targets for therapeutic intervention.
CD4 T-Cell Epitopes Associated with Protective Immunity Induced following Vaccination of Mice with an Ehrlichial Variable Outer Membrane Protein
Authors: Nandi Bisweswar , Hogle Kathryn , Vitko Nicholas , Winslow Gary M.
Published: August 2007

The ehrlichiae express variable outer membrane proteins (OMPs) that play important roles in both pathogenesis and host defense. Previous studies revealed that OMPs are immunodominant B-cell antigens and that passive transfer of anti-OMP antibodies can protect SCID mice from fatal ehrlichial infection. In this study, we used a model of fatal monocytotropic ehrlichiosis caused by
Ehrlichia
bacteria from
Ixodes ovatus
(IOE) to determine whether OMP immunization could generate protective immunity in immunocompetent mice. Immunization of C57BL/6 mice with a purified recombinant OMP expressed by IOE
omp19
generated protection from fatal IOE infection and elicited robust humoral and CD4 T-cell responses. To identify CD4 T-cell epitopes within OMPs, we performed enzyme-linked immunospot analyses for gamma interferon (IFN-γ) production using a panel of overlapping 16-mer peptides from IOE OMP-19. Five immunoreactive peptides comprising residues 30 to 45, 77 to 92, 107 to 122, 197 to 212, and 247 to 264 were identified; the strongest response was generated against OMP-19
107-122
. Most of the peptides are conserved between
E. muris
and
E. chaffeensis
OMP-19, and they elicited IFN-γ production in CD4 T cells from
E. muris
-infected mice, indicating that T-cell epitope cross-reactivity likely contributes to heterologous immunity. Accordingly, CD4 T-cell responses to both OMP-19 and OMP-19
107-122
were of greater magnitude following high-dose IOE challenge of mice that had been immunized by prior infection with
E. muris
. Our studies cumulatively identify B- and T-cell epitopes that are associated with protective homologous and heterologous immunity during ehrlichial infection.
The O Antigen Enables
Bordetella parapertussis
To Avoid
Bordetella pertussis
-Induced Immunity
Authors: Wolfe Daniel N. , Goebel Elizabeth M. , Bjornstad Ottar N. , Restif Olivier , Harvill Eric T.
Published: August 2007

Bordetella pertussis
and
Bordetella parapertussis
are closely related endemic human pathogens which cause whooping cough, a disease that is reemerging in human populations. Despite how closely related these pathogens are, their coexistence and the limited efficacy of
B. pertussis
vaccines against
B. parapertussis
suggest a lack of cross-protective immunity between the two. We sought to address the ability of infection-induced immunity against one of these pathogens to protect against subsequent infection by the other using a mouse model of infection. Immunity induced by
B. parapertussis
infection protected against subsequent infections by either species. However, immunity induced by
B. pertussis
infection prevented subsequent
B. pertussis
infections but did not protect against
B. parapertussis
infections. The O antigen of
B. parapertussis
inhibited binding of antibodies to the bacterial surface and was required for
B. parapertussis
to colonize mice convalescent from
B. pertussis
infection. Thus, the O antigen of
B. parapertussis
confers asymmetrical cross-immunity between the causative agents of whooping cough. We propose that these findings warrant investigation of the relative role of
B. parapertussis
in the resurgence of whooping cough.
Monomeric Expression of Bovine β2-Integrin Subunits Reveals Their Role inMannheimia haemolyticaLeukotoxin-Induced Biological Effects
Authors: Dassanayake Rohana P. , Maheswaran Samuel K. , Srikumaran Subramaniam
Published: August 2007

