bluuebunny/crossref_metadata_2025 huggingface dataset:
Type I photosynthetic reaction centres: structure and function
Authors: Heathcote Peter , Jones Michael R. , Fyfe Paul K.
Published: February 2003

We review recent advances in the study of the photosystem I reaction centre, following the determination of a spectacular 2.5 Å resolution crystal structure for this complex of
Synechococcus elongatus
. Photosystem I is proving different to type II reaction centres in structure and organization, and the mechanism of transmembrane electron transfer, and is providing insights into the control of function in reaction centres that operate at very low redox potentials. The photosystem I complex of oxygenic organisms has a counterpart in non–oxygenic bacteria, the strictly anaerobic phototrophic green sulphur bacteria and heliobacteria. The most distinctive feature of these type I reaction centres is that they contain two copies of a large core polypeptide (i.e. a homodimer), rather than a heterodimeric arrangement of two related, but different, polypeptides as in the photosystem I complex. To compare the structural organization of the two forms of type I reaction centre, we have modelled the structure of the central region of the reaction centre from green sulphur bacteria, using sequence alignments and the structural coordinates of the
S. elongatus
Photosystem I complex. The outcome of these modelling studies is described, concentrating on regions of the type I reaction centre where important structure–function relationships have been demonstrated or inferred.
Parasite plastids: maintenance and functions
Authors: Wilson R. J. M. (Iain) , Rangachari K. , Saldanha J. W. , Rickman L. , Buxton R. S. , Eccleston J. F.
Published: February 2003

Malaria and related parasites retain a vestigial, but biosynthetically active, plastid organelle acquired far back in evolution from a red algal cell. The organelle appears to be essential for parasite transmission from cell to cell and carries the smallest known plastid genome. Why has this genome been retained? The genes it carries seem to be dedicated to the expression of just two ‘housekeeping’ genes. We speculate that one of these, called
ycf24
in plants and
sufB
in bacteria, is tied to an essential ‘dark’ reaction of the organelle – fatty acid biosynthesis. ‘Ball–park’ clues to the function of bacterial
suf
genes have emerged only recently and point to the areas of iron homeostasis, [Fe–S] cluster formation and oxidative stress. We present experimental evidence for a physical interaction between SufB and its putative partner SufC (
ycf16
). In both malaria and plants, SufC is encoded in the nucleus and specifies an ATPase that is imported into the plastid.
Genomes at the interface between bacteria and organelles
Authors: Douglas Angela E. , Raven John A.
Published: February 2003

The topic of the transition of the genome of a free–living bacterial organism to that of an organelle is addressed by considering three cases. Two of these are relatively clear–cut as involving respectively organisms (cyanobacteria) and organelles (plastids). Cyanobacteria are usually free–living but some are involved in symbioses with a range of eukaryotes in which the cyanobacterial partner contributes photosynthesis, nitrogen fixation, or both of these. In several of these symbioses the cyanobacterium is vertically transmitted, and in a few instances, sufficient unsuccessful attempts have been made to culture the cyanobiont independently for the association to be considered obligate for the cyanobacterium. Plastids clearly had a cyanobacterial ancestor but cannot grow independently of the host eukaryote. Plastid genomes have at most 15% of the number of genes encoded by the cyanobacterium with the smallest number of genes; more genes than are retained in the plastid genome have been transferred to the eukaryote nuclear genome, while the rest of the cyanobacterial genes have been lost. Even the most cyanobacteria–like plastids, for example the ‘cyanelles’ of glaucocystophyte algae, are functionally and genetically very similar to other plastids and give little help in indicating intermediates in the evolution of plastids. The third case considered is the vertically transmitted intracellular bacterial symbionts of insects where the symbiosis is usually obligate for both partners. The number of genes encoded by the genomes of these obligate symbionts is intermediate between that of organelles and that of free–living bacteria, and the genomes of the insect symbionts also show rapid rates of sequence evolution and AT (adenine, thymine) bias. Genetically and functionally, these insect symbionts show considerable similarity to organelles.
The relationship between consumer characteristics and attitude toward online shopping
Authors: Wu Shwu‐Ing
Published: February 2003

The purpose of the experiment reported here was to examine Internet user concerns and perceptions of online shopping. The attitude of Internet users toward online shopping was measured using the Fishbein model. The relative factors influencing user attitudes toward online shopping and the relationship between the attitude and the influence factors were explored. The results show that the Fishbein model can effectively measure consumer attitudes and the examined consumer characteristics were important influence factors on consumer attitudes and online shopping decisions.
The Framsticks system: versatile simulator of 3D agents and their evolution
Authors: Komosin´ski Maciej
Published: February 2003

Various aspects of the Framsticks system are described. The system is a universal tool for modeling, simulating and optimizing virtual agents, with three‐dimensional body and embedded control system. Simulation model is described first. Then features of the system framework are presented, with typical and potential applications. Specific tools supporting human understanding of evolutionary processes, control and behaviors are also outlined. Finally, the most interesting research experiments are summarized.
The impact of school‐based management on supervision instructors’ professional considerations
Authors: Nir Adam E.
Published: February 2003

The following study examines how, and to what extent, the introduction of school‐based management (SBM) in schools and the authority thereby delegated to principals to hire and dismiss supervision instructors have changed instructors’ role expectations and job conflict and affected their professional considerations. Based on data gathered from in‐depth interviews, it was evident that before SBM, supervision instructors typically faced multiple and contradicting expectations and, therefore, used various strategies to avoid role conflicts. However, after SBM was introduced, the discrepancy among these expectations has increased, and so did the uncertainty and insecurity that instructors perceived on the job. These circumstances have encouraged instructors to prefer personal concerns over professional obligations and to direct their efforts so that their future employment will be ensured. The study concludes that school principals need to increase their professional knowledge regarding supervision instruction and devote their efforts towards establishing an organizational learning culture in their schools.
Privacy in Canadian Health Networks: challenges and opportunities
Authors: Mills S. Keith , Yao Rico S. , Chan Yolande E.
Published: February 2003

