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1

Vaca Muerta mesosiderite strewnfield  

NASA Astrophysics Data System (ADS)

A field investigation is presented of the strewnfield of the mesosiderite Vaca Muerta, originally found in 1861. The area, 11.5 km long, 2.1 km wide, is located about 60 km southeast of Taltal, Chile, in the Atacama Desert. It has yielded 80 meteorites with a total mass exceeding 3782 kg. Most fragments were found in an undisturbed state, but some had been broken by prospectors. The present studies, in connection with historical records, indicate that the original mass of Vaca Muerta exceeded 6 metric tons. One impact feature, somewhat modified by man, consists of a 10.5-m diameter, 1.7-m deep hole, without an uplifted rim. Small masses were scattered up to 85 m from the hole.

Pedersen, Holger; Canut de Bon, Claudio; Lindgren, Harri

1992-06-01

2

VacA, the vacuolating cytotoxin of Helicobacter pylori, binds to multimerin 1 on human platelets.  

PubMed

Platelets were activated under the infection with H. pylori in human and mice. We investigated the role of VacA, an exotoxin released by H. pylori in this context. Acid-activated VacA, but not heated VacA, induced platelet CD62P expression. However, VacA reacted with none of the alleged VacA receptors present on platelet membranes. We therefore analyzed VacA associated proteins obtained through VacA affinity chromatography, using MALDI-TOF-MS. Multimerin1 was detected in two consecutive experiments, as the binding protein for VacA. Plasmon resonance confirmed their binding, and dot blot analysis revealed that the peptide sequence AA 321-340 of multimerin 1 is the binding site for VacA. In conclusion, we propose a new interaction between multimerin1 and VacA , which may give another insight into H. pylori-induced platelet activations under H. pylori infection. PMID:24219705

Satoh, Kaneo; Hirayama, Toshiya; Takano, Katsuhiro; Suzuki-Inoue, Katsue; Sato, Tadashi; Ohta, Masato; Nakagomi, Junko; Ozaki, Yukio

2013-01-01

3

Expanding Allelic Diversity of Helicobacter pylori vacA  

Microsoft Academic Search

The diversity of the gene encoding the vacuolating cytotoxin (vacA )o fHelicobacter pylori was analyzed in 98 isolates obtained from different geographic locations. The studies focused on variation in the previously defined s and m regions of vacA, as determined by PCR and direct sequencing. Phylogenetic analysis revealed the existence of four distinct types of s-region alleles: aside from the

LEEN-JAN VAN DOORN; C EU FIGUEIREDO; RICARDO SANNA; SALVADOR PENA; PETER MIDOLO; ENDERS K. W. NG; JOHN C. ATHERTON; MARTIN J. BLASER; WIM G. V. QUINT

1998-01-01

4

Isotopically Heavy and Heterogeneous C in Graphite of the Vaca Muerta Mesosiderite  

NASA Astrophysics Data System (ADS)

We report on C-bearing Fe-Ni metal objects of Vaca Muerta and C isotopic ratios of graphite associated with the metal. Our results severely constrain the conditions prevailing during formation of the Vaca Muerta mesosiderite.

Maruoka, T.; Varela, M. E.; Kurat, G.; Zinner, E.

2006-03-01

5

Feasibility Design Report. Bauta-Toa Vaca Tunnel.  

National Technical Information Service (NTIS)

The report summarizes feasibility design studies prepared by the Bureau of Reclamation (BuRec) for the Puerto Rico Water Resources Authority (PRWRA) for Bauta-Toa Vaca Tunnel, a key feature for initial diversion of water from northward flowing streams to ...

1970-01-01

6

Helicobacter pylori VacA, a paradigm for toxin multifunctionality  

Microsoft Academic Search

Bacterial protein toxins alter eukaryotic cellular processes and enable bacteria to successfully colonize their hosts. In recent years, there has been increased recognition that many bacterial toxins are multifunctional proteins that can have pleiotropic effects on mammalian cells and tissues. In this review, we examine a multifunctional toxin (VacA) that is produced by the bacterium Helicobacter pylori. The actions of

Steven R. Blanke

2005-01-01

7

Significance of Helicobacter pylori vacA intermediate region genotyping-a Bulgarian study.  

PubMed

The significance of the intermediate (i) region of the Helicobacter pylori vacA gene as a virulence factor associated with the severity of gastric disease is still disputable. The aim of the present study was to evaluate the prevalence and significance of vacA i alleles alone or in combination with other vacA alleles in symptomatic Bulgarian patients and to find out possible associations between vacA i genotype and patients' disease, age, sex, and other H. pylori virulence factors. Unlike vacA s1 and m1, vacA i1 prevalence was significantly higher (75.0%) in strains from peptic ulcer patients than in strains from nonulcer patients with gastric diseases (58.6%) (P = 0.022). Less virulent vacA s1 i2 m2 strains were more prevalent in females (P = 0.03), and cagA(+) was associated with vacA i1, s1, m1, and their combinations. In conclusion, vacA i status is a better predictor for the strain virulence than other vacA alleles. PMID:22951332

Yordanov, Daniel; Boyanova, Lyudmila; Markovska, Rumyana; Gergova, Galina; Mitov, Ivan

2012-11-01

8

Identification of the Helicobacter pylori VacA Toxin Domain Active in the Cell Cytosol  

Microsoft Academic Search

Cells exposed to Helicobacter pylori toxin VacA develop large vacuoles which originate from massive swelling of membranous compartments at late stages of the endocytic pathway. When expressed in the cytosol, VacA induces vacuolization as it does when added from outside. This and other evidence indicate that VacA is a toxin capable of entering the cell cytosol, where it displays its

MARINA DE BERNARD; DANIELA BURRONI; EMANUELE PAPINI; RINO RAPPUOLI; JOHN TELFORD; CESARE MONTECUCCO

1998-01-01

9

The Acid Activation of Helicobacter pyloriToxin VacA: Structural and Membrane Binding Studies  

Microsoft Academic Search

The cell vacuolating activity of the protein toxin VacA, released byHelicobacter pylori,is strongly increasedin vitroby exposure to acidic pH followed by neutralization. This short acid exposure does not increase significantly the binding of VacA to cell or to lipid membranes. However, membrane photolabeling with photoactivatable radioactive phospholipids and ANS binding studies show that VacA transiently exposed to pH equal or

Maurizio Molinari; Carmela Galli; Marina de Bernard; Nathalie Norais; Jean-Marie Ruysschaert; Rino Rappuoli; Cesare Montecucco

1998-01-01

10

Heterogeneity in Levels of Vacuolating Cytotoxin Gene (vacA) Transcription among Helicobacter pylori Strains  

Microsoft Academic Search

Broth culture supernatants from Tox1 Helicobacter pylori strains induce vacuolation of HeLa cells in vitro and contain VacA in concentrations that are higher than those found in supernatants from Tox2 H. pylori strains. To investigate the basis for this phenomenon, we analyzed the transcription of the vacuolating cytotoxin gene (vacA) in eight Tox1 strains (each with a type s1\\/m1 vacA

M. H. FORSYTH; J. C. ATHERTON; M. J. BLASER

1998-01-01

11

Evaluation of Helicobacter pylori vacA genotype in Japanese patients with gastric cancer  

Microsoft Academic Search

AIM: To examine the vacA genotypes of Helicobacter pylori strains in Japan and to define whether any specific genotype was associated with gastric cancer. METHODS: The allelic variation of vacA gene was studied using a recently introduced polymerase chain reaction based vacA genotyping system. RESULTS: 80 H pylori strains were isolated from gastric biopsies of 40 patients with gastric cancer

T. Shimoyama; T. Yoshimura; T. Mikami; S. Fukuda; J. E. Crabtree; A. Munakata

1998-01-01

12

Molecular Evolution of the Helicobacter pylori Vacuolating Toxin Gene vacA ? †  

PubMed Central

Helicobacter pylori is a genetically diverse organism that is adapted for colonization of the human stomach. All strains contain a gene encoding a secreted, pore-forming toxin known as VacA. Genetic variation at this locus could be under strong selection as H. pylori adapts to the host immune response, colonizes new human hosts, or inhabits different host environments. Here, we analyze the molecular evolution of VacA. Phylogenetic reconstructions indicate the subdivision of VacA sequences into three main groups with distinct geographic distributions. Divergence of the three groups is principally due to positively selected sequence changes in the p55 domain, a central region required for binding of the toxin to host cells. Divergent amino acids map to surface-exposed sites in the p55 crystal structure. Comparative phylogenetic analyses of vacA sequences and housekeeping gene sequences indicate that vacA does not share the same evolutionary history as the core genome. Further, rooting the VacA tree with outgroup sequences from the close relative Helicobacter acinonychis reveals that the ancestry of VacA is different from the African origin that typifies the core genome. Finally, sequence analyses of the virulence determinant CagA reveal three main groups strikingly similar to the three groups of VacA sequences. Taken together, these results indicate that positive selection has shaped the phylogenetic structure of VacA and CagA, and each of these virulence determinants has evolved separately from the core genome.

Gangwer, Kelly A.; Shaffer, Carrie L.; Suerbaum, Sebastian; Lacy, D. Borden; Cover, Timothy L.; Bordenstein, Seth R.

2010-01-01

13

Acid-induced Dissociation of VacA, the Helicobacter pylori Vacuolating Cytotoxin, Reveals Its Pattern of Assembly  

Microsoft Academic Search

In this study, we describe the ultrastructural changes associated with acid activation of Helicobacter pylori vacuolating cytotoxin (VacA). Purified VacA molecules imaged by deep-etch electron microscopy form z 30-nm hexagonal \\

Phyllis I. Hanson; John E. Heuser

1997-01-01

14

Diverse eucritic pebbles in the Vaca Muerta mesosiderite  

NASA Technical Reports Server (NTRS)

Seven 5-cm basaltic pebbles from the Vaca Muerta mesosiderite were studied by neutron activation and electron microprobe analysis, and three additional pebbles were studied petrographically. The cumulate pebbles had low REE concentrations and high Eu/Sm ratios, indicating the absence of intercumulus liquid. Siderophile interelement ratios were similar to those found in Vaca Muerta metal except for anomalously low Ir concentrations. The presence of 20 percent impact-melt breccias among the pebbles and 35-40 percent melt breccias among the mesosiderite whole-rocks suggests that the mesosiderites were more extensively impact melted than the howardites. Three alternative models to explain this greater proportion of impact-melted material among the mesosiderites are proposed.

Rubin, Alan E.; Jerde, Eric A.

1987-01-01

15

Diverse eucritic pebbles in the Vaca Muerta mesosiderite  

NASA Astrophysics Data System (ADS)

Seven 5-cm basaltic pebbles from the Vaca Muerta mesosiderite were studied by neutron activation and electron microprobe analysis, and three additional pebbles were studied petrographically. The cumulate pebbles had low REE concentrations and high Eu/Sm ratios, indicating the absence of intercumulus liquid. Siderophile interelement ratios were similar to those found in Vaca Muerta metal except for anomalously low Ir concentrations. The presence of 20 percent impact-melt breccias among the pebbles and 35-40 percent melt breccias among the mesosiderite whole-rocks suggests that the mesosiderites were more extensively impact melted than the howardites. Three alternative models to explain this greater proportion of impact-melted material among the mesosiderites are proposed.

Rubin, A. E.; Jerde, E. A.

1987-06-01

16

Structural Analysis of the Oligomeric States of Helicobacter pylori VacA Toxin  

PubMed Central

Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach and contributes to peptic ulceration and gastric adenocarcinoma. H. pylori secretes a pore-forming exotoxin known as vacuolating toxin (VacA). VacA contains two distinct domains, designated p33 and p55, and assembles into large “snowflake”-shaped oligomers. Thus far, no structural data are available for the p33 domain, which is essential for membrane channel formation. Using single-particle electron microscopy and the random conical tilt approach, we have determined the three-dimensional structures of six VacA oligomeric conformations at ~15-Å resolution. The p55 domain, composed primarily of ?-helical structures, localizes to the peripheral arms, while the p33 domain consists of two globular densities that localize within the center of the complexes. By fitting the VacA p55 crystal structure into the electron microscopy densities, we have mapped inter-VacA interactions that support oligomerization. In addition, we have examined VacA variants/mutants that differ from wild-type (WT) VacA in toxin activity and/or oligomeric structural features. Oligomers formed by VacA?6–27, a mutant that fails to form membrane channels, lack an organized p33 central core. Mixed oligomers containing both WT and VacA?6–27 subunits also lack an organized core. Oligomers formed by a VacA s2m1 chimera (which lacks cell-vacuolating activity) and VacA?301–328 (which retains vacuolating activity) each contain p33 central cores similar to those of WT oligomers. By providing the most detailed view of the VacA structure to date, these data offer new insights into the toxin's channel-forming component and the intermolecular interactions that underlie oligomeric assembly.

Chambers, Melissa G.; Pyburn, Tasia M.; Gonzalez-Rivera, Christian; Collier, Scott E.; Eli, Ilyas; Yip, Calvin K.; Takizawa, Yoshimasa; Lacy, D. Borden; Cover, Timothy L.; Ohi, Melanie D.

2013-01-01

17

Lack of a relationship between Lewis antigen expression and cagA, CagA, vacA and VacA status of Irish Helicobacter pylori isolates  

Microsoft Academic Search

The cagA gene, vacA gene, CagA (cytotoxin-associated gene A product) and VacA (vacuolating cytotoxin) status of a collection of Helicobacter pylori isolates from the geographically distinct Irish population was determined, the potential association of these traits with Lewis (Le) antigen expression was assessed, and the relationship between these bacterial properties and the pathology associated with H. pylori infection was evaluated.

David G Marshall; Sean O Hynes; David C Coleman; Colm A O'Morain; Cyril J Smyth; Anthony P Moran

1999-01-01

18

Helicobacter pylori VacA Subdomain Required for Intracellular Toxin Activity and Assembly of Functional Oligomeric Complexes?  

PubMed Central

Helicobacter pylori VacA is a secreted pore-forming toxin that is comprised of two domains, designated p33 and p55. The p55 domain has an important role in the binding of VacA to eukaryotic cell surfaces. A total of 111 residues at the amino terminus of p55 (residues 312 to 422) are essential for the intracellular activity of VacA, which suggests that this region may constitute a subdomain with an activity distinct from cell binding. To investigate the properties of this subdomain, a small deletion mutation (targeting aspartic acid 346 and glycine 347) was introduced into the H. pylori chromosomal vacA gene. Similar to wild-type VacA, the VacA ?346-347 mutant protein was proteolytically processed, secreted, and bound to eukaryotic cells. However, VacA ?346-347 did not cause cell vacuolation or membrane depolarization, and it was impaired in the ability to assemble into large water-soluble oligomeric structures. Interestingly, VacA ?346-347 was able to physically interact with wild-type VacA to form mixed oligomeric complexes, and VacA ?346-347 inhibited wild-type vacuolating activity in a dominant-negative manner. These data indicate that the assembly of functional oligomeric VacA complexes is dependent on specific sequences, including amino acids 346 and 347, within the p55 amino-terminal subdomain.

Ivie, Susan E.; McClain, Mark S.; Torres, Victor J.; Algood, Holly M. Scott; Lacy, D. Borden; Yang, Rong; Blanke, Steven R.; Cover, Timothy L.

2008-01-01

19

Helicobacter pylori VacA subdomain required for intracellular toxin activity and assembly of functional oligomeric complexes.  

PubMed

Helicobacter pylori VacA is a secreted pore-forming toxin that is comprised of two domains, designated p33 and p55. The p55 domain has an important role in the binding of VacA to eukaryotic cell surfaces. A total of 111 residues at the amino terminus of p55 (residues 312 to 422) are essential for the intracellular activity of VacA, which suggests that this region may constitute a subdomain with an activity distinct from cell binding. To investigate the properties of this subdomain, a small deletion mutation (targeting aspartic acid 346 and glycine 347) was introduced into the H. pylori chromosomal vacA gene. Similar to wild-type VacA, the VacA Delta346-347 mutant protein was proteolytically processed, secreted, and bound to eukaryotic cells. However, VacA Delta346-347 did not cause cell vacuolation or membrane depolarization, and it was impaired in the ability to assemble into large water-soluble oligomeric structures. Interestingly, VacA Delta346-347 was able to physically interact with wild-type VacA to form mixed oligomeric complexes, and VacA Delta346-347 inhibited wild-type vacuolating activity in a dominant-negative manner. These data indicate that the assembly of functional oligomeric VacA complexes is dependent on specific sequences, including amino acids 346 and 347, within the p55 amino-terminal subdomain. PMID:18443094

Ivie, Susan E; McClain, Mark S; Torres, Victor J; Algood, Holly M Scott; Lacy, D Borden; Yang, Rong; Blanke, Steven R; Cover, Timothy L

2008-07-01

20

Sphingomyelin Functions as a Novel Receptor for Helicobacter pylori VacA  

PubMed Central

The vacuolating cytotoxin (VacA) of the gastric pathogen Helicobacter pylori binds and enters epithelial cells, ultimately resulting in cellular vacuolation. Several host factors have been reported to be important for VacA function, but none of these have been demonstrated to be essential for toxin binding to the plasma membrane. Thus, the identity of cell surface receptors critical for both toxin binding and function has remained elusive. Here, we identify VacA as the first bacterial virulence factor that exploits the important plasma membrane sphingolipid, sphingomyelin (SM), as a cellular receptor. Depletion of plasma membrane SM with sphingomyelinase inhibited VacA-mediated vacuolation and significantly reduced the sensitivity of HeLa cells, as well as several other cell lines, to VacA. Further analysis revealed that SM is critical for VacA interactions with the plasma membrane. Restoring plasma membrane SM in cells previously depleted of SM was sufficient to rescue both toxin vacuolation activity and plasma membrane binding. VacA association with detergent-resistant membranes was inhibited in cells pretreated with SMase C, indicating the importance of SM for VacA association with lipid raft microdomains. Finally, VacA bound to SM in an in vitro ELISA assay in a manner competitively inhibited by lysenin, a known SM-binding protein. Our results suggest a model where VacA may exploit the capacity of SM to preferentially partition into lipid rafts in order to access the raft-associated cellular machinery previously shown to be required for toxin entry into host cells.

Kostolansky, Sean S.; Ballivian, Roberto A.; Eichberg, Joseph; Blanke, Steven R.

2008-01-01

21

Diversity of Helicobacter pylori vacA and cagA Genes and Relationship to VacA and CagA Protein Expression, Cytotoxin Production, and Associated Diseases  

Microsoft Academic Search

The vacuolating cytotoxin and the cytotoxin-associated protein, encoded by vacA and cagA, respectively, are important virulence determinants of Helicobacter pylori. Sixty-five H. pylori strains were isolated from dyspeptic patients (19 with peptic ulcer disease, 43 with chronic gastritis, and 3 with gastric cancer) and studied for differences in the vacA and cagA genes and their relationship to VacA and CagA

JOCHEN RUDI; CHRISTOF KOLB; MATTHIAS MAIWALD; DIRK KUCK; ANDREAS SIEG; PETER R. GALLE; WOLFGANG STREMMEL

1998-01-01

22

Action site and cellular effects of cytotoxin VacA produced by Helicobacter pylori  

Microsoft Academic Search

Cells treated with the VacA toxin fromHelicobacter pylori develop large membrane-bound vacuoles that originate from the late endocytotic pathway. Using different experimental approaches,\\u000a we showed that VacA can induce vacuoles by acting within the cell cytosol. Moreover, separation of VacA-induced vacuoles at\\u000a an early stage of formation, using a novel isopycnic density ultracentrifugation method, allowed us to show that they

E. Papini; B. Satin; M. de Bernard; M. Molinari; B. Aricò; C. Galli; J. R. Telford; R. Rappuoli; C. Montecucco

1998-01-01

23

Selective Inhibition of Ii-dependent Antigen Presentation by Helicobacter pylori Toxin VacA  

Microsoft Academic Search

Summary A major virulence factor in the stomach chronic infection by Helicobacter pylori is a protein toxin (VacA), which alters cell membrane trafficking of late endosomal\\/prelysosomal compartments. Its role in the chronic infection established by H. pylori is unknown. To test the possibility that VacA alters antigen processing taking place in prelysosomal compartments, we have used the well-established model of

Maurizio Molinari; Mariolina Salio; Carmela Galli; Nathalie Norais; Rino Rappuoli; Antonio Lanzavecchia; Cesare Montecucco

24

Association of Helicobacter pylori Vacuolating Toxin (VacA) with Lipid Rafts  

Microsoft Academic Search

A variety of extracellular ligands and pathogens inter- act with raft domains in the plasma membrane of eu- karyotic cells. In this study, we examined the role of lipid rafts and raft-associated glycosylphosphatidyli- nositol (GPI)-anchored proteins in the process by which Helicobacter pylori vacuolating toxin (VacA) intoxicates cells. We first investigated whether GPI-anchored pro- teins are required for VacA toxicity

Wayne Schraw; Yi Li; Mark S. McClain; F. Gisou van der Goot

2002-01-01

25

Geographic distribution of vacA allelic types of Helicobacter pylori  

Microsoft Academic Search

Background & Aims: Distinct allelic types of Helicobacter pylori vacA have been defined. The geographic distribution of vacA alleles and cagA was assessed in this study. Methods: A total of 735 cultures from patients in 24 countries were analyzed by polymerase chain reaction and reverse hybridization on a line probe assay (LiPA). Results: In 124 (16.9%) of the 735 cultures,

Céu Figueiredo; Francis Mégraud; Salvador Pena; Peter Midolo; Dulciene Maria De Magalhães Queiroz; Fátima Carneiro; Bart Vanderborght; Maria Da Glória F. Pegado; Ricardo Sanna; Wink De Boer; Peter M. Schneeberger; Pelayo Correa; Enders K. W. Ng; John Atherton; Martin J. Blaser; Wim G. V. Quint

1999-01-01

26

Helicobacter pylori VacA induces programmed necrosis in gastric epithelial cells.  

PubMed

Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach and contributes to the development of peptic ulcer disease and gastric cancer. The secreted pore-forming toxin VacA is one of the major virulence factors of H. pylori. In the current study, we show that AZ-521 human gastric epithelial cells are highly susceptible to VacA-induced cell death. Wild-type VacA causes death of these cells, whereas mutant VacA proteins defective in membrane channel formation do not. Incubation of AZ-521 cells with wild-type VacA results in cell swelling, poly(ADP-ribose) polymerase (PARP) activation, decreased intracellular ATP concentration, and lactate dehydrogenase (LDH) release. VacA-induced death of these cells is a caspase-independent process that results in cellular release of histone-binding protein high mobility group box 1 (HMGB1), a proinflammatory protein. These features are consistent with the occurrence of cell death through a programmed necrosis pathway and suggest that VacA can be included among the growing number of bacterial pore-forming toxins that induce cell death through programmed necrosis. We propose that VacA augments H. pylori-induced mucosal inflammation in the human stomach by causing programmed necrosis of gastric epithelial cells and subsequent release of proinflammatory proteins and may thereby contribute to the pathogenesis of gastric cancer and peptic ulceration. PMID:21482684

Radin, Jana N; González-Rivera, Christian; Ivie, Susan E; McClain, Mark S; Cover, Timothy L

2011-07-01

27

Gastric cell apoptosis and H. pylori: has the main function of VacA finally been identified?  

Microsoft Academic Search

The vacuolating cytotoxin VacA is one of the most important virulence factors of Helicobacter pylori, a bacterium causing severe gastric diseases such as ulcers and cancer. VacA forms large cytoplasmic vacuoles in cultured cells, although its effects on host cells in vivo remain to be elucidated. Three independent groups have reported that VacA induces epithelial cell apoptosis. In particular, a

Patrice Boquet; Vittorio Ricci; Antoine Galmiche; Nils C. Gauthier

2003-01-01

28

Stratigraphic correlations of the Vaca Muerta formation in the southern Neuquén basin, Argentina  

NASA Astrophysics Data System (ADS)

The petroleum Neuquén basin, south west Argentina, contains a continuous late Triassic to Cenozoic succession including continental and marine sediments, deposited under a variety of tectonic regimes. The Vaca Muerta formation is one of the major source rocks of the Neuquén basin and was deposited during the Andic cycle. This formation consists of organic-rich dark brown to black shales and mudstones deposited during a major transgression, in euxinic conditions on a shelf and slope during the Tithonian. Over most of the basin, the Vaca Muerta formation overlies the continental deposits of the Tordillo formation. The contact between the two formations is isochronous throughout the basin and marks the Tithonian transgression (Leanza, 1981). After this transgression, prograding bodies were deposited and the Vaca Muerta corresponds to the distal part of this latest. It includes stages from Middle Tithonian in the south to Valanginian in the north (Leanza & Hugo, 1977). The Vaca Muerta formation is well exposed in the southern part of the Neuquén basin, from the Picun Leufu Anticline to the north of the town of Las Lajas. It corresponds in these two areas to a succession of dark to brown shales and carbonate beds. In details, we can divide it into two parts: the Lower Vaca Muerta and the Upper Vaca Muerta. Above, the Picun Leufu formation overlies the Vaca Muerta formation and consists of carbonaceous and siliciclastics prograditional bodies. This unit is absent in the "North Zapala Zone" and its lateral equivalent is less carbonaceous. In this poster; we propose eight detailed sedimentological logs, which are correlated along 120 km north-south trend (from the Picun Leufu Anticline to the south west to the Agrio thrust Belt (ATB) to the north). This correlation will be used to assess the vertical and lateral variability of the Vaca Muerta deposits and to define the palaeogeographic evolution of that region. This allowed us to identify two major prograding sequences during this period. The sedimentary response in the distal (central?) part of the basin (ATB) is characterized by an undifferentiated deposits of organic-rich dark brown to black shales and mudstones (Vaca Muerta facies ), while in the proximal part we can identified two prograding sequences, the first one mainly siliciclastic and the second one mainly carbonated. The transition between these two sequences is characterized by a relief inversion of the southern part of the Neuquen basin related to the uplift of the Huincul Ridge (close to Zapala city). This tectonic movement involves the establishment on the southern edge of the basin of a blue marls deposits (lower part of Picun Leufu formation) which corresponds laterally to a carbonate platform (member Los Catutos of Vaca Muerta) on the structural high.

Nesma, Krim; Patrice, Imbert; Cedric, Bonnel; Charles, Aubourg

2013-04-01

29

Expression and Antigenic Evaluation of VacA Antigenic Fragment of Helicobacter Pylori  

PubMed Central

Objective(s) : Helicobacter pylori, a human specific gastric pathogen is a causative agent of chronic active gastritis. The vacuolating cytotoxin (VacA) is an effective virulence factor involved in gastric injury. The aim of this study was to construct a recombinant protein containing antigenic region of VacA gene and determine its antigenicity. Materials and Methods: The antigenic region of VacA gene was detected by bioinformatics methods. The polymerase chain reaction method was used to amplify a highly antigenic region of VacA gene from chromosomal DNA of H. pylori. The eluted product was cloned into the prokaryotic expression vector pET32a. The target protein was expressed in the Escherichia coli BL21 (DE3) pLysS. The bacteria including pET32a-VacA plasmids were induced by IPTG. The antigenicity was finally studied by western blotting using sera of 15 H. pylori infected patients after purification. Results: Enzyme digestion analysis, PCR and DNA sequencing results showed that the target gene was inserted correctly into the recombinant vector. The expressed protein was purified successfully via affinity chromatography. Data indicated that antigenic region of VacA protein from Helicobacter pylori was recognized by all 15 patient’s sera. Conclusion : Our data showed that antigenic region of VacA protein can be expressed by in E. co.li. This protein was recognized by sera patients suffering from H. pylori infection. the recombinant protein has similar epitopes and close antigenic properties to the natural form of this antigen. Recombinant antigenic region of VacA protein also seems to be a promising antigen for protective and serologic diagnosis .

Hasanzadeh, Leila; Ghaznavi-Rad, Ehsanollah; Soufian, Safieh; Farjadi, Vahideh; Abtahi, Hamid

2013-01-01

30

Selective Inhibition of Ii-dependent Antigen Presentation by Helicobacter pylori Toxin VacA  

PubMed Central

A major virulence factor in the stomach chronic infection by Helicobacter pylori is a protein toxin (VacA), which alters cell membrane trafficking of late endosomal/prelysosomal compartments. Its role in the chronic infection established by H. pylori is unknown. To test the possibility that VacA alters antigen processing taking place in prelysosomal compartments, we have used the well-established model of antigen processing and presentation consisting of tetanus toxoid–specific human (CD4+) T cells stimulated by autologous antigen-pulsed Epstein-Barr virus-transformed B cells. We found that VacA interferes with proteolytic processing of tetanus toxin and toxoid and specifically inhibits the Ii-dependent pathway of antigen presentation mediated by newly synthesized major histocompatibility complex (MHC) class II, while leaving unaffected the presentation pathway dependent on recycling MHC class II. The results presented here suggest that VacA may contribute to the persistence of H. pylori by interfering with protective immunity and that this toxin is a new useful tool in the study of the different pathways of antigen presentation.

Molinari, Maurizio; Salio, Mariolina; Galli, Carmela; Norais, Nathalie; Rappuoli, Rino; Lanzavecchia, Antonio; Montecucco, Cesare

1998-01-01

31

Sedimentation Survey of Toa Vaca, Puerto Rico, June-July 2002.  

National Technical Information Service (NTIS)

The Lago Toa Vaca dam is located in the municipality of Villalba in Southern Puerto Rico, and is owned and operated by the Puerto Rico Aqueduct and Sewer Authority. Construction was completed in 1972 as the first phase of a multi-purpose project the conte...

L. R. Soler-Lopez

2004-01-01

32

Helicobacter pylori Vacuolating Cytotoxin (VacA) Disorganizes the Cytoskeletal Architecture of Gastric Epithelial Cells  

Microsoft Academic Search

Helicobacter pylori colonization of the gastric mucosa induces peptic ulcer disease and interferes with ulcer healing. Re-epithelialization is an essential component of ulcer healing. It requires cell migration and proliferation which are dependent on the cell cytoskeleton. Most H. pylori strains produce a toxin (VacA) that induces multiple structural and functional changes in epithelial cells. In this study, we investigated

Rama Pai; Andrzej S. Tarnawski

1999-01-01

33

Petroleum systems charged by the Vaca Muerta (Tithonian) Formation: Neuquen basin, Argentina  

SciTech Connect

Tithonian (Upper Jurassic) source rock sequences are responsible for a significant volume of petroleum reserves on a global basis. This research defines the petroleum systems within the Neuquon basin that are charged from the Tithonian Vaca Muerta Formation, a unit deposited in a low angle ramp setting that is characterized in seismic and geochemical terms to contain three distinct organic facies. The oil types that correlate to the different organic facies are used to define effective migration pathways. The results indicate that the distal condensed sections are volumetrically significant but physical constraints related to hydrocarbon expulsion and migration contribute to decreased system efficiency. In contrast, the hydrocarbon potential of the shelfal condensed sections have less volumetric significance but exhibit higher efficiency due to the shorter distance required for fracture propagation (i.e., related to the expulsion event) and the effective juxtaposition of migration conduits and/or potential reservoirs. Organic facies are also identified within the Picun Leufu subbasin (South Embayment) that generate a hydrocarbon charge at relatively low levels of thermal stress. The sequence of events required for effective hydrocarbon entrapment is demonstrated by time-slice analysis for the Vaca Muerta-Lajas(!), Vaca Muerta-Sierras Blancas/Tordillo/Catriel/Qda. del Sapo (!), and Vaca Muerta-Quintuco/Mulichinco/Loma Montosa(!) Petroleum Systems.