The ruminant-specific leukotoxin (Lkt) ofMannheimia haemolyticais the key virulence factor contributing to the pathogenesis of lung injury in bovine pneumonic pasteurellosis. Previous studies by us and others indicate thatM. haemolyticaLkt binds to CD18, the β subunit of bovine β2-integrins on leukocytes, and that the species specificity of Lkt-induced effects is resident in the β subunit CD18 and not in the α subunit CD11. However, Lkt also binds to the CD11a subunit of LFA-1. Furthermore, antibodies specific for CD18 or CD11a inhibit signaling events leading to elevation of intracellular [Ca2+], tyrosine phosphorylation of the cytosolic domain of CD18, and cytolysis of bovine leukocytes. These observations underscore the need for further investigation to identify the precise subunit of bovine LFA-1 utilized byM. haemolyticaLkt as the functional receptor. For this purpose, monomeric bovine CD18 and CD11a and heterodimeric LFA-1 were expressed in the HEK-293 cell line by transfection, and the resulting transfectants were tested for susceptibility to Lkt-induced effects. All three transfectants effectively bound Lkt. However, Lkt-induced cytolysis was observed only with transfectants expressing monomeric bovine CD18 or LFA-1. Furthermore, intracellular [Ca2+] elevation following exposure to Lkt, which is a marker for postbinding signaling leading to cellular activation, was seen only with transfectants expressing monomeric bovine CD18 or LFA-1. These results clearly indicate that the bovine CD18 subunit of β2-integrins is the functional receptor forM. haemolyticaLkt.
Taenia solium
Oncosphere Adhesion to Intestinal Epithelial and Chinese Hamster Ovary Cells In Vitro
Authors: Verastegui Manuela , Gilman Robert H. , Arana Yanina , Barber Dylan , Velásquez Jeanette , Farfán Marilu , Chile Nancy , Kosek Jon C. , Kosek Margaret , Garcia Hector H. , Gonzalez Armando
Published: August 2007

The specific mechanisms underlying
Taenia solium
oncosphere adherence and penetration in the host have not been studied previously. We developed an in vitro adhesion model assay to evaluate the mechanisms of
T. solium
oncosphere adherence to the host cells. The following substrates were used: porcine intestinal mucosal scrapings (PIMS), porcine small intestinal mucosal explants (PSIME), Chinese hamster ovary cells (CHO cells), epithelial cells from ileocecal colorectal adenocarcinoma (HCT-8 cells), and epithelial cells from colorectal adenocarcinoma (Caco-2 cells). CHO cells were used to compare oncosphere adherence to fixed and viable cells, to determine the optimum time of oncosphere incubation, to determine the role of sera and monolayer cell maturation, and to determine the effect of temperature on oncosphere adherence. Light microscopy, scanning microscopy, and transmission microscopy were used to observe morphological characteristics of adhered oncospheres. This study showed in vitro adherence of activated
T. solium
oncospheres to PIMS, PSIME, monolayer CHO cells, Caco-2 cells, and HCT-8 cells. The reproducibility of
T. solium
oncosphere adherence was most easily measured with CHO cells. Adherence was enhanced by serum-binding medium with >5% fetal bovine serum, which resulted in a significantly greater number of oncospheres adhering than the number adhering when serum at a concentration less than 2.5% was used (
P
< 0.05). Oncosphere adherence decreased with incubation of cells at 4°C compared with the adherence at 37°C. Our studies also demonstrated that
T. solium
oncospheres attach to cells with elongated microvillus processes and that the oncospheres expel external secretory vesicles that have the same oncosphere processes.
WAVE FRONTS AND THE RADIATION PRINCIPLE
Authors: EIDUS D.
Published: August 2007

We are concerned with the construction of Sommerfeld-type radiation conditions for stationary acoustic oscillations in inhomogeneous media with densities independent of r. It is shown that such radiation conditions exist iff there exists a one-parameter family of closed homothetic star-shaped (with respect to origin) wave fronts. These radiation conditions select the same solutions of the reduced wave equation as the limiting absorption principle.
NUMERICALLY FLAT HIGGS VECTOR BUNDLES
Authors: BRUZZO UGO , GRAÑA OTERO BEATRIZ
Published: August 2007