Privacy and security are coming under more and more scrutiny in this age of digital information that can be generated, duplicated, and transferred with increasing facility. Nowhere is this so apparent as in the field of health care, where breaches to security and privacy carry very personal and potentially harmful consequences. Health Information Networks must deal with these issues carefully as they seek to share sensitive information among health‐care providers to improve patient care. This article examines issues related to privacy in Health Information Networks in Canada, provides a summary of relevant federal and provincial legislation, and through a case study offers suggestions for future directions in the arena where health‐care and privacy issues meet.
Direct Fabrication of Large Micropatterned Single Crystals
Authors: Aizenberg Joanna , Muller David A. , Grazul John L. , Hamann D. R.
Published: February 2003

Micropatterning of single crystals for technological applications is a complex, multistep process. Nature provides alternative fabrication strategies, when crystals with exquisite micro-ornamentation directly develop within preorganized frameworks. We report a bio-inspired approach to growing large micropatterned single crystals. Micropatterned templates organically modified to induce the formation of metastable amorphous calcium carbonate were imprinted with calcite nucleation sites. The template-directed deposition and crystallization of the amorphous phase resulted in the fabrication of millimeter-sized single calcite crystals with sub–10-μm patterns and controlled crystallographic orientation. We suggest that in addition to regulating the shape, micropatterned frameworks act as sites for stress and impurity release during the amorphous-to-crystalline transition. The proposed mechanisms may have direct biological relevance and broad implications in materials synthesis.
Deletion of Two-Component Regulatory Systems Increases the Virulence of
Mycobacterium tuberculosis
Authors: Parish Tanya , Smith Debbie A. , Kendall Sharon , Casali Nicola , Bancroft Gregory J. , Stoker Neil G.
Published: February 2003

Two-component regulatory signal transduction systems are widely distributed among bacteria and enable the organisms to make coordinated changes in gene expression in response to a variety of environmental stimuli. The genome sequence of
Mycobacterium tuberculosis
contains 11 complete two-component systems, four isolated homologous regulators, and three isolated homologous sensors. We have constructed defined mutations in six of these genes and measured virulence in a SCID mouse model. Mice infected with four of the mutants (deletions of
devR
,
tcrXY
,
trcS
, and
kdpDE
) died more rapidly than those infected with wild-type bacteria. The other two mutants (
narL
and
Rv3220c
) showed no change compared to the wild-type H37Rv strain. The most hypervirulent mutant (
devR
Δ) also grew more rapidly in the acute stage of infection in immunocompetent mice and in gamma interferon-activated macrophages. These results define a novel class of genes in this pathogen whose presence slows down its multiplication in vivo or increases its susceptibility to host killing mechanisms. Thus,
M. tuberculosis
actively maintains a balance between its own survival and that of the host.
Inhalational Poisoning by Botulinum Toxin and Inhalation Vaccination with Its Heavy-Chain Component
Authors: Park Jong-Beak , Simpson Lance L.
Published: February 2003

Botulinum toxin is the etiologic agent responsible for the disease botulism, which is characterized by peripheral neuromuscular blockade. Botulism is ordinarily encountered as a form of oral poisoning. The toxin is absorbed from the lumen of the gut to reach the general circulation and is then distributed to peripheral cholinergic nerve endings. However, there is a widespread presumption that botulinum toxin can also act as an inhalation poison, which would require that it be absorbed from the airway. Experiments have been done to show that both pure toxin and progenitor toxin (a complex with auxiliary proteins) are inhalation poisons. Interestingly, the data indicate that auxiliary proteins are not necessary to protect the toxin or to facilitate its absorption. When studied on rat primary alveolar epithelial cells or on immortalized human pulmonary adenocarcinoma (Calu-3) cells, botulinum toxin displayed both specific binding and transcytosis. The rate of transport was greater in the apical-to-basolateral direction than in the basolateral-to-apical direction. Transcytosis was energy dependent, and it was blocked by serotype-specific antibody. The results demonstrated that the holotoxin was not essential for the process of binding and transcytosis. Both in vivo and in vitro experiments showed that the heavy-chain component of the toxin was transported across epithelial monolayers, which indicates that the structural determinants governing binding and transcytosis are found in this fragment. The heavy chain was not toxic, and therefore it was tested for utility as an inhalation vaccine against the parent molecule. This fragment was shown to evoke complete protection against toxin doses of at least 104times the 50% lethal dose.
Rho GTPase Is Activated by Cytotoxic Necrotizing Factor 1 in Peripheral Blood T Lymphocytes: Potential Cytotoxicity for Intestinal Epithelial Cells
Authors: Brest Patrick , Mograbi Baharia , Hofman Véronique , Loubat Agnès , Rossi Bernard , Auberger Patrick , Hofman Paul
Published: February 2003