Wavrek, D.A.; Collister, J.W.; Quick, J.C.; Allen, R.B. [Univ. of Utah, Salt Lake City (United States)] [and others

1996-08-01

34

Sedimentation Survey of Lago Toa Vaca, Puerto Rico, June-July 2002  

USGS Publications Warehouse

The Lago Toa Vaca dam is located in the municipality of Villalba in southern Puerto Rico, and is owned and operated by the Puerto Rico Aqueduct and Sewer Authority. Construction was completed in 1972 as the first phase of a multi-purpose project that contemplated four possible diversions from other basins to mitigate the rapid storage capacity loss of Lago Guayabal, located immediately downstream of the Toa Vaca dam. The latter phases of the intra-basin diversions were cancelled, and currently, the reservoir receives runoff from only 56.8 square kilometers of its drainage area. Lago Toa Vaca reservoir when constructed was to be used for irrigation of croplands in the southern coastal plain. The reservoir had an original storage capacity of 68.94 million cubic meters. Sedimentation has reduced the storage capacity by only 7 percent between 1972 and 2002 to 64.08 million cubic meters. This represents a long-term sedimentation rate of about 162,000 cubic meters per year. Based on the 2002 sedimentation survey, Lago Toa Vaca has a sediment trapping efficiency of about 98 percent and a drainage area-normalized sedimentation rate of about 3,086 cubic meters per square kilometer per year between 1972 and 2002. At the current long-term sedimentation rate the reservoir would lose its storage capacity by the year 2400.

Soler-Lopez, Luis R.

2004-01-01

35

Vacuolating cytotoxin A (VacA), a key toxin for Helicobacter pylori pathogenesis  

PubMed Central

More than 50% of the world's population is infected with Helicobacter pylori (H. pylori). Chronic infection with this Gram-negative pathogen is associated with the development of peptic ulcers and is linked to an increased risk of gastric cancer. H. pylori secretes many proteinaceous factors that are important for initial colonization and subsequent persistence in the host stomach. One of the major protein toxins secreted by H. pylori is the Vacuolating cytotoxin A (VacA). After secretion from the bacteria via a type V autotransport secretion system, the 88 kDa VacA toxin (comprised of the p33 and p55 subunits) binds to host cells and is internalized, causing severe “vacuolation” characterized by the accumulation of large vesicles that possess hallmarks of both late endosomes and early lysosomes. The development of “vacuoles” has been attributed to the formation of VacA anion-selective channels in membranes. Apart from its vacuolating effects, it has recently become clear that VacA also directly affects mitochondrial function. Earlier studies suggested that the p33 subunit, but not the p55 subunit of VacA, could enter mitochondria to modulate organelle function. This raised the possibility that a mechanism separate from pore formation may be responsible for the effects of VacA on mitochondria, as crystallography studies and structural modeling predict that both subunits are required for a physiologically stable pore. It has also been suggested that the mitochondrial effects observed are due to indirect effects on pro-apoptotic proteins and direct effects on mitochondrial morphology-related processes. Other studies have shown that both the p55 and p33 subunits can indeed be efficiently imported into mammalian-derived mitochondria raising the possibility that they could re-assemble to form a pore. Our review summarizes and consolidates the recent advances in VacA toxin research, with focus on the outstanding controversies in the field and the key remaining questions that need to be addressed.

Palframan, Samuel L.; Kwok, Terry; Gabriel, Kipros

2012-01-01

36

vacA Genotypes in Helicobacter pylori Strains Isolated from Children with and without Duodenal Ulcer in Brazil  

Microsoft Academic Search

Data concerning the association between vacA genotypes and disease in children in both developed and de- veloping countries are scarce, especially because of the small number of children with a duodenal ulcer studied. The vacA genotypes of Helicobacter pylori strains obtained from 65 children (24 with a duodenal ulcer and 41 without a duodenal ulcer; 33 girls; mean age, 10.2

VALQUIRIA RIBEIRO DE GUSMAO; EDILBERTO NOGUEIRA MENDES; MARIA DE MAGALHAES QUEIROZ; GIFONE AGUIAR ROCHA; ANDREIA MARIA CAMARGOS ROCHA; ABDUSSALAM ALI; RAMADAN ASHOUR; ANFRISINA SALES; TELES CARVALHO

2000-01-01

37

Colonization of Mexican Patients by Multiple Helicobacter pylori Strains with Different vacA and cagA Genotypes  

Microsoft Academic Search

Helicobacter pylori virulence determinants have not previously been studied in detail in Latin Americans with H. pylori infections. We characterized the vacA (vacuolating cytotoxin gene A) and cagA (cytotoxin-associated gene A) types of more than 400 single-colony isolates from 20 patients in Mexico City. For 17 patients H. pylori strains of two or more different vacA genotypes were isolated from

ROSARIO MORALES-ESPINOSA; GONZALO CASTILLO-ROJAS; GERARDO GONZALEZ-VALENCIA; SERGIO PONCE DE LEON; ALEJANDRO CRAVIOTO; JOHN C. ATHERTON; YOLANDA LOPEZ-VIDAL

1999-01-01

38

Clinical and histological associations of cagA and vacA genotypes in Helicobacter pylori gastritis  

Microsoft Academic Search

AIMS: To determine the relation among the cytotoxin associated gene (cagA) and vacuolating cytotoxin gene (vacA) status of Helicobacter pylori isolates, the associated clinical diseases, and the severity and pattern of chronic gastritis. METHODS: Helicobacter pylori was cultured from gastric biopsies obtained from dyspeptic patients. DNA was extracted from the isolates and the cagA and vacA status determined by the

V. J. Warburton; S. Everett; N. P. Mapstone; A. T. Axon; P. Hawkey; M. F. Dixon

1998-01-01

39

vacA genotypes of Helicobacter pylori in relation to cagA status and clinical outcomes in Iranian populations.  

PubMed

Mosaicism in vacA alleles with two distinct families of vacA signal sequences (s1 and s2) and two distinct families of middle region alleles (m1 and m2) has been reported. Research suggests that the vacA s1 genotype is closely associated with duodenal ulcer disease and with high cytotoxin production. The aims of this study were to evaluate the role of vacA genotyping with respect to gastric inflammation and injury, and clinical presentation in Iranian populations. Genomic DNA of biopsy specimens from patients with gastritis, peptic ulcer disease (PUD), or gastric cancer (GC) were characterized based on ureC (glmM), cagA, and vacA genotyping by using polymerase chain reaction. Of 167 patients including 33 with PUDs, 129 with non-ulcer dyspepsia (NUD), and 5 with GC, 96 (57.5%) cases were infected by Helicobacter pylori. Among these patients, H. pylori were isolated from 19 (57.7%) PUD patients, 74 (68.7%) NUD patients, and 3 (60%) GC patients. The cagA was detected in 76% of H. pylori-positive cases. The vacA s1-m2 genotype was the most prevalent in 7/19 PUD (37%) and 30/74 NUD (40.5%) patients with H. pylori infection. The prevalence of vacA s2-m1 (8%) was high in Iranian isolates. A significant association was not found between H. pylori genotypes and clinical outcomes. The vacA genotypes and cagA status were not useful markers for gastroduodenal diseases in Tehran, Iran. PMID:18653971

Jafari, Fereshteh; Shokrzadeh, Lleila; Dabiri, Hossein; Baghaei, Kaveh; Yamaoka, Yoshio; Zojaji, Homayon; Haghazali, Mehrdad; Molaei, Masha; Zali, Mohammad Reza

2008-07-01

40

Random Mutagenesis of Helicobacter pylori vacA To Identify Amino Acids Essential for Vacuolating Cytotoxic Activity  

Microsoft Academic Search

Received 8 June 2006\\/Returned for modification 12 July 2006\\/Accepted 22 August 2006 VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. In this study, we analyzed a library of plasmids expressing randomly mutated forms of recombinant VacA and identified 10

Mark S. McClain; Daniel M. Czajkowsky; Victor J. Torres; Gabor Szabo; Zhifeng Shao

2006-01-01

41

Clinical and pathological importance of heterogeneity in vacA, the vacuolating cytotoxin gene of Helicobacter pylori  

Microsoft Academic Search

BACKGROUND & AIMS: vacA encodes the vacuolating cytotoxin of Helicobacter pylori and exhibits marked variation in signal sequence and midgene coding regions. The implications for gastroduodenal pathology are unknown. The aim of this study was to define the association of vacA genotype with gastric inflammation and injury, in vitro cytotoxin activity, and peptic ulceration. METHODS: Sixty-one consecutive dyspeptic patients underwent

JC Atherton; RM Peek; KT Tham; MJ Blaser

1997-01-01

42

Major virulence factors, VacA and CagA, are commonly positive inHelicobacter pylori isolates in Japan  

Microsoft Academic Search

Background—VacA and CagA proteins have been reported to be major virulence factors of Helicobacter pylori. However, antibodies against these proteins are frequently found in the sera of Japanese patients regardless of their gastroduodenal status.Aim—To evaluate the expression of VacA and CagA proteins by H pylori strains isolated in Japan.Methods—By using specific antibodies raised against recombinant VacA and CagA proteins, the

S Maeda; K Ogura; H Yoshida; F Kanai; T Ikenoue; N Kato; Y Shiratori; M Omata

1998-01-01

43

Sequence and Apoptotic Activity of VacA Cytotoxin Cloned from a Helicobacter pylori Thai Clinical Isolate  

PubMed Central

The vacuolating cytotoxin VacA produced by Helicobacter pylori induces the formation of large cytoplasmic vacuoles in host gastric epithelial cells as well as a release of cytochrome C from mitochondria resulting in cell apoptosis. Considerable sequence diversity in VacA relating to different degrees of disease severity is observed with clinical samples from a multitude of geographic places. In this study we describe expression in Escherichia coli, purification to homogeneity and in vitro assay of its apoptotic activity of a VacA toxin from a H. pylori isolate of a Thai patient with gastrointestinal lymphoma. Sequencing revealed that the deduced amino acid sequence of the cloned Thai isolate VacA is similar to H. pylori s1/m2 type strains. The percent sequence similarity to the model strain 60190 was lower due to the presence of extra amino acids in the mid (m) region. The purified VacA toxin exhibited significant apoptotic activity on both T84 and MDCK epithelial cell lines, as revealed by DAPI staining, whereby the observed activity was significantly higher on MDCK cells. These findings could relate to a modulation of VacA activity on host cells in the Thai isolate-VacA toxin that may differ from those of the model strain.

Junaid, Muhammad; Al-Gubare, Sarbast; Yousef, Muhammad; Na Ubol, Mathukorn; Leetachewa, Somphob; Muanprasat, Chatchai; Angsuthanasombat, Chanan; Chaicumpa, Wanpen; Ali, Niaz; Katzenmeier, Gerd

2014-01-01

44

Sequence and Apoptotic Activity of VacA Cytotoxin Cloned from a Helicobacter pylori Thai Clinical Isolate.  

PubMed

The vacuolating cytotoxin VacA produced by Helicobacter pylori induces the formation of large cytoplasmic vacuoles in host gastric epithelial cells as well as a release of cytochrome C from mitochondria resulting in cell apoptosis. Considerable sequence diversity in VacA relating to different degrees of disease severity is observed with clinical samples from a multitude of geographic places. In this study we describe expression in Escherichia coli, purification to homogeneity and in vitro assay of its apoptotic activity of a VacA toxin from a H. pylori isolate of a Thai patient with gastrointestinal lymphoma. Sequencing revealed that the deduced amino acid sequence of the cloned Thai isolate VacA is similar to H. pylori s1/m2 type strains. The percent sequence similarity to the model strain 60190 was lower due to the presence of extra amino acids in the mid (m) region. The purified VacA toxin exhibited significant apoptotic activity on both T84 and MDCK epithelial cell lines, as revealed by DAPI staining, whereby the observed activity was significantly higher on MDCK cells. These findings could relate to a modulation of VacA activity on host cells in the Thai isolate-VacA toxin that may differ from those of the model strain. PMID:24963483

Junaid, Muhammad; Al-Gubare, Sarbast; Yousef, Muhammad; Na Ubol, Mathukorn; Leetachewa, Somphob; Muanprasat, Chatchai; Angsuthanasombat, Chanan; Chaicumpa, Wanpen; Ali, Niaz; Katzenmeier, Gerd

2014-01-01

45

Helicobacter pylori oipA genetic diversity and its associations with both disease and cagA, vacA s, m, and i alleles among Bulgarian patients.  

PubMed

Prevalence of outer inflammatory protein (oipA) gene functional status in Helicobacter pylori strains from Southeastern Europe is still unclear. H. pylori strains from 70 symptomatic patients were polymerase chain reaction (PCR) assessed for cagA and vacA types, and oipA gene functional status was evaluated by PCR and sequencing. Our results demonstrated a high prevalence of strains with oipA status "on" genes (81%) and strong association between them and peptic ulcers, cagA, and vacA s1 and s1/m1 genotypes, regardless of the patient gender, place of residence, and age. Importantly, most vacA i1 strains (93%) harbored oipA status "on" versus only 57% of those with vacA i2 type. The vacA i1 genotype was less frequent (66%) than both cagA and vacA s1 types. The virulent strains with cagA(+) and vacA s1, m1, and i1 were detected in 35% as a predominant genotype and almost all (96%) of these strains harbored oipA status "on". In conclusion, the high prevalence of in-frame oipA gene strains (81%), associated with peptic ulcers and cagA(+), vacA s1, m1, m2, and, importantly, i1 genotypes, indicates a strong synergistic activity of H. pylori virulence factors. PMID:21937185

Markovska, Rumyana; Boyanova, Lyudmila; Yordanov, Daniel; Gergova, Galina; Mitov, Ivan

2011-12-01

46

The role of small molecular weight compounds to increase vacuolation induced by VacA toxin in vitro.  

PubMed

VacA is a vacuolation protein toxin secreted by Helicobacter pylori. Many compounds have been implicated in the regulation of VacA toxin activity. In this study, regulation of cell vacuolation induced by VacA was observed with the addition of glycine, glycine hydrochloride, xylitol, and taurine by neutral red dye uptake assay using gastric human epithelial cell cultures. Glycine, xylitol, and taurine increased cell vacuolation significantly after 48h (p<0.05), with their effect apparent in a wide concentration range (0.2mM to about 100mM). Changes were sharp in respect of concentration and showed little dose-response characteristics. In contrast, upregulation of glycine hydrochloride on cell vacuolation in weak acidic extracellular pH was much retarded with VacA activity not initiated until 72h. In addition, our results showed that cell vacuolation was highest when the pH was 6.8. The increase in vacuolation was gentle in weak acidic extracellular pH and the increase dose-dependent with a Pearson correlation coefficient (r) of 0.986 from 0.2 to 6.25mM. In this concentration range and at the same time point, the pH decrease was negatively correlated with vacuolating activity (r=0.922, p<0.01). In conclusion, our study showed that three small molecular compounds can increase vacuolation induced by VacA toxin in vitro. PMID:20403422

Sun, Juan; Wu, Yan; Su, Zhuang; Liu, Zhifang; Su, Bingzhong; Liu, Zhiyue; Liu, Wenzhong; Zhao, Haixia; Tana; Bateer; Eshita, Yuki; Chi, Baofeng; Zhao, Lingyan; Fang, Xin; Hao, Wenli; Wu, Siqintoya; Bian, Jiang; Chen, Jie; Ouyang, Xiaohui

2010-08-01

47

The association of vacA genotypes and Helicobacter pylori-related gastroduodenal diseases in the Middle East  

PubMed Central

The variations in the three regions of the Helicobacter pylori vacA gene, the signal (s1 and s2), intermediate (i1 and i2) and middle regions (m1 and m2), are known to cause the differences in vacuolating activities. However, it was unclear whether these vacA genotypes are associated with the development of gastric cancer and peptic ulcer in the Middle East. The aim was to identify the prevalence of vacA genotypes in the Middle East and the association with gastroduodenal diseases. We investigated the relationship of vacA genotypes to H. pylori-related disease development by meta-analysis using previous reports of 1,646 patients from the Middle East. The frequency of the vacA s1, m1 and i1 genotypes in the Middle Eastern strains was 71.5% (1,007/ 1,409), 32.8% (427/1,300) and 40.7% (59/145), respectively. Importantly, the frequency of vacA s- and m-region genotypes significantly differed between the north and south parts of the Middle East countries (P<0.001). The vacA genotypes significantly increased the risk of gastric cancer (odds ratio [OR]: 4.02, 95% confidence interval [CI]: 1.98–8.14 for the s1 genotype; 2.50, 1.62–3.85 for m1; 5.27, 1.97–14.1 for s1m1; 15.03, 4.69–48.17 for i1) and peptic ulcers (OR: 3.07, 95% CI: 2.08–4.52 for s1; 1.81, 1.36–2.42 for m1). The cagA-positive genotype frequently coincided with the s1, m1 and i1 genotypes. The vacA s- and m-region genotypes may be useful risk factors for gastrointestinal diseases in the Middle East, similar to European and American countries. Further studies will be required to evaluate the effects of the i-region genotype.

Sugimoto, M.; Zali, M. R.

2011-01-01

48

Pathogenicity island cag, vacA and IS605 genotypes in Mexican strains of Helicobacter pylori associated with peptic ulcers  

PubMed Central

Background Helicobacter pylori is associated with chronic gastritis, peptic ulcers, and gastric cancer. Two major virulence factors of H. pylori have been described: the pathogenicity island cag (cag PAI) and the vacuolating cytotoxin gene (vacA). Virtually all strains have a copy of vacA, but its genotype varies. The cag PAI is a region of 32 genes in which the insertion of IS605 elements in its middle region has been associated with partial or total deletions of it that have generated strains with varying virulence. Accordingly, the aim of this work was to determine the cag PAI integrity, vacA genotype and IS605 status in groups of isolates from Mexican patients with non-peptic ulcers (NPU), non-bleeding peptic ulcers (NBPU), and bleeding peptic ulcers (BPU). Methods The cag PAI integrity was performed by detection of eleven targeted genes along this locus using dot blot hybridization and PCR assays. The vacA allelic, cag PAI genotype 1 and IS605 status were determined by PCR analysis. Results Groups of 16-17 isolates (n = 50) from two patients with NPU, NBPU, and BPU, respectively, were studied. 90% (45/50) of the isolates harbored a complete cag PAI. Three BPU isolates lacked the cag PAI, and two of the NBPU had an incomplete cag PAI: the first isolate was negative for three of its genes, including deletion of the cagA gene, whereas the second did not have the cagM gene. Most of the strains (76%) had the vacA s1b/m1 genotype; meanwhile the IS605 was not present within the cag PAI of any strain but was detected elsewhere in the genome of 8% (4/50). Conclusion The patients had highly virulent strains since the most of them possessed a complete cag PAI and had a vacA s1b/m1 genotype. All the isolates presented the cag PAI without any IS605 insertion (genotype 1). Combined vacA genotypes showed that 1 NPU, 2 NBPU, and 1 BPU patients (66.6%) had a mixed infection; coexistence of H. pylori strains with different cag PAI status was observed in 1 NBPU and 2 BPU (50%) of the patients, but only two of these patients (NBPU and BPU) had different vacA genotypes.

2011-01-01

49

Non-invasive Genotyping of Helicobacter pylori cagA, vacA, and hopQ from Asymptomatic Children  

PubMed Central

Background H. pylori infection is usually acquired in childhood, but little is known about its natural history in asymptomatic children, primarily due to the paucity of non-invasive diagnostic methods. H. pylori strains harboring cagA and specific alleles of hopQ and vacA are associated with increased risk for gastric cancer. Many studies of H. pylori virulence markers in children have the bias that symptomatic subjects are selected for endoscopy, and these children may harbor the most virulent strains. Our aim: to genotype cagA, hopQ and vacA alleles in stool DNA samples of healthy Colombian children residing in an area with high incidence of gastric cancer, in order to avoid selection bias resulting from endoscopy. Methods H. pylori status of 86 asymptomatic children was assessed by 13C-Urea Breath Test (UBT) and PCR. H. pylori 16S rRNA, cagA, hopQ and vacA genes were amplified from stool DNA samples and sequenced. Results UBT was positive in 69 (80.2%) of 86 children; in stool DNA analysis, 78.3% were positive by 16S rRNA PCR. cagA, vacA and hopQ were detected in 66.1%, 84.6%, and 72.3% of stool DNA samples from 16S rRNA positive children. Of the children's DNA samples which revealed vacA and hopQ alleles, 91.7% showed vacA s1 and 73.7% showed type I hopQ. Type I hopQ alleles were associated with cagA-positivity and vacA s1 genotypes (P<0.0001). Conclusions Using stool DNA samples, virulence markers of H. pylori were successfully genotyped in a high percentage of the asymptomatic infected children, revealing a high prevalence of genotypes associated with virulence. Type I hopQ alleles were associated with the presence of cagA and the vacA s1 genotype.

Sicinschi, Liviu A.; Correa, Pelayo; Bravo, Luis E.; Peek, Richard M.; Wilson, Keith T.; Loh, John T.; Yepez, Maria C.; Gold, Benjamin D.; Thompson, Dexter T.; Cover, Timothy L.; Schneider, Barbara G.

2011-01-01

50

Adição de Lipídios na Ração de Vacas Leiteiras: Parâmetros Fermentativos Ruminais, Produção e Composição do Leite1  

Microsoft Academic Search

RESUMO - Objetivou-se avaliar o efeito de dois níveis de lipídios (3 e 7%) na dieta de vacas em lactação e, dentro do nível de 7% avaliar duas fontes de lipídios (grão de soja moído e óleo de soja), sobre a produção e composição do leite, os parâmetros ruminais, a atividade de produção de amônia pela microbiota ruminal e o

Luiz Henrique Vargas; Rogério de Paula Lana; Gulab Newamdram Jham; Ferlando Lima Santos; Augusto César de Queiroz; Antônio Bento Mancio

51

Association between Helicobacter pylori, cagA, and vacA Status and Clinical Presentation in Iranian Children  

PubMed Central

Objective Seroprevalence of H. pylori infection in Iran exceeds 65% of pediatric population. In this study, we intended to find association between the virulence genes (cagA and vacA) and clinical presentations. Methods H. pylori isolates were achieved from the gastric mucosa of children. In each case, the gastric biopsy specimens were cultured and the organisms identified. Detection of different genotypes was carried out by PCR method. Findings A total of 106 biopsy specimens were cultured and 33 H. pylori isolates obtained. Among these 33 H. pylori strains 24 (73%) were cagA-positive. Genotypes of vacA s1m2, s1m1, s2m2, and s2m1 were 45.5%, 30.3%, 21.2%, and 3%, respectively. Most female patients were infected with genotype s1m2. The vacA-m1 strains were significantly more common in patients with nodular gastritis. There were no statistical differences between the vacA and cagA genotypes and clinical outcomes. Conclusion The frequency of cagA genotype was high. In this study, nodular gastritis was a common finding and was rather significantly associated with m1 allele of vacA.

Rafeey, Mandana; Ghotaslou, Reza; Milani, Morteza; Farokhi, Nima; Ghojazadeh, Morteza

2013-01-01

52

Polymorphism in the Helicobacter pylori CagA and VacA toxins and disease  

PubMed Central

Half of the world’s population is infected with Helicobacter pylori and approximately 20% of infected individuals develop overt clinical disease such as ulcers and stomach cancer. Paradoxically, despite its classification as a class I carcinogen, H. pylori has been shown to be protective against development of asthma, allergy, and esophageal disease. Given these conflicting roles for H. pylori, researchers are attempting to define the environmental, host, and pathogen interactions that ultimately result in severe disease in some individuals. From the bacterial perspective, the toxins, CagA and VacA, have each been shown to be polymorphic and to contribute to disease in an allele-dependent manner. Based on the notable advances that have recently been made in the CagA field, herein we review recent studies that have begun to shed light on the role of CagA polymorphism in H. pylori disease. Moreover, we discuss the potential interaction of CagA and VacA as a mediator of gastric disease.

Bridge, Dacie R.; Merrell, D. Scott

2013-01-01

53

Clustering of Helicobacter pylori VacA in Lipid Rafts, Mediated by Its Receptor, Receptor-Like Protein Tyrosine Phosphatase  , Is Required for Intoxication in AZ-521 Cells  

Microsoft Academic Search

Helicobacter pylori vacuolating cytotoxin, VacA, induces multiple effects on epithelial cells through different cellular events: one involves pore formation, leading to vacuolation, mitochondrial damage, and apoptosis, and the second involves cell signaling, resulting in stimulation of proinflammatory responses and cell detachment. Our recent data demonstrated that VacA uses receptor-like protein tyrosine phosphatase (RPTP )a s a receptor, of which five

Masaaki Nakayama; Jyunzo Hisatsune; Eiki Yamasaki; Yoshito Nishi; Akihiro Wada; Hisao Kurazono; Jan Sap; Kinnosuke Yahiro; Joel Moss; Toshiya Hirayama

2006-01-01

54

Prevalence and Correlation with Clinical Diseases of Helicobacter pylori cagA and vacA Genotype among Gastric Patients from Northeast China  

PubMed Central

Helicobacter pylori vacA and cagA genes have significant genetic heterogenicity, resulting in different clinical outcomes. Northeast part of China has reported high prevalence of H. pylori infections and gastric cancer. Hence, we investigated the H. pylori cagA and vacA genotypes with clinical outcomes in Northeast China. Gastric tissue samples (n = 169), chronic gastritis (GIs), gastric ulcer (GU), and gastric cancer (GC) were analysed for 16S rRNA ureA, cagA, and cagA genotypes by PCR. A total of 141 (84%) cases were found positive for H. pylori by 16S rRNA and ureA. GC showed high H. pylori infection (93%) compared with GIs (72%) and GU (84%). The vacAs1am1 was highly found in GC (40%) and GU (36%), vacAs1am2 in GIs (33%), vacAs1bm1 (14%) and vacAs1bm2 (8%) in GU cases, and s2m1 in normal cases (33%), while vacAs1cm1 showed low frequency in GIs (2%) and GU (3%) and GC showed negative result. The East-Asian cagA strain was highly observed in GC (43%), as compared to GIs (41%) and GU (20%). The East-Asian cagA/vacAs1am1 was significantly higher in GC (23%) than in GU (22%) and GIs (145) patients. The East-Asian type cagA with vacAs1a and vacAm1 is the most predominant genotype in H. pylori strains of Northeast China.

Aziz, Faisal; Chen, Xin; Yang, Xuesong; Yan, Qiu

2014-01-01

55

Direct determination of Helicobacter pylori vacA genotypes and cagA gene in gastric biopsies and relationship to gastrointestinal diseases  

Microsoft Academic Search

OBJECTIVE:Our aim was to detect Helicobacter pylori (H. pylori) from gastric biopsies of 248 patients using a novel, polymerase chain reaction (PCR)-based methodology, which simultaneously facilitates the determination of H. pylori vacA genotypes and cagA gene.METHODS:A simple methodology for sample preparation was established and PCR was performed with primer systems for the 16S rRNA, vacA, and cagA genes, thus circumventing

Jochen Rudi; Andreas Rudy; Matthias Maiwald; Dirk Kuck; Andreas Sieg; Wolfgang Stremmel

1999-01-01

56

Serum Antibodies Against Helicobacter pylori Proteins VacA and CagA Are Associated with Increased Risk for Gastric Adenocarcinoma  

Microsoft Academic Search

Infection with Helicobacter pylori is associatedwith the development of gastric cancer. To study whetherthe infection with H. pylori strains expressing thevacuolating cytotoxin (VacA) and\\/or thecytotoxin-associated protein (CagA) is associated with an increasedrisk of developing gastric adenocarcinoma, sera of 90patients with gastric cancer and 90 matched controlswith cardiovascular diseases were investigated for the presence of antibodies to VacA and CagA byimmunoblot.

Jochen Rudi; Christof Kolb; Matthias Maiwald; Ivan Zuna; Axel Von Herbay; Peter R. Galle; Wolfgang Stremmel

1997-01-01

57

Prevalence and correlation with clinical diseases of Helicobacter pylori cagA and vacA genotype among gastric patients from Northeast China.  

PubMed

Helicobacter pylori vacA and cagA genes have significant genetic heterogenicity, resulting in different clinical outcomes. Northeast part of China has reported high prevalence of H. pylori infections and gastric cancer. Hence, we investigated the H. pylori cagA and vacA genotypes with clinical outcomes in Northeast China. Gastric tissue samples (n = 169), chronic gastritis (GIs), gastric ulcer (GU), and gastric cancer (GC) were analysed for 16S rRNA ureA, cagA, and cagA genotypes by PCR. A total of 141 (84%) cases were found positive for H. pylori by 16S rRNA and ureA. GC showed high H. pylori infection (93%) compared with GIs (72%) and GU (84%). The vacAs1am1 was highly found in GC (40%) and GU (36%), vacAs1am2 in GIs (33%), vacAs1bm1 (14%) and vacAs1bm2 (8%) in GU cases, and s2m1 in normal cases (33%), while vacAs1cm1 showed low frequency in GIs (2%) and GU (3%) and GC showed negative result. The East-Asian cagA strain was highly observed in GC (43%), as compared to GIs (41%) and GU (20%). The East-Asian cagA/vacAs1am1 was significantly higher in GC (23%) than in GU (22%) and GIs (145) patients. The East-Asian type cagA with vacAs1a and vacAm1 is the most predominant genotype in H. pylori strains of Northeast China. PMID:24949419

Aziz, Faisal; Chen, Xin; Yang, Xuesong; Yan, Qiu

2014-01-01

58

Studies of Cosmic-Ray-produced Carbon-14 in the Vaca Muerta Mesosiderite  

NASA Astrophysics Data System (ADS)

We have studied the production of 5730-yr ^14C in samples of the VM10 mass of the mesosiderite Vaca Muerta. This ~165-kg mass was buried with only one surface exposed at ground level. Because of heavy corrosion, it could only be excavated in pieces ranging in size up to 4 kg. Our samples ranged from the exposed surface to about 25 cm depth. These samples were analyzed for ^14C content at the University of Arizona by accelerator mass spectrometry, and their elemental compositions were measured. The results are compared to calculations of ^14C in Vaca Muerta produced by cosmic rays, and constraints on the recent exposure record of Vaca Muerta, such as terrestrial age and preatmospheric size, are obtained. Five of the samples were fairly pure silicate, and three other samples were about 40-50% silicate. The major target for ^14C, oxygen, is ~43% by weight in the silicate. The results of surface silicate inclusions give ^14C of 37-43 dpm/kg. Samples of mesosiderite, ~45% metal, are about 23 dpm/kg ^14C at the same surface. Production rates of ^14C were calculated using the Los Alamos Monte Carlo LAHET Code System (LCS). LCS has yielded calculated production rates for ^14C and other nuclides that are in good agreement with cosmogenic-nuclide measurements in meteorites [1,2]. Earlier calculations showed that the bulk composition of a meteorite affects production rates of cosmogenic nuclides [1]. In the calculations done for Vaca Muerta, spherical objects with radii of 50 and 70 cm, a density of 5 g/cm^3, and typical bulk mesosiderite compositions were irradiated with galactic-cosmic-ray protons. Layers 2.5 cm thick were used. The calculated fluxes for each layer were then multiplied by the relevant cross sections and integrated over energy to get ^14C production rates for pure silicate and for the other samples. The calculated production profiles increased from the surface to depths of ~20-30 cm. In the 50-cm object, the profile was fairly flat to the center, but the profile dropped slightly for depths >30 cm in the 70-cm object. Production rates for ^14C were about 60 atoms/(min kg) in pure silicate but only a few atoms/(min kg) (not well determined because of the lack of cross sections) in metal. The rates for a 50-cm radius were ~10% higher than for the 70-cm radius. The ^14C measurements and the calculated production rates are only consistent with a meteoroid of short terrestrial age, as practically none of the ^14C can have decayed. The ^14C must have been produced in a body not substantially larger than a radius of 70 cm and probably not more than ~100 cm. This indicates a lack of significant erosion of the meteoroid in the last 20,000 years. If the current sampled surface were actually at some depth in the preatmospheric meteoroid, then some terrestrial age of up to about 2500 years is possible using these data. However, data from deeper samples argue against any significant terrestrial age. With some additional studies of samples at additional depths and other cosmic-ray-produced isotopes, particularly ^36Cl and Ne isotopes to constrain shielding, we may be able to derive a better model for the preatmospheric irradiation history. Acknowledgments: This work was supported by NASA, and the work at Los Alamos was done under the auspices of the U.S. Department of Energy. References: [1] Masarik J. and Reedy R. C. (1993) LPS XXIV, 937. [2] Reedy R. C. et al. (1993) LPS XXIV, 1195.