After providing a suitable definition of numerical effectiveness for Higgs bundles, and a related notion of numerical flatness, in this paper we prove, together with some side results, that all Chern classes of a Higgs-numerically flat Higgs bundle vanish, and that a Higgs bundle is Higgs-numerically flat if and only if it is has a filtration whose quotients are flat stable Higgs bundles. We also study the relation between these numerical properties of Higgs bundles and (semi)stability.
A Thr94Ala mutation in human liver fatty acid-binding protein contributes to reduced hepatic glycogenolysis and blunted elevation of plasma glucose levels in lipid-exposed subjects
Authors: Weickert Martin O. , Loeffelholz Christian v. , Roden Michael , Chandramouli Visvanathan , Brehm Attila , Nowotny Peter , Osterhoff Martin A. , Isken Frank , Spranger Jochen , Landau Bernard R. , Pfeiffer Andreas F. H. , Möhlig Matthias
Published: August 2007

Liver fatty acid-binding protein (L-FABP) is a highly conserved key factor in lipid metabolism. Amino acid replacements in L-FABP might alter its function and thereby affect glucose metabolism in lipid-exposed subjects, as indicated by studies in L-FABP knockout mice. Amino acid replacements in L-FABP were investigated in a cohort of 1,453 Caucasian subjects. Endogenous glucose production (EGP), gluconeogenesis, and glycogenolysis were measured in healthy carriers of the only common Thr94-to-Ala amino acid replacement (Ala/Ala94) vs. age-, sex-, and BMI-matched wild-type (Thr/Thr94) controls at baseline and after 320-min lipid/heparin-somatostatin-insulin-glucagon clamps ( n = 18). Whole body glucose disposal was further investigated (subset; n = 13) using euglycemic-hyperinsulinemic clamps without and with lipid/heparin infusion. In the entire cohort, the only common Ala/Ala94 mutation was significantly associated with reduced body weight, which is in agreement with a previous report. In lipid-exposed, individually matched subjects there was a genotype vs. lipid-treatment interaction for EGP ( P = 0.009) driven mainly by reduced glycogenolysis in Ala/Ala94 carriers (0.46 ± 0.05 vs. 0.59 ± 0.05 mg·kg−1·min−1, P = 0.013). The lipid-induced elevation of plasma glucose levels was smaller in Ala/Ala94 carriers compared with wild types ( P < 0.0001). Whole body glucose disposal was not different between lipid-exposed L-FABP genotypes. In summary, the Ala/Ala94-mutation contributed significantly to reduced glycogenolysis and less severe hyperglycemia in lipid-exposed humans and was further associated with reduced body weight in a large cohort. Data clearly show that investigation of L-FABP phenotypes in the basal overnight-fasted state yielded incomplete information, and a challenge test was essential to detect phenotypical differences in glucose metabolism between L-FABP genotypes.
Stimulated PI3K-AKT Signaling Mediated through Ligand or Radiation-Induced EGFR Depends Indirectly, but not Directly, on Constitutive K-Ras Activity
Authors: Toulany Mahmoud , Baumann Michael , Rodemann H. Peter
Published: August 2007

Previous results showed an inducible radiation sensitivity selectively observable for K-RAS–mutated cell lines as a function of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor blockade of phosphatidylinositol 3-kinase (PI3K)-AKT signaling. Therefore, the role of K-Ras activity for a direct (i.e., through activation of PI3K by K-Ras) or an indirect stimulation of PI3K-AKT signaling (through K-Ras activity–dependent EGFR ligand production) was investigated by means of small interfering RNA and inhibitor approaches as well as ELISA measurements of EGFR ligand production. K-RASmt tumor cells presented a constitutively activated extracellular signal–regulated kinase-1/2 signaling, resulting in enhanced production and secretion of the EGFR ligand amphiregulin (AREG). Medium supernatants conditioned by K-RASmt tumor cells equally efficiently stimulated EGFR signaling into the PI3K-AKT and mitogen-activated protein kinase pathways. Knocking down K-Ras expression by specific small interfering RNA markedly affected autocrine production of AREG, but not PI3K-AKT signaling, after treatment of K-RAS–mutated or wild-type cells with EGFR ligands or exposure to ionizing radiation. These results indicate that PI3K-mediated activation of AKT in K-RASmt human tumor cells as a function of EGFR ligand or radiation stimulus is independent of a direct function of K-Ras enzyme activity but depends on a K-Ras–mediated enhanced production of EGFR ligands (i.e., most likely AREG) through up-regulated extracellular signal–regulated kinase-1/2 signaling. The data provide new differential insight into the importance of K-RAS mutation in the context of PI3K-AKT–mediated radioresistance of EGFR-overexpressing or EGFR-mutated tumors. (Mol Cancer Res 2007;5(8):863–72)
Activated Signal Transducers and Activators of Transcription 3 Signaling Induces CD46 Expression and Protects Human Cancer Cells from Complement-Dependent Cytotoxicity
Authors: Buettner Ralf , Huang Mei , Gritsko Tanya , Karras Jim , Enkemann Steve , Mesa Tania , Nam Sangkil , Yu Hua , Jove Richard
Published: August 2007