Some strains ofEscherichia colirelated to acute cystitis or colitis produce a toxin named cytotoxic necrotizing factor 1 (CNF-1). CNF-1 mediates its effects on epithelial cells or phagocytes via the permanent activation of small GTP-binding proteins, caused by the toxin-induced deamidation of Glu63of p21 Rho. The behavior of peripheral blood T lymphocytes during the acute phase of bacterial colitis has been poorly investigated. Our study was conducted to test whether (i) peripheral blood T lymphocytes can be activated by CNF-1 and (ii) CNF-1-activated T lymphocytes are cytotoxic against intestinal epithelial cells. Activation of T lymphocytes by CNF-1 was assessed by electrophoresis, flow cytometry, confocal microscopy, and electron microscopy studies. Assays for migration and adherence of CNF-1-treated T lymphocytes were performed in Transwell chambers with T84 intestinal epithelial cells grown on polycarbonate semipermeable filters. CNF-1 induced a decrease in the electrophoretic mobility of the GTP-binding protein Rho in treated T lymphocytes. CNF-1 provoked an increase in the content of actin stress fibers and pseudopodia in T lymphocytes. Several adherence molecules were clustered into cytoplasmic projections in CNF-1-treated T lymphocytes and adherence of such lymphocytes on the basolateral pole of T84 was increased, resulting in cytotoxicity toward epithelial cells. Such enhanced adherence in response to CNF-1 was dependent on p42-44MAPkinase activation of T lymphocytes. Taken together, these results suggest that CNF-1, by acting on T lymphocytes, may increase in an important fashion the virulence of certain strains ofE. coliagainst the intestinal epithelia.
Polymorphic Membrane Protein H Has Evolved in Parallel with the Three Disease-Causing Groups ofChlamydia trachomatis
Authors: Stothard Diane R. , Toth Gregory A. , Batteiger Byron E.
Published: February 2003

Chlamydia trachomatisis a human pathogen causing trachoma, urogenital disease, and lymphogranuloma venereum (LGV). A family of nine polymorphic membrane protein genes (pmpAtopmpI), resembling autotransporter proteins, has recently been discovered inC. trachomatis. pmpgenes are large and predicted to be outer membrane proteins. We hypothesized that they would contain useful nucleotide sequence variability for epidemiologic studies. Since sequence information is available only for serovars D and L2, we sought to determine the amount of diversity within an individualpmpgene among serovars. We used restriction fragment length polymorphism (RFLP) analysis as a primary screen to assess the amount of sequence divergence among thepmpgenes for serovars A to L3 ofC. trachomatis. RFLP analysis showed little variation for some of the genes, such aspmpA, but substantial variation in others, such aspmpI. pmpHandpmpEyielded RFLP patterns that clustered the 15 serovars into ocular, urogenital, and LGV groups, and both proteins have been localized to the outer membrane. Therefore, we chose to sequencepmpE,pmpH, andpmpIfrom each of the 15 serovars. Evolutionary analysis showed three distinct divergence patterns. PmpI was least variable, resulting in an ambiguous evolutionary pattern. PmpE showed a high degree of diversity in the ocular strains compared to the other strains. Finally, the evolution of PmpH shows three groups that reflect disease groups, suggesting this protein may play a role in pathogenesis.
Expression of Truncated Internalin A Is Involved in Impaired Internalization of Some
Listeria monocytogenes
Isolates Carried Asymptomatically by Humans
Authors: Olier Maïwenn , Pierre Fabrice , Rousseaux Sandrine , Lemaître Jean-Paul , Rousset André , Piveteau Pascal , Guzzo Jean
Published: February 2003

Fourteen human carriage
Listeria monocytogenes
isolates were compared to sporadic and epidemic-associated human strains in order to ascertain the pathogenic behavior of these unrecognized asymptomatic strains. Experimental infection of 14-day-old chick embryos revealed that the majority of the carriage strains were attenuated for virulence. Of the 10 attenuated carriage strains, 5 were affected in their invasion capacities in vitro. Western blot analysis with antibody directed against InlA, the surface protein implicated in the internalization in host cells, allowed correlation between the ability of the carriage strains to enter Caco-2 cells and InlA expression. Indeed, these five carriage strains produced truncated forms of InlA. Four of the five truncated forms of InlA had an apparent molecular mass of 47 kDa. In order to assess the existence of a genetic lineage, partial sequences of
inlA
gene of these four strains were compared and revealed that they had a high degree of sequence conservation at the gene (99.86%) and amino acid (100%) levels. Comparison of their nucleotide sequences with that of the corresponding segment of
inlA
from EGD-e and Scott A strains, taken as epidemic references, showed more divergence. Taken together, these observations suggest the presence of specific traits that characterize
L. monocytogenes
strains isolated during asymptomatic carriage. Some of these traits could provide some explanations about the determinants that make them unable to cause systemic human infection.
Nitric Oxide Partially ControlsCoxiella burnetiiPhase II Infection in Mouse Primary Macrophages
Authors: Zamboni Dario S. , Rabinovitch Michel
Published: February 2003

In most primary or continuous cell cultures infected with the Q-fever agentCoxiella burnetii, bacteria are typically sheltered in phagolysosome-like, large replicative vacuoles (LRVs). We recently reported that only a small proportion of mouse peritoneal macrophages (PMΦ) infected with a nonvirulent, phase II strain ofC. burnetiideveloped LRVs and that their relative bacterial load increased only slowly. In the majority of infected PMΦ, the bacteria were confined to the small vesicles. We show here that nitric oxide (NO) induced by the bacteria partially accounts for the restricted development of LRVs in primary macrophages. Thus, (i) PMΦ and bone marrow-derived macrophages (BMMΦ) challenged with phase IIC. burnetiiproduced significant amounts of NO; (ii) the NO synthase inhibitors aminoguanidine andN-methyl-l-arginine reduced the production of NO and increased the frequency of LRVs (although the relative bacterial loads of individual LRVs did not change, the estimated loads per well increased appreciably); (iii) gamma interferon (IFN-γ) or the NO donor sodium nitroprusside, added to BMMΦ prior to or after infection, reduced the development and the relative bacterial loads of LRVs and lowered the yield of viable bacteria recovered from the cultures; and (iv) these effects of IFN-γ may not be entirely dependent on the production of NO since IFN-γ also controlled the infection in macrophages from inducible NO synthase knockout mice. It remains to be determined whether NO reduced the development of LRVs by acting directly on the bacteria; by acting on the traffic, fusion, or fission of cell vesicles; or by a combination of these mechanisms.
HilE Interacts with HilD and Negatively Regulates
hilA
Transcription and Expression of the
Salmonella enterica
Serovar Typhimurium Invasive Phenotype
Authors: Baxter M. Aaron , Fahlen Thomas F. , Wilson Rebecca L. , Jones Bradley D.
Published: February 2003