Reedy, R. C.; Masarik, J.; Jull, A. J. T.; Donahue, D. J.; Wasson, J. T.

1993-07-01

59

Source rock characteristics, Los Molles and Vaca Muerta shales, Neuquen basin, west-central Argentina  

SciTech Connect

Major hydrocarbon-producing trends of the Neuquen basin occur along its northeastern margin (Eastern Shelf) and along an east-west-trending structural high in the southern half of the basin (Neuquen Dorsal). Sediment thickness increases northward from the Neuquen Dorsal and westward from the Eastern Shelf into the Neuquen Embayment, a region that has been relatively unproductive for hydrocarbons. Major source rocks are the Lower to Middle Jurassic Los Molles Formation and the Upper Jurassic to Lower Cretaceous Vaca Muerta Formation. Los Molles shales are immature to moderately mature on the Neuquen Dorsal: vitrinite reflectance (R/sub o/) = 0.3-0.8%; thermal alteration index (TAI) = 1+ to 2; total organic carbon (TOC) = 2.0-5.0%. However, they are severely altered in the deepest part of the Neuquen Embayment (R/sub o/ = 2.5-3.0%; TAI = 3+ to 4; TOC = 1.1%). Organic matter is woody on the Neuquen Dorsal but is coaly in the Neuquen Embayment. Clay minerals are smectite and mixed layer illite-smectite on the Neuquen Dorsal whereas illite and chlorite are present in the Neuquen Embayment. Similarly, Vaca Muerta shales are immature on the Neuquen Dorsal and along much of the Eastern Shelf (R/sub o/ = 0.3-0.5%; TAI = 1 to 2-), but are mature throughout the Neuquen Embayment (R/sub o/ = 0.7-1.3%; TAI = 2-3). The lower part of the unit is a bituminous black shale (TOC = 2.5-6.5%). The dominant visual kerogen type is amorphous (Al). Clay minerals change from smectite to mixed layer illite-smectite with decreasing expandability toward the deepest part of the Neuquen Embayment. The lack of correlation between areas of source rock maturity and major hydrocarbon production suggests long-distance fluid transport out of deep portions of the basin.

Kugler, R.L.

1985-02-01

60

Reconstitution of Helicobacter pylori VacA toxin from purified components  

PubMed Central

Helicobacter pylori VacA is a pore-forming toxin that causes multiple alterations in human cells and contributes to the pathogenesis of peptic ulcer disease and gastric cancer. The toxin is secreted by H. pylori as an 88 kDa monomer (p88) consisting of two domains (p33 and p55). While an X-ray crystal structure for p55 exists and p88 oligomers have been visualized by cryo-electron microscopy, a detailed analysis of p33 has been hindered by an inability to purify this domain in an active form. In this study, we expressed and purified a recombinant form of p33 under denaturing conditions and optimized conditions for the refolding of soluble protein. We show that refolded p33 can be added to purified p55 in trans to cause vacuolation of HeLa cells and inhibition of IL-2 production by Jurkat cells, effects identical to those produced by the p88 toxin from H. pylori. The p33 protein markedly enhances the cell-binding properties of p55. Size exclusion chromatography experiments suggest that p33 and p55 assemble into a complex consistent with the size of a p88 monomer. Electron microscopy of these p33/p55 complexes reveals small rod-shaped structures that can convert to oligomeric flower-shaped structures in the presence of detergent. We propose that the oligomerization observed in these experiments mimics the process by which VacA oligomerizes when in contact with membranes of host cells.

Gonzalez-Rivera, Christian; Gangwer, Kelly A.; McClain, Mark S.; Eli, Ilyas M.; Chambers, Melissa G.; Ohi, Melanie D.; Lacy, D. Borden; Cover, Timothy L.

2010-01-01

61

Clinical relevance of the cagA, vacA, and iceA status of Helicobacter pylori  

Microsoft Academic Search

Background & Aims: Clinical outcome of Helicobacter pylori infection may be associated with specific virulence-associated bacterial genotypes. The aim of this study was to assess the relationships between H. pylori cagA, vacA, and iceA status and severity of disease. Methods: Gastric biopsy specimens from 94 patients in The Netherlands were analyzed by polymerase chain reaction and reverse hybridization. Results:cagA was

Céu Figueiredo; Ricardo Sanna; Anton Plaisier; Peter Schneeberger; Wink de Boer; Wim Quint

1998-01-01

62

Identification and Analysis of a New vacA Genotype Variant of Helicobacter pylori in Different Patient Groups in Germany  

Microsoft Academic Search

genotype and peptic ulceration (P < 0.001). In contrast, 31% of the patients from the NUD control group were infected with strains of vacA genotype s2. Particular midregion genotypes (m1 and m2) were not associated with clinical manifestations. The midregions from 18% of the isolates could not be classified by the proposed scheme. DNA sequencing revealed high homology between the

SONJA STROBEL; STEFAN BERESWILL; PETER BALIG; PETER ALLGAIER; HANS-GUNTHER SONNTAG; MANFRED KIST

1998-01-01

63

Antibody against Helicobacter pylori CagA and VacA and the risk for gastric cancer  

Microsoft Academic Search

AIM: Helicobacter pylori is associated with gastric cancer. Our aim was to investigate whether CagA or VacA seropositivity provides additional risk for gastric cancer. METHODS: Sera from 110 gastric cancer patients were sex and aged matched with asymptomatic controls. H pylori status was determined by IgG enzyme immunoassay (HM-CAP EIA); CagA status was assessed by enzyme linked immunosorbent assay (ELISA)

Y. Yamaoka; T. Kodama; K. Kashima; D. Y. Graham

1999-01-01

64

Typing of Helicobacter pylori vacA Gene and Detection of cagA Gene by PCR and Reverse Hybridization  

Microsoft Academic Search

The present report describes an analysis of two virulence genes of Helicobacter pylori. Parts of the cagA gene, as well as parts from the signal (s) and middle (m) regions of the mosaic vacA gene, were amplified with biotin-labelled PCR primers and the products were subsequently analyzed by a single-step reverse hybridiza- tion line probe assay (LiPA). This assay comprises

L. J. VAN DOORN; C. FIGUEIREDO; R. ROSSAU; G. JANNES; M. VAN ASBROECK; J. C. SOUSA; F. CARNEIRO; W. G. V. QUINT

1998-01-01

65

Helicobacter pylori vacA arrangement and related diseases: a retrospective study over a period of 15 years.  

PubMed

Peptic ulcer disease incidence is decreasing. Both s1m1 and s1m2 vacA gene combinations of Helicobacter pylori have been associated with the development of major gastroduodenal diseases. This study assessed whether H. pylori vacA gene arrangement changed over 15 years in a Southern Italy area. H. pylori-positive patients observed in January-June 1989 and January-June 2005 were selected. Histological specimens were retrieved to extract DNA for vacA arrangement characterization (mid-m and peptide signal-s regions) by using the polymerase chain reaction. Fifty-nine patients in the first period and 56 matched patients in the second period were evaluated. A correlation between s1 presence and intestinal metaplasia at histology was found. Overall, the s1m1 combination increased (P < 0.01) and s2m2 decreased (P < 0.001) during the study period. In detail, s1m1 (P < 0.05) and s1m2 (P < 0.01) increased, and s2m2 decreased (P < 0.001) in dyspeptic patients, while only s1m1 increased (P < 0.01) in peptic ulcer patients. Finally, few cases of s2m1 combination in both series were found. Our results show some unexpected aspects that require confirmation. In detail, the increased prevalence of potential more virulent H. pylori strains contrasts with peptic ulcer incidence reduction. PMID:18594981

De Francesco, Vincenzo; Margiotta, Marcella; Zullo, Angelo; Hassan, Cesare; Giorgio, Floriana; Zotti, Mariangela; Stoppino, Giuseppe; Bastianelli, Alessia; Diterlizzi, Francesco; Verderosa, Giovanna; Morini, Sergio; Panella, Carmine; Ierardi, Enzo

2009-01-01

66

An integrated sequence stratigraphy-organic geochemistry study of the Vaca Muerta petroleum systems, Neuquen Basin, Argentina  

SciTech Connect

This study shows that the Early Tithonian maximum flooding surface associated with the base of the Vaca Muerta Formation is an oil-prone marine condensed section which accumulated in the distal and shelfal parts of the basin during the maximum transgression. The overlying organic-rich sequences were deposited in a low-angle ramp setting in response to minor relative sea-level changes within an overall relative still-stand. Throughout the basin, the TOC content of the Vaca Muerta Formation decreases upward with the maximum TOC values correlating to the basal condensed section. Lateral variations in depositional setting along the Neuquen Embayment correlate to different source facies within the Vaca Muerta Formation. The distal source facies consist of multiple stacked marine condensed depositional sequences of all systems tracts. The upward decrease in TOC of the distal facies is gradual indicating that prolonged sediment starvation resulted in the accumulation of a thick organic-rich section. However, expulsion efficiency from the distal source facies was relatively low as it required high levels of thermal stress. The shelfal source facies consist of a single marine condensed section whose TOC content abruptly decreases upward due to the diluting effect of clastic highstand progradation. The low-angle shelfal setting favored widespread accumulation of the relatively thin shelfal facies, but coarser sediment interbedding increased expulsion efficiency from this facies. Kimmeridgian-incised valleys provided a regional migration pathway for hydrocarbons generated from both the distal and shelfal source facies.

Lara, M.E. [Lagoven, S.A., Caracas (Venezuela); Wavrek, D.A. [ERSI, Univ. of Utah, Salt Lake City (United States); Vines, R.; Laffitte, G.A. [and others

1996-08-01

67

Frequency of vacA, cagA and babA2 virulence markers in Helicobacter pylori strains isolated from Mexican patients with chronic gastritis  

PubMed Central

Background Helicobacter pylori has been strongly associated with chronic gastritis, peptic and duodenal ulcers, and it is a risk factor for gastric cancer. Three major virulence factors of H. pylori have been described: the vacuolating toxin (VacA), the cytotoxin-associated gene product (CagA) and the adhesion protein BabA2. Since considerable geographic diversity in the prevalence of H. pylori virulence factors has been reported, the aim of this work was to establish the H. pylori and vacA, cagA and babA2 gene status in 238 adult patients, from a marginal urban area of Mexico, with chronic gastritis. Methods H. pylori was identified in cultures of gastric biopsies by nested PCR. vacA and cagA genes were detected by multiplex PCR, whereas babA2 gene was identified by conventional PCR. Results H. pylori-positive biopsies were 143 (60.1%). All H. pylori strains were vacA+; 39.2% were cagA+; 13.3% were cagA+ babA2+ and 8.4% were babA2+. Mexican strains examined possessed the vacA s1, m1 (43.4%), s1, m2 (24.5%), s2, m1 (20.3%) and s2, m2 (11.9%) genotypes. Conclusion These results show that the Mexican patients suffering chronic gastritis we have studied had a high incidence of infection by H. pylori. Forty four percent (63/143) of the H. pylori strains analyzed in this work may be considered as highly virulent since they possessed two or three of the virulence markers analyzed: vacA s1 cagA babA2 (9.8%, 14/143), vacA s1 babA2 (4.9%, 7/143), and vacA s1 cagA (29.4%, 42/143). However, a statistically significant correlation was not observed between vacAs1, cagA and babA2 virulence markers (?2 test; P > 0.05).

Paniagua, Gloria Luz; Monroy, Eric; Rodriguez, Raymundo; Arroniz, Salvador; Rodriguez, Cristina; Cortes, Jose Luis; Camacho, Ausencio; Negrete, Erasmo; Vaca, Sergio

2009-01-01

68

Sensitive ecological areas and species inventory of Actun Chapat Cave, Vaca Plateau, Belize  

USGS Publications Warehouse

Cave ecosystems are considered one of the most poorly studied and fragile systems on Earth. Belize caves are no exception. This paper represents the first effort to synthesize information on both invertebrate and vertebrate observations from a Belize cave. Based on limited field research and a review of literature, we identified two ecologically sensitive areas, and developed a species inventory list containing 41 vertebrate and invertebrate morphospecies in Actun Chapat, Vaca Plateau, west-central Belize. Actun Chapat contains two ecologically sensitive areas: (1) a large multiple species bat roost, and (2) a subterranean pool containing troglobites and stygobites. The inventory list is a product of sporadic research conducted between 1973 and 2001. Ecological research in this cave system remains incomplete. An intensive systematic ecological survey of Actun Chapat with data collection over multiple seasons using a suite of survey techniques will provide a more complete inventory list. To minimize human disturbance to the ecologically sensitive areas, associated with ecotourism, we recommend limited to no access in the areas identified as "sensitive".

Wynne, J. J.; Pleytez, W.

2005-01-01

69

81Kr-Kr age and multiple cosmic-ray exposure history of the Vaca Muerta mesosiderite  

NASA Astrophysics Data System (ADS)

Noble gas isotopic compositions were measured for a eucritic pebble and bulk material of a silicate-metal mixture from the Vaca Muerta mesosiderite as well as pyroxene and plagioclase separated from the eucritic pebble by total melting and stepwise heating methods. Trapped noble gases were degassed completely by a high-temperature thermal event, probably at the formation of the Vaca Muerta parent body (VMPB). The presence of fissiogenic Xe isotopes from extinct 244Pu in the bulk samples might be a result of rapid cooling from an early high-temperature metamorphism. High concentrations of cosmogenic noble gases enabled us to determine precise isotopic ratios of cosmogenic Kr and Xe. Spallogenic Ne from Na and unique Ar isotopic compositions were observed. The 81Kr-Kr exposure age of 168 ± 8 Myr for the silicate pebble is distinctly longer than the age of 139 ± 8 Myr for the bulk samples. The precursor of the pebble had been irradiated on the surface of the VMPB for more than 60 Myr (first stage irradiation), with subsequent incorporation into bulk materials approximately 4 Gyr ago. The Vaca Muerta meteorite was excavated from the VMPB 140 Myr ago (second stage irradiation). Relative diffusion rates among the cosmogenic Ar, Kr, and Xe based on data obtained by stepwise heating indicate that Kr and Xe can be partially retained in pyroxene and plagioclase under the condition that resets the K-Ar system. This result supports the presence of fission Xe and of excess concentration of cosmogenic Kr, which could have survived the thermal event approximately 3.8 Gyr ago.

Bajo, Ken-Ichi; Nagao, Keisuke

2011-04-01

70

Low-density Lipoprotein Receptor-related Protein-1 (LRP1) Mediates Autophagy and Apoptosis Caused by Helicobacter pylori VacA*  

PubMed Central

In Helicobacter pylori infection, vacuolating cytotoxin (VacA)-induced mitochondrial damage leading to apoptosis is believed to be a major cause of cell death. It has also been proposed that VacA-induced autophagy serves as a host mechanism to limit toxin-induced cellular damage. Apoptosis and autophagy are two dynamic and opposing processes that must be balanced to regulate cell death and survival. Here we identify the low-density lipoprotein receptor-related protein-1 (LRP1) as the VacA receptor for toxin-induced autophagy in the gastric epithelial cell line AZ-521, and show that VacA internalization through binding to LRP1 regulates the autophagic process including generation of LC3-II from LC3-I, which is involved in formation of autophagosomes and autolysosomes. Knockdown of LRP1 and Atg5 inhibited generation of LC3-II as well as cleavage of PARP, a marker of apoptosis, in response to VacA, whereas caspase inhibitor, benzyloxycarbonyl-VAD-fluoromethylketone (Z-VAD-fmk), and necroptosis inhibitor, Necrostatin-1, did not inhibit VacA-induced autophagy, suggesting that VacA-induced autophagy via LRP1 binding precedes apoptosis. Other VacA receptors such as RPTP?, RPTP?, and fibronectin did not affect VacA-induced autophagy or apoptosis. Therefore, we propose that the cell surface receptor, LRP1, mediates VacA-induced autophagy and apoptosis.

Yahiro, Kinnosuke; Satoh, Mamoru; Nakano, Masayuki; Hisatsune, Junzo; Isomoto, Hajime; Sap, Jan; Suzuki, Hidekazu; Nomura, Fumio; Noda, Masatoshi; Moss, Joel; Hirayama, Toshiya

2012-01-01

71

The significance of cagA and vacA subtypes of Helicobacter pylori in the pathogenesis of inflammation and peptic ulceration  

Microsoft Academic Search

AIMS: To assess the significance of cagA and vacA subtypes of Helicobacter pylori in relation to inflammation and density of bacterial colonisation in vivo within a dyspeptic UK population. METHODS: Dyspeptic patients who were Helicobacter pylori positive had antral samples taken for histology and culture. Gastroduodenal pathology was noted. The grade of bacterial density and inflammation was assessed using the

M. C. Gunn; J. C. Stephens; J. A. Stewart; B. J. Rathbone; K. P. West

1998-01-01

72

Association of IL1B -511C/-31T haplotype and Helicobacter pylori vacA genotypes with gastric ulcer and chronic gastritis  

PubMed Central

Background The association between proinflammatory cytokine gene polymorphisms and gastric diseases related to Helicobacter pylori varies by population and geographic area. Our objective was to determine if the IL-1B -511 T>C and -31 C>T polymorphisms and H. pylori vacA genotypes are associated with risk of chronic gastritis and gastric ulcer in a Mexican population. Methods We conducted endoscopic studies in 128 patients with symptoms of dyspepsia. We took two biopsies from the body, antrum, or ulcer edge from each patient, and classified our histopathological findings according to the Sydney System. H. pylori infection and vacA genotyping were accomplished via PCR from total DNA of the gastric biopsies. We confirmed the presence of anti-H. pylori serum IgG and IgM in 102 control subjects. In both case subjects and control subjects, the IL-1B -511 T>C polymorphism was genotyped by PCR-RFLPs and the IL-1B -31 C>T polymorphism was genotyped by pyrosequencing. Results Sixty-two point seven (62.7%) of the 102 control subjects were H. pylori-seropositive. Among the case subjects, 100 were diagnosed with chronic gastritis and 28 with gastric ulcer. We found that 77% of the patients with chronic gastritis and 85.7% of the patients with gastric ulcer were H. pylori-positive. The predominant H. pylori genotype was vacA s1m1 (58.4%) and the most frequent subtype was vacA s1. The -511 TC, (rs16944 -511 T>C) genotype and the -511C allele were associated with chronic gastritis (OR = 3.1, 95% CI = 1.4-6.8 and OR = 3.0, 95% CI = 1.4-6.0, respectively). The subjects carrying -31T (rs1143627 -31 C>T) were found to be at a higher risk of having chronic gastritis (OR = 2.8, 95% CI = 1.3-5.8). The IL-1B -511C/-31T haplotype was associated with chronic gastritis (OR = 2.1, 95% CI = 1.2-3.8) but not with gastric ulcer. Conclusions The H. pylori vacA genotypes identified herein were similar to those reported for other regions of Mexico. The vacA s1m1 genotype was not associated with gastric ulcer. In the southern Mexican population, the IL-1B -511C and -31T alleles and the -511C/-31T and -511T/-31T haplotypes are associated with increased risk of chronic gastritis and gastric ulcer.

2010-01-01

73

Conservation of the cag pathogenicity island is associated with vacA alleles and gastroduodenal disease in South AfricanHelicobacter pylori isolates  

Microsoft Academic Search

BACKGROUNDThe development of clinically significant disease in South Africa is associated with the vacuolating cytotoxin gene (vacA) s1 genotype but not with the presence of the cytotoxin associated gene cagA. cagA occurs in >95% of South African isolates and is a variable marker for the entirecag pathogenicity island (PAI).AIMTo characterise the cagPAI in South African isolates and to investigate if

M Kidd; A J Lastovica; J C Atherton; J A Louw

2001-01-01

74

Analysis of Helicobacter pylori vacA andcagA genotypes and serum antibody profile in benign and malignant gastroduodenal diseases  

Microsoft Academic Search

Background—Helicobacter pylori species comprise different strains, cytotoxic and non-cytotoxic, which can be identified on the basis of their genomic pattern.Aims—(1) To evaluate the polymorphism of the vacA gene and to ascertain whether thecagA gene is present in patients with gastric adenocarcinoma. (2) To study the anti-H pylori antibody profile using western blotting.Patients—Twenty one patients with gastric adenocarcinoma and 71 with

D Basso; F Navaglia; L Brigato; M G Piva; A Toma; E Greco; F Di Mario; F Galeotti; G Roveroni; A Corsini; M Plebani

1998-01-01

75

Relationship between Helicobacter pylori iceA, cagA, and vacA Status and Clinical Outcome: Studies in Four Different Countries  

Microsoft Academic Search

There is continuing interest in identifying Helicobacter pylori virulence factors that might predict the risk for symptomatic clinical outcomes. It has been proposed that iceA and cagA genes are such markers and can identify patients with peptic ulcers. We compared H. pylori isolates from four countries, looking at the cagA and vacA genotypes, iceA alleles, and presentation of the infection.

YOSHIO YAMAOKA; TADASHI KODAMA; OSCAR GUTIERREZ; JONG G. KIM; KEI KASHIMA; DAVID Y. GRAHAM

1999-01-01

76

Differentiation history of the mesosiderite parent body: constraints from trace elements and manganese-chromium isotope systematics in Vaca Muerta silicate clasts  

NASA Astrophysics Data System (ADS)

We report here the results of a study of trace element microdistributions and 53Mn- 53Cr systematics in several basaltic and orthopyroxenitic clasts from the Vaca Muerta mesosiderite. Ion microprobe analyses of selected trace and minor element abundances in minerals of the silicate clasts indicate that, following igneous crystallization, these clasts underwent extensive metamorphic equilibration that resulted in intra- and inter-grain redistribution of elements. There is also evidence in the elemental microdistributions that these clasts were subsequently affected to varying degrees by alteration resulting from redox reactions involving the indigenous silicates and externally derived reducing agents (such as phosphorus, derived from the mesosiderite metal) at the time of metal-silicate mixing. Furthermore, our results suggest that the varying degrees of alteration by redox reactions recorded in the different clasts were most likely facilitated by different degrees of remelting induced by heating during the metal-silicate mixing event. After taking into account the effects of these postmagmatic secondary processes, comparison of the trace and minor element concentrations and distributions in minerals of basaltic and orthopyroxenitic clasts with those of noncumulate eucrites and diogenites, respectively, suggests that the primary igneous petrogenesis, including parent magma and source compositions, of Vaca Muerta silicates were similar to those of achondritic meteorites of the Howardite-Eucrite-Diogenite (HED) association. Internal 53Mn- 53Cr isochrons obtained for two basaltic (pebble 16 and 4679) and two orthopyroxenitic (4659 and 4670) clasts show that chromium isotopes are equilibrated within each clast. Nevertheless, just as for noncumulate eucrites and diogenites, 53Cr excesses in whole-rock samples of the basaltic clasts (˜1.01 ? in pebble 16; ˜1.07 ? in 4679) are significantly higher than in the orthopyroxene-rich clasts (˜0.62 ? in 4659; ˜0.53 ? in 4670). As in the case of the HED parent body, this suggests that Mn/Cr fractionation in the parent body of the Vaca Muerta silicate clasts occurred very early in the history of the solar system, when 53Mn was still extant. However, the slope of the 53Mn- 53Cr isochron defined by the whole-rock samples of Vaca Muerta clasts (corresponding to a 53Mn/ 55Mn ratio of 3.3 ± 0.6 × 10 -6) is distinctly lower than that defined by the HED whole-rock samples (corresponding to a 53Mn/ 55Mn ratio of 4.7 ± 0.5 × 10 -6), indicating that the global Mn/Cr fractionation event that established mantle source reservoirs on the parent body of the Vaca Muerta silicate clasts occurred ˜2 Ma after a similar event on the HED parent body.

Wadhwa, M.; Shukolyukov, A.; Davis, A. M.; Lugmair, G. W.; Mittlefehldt, D. W.

2003-12-01

77

Association of H. pylori virulence genes CagA, VacA and UreAB with ulcer and nonulcer diseases in Iranian population.  

PubMed

To evaluate the association of virulence genes CagA, VacA and UreAB of H. pylori with the development of different gastric disorders, polymerase chain reaction was performed on H. pylori organisms isolated from biopsy samples of stomach of patients with ulcerative disease and nonulcerative disease. The difference between the groups was statistically significant (p < 0.05) only for VacA gene. We detected 8 phenotypes, characterized as CagA(+)-VacA(-)-UreAB(+) (phe 1), CagA(-)-VacA(-)-UreAB(-) (phe 2), CagA(+)-VacA(+)-UreAB(-) (phe 3), CagA(+)-VacA(-)-UreAB(+) (phe 4), CagA(-)-VacA(+)-UreAB(+) (phe 5), CagA(+)-VacA(-)-UreAB(-) (phe 6), CagA(-)-VacA(+)-UreAB(-) (phe 7), CagA(-)VacA(-)-UreAB(+) (phe 8). The prevalence of phenotype 1 was significantly higher in the patients with UD than that in the patients with NUD (p < 0.05). These results suggest that in the population under our study, being infected by a H. pylori strain with the genotype CagA(+)-VacA(+)-UreAB(+) may be associated with an increased risk of acquiring an ulcer disease. PMID:19069914

Farshad, Shohreh; Alborzi, Abdolvahab; Abbasian, Amin

2007-04-15

78

Genetic Analysis of cagA and vacA Genes in Helicobacter Pylori Isolates and Their Relationship with Gastroduodenal Diseases in the West of Iran  

PubMed Central

Background Helicobacter pylori have different virulence factors which are associated with several gastroduodenal diseases; however, this association is variable in different geographical regions. Data of genotypes of Iranian H. pylori isolates are few. Objectives The aim of the current study was to investigate the cagA/vacA genotypes of Helicobacter pylori isolates and determine the relationship between these genotypes with respect to different gastric disorders in patients of Chaharmahalo Bakhtiarian. Materials and Methods In this cross-sectional study, gastric biopsies were taken from 200 patients with gastrodoudenal diseases. Histopathological features were recognized by specialist. The samples were subjected to PCR for detection and identification of ureC, cagA and vacA genes. Results The frequency of the vacA genotypes, sa1/m1, s1a/m1b, s1a/m2, s1b/m1a, s1b/m1b, s1b/m2, s1c/m1a, s1c/m1b, s1c/m2, s2/m1a, s2/m1b and s2/m2 were 27(6.6%), 8(4.3%), 45(28.04%), 7(3.7%), 5(2.5%), 10 (6.1%), 12 (7.4%), 4 (2.5%), 18(11%), 6(3.7%), 0 and 22(13.5%) respectively. The cagA gene was detected in 92% of strains. Based on our findings, it seemed that cagPAI and vacA s1 genotypes were associated with some gastric disorders in patients with H. pylori. In this region, the isolates carrying s1a/m2 were the most prevalent. Conclusions We found considerable relationship between s1a/m1a, s1a/m2, s2/m2 and s1c/m1a and some gastric disorders. Further studies about the role of H. pylori virulence factors and gastric disorders were recommended.

Souod, Negar; Kargar, Mohammad; Doosti, Abbas; Ranjbar, Reza; Sarshar, Meysam

2013-01-01

79

Helicobacter pylori cagA Status and s and m Alleles of vacA in Isolates from Individuals with a Variety of H. pylori-Associated Gastric Diseases  

Microsoft Academic Search

The cagA gene was detected in 100% of 16 Helicobacter pylori isolates from patients with gastric carcinoma versus 78% of 18 isolates from patients with duodenal ulcers (P 5 0.344) and only 64% of 22 isolates from patients with gastritis only (P 5 0.005) in Brazil. Also, there was a significant association between isolation of cagA 1 s1-type vacA H.

DOLORES G. EVANS; DULCIENE M. M. QUEIROZ; EDILBERTO N. MENDES; DOYLE J. EVANS

1998-01-01

80

Analysis of the expression of CagA and VacA and the vacuolating activity in 167 isolates from patients with either peptic ulcers or non-ulcer dyspepsia  

Microsoft Academic Search

Objectives: The goals of this study were: 1) to examine the prevalence of cytotoxin-associated protein (CagA), vacuolating cytotoxin (VacA), and the vacuolating cytotoxin activity (VCA) in vitro of infecting Helicobacter pylori isolates and 2) to clarify the relation between the expression of these virulence factors and the occurrence of peptic ulceration. Methods: One hundred sixty-seven clinical isolates of H. pylori

Tohru Takata; Shuji Fujimoto; Keizo Anzai; Takuro Shirotani; Mitsuo Okada; Yoshiro Sawae; Junko Ono

1998-01-01

81

Helicobacter pylori VacA Suppresses Lactobacillus acidophilus-Induced Interferon Beta Signaling in Macrophages via Alterations in the Endocytic Pathway  

PubMed Central

ABSTRACT Helicobacter pylori causes chronic gastritis and avoids elimination by the immune system of the infected host. The commensal bacterium Lactobacillus acidophilus has been suggested to exert beneficial effects as a supplement during H. pylori eradication therapy. In the present study, we applied whole-genome microarray analysis to compare the immune responses induced in murine bone marrow-derived macrophages (BMDMs) stimulated with L. acidophilus, H. pylori, or both bacteria in combination. While L. acidophilus induced a Th1-polarizing response characterized by high expression of interferon beta (IFN-?) and interleukin 12 (IL-12), H. pylori strongly induced the innate cytokines IL-1? and IL-1?. In BMDMs prestimulated with L. acidophilus, H. pylori blocked the expression of L. acidophilus-induced IFN-? and IL-12 and suppressed the expression of key regulators of the Rho, Rac, and Cdc42 GTPases. The inhibition of L. acidophilus-induced IFN-? was independent of H. pylori viability and the virulence factor CagPAI; however, a vacuolating cytotoxin (vacA) mutant was unable to block IFN-?. Confocal microscopy demonstrated that the addition of H. pylori to L. acidophilus-stimulated BMDMs redirects intracellular processing, leading to an accumulation of L. acidophilus in the endosomal and lysosomal compartments. Thus, our findings indicate that H. pylori inhibits the development of a strong Th1-polarizing response in BMDMs stimulated with L. acidophilus by blocking the production of IFN-? in a VacA-dependent manner. We suggest that this abrogation is caused by a redirection of the endocytotic pathway in the processing of L. acidophilus.

Weiss, Gudrun; Forster, Sam; Irving, Aaron; Tate, Michelle; Ferrero, Richard L.; Hertzog, Paul; Fr?kiaer, Hanne; Kaparakis-Liaskos, Maria

2013-01-01

82

Analysis of Expression of CagA and VacA Virulence Factors in 43 Strains ofHelicobacter pyloriReveals that Clinical Isolates Can Be Divided into Two Major Types and that CagA Is Not Necessary for Expression of the Vacuolating Cytotoxin  

Microsoft Academic Search

Colonization of the mucosa of the stomach and the duodenum by Helicobacter pylori is the major cause of acute and chronic gastroduodenal pathologies in humans. Duodenal ulcer formation strongly correlates with the expression of an antigen (CagA) that is usually coexpressed with the vacuolating cytotoxin (VacA), a protein that causes ulceration in the stomach of mice. However, the relationship between

ZHAOYING XIANG; STEFANO CENSINI; PIETRO F. BAYELI; JOHN L. TELFORD; NATALE FIGURA; RINO RAPPUOLI; ANDANTONELLO COVACCI

83

Sedimentology and sequence stratigraphy of a Tithonian-Valanginian carbonate ramp (Vaca Muerta Formation): A misunderstood exceptional source rock in the Southern Mendoza area of the Neuquén Basin, Argentina  

NASA Astrophysics Data System (ADS)

The Vaca Muerta Formation (early Tithonian-early Valanginian) is a rhythmic succession of marls and limestones, cropping out in the Neuquén Basin, west-central Argentina. This lithostratigraphic unit was traditionally interpreted as basinal to slope deposits. Detailed facies analysis allows to differentiate seven facies associations, representing basinal to middle ramp facies of a homoclinal ramp system prograding westward from the eastern margin, and slope facies attributed to a distally steepened ramp system that progrades eastward from the Andean volcanic arc in the west. Two sequence hierarchies are recognized: five third order depositional sequences, and fifteen fourth order high-frequency sequences. Fluctuations in organic matter content within the Vaca Muerta Formation suggest relationship with depositional sequences, finding the highest values associated with transgressive system tracts. This work represents an important advance in the understanding of the sedimentary and stratigraphic evolution of this exceptional unconventional reservoir. Our sequence stratigraphic approach contributes to the understanding of the relationship between organic matter, facies, and sea-level changes.