CD46 is one of the complement-regulatory proteins expressed on the surface of normal and tumor cells for protection against complement-dependent cytotoxicity. Cancer cells need to access the blood circulation for continued growth and metastasis, thus exposing themselves to destruction by complement system components. Previous studies have established that the signal transducers and activators of transcription 3 (STAT3) transcription factor is persistently activated in a wide variety of human cancer cells and primary tumor tissues compared with their normal counterparts. Using microarray gene expression profiling, we identified the CD46 gene as a target for activated STAT3 signaling in human breast and prostate cancer cells. The CD46 promoter contains two binding sites for activated STAT3 and mutations introduced into the major site abolished STAT3 binding. Chromatin immunoprecipitation confirms binding of STAT3 to the CD46 promoter. CD46 promoter activity is induced by activation of STAT3 and blocked by a dominant-negative form of STAT3 in luciferase reporter assays. CD46 mRNA expression is induced by interleukin-6 and by transient transfection of normal human epithelial cells with a persistently active mutant construct of STAT3, STAT3C. Furthermore, we show that inhibition of STAT3-mediated CD46 cell surface expression sensitizes DU145 prostate cancer cells to cytotoxicity in an in vitro complement lysis assay using rabbit anti-DU145 antiserum and rabbit complement. These results show that activated STAT3 signaling induces the CD46 promoter and protects human cancer cells from complement-dependent cytotoxicity, suggesting a potential mechanism whereby oncogenic signaling contributes to tumor cell evasion of antibody-mediated immunity. (Mol Cancer Res 2007;5(8):823–32)
The Opposing Effect of Hypoxia-Inducible Factor-2α on Expression of Telomerase Reverse Transcriptase
Authors: Lou Fenglan , Chen Xinxia , Jalink Marit , Zhu Qingjun , Ge Nan , Zhao Shengtian , Fang Xiaolei , Fan Yidong , Björkholm Magnus , Liu Zhaoxu , Xu Dawei
Published: August 2007

Hypoxia-inducible factor-1α (HIF-1α) has been implicated in the transcriptional regulation of the telomerase reverse transcriptase (hTERT) gene expression and telomerase activity, essential elements for cellular immortalization and transformation. However, controversial results were obtained in different studies. Moreover, it is totally unclear whether HIF-2α, the paralog of HIF-1α, plays a role in regulating hTERT expression. In the present study, we found that hypoxic treatment enhanced hTERT mRNA expression and telomerase activity in three renal cell carcinoma (RCC) cell lines with different genetic backgrounds. Both HIF-1α and HIF-2α were capable of significantly increasing the hTERT promoter activity in these cells. Moreover, depleting HIF-2α led to a down-regulation of hTERT mRNA level in RCC A498 cells expressing constitutive HIF-2α. It was found that HIF-2α bound to the hTERT proximal promoter and enhanced the recruitment of the histone acetyltransferase p300 and histone H3 acetylation locally in A498 cells treated with hypoxia. Increased levels of hTERT mRNA were observed in two of three hypoxia-treated malignant glioma cell lines. However, HIF-1α stimulated whereas HIF-2α inhibited the hTERT promoter activity in these glioma cell lines. Ectopic expression of HIF-2α resulted in diminished hTERT expression in glioma cells. Collectively, HIF-1α activates hTERT and telomerase expression in both RCC and glioma cells, and HIF-2α enhances hTERT expression in RCC cells, whereas it represses the hTERT transcription in glioma cells. These findings reveal a complex relationship between HIF-1α/2α and hTERT/telomerase expression in malignant cells, which may have both biological and clinical implications. (Mol Cancer Res 2007;5(8):793–800)
(Dihydro)ceramide Synthase 1–Regulated Sensitivity to Cisplatin Is Associated with the Activation of p38 Mitogen-Activated Protein Kinase and Is Abrogated by Sphingosine Kinase 1
Authors: Min Junxia , Mesika Adi , Sivaguru Mayandi , Van Veldhoven Paul P. , Alexander Hannah , Futerman Anthony H. , Alexander Stephen
Published: August 2007