The ability of
Salmonella enterica
serovar Typhimurium to traverse the intestinal mucosa of a host is an important step in its ability to initiate gastrointestinal disease. The majority of the genes required for this invasive characteristic are encoded on
Salmonella
pathogenicity island 1 (SPI1), and their expression is controlled by the transcriptional activator HilA, a member of the OmpR/ToxR family of proteins. A variety of genes (
hilC
,
hilD
,
fis
,
sirA
/
barA
,
csrAB
,
phoB
,
fadD
,
envZ
/
ompR
,
fliZ
,
hilE
,
ams
,
lon
,
pag
, and
hha
) have been identified that exert positive or negative effects on
hilA
expression, although the mechanisms by which these gene products function remain relatively unclear. Recent work indicates that the small DNA-binding protein, Hha, has a significant role in repressing
hilA
transcription and the invasive phenotype, particularly in response to osmolarity signals. We have characterized the
Salmonella
-specific gene,
hilE
, and found that it plays an important regulatory role in
hilA
transcription and invasion gene expression. Mutation of
hilE
causes derepression of
hilA
transcription, and overexpression of
hilE
superrepresses
hilA
expression and the invasive phenotype. Bacterial two-hybrid experiments indicate that the HilE protein interacts with HilD, suggesting a possible mechanism for HilE negative regulation of
hilA
gene expression and the
Salmonella
invasive phenotype. Finally, we have found that the
hilE
gene resides on a region of the serovar Typhimurium chromosome that has many characteristics of a pathogenicity island.
EnterohemorrhagicEscherichia coliO157:H7 Disrupts Stat1-Mediated Gamma Interferon Signal Transduction in Epithelial Cells
Authors: Ceponis Peter J. M. , McKay Derek M. , Ching Joyce C. Y. , Pereira Perpetual , Sherman Philip M.
Published: February 2003

EnterohemorrhagicEscherichia coli(EHEC) O157:H7 is a clinically important bacterial enteropathogen that manipulates a variety of host cell signal transduction cascades to establish infection. However, the effect of EHEC O157:H7 on Jak/Stat signaling is unknown. To define the effect of EHEC infection on epithelial gamma interferon (IFN-γ)-Stat1 signaling, human T84 and HEp-2 epithelial cells were infected with EHEC O157:H7 and then stimulated with recombinant human IFN-γ. Cells were also infected with different EHEC strains, heat-killed EHEC, enteropathogenicE. coli(EPEC) O127:H6, and the commensal strainE. coliHB101. Nuclear and whole-cell protein extracts were prepared and were assayed by an electrophoretic mobility shift assay (EMSA) and by Western blotting, respectively. Cells were also processed for immunofluorescence to detect the subcellular localization of Stat1. The EMSA revealed inducible, but not constitutive, Stat1 activation upon IFN-γ treatment of both cell lines. The EMSA also showed that 6 h of EHEC O157:H7 infection, but not 30 min of EHEC O157:H7 infection, prevented subsequent Stat1 DNA binding induced by IFN-γ, whereas infection with EPEC did not. Immunoblotting showed that infection with EHEC, but not infection with EPEC, eliminated IFN-γ-induced Stat1 tyrosine phosphorylation in both dose- and time-dependent fashions and disrupted inducible protein expression of the Stat1-dependent gene interferon regulatory factor 1. Immunofluorescence revealed that EHEC infection did not prevent nuclear accumulation of Stat1 after IFN-γ treatment. Also, Stat1 tyrosine phosphorylation was suppressed by different EHEC isolates, including intimin-, type III secretion- and plasmid-deficient strains, but not by HB101 and heat-killed EHEC. These findings indicate the novel disruption of host cell signaling caused by EHEC infection but not by EPEC infection.
Shiga Toxin 1 Triggers a Ribotoxic Stress Response Leading to p38 and JNK Activation and Induction of Apoptosis in Intestinal Epithelial Cells
Authors: Smith Wendy E. , Kane Anne V. , Campbell Sausan T. , Acheson David W. K. , Cochran Brent H. , Thorpe Cheleste M.
Published: February 2003