Kietzmann, Diego A.; Palma, Ricardo M.; Riccardi, Alberto C.; Martín-Chivelet, Javier; López-Gómez, José

2014-04-01

84

Funcionalidade de sistemas colinergicos em ratos previamente tratados com triiodotironina. (Function of Colinergic systems in rats pre-treated with triiodothyronine).  

National Technical Information Service (NTIS)

In order to investigate the influence of experimental hyperthyroidism on cholinergic activity, rats were injected daily, during 1, 5, 19 or 20 days, with triiodothyronine (0 to 100 ug/kg, s.c.). The hiperthyroidism was evaluated by the decrease of the bod...

O. M. S. Almeida

1990-01-01

85

Impactación de abomaso en vacas de cría Abomasal impaction in breed cows  

Microsoft Academic Search

Summary In this work we describe an outbreak of dietary abomasal impaction occurred in a herd of pregnant cows during June-July 2006 in a country placed in Buenos Aires Province, Argentina. It was caused by ad libitum intake of oat straw hay. The clinical findings were lost of corporal score, moderate distension of the abdomen, unsteady gait, weakness, recumbence, dehydration

Cantón G; Odriozola E; Giannitti F; Fernández M; Spinelli R

86

Distinct Variants of Helicobacter pylori cagA Are Associated with vacA Subtypes  

Microsoft Academic Search

The diversity of the cytotoxin-associated gene (cagA )o fHelicobacter pylori was analyzed in 45 isolates obtained from nine countries. We examined variation in the 5* end of the cagA open reading frame as determined by PCR and sequencing. Phylogenetic analysis revealed the existence of at least two distinct types of cagA. One variant (cagA1) was found exclusively in strains from

LEEN-JAN VAN DOORN; C EU FIGUEIREDO; RICARDO SANNA; MARTIN J. BLASER; WIM G. V. QUINT

1999-01-01

87

Morfologia do fruto, semente e plântula do Mororó (ou pata de vaca) - Bauhína forficata Linn  

Microsoft Academic Search

The mororó or cow paw (Bauhinia forficata Linn) presents great importance for the savanna paraibana, so much for the home-made medicine as for its economical value, in spite of it is threatened of extinction according to caririzeiros of the area. It was aimed at the morphologic knowledge of the fruit, seed and plantule of this species. The fruits were collected

Giselle Medeiros; Humberto Silva; Myrthis Virginia; Alves de Almeida; Mário Luiz Farias; Patrícia de Lima Martins

88

Source rock characteristics, Los Molles and Vaca Muerta shales, Neuquen basin, west-central Argentina  

Microsoft Academic Search

Major hydrocarbon-producing trends of the Neuquen basin occur along its northeastern margin (Eastern Shelf) and along an east-west-trending structural high in the southern half of the basin (Neuquen Dorsal). Sediment thickness increases northward from the Neuquen Dorsal and westward from the Eastern Shelf into the Neuquen Embayment, a region that has been relatively unproductive for hydrocarbons. Major source rocks are

Ralph L. Kugler

1985-01-01

89

Heterogeneity in the Helicobacter pylori vacA and cagA genes: association with gastroduodenal disease in South Africa?  

Microsoft Academic Search

BACKGROUNDHelicobacter pylori infection is universally associated with gastritis, but only sometimes with clinically significant disease. Candidate virulence markers seem to be useful in identifying the pathogenic infections in some populations.AIMSTo investigate the association between putative virulence markers and disease in an African population.METHODSFifty nineH pylori strains isolated from dyspeptic patients (11 with peptic ulceration, eight with gastric adenocarcinoma, and 28

M Kidd; A J Lastovica; J C Atherton; J A Louw

1999-01-01

90

Introduction of Unmarked Mutations in theHelicobacter pylori vacA Gene with a Sucrose Sensitivity Marker  

Microsoft Academic Search

Research onHelicobacter pylorihas been hindered by the lack of useful genetic tools. Using thesacBgene of Bacillus subtilis, we developed a sucrose-based counterselection system that allows introduction of unmarked mutations inH. pylori.Akan-sacBcassette, consisting of thesacBgene expressed from theH. pyloriflagellin promoterandthekanamycinresistancemodule,wasintroducedbyhomologousrecombinationintoatargetH. pylori gene. The resultant strains were sucrose sensitive and kanamycin resistant. Following transformation with a mutated allele, growth in sucrose-containing medium

MICHAEL COPASS; GUIDO GRANDI; ANDRINO RAPPUOLI

1997-01-01

91

Newly Discovered Paleocene and Eocene Rocks near Fairfield, California, and Correlation with Rocks in Vaca Valley and the So-Called Martinez Formation or Stage  

USGS Publications Warehouse

Discovery of a 3-foot thick sandstone bed with abundant Turritellid gastropods of late Paleocene age about 4 miles northeast of Fairfield and on the southwest flank of Cement Hill, Solano County provides an opportunity to reevaluate the relationships of lower Tertiary formations in this part of California. Cement Hill is named for travertine deposits in and on top of sandstone of Late Cretaceous age. In this report, the current study area where the Paleocene fossils were recently discovered is referred to as lower Cement Hill and is located in section 7 of the U.S. Geological Survey Fairfield North 7.5-minute quadrangle, Township 5 North, Range 1 West. Lower Cement Hill is about 23 miles north of the so-called Martinez 'formation' or stage area (Weaver and others, 1941) of late Paleocene age near Martinez. The Martinez 'formation' and stage have played a significant role in the development of early Tertiary stratigraphy in this part of California. The discovery of correlative rocks at Cement Hill was unsuspected and may be helpful in defining the extent of this so-called formation or stage. Coccolith identification and correlations are by David Bukry, foraminifer identifications and correlations by Alvin Almgren and Kristin McDougall, gastropod identification and correlation by LouElla Saul, and Radiolaria identifications and correlations are by Annika Sanfilippo.

Brabb, Earl E.; Ristau, Donn; Bukry, David; McDougall, Kristin; Almgren, Alvin A.; Saul, LouElla; Sanfilippo, Annika

2008-01-01

92

76 FR 12098 - Combined Notice of Filings No. 1  

Federal Register 2010, 2011, 2012, 2013

...2011 Docket Numbers: ER11-2600-001 Applicants: CalPeak Power--Vaca Dixon LLC Description: CalPeak Power--Vaca Dixon LLC submits tariff filing per 35: Vaca Dixon--Supplement to Notice of Non-Material Change to be effective...

2011-03-04

93

Vacuolating Cytotoxin of Helicobacter pylori Plays a Role during Colonization in a Mouse Model of Infection  

Microsoft Academic Search

Helicobacter pylori, the causative agent of gastritis and ulcer disease in humans, secretes a toxin called VacA (vacuolating cytotoxin) into culture supernatants. VacA was initially characterized and purified on the basis of its ability to induce the formation of intracellular vacuoles in tissue culture cells. H. pylori strains possessing different alleles of vacA differ in their ability to express active

NINA R. SALAMA; GLEN OTTO; LUCY TOMPKINS; STANLEY FALKOW

2001-01-01

94

Multiple Gene Status in Helicobacter pylori Strains and Risk of Gastric Cancer Development  

Microsoft Academic Search

Background\\/Aim: The identification of the vacA intermediate region has provided new insights into the role of vacA heterogeneity in relation to gastro-duodenal pathogenesis. The aim of this study was to assess vacA polymorphism in Iranian Helicobacter pylori strains and its association with cagA as a major virulence determinant, gastric histopathology and disease. Methods:vacA polymorphism and serum antibody responses were studied

Masoumeh Douraghi; Yeganeh Talebkhan; Hojjat Zeraati; Fatemeh Ebrahimzadeh; Azin Nahvijoo; Arman Morakabati; Masoud Ghafarpour; Maryam Esmaili; Maryam Bababeik; Akbar Oghalaie; Nasser Rakhshani; Mahmoud Eshagh Hosseini; Mohammad Ali Mohagheghi; Marjan Mohammadi

2009-01-01

95

The Helicobacter pylori Vacuolating Toxin Inhibits T Cell Activation by Two Independent Mechanisms  

Microsoft Academic Search

Helicobacter pylori toxin, VacA, damages the gastric epithelium by erosion and loosening of tight junctions. Here we report that VacA also interferes with T cell activation by two different mech- anisms. Formation of anion-specific channels by VacA prevents calcium influx from the extracellular milieu. The transcription factor NF-AT thus fails to translocate to the nucleus and activate key cytokine genes.

Marianna Boncristiano; Silvia Rossi Paccani; Silvia Barone; Cristina Ulivieri; Laura Patrussi; Dag Ilver; Amedeo Amedei; Mario Milco D'Elios; John L. Telford; Cosima T. Baldari

96

Functional properties of the p33 and p55 domains of the Helicobacter pylori vacuolating cytotoxin.  

PubMed

Helicobacter pylori secretes an 88-kDa vacuolating cytotoxin (VacA) that may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. VacA cytotoxic activity requires assembly of VacA monomers into oligomeric structures, formation of anion-selective membrane channels, and entry of VacA into host cells. In this study, we analyzed the functional properties of recombinant VacA fragments corresponding to two putative VacA domains (designated p33 and p55). Immunoprecipitation experiments indicated that these two domains can interact with each other to form protein complexes. In comparison to the individual VacA domains, a mixture of the p33 and p55 proteins exhibited markedly enhanced binding to the plasma membrane of mammalian cells. Furthermore, internalization of the VacA domains was detected when cells were incubated with the p33/p55 mixture but not when the p33 and p55 proteins were tested individually. Incubation of cells with the p33/p55 mixture resulted in cell vacuolation, whereas the individual domains lacked detectable cytotoxic activity. Interestingly, sequential addition of p55 followed by p33 resulted in VacA internalization and cell vacuolation, whereas sequential addition in the reverse order was ineffective. These results indicate that both the p33 and p55 domains contribute to the binding and internalization of VacA and that both domains are required for vacuolating cytotoxic activity. Reconstitution of toxin activity from two separate domains, as described here for VacA, has rarely been described for pore-forming bacterial toxins, which suggests that VacA is a pore-forming toxin with unique structural properties. PMID:15817461

Torres, Victor J; Ivie, Susan E; McClain, Mark S; Cover, Timothy L

2005-06-01

97

Dinâmica da eliminação de ovos por nematódeos gastrintestinais, durante o periparto de vacas de corte, no Estado do Pará Parasitic dynamics of gastrointestinal nematode infection in the periparturient period of beef cattle in the State of Para  

Microsoft Academic Search

The experiment was conducted to investigate the dynamics of infection by gastrointestinal nematodes during the periparturition period in cows. One hundred and six beef cows were divided into two groups: G1 was formed by 42 cows of one and two parturitions, and G2 by 76 cows of three or more parturitions. From the 120 days pre partum until the 90

Rinaldo Batista Viana; Jean Pierre Brasileiro Bispo; Cláudio Vieira de Araújo; Raimundo Nonato Moraes Benigno; Bruno Moura Monteiro; Solange Maria Gennari

2009-01-01

98

USO DE UNA SOLUCIÓN ANTISÉPTICA SOLA O ASOCIADA CON UN PROGESTÁGENO EN EL TRATAMIENTO DE LA VACA REPETIDORA DE SERVICIO Treatment of Repeat Breeders Cows with Antiseptic Solutions Alone or Associated with Progestins  

Microsoft Academic Search

In Maracaibo lake basin, around 20% of crossbred dual pur- pose cows are considered repeat breeders, having long post- partum intervals and impeding the main farm objective of one calf per cow, per year. The aim of this study was to evaluate the effect of the use of an intrauterine infusion with Listerine ® alone or associated with progestins for

2005-01-01

99

Vacuolating Cytotoxin and Variants in Atg16L1 that Disrupt Autophagy Promote Helicobacter pylori Infection in Humans  

PubMed Central

Background & Aims The Helicobacter pylori toxin vacuolating cytotoxin (VacA) promotes gastric colonization and its presence (VacA+) is associated with more-severe disease. The exact mechanisms by which VacA contributes to infection are unclear. We previously found that limited exposure to VacA induces autophagy of gastric cells, which eliminates the toxin; we investigated whether autophagy serves as a defense mechanism against H pylori infection. Methods We investigated the effect of VacA on autophagy in human gastric epithelial cells (AGS) and primary gastric cells from mice. Expression of p62, a marker of autophagy, was also assessed in gastric tissues from patients infected with toxigenic (VacA+) or nontoxigenic strains. We analyzed the effect of VacA on autophagy in peripheral blood monocytes obtained from subjects with different genotypes of ATG16L1, which regulates autophagy. We performed genotyping for ATG16L1 in two cohorts of infected and uninfected subjects. Results Prolonged exposure of AGS and mouse gastric cells to VacA disrupted induction of autophagy in response to the toxin, because the cells lacked cathepsin-D in autophagosomes. Loss of autophagy resulted in the accumulation of p62 and reactive oxygen species. Gastric biopsies samples from patients infected with VacA+, but not nontoxigenic strains of H pylori, had increased levels of p62. Peripheral blood monocytes isolated from individuals with polymorphisms in ATG16L1 that increase susceptibility to Crohn's disease had reduced induction of autophagy in response to VacA+ compared to cells from individuals that did not have these polymorphisms. The presence of the ATG16L1 Crohn’s disease risk variant increased susceptibility to H pylori infection in 2 separate cohorts. Conclusions Autophagy protects against infection with H pylori; the toxin VacA disrupts autophagy to promote infection, which could contribute to inflammation and eventual carcinogenesis.

Raju, D; Hussey, S; Ang, M; Terebiznik, M.R.; Sibony, M; Galindo-Mata, E; Gupta, V; Blanke, S.R.; Delgado, A; Romero-Gallo, J; Ramjeet, M; Mascarenhas, H; Peek, R.M.; Correa, P; Streutker, C; Hold, G; Kunstmann, E; Yoshimori, T; Silverberg, M. S.; Girardin, S.E.; Philpott, D.J.; El Omar, E; Jones, N.L.

2012-01-01

100

Plasma Membrane Cholesterol Modulates Cellular Vacuolation Induced by the Helicobacter pylori Vacuolating Cytotoxin  

PubMed Central

The Helicobacter pylori vacuolating cytotoxin (VacA) induces the degenerative vacuolation of mammalian cells both in vitro and in vivo. Here, we demonstrate that plasma membrane cholesterol is essential for vacuolation of mammalian cells by VacA. Vacuole biogenesis in multiple cell lines was completely blocked when cholesterol was extracted selectively from the plasma membrane by using ?-cyclodextrins. Moreover, increasing plasma membrane cholesterol levels strongly potentiated VacA-induced vacuolation. In contrast, inhibiting de novo biosynthesis of cholesterol with lovastatin or compactin had no detectable effect on vacuolation. While depletion of plasma membrane cholesterol has been shown to interfere with both clathrin-mediated endocytosis and caveola-dependent endocytosis, neither of these two internalization pathways was found to be essential for vacuolation of cells by VacA. Depleting plasma membrane cholesterol attenuated the entry of VacA into HeLa cells. In addition, ?-cyclodextrin reagents blocked vacuolation of cells that were either preloaded with VacA or had VacA directly expressed within the cytosol. Collectively, our results suggest that plasma membrane cholesterol is important for both the intoxication mechanism of VacA and subsequent vacuole biogenesis.

Patel, Hetal K.; Willhite, David C.; Patel, Rakhi M.; Ye, Dan; Williams, Christopher L.; Torres, Eric M.; Marty, Kent B.; MacDonald, Robert A.; Blanke, Steven R.

2002-01-01

101

Measurement of aerosol sulfuric acid: 1. Experimental setup, characterization, and calibration of a novel mass spectrometric system  

NASA Astrophysics Data System (ADS)

An instrument for the direct in situ measurement of aerosol sulfuric acid in the atmosphere has been developed, characterized and calibrated. The instrument termed Volatile Aerosol Component Analyzer (VACA) utilizes chemical ionization mass spectrometry technique for the detection of sulfuric acid. Prior to the mass spectrometric identification the sample flow is heated, and sulfuric acid is evaporated from the aerosol. The VACA system is characterized as a function of temperature, residence time in the flow reactor, aerosol size, and chemical composition. A unit consisting of an aerosol generator, a differential mobility analyzer, a hygrometer, and a condensation nuclei counter is used to calibrate the VACA instrument.

Curtius, J.; Arnold, F.

2001-12-01

102

A Helicobacter pylori Vacuolating Toxin Mutant That Fails To Oligomerize Has a Dominant Negative Phenotype  

Microsoft Academic Search

Received 11 November 2005\\/Returned for modification 5 December 2005\\/Accepted 23 December 2005 Most Helicobacter pylori strains secrete a toxin (VacA) that causes massive vacuolization of target cells and which is a major virulence factor of H. pylori. The VacA amino-terminal region is required for the induction of vacuolization. The aim of the present study was a deeper understanding of the

Christophe Genisset; Cesira L. Galeotti; Pietro Lupetti; David Mercati; David A. G. Skibinski; Silvia Barone; Roberto Battistutta; Marina de Bernard; John L. Telford

2006-01-01

103

Helicobacter pylori vacuolating toxin forms anion-selective channels in planar lipid bilayers: possible implications for the mechanism of cellular vacuolation.  

PubMed Central

The Helicobacter pylori VacA toxin plays a major role in the gastric pathologies associated with this bacterium. When added to cultured cells, VacA induces vacuolation, an effect potentiated by preexposure of the toxin to low pH. Its mechanism of action is unknown. We report here that VacA forms anion-selective, voltage-dependent pores in artificial membranes. Channel formation was greatly potentiated by acidic conditions or by pretreatment of VacA at low pH. No requirement for particular lipid(s) was identified. Selectivity studies showed that anion selectivity was maintained over the pH range 4.8-12, with the following permeability sequence: Cl- approximately HCO3- > pyruvate > gluconate > K+ approximately Li+ approximately Ba2+ > NH4+. Membrane permeabilization was due to the incorporation of channels with a voltage-dependent conductance in the 10-30 pS range (2 M KCl), displaying a voltage-independent high open probability. Deletion of the NH2 terminus domain (p37) or chemical modification of VacA by diethylpyrocarbonate inhibited both channel activity and vacuolation of HeLa cells without affecting toxin internalization by the cells. Collectively, these observations strongly suggest that VacA channel formation is needed to induce cellular vacuolation, possibly by inducing an osmotic imbalance of intracellular acidic compartments.

Tombola, F; Carlesso, C; Szabo, I; de Bernard, M; Reyrat, J M; Telford, J L; Rappuoli, R; Montecucco, C; Papini, E; Zoratti, M

1999-01-01

104

Endoplasmic reticulum stress contributes to Helicobacter pylori VacA-induced apoptosis.  

PubMed

Vacuolating cytotoxin A (VacA) is one of the important virulence factors produced by H. pylori. VacA induces apoptotic cell death, which is potentiated by ammonia. VacA also causes cell death by mitochondrial damage, via signaling pathways that are not fully defined. Our aim was to determine whether endoplasmic reticulum (ER) stress is associated with VacA-induced mitochondrial dysfunction and apoptosis. We found that C/EBP homologous protein (CHOP), a key signaling protein of ER stress-induced apoptosis, was transcriptionally up-regulated following incubation of gastric epithelial cells with VacA. The effect of VacA on CHOP induction was significantly enhanced by co-incubation with ammonium chloride. Phosphorylation of eukaryotic initiation factor 2 (eIF2)-alpha, which is known to occur downstream of the ER stress sensor PKR-like ER-localized eIF2-alpha kinase (PERK) and to regulate CHOP expression, was also observed following incubation with VacA in the presence of ammonium chloride. Knockdown of CHOP by siRNA resulted in inhibition of VacA-induced apoptosis. Further studies showed that silencing of the PERK gene with siRNA attenuated VacA-mediated phosphorylation of eIF2-alpha, CHOP induction, expression of BH3-only protein Bim and Bax activation, and cell death induced by VacA with ammonium chloride, indicating that ER stress may lead to mitochondrial dysfunction during VacA-induced toxicity. Activation of ER stress and up-regulation of BH3-only proteins were also observed in human H. pylori-infected gastric mucosa. Collectively, this study reveals a possible association between VacA-induced apoptosis in gastric epithelial cells, and activation of ER stress in H. pylori-positive gastric mucosa. PMID:24349255

Akazawa, Yuko; Isomoto, Hajime; Matsushima, Kayoko; Kanda, Tsutomu; Minami, Hitomi; Yamaghchi, Naoyuki; Taura, Naota; Shiozawa, Ken; Ohnita, Ken; Takeshima, Fuminao; Nakano, Masayuki; Moss, Joel; Hirayama, Toshiya; Nakao, Kazuhiko

2013-01-01

105

Prevalence of genotypes in Helicobacter pyloriisolates from patients in eastern Turkey and the association of these genotypes with clinical outcome  

PubMed Central

There is not much information available regarding the prevalence of the genotypes of Helicobacter pylori isolates in Turkey, particularly in eastern Turkey. The aims of this study were to detect the prevalence of different genotypes of H. pylori in Turkish patients with gastrointestinal complaints and to determine the relationship of these genotypes with clinical outcome and sex. One hundred forty H. pylori isolates were examined for the presence of its genotypes by the PCR. We found that the prevalence of vacAs1,vacAs2, cagA, cagE, iceA1, iceA2 and babA2 genes were 88.6%, 11.4%, 71.4%, 35.7%, 41.4%, 58.6%, and 62.1%, respectively. The most predominant vacA subtype was s1a (81.4%). The most vacA allelic combination detected were vacAs1m1 (65.2%) and s1m2 (53.9%) in patients with peptic ulcer and gastritis, respectively. The only vacAs1 isolate was significantly associated with gastritis and peptic ulcer (p<0.05). The vacAs1a, ml, slml and babA2 genes were significantly associated with peptic ulcer (p<0.05), whereas m2 gene was significantly associated with only gastritis (p<0.05). The difference between sex and genotypes was statistically significant among the cagA,vacAs1, iceA2 and babA2 genes. This study reported for the first time the prevalence of H. pylori genotypes in patients with gastrointestinal complaints in eastern Turkey. Further studies are needed to understand epidemiological importance of the genotypes of H. pylori isolates in this region and the association between the virulence genes and clinical outcome in different regions.

Ozbey, Gokben; Aygun, Cem

2012-01-01

106

Endoplasmic Reticulum Stress Contributes to Helicobacter Pylori VacA-Induced Apoptosis  

PubMed Central

Vacuolating cytotoxin A (VacA) is one of the important virulence factors produced by H. pylori. VacA induces apoptotic cell death, which is potentiated by ammonia. VacA also causes cell death by mitochondrial damage, via signaling pathways that are not fully defined. Our aim was to determine whether endoplasmic reticulum (ER) stress is associated with VacA-induced mitochondrial dysfunction and apoptosis. We found that C/EBP homologous protein (CHOP), a key signaling protein of ER stress-induced apoptosis, was transcriptionally up-regulated following incubation of gastric epithelial cells with VacA. The effect of VacA on CHOP induction was significantly enhanced by co-incubation with ammonium chloride. Phosphorylation of eukaryotic initiation factor 2 (eIF2)-alpha, which is known to occur downstream of the ER stress sensor PKR-like ER-localized eIF2-alpha kinase (PERK) and to regulate CHOP expression, was also observed following incubation with VacA in the presence of ammonium chloride. Knockdown of CHOP by siRNA resulted in inhibition of VacA-induced apoptosis. Further studies showed that silencing of the PERK gene with siRNA attenuated VacA-mediated phosphorylation of eIF2-alpha, CHOP induction, expression of BH3-only protein Bim and Bax activation, and cell death induced by VacA with ammonium chloride, indicating that ER stress may lead to mitochondrial dysfunction during VacA-induced toxicity. Activation of ER stress and up-regulation of BH3-only proteins were also observed in human H. pylori-infected gastric mucosa. Collectively, this study reveals a possible association between VacA-induced apoptosis in gastric epithelial cells, and activation of ER stress in H. pylori-positive gastric mucosa.

Akazawa, Yuko; Isomoto, Hajime; Matsushima, Kayoko; Kanda, Tsutomu; Minami, Hitomi; Yamaghchi, Naoyuki; Taura, Naota; Shiozawa, Ken; Ohnita, Ken; Takeshima, Fuminao; Nakano, Masayuki; Moss, Joel; Hirayama, Toshiya; Nakao, Kazuhiko

2013-01-01

107

Analysis of a ?-helical region in the p55 domain of Helicobacter pylori vacuolating toxin  

PubMed Central

Background Helicobacter pylori is a gram-negative bacterium that colonizes the human stomach and contributes to the development of gastric cancer and peptic ulcer disease. VacA, a toxin secreted by H. pylori, is comprised of two domains, designated p33 and p55. Analysis of the crystal structure of the p55 domain indicated that its structure is predominantly a right-handed parallel ?-helix, which is a characteristic of autotransporter passenger domains. Substitution mutations of specific amino acids within the p33 domain abrogate VacA activity, but thus far, it has been difficult to identify small inactivating mutations within the p55 domain. Therefore, we hypothesized that large portions of the p55 domain might be non-essential for vacuolating toxin activity. To test this hypothesis, we introduced eight deletion mutations (each corresponding to a single coil within a ?-helical segment spanning VacA amino acids 433-628) into the H. pylori chromosomal vacA gene. Results All eight of the mutant VacA proteins were expressed by the corresponding H. pylori mutant strains and underwent proteolytic processing to yield ~85 kDa passenger domains. Three mutant proteins (VacA ?484-504, ?511-536, and ?517-544) were secreted and induced vacuolation of mammalian cells, which indicated that these ?-helical coils were dispensable for vacuolating toxin activity. One mutant protein (VacA ?433-461) exhibited reduced vacuolating toxin activity compared to wild-type VacA. Other mutant proteins, including those containing deletions near the carboxy-terminal end of the ?-helical region (amino acids Val559-Asn628), exhibited marked defects in secretion and increased susceptibility to proteolytic cleavage by trypsin, which suggested that these proteins were misfolded. Conclusions These results indicate that within the ?-helical segment of the VacA p55 domain, there are regions of plasticity that tolerate alterations without detrimental effects on protein secretion or activity, as well as a carboxy-terminal region in which similar alterations result in protein misfolding and impaired secretion. We propose that non-essential ?-helical coils and a carboxy-terminal ?-helical segment required for proper protein folding and secretion are features shared by numerous autotransporter passenger domains.

2010-01-01

108

Neutron capture records of mesosiderites and an iron meteorite  

NASA Astrophysics Data System (ADS)

The Sm and Gd isotopic compositions of silicates from six mesosiderites (Dalgaranga, Estherville, Morristown, Northwest Africa (NWA) 1242, NWA 2932, and Vaca Muerta) and one iron meteorite (Udei Station) were determined to elucidate the cosmic-ray exposure records. All seven samples showed significant 150Sm/ 149Sm and 158Gd/ 157Gd isotopic shifts from neutron capture reactions corresponding to neutron fluences of (1.3-21.8) × 10 15 n cm -2. In particular, Vaca Muerta showed a significantly higher neutron fluences than the other six samples. The parameter for the degree of neutron thermalization ( ?Sm/ ?Gd) also showed a significant difference between Vaca Muerta (0.76) and the other samples (0.93-1.20). These results suggest a two-stage irradiation of the Vaca Muerta silicates in the parent body (>50 Ma) before formation of the mesosiderite and during its transit to Earth (138 Ma). This is consistent with the 81Kr-Kr cosmic-ray exposure age data of a Vaca Muerta pebble from a previous noble gas isotopic study.

Hidaka, Hiroshi; Yoneda, Shigekazu

2011-10-01

109

Vacuolating Cytotoxin Genotypes Are Strong Markers of Gastric Cancer and Duodenal Ulcer-Associated Helicobacter pylori Strains: a Matched Case-Control Study.  

PubMed

The Helicobacter pylori virulence gene, cagA, and active forms of the vacuolating cytotoxin gene, vacA, are major determinants of pathogenesis. However, previous studies linking these factors to disease risk have often included patients using aspirin/nonsteroidal anti-inflammatory agents (NSAIDs) or acid-suppressing drugs, both of which may confound results. Also, particularly for gastric cancer (GC), controls have often been of quite different ages. Here, we performed a careful study in a "clean" Belgian population with gastric cancer cases age and sex matched to 4 controls and with a parallel duodenal ulcer (DU) group. As in other populations, there was a close association between the presence of cagA and the vacA s1 genotype. For GC, associations were found for vacA s1-positive (P = 0.01, odds ratio [OR], 9.37; 95% confidence interval [CI], 1.16 to 201.89), i1-positive (P = 0.003; OR, 12.08; 95% CI, 1.50 to 259.64), and cagA-positive status (P < 0.05; OR, infinity; 95% CI, 0.76 to infinity). For DU, associations were found with vacA s1 (P = 0.002; OR, 6.04; 95% CI, 1.52 to 27.87) and i1 (P = 0.004; OR, 4.35; 95% CI, 1.36 to 14.78) status but not with cagA status. Neither condition showed independent associations with the vacA m1 allele or with more biologically active forms of cagA with longer 3' variable regions. In this Belgian population, the best markers of gastric cancer- and duodenal ulcer-associated strains are the vacA s1 and i1 genotypes. This fits with experimental data showing that the s and i regions are the key determinants of vacuolating cytotoxin activity. PMID:24920772

Memon, Ameer A; Hussein, Nawfal R; Miendje Deyi, Véronique Y; Burette, Alain; Atherton, John C

2014-08-01

110

Helicobacter pylori Membrane Vesicles Stimulate Innate Pro- and Anti-Inflammatory Responses and Induce Apoptosis in Jurkat T Cells  

PubMed Central

Persistent Helicobacter pylori infection induces chronic inflammation in the human gastric mucosa, which is associated with development of peptic ulceration, gastric atrophy, and gastric adenocarcinoma. It has been postulated that secretion of immunomodulatory molecules by H. pylori facilitates bacterial persistence, and membrane vesicles (MV), which have the potential to cross the gastric epithelial barrier, may mediate delivery of these molecules to host immune cells. However, bacterial MV effects on human immune cells remain largely uncharacterized to date. In the present study, we investigated the immunomodulatory effects of H. pylori MV with and without the vacuolating cytotoxin, VacA, which inhibits human T cell activity. We show a high degree of variability in the toxin content of vesicles between two H. pylori strains (SS1 and 60190). Vesicles from the more toxigenic 60190 strain contain more VacA (s1i1 type) than vesicles from the SS1 strain (s2i2 VacA), but engineering the SS1 strain to produce s1i1 VacA did not increase the toxin content of its vesicles. Vesicles from all strains tested, including a 60190 isogenic mutant null for VacA, strongly induced interleukin-10 (IL-10) and IL-6 production by human peripheral blood mononuclear cells independently of the infection status of the donor. Finally, we show that H. pylori MV induce T cell apoptosis and that this is enhanced by, but not completely dependent on, the carriage of VacA. Together, these findings suggest a role for H. pylori MV in the stimulation of innate pro- and anti-inflammatory responses and in the suppression of T cell immunity.