Resistance to chemotherapeutic drugs often limits their clinical efficacy. Previous studies have implicated the bioactive sphingolipid sphingosine-1-phosphate (S-1-P) in regulating sensitivity to cisplatin [cis-diamminedichloroplatinum(II)] and showed that modulating the S-1-P lyase can alter cisplatin sensitivity. Here, we show that the members of the sphingosine kinase (SphK1 and SphK2) and dihydroceramide synthase (LASS1/CerS1, LASS4/CerS4, and LASS5/CerS5) enzyme families each have a unique role in regulating sensitivity to cisplatin and other drugs. Thus, expression of SphK1 decreases sensitivity to cisplatin, carboplatin, doxorubicin, and vincristine, whereas expression of SphK2 increases sensitivity. Expression of LASS1/CerS1 increases the sensitivity to all the drugs tested, whereas LASS5/CerS5 only increases sensitivity to doxorubicin and vincristine. LASS4/CerS4 expression has no effect on the sensitivity to any drug tested. Reflecting this, we show that the activation of the p38 mitogen-activated protein (MAP) kinase is increased only by LASS1/CerS1, and not by LASS4/CerS4 or LASS5/CerS5. Cisplatin was shown to cause a specific translocation of LASS1/CerS1, but not LASS4/CerS4 or LASS5/CerS5, from the endoplasmic reticulum (ER) to the Golgi apparatus. Supporting the hypothesis that this translocation is mechanistically involved in the response to cisplatin, we showed that expression of SphK1, but not SphK2, abrogates both the increased cisplatin sensitivity in cells stably expressing LASS1/CerS and the translocation of the LASS1/CerS1. The data suggest that the enzymes of the sphingolipid metabolic pathway can be manipulated to improve sensitivity to the widely used drug cisplatin. (Mol Cancer Res 2007;5(8):801–12)
Ataxia Telangiectasia-Mutated–Dependent DNA Damage Checkpoint Functions Regulate Gene Expression in Human Fibroblasts
Authors: Zhou Tong , Chou Jeff , Zhou Yingchun , Simpson Dennis A. , Cao Feng , Bushel Pierre R. , Paules Richard S. , Kaufmann William K.
Published: August 2007

The relationships between profiles of global gene expression and DNA damage checkpoint functions were studied in cells from patients with ataxia telangiectasia (AT). Three telomerase-expressing AT fibroblast lines displayed the expected hypersensitivity to ionizing radiation (IR) and defects in DNA damage checkpoints. Profiles of global gene expression in AT cells were determined at 2, 6, and 24 h after treatment with 1.5-Gy IR or sham treatment and were compared with those previously recognized in normal human fibroblasts. Under basal conditions, 160 genes or expressed sequence tags were differentially expressed in AT and normal fibroblasts, and these were associated by gene ontology with insulin-like growth factor binding and regulation of cell growth. On DNA damage, 1,091 gene mRNAs were changed in at least two of the three AT cell lines. When compared with the 1,811 genes changed in normal human fibroblasts after the same treatment, 715 were found in both AT and normal fibroblasts, including most genes categorized by gene ontology into cell cycle, cell growth, and DNA damage response pathways. However, the IR-induced changes in these 715 genes in AT cells usually were delayed or attenuated in comparison with normal cells. The reduced change in DNA damage response genes and the attenuated repression of cell cycle–regulated genes may account for the defects in cell cycle checkpoint function in AT cells. (Mol Cancer Res 2007;5(8):813–22)