Shiga toxins made by Shiga toxin-producing
Escherichia coli
(STEC) are associated with hemolytic uremic syndrome. Shiga toxins (Stxs) may access the host systemic circulation by absorption across the intestinal epithelium. The effects of Stxs on this cell layer are not completely understood, although animal models of STEC infection suggest that, in the gut, Stxs may participate in both immune activation and apoptosis. Stxs have one enzymatically active A subunit associated with five identical B subunits. The A subunit inactivates ribosomes by cleaving a specific adenine from the 28S rRNA. We have previously shown that Stxs can induce multiple C-X-C chemokines in intestinal epithelial cells in vitro, including interleukin-8 (IL-8), and that Stx-induced IL-8 expression is linked to induction of c-Jun mRNA and p38 mitogen-activated protein (MAP) kinase pathway activity. We now report Stx1 induction of both primary response genes
c-jun
and c-
fos
and activation of the stress-activated protein kinases, JNK/SAPK and p38, in the intestinal epithelial cell line HCT-8. By 1 h of exposure to Stx1, mRNAs for
c-jun
and c-
fos
are induced, and both JNK and p38 are activated; activation of both kinases persisted up to 24 h. Stx1 enzymatic activity was required for kinase activation; a catalytically defective mutant toxin did not activate either. Stx1 treatment of HCT-8 cells resulted in cell death that was associated with caspase 3 cleavage and internucleosomal DNA fragmentation; this cytotoxicity also required Stx1 enzymatic activity. Blocking Stx1-induced p38 and JNK activation with the inhibitor SB202190 prevented cell death and diminished Stx1-associated caspase 3 cleavage. In summary, these data link the Stx1-induced ribotoxic stress response with both chemokine expression and apoptosis in the intestinal epithelial cell line HCT-8 and suggest that blocking host cell MAP kinases may prevent these Stx-associated events.
MutantEscherichia coliHeat-Labile Toxin B Subunit That Separates Toxoid-Mediated Signaling and Immunomodulatory Action from Trafficking and Delivery Functions
Authors: Fraser Sylvia A. , de Haan Lolke , Hearn Arron R. , Bone Heather K. , Salmond Robert J. , Rivett A. Jennifer , Williams Neil A. , Hirst Timothy R.
Published: February 2003

The homopentameric B-subunit components ofEscherichia coliheat-labile enterotoxin (EtxB) and cholera toxin (CtxB) possess the capacity to enter mammalian cells and to activate cell-signaling events in leukocytes that modulate immune cell function. Both properties have been attributed to the ability of the B subunits to bind to GM1-ganglioside receptors, a ubiquitous glycosphingolipid found in the plasma membrane. Here we describe the properties of EtxB(H57S), a mutant B subunit with a His→Ser substitution at position 57. The mutant was found to be severely defective in inducing leukocyte signaling, as shown by failure to (i) trigger caspase 3-mediated CD8+-T-cell apoptosis, (ii) activate nuclear translocation of NF-κB in Jurkat T cells, (iii) induce a potent anti-B-subunit response in mice, or (iv) serve as a mucosal adjuvant. However, its GM1 binding, cellular uptake, and delivery functions remained intact. This was further validated by the finding that EtxB(H57S) was as effective as EtxB in delivering a conjugated model class I epitope into the major histocompatibility complex class I pathway of a dendritic cell line. These observations imply that GM1 binding alone is not sufficient to trigger the signaling events responsible for the potent immunomodulatory properties of EtxB. Moreover, they demonstrate that its signaling properties play no role in EtxB uptake and trafficking. Thus, EtxB(H57S) represents a novel tool for evaluating the complex cellular interactions and signaling events occurring after receptor interaction, as well as offering an alternative means of delivering attached peptides in the absence of the potent immunomodulatory signals induced by wild-type B subunits.
Cell Adhesion and Ca
2+
Signaling Activity in Stably Transfected
Trypanosoma cruzi
Epimastigotes Expressing the Metacyclic Stage-Specific Surface Molecule gp82
Authors: Manque Patricio M. , Neira Ivan , Atayde Vanessa D. , Cordero Esteban , Ferreira Alice T. , da Silveira José Franco , Ramirez Marcel , Yoshida Nobuko
Published: February 2003

Metacyclic trypomastigotes of
Trypanosoma cruzi
express a developmentally regulated 82-kDa surface glycoprotein (gp82) that has been implicated in host cell invasion. gp82-mediated interaction of metacyclic forms with target cells induces in both cells activation of the signal transduction pathways, leading to intracellular Ca
2+
mobilization, which is required for parasite internalization. Noninfective epimastigotes do not express detectable levels of gp82 and are unable to induce a Ca
2+
response. We stably transfected epimastigotes with a
T. cruzi
expression vector carrying the metacyclic stage gp82 cDNA. These transfectants produced a functional gp82, which bound to and triggered a Ca
2+
response in HeLa cells, in the same manner as the metacyclic trypomastigote gp82. Such properties were not found in epimastigotes transfected with the plasmid vector alone. Epimastigotes expressing gp82 on the surface adhered to HeLa cells but were not internalized. Treatment of gp82-expressing epimastigotes with forskolin, an activator of adenylyl cyclase that increases the metacyclic trypomastigote entry into target cells, did not promote parasite internalization. P175, an intracellular tyrosine phosphorylated protein, which appears to play a role in gp82-dependent signaling cascade in metacyclic forms, was undetectable in epimastigotes, either transfected or not with pTEX-gp82. Overall, our results indicate that gp82 is required but not sufficient for target cell invasion.
Interleukin-6-Deficient Mice Are Highly Susceptible toGiardia lambliaInfection but Exhibit Normal Intestinal Immunoglobulin A Responses against the Parasite
Authors: Bienz Marianne , Dai Wen Juan , Welle Monika , Gottstein Bruno , Müller Norbert
Published: February 2003