Letley, Darren; Rhead, Joanne; Atherton, John; Robinson, Karen

2014-01-01

111

Pathological significance and molecular characterization of the vacuolating toxin gene of Helicobacter pylori.  

PubMed Central

Some strains of Helicobacter pylori are known to produce an extracellular cytotoxin that causes vacuolization in various mammalian cells. In this study, we found that concentrated culture supernatants from four Helicobacter strains isolated from patients infected with the bacterium, but having normal gastric mucosa, lacked cytotoxic activity. We also show that a higher percentage of strains isolated from patients with polymorphonuclear leukocyte infiltration of gastric mucosa are toxin positive (78%) versus those isolated from patients lacking such infiltration (33%). In addition to examining the relationship between pathology and cytotoxic activity, we used the previously published N-terminal sequence of the protein to clone and characterize vacA, the structural gene encoding the cytotoxin. Briefly, three oligonucleotides capable of encoding the first nine amino acids corresponding to the sense strand and four oligonucleotides corresponding to the noncoding strand of the last seven known amino acids of the cytotoxin protein were made. They were used in all 12 possible combinations in 12 different PCR reactions, with DNA from a cytotoxin-positive strain as template. In four combinations, the expected 69-bp fragment was seen. The sequence of this 69-bp fragment confirmed that it encoded the known N-terminal sequence of the cytotoxin. This gene is capable of encoding a 136-kDa protein with a 33-amino-acid signal peptide, whereas the purified cytotoxin is only 87 kDa, suggesting processing in the C-terminal region of the protein. A single copy of the vacA gene encodes the cytotoxin in H. pylori. Consequently, the insertion of a kanamycin resistance marker in the vacA gene produced an isogenic mutant lacking the cytotoxic activity. This mutant provides genetic evidence that vacA encodes the cytotoxin. Sequence analysis of the DNA adjacent to the vacA gene demonstrated that this gene is next to a putative cysteinyl tRNA synthetase gene. From the sequence arrangement, we predict that there are no other genes transcribed together with vacA. We also show that five of seven cytotoxin-negative strains examined still carry the sequences encoding it whereas the other two have suffered a deletion of the vacA gene. We further show that in at least one cytotoxin-negative but vacA-positive strain (MO19), there are variations in the length of the vacA gene that could explain the cytotoxin-negative phenotype in this strain. Images

Phadnis, S H; Ilver, D; Janzon, L; Normark, S; Westblom, T U

1994-01-01

112

Modulation of autophagy by Helicobacter pylori and its role in gastric carcinogenesis.  

PubMed

Helicobacter pylori infection represents the strongest known risk factor for the development of gastric cancer. The vacuolating cytotoxin (VacA) plays a key role in disease pathogenesis by exerting pleiotrophic effects on the host. One effect of acute VacA exposure is the induction of autophagy. However, prolonged exposure to the toxin disrupts autophagy by preventing maturation of the autolysosome. Novel insights into the mechanism and consequences of this phenomenon have emerged, but many aspects remain largely unknown. Current evidence supports a scenario in which H. pylori-suppressed autophagy facilitates intracellular survival and persistence of the pathogen, while also generating an environment favoring carcinogenesis. PMID:24156875

Greenfield, Laura K; Jones, Nicola L

2013-11-01

113

Historic Indian Groups of the Choke Canyon Reservoir and Surrounding Area, Southern Texas: Volume I.  

National Technical Information Service (NTIS)

The study analyzes most of the cultural information recorded for each named Indian group that is relatable to the Choke Canyon Reservoir area of southern Texas. This has involved all the Indian groups named by Cabeza de Vaca for the area west and southwes...

T. N. Campbell T. J. Campbell

1981-01-01

114

Distinct Diversity of the cag Pathogenicity Island among Helicobacter pylori Strains in Japan  

Microsoft Academic Search

The severity of Helicobacter pylori-related disease is correlated with the presence of a cag pathogenicity island (PAI). Genetic diversity within the cag PAI may have a modifying effect on the pathogenic potential of the infecting strain. We analyzed the complete cag PAI sequences of 11 representative Japanese strains according to their vacA genotypes and clinical effects and examined the relationship

Takeshi Azuma; Akiyo Yamakawa; Shiho Yamazaki; Masahiro Ohtani; Yoshiyuki Ito; Atsushi Muramatsu; Hiroyuki Suto; Yukinao Yamazaki; Yoshihide Keida; Hideaki Higashi; Masanori Hatakeyama

2004-01-01

115

78 FR 36765 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...ER11-2540-002; ER11-2542-002. Applicants: CalPeak Power LLC, CalPeak Power--Panoche LLC, CalPeak Power--Vaca Dixon LLC, CalPeak Power--Enterprise LLC, CalPeak Power-- Border LLC, Tyr Energy, LLC, Commonwealth Chesapeake...

2013-06-19

116

75 FR 61742 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...filings: Docket Numbers: ER06-1331-006. Applicants: CalPeak Power LLC, CalPeak Power--Panoche LLC, CalPeak Power--Vaca Dixon LLC, CalPeak Power--El Cajon LLC, CalPeak Power-- Enterprise LLC, CalPeak Power--Border LLC, Tyr Energy...

2010-10-06

117

Mineralogical investigations of lunar samples and meteorites  

NASA Technical Reports Server (NTRS)

Electron microprobe analysis was employed to study north ray crater breccia 67015 from the Moon. The melting history of lunar troctolite 130-9 was investigated, along with the presence of Mg-26 in anorthite grains recovered from the Vaca Meurta mesosiderite. Geographic distributions of meteorites in Antarctica were plotted. The Allende meteorite was analyzed with the electron microprobe method.

Marvin, U. B.

1985-01-01

118

77 FR 48511 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...acquisition reports: Docket Numbers: LA11-4-000. Applicants: CalPeak Power LLC, CalPeak Power-Panoche LLC, CalPeak Power-Vaca Dixon LLC, CalPeak Power-Enterprise LLC, CalPeak Power- Border LLC, Starwood Power-Midway, LLC. Description:...

2012-08-14

119

Mineralogical investigations of lunar samples and meteorites  

NASA Astrophysics Data System (ADS)

Electron microprobe analysis was employed to study north ray crater breccia 67015 from the Moon. The melting history of lunar troctolite 130-9 was investigated, along with the presence of Mg-26 in anorthite grains recovered from the Vaca Meurta mesosiderite. Geographic distributions of meteorites in Antarctica were plotted. The Allende meteorite was analyzed with the electron microprobe method.

Marvin, U. B.

1985-02-01

120

78 FR 62296 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...20131004-5077. Comments Due: 5 p.m. ET 10/25/13. Docket Numbers: ER14-34-000. Applicants: CalPeak Power-Vaca Dixon LLC. Description: Change in Status & Tariff Revisions to be effective 11/27/2013. Filed Date: 10/4/13....

2013-10-15

121

Origin of Silicate Clasts in Mesosiderites: Trace Element Microdistributions and Mn-Cr Systematics Tell the Tale  

NASA Astrophysics Data System (ADS)

We report the results of a study of trace element distributions and Mn-Cr systematics in several basaltic clasts and one diogenitic clast from Vaca Muerta. The goal of this study is to ascertain whether these clasts are related to the HEDs.

Wadhwa, M.; Shukolyukov, A.; Davis, A. M.; Lugmair, G. W.

1999-03-01

122

Induction of Gastric Epithelial Cell Apoptosis by Helicobacter pylori Vacuolating Cytotoxin1  

Microsoft Academic Search

Chronic gastritis induced by Helicobacter pylori is a strong risk factor for the development of distal gastric adenocarcinoma. A specific host response to H. pylori that may contribute to gastric carcinogenesis is epithelial cell apoptosis. The aim of this study was to investigate the capacity of H. pylori vacuolating toxin (VacA) to induce gastric epithelial cell apoptosis. When cocultured with

Uma S. Krishna; Dawn A. Israel; Richard M. Peek

2003-01-01

123

76 FR 21732 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...Gas and Electric Company. Description: Pacific Gas and Electric Company submits tariff filing per 35.13(a)(2)(iii: Vaca-Dixon Solar Station WDT SGIA to be effective 4/28/2010. Filed Date: 04/06/2011. Accession Number:...

2011-04-18

124

78 FR 67133 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...Power LLC, CalPeak Power--Border LLC, CalPeak Power--Enterprise LLC, CalPeak Power--Panoche LLC, CalPeak Power--Vaca Dixon LLC Starwood Power-Midway LLC. Description: Quarterly Land Acquisition Report of CalPeak Power LLC, et al....

2013-11-08

125

78 FR 41792 - Combined Notice of Filings #1  

Federal Register 2010, 2011, 2012, 2013

...ER10-3257-002. Applicants: CalPeak Power LLC, CalPeak Power--Border LLC, CalPeak Power--Enterprise LLC, CalPeak Power--Vaca Dixon LLC, CalPeak Power-- Panoche LLC, Starwood Power-Midway, LLC. Description: Updated Market Power Analysis for...

2013-07-11

126

Custos de alimentação para caprinos na fase de aleitamento recebendo sucedâneos com fontes de proteína láctea e de origem vegetal  

Microsoft Academic Search

5 Bolsista de Pós-doutorado da Fapemig, UFV, Viçosa - MG. Resumo: Leite em pó integral de vaca, reconstituído, e sucedâneo comercial à base de mistura de proteínas vegetais isoladas foram comparados para avaliar custo de produção no aleitamento artificial em caprinos. Os animais foram separados das mães logo após o nascimento recebendo colostro tratado nas primeiras 6 horas de vida.

Ana Gabriela Pombo; Márcia Maria Cândido da Silva

127

Adherence and invasion of mouse-adapted H pylori in different epithelial cell lines  

PubMed Central

AIM: To assess the adhesion and invasion abilities of different mouse adapted H pylori strains in different cell lines in vitro and investigate their effects on the virulence factors cagA and vacA. METHODS: The adherence and invasion abilities of different H pylori strains in different epithelial cell lines were examined by the gentamycin protection assay. The null mutants of cagA and vacA were processed by direct PCR mutation method. The morphologic changes of different cell lines after H pylori attachment were examined by microscopy. RESULTS: The densities of adherence to and invasion into cells in vitro were different from those in the mouse infection experiments. 88-3887 strain could invade and adhere to cells stronger than SS1 and X47. All tested strains had better adhering and invasive abilities in SCG-7901 cell. CagA and vacA minus mutants had the same invasion and adherent abilities as their wild types. In all strains and cell lines tested, only AGS cell had the significant hummingbird phenotype after inoculation with the 88-3887 wild-type. CONCLUSION: Both the host cells and the bacteria play important parts in the invasion and adhesion abilities of H pylori. CagA and VacA are not related to the ability of invasion and adhesion of H pylori in different cell lines in vitro.

Zhang, Mao-Jun; Meng, Fan-Liang; Ji, Xiao-Yun; He, Li-Hua; Zhang, Jian-Zhong

2007-01-01

128

Helicobacter pylori in dental plaque and stomach of patients from Northern Brazil  

PubMed Central

AIM: To establish whether virulence factor genes vacA and cagA are present in Helicobacter pylori (H. pylori) retrieved from gastric mucosa and dental plaque in patients with dyspepsia. METHODS: Cumulative dental plaque specimens and gastric biopsies were submitted to histological examination, rapid urease test and polymerase chain reaction (PCR) assays to detect the presence of cagA and vacA polymorphisms. RESULTS: Detection of H. pylori from dental plaque and gastric biopsy samples was greater by PCR compared to histological examination and the rapid urease test. DNA from H. pylori was detected in 96% of gastric mucosa samples and in 72% of dental plaque samples. Sixty-three (89%) of 71 dental plaque samples that were H. pylori-positive also exhibited identical vacA and cagA genotypes in gastric mucosa. The most common genotype was vacAs1bm1 and cagA positive, either in dental plaque or gastric mucosa. These virulent H. pylori isolates were involved in the severity of clinical outcome. CONCLUSION: These pathogenic strains were found simultaneously in dental plaque and gastric mucosa, which suggests that gastric infection is correlated with the presence of H. pylori in the mouth.

Assumpcao, Monica Barauna; Martins, Luisa Caricio; Melo Barbosa, Hivana Patricia; dos Santos Barile, Katarine Antonia; de Almeida, Sintia Silva; Assumpcao, Paulo Pimentel; de Oliveira Corvelo, Tereza Cristina

2010-01-01

129

Proliferative and apoptotic effects of gastric epithelial cells induced by coccoid Helicobacter pylori.  

PubMed

Helicobacter pylori exhibit morphology convertion in a spiral or coccoid form. This study aims to reveal the impact of coccoid H. pylori on the proliferation and apoptosis of gastric epithelial cells. The cagA and vacA genes of H. pylori were detected by semi-quantitative RT-PCR. Proliferation and apoptosis were analyzed by the CCK-8 colorimetric method and TUNEL assay, respectively. Egr-1 mRNA and PCNA expression affected by the ERK1/2-specific inhibitor were detected by RT-PCR and immunochemistry. At low density of infection (MOI?vacA and cagA in coccoid H. pylori decreased compared with the spiral form, whereas vacA decreased more than cagA. The difference of proliferation and apoptosis may be related to the unequal decreased expression of vacA and cagA in coccoid H. pylori. Activation of the ERK1/2-Egr-1-PCNA signal transduction pathway may play an important role in coccoid H. pylori-induced cell proliferation. Long latency of the coccoid form of H. pylori in gastric tissue may be associated with gastric cancer caused by H. pylori. PMID:22581720

Li, Neng; Han, Lei; Chen, Jiansen; Lin, Xu; Chen, Hao; She, Feifei

2013-02-01

130

A DIVERSE ASSEMBLAGE OF ANACARDIACEAE FROM OLIGOCENE SEDIMENTS ,T EPEXI DE RODRIGUEZ, PUEBLA ,M EXICO1  

Microsoft Academic Search

Among the plants collected from the Pie de Vaca Formation of the Oligocene, of Tepexi de Rodriguez, Puebla, Mexico are five plants of Anacardiaceae, Haplorhus medranoensis, Rhus toxicodendron, Rhus sp., Comocladia intermedia, and Pistacia marquezii represented by their leaves and\\/or leaflets. The past and present diversity and geographic distribution of one of these genera, Rhus, demonstrate its capability to adapt

SERGIO R. S. CEVALLOS-FERRIZ

2002-01-01

131

A diverse assemblage of Anacardiaceae from Oligocene sediments, Tepexi de Rodriguez, Puebla, Mexico.  

PubMed

Among the plants collected from the Pie de Vaca Formation of the Oligocene, of Tepexi de Rodríguez, Puebla, México are five plants of Anacardiaceae, Haplorhus medranoensis, Rhus toxicodendron, Rhus sp., Comocladia intermedia, and Pistacia marquezii represented by their leaves and/or leaflets. The past and present diversity and geographic distribution of one of these genera, Rhus, demonstrate its capability to adapt and diversify in a wide variety of environments. Leaf architecture characters of this taxon overlap with those of other genera in the family, suggesting a high degree of phenotypic plasticity. The presence in the Pie de Vaca Formation of a type of Pistacia with leaf architecture characters similar to those of Asian plants further supports a long history of exchange between low-latitude North America and Asia. Links between low-latitude North and South America and the Caribbean are suggested by the presence of Comocladia and Haplorhus. Whereas Comocladia highlights the long history of regional endemics in the area, Haplorhus, today an endemic monotypic genus of Peru, suggests exchange mechanisms between North and South America. The morphologic characters of these taxa, and those of Pseudosmodingium (Anacardiaceae), some Rosaceae, Leguminosae, and Berberidaceae, suggest that the Pie de Vaca community was established and evolved in harsh environmental conditions. The Pie de Vaca flora thus provides significant new insights into the biogeographic relationships of the low latitude vegetation of North America. PMID:21665653

Ramírez, José L; Cevallos-Ferriz, Sergio R S

2002-03-01

132

Prevalence of Helicobacter pylori virulence genotypes among children in Eastern Turkey  

PubMed Central

AIM: To identify the virulence genotypes of Helicobacter pylori (H. pylori) if present in children in Eastern Turkey and if those genotypes are mostly associated with severe clinical presentations. METHODS: A total of 49 H. pylori positive Turkish children (42 with antral nodularity and 7 with peptic ulcer) who underwent upper gastrointestinal endoscopy with abdominal symptoms during the period from March 2011 to September 2012 were enrolled in this study. Antral nodularity was diagnosed endoscopically by two of the authors. We determined for the presence of cagA, vacA, cagE, iceA and babA2 genotypes of H. pylori isolates in DNA obtained directly from frozen gastric biopsy samples by polymerase chain reaction test using specific primers. RESULTS: Of the 49 H. pylori isolates studied, 61.2%, 91.8%, 22.4%, 28.6%, 57.1% and 40.8% were positive for the cagA, vacA s1, cagE, iceA1, iceA2 and babA2 genes, respectively. We showed that the most common vacA subtype was s1a (79.6%). However, the s2 gene was found less frequently with an isolation rate of 8.2% of the H. pylori isolates. The genotypes iceA2 and vacA s1m2 were the most frequently found types in children with antral nodularity. In addition, the genotypes iceA1, babA2 and vacA s1m1 were found in similar ratios in all the H. pylori isolates obtained from children with peptic ulcer. The genotypes vacA s2m1 and s1c were not observed in any of isolates studied. CONCLUSION: This study showed that vacA s1m2, cagA and iceA2 were the most common genotypes, and no association between antral nodularity and genotypes was observed.

Ozbey, Gokben; Dogan, Yasar; Demiroren, Kaan

2013-01-01

133

Association of iceA and babA genotypes in Helicobacter pylori strains with patient and strain characteristics.  

PubMed

Data on the geographic prevalence of Helicobacter pylori iceA and babA alleles in Eastern Europe are still relatively scant. The aim of this study was to evaluate the prevalence of iceA and babA genotypes in Bulgarian symptomatic patients. The iceA and babA genotypes were evaluated by PCR with pure cultures in strains from 196 and 181 patients, respectively. Mixed infections were found in 10.2% of all 196 patients. Prevalence of H. pylori genotypes in patients with single-strain infections was 69.3% for iceA1, 30.7% for iceA2, 82.4% for cagA(+), 89.2% for vacA s1, 10.8% for vacA s2, 39.8% for vacA m1, 60.2% for vacA m2 and 48.8% for babA2. Within the iceA1 positive strains, 94.3% and 88.5% were also vacA s1a and cagA positive, respectively. Of the babA2 positive strains, 100.0%, 92.4% and 72.2% were also vacA s1a, cagA and iceA1 positive, respectively. Ulcer patients had more often strains with cagA positive status and vacA s1a allele. Although neither iceA1 nor babA2 were more common in ulcer patients, the combination of both alleles was more frequent (48.1%) in the ulcer patients than in the rest (28.7%). Clarithromycin susceptible strains had more often iceA1 allele (74.4%) than the resistant strains (55.3%). In conclusion, the results demonstrated a high prevalence of virulent H. pylori in Bulgaria. Both iceA1 and babA2 genotypes were associated with other virulence factors of H. pylori and, in addition, the iceA1 allele was associated with the strain susceptibility. PMID:20454856

Boyanova, Lyudmila; Yordanov, Daniel; Gergova, Galina; Markovska, Rumyana; Mitov, Ivan

2010-10-01

134

Claritromycin resistance and Helicobacter pylori genotypes in Italy.  

PubMed

The relationship between H. pylori clarithromycin resistance and genetic pattern distribution has been differently explained from different geographic areas. Therefore, we aimed to assess the clarithromycin resistance rate, to evaluate the bacterial genetic pattern, and to search for a possible association between clarithromycin resistance and cagA or vacA genes. This prospective study enrolled 62 consecutive H. pylori infected patients. The infection was established by histology and rapid urease test. Clarithromycin resistance, cagA and vacA status, including s/m subtypes, were assessed on paraffin-embedded antral biopsy specimens by TaqMan real time polymerase chain reaction (PCR). Primary clarithromycin resistance was detected in 24.1 % of cases. The prevalence of cagA was 69.3 %, and a single vacA mosaicism was observed in 95.1 % cases. In detail, the s1m1 was observed in 23 (38.9 %) patients, the s1m2 in 22 (37.2 %), and the s2m2 in 14 (23.7 %), whereas the s2m1 combination was never found. The prevalence of cagA and the vacA alleles distribution did not significantly differ between susceptible and resistant strains. Primary clarithromycin resistance is high in our area. The s1m1 and s1m2 are the most frequent vacA mosaicisms. There is no a relationship between clarithromycin resistance and bacterial genotypic pattern and/or cagA positivity. PMID:17205045

De Francesco, Vincenzo; Margiotta, Marcella; Zullo, Angelo; Hassan, Cesare; Valle, Nicola Della; Burattini, Osvaldo; D'Angelo, Roberto; Stoppino, Giuseppe; Cea, Ugo; Giorgio, Floriana; Monno, Rosa; Morini, Sergio; Panella, Carmine; Ierardi, Enzo

2006-12-01

135

Susceptibility to Helicobacter pylori infection: results of an epidemiological investigation among gastric cancer patients.  

PubMed

The aim of this study was to identify the clinical, demographic, lifestyle factors and selected genetic polymorphisms that affect the susceptibility towards Helicobacter pylori (H. pylori) infection in gastric cancer patients. Histological confirmed gastric adenocarcinoma cases that underwent curative gastrectomy between 2002 and 2012 were included. Gastric biopsy samples were obtained to determine the H. pylori status, and further cagA status and vacA m and s genotypes by polymerase chain reaction. Patients were interviewed with structured questionnaires, and blood samples were collected for EPHX1, GSTM1, GSTT1, IL1B, IL1-RN, MTHFR and p53 genotyping. Proportions were compared in univariate analysis, while the relation between putative risk factors and H. pylori status and genotype were measured using logistic regression analysis. One hundred forty-nine gastric cancer patients were included, of which 78.5 % were H. pylori positive. Among positive patients 50 % were cagA+, 72.5 % vacA m1 and 80.7 % vacA s1. The presence of cagA was less frequent among vacA m1 (p = 0.031) and vacA s1 (p = 0.052) subtypes. The presence of father history for any cancer was a significant risk factor for H. pylori infection [adjusted odds ratio (OR) = 8.18, 95 % confidence interval (CI) 1.04-64.55]. EPHX1 exon 3 T > C (OR = 0.35, CI 95 % 0.13-0.94), IL1B-511 T > C (OR = 0.38, CI 95 % 0.15-0.97) and IL1-RN VNTR (OR = 0.19, CI 95 % 0.06-0.58) polymorphisms were protective towards H. pylori infection in the univariate analysis. Wine consumption was associated with higher risk of carrying the H. pylori vacA m1 virulent subtype (p = 0.034). Lastly, cardiovascular diseases were less common among cagA positive subjects (p = 0.023). Father history of any cancer is a risk factor for H. pylori infection. Polymorphisms in IL1B-511, IL1-RN and EPHX1 exon 3 genes might be protective towards H. pylori infection. PMID:24526578

Panic, Nikola; Mastrostefano, Elena; Leoncini, Emanuele; Persiani, Roberto; Arzani, Dario; Amore, Rosarita; Ricci, Riccardo; Sicoli, Federico; Sioletic, Stefano; Bulajic, Milutin; Ugo, Domenico D'; Ricciardi, Walter; Boccia, Stefania

2014-06-01

136

Virulence genotypes and drug resistance of Helicobacter pylori from Vladivostok, Russia: another feature in the Far East.  

PubMed

Helicobacter pylori in Vladivostok, Far Eastern Russia, was investigated during 2004 to 2009. The genotype cagA(+) vacA(+) (s1/m1 or m2) accounted for 74.7%, with cagA(-) vacA(+) (s2/m2) at 11.2%. The CagA EPIYA type was mainly Western ABC, with minor types (ABCCC and novel AAABC) or non-Western/non-East Asia type (AB). Regarding drug resistance, metronidazole resistance was the highest, with a marked decrease in 6 years (from 71.4% to 30.8%); in contrast, levofloxacin and clarithromycin resistance increased. The data indicate that in Vladivostok, H. pylori was mainly the Western (not East Asian) type and dynamic changes in drug resistance occurred during 6 years. PMID:22211953

Reva, Ivan; Takano, Tomomi; Higuchi, Wataru; Iwao, Yasuhisa; Taneike, Ikue; Nakagawa, Saori; Ike, Masami; Pererva, Oleg; Tarankov, Alexey; Agapov, Mikhail; Rizhkov, Evgeniy; Singur, Olga; Reva, Galina; Potapov, Vladimir; Yamamoto, Tatsuo

2012-03-01

137

First direct sulfuric acid detection in the exhaust plume of a jet aircraft in flight  

NASA Astrophysics Data System (ADS)

Sulfuric acid (SA) was for the first time directly detected in the exhaust plume of a jet aircraft in flight. The measurements were made by a novel aircraft-based VACA (Volatile Aerosol Component Analyzer) instrument of MPI-K Heidelberg while the research aircraft Falcon was chasing another research aircraft ATTAS. The VACA measures the total SA in the gas and in volatile submicron aerosol particles. During the chase the engines of the ATTAS alternatively burned sulfur-poor and sulfur-rich fuel. In the sulfur-rich plume very marked enhancements of total SA were observed of up to 1300 pptv which were closely correlated with ?CO2 and ?T and were far above the local ambient atmospheric background-level of typically 15-50 pptv. Our observations indicate a lower limit for the efficiency ? for fuel-sulfur conversion to SA of 0.34 %.

Curtius, J.; Sierau, B.; Arnold, F.; Baumann, R.; Busen, R.; Schulte, P.; Schumann, U.

138

Helicobacter pylori in North and South America before Columbus.  

PubMed

We present a molecular epidemiologic study, based on an analysis of vacA, cagA and cag right end junction genotypes from 1042 Helicobacter pylori isolates, suggesting that H. pylori was present in the New World before Columbus. Eight Native Colombian and Alaskan strains possessed novel vacA and/or cagA gene structures and were more closely related to East Asian than to non-Asian H. pylori. Some Native Alaskan strains appear to have originated in Central Asia and to have arrived after strains found in South America suggesting that H. pylori crossed the Bering Strait from Asia to the New World at different times. PMID:12062433

Yamaoka, Yoshio; Orito, Etsuro; Mizokami, Masashi; Gutierrez, Oscar; Saitou, Naruya; Kodama, Tadashi; Osato, Michael S; Kim, Jong G; Ramirez, Francisco C; Mahachai, Varocha; Graham, David Y

2002-04-24

139

Analysis of antimicrobial susceptibility and virulence factors in Helicobacter pylori clinical isolates  

Microsoft Academic Search

BACKGROUND: In this study, we evaluated the prevalence of primary resistance of Brazilian H. pylori isolates to metronidazole, clarithromycin, amoxicillin, tetracycline, and furazolidone. In addition, the vacA, iceA, cagA and cagE genotypes of strains isolated from Brazilian patients were determined and associated with clinical data in an effort to correlate these four virulence markers and antibiotic resistance. METHODS: H. pylori

Anita Paula Ortiz Godoy; Marcelo Lima Ribeiro; Yune Helena Borges Benvengo; Lea Vitiello; Maira de Carvalho Bueno Miranda; Sergio Mendonça; José Pedrazzoli Jr

2003-01-01

140

PCR-Based Diagnosis of Helicobacter pylori Infection and Real-Time Determination of Clarithromycin Resistance Directly from Human Gastric Biopsy Samples  

Microsoft Academic Search

A novel PCR detection assay that amplifies the Helicobacter pylori-specific vacuolating cytotoxin gene (vacA) and thus enables rapid diagnosis of infection is described. Additionally, a real-time probe hybridization melting point analysis assay to detect all three mutations in the 23S rRNA gene associated with clarithromycin resistance was applied directly to antral gastric biopsy samples. Comparison with culture and an alternative

STEPHANIE A. CHISHOLM; ROBERT J. OWEN; E. LOUISE TEARE; SETH SAVERYMUTTU

2001-01-01

141

NIR reflectance spectroscopy of mafic minerals in the temperature range between 80 and 473 K  

NASA Astrophysics Data System (ADS)

We performed our investigations on mono-mineralogical phases of two terrestrial pyroxenes, a diopsidic augite and a hyperstene as well as on four meteoritic samples, Millbillillie, Ellemeet, Soko-Banja and Vaca Muerta, which represent extraterrestrial matter and could be considered to be analogs for surface material of some asteroid classes. Beside the known spectral variations characterizing ortho- and clinopyroxenes as well as basaltic assemblages, temperature related effects on the reflectance spectra are discussed.

Schade, U.; Wäsch, R.

1999-01-01

142

Characterization of oral Helicobacter pylori strain by 4 methods.  

PubMed

The aim of the study was to describe oral Helicobacter pylori strain from a child by 4 methods. The strain was positive by immunofluorescence, ureA- and cagA positive, vacA s1 m2 genotype and resistant to metronidazole and clarithromycin. In conclusion, virulent and antibiotic resistant H. pylori strains can be present in oral cavity from patients with chronic dental and gastroduodenal diseases. PMID:24075629

Boyanova, Lyudmila; Panov, Vladimir; Yordanov, Daniel; Gergova, Galina; Mitov, Ivan

2013-12-01

143

Involvement of mast cells in gastritis caused by Helicobacter pylori: a potential role in epithelial cell apoptosis  

PubMed Central

Background The role(s) of mast cells (MC) in gastric mucosal inflammation caused by Helicobacterpylori is (are) still debated. Aim To determine whether there is an association between MC density and epithelial cell apoptosis in antral gastric mucosa infected by H pylori. Patients and methods Biopsy specimens from 122 H pylori?positive subjects with chronic active gastritis, 84 patients with non?steroidal anti?inflammatory drug?induced gastritis and 48 volunteers were included. H pylori genotypes were determined by PCR amplification of bacterial cultures. Immunohistochemical analysis was performed on tissue microarrays with anti?CD117, anti?chymase, anti?tryptase, anti?myeloperoxidase, anti?Bcl?2, anti?Bcl?x, anti?Bax and anti?caspase 3 antibodies. Results Of the 122 patients infected with H pylori, 76 (62.3%) harboured cagA positive strains. H pylori isolates belonged to the vacAs1/m1 genotype in 82 (67%) cases, to the vacAs2/m2 genotype in 23 (18.8%) cases and to the vacAs1/m2 genotype in 17 (13.9%) cases. 61 (50%) H pylori isolates were babA2+. In patients infected with H pylori, the density of MC, and in particular the number of MC?associated epithelial cells, was correlated with a high number of apoptotic epithelial cells. Moreover, the density of MC was correlated with the number of neutrophils infiltrating the antral gastric mucosa, and was strongly increased in patients infected with cagA, vacAs1/m1 and babA2 positive strains. Conclusions Taken together, these data show that the density of MC can be considered as a histopathological criterion of gastritis activity in patients infected with H pylori.

Hofman, Veronique; Lassalle, Sandra; Selva, Eric; Kalem, Kheira; Steff, Adrien; Hebuterne, Xavier; Sicard, Dominique; Auberger, Patrick; Hofman, Paul

2007-01-01

144

Helicobacter pylori ?-glutamyl transpeptidase and vacuolating cytotoxin promote gastric persistence and immune tolerance  

PubMed Central

Infection with the gastric bacterial pathogen Helicobacter pylori is typically contracted in early childhood and often persists for decades. The immunomodulatory properties of H. pylori that allow it to colonize humans persistently are believed to also account for H. pylori’s protective effects against allergic and chronic inflammatory diseases. H. pylori infection efficiently reprograms dendritic cells (DCs) toward a tolerogenic phenotype and induces regulatory T cells (Tregs) with highly suppressive activity in models of allergen-induced asthma. We show here that two H. pylori virulence determinants, the ?-glutamyl transpeptidase GGT and the vacuolating cytotoxin VacA, contribute critically and nonredundantly to H. pylori’s tolerizing effects on murine DCs in vitro and in vivo. The tolerance-promoting effects of both factors are independent of their described suppressive activity on T cells. Isogenic H. pylori mutants lacking either GGT or VacA are incapable of preventing LPS-induced DC maturation and fail to drive DC tolerization as assessed by induction of Treg properties in cocultured naive T cells. The ?ggt and ?vacA mutants colonize mice at significantly reduced levels, induce stronger T-helper 1 (Th1) and T-helper 17 (Th17) responses, and/or trigger more severe gastric pathology. Both factors promote the efficient induction of Tregs in vivo, and VacA is required to prevent allergen-induced asthma. The defects of the ?ggt mutant in vitro and in vivo are phenocopied by pharmacological inhibition of the transpeptidase activity of GGT in all readouts. In conclusion, our results reveal the molecular players and mechanistic basis for H. pylori-induced immunomodulation, promoting persistent infection and conferring protection against allergic asthma.

Oertli, Mathias; Noben, Manuel; Engler, Daniela B.; Semper, Raphaela P.; Reuter, Sebastian; Maxeiner, Joachim; Gerhard, Markus; Taube, Christian; Muller, Anne

2013-01-01

145

mRNA levels of TLR4 and TLR5 are independent of H pylori  

PubMed Central

AIM: To determine if the presence H pylori or its virulence affect toll-like receptor 4 (TLR4) and TLR5 mRNA expression levels. METHODS: For the in vivo assays, gastric biopsies were obtained from 40 patients and H pylori status was determined. For the in vitro assays, human gastric adenocarcinoma mucosal cells (AGS) were cultured in the presence or absence of twelve selected H pylori strains. H pylori strains isolated from culture-positive patients and selected strains were genotyped for cagA and vacA. The cDNA was obtained from mRNA extracted from biopsies and from infected AGS cells. TLR4 and TLR5 mRNA levels were examined by real-time PCR. RESULTS: The presence of H pylori did not affect the mRNA levels of TLR4 or TLR5 in gastric biopsies. The mRNA levels of both receptors were not influenced by the vacA status (P > 0.05 for both receptors) and there were no differences in TLR4 or TLR5 mRNA levels among the different clinical presentations/histological findings (P > 0.05). In the in vitro assay, the mRNA levels of TLR4 or TLR5 in AGS cells were not influenced by the vacAs1 status or the clinical condition associated with the strains (P > 0.05 for both TLR4 and TLR5). CONCLUSION: The results of this study show that the mRNA levels of TLR4 and TLR5 in gastric cells, both in vivo and in vitro, are independent of H pylori colonization and suggest that vacA may not be a significant player in the first step of innate immune recognition mediated by TLR4 or TLR5.

Garza-Gonzalez, Elvira; Bocanegra-Garcia, Virgilio; Bosques-Padilla, Francisco Javier; Flores-Gutierrez, Juan Pablo; Moreno, Francisco; Perez-Perez, Guillermo Ignacio

2008-01-01

146

Estimation of the invasiveness of Helicobacter pylori strains on the basis of serological investigations in blood  

Microsoft Academic Search

Introduction: Helicobacter pylori is a recognized factor inducing gastritis. Chronic gastritis with H.pylori infection is a precursor of chronic peptic ulcer disease as well as gastric cancer and lymphoma. Alterations in mucous membrane le- ading to the development of a neoplasm can last for years or even decades. The most pathogenic H.pylori strains are cagA+\\/ vacA+ and infection with these

Leokadia B?k-Romaniszyn; Hanna Romanowicz; Andrzej Kulig; Magdalena Chmiela; Izabela P?aneta-Ma?ecka

147

Free Recombination within Helicobacter pylori  

Microsoft Academic Search

Sequences of three gene fragments (flaA, flaB, and vacA) from Helicobacter pylori strains isolated from patients in Germany, Canada, and South Africa were analyzed for diversity and for linkage equilibrium by using the Homoplasy Test and compatibility matrices. Horizontal genetic exchange in H. pylori is so frequent that different loci and polymorphisms within each locus are all at linkage equilibrium.

Sebastian Suerbaum; John Maynard Smith; Khairun Bapumia; Giovanna Morelli; Noel H. Smith; Erdmute Kunstmann; Isabelle Dyrek; Mark Achtman

1998-01-01

148

Distinctiveness of Genotypes of Helicobacter pylori in Calcutta, India  

Microsoft Academic Search

The genotypes of 78 strains of Helicobacter pylori from Calcutta, India (55 from ulcer patients and 23 from more-benign infections), were studied, with a focus on putative virulence genes and neutral DNA markers that were likely to be phylogenetically informative. PCR tests indicated that 80 to 90% of Calcutta strains carried the cag pathogenicity island (PAI) and potentially toxigenic vacAs1

ASISH K. MUKHOPADHYAY; DANGERUTA KERSULYTE; JIN-YONG JEONG; SIMANTI DATTA; YOSHIYUKI ITO; ABHIJIT CHOWDHURY; SUJIT CHOWDHURY; AMAL SANTRA; SUJIT K. BHATTACHARYA; TAKESHI AZUMA; G. BALAKRISH NAIR; D. E. Berg

2000-01-01

149

Presentación: el Fórum a debate  

Microsoft Academic Search

La posibilidad de escribir un libro sobre el Fórum empezó a tomar forma gracias a una ayuda que la Comissió Permanent de Recerca de la Universidad de Barcelona brindó al Seminario de Filosofía Política. Previamente, sin embargo, se iban fraguando en el espíritu de este último las inquietudes y esperanzas necesarias para empezar a trabajar; es imposible disociar, por tanto,

Juan Manuel Checa

2005-01-01

150

Ambiente para la Captura y Administración de Versiones de Modelos  

Microsoft Academic Search

El proceso de desarrollo de modelos para la gestión, investigación, producción, etc., en general involucra actividades creativas, que frecuentemente son poco estructuradas, es decir, no existe un flujo de trabajo definido previamente. Durante este proceso se genera un gran número de modelos de distinto nivel de abstracción del objeto que se desarrolla, el cual puede consistir en un sistema de

Diego Sánchez Schenone; Silvio Gonnet; Horacio Leone

151

Lewis antigen expression and other pathogenic factors in the presence of atrophic chronic gastritis in a European population.  

PubMed

To study the relationship between Helicobacter pylori cagA and vacA status and the expression of Lewis (Le) antigens and between these characteristics and atrophic chronic gastritis (ACG), H. pylori infection was assessed by culture and by histologic and serologic tests, cagA and vacA were assessed by a polymerase chain reaction--based reverse hybridization assay, and bacterial Le expression was assessed by immunoblotting. ACG was any form of antral or fundic atrophy with or without intestinal metaplasia. Of the 215 isolates, 64% were cagA(+) and 100% were vacA(+) (s1m1, 42%; s1m2, 29%; s2m2, 29%; and s2m1, 0). Le typing of 155 isolates showed that 6 (4%) were Le(x), 31 (20%) were Le(y), 87 (56%) were Le(x,y), and 31 (20%) were neither Le(x) nor Le(y). Two main clusters of isolates were identified by multiple correspondence analysis: s1a/m1/cagA(+)/Le(x)+/Le(y)+ (n=44; 29.7%) and s2/m2a/cagA(-)/Le(y)+ or Le(x)-/Le(y)- (n=29; 19.7%). Among patients with ACG, 54% of their isolates were from cluster s1m1/cagA(+)/Le(x)+/Le(y)+, which was associated with the presence of ACG (odds ratio, 7.4; 95% confidence interval, 1.5-37.0). PMID:11865403

Broutet, Nathalie; Moran, Anthony; Hynes, Sean; Sakarovitch, Charlotte; Mégraud, Francis

2002-02-15

152

Virulence factor genotypes of Helicobacter pylori affect cure rates of eradication therapy  

PubMed Central

The cure rates of Helicobacter pylori infection by using a combination of a proton pump inhibitor (PPI) and antimicrobial agents are mainly influenced by bacterial susceptibility to antimicrobial agents and the magnitude of acid inhibition during the treatment. Currently used empirical triple therapies do not reliably produce a ?80% cure rate on an intention-to-treat basis. Therefore, tailored regimens based on relevant microbiological findings and pharmacogenomics are recommended for attaining an acceptable ?95% cure rate. Recently, virulence factors of H. pylori, such as cagA and vacA, are reported to be major factors determining the cure rates. Individuals infected with strains with cagA-negative and vacA s2 genotypes have significantly increased risk of eradication failure of H. pylori infection. These virulence factors enhance gastric mucosal inflammation and are associated with the development of peptic ulcer and gastric cancer. H. pylori virulence factors induce proinflammatory cytokines, such as interleukin (IL)-1, IL-8, and tumor necrosis factor (TNF)-?, which influence mucosal inflammation and/or gastric acid secretion. When physicians select an H. pylori eradication regimen with an acceptable cure rate, they might need to consider H. pylori virulence factors, especially cagA and vacA.

Sugimoto, Mitsushige; Yamaoka, Yoshio

2011-01-01

153

Helicobacter pylori typing as a tool for tracking human migration  

PubMed Central

Helicobacter pylori strains from different geographic areas exhibit clear phylogeographical differentiation; therefore, the genotypes of H. pylori strains can serve as markers for the migration of human populations. Currently, the genotypes of two virulence factors of H. pylori, cagA and vacA, and multilocus sequence typing (MLST) are widely used markers for genomic diversity within H. pylori populations. There are two types of cagA: the East Asian type and the Western type. In addition, the right end of the cag pathogenicity island is divided into five subtypes and there are distinct mosaic structures at the signal region and the middle region of vacA. Using combinations of the cagA, cag right end junction, and vacA genotypes, five major groups (East Asia type, South/Central Asia type, Iberian/Africa type and Europe type) have been defined according to geographical associations. MLST has revealed seven modern population types and six ancestral population types of H. pylori, and is a useful tool for mapping human migration patterns. Serial studies of large numbers of H. pylori strains, including strains isolated from aboriginal populations, show that MLST analysis provides more detailed information on human migration than does the analysis of human genetics. H. pylori infection is rapidly declining as a result of improvements in personal hygiene and quality of life. The molecular epidemiology of H. pylori infection has much to tell us and should be studied before it disappears entirely.

Yamaoka, Y.

2011-01-01

154

Cyanidin 3-O-glucoside reduces Helicobacter pylori VacA-induced cell death of gastric KATO III cells through inhibition of the SecA pathway.  

PubMed

Two key virulence factors of Helicobacter pylori are the secreted virulent proteins of vacuolating toxin A (VacA) and cytotoxin associated protein A (CagA) which lead to damages of gastric epithelial cells. We previously identified that the cyanidin 3-O-glucoside (C3G) inhibits the secretion of both VacA and CagA. In the current report, we show that C3G inhibits VacA secretion in a dose-dependent manner by inhibiting secretion system subunit protein A (SecA) synthesis. As SecA is involved in translocation of bacterial proteins, we predicted that inhibition of the SecA pathway by C3G should decrease H. pylori-induced cell death. To test this hypothesis, the human gastric cell line KATO III cells were co-cultured with H. pylori 60190 (VacA(+)/CagA(+)) and C3G. We found that C3G treatment caused a decrease in activation of the pro-apoptotic proteins caspase-3/-8 in H. pylori-infected cells leading to a decrease in cell death. Our data suggest that consumption of foods containing anthocyanin may be beneficial in reducing cell damage due to H. pylori infection. PMID:24904230

Kim, Sa-Hyun; Woo, Hyunjun; Park, Min; Rhee, Ki-Jong; Moon, Cheol; Lee, Dongsup; Seo, Woo Duck; Kim, Jong Bae

2014-01-01

155

Transcranial Doppler sonography in chronic paroxysmal hemicrania.  

PubMed

Three patients with chronic paroxysmal hemicrania (CPH) (1 M, 2 F) and 9 healthy controls (8 M 1 F) were studied with transcranial Doppler (TCD) sonography. One patient who was studied during the spontaneous attacks hyperventilated markedly. Middle cerebral artery velocity (VMCA) was measured in the first attack, and anterior cerebral artery velocity (VACA) in the second attack, respectively. VMCA and VACA decreased bilaterally during attack. VMCA started to decrease at an early stage of the attack, i.e. prior to the major hyperventilation that was observed during the attack. VACA on the symptomatic side decreased less than that on the other side (P < 0.05). Cerebral vasomotor reactivity (VMR) was expressed as the percentage change in mean blood flow velocity as a function of end-tidal PCO2 (PETCO2) reduction induced by voluntary hyperventilation (delta V/delta PETCO2). In the 3 patients, a slightly lowered VMR was observed in the MCA and posterior cerebral artery on both sides, and in the ACA on the symptomatic side (P > 0.05) in comparison with controls. These observations may imply an abnormal vascular reactivity in CPH. PMID:7903292

Shen, J M

1993-10-01

156

Red wine and green tea reduce H pylori- or VacA-induced gastritis in a mouse model  

PubMed Central

AIM: To investigate whether red wine and green tea could exert anti-H pylori or anti-VacA activity in vivo in a mouse model of experimental infection. METHODS: Ethanol-free red wine and green tea concentrates were administered orally as a mixture of the two beverages to H pylori infected mice, or separately to VacA-treated mice. Gastric colonization and gastric inflammation were quantified by microbiological, histopathological, and immunohistochemical analyses. RESULTS: In H pylori-infected mice, the red wine and green tea mixture significantly prevented gastritis and limited the localization of bacteria and VacA to the surface of the gastric epithelium. Similarly, both beverages significantly prevented gastric epithelium damage in VacA-treated mice; green tea, but not red wine, also altered the VacA localization in the gastric epithelium. CONCLUSION: Red wine and green tea are able to prevent H pylori-induced gastric epithelium damage, possibly involving VacA inhibition. This observation supports the possible relevance of diet on the pathological outcome of H pylori infection.

Ruggiero, Paolo; Rossi, Giacomo; Tombola, Francesco; Pancotto, Laura; Lauretti, Laura; Del Giudice, Giuseppe; Zoratti, Mario

2007-01-01

157

Determination of Helicobacter pylori Virulence Genes in Gastric Biopsies by PCR.  

PubMed

Aim. The aim of this study was to identify the presence of H. pylori in biopsy specimens from symptomatic patients by PCR. In addition, the rate of cagA, vacA, iceA1, and iceA2 virulence genes was determined. Materials and Methods. One hundred antral gastric biopsy specimens were collected during endoscopy from patients suffering from gastroduodenal symptoms. The samples were collected by the gastroenterologists in their own clinics in Ramallah, Palestine. DNA was extracted from the biopsies and subsequently used for PCR identification of H. pylori and the virulence genes using specific primers. Results. The rate of positive H. pylori in the collected biopsies was 44%. The rates of the virulence genes in this sample: cagA, vacA, iceA1, and iceA2 were 65.9%, 40.9%, 63.6%, and 84.1%, respectively. Conclusion. The iceA2 gene was the most frequent in this study. Much research is necessary to determine the presence of an association of this gene with gastric pathology. Variation in the rates of the iceA gene in different countries is a strong indication of its geographical distribution. This study would provide important information regarding the prevalence of virulence genes (vacA, cagA, iceA1, and iceA2) in H. pylori strains in the sample tested in this country. PMID:23691338

Essawi, Tamer; Hammoudeh, Wail; Sabri, Israr; Sweidan, Walid; Farraj, Mohammad A

2013-01-01

158

Cyanidin 3-O-Glucoside Reduces Helicobacter pylori VacA-Induced Cell Death of Gastric KATO III Cells through Inhibition of the SecA Pathway  

PubMed Central

Two key virulence factors of Helicobacter pylori are the secreted virulent proteins of vacuolating toxin A (VacA) and cytotoxin associated protein A (CagA) which lead to damages of gastric epithelial cells. We previously identified that the cyanidin 3-O-glucoside (C3G) inhibits the secretion of both VacA and CagA. In the current report, we show that C3G inhibits VacA secretion in a dose-dependent manner by inhibiting secretion system subunit protein A (SecA) synthesis. As SecA is involved in translocation of bacterial proteins, we predicted that inhibition of the SecA pathway by C3G should decrease H. pylori-induced cell death. To test this hypothesis, the human gastric cell line KATO III cells were co-cultured with H. pylori 60190 (VacA+/CagA+) and C3G. We found that C3G treatment caused a decrease in activation of the pro-apoptotic proteins caspase-3/-8 in H. pylori-infected cells leading to a decrease in cell death. Our data suggest that consumption of foods containing anthocyanin may be beneficial in reducing cell damage due to H. pylori infection.

Kim, Sa-Hyun; Woo, Hyunjun; Park, Min; Rhee, Ki-Jong; Moon, Cheol; Lee, Dongsup; Seo, Woo Duck; Kim, Jong Bae

2014-01-01

159

Virulence attributes of Helicobacter pylori isolates & their association with gastroduodenal disease  

PubMed Central

Background & objectives Certain genotype(s) of Helicobacter pylori strains may play important role in the development of gastric cancer (GC) and peptic ulcer disease (PUD). This study was undertaken to investigate the association of cagA, cagA3/ region subtypes, babA2 and vacA genotypes of H. pylori with GC, PUD and non-ulcer dyspepsia (NUD) as there are no such studies from India. Methods A total of 348 consecutive adult patients (NUD 241, PUD 45, GC 62) undergoing upper gastrointestinal endoscopy between September 2002 and May 2007 in a tertiary referral centre at Lucknow, north India, were enrolled. H. pylori infection was diagnosed by rapid urease test, culture, histopathology and PCR. Genotyping for cagA, cagA3/ subtypes, babA2 and vacA was performed by PCR using sequence specific primers. Results H. pylori infection was higher in patients with PUD than with GC (80 vs. 56.5%, P < 0.01) and NUD (80 vs. 55.2%, P= 0.002). cagA positive H. pylori isolates were detected in 80 per cent in GC, 83.3 per cent in PUD and 76.7 per cent in NUD with no significant difference among them. Only A subtype of cagA3/ was detected and its distribution in GC, PUD and NUD was 68.8, 69.4 and 52.6 per cent respectively. Presence of babA2 genotype was 31.4 per cent and it had significant association with PUD when compared with NUD (52.8 vs. 26.3%, P<0.003). On univariate regression analysis, s1a allele was associated with GC (P<0.050) and s1a/m2 vacA genotype with both GC (P=0.014) and PUD (P=0.016). Interpretation & conclusions H. pylori infection was strongly associated with PUD with a very high proportion of patients with GC have s1a allele and s1a/m2 vacA genotype. Both s1a/m2 vacA genotype and babA2 are associated with PUD. The study shows that different virulence attributes of H. pylori are involved in different gastroduodenal disorders.

Saxena, A.; Shukla, S.; Prasad, K.N.; Ghoshal, U.C.

2011-01-01

160

High prevalence of virulent Helicobacter pylori strains in symptomatic Bulgarian patients.  

PubMed

The aim of the study was to evaluate the prevalence of main virulence genes in Helicobacter pylori strains from 116 patients with peptic ulcers (41 cases) and nonulcer diseases (75) by polymerase chain reaction (PCR) with pure cultures and to compare the results with those by multiplex PCR in 39 H. pylori-positive gastric biopsies in another center in Sofia, Bulgaria. Strain susceptibility to amoxicillin, metronidazole, and clarithromycin was determined by agar dilution method. By PCR with pure cultures, coinfections with multiple H. pylori strains were found in 8 (6.9%) patients who were excluded from the statistical analysis. Prevalence of toxigenic type vacA s1 was higher (91.7%) than that usually reported in Europe. cagA-positive genotype was detected in most (81.5%) strains, and almost all of them harbored vacA s1 genotype. Strains with cagA+/vacA s1a genotype were more common (80.6%) than the other genotypes (19.4%, P = 0.0001). The ulcer patients had more often virulent strains than the other patients (92.3% versus 75.4% for cagA+, 100.0% versus 87.0% for vacA s1, 100% versus 84.0% for vacA s1a, and 92.3% versus 73.9% for cagA+/vacA s1a, respectively). The prevalence of H. pylori virulence-associated genes was not associated with patients' sex and age or with the antibacterial resistance of strains. The most common H. pylori genotype was cagA+/vacA s1a. Similar prevalence of cagA-positive (82.1%), vacA s1 (97.4%), and cagA+/vacA s1 strains (79.5%) was found by multiplex PCR in gastric biopsies in the 2nd center. In conclusion, H. pylori strains with virulent genotypes are widespread in symptomatic Bulgarian patients. PMID:19631090

Boyanova, Lyudmila; Markovska, Rumiana; Yordanov, Daniel; Marina, Maya; Ivanova, Katusha; Panayotov, Stephan; Gergova, Galina; Mitov, Ivan

2009-08-01

161

Role of Connexin 43 in Helicobacter pylori VacA-Induced Cell Death  

PubMed Central

Helicobacter pylori colonizes the human stomach and confers an increased risk for the development of peptic ulceration, noncardia gastric adenocarcinoma, and gastric lymphoma. A secreted H. pylori toxin, VacA, can cause multiple alterations in gastric epithelial cells, including cell death. In this study, we sought to identify host cell factors that are required for VacA-induced cell death. To do this, we analyzed gene trap and short hairpin RNA (shRNA) libraries in AZ-521 human gastric epithelial cells and selected for VacA-resistant clones. Among the VacA-resistant clones, we identified multiple gene trap library clones and an shRNA library clone with disrupted expression of connexin 43 (Cx43) (also known as gap junction protein alpha 1 [GJA1]). Further experiments with Cx43-specific shRNAs confirmed that a reduction in Cx43 expression results in resistance to VacA-induced cell death. Immunofluorescence microscopy experiments indicated that VacA did not colocalize with Cx43. We detected production of the Cx43 protein in AZ-521 cells but not in AGS, HeLa, or RK-13 cells, and correspondingly, AZ-521 cells were the most susceptible to VacA-induced cell death. When Cx43 was expressed in HeLa cells, the cells became more susceptible to VacA. These results indicate that Cx43 is a host cell constituent that contributes to VacA-induced cell death and that variation among cell types in susceptibility to VacA-induced cell death is attributable at least in part to cell type-specific differences in Cx43 production.

Radin, Jana N.; Gonzalez-Rivera, Christian; Frick-Cheng, Arwen E.; Sheng, Jinsong; Gaddy, Jennifer A.; Rubin, Donald H.; Algood, Holly M. Scott; McClain, Mark S.

2014-01-01

162

Investigation of the association between clinical outcome and the cag pathogenicity-island and other virulence genes of Helicobacter pylori isolates from patients with dyspepsia in Eastern Turkey  

PubMed Central

The aims of our work were to determine the presence of the cag pathogenicity-island (cag PAI) and other virulence genes of Helicobacter pylori recovered from patients with gastritis and peptic ulcer, and to investigate the correlation of these virulence genes with clinical outcome. The presence of the cagA, the promoter regions of cagA, cagE, cagT, and the left end of cag-PAI (LEC), cag right junction (cagRJ), the plasticity region open reading frames (ORFs), vacA and oipA genes among 69 H. pylori isolates were determined by polymerase chain reaction. Intact cag PAI was detected in only one (1.4%) isolate. The cagA gene was identified in 52.1% and 76.2% of isolates from patients with dyspepsia (gastritis and peptic ulcer), respectively. The plasticity region ORFs i.e. JHP912 and JHP931 were predominantly detected in isolates from peptic ulcer. Less than 25% of the isolates carried other ORFs. Types I, II and III were the most commonly found among the isolates. None of the isolates possessed type Ib, 1c, IIIb, IV and V motifs. The most commonly vacA genotypes were s1am1a and s1m2 in isolates with peptic ulcer and gastritis, respectively. The results confirmed that the prevalence of oipA (Hp0638) gene was 75% and 85.7% in patients with gastritis and peptic ulcer, respectively. Furthermore, vacA s1am1a positivity was significantly related to peptic ulcer (p < 0.05).

Ozbey, Gokben; Demirel, Ulvi; Aygun, Cem; Ertas, Hasan Basri

2013-01-01

163

Investigation of the association between clinical outcome and the cag pathogenicity-island and other virulence genes of Helicobacter pylori isolates from patients with dyspepsia in Eastern Turkey.  

PubMed

The aims of our work were to determine the presence of the cag pathogenicity-island (cag PAI) and other virulence genes of Helicobacter pylori recovered from patients with gastritis and peptic ulcer, and to investigate the correlation of these virulence genes with clinical outcome. The presence of the cagA, the promoter regions of cagA, cagE, cagT, and the left end of cag-PAI (LEC), cag right junction (cagRJ), the plasticity region open reading frames (ORFs), vacA and oipA genes among 69 H. pylori isolates were determined by polymerase chain reaction. Intact cag PAI was detected in only one (1.4%) isolate. The cagA gene was identified in 52.1% and 76.2% of isolates from patients with dyspepsia (gastritis and peptic ulcer), respectively. The plasticity region ORFs i.e. JHP912 and JHP931 were predominantly detected in isolates from peptic ulcer. Less than 25% of the isolates carried other ORFs. Types I, II and III were the most commonly found among the isolates. None of the isolates possessed type Ib, 1c, IIIb, IV and V motifs. The most commonly vacA genotypes were s1am1a and s1m2 in isolates with peptic ulcer and gastritis, respectively. The results confirmed that the prevalence of oipA (Hp0638) gene was 75% and 85.7% in patients with gastritis and peptic ulcer, respectively. Furthermore, vacA s1am1a positivity was significantly related to peptic ulcer (p < 0.05). PMID:24688521

Ozbey, Gokben; Demirel, Ulvi; Aygun, Cem; Ertas, Hasan Basri

2013-12-01

164

Role of connexin 43 in Helicobacter pylori VacA-induced cell death.  

PubMed

Helicobacter pylori colonizes the human stomach and confers an increased risk for the development of peptic ulceration, noncardia gastric adenocarcinoma, and gastric lymphoma. A secreted H. pylori toxin, VacA, can cause multiple alterations in gastric epithelial cells, including cell death. In this study, we sought to identify host cell factors that are required for VacA-induced cell death. To do this, we analyzed gene trap and short hairpin RNA (shRNA) libraries in AZ-521 human gastric epithelial cells and selected for VacA-resistant clones. Among the VacA-resistant clones, we identified multiple gene trap library clones and an shRNA library clone with disrupted expression of connexin 43 (Cx43) (also known as gap junction protein alpha 1 [GJA1]). Further experiments with Cx43-specific shRNAs confirmed that a reduction in Cx43 expression results in resistance to VacA-induced cell death. Immunofluorescence microscopy experiments indicated that VacA did not colocalize with Cx43. We detected production of the Cx43 protein in AZ-521 cells but not in AGS, HeLa, or RK-13 cells, and correspondingly, AZ-521 cells were the most susceptible to VacA-induced cell death. When Cx43 was expressed in HeLa cells, the cells became more susceptible to VacA. These results indicate that Cx43 is a host cell constituent that contributes to VacA-induced cell death and that variation among cell types in susceptibility to VacA-induced cell death is attributable at least in part to cell type-specific differences in Cx43 production. PMID:24191302

Radin, Jana N; González-Rivera, Christian; Frick-Cheng, Arwen E; Sheng, Jinsong; Gaddy, Jennifer A; Rubin, Donald H; Algood, Holly M Scott; McClain, Mark S; Cover, Timothy L

2014-01-01

165

Cluster headache: transcranial Doppler assessment of dynamic cerebral circulatory changes during hypocapnia and attack.  

PubMed

Transcranial Doppler ultrasound (TCD) investigations have been carried out in cluster headache patients (8 during remission and 6 during bout) and 14 healthy subjects, to assess cerebral vasomotor reactivity (VMR) to hypocapnia induced by voluntary hyperventilation. VMR was expressed as the relative change in blood flow velocity (V) (%) as a function of the reduction in end-tidal PCO2 (PETCO2) (kPa), i.e. V/P ETCO2. TCD with simultaneous PETCO2 monitoring, was also performed in 5 patients during spontaneous attacks. Prior to hyperventilation, there was bilaterally lower anterior cerebral artery velocity (VACA) during the bout than during remission (P < 0.05 on the symptomatic side), and also lower than in the controls. During remission, VACA was higher on the symptomatic side than on the other side (P < 0.05). ACA also showed a lower VMR during the bout than during remission, and it was also lower than in controls (bout vs. remission on the non-symptomatic side, P < 0.01; on the symptomatic side, P > 0.1). Approximately 30 minutes after the onset of attack, PETCO2 started to decrease gradually from 4.65 to 4.10 kPa in one patient with severe attack. The VACA decreased markedly and bilaterally already at an early stage of the attack, i.e. prior to the hyperventilation. Middle cerebral artery velocity tended to decrease 30 minutes after the onset of attack on the symptomatic side, and 50 minutes after onset on the non-symptomatic side. It is concluded that the vascular changes observed most likely are secondary phenomena during the cluster headache attack. PMID:7903291

Shen, J M; Johnsen, H J; Juul, R

1993-10-01

166

Comparative Genomic Analysis of East Asian and Non-Asian Helicobacter pylori Strains Identifies Rapidly Evolving Genes  

PubMed Central

Helicobacter pylori infection is a risk factor for the development of gastric adenocarcinoma, a disease that has a high incidence in East Asia. Genes that are highly divergent in East Asian H. pylori strains compared to non-Asian strains are predicted to encode proteins that differ in functional activity and could represent novel determinants of virulence. To identify such proteins, we undertook a comparative analysis of sixteen H. pylori genomes, selected equally from strains classified as East Asian or non-Asian. As expected, the deduced sequences of two known virulence determinants (CagA and VacA) are highly divergent, with 77% and 87% mean amino acid sequence identities between East Asian and non-Asian groups, respectively. In total, we identified 57 protein sequences that are highly divergent between East Asian and non-Asian strains, but relatively conserved within East Asian strains. The most highly represented functional groups are hypothetical proteins, cell envelope proteins and proteins involved in DNA metabolism. Among the divergent genes with known or predicted functions, population genetic analyses indicate that 86% exhibit evidence of positive selection. McDonald-Kreitman tests further indicate that about one third of these highly divergent genes, including cagA and vacA, are under diversifying selection. We conclude that, similar to cagA and vacA, most of the divergent genes identified in this study evolved under positive selection, and represent candidate factors that may account for the disproportionately high incidence of gastric cancer associated with East Asian H. pylori strains. Moreover, these divergent genes represent robust biomarkers that can be used to differentiate East Asian and non-Asian H. pylori strains.

Duncan, Stacy S.; Valk, Pieter L.; McClain, Mark S.; Shaffer, Carrie L.; Metcalf, Jason A.; Bordenstein, Seth R.; Cover, Timothy L.

2013-01-01

167

First-degree relatives of early-onset gastric cancer patients show a high risk for gastric cancer: phenotype and genotype profile.  