In the present study, interleukin-6 (IL-6)-deficient mice were infected withGiardia lambliaclone GS/M-83-H7. Murine IL-6 deficiency did not affect the synthesis of parasite-specific intestinal immunoglobulin A. However, in contrast to wild-type mice, IL-6-deficient animals were not able to control the acute phase of parasite infection. Reverse transcription-PCR-based quantitation of cytokine mRNA levels in peripheral lymph node cells exhibited a short-term up-regulation of IL-4 expression in IL-6-deficient mice that seemed to be associated with failure in controlling the parasite population. This observation suggests a further elucidation of IL-4-dependent, Th2-type regulatory processes regarding their potential to influence the course ofG. lambliainfection in the experimental murine host.
Nonhuman Primate Model for
Listeria monocytogenes
-Induced Stillbirths
Authors: Smith Mary Alice , Takeuchi Kazue , Brackett Robert E. , McClure Harold M. , Raybourne Richard B. , Williams Kristina M. , Babu Uma S. , Ware Glenn O. , Broderson J. Roger , Doyle Michael P.
Published: February 2003

Listeria monocytogenes
, isolated from outbreaks in either human or nonhuman primate populations, was administered orally at doses ranging from 10
6
to 10
10
CFU. Four of 10 treated animals delivered stillborn infants.
L. monocytogenes
was isolated from fetal tissue, and the pathology was consistent with
L. monocytogenes
infection as the cause of pregnancy loss. For all pregnancies resulting in stillbirths,
L. monocytogenes
was isolated from maternal feces, indicating that
L. monocytogenes
had survived and had probably colonized the gastrointestinal tract. Antibodies and antigen-specific lymphocyte proliferation against
Listeria
increased in animals that had stillbirths.
Bacterial [Cu,Zn]-Cofactored Superoxide Dismutase Protects Opsonized, EncapsulatedNeisseria meningitidisfrom Phagocytosis by Human Monocytes/Macrophages
Authors: Dunn Kate L. R. , Farrant Jayne L. , Langford Paul R. , Kroll J. Simon
Published: February 2003

Superoxide dismutase cofactored by copper and zinc ([Cu,Zn]-SOD) contributes to the protection of opsonized serogroup BNeisseria meningitidisagainst phagocytosis by human monocytes/macrophages, withsodCmutant organisms being endocytosed in significantly higher numbers than are wild-type organisms. The influence of [Cu,Zn]-SOD was found to be exerted at the stage of phagocytosis, rather than at earlier (modulating surface association) or later (intracellular killing) stages.
SOLITONIC ASPECTS OF q-FIELD THEORIES
Authors: FINKELSTEIN R. J.
Published: February 2003

We have examined the deformation of a generic non-Abelian gauge theory obtained by replacing its Lie group by the corresponding quantum group. This deformed gauge theory has more degrees of freedom than the theory from which it is derived. By going over from point particles in the standard theory to solitonic particles in the deformed theory, it is proposed that we interpret the new degrees of freedom as being descriptive of the non-locality of the deformed theory. It also turns out that the original Lie algebra gets replaced by two dual algebras, one of which lies close to and approaches the original Lie algebra in a correspondence limit, while the second algebra is new and disappears in this same correspondence limit. The exotic field particles associated with the second algebra can be interpreted as quark-like constituents of the solitons, which are themselves described as point particles in the first algebra. These ideas are explored for q-deformed SU(2) and GL q(3).
TWO-SCALE HOMOGENIZATION STUDY OF A REYNOLDS-ROD ELASTOHYDRODYNAMIC MODEL
Authors: BAYADA G. , CID B. , VÁZQUEZ C.
Published: February 2003

In this paper, the existence of solution for a coupled system of variational inequalities with highly oscillating coefficients modelling a micro-elastohydrodynamic lubrication problem is stated. Moreover, by means of two-scale convergence techniques, the limit coupled models when the frequency of oscillation tends to zero are established for different amplitude-frequency rates. The effect of roughness appears to be limited to one of the coupled nonlinear equations, either the elastic one or the hydrodynamic one. Finally, some numerical examples to illustrate both the qualitative behavior of the solution and the theoretical convergence results are presented.
Treatment With Statins After Induction of Focal Ischemia in Rats Reduces the Extent of Brain Damage
Authors: Sironi Luigi , Cimino Mauro , Guerrini Uliano , Calvio Anna Maria , Lodetti Barbara , Asdente Maria , Balduini Walter , Paoletti Rodolfo , Tremoli Elena
Published: February 2003

Objective—

In the present study, MRI has been used to investigate therapeutic intervention with statins in a model of permanent focal cerebral ischemia in rat.

Methods and Results—

Brain ischemia was induced in rats by the permanent occlusion of middle cerebral artery (MCAO) and the brain infarct size followed up in alive animals 2, 24, and 48 hours after MCAO, using the trace of apparent diffusion coefficient [Tr(D)] maps and T2-weighted images. In vehicle-treated rats, the infarct volumes increased by 38.5% and 89% after 24 and 48 hours, respectively, compared with the damage detected at 2 hours after MCAO. Treatment with simvastatin (20 mg/kg) after MCAO prevented the increase in brain infarct volume occurring at 24 hours and induced a 46.6% reduction after 48 hours. This effect was similar to that observed when simvastatin was administered before the induction of focal ischemia. T2W-MRI images confirmed these findings. The neuroprotective effects of simvastatin were paralleled by an increase in endothelial NO synthase immunoreactivity, detectable in the brain of simvastatin-treated rats.

Conclusions—

Statins, in addition to their preventive effect on cerebral ischemia, exert a neuroprotective role in the attenuation of brain damage after acute stroke.
Short-Term Triglyceride Lowering With Fenofibrate Improves Vasodilator Function in Subjects With Hypertriglyceridemia
Authors: Capell Warren H. , DeSouza Christopher A. , Poirier Paul , Bell Melanie L. , Stauffer Brian L. , Weil Kathleen M. , Hernandez Teri L. , Eckel Robert H.
Published: February 2003

Objective—

The objective of this study was to investigate the effects of lowering plasma triglycerides (TGs) on endothelial function and gain insight into the role played by free fatty acids (FFAs) in hypertriglyceridemia-associated vascular dysfunction.