PubMed

First-degree relatives (FDR) of early-onset gastric cancer (EOGC) is presumed to be a population with a distinct molecular and phenotypic profile, regarding the prevalence of gastric premalignant conditions and the association with Helicobacter pylori infection and host proinflammatory gene polymorphisms. A case-control study was conducted with FDR of EOGC patients (n?=?103) and age and gender matched controls (n?=?101; ranging from spouses to neighbors and dyspeptics). Upper endoscopy was performed, Operative Link on Gastritis Assessment (OLGA) system used for staging and H. pylori (cagA and vacA) and host IL1B-511, IL1RN intron2 VNTR and IFNGR1-56 genotyping. Seventy percent of cases showed atrophy, while 19 % presented with high-stage gastritis (OLGA stage III or IV) (p?vacA s1 and vacA m1 + strains significantly associated with the presence of atrophy; individuals homozygous for IL1B-511*T present a significantly higher risk for dysplasia. An increased global prevalence of IFNGR1-56*T/*T polymorphism (37 % in cases vs 24 % in controls; p?=?0.03) was observed with no association with atrophic changes or dysplasia. All trends observed were kept when comparing FDR of EOGC with spouses, neighbors, or dyspeptic controls. We demonstrated that FDR of EOGC patients have an increased prevalence of high-risk OLGA stages and dysplasia that seem to be associated with high virulence H. pylori strains and pro-inflammatory host genotypes, including a possible population-specific risk marker. FDR of EOGC patients may merit specific management through endoscopic and histopathological adequate assessment of gastric mucosa and surveillance. PMID:23887584

Marcos-Pinto, Ricardo; Dinis-Ribeiro, Mário; Carneiro, Fátima; Wen, Xiaogang; Lopes, Carlos; Figueiredo, Céu; Machado, José Carlos; Ferreira, Rui M; Reis, Celso A; Canedo, Paulo; Durães, Cecília; Ferreira, José; Pedroto, Isabel; Areias, Jorge

2013-09-01

168

Analysis of virulence factors of Helicobacter pylori isolated from a Vietnamese population  

PubMed Central

Background The incidence of gastric cancer differs among countries in Asia, and it has been suggested that virulence factors associated with Helicobacter pylori are partly responsible. The aim of this study was to investigate several genetic factors regarded as virulence or molecular epidemiologic markers in H. pylori isolates from Vietnamese subjects. Results The cagA, vacA and cag right-end junction genotypes of 103 H. pylori strains from Vietnam (54 from Hanoi and 49 from Ho Chi Minh) were determined by PCR and sequencing. Three types of deletion in the region located upstream of the cagA Glu-Pro-Ile-Tyr-Ala (EPIYA) repeat region were identified: the 39-bp deletion type, the 18-bp deletion type, and the no-deletion type. The majority of strains studied (77%; 80/103) had the 18-bp deletion irrespective of geographical location in the country or clinical outcome. All of the 39-bp and 18-bp deletion-type strains possessed the East Asian type cagA repeat region. The type II cag right-end junction genotype was predominant (84%). The vacA m1 genotype was significantly more common in strains isolated in Hanoi, where the incidence of gastric cancer is higher, than in strains from Ho Chi Minh. Conclusion Pre-EPIYA-region typing of the cagA gene could provide a new genetic marker of H. pylori genomic diversity. Our data support the hypothesis that vacA m1 is closely associated with gastric carcinogenesis.

2009-01-01

169

Sedimentation History of Lago Guayabal, Puerto Rico, 1913-2001  

USGS Publications Warehouse

The Lago Guayabal dam, located in the municipality of Villalba in southern Puerto Rico, was constructed in 1913 for irrigation of croplands in the southern coastal plains and is owned and operated by the Puerto Rico Electric Power Authority. The reservoir had an original storage capacity of 11.82 million cubic meters and a drainage area upstream of the dam of 112 square kilometers. Sedimentation has reduced the storage capacity to 6.12 million cubic meters in 2001, which represents a storage loss of about 48 percent. However, the actual sediment accumulation in the reservoir during the 88 years is greater, because some sediment removal was conducted between 1940 and 1948 by dredging and sluicing. This report summarizes the historical data from a 1913 land survey and eight bathymetric surveys conducted between 1914 and 2001, and the relation of high sedimentation to agricultural land practices within the Lago Guayabal basin and six major hurricanes which made landfall on the island. The reservoir had an area-normalized sedimentation rate of about 1,863 cubic meters per square kilometer per year between 1913 and 1936 from a 112 square kilometer basin. In 1972, a new dam upstream along the Rio Toa Vaca impounded runoff from 57.5 square kilometers, and sediment transport to Lago Guayabal was reduced. A comparison of bathymetric survey results between 1972 and 2001 indicates an area-normalized sedimentation rate of 1,120 cubic meters per square kilometer per year or about 60 percent of the rate between 1913 and 1936. The significant reduction (almost half) of the sedimentation rate after the Toa Vaca dam was built may indicate that erosion susceptibility of the Rio Toa Vaca watershed is about twice that of the Rio Jacaguas watershed impounded by Lago Guayabal.

Soler-Lopez, Luis R.

2003-01-01

170

Conquistadors  

NSDL National Science Digital Library

To accompany its television program, PBS presents this Website. Designed for students in grades 8-12, Conquistadors follows the Spanish Conquistadors' exploration of the New World from 1500 to 1550 and their contact with Native Americans. There are four main sections of the site: Cortez and the Aztecs in Mexico, Peru -- the Inca Empire and Pizzaro, Amazonia and the Quest for El Dorado, and North America: Cabeza de Vaca and the American Southwest. The site also features a timeline, teaching guides, and a journal kept by the series host, Michael Wood, as he made the documentary and traveled the Conquistadors' path.

2001-01-01

171

Inhibition of cell-cycle progression in HeLa cells by HY52, a novel cyclin-dependent kinase inhibitor isolated from Bauhinia forficata  

Microsoft Academic Search

In the course of screening for a novel inhibitor of cyclin-dependent kinase (CDK), HY52 (C17H30O2N2; molecular weight 294) was isolated from the leaves of Pata de Vaca (Bauhinia forficata). The growth of HeLa cells was inhibited in a dose-dependent manner when treated with 0.07 to 0.41mM of HY52 for 24h (IC50: 0.11mM). Furthermore, HY52 showed the selective inhibitory activity on

Haeyoung Lim; Min Kyoung Kim; Yoongho Lim; Youl-Hee Cho; Chul-Hoon Lee

2006-01-01

172

Vestiges of an Ordovician west-vergent thin-skinned Ocloyic thrust belt in the Argentine Precordillera, southern Central Andes  

NASA Astrophysics Data System (ADS)

Collision of the down-going, Laurentia-derived Argentine Precordillera terrane with the Gondwanan margin drove the Ordovician Ocloyic orogeny, including subduction volcanism, metamorphism, and top-to-west shearing east of the Precordillera. In the Precordillera, above passive-margin carbonates (Lower Ordovician San Juan Limestone and older carbonates), a Middle to Upper Ordovician westward-prograding synorogenic clastic wedge of black shale (Gualcamayo Shale) and coarser clastic sediment (Las Vacas Conglomerate and Trapiche Formation) fills a peripheral foreland basin. New research has identified vestiges of a west-directed thin-skinned Ocloyic foreland thrust belt that has been fragmented by east-directed Andean thrusting. The El Corral thrust sheet, with hanging-wall detachment in the San Juan Limestone, extends over a west-directed footwall frontal ramp and extensive flat to low-angle footwall cutoff in the Gualcamayo and Las Vacas formations. Las Vacas conglomerates in the footwall include olistoliths (10-m scale) exclusively of San Juan Limestone and Gualcamayo Shale; the beds in some olistoliths are folded. The advancing El Corral thrust sheet successively supplied and overrode the stratigraphically restricted olistoliths. In the El Corral footwall, tight west-vergent folds and faults within an anticlinorium in the San Juan Limestone and Gualcamayo Shale suggest a deeper (unexposed) thrust fault, the Los Celestitos fault. West of the anticlinorium, easterly dip (restored to remove Andean deformation) beneath an angular unconformity between Las Vacas and Trapiche beds is consistent geometrically with the trailing limb of a west-vergent fault-propagation anticline in the hanging wall of the subsurface Los Celestitos fault. The same angular unconformity truncates the El Corral fault and hanging-wall strata. In the Trapiche Formation, contrasting sedimentary facies from sandy turbidites westward to limestone-clast megabeds and olistoliths suggest another frontal ramp from a stratigraphically deeper detachment in a break-forward sequence. None of these observations separately defines an Ocloyic thrust belt. Taken together, however, these vestiges of thrust-belt style indicate the consistent geometry of an Ordovician west-vergent thin-skinned Ocloyic thrust belt.

Thomas, William A.; Astini, Ricardo A.

2007-08-01

173

Suppression of density limit disruptions using vacuum rotational transform on the CTH experiment  

NASA Astrophysics Data System (ADS)

Experiments on the Compact Toroidal Hybrid (CTH) demonstrate the suppression of disruptions in tokamak discharges in which a fraction of the net rotational transform is produced by torsatron coils. Torsatron plasmas with adjustable vacuum transform are generated in CTH by ECRH, followed by ramp-up of the plasma current and density. Neither density nor current-driven disruptions are observed when the vacuum rotational transform is above a threshold value of vac(a) ˜ 0.11. At lower vacuum transform levels, density limit disruptions can occur in CTH when gas puffing produces line-averaged densities near the Greenwald limit. These density limit disruptions are preceded by growing m/n=2/1 MHD oscillations prior to the disruptiion, indicating internal tearing mode activity. Above the apparent threshold value of vac(a) ˜ 0.11, the plasma current declines as the density is increased, indicating cooling of the plasma without an associated major disruption. Vertical displacement events are also reduced by the addition of vacuum transform. Disruptions in plasmas with varying levels of applied vacuum transform will be discussed in light of other diagnostic measurements and modeling. Supported by US. Department of Energy Grant No. DE-FG02-00ER54610

Knowlton, S. F.; Hanson, J. D.; Hartwell, G. J.; Herfindal, J. L.; Ma, X.; Maurer, D. A.; Archmiller, M. C.; Pandya, M.

2012-10-01

174

Helicobacter pylori virulence factors as tools to study human migrations.  

PubMed

Helicobacter pylori is one of the most common infections worldwide. In most individuals it consists in a lifelong host-pathogen relationship without consequences, but in some subjects it is associated with peptic ulcer disease and gastric cancer. Polymorphism in genes that code bacterial virulence factors, cagA and vacA, are independently associated with the infection severe outcomes and are geographically diverse. In the last decade, accumulated knowledge allowed to characterize typical H. pylori strain patterns for all the major human populations; patterns that can be used to study the origin of specific human groups. Thus, the presence or absence of cagA, cagA EPIYA genotypes, and vacA subtypes can be used as tools to study not only the geographic origin of specific human populations, but also to identify markers of historical contact between different ethnicities. We report here a study including a set of native Amazon Amerindians that had supposedly been some, but little, contact with European Brazilian colonizer and/or African slaves. They harbor H. pylori strains in a mixed pattern with Asian and Iberian Peninsula characteristics. It is possible that this finding represents H. pylori recombination upon short contact between human groups. Alternatively, it could be due to a founder effect from a small cluster of Asian origin native Americans. PMID:20144640

Queiroz, Dulciene Maria de Magalhães; Cunha, Roberto Penna de Almeida; Saraiva, Ivan Euclides Borges; Rocha, Andreia Maria Camargos

2010-12-15

175

Therapeutic intragastric vaccination against Helicobacter pylori in mice eradicates an otherwise chronic infection and confers protection against reinfection.  

PubMed Central

Chronic infection of the gastroduodenal mucosae by the gram-negative spiral bacterium Helicobacter pylori is responsible for chronic active gastritis, peptic ulcers, and gastric cancers such as adenocarcinoma and low-grade gastric B-cell lymphoma. The success of eradication by antibiotic therapy is being rapidly hampered by the increasing occurrence of antibiotic-resistant strains. An attractive alternative approach to combat this infection is represented by the therapeutic use of vaccines. In the present work, we have exploited the mouse model of persistent infection by mouse-adapted H. pylori strains that we have developed to assess the feasibility of the therapeutic use of vaccines against infection. We report that an otherwise chronic H. pylori infection in mice can be successfully eradicated by intragastric vaccination with H. pylori antigens such as recombinant VacA and CagA, which were administered together with a genetically detoxified mutant of the heat-labile enterotoxin of Escherichia coli (referred to as LTK63), in which the serine in position 63 was replaced by a lysine. Moreover, we show that therapeutic vaccination confers efficacious protection against reinfection. These results represent strong evidence of the feasibility of therapeutic use of VacA- or CagA-based vaccine formulations against H. pylori infection in an animal model and give substantial preclinical support to the application of this kind of approach in human clinical trials.

Ghiara, P; Rossi, M; Marchetti, M; Di Tommaso, A; Vindigni, C; Ciampolini, F; Covacci, A; Telford, J L; De Magistris, M T; Pizza, M; Rappuoli, R; Del Giudice, G

1997-01-01

176

Preliminary design of a special casing joint for a well equipped twin horizontal drainholes in the Oxnard field  

SciTech Connect

The Oxnard field is presently under production,with a typical average monthly oil production of about 70,000 B, of which the Vaca Tar sand represents more than half.It is Unitized and operated under cyclic steam injection.The hot Tar and produced water are lifted to the surface with rod pumps equipped for injection of a diluent. The produced WOR is about 2.5 and the GOR is about 150 scf/B. The Vaca Tar sand originally contained about 400 million STB. The estimated recoverable reserve under full-scale cyclic steam injection is 100 to 120 Million STB. Under steamflood, it might reach 240 million STB. The objectives of this field test are: (1) increase well productivity by using a vertical well equipped with twin horizontal drainholes, each of about 1,000 ft. reach; (2) maximize the well draw-down by locating the horizontal wells near the base of the sand layer; (3) reduce capital cost by using twin drainholes connected to the same vertical cased well; (4) reduce operating expenses by eliminating the need for a service rig to pull-out the rods and pump before each steam injection cycle; and (5) be adaptable to other operating modes.

Not Available

1993-12-31

177

Immune responses to Helicobacter pylori infection.  

PubMed

Helicobacter pylori (H. pylori) infection is one of the most common infections in human beings worldwide. H. pylori express lipopolysaccharides and flagellin that do not activate efficiently Toll-like receptors and express dedicated effectors, such as ?-glutamyl transpeptidase, vacuolating cytotoxin (vacA), arginase, that actively induce tolerogenic signals. In this perspective, H. pylori can be considered as a commensal bacteria belonging to the stomach microbiota. However, when present in the stomach, H. pylori reduce the overall diversity of the gastric microbiota and promote gastric inflammation by inducing Nod1-dependent pro-inflammatory program and by activating neutrophils through the production of a neutrophil activating protein. The maintenance of a chronic inflammation in the gastric mucosa and the direct action of virulence factors (vacA and cytotoxin-associated gene A) confer pro-carcinogenic activities to H. pylori. Hence, H. pylori cannot be considered as symbiotic bacteria but rather as part of the pathobiont. The development of a H. pylori vaccine will bring health benefits for individuals infected with antibiotic resistant H. pylori strains and population of underdeveloped countries. PMID:24914318

Moyat, Mati; Velin, Dominique

2014-05-21

178

Plausible asteroidal analogs for enstatite chondrites and mesosiderites  

NASA Astrophysics Data System (ADS)

We present new irradiation experiments performed on the enstatite chondrite Eagle (EL6) and the mesosiderite Vaca Muerta. These experiments were performed with the aims of (a) quantifying the spectral effect of the solar wind on their parent asteroid surfaces and (b) identifying their parent bodies within the asteroid belt. For Vaca Muerta we observe a reddening and darkening of the reflectance spectrum with progressive irradiation, consistent with what is observed in the cases of silicates and silicate-rich meteorites such as OCs and HEDs. For Eagle we observe little spectral variation, and therefore we do not expect to observe a significant spectral difference between EC meteorites and their parent bodies. We evaluated possible parent bodies for both meteorites by comparing their VNIR spectra (before and after irradiation) with those of ~400 main-belt asteroids. We found that 21 Lutetia (Rosetta's forthcoming fly-by target) and 97 Klotho have physical properties compatible with those of enstatite chondrite meteorites while 201 Penelope, 250 Bettina and 337 Devosa are compatible with the properties of mesosiderites.

Vernazza, P.; Brunetto, R.; Binzel, R. P.; Perron, C.; Fulvio, D.; Strazzulla, G.; Fulchignoni, M.

2009-04-01

179

Sulfuric acid measurements in the exhaust plume of a jet aircraft in flight: Implications for the sulfuric acid formation efficiency  

NASA Astrophysics Data System (ADS)

Sulfuric acid concentrations were measured in the exhaust plume of a B737-300 aircraft in flight. The measurements were made onboard of the German research aircraft Falcon using the Volatile Aerosol Component Analyzer (VACA). The VACA measures total H2SO4, which is the sum of gaseous H2SO4 and aerosol H2SO4. Measurements took place at distances of 25-200 m behind the B737 corresponding to plume ages of about 0.1-1 seconds. The fuel sulfur content (FSC) of the fuel burned by the B737 engines was alternatively 2.6 and 56 mg sulfur per kilogram fuel (ppmm). H2SO4 concentrations measured in the plume for the 56 ppmm sulfur case were up to ~600 pptv. The average concentration of H2SO4 measured in the ambient atmosphere outside the aircraft plume was 88 pptv, the maximum ambient atmospheric H2SO4 was ~300 pptv. Average efficiencies ??CO2 = 3.3 +/- 1.8% and ??T = 2.9 +/- 1.6% for fuel sulfur conversion to sulfuric acid were inferred when relating the H2SO4 data to measurements of the plume tracers ?CO2 and ?T.

Curtius, J.; Arnold, F.; Schulte, P.

2002-04-01

180

Upwelling-triggered near-geostrophic recirculation in an equatorward facing embayment  

NASA Astrophysics Data System (ADS)

Underway current velocity profiles were combined with hydrographic profiles at the entrance to Tongoy Bay, an equatorward facing bay in north-central Chile, with the objective of determining its exchange hydrodynamics. To the west, Tongoy Bay is bounded by Lengua de Vaca Point, a ˜6 km-long northward protruding peninsula. Observations were obtained during three surveys (April 2005, December 2005, May 2009) along cross-bay transects for at least one full day. During the surveys, winds were upwelling-favorable and displayed diurnal variations. Non-tidal (tidally averaged) flows showed a consistent clockwise or southern hemisphere cyclonic, recirculation during the three surveys. This recirculation was likely part of a cyclonic gyre (10-20 km in diameter), not entirely resolved by the surveys, and formed by flow separation off Lengua de Vaca Point. Estimates of the baroclinic pressure gradient, combined with analytical solutions of density-driven and wind-driven flows, indicated that the recirculation in Tongoy Bay was nearly in geostrophic balance. An ageostrophic contribution to the dynamics was related to frictional effects derived from local upwelling-favorable winds. A linear superposition of the analytically derived density-driven and wind-driven exchange resulted in a flow pattern that resembled the observed net exchange flows at the bay mouth.

Moraga-Opazo, Julio; Valle-Levinson, Arnoldo; Ramos, Marcel; Pizarro-Koch, Matías

2011-12-01

181

Plausible parent bodies for enstatite chondrites and mesosiderites: Implications for Lutetia's fly-by  

NASA Astrophysics Data System (ADS)

We present new irradiation experiments performed on the enstatite chondrite Eagle (EL6) and the mesosiderite Vaca Muerta. These experiments were performed with the aims of (a) quantifying the spectral effect of the solar wind on their parent asteroid surfaces and (b) identifying their parent bodies within the asteroid belt. For Vaca Muerta we observe a reddening and darkening of the reflectance spectrum with progressive irradiation, consistent with what is observed in the cases of silicates and silicate-rich meteorites such as OCs and HEDs. For Eagle we observe little spectral variation, and therefore we do not expect to observe a significant spectral difference between EC meteorites and their parent bodies. We evaluated possible parent bodies for both meteorites by comparing their VNIR spectra (before and after irradiation) with those of ˜400 main-belt asteroids. We found that 21 Lutetia (Rosetta's forthcoming fly-by target) and 97 Klotho (both Xc types in the new Bus-DeMeo taxonomy) have physical properties compatible with those of enstatite chondrite meteorites while 201 Penelope, 250 Bettina and 337 Devosa (all three are Xk types in the Bus-DeMeo taxonomy) are compatible with the properties of mesosiderites.

Vernazza, P.; Brunetto, R.; Binzel, R. P.; Perron, C.; Fulvio, D.; Strazzulla, G.; Fulchignoni, M.

2009-08-01

182

Molecular analysis of Helicobacter pylori virulent-associated genes in hepatobiliary patients  

PubMed Central

Objectives The Helicobacter pylori virulence-associated genes in hepatobiliary patients, including vacA, iceA, babA2, cagA and cagE, have not been reported. The aim of this study was to investigate these genes and the association of those and the clinical outcomes in hepatobiliary diseases. Methods Eighty H. pylori-PCR-positive cases were obtained from hepatobiliary patients, representing both cholangiocarcinoma (CCA) (n = 58) and cholelithiasis (n = 22). The diversity of virulence genes was examined by polymerase chain reaction and DNA sequencing. Phylogenetic analysis of cagA was determined using the maximum parsimony method. Results The vacAs1a + c/m1, iceA1 and babA2 genes were the most predominant genotypes in both CCA and cholelithiasis patients. The cagA and cagE genes were found significantly more frequently in patients with CCA than those with cholelithiasis (P < 0.05). The cagA positive samples were the Western-type cagA and showed that almost all of the detected sequences in Thai hepatobiliary and Thai gastric cancer patients were classified in the same cluster but separated from the cluster of Japan and other countries. Conclusions The cagA and cagE genes may be associated in the pathogenesis of hepatobiliary diseases, especially of CCA. Besides the bacterial variation, other host factors may be involved in the pathogenesis of hepatobiliary cancer.

Boonyanugomol, Wongwarut; Chomvarin, Chariya; Sripa, Banchob; Chau-in, Siri; Pugkhem, Ake; Namwat, Wises; Wongboot, Warawan; Khampoosa, Bandit

2012-01-01

183

Immune responses to Helicobacter pylori infection  

PubMed Central

Helicobacter pylori (H. pylori) infection is one of the most common infections in human beings worldwide. H. pylori express lipopolysaccharides and flagellin that do not activate efficiently Toll-like receptors and express dedicated effectors, such as ?-glutamyl transpeptidase, vacuolating cytotoxin (vacA), arginase, that actively induce tolerogenic signals. In this perspective, H. pylori can be considered as a commensal bacteria belonging to the stomach microbiota. However, when present in the stomach, H. pylori reduce the overall diversity of the gastric microbiota and promote gastric inflammation by inducing Nod1-dependent pro-inflammatory program and by activating neutrophils through the production of a neutrophil activating protein. The maintenance of a chronic inflammation in the gastric mucosa and the direct action of virulence factors (vacA and cytotoxin-associated gene A) confer pro-carcinogenic activities to H. pylori. Hence, H. pylori cannot be considered as symbiotic bacteria but rather as part of the pathobiont. The development of a H. pylori vaccine will bring health benefits for individuals infected with antibiotic resistant H. pylori strains and population of underdeveloped countries.

Moyat, Mati; Velin, Dominique

2014-01-01

184

Variable-aperture calorimeter for an unstable resonator.  

PubMed

A new technique for measuring the output power from a cw edge-coupled unstable resonator has been developed and applied to a cw DF laser. An internal-cavity calorimeter was used that permits measurement of output power with a variable rectangular mode geometry while containing the radiation inside the resonator. The variable aperture calorimeter absorbing scraper (VACAS) device consists of an absorbing copper plate calorimeter assembly, which replaces the 45 degrees output coupling mirror of a conventional edge-coupled unstable cavity. A rectangular hole in the plate of variable width w and height h defines a rectangular mode of variable width Mw and height Mh within the geometric optics approximation, where M is the magnification. Two important applications of VACAS are (1) the determination of the optimum mode geometry for a cw diffusion-type chemical laser where there is significant variation in gain across the unstable resonator mode and (2) the determination of the power tradeoff between mode width and the number of folds in a folded unstable resonator configuration. PMID:20165402

Chodzko, R A; Mason, S B; Giedt, R R; Durran, D A

1976-10-01

185

Different risk factors influence peptic ulcer disease development in a Brazilian population  

PubMed Central

AIM: To investigate age, sex, histopathology and Helicobacter pylori (H. pylori) status, as risk factors for gastroduodenal disease outcome in Brazilian dyspeptic patients. METHODS: From all 1466 consecutive dyspeptic patients submitted to upper gastroscopy at Hospital das Clinicas of Marilia, antral biopsy specimens were obtained and subjected to histopathology and H. pylori diagnosis. All patients presenting chronic gastritis (CG) and peptic ulcer (PU) disease localized in the stomach, gastric ulcer (GU) and/or duodenal ulcer (DU) were included in the study. Gastric biopsies (n = 668) positive for H. pylori by rapid urease test were investigated for vacuolating cytotoxin A (vacA) medium (m) region mosaicism by polymerase chain reaction. Logistic regression analysis was performed to verify the association of age, sex, histopathologic alterations, H. pylori diagnosis and vacA m region mosaicism with the incidence of DU, GU and CG in patients. RESULTS: Of 1466 patients submitted to endoscopy, 1060 (72.3%) presented CG [male/female = 506/554; mean age (year) ± SD = 51.2 ± 17.81], 88 (6.0%) presented DU [male/female = 54/34; mean age (year) ± SD = 51.4 ± 17.14], and 75 (5.1%) presented GU [male/female = 54/21; mean age (year) ± SD = 51.3 ± 17.12] and were included in the comparative analysis. Sex and age showed no detectable effect on CG incidence (overall ?2 = 2.1, P = 0.3423). Sex [Odds ratios (OR) = 1.8631, P = 0.0058] but not age (OR = 0.9929, P = 0.2699) was associated with DU and both parameters had a highly significant effect on GU (overall ?2 = 30.5, P < 0.0001). The histopathological results showed a significant contribution of ageing for both atrophy (OR = 1.0297, P < 0.0001) and intestinal metaplasia (OR = 1.0520, P < 0.0001). Presence of H. pylori was significantly associated with decreasing age (OR = 0.9827, P < 0.0001) and with the incidence of DU (OR = 3.6077, P < 0.0001). The prevalence of m1 in DU was statistically significant (OR = 2.3563, P = 0.0018) but not in CG (OR = 2.678, P = 0.0863) and GU (OR = 1.520, P= 0.2863). CONCLUSION: In our population, male gender was a risk factor for PU; ageing for GU, atrophy and metaplasia; and H. pylori of vacA m1 genotype for DU.

Suzuki, Rodrigo Buzinaro; Cola, Rodrigo Faria; Cola, Larissa Tranquilino Bardela; Ferrari, Camila Garcia; Ellinger, Fred; Therezo, Altino Luiz; Silva, Luis Carlos; Eterovic, Andre; Speranca, Marcia Aparecida

2012-01-01

186

Serum Antibodies Positivity to 12 Helicobacter pylori Virulence Antigens in Patients with Benign or Malignant Gastroduodenal Diseases - Cross-sectional Study  

PubMed Central

Aim To investigate the association of gastric histological and endoscopic findings in patients with Helicobacter pylori (H. pylori), according to presence of seropositivity to 12 bacterial virulence antigens. Methods This is a cross-sectional single-center study of 360 consecutive outpatients referred in the period of one year to upper gastrointestinal endoscopy because of dyspeptic complaints. Patients sera were tested by Western blot method to determine the presence of serum antibodies to bacterial virulence antigens – p120 (CagA – cytotoxin-associated antigen), p95 (VacA – vacuolating cytotoxin), p67 (FSH – flagellar sheath protein), p66 (UreB – urease enzyme heavy subunit), p57 (HSP homologue – heath shock protein homologue), p54 (flagellin), p33, p30 (OMP – outer membrane protein), p29 (UreA – urease enzyme light subunit), p26, p19, and p17. Upper gastrointestinal endoscopy was performed, endoscopic diagnosis recorded, and 4 mucosal biopsy samples were obtained and assessed according to Updated Sydney protocol. Results The sera of 207 patients were analyzed. Thirty patients had gastric adenocarcinoma, 126 peptic ulcers, and 51 normal finding. p120 (CagA) seropositivity was significantly more often present in patients with higher activity grade in the antrum (P?=?0.025), p30 in patients with greater inflammation in the antrum (P?=?0.025) and the corpus (P?=?0.010), p33 in patients with greater inflammation in the corpus (P?=?0.050), and p19 (OMP) in patients with lower intestinal metaplasia grades in the corpus (P?=?0.025). Seroreactivity to all other bacterial proteins showed no association with the histological status of the stomach mucosa. Except for the seropositivity to protein p95 (VacA), which was more often present in patients with duodenal ulcer (P?=?0.006), there was no difference in seroreactivity to other bacterial proteins and upper gastrointestinal endoscopic findings. Conclusions p120 (CagA), p33, p 30 (OMP), and p19 (OMP) seropositivity was more often present in patients with higher grades of the histological parameters of gastritis and seropositivity to protein p95 (VacA) with endoscopic presence of duodenal ulcer. Histological parameters of gastritis are more associated with bacterial virulence than endoscopic findings.

Filipec Kanizaj, Tajana; Katicic, Miroslava; Presecki, Vladimir; Gasparov, Slavko; Colic Cvrlje, Vesna; Kolaric, Branko; Mrzljak, Anna

2009-01-01

187

Faulting evidence of isostatic uplift in the Rincon Mountains metamorphic core complex: An image processing analysis  

NASA Astrophysics Data System (ADS)

This study focuses on the applications of remote sensing techniques and digital analysis to characterizing of tectonic features of the Rincon Mountains metamorphic core complex. Data included Landsat Thematic Mapper (TM) images, digital elevation models (DEM), and digital orthophoto quadrangle quads (DOQQ). The main findings in this study are two nearly orthogonal systems of structures that have never been reported in the Rincon Mountains. The first system, a penetrative faulting system of the footwall rocks, trends N10--30°W. Similar structures identified in other metamorphic core complexes. The second system trends N60--70°E, and has only been alluded indirectly in the literature of metamorphic core complexes. The structures pervade mylonites in Tanque Verde Mountain, Mica Mountain, and the Rincon Peak area. As measured on the imagery, spacing between the N10--30°W lineaments ranges from ˜0.5 to 2 km, and from 0.25 to 1 km for the N60--70°E system. Field inspection reveals that the N10--30°W trending system, are high-angle normal faults dipping mainly to the west. One of the main faults, named here the Cabeza de Vaca fault, has a polished, planar, striated and grooved surface with slickenlines indicating pure normal dip-slip movement (N10°W, 83°SW; slickensides rake 85°SW). The Cabeza de Vaca fault is the eastern boundary of a 2 km-wide graben, with displacement as great as 400 meters. The N10--30°W faults are syn- to post-mylonitic, high-angle normal faults that formed during isostatic uplift of the Rincon core complex during mid-Tertiary time. This interpretation is based on previous works, which report similar fault patterns in other metamorphic core complexes. Faults trending N20--30°W, shape the east flank of Mica Mountain. These faults, on the back dipping mylonitic zone, dip east and may represent late-stage antithetic shear zones. The Cabeza de Vaca fault and the back dipping antithetic faults accommodate as much as 65% of the extension due to doming of the core complex. The N60--70°E structures, not verified as a fault system, are a joint system pervading the footwall rocks of the metamorphic core complex. This system is less systematic. Spacing varies from 0.25 to 1 km. Both systems control the drainage of the mountains.

Rodriguez-Guerra, Edna Patricia

188

The metamorphic history of eucrites and eucrite-related meteorites and the case for late metamorphism  

NASA Astrophysics Data System (ADS)

We report induced thermoluminescence data for separates from three HED meteorites and the Vaca Muerta mesosiderite. The results of thermal modeling of the surface of their parent body are also described. The TL sensitivities for matrix samples from the LEW 85300, 302 and 303 paired eucrites and the Bholghati howardite are lower than the TL sensitivities for the clasts, consistent with regolith working of the matrix in fairly mature regoliths. Within an isochemical series of HED meteorites, TL sensitivity reflects metamorphic intensity, but clast-to-clast variations in the TL sensitivities of the Vaca Muerta mesosiderite and clasts in the EET 87509, 513 and 531 paired howardite primarily reflect differences in mineralogy and petrology. Thermoluminescence peak temperatures indicate that all the components from the LEW 85300, 302 and 303 paired eucrites experienced a reheating event involving temperatures >800oC, thought to have been due to impact heating, and therefore that the event was concurrent with or post-dated brecciation. The Vaca Muerta clasts are essentially unmetamorphosed, but the induced TL data indicate that the remaining HEDM meteorites experienced metamorphism to a variety of intensities but involving temperatures <800oC. Laboratory heating experiments show that temperatures >800oC cause a change in TL peak temperature. Feldspars from a variety of terrestrial and extraterrestrial sources show this behavior, and X-ray diffraction and kinetic studies suggest that it is indirectly related to Al,Si disordering. Cooling rates are not consistent with autometamorphism following the initial igneous event, or with heating by subsequent eruptions of lava onto the surface of the HED parent body. Instead, our thermal models suggest that the metamorphism occurred within a regolith ejecta blanket of up to a few kilometers thick, with different levels of metamorphism corresponding to different thicknesses of blanket, between essentially zero and about 2 km, rather than different burial depths in a regolith of uniform thickness. We argue that metamorphism occurred 3.9 Ga ago and was associated with the resetting of the Ar-Ar system for the HED meteorites.