Methods and Results—

Eleven hypertriglyceridemic subjects without coronary artery disease, diabetes, elevated low-density lipoprotein cholesterol, tobacco use, or hypertension were studied using a randomized, double-blinded, crossover design (fenofibrate and placebo, 14 days). After each regimen, forearm blood flow was assessed by plethysmography in response to arterial acetylcholine, nitroprusside, and verapamil infusion. Hourly plasma TGs, FFA, glucose, and insulin were measured during a 24-hour feeding cycle to characterize the metabolic environment. Changes in plasma FFA after intravenous heparin were used to estimate typical FFA accumulation in the luminal endothelial microenvironment. Fenofibrate lowered plasma TG (
P
<0.001), total cholesterol (
P
<0.01), and apolipoprotein B (
P
<0.01) without altering high-density lipoprotein or low-density lipoprotein cholesterol concentrations. Forearm blood flow in response to acetylcholine (
P
<0.0001), nitroprusside (
P
<0.001), and verapamil (
P
<0.0001) improved after fenofibrate. Fenofibrate lowered 24-hour (
P
<0.0001) and post-heparin (
P
<0.001) TG and tended to lower 24-hour (
P
=0.054) and post-heparin (
P
=0.028) FFA.

Conclusions—

Vascular smooth muscle function significantly improves after lowering plasma TG without changes in confounding lipoproteins or insulin resistance. The data raise additional questions regarding the role of FFA in hypertriglyceridemia-associated vascular dysfunction.
Association Between Insulin Resistance and Carotid Arteriosclerosis in Subjects With Normal Fasting Glucose and Normal Glucose Tolerance
Authors: Ishizaka Nobukazu , Ishizaka Yuko , Takahashi Eiko , Unuma Tadao , Tooda Ei-ichi , Nagai Ryozo , Togo Masako , Tsukamoto Kazuhisa , Hashimoto Hideki , Yamakado Minoru
Published: February 2003

Objective—

We examined the possible association between insulin resistance and carotid arteriosclerosis in subjects who had both normal fasting glucose and normal glucose tolerance after intake of a glucose load.

Methods and Results—

Our subjects were individuals who underwent general health screening at our institute, which included carotid ultrasound and oral glucose tolerance testing. Of the 1238 subjects enrolled in our study, 738 (60%) were classified as normal, defined as a normal fasting glucose level and normal glucose tolerance, and 334 (27%) and 166 (13%) were classified as borderline and diabetic, respectively, according to the criteria of the Japan Diabetes Society. The homeostasis model assessment of insulin resistance (HOMA-IR) was used as the index to measure insulin resistance. In normal-type subjects, univariate analysis showed that insulin resistance, but not insulin secretion, was associated with the presence of carotid plaque. Multivariate analysis showed that HOMA-IR was positively associated with carotid plaque in normal-type subjects, with an odds ratio of 1.19 (95% confidence interval, 1.00 to 1.41;
P
<0.05).

Conclusions—

These data suggest the possibility that the presence of higher insulin resistance could be a risk factor for carotid arteriosclerosis in subjects with normal fasting glucose and normal glucose tolerance.
A Functional Polymorphism in a STAT5B Site of the Human
PPARγ3
Gene Promoter Affects Height and Lipid Metabolism in a French Population
Authors: Meirhaeghe Aline , Fajas Lluis , Gouilleux Fabrice , Cottel Dominique , Helbecque Nicole , Auwerx Johan , Amouyel Philippe
Published: February 2003

Objective—

The peroxisome proliferator-activated receptor-γ (PPARγ) plays a role in adipocyte differentiation and insulin sensitization. It has been shown that genetic variation in the
PPARγ
gene alters body weight control, lipid and insulin homeostasis, and the susceptibility to type 2 diabetes. Four PPARγ isoforms are generated by alternative splicing and promoter usage. PPARγ3 is only expressed in adipose tissue, colon, and macrophages and therefore seems to be a good candidate gene for metabolic and cardiovascular-associated diseases. In the present study, we looked for genetic variation in the
PPARγ3
promoter.

Methods and Results—

The proximal
PPARγ3
promoter was sequenced in 20 individuals. We detected a C/G polymorphism at position −681 from exon A2. Interestingly, it was located in a signal transducer and activator of transcription 5B (STAT5B) binding consensus site. In a French population (n=836), the −681G allele was associated with increased height and plasma low-density lipoprotein cholesterol concentrations. In vitro, we showed that the −681G allele completely abolished the binding of STAT5B to the cognate promoter element as well as the transactivation of the
PPARγ3
promoter by the growth hormone/STAT5B pathway.

Conclusions—

Our results suggest that PPARγ3 may regulate the control of height and lipid homeostasis via the STAT5B pathway.
Endothelial Dysfunction
Authors: Bonetti Piero O. , Lerman Lilach O. , Lerman Amir
Published: February 2003

Endothelial dysfunction is a systemic disorder and a key variable in the pathogenesis of atherosclerosis and its complications. Current evidence suggests that endothelial status is not determined solely by the individual risk factor burden but rather, may be regarded as an integrated index of all atherogenic and atheroprotective factors present in an individual, including known as well as yet-unknown variables and genetic predisposition. Endothelial dysfunction reflects a vascular phenotype prone to atherogenesis and may therefore serve as a marker of the inherent atherosclerotic risk in an individual. In line with this hypothesis, dysfunction of either the coronary or peripheral vascular endothelium was shown to constitute an independent predictor of cardiovascular events, providing valuable prognostic information additional to that derived from conventional risk factor assessment. Interventions like risk factor modification and treatment with various drugs, including statins and angiotensin-converting enzyme inhibitors, may improve endothelial function and thereby, potentially prognosis. Hence, given its reversibility and granted the availability of a diagnostic tool to identify patients at risk and to control the efficacy of therapy in clinical practice, endothelial dysfunction may be an attractive primary target in the effort to optimize individualized therapeutic strategies to reduce cardiovascular morbidity and mortality.
Expansive Remodeling Is a Response of the Plaque-Related Vessel Wall in Aortic Roots of ApoE-Deficient Mice
Authors: Bentzon Jacob F. , Pasterkamp Gerard , Falk Erling
Published: February 2003

Objective—

In the present study, we (1) evaluated the apolipoprotein E–deficient (apoE
−/−
) mouse aortic root as a model for expansive remodeling in atherosclerosis and (2) examined whether remodeling at this site was due to dilation of the vessel wall beneath or flanking the plaque.

Methods and Results—

Plaque area and length of the internal elastic lamina (IEL) were measured in aortic roots of apoE
−/−
mice at 11 weeks, 6 months, and 13 months of age. Expansive remodeling, indicated by IEL lengthening exceeding that of normal growth in wild-type C57BL/6 mice, was evident at 6 months of age and showed overcompensation (luminal enlargement) by 13 months of age. When the left coronary (LC), right coronary (RC), and noncoronary (NC) sinuses of the aortic root were looked at individually, remodeling was located to the LC at 6 months of age and to the LC and RC at 13 months of age. The remodeling response was closely related to local plaque area but unrelated to plaque formation in flanking sinuses.

Conclusions—

The aortic root of the apoE
−/−
mouse features a consistent remodeling response. In this model, expansive remodeling was a strictly local response of the plaque-related vessel wall.
Fluvastatin Prevents Renal Dysfunction and Vascular NO Deficit in Apolipoprotein E-Deficient Mice
Authors: Gervais Marianne , Pons Sandrine , Nicoletti Antonino , Cosson Claudine , Giudicelli Jean-François , Richer Christine
Published: February 2003

Objective—

The objective of this study was to investigate the effects of fluvastatin on atherosclerosis, systemic and regional hemodynamics, and vascular reactivity in apolipoprotein E-deficient (ApoE
−/−
) mice.

Methods and Results—

Hemodynamics (fluospheres) and vasomotor responses of thoracic aorta and carotid artery were evaluated in male wild-type (WT) and untreated (ApoE
−/−
Control) or fluvastatin-treated (50 mg/kg per day for 20 weeks) ApoE
−/−
mice, all fed a Western-type diet. Plasma cholesterol and aortic root atherosclerotic lesions (ALs) were greater in ApoE
−/−
Control mice (19±1 mmol/L and 63 0176±38 785 μm
2
, respectively) than in WT mice (2±1 mmol/L and 1±1 μm
2
, respectively,
P
<0.01). Fluvastatin significantly decreased plasma cholesterol (−53%) but failed to limit ALs. Renal blood flow was significantly reduced in ApoE
−/−
Control versus WT (−25%,
P
<0.05) mice. This reduction was prevented by fluvastatin. Aortic and carotid endothelium-dependent relaxations to acetylcholine were not altered in ApoE
−/−
Control versus WT mice. In carotid arteries from WT mice, these responses were abolished after nitro-
l
-arginine (L-NA), whereas those from ApoE
−/−
Control were only partially inhibited after L-NA but fully abolished after L-NA+diclofenac. Thus, in carotid arteries from ApoE
−/−
mice, vasodilating prostanoids compensate the deficit in NO availability. Fluvastatin prevented this carotid NO deficit.

Conclusions—

In ApoE
−/−
mice, chronic fluvastatin treatment preserved renal perfusion and vascular NO availability independently from atherosclerotic lesion prevention.
Mast Cell Chymase Induces Smooth Muscle Cell Apoptosis by a Mechanism Involving Fibronectin Degradation and Disruption of Focal Adhesions
Authors: Leskinen Markus J. , Lindstedt Ken A. , Wang Yenfeng , Kovanen Petri T.
Published: February 2003

Objective—

Chymase released from activated mast cells has been shown to induce apoptosis of vascular smooth muscle cells (SMCs) in vitro. The proteolytic activity of chymase is essential for the proapoptotic effect, but the mechanism of chymase-induced apoptosis has remained unknown.

Methods and Results—

Here we show by means of FACS analysis, immunohistochemistry, and Western blotting that mast cell–derived chymase induces SMC apoptosis by a mechanism involving degradation of an extracellular matrix component, fibronectin (FN), with subsequent disruption of focal adhesions. The FN degradation products induced SMC apoptosis of similar magnitude and with similar changes in outside-in signaling, as did chymase. Sodium orthovanadate, an inhibitor of tyrosine phosphatases, inhibited the chymase-induced SMC apoptosis. Focal adhesion kinase (FAK), one of the key mediators of integrin–extracellular matrix interactions and cell survival, was rapidly degraded in the presence of chymase or FN degradation products. Loss of phosphorylated FAK (p-FAK) resulted in a rapid dephosphorylation of the p-FAK–dependent downstream mediator Akt.

Conclusions—

The results suggest that chymase-secreting mast cells can mediate apoptosis of neighboring SMCs through a mechanism involving degradation of pericellular FN and disruption of the p-FAK–dependent cell-survival signaling cascade.