Sears, Derek W. G.; Symes, Steven J. K.; Batchelor, J. David; Akridge, D. Glen; Benoit, Paul H.

1997-11-01

189

Magnetic fabric and microstructures of Late Paleozoic granitoids from the North Patagonian Massif: Evidence of a collision between Patagonia and Gondwana?  

NASA Astrophysics Data System (ADS)

Widespread Late Paleozoic magmatism in northern Patagonia is a target to test hypotheses on the long standing question over the origin of Patagonia. In recent years, a dispute over whether it is an accreted crustal block that collided with Gondwana in Paleozoic times or an autochthonous part of South America has taken place. As part of a multidisciplinary study, an integrated microstructural and magnetic fabric study was carried out on the Late Carboniferous Yaminué Complex and the Early Permian Navarrete Plutonic Complex, both exposed in the northeastern corner of the North Patagonian Massif (40.5°S, 67.0°W). Other investigated units are the Late Carboniferous Tardugno Granodiorite, the newly defined Cabeza de Vaca Granite and the Late Permian San Martin pluton. Over 300 oriented cores from 60 sites were collected for anisotropy of magnetic susceptibility (AMS) measurements. A systematic analysis of around 100 petrographic thin sections was performed to characterize the microstructures of the different magmatic units. Microstructures in the Yaminué Complex are indicative of a transition from magmatic to solid-state deformation. Microstructures of the orthogneiss of tonalitic composition suggest an early stage in the emplacement history of this complex. The Cabeza de Vaca Granite, intrusive in Yaminué Complex, is the most evolved unit and records less intense high-temperature solid-state deformation which suggests that the stress field that controlled the emplacement of the Yaminué Complex outlasted it. According to petrologic and structural considerations, the Navarrete Plutonic Complex has been subdivided into three facies, i.e. Robaina, Guanacos and Aranda, respectively. Microstructures of the Navarrete Plutonic Complex are mostly magmatic to submagmatic, versus the solid-state fabric that characterizes the Robaina facies at the contact with the Yaminué Complex. Combined analyses of AMS and microstructural data lead us to suggest that the Yaminué Complex, Cabeza de Vaca Granite and possibly Tardugno Granodiorite were intruded during a major compressional event associated with top-to-the-SSW thrusting. This event is most likely related to a frontal collision of the North Patagonian Massif and the southwestern Gondwana margin at around 300 Ma. The Navarrete Plutonic Complex and San Martin pluton were emplaced after that tectonic event, which must have ended by 281 Ma. Previous magmatic, geochronological and paleomagnetic data that suggest close connection of the North Patagonian Massif with the South American Gondwana blocks during the Paleozoic, can be reconciled with a Late Paleozoic collision by a model of a para-autochthonous North Patagonian Massif that rifted away from Gondwana after the Ordovician and collided again in the Late Carboniferous-Early Permian.

López de Luchi, Mónica G.; Rapalini, Augusto E.; Tomezzoli, Renata N.

2010-10-01

190

Diet, microbial virulence, and Helicobacter pylori-induced gastric cancer.  

PubMed

Gastric adenocarcinoma is a leading cause of cancer-related death worldwide, and Helicobacter pylori infection is one of the strongest known risk factors for this malignancy. H. pylori strains exhibit a high level of genetic diversity, and the risk of gastric cancer is higher in persons carrying certain strain types (for example, those that contain a cag pathogenicity island or type s1 vacA alleles) than in persons carrying other strain types. Additional risk factors for gastric cancer include specific human genetic polymorphisms and specific dietary preferences (for example, a high-salt diet or a diet deficient in fruits and vegetables). Finally, iron-deficiency anemia is a risk factor for gastric cancer. Recent studies have provided evidence that several dietary risk factors for gastric cancer directly impact H. pylori virulence. In this review article, we discuss mechanisms by which diet can modulate H. pylori virulence and thereby influence gastric cancer risk. PMID:23989802

Cover, Timothy L; Peek, Richard M

2013-01-01

191

Historical descriptions of some soils and landscapes of Texas  

NASA Astrophysics Data System (ADS)

Europeans explorers, immigrants, and travelers have been crisscrossing Texas for almost 5 centuries, recording their observations of soils and landscapes through the lens of their own times. In the early 16th century, Cabeza de Vaca was struck by how the natives among whom he lived used soil as a part of their diet. In the 17th century, as a member of the La Salle expedition to Texas, Henri Joutel described the soils and landscapes he saw in considerable detail, perhaps with an eye to possible future French settlement. To 19th century immigrants, the soil was the source of their future wealth, but also, so they thought, of the source of the various illnesses that inflicted them. With their distinctive micro-topography and large cracks when dry, Vertisols have elicited some of the most interesting early descriptions of Texas soils.

Schulze, Darrell G.

192

Classification of mafic clasts from mesosiderites - Implications for endogenous igneous processes  

NASA Astrophysics Data System (ADS)

Results are presented from an analysis of 13 igneous pebbles from the Vaca Muerta, EET87500, and Bondoc mesosiderites, using electron microprobe and instrumental neutron activation techniques. These data, combined with literature data on compositions of 43 mesosiderite clasts were used to compile a classification scheme for the various types of mafic silicate clasts that occur in mesosiderites. These clasts were classified into five principal groups: (1) polygenic and monogenic cumulates (30 percent); (2) polygenic basalts (30 percent); (3) quench-textured rocks, comprising two compositional subgroups (those which resemble basaltic eucrites (5 percent), and those which resemble cumulate eucrites (2 percent)); (4) monogenic basalts (11 percent); and (5) ultramafic rocks, consisting mainly of large crystals of orthopyroxene (9 percent) or olivine (4 percent). The conditions under which these clasts were formed are discussed.

Rubin, Alan E.; Mittlefehldt, David W.

1992-02-01

193

Classification of mafic clasts from mesosiderites - Implications for endogenous igneous processes  

NASA Technical Reports Server (NTRS)

Results are presented from an analysis of 13 igneous pebbles from the Vaca Muerta, EET87500, and Bondoc mesosiderites, using electron microprobe and instrumental neutron activation techniques. These data, combined with literature data on compositions of 43 mesosiderite clasts were used to compile a classification scheme for the various types of mafic silicate clasts that occur in mesosiderites. These clasts were classified into five principal groups: (1) polygenic and monogenic cumulates (30 percent); (2) polygenic basalts (30 percent); (3) quench-textured rocks, comprising two compositional subgroups (those which resemble basaltic eucrites (5 percent), and those which resemble cumulate eucrites (2 percent)); (4) monogenic basalts (11 percent); and (5) ultramafic rocks, consisting mainly of large crystals of orthopyroxene (9 percent) or olivine (4 percent). The conditions under which these clasts were formed are discussed.

Rubin, Alan E.; Mittlefehldt, David W.

1992-01-01

194

Niobium-Zirconium Chronometry and Early Solar System Development  

NASA Astrophysics Data System (ADS)

Niobium-92 (92Nb) decays to zirconium-92 (92Zr) with a half-life of 36 million years and can be used to place constraints on the site of p-process nucleosynthesis and the timing of early solar system processes. Recent results have suggested that the initial 92Nb/93Nb of the solar system was high (>10-3). We report Nb-Zr internal isochrons for the ordinary chondrite Estacado (H6) and a clast of the mesosiderite Vaca Muerta, both of which define an initial 92Nb/93Nb ratio of ~10-5. Therefore, the solar system appears to have started with a ratio of <3 × 10-5, which implies that Earth's initial differentiation need not have been as protracted as recently suggested.

Schönbächler, Maria; Rehkämper, Mark; Halliday, Alex N.; Lee, Der-Chuen; Bourot-Denise, Michèle; Zanda, Brigitte; Hattendorf, Bodo; Günther, Detlef

2002-03-01

195

The oldest zircons in the solar system  

NASA Astrophysics Data System (ADS)

The occurrence, chemistry, and U-Th-Pb isotopic systematics of three meteoritic zircon assemblages, two from the Vaca Muerta mesosiderite and one from the Simmern H5 chondrite, are presented. Like terrestrial zircons, the meteoritic zircons are enriched in the heavy rare-earth elements, but unlike terrestrial zircons, they do not show a positive Ce anomaly. This feature is also absent in one lunar zircon analyzed and probably reflects the oxidation state of the formation environment: under oxidizing conditions Ce(4+) is stabilized, whereas under relatively reducing conditions Ce(3+) is stable. The zircon from Simmern has depletions in the relative abundances of Tm and Yb, a characteristic of the volatility fractionation of the REE. The Simmern zircon has an exceptionally low U concentration (around 180 ppb), and only a poorly constrained Pb-207/Pb-206 age of 4100 +/- 700 Ma could be obtained.

Ireland, T. R.; Wlotzka, F.

1992-03-01

196

A late Jurassic pterosaur (Reptilia, Pterodactyloidea) from northwestern Patagonia, Argentina  

NASA Astrophysics Data System (ADS)

A small to medium-sized pterodactyloid pterosaur (wingspan approximately 1.10 m) from the Upper Jurassic (middle-late Tithonian) marine deposits of the Vaca Muerta Formation of Patagonia (Los Catutos area, central Neuquén Province, Argentina) is reported. The specimen lacks the skull but constitutes a nearly complete postcranial skeleton, which includes cervical and dorsal vertebrae; a few thoracic ribs; both pectoral girdles; the left pelvic girdle; a proximal right wing (humerus, ulna, and radius) and metacarpal IV; a left wing that lacks only wing phalanx four; and both hindlimbs, the right one without the foot. Ontogenetic features suggest that the new fossil corresponds to a relatively mature individual, probably a subadult. Observed characters support its assignment to the Archaeopteroactyloidea, a basal clade within the Pterodactyloidea. This specimen is the second pterosaur from Los Catutos and the most complete Jurassic pterosaur so far known from South America.

Codorniú, Laura; Gasparini, Zulma; Paulina-Carabajal, Ariana

2006-03-01

197

Helicobacter pylori infection in Japan  

PubMed Central

The prevalence of Helicobacter pylori infection is gradually decreasing in Japan. On the main island of Japan, nearly all H. pylori isolates possess cagA and vacA with strong virulence. However, less virulent H. pylori strains are frequently found in Okinawa where cases of gastric cancer are the lowest in Japan. Eradication therapy for peptic ulcer, idiopathic thrombocytopenic purpura, gastric mucosa-associated lymphoid tissue lymphoma and early gastric cancer after endoscopic resection has been approved by the Japanese national health insurance system. However, the Japanese Society for Helicobacter Research recently stated that all ‘H. pylori infection’ was considered as the indication for eradication irrespective of the background diseases. To eliminate H. pylori in Japan, the Japanese health insurance system should approve the eradication of all H. pylori infections.

Shiota, Seiji; Murakawi, Kazunari; Suzuki, Rumiko; Fujioka, Toshio; Yamaoka, Yoshio

2013-01-01

198

Helicobacter pylori infection in Japan.  

PubMed

The prevalence of Helicobacter pylori infection is gradually decreasing in Japan. On the main island of Japan, nearly all H. pylori isolates possess cagA and vacA with strong virulence. However, less virulent H. pylori strains are frequently found in Okinawa where cases of gastric cancer are the lowest in Japan. Eradication therapy for peptic ulcer, idiopathic thrombocytopenic purpura, gastric mucosa-associated lymphoid tissue lymphoma and early gastric cancer after endoscopic resection has been approved by the Japanese national health insurance system. However, the Japanese Society for Helicobacter Research recently stated that all 'H. pylori infection' was considered as the indication for eradication irrespective of the background diseases. To eliminate H. pylori in Japan, the Japanese health insurance system should approve the eradication of all H. pylori infections. PMID:23265147

Shiota, Seiji; Murakawi, Kazunari; Suzuki, Rumiko; Fujioka, Toshio; Yamaoka, Yoshio

2013-01-01

199

Olivines and olivine coronas in mesosiderites  

NASA Technical Reports Server (NTRS)

The paper presents a study of olivines and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. Olivine composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; olivine occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified olivine orthopyroxenites. Fine-grained coronas surround olivine, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.

Nehru, C. E.; Zucker, S. M.; Harlow, G. E.; Prinz, M.

1980-01-01

200

Olivines and olivine coronas in mesosiderites  

NASA Astrophysics Data System (ADS)

The paper presents a study of olivines and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. Olivine composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; olivine occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified olivine orthopyroxenites. Fine-grained coronas surround olivine, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.

Nehru, C. E.; Zucker, S.; Harlow, G. E.; Prinz, M.

1980-08-01

201

Loma La Lata giant gas field from a petroleum paleosystem, Neuquen Basin, Argentina  

SciTech Connect

The elements of a fully developed petroleum system may undergo later modifications, transforming it to a new system. We define the original system as a Petroleum Paleosystem. In the evolution of the Loma La Lata gas field, diagenetic processes have played a major role in the entrapment since reservoir, lateral and top seals consist of eolian sandstones. The gas origin can be explained as an early oil accumulation trapped between the Late Jurassic to Early Tertiary (petroleum paleosystem) that since Late Tertiary underwent a weak but sufficient thermal degradation to provoke the oil cracking resulting in the co-generation of wet gas+condensate+pyrobitumen-like residue. The elements of the paleosystem are: the Kimmeridgian eolian sandstones of the Sierras Blancas Formation+Catriel Formation as reservoir; the source rock and vertical seat is the rich organic matter marine shales associated with the 139 Ma MFS of the Vaca Muerta Formation; the lateral seal is the eolian facies of the Sierras Blancas Formation that experienced very early diagenesis under the strong influence of the phreatic oscillations in areas of maximum subsidence (Sauzal Bonito); the structural trap is related to the Cenomanian tectonic inversion phase; the expulsion peak was reached in the Late Eocene (40 Ma) and the migration from Vaca Muerta Formation. In the last 5 Ma the paleosystem was transformed by processes related to temperature increase. Subsequent calcite precipitation is extensive and resulted in the transformation of eolianites of the Catriel Formation in the vertical seal and coeval down dip remigration from the top of the structure. The intra-reservoir oil cracking has occurred as a consequence of an increment in the subsidence rate accompanied by an abnormally high geothermal gradient in the area.

Guillermo, A.J.; Guillermo, A.L. [YPF, S.A., Avenue Roque Saenz Pena, Buenos Aires (Argentina)

1996-08-01

202

The Costa Rican Central Valley Lavina Formation: Lahar or Debris Avalanche?  

NASA Astrophysics Data System (ADS)

The Lavina Formation of the Central Valley of Costa Rica consists of lava blocks floating in a volcanic mud matrix. Different authors have interpreted this deposit genetically as a lahar or debris flow deposit. Based on geomorphologic, textural, and morphometric evidence, we conclude that the origin of this deposit is a debris avalanche event that transformed into a debris flow on its path down the valley. Using aerial photographs, many debris avalanche amphitheaters are found in the western sector of the Irazu volcanic complex. However, textural and morphometric characteristics of the deposit are consistent with the source of the sector collapse being located on the west flank of the Cabeza de Vaca volcano. Three-dimensional modeling of the Lavina Formation was done using data from 213 drill cores distributed along the Central Valley area. Maps of isopaches and isohipses of the roof and floor of this stratum were created. These allowed for qualification of morphometry of the stratigraphic surfaces, characterization of the paleoslopes, and quantification of the compacted deposit volume. The data derived form the isopach and isohipse contour maps indicate that abrupt changes in the thickness of the stratum are common. Also, it illustrates the morphological differences between the roof, elongated hills in the direction of the flux, and the floor of the stratum, smooth and uniform. The morphometric, geomorphologic, and textural evidence, were used to conclude that the Lavina deposit originated as a debris avalanche event in the Cabeza de Vaca Volcano. The debris avalanche was eventually fluidized into a debris flow that spread extensively (130 km2) along the Central Valley of Costa Rica.

Hidalgo, P. J.; Alvarado Induni, G. E.; Linkimer, L.

2005-12-01

203

Comparative analysis of the full genome of Helicobacter pylori isolate Sahul64 identifies genes of high divergence.  

PubMed

Isolates of Helicobacter pylori can be classified phylogeographically. High genetic diversity and rapid microevolution are a hallmark of H. pylori genomes, a phenomenon that is proposed to play a functional role in persistence and colonization of diverse human populations. To provide further genomic evidence in the lineage of H. pylori and to further characterize diverse strains of this pathogen in different human populations, we report the finished genome sequence of Sahul64, an H. pylori strain isolated from an indigenous Australian. Our analysis identified genes that were highly divergent compared to the 38 publically available genomes, which include genes involved in the biosynthesis and modification of lipopolysaccharide, putative prophage genes, restriction modification components, and hypothetical genes. Furthermore, the virulence-associated vacA locus is a pseudogene and the cag pathogenicity island (cagPAI) is not present. However, the genome does contain a gene cluster associated with pathogenicity, including dupA. Our analysis found that with the addition of Sahul64 to the 38 genomes, the core genome content of H. pylori is reduced by approximately 14% (?170 genes) and the pan-genome has expanded from 2,070 to 2,238 genes. We have identified three putative horizontally acquired regions, including one that is likely to have been acquired from the closely related Helicobacter cetorum prior to speciation. Our results suggest that Sahul64, with the absence of cagPAI, highly divergent cell envelope proteins, and a predicted nontransportable VacA protein, could be more highly adapted to ancient indigenous Australian people but with lower virulence potential compared to other sequenced and cagPAI-positive H. pylori strains. PMID:24375107

Lu, Wei; Wise, Michael J; Tay, Chin Yen; Windsor, Helen M; Marshall, Barry J; Peacock, Christopher; Perkins, Tim

2014-03-01

204

Virulence of infecting Helicobacter pylori strains and intensity of mononuclear cell infiltration are associated with levels of DNA hypermethylation in gastric mucosae.  

PubMed

DNA methylation changes are known to occur in gastric cancers and in premalignant lesions of the gastric mucosae. In order to examine variables associated with methylation levels, we quantitatively evaluated DNA methylation in tumors, non-tumor gastric mucosae, and in gastric biopsies at promoters of 5 genes with methylation alterations that discriminate gastric cancers from non-tumor epithelia (EN1, PCDH10, RSPO2, ZIC1, and ZNF610). Among Colombian subjects at high and low risk for gastric cancer, biopsies from subjects from the high-risk region had significantly higher levels of methylation at these 5 genes than samples from subjects in the low risk region (p ? 0.003). When results were stratified by Helicobacter pylori infection status, infection with a cagA positive, vacA s1m1 strain was significantly associated with highest methylation levels, compared with other strains (p = 0.024 to 0.001). More severe gastric inflammation and more advanced precancerous lesions were also associated with higher levels of DNA methylation (p ? 0.001). In a multivariate model, location of residence of the subject and the presence of cagA and vacA s1m1 in the H. pylori strain were independent variables associated with higher methylation in all 5 genes. High levels of mononuclear cell infiltration were significantly related to methylation in PCDH10, RSPO2, and ZIC1 genes. These results indicate that for these genes, levels of methylation in precancerous lesions are related to H. pylori virulence, geographic region and measures of chronic inflammation. These genes seem predisposed to sustain significant quantitative changes in DNA methylation at early stages of the gastric precancerous process. PMID:24128875

Schneider, Barbara G; Piazuelo, M Blanca; Sicinschi, Liviu A; Mera, Robertino; Peng, Dun-Fa; Roa, Juan Carlos; Romero-Gallo, Judith; Delgado, Alberto G; de Sablet, Thibaut; Bravo, Luis E; Wilson, Keith T; El-Rifai, Wael; Peek, Richard M; Correa, Pelayo

2013-11-01

205

Helicobacter Pylori Promotes the Expression of Kr?ppel-Like Factor 5, a Mediator of Carcinogenesis, In Vitro and In Vivo  

PubMed Central

Helicobacter pylori is the strongest known risk factor for the development of gastric adenocarcinoma. H. pylori expresses a repertoire of virulence factors that increase gastric cancer risk, including the cag pathogenicity island and the vacuolating cytotoxin (VacA). One host element that promotes carcinogenesis within the gastrointestinal tract is Krüppel-like factor 5 (KLF5), a transcription factor that mediates key cellular functions. To define the role of KLF5 within the context of H. pylori-induced inflammation and injury, human gastric epithelial cells were co-cultured with the wild-type cag+ H. pylori strain 60190. KLF5 expression was significantly upregulated following co-culture with H. pylori, but increased expression was independent of the cag island or VacA. To translate these findings into an in vivo model, C57BL/6 mice were challenged with the wild-type rodent-adapted cag+ H. pylori strain PMSS1 or a PMSS1 cagE? isogenic mutant. Similar to findings in vitro, KLF5 staining was significantly enhanced in gastric epithelium of H. pylori-infected compared to uninfected mice and this was independent of the cag island. Flow cytometry revealed that the majority of KLF5+ cells also stained positively for the stem cell marker, Lrig1, and KLF5+/Lrig1+ cells were significantly increased in H. pylori-infected versus uninfected tissue. To extend these results into the natural niche of this pathogen, levels of KLF5 expression were assessed in human gastric biopsies isolated from patients with or without premalignant lesions. Levels of KLF5 expression increased in parallel with advancing stages of neoplastic progression, being significantly elevated in gastritis, intestinal metaplasia, and dysplasia compared to normal gastric tissue. These results indicate that H. pylori induces expression of KLF5 in gastric epithelial cells in vitro and in vivo, and that the degree of KLF5 expression parallels the severity of premalignant lesions in human gastric carcinogenesis.

Noto, Jennifer M.; Khizanishvili, Tinatin; Chaturvedi, Rupesh; Piazuelo, M. Blanca; Romero-Gallo, Judith; Delgado, Alberto G.; Khurana, Shradha S.; Sierra, Johanna C.; Krishna, Uma S.; Suarez, Giovanni; Powell, Anne E.; Goldenring, James R.; Coffey, Robert J.; Yang, Vincent W.; Correa, Pelayo; Mills, Jason C.; Wilson, Keith T.; Peek, Richard M.

2013-01-01

206

Effects of Helicobacter pylori on intracellular Ca2+ signaling in normal human gastric mucous epithelial cells.  

PubMed

In stomach, Helicobacter pylori (Hp) adheres to gastric mucous epithelial cells (GMEC) and initiates several different signal transduction events. Alteration of intracellular Ca2+ concentration ([Ca2+]i) is an important signaling mechanism in numerous bacteria-host model systems. Changes in [Ca2+]i induced by Hp in normal human GMEC have not yet been described; therefore, we examined effects of Hp on [Ca2+]i in normal human GMEC and a nontransformed GMEC line (HFE-145). Cultured cells were grown on glass slides, porous filters, or 96-well plates and loaded with fura 2 or fluo 4. Hp wild-type strain 60190 and vacA-, cagA-, and picB-/cagE- isogenic mutants were incubated with cells. Changes in [Ca2+]i were recorded with a fluorimeter or fluorescence plate reader. Wild-type Hp produced dose-dependent biphasic transient [Ca2+]i peak and plateau changes in both cell lines. Hp vacA- isogenic mutant produced changes in [Ca2+]i similar to those produced by wild type. Compared with wild type, cagA- and picB-/cagE- isogenic mutants produced lower peak changes and did not generate a plateau change. Preloading cultures with intracellular Ca2+ chelator BAPTA blocked all Hp-induced [Ca2+]i changes. Thapsigargin pretreatment of cultures to release Ca2+ from internal stores reduced peak change. Extracellular Ca2+ removal reduced plateau response. Hp-induced peak response was sensitive to G proteins and PLC inhibitors. Hp-induced plateau change was sensitive to G protein inhibitors, src kinases, and PLA2. These findings are the first to show that H. pylori alters [Ca2+]i in normal GMEC through a Ca2+ release/influx mechanism that depends on expression of cagA and picB/cagE genes. PMID:12606301

Marlink, Katie L; Bacon, Kathy D; Sheppard, Brett C; Ashktorab, Hassan; Smoot, Duane T; Cover, Timothy L; Deveney, Clifford W; Rutten, Michael J

2003-07-01

207

Helicobacter pylori induces apoptosis in Barrett's-derived esophageal adenocarcinoma cells.  

PubMed

Helicobacter pylori may protect against the development of dysplasia in Barrett's epithelium of patients with gastroesophageal reflux disease. The aim of this study was to determine whether H. pylori preferentially induces apoptosis in Barrett's-derived cancer cells compared to normal cells. A Barrett's-derived adenocarcinoma cell line (OE33) was grown. H. pylori wild-type, isogenic vacA-, cagA(-), and picB-/cagE- mutant strains were grown on agar plates. Intact or sonicated bacteria were used to treat normal and OE33 cells for 24 hours, and Hoechst dye binding was performed to measure apoptosis. FAS protein expression was determined by Western immunoblotting. OE33 cells treated with intact H. pylori wild-type strains produced significant (P < 0.05) dose-dependent increases in apoptosis compared to normal esophageal cells. H. pylori wild-type and vacA- isogenic strains were more effective than cagA- and picB-/cage- isogenic strains in inducing apoptosis in OE33 cells. In OE33 cells, H. pylori sonicates produced lower levels of apoptosis than intact bacteria. Wild-type H. pylori strains increased Fas protein expression in OE33 cells at 18 hours. H. pylori induced apoptosis at a higher rate in the Barrett's-derived human esophageal adenocarcinoma cells than in normal esophageal cells. The H. pylori-induced apoptosis was primarily dependent on intact bacteria and the presence of the cagA and picB/cagE gene products. H. pylori-induced apoptosis may involve the Fas-caspase cascade. PMID:12559187

Jones, Andrew D; Bacon, Kathy D; Jobe, Blair A; Sheppard, Brett C; Deveney, Clifford W; Rutten, Michael J

2003-01-01

208

A pilot study of Helicobacter pylori genotypes and cytokine gene polymorphisms in reflux oesophagitis and peptic ulcer disease.  

PubMed

Helicobacter pylori causes various diseases such as chronic gastritis, peptic ulcer and gastric cancer. While majority of the people infected with H. pylori is asymptomatic, 15-20 % of them develop such diseases. The main factors, which determine the development of H. pylori related diseases might be bacterial virulence, host genetic and environmental factors.The aim of this study was to reveal the factors that play a role in the disease development in patients with reflux esophagitis and peptic ulcer, infected with Helicobacter pylori. Environmental factors such as medical agents, smoking and body mass index were evaluated. The factors specific to bacteria such as vacA, CagA, babA and iceA virulence genotypes and the host factors such as IL-1, IL-2, IL-4, IL-6, IL-10, IL-12, interferon-?, TNF-?, ve TGF-?1 gene polymorphisms were compared between the two groups.H. pylori infected twenty five patients with reflux esophagitis and peptic ulcer were enrolled in the study. There was no statistical difference between the two groups regarding environmental factors. IL-2 -330T +166T (p=0.037) and IL10 -1082A; -819C (p=0.049) gene polymorphisms were significantly more common in the group of patients with peptic ulcer compared to the group with reflux esophagitis. In both groups of patients, either with reflux esophagitis or peptic ulcer, multiple H. pylori virulence genotypes (cagA, vacA, babA) (mean values 74?%, 78 %, 54 % respectively) were observed.In this study, we revealed that cytokine gene polymorphisms may play a role in the development peptic ulcer while H. pylori virulence genotypes seem to be crucial for the development of associated diseases (Tab. 4, Ref.?51). PMID:24797597

Akdogan, R A; Ozgur, O; Gucuyeter, S; Kaklikkaya, N; Cobanoglu, U; Aydin, F

2014-01-01

209

Helicobacter pylori infection and gastroduodenal diseases in Vietnam: a cross-sectional, hospital-based study  

PubMed Central

Background The rate of H. pylori infection in Vietnam is reportedly high, but the spectrum of H. pylori-associated gastroduodenal diseases has not been systematically investigated. Moreover, despite the similarities of ethnicity and diet, the age-standardized incidence rate of gastric cancer in the northern city of Hanoi is higher than that in the southern city of Ho Chi Minh, but the reason for this phenomenon is unknown. The virulence of Vietnamese H. pylori has also not been investigated in detail. Methods Individuals undergoing esophagogastroduodenoscopy were randomly recruited. H. pylori infection status was determined based on the combined results of culture, histology, immunohistochemistry, rapid urine test and serum ELISA. Peptic ulcer (PU) and gastroesophageal reflux disease was diagnosed by endoscopy, and chronic gastritis was determined histologically. H. pylori virulence factors were investigated by PCR and sequencing. Results Among the examined patients, 65.6% were infected with H. pylori. The prevalence of infection was significantly higher in those over 40 years of age than in those aged ?40. Chronic gastritis was present in all H. pylori-infected individuals, 83.1% of whom had active gastritis, and 85.3% and 14.7% had atrophy and intestinal metaplasia, respectively. PU was present in 21% of infected patients, whereas its incidence was very low in non-infected individuals. The prevalence of PU was significantly higher in Hanoi than in Ho Chi Minh. The prevalence of vacA m1, which has been identified as an independent risk factor for PU in Vietnam, was significantly higher among H. pylori isolates from Hanoi than among those from Ho Chi Minh. Conclusions H. pylori infection is common in Vietnam and is strongly associated with PU, active gastritis, atrophy and intestinal metaplasia. vacA m1 is associated with an increased risk for PU and might contribute to the difference in the prevalence of PU and gastric cancer between Hanoi and Ho Chi Minh.

2010-01-01

210

Helicobacter pylori: Clonal Population Structure and Restricted Transmission within Families Revealed by Molecular Typing  

PubMed Central

Helicobacter pylori infects up to 50% of the human population worldwide. The infection occurs predominantly in childhood and persists for decades or a lifetime. H. pylori is believed to be transmitted from person to person. However, tremendous genetic diversity has been reported for these bacteria. In order to gain insight into the epidemiological basis of this phenomenon, we performed molecular typing of H. pylori isolates from different families. Fifty-nine H. pylori isolates from 27 members of nine families were characterized by using restriction fragment length polymorphism analysis of five PCR-amplified genes, by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA, and by vacA and cagA genotyping. The 16S rRNA gene exhibited little allelic variation, as expected for a unique bacterial species. In contrast, the vacA, flaA, ureAB, and lspA-glmM genes were highly polymorphic, with a mean genetic diversity of 0.83, which exceeds the levels recorded for all other bacterial species. In conjunction with PFGE, 59 H. pylori isolates could be differentiated into 21 clonal types. Each individual harbored only one clone, occasionally with a clonal variant. Identical strains were always found either between siblings or between a mother and her children. Statistical analysis revealed clonality of population structure in all isolates. The results of this study suggest the possible coexistence of a large array of clonal lineages that are evolving in each individual in isolation from one another. Transmission appears to occur primarily from mother to child and perhaps between siblings.

Han, Shan-Rui; Zschausch, Hans-Christoph E.; Meyer, Heinz-Georg W.; Schneider, Thomas; Loos, Michael; Bhakdi, Sucharit; Maeurer, Markus J.

2000-01-01

211

Fotometría superficial de la galaxia irregular NGC 1427A  

NASA Astrophysics Data System (ADS)

Se presenta fotometría superficial multicolor de la galaxia irregular NGC 1427A. Esta galaxia, un miembro del Cúmulo de Fornax que no ha sido estudiado previamente, muestra una morfología muy particular: una distribución estelar subyacente de bajo brillo superficial (LSB) con varias manchas brillantes dispuestas en una estructura anular deformada. Por sus colores muy azules se infiere que estas son zonas de formación estelar reciente. Al norte del cuerpo principal de la galaxia, y conectado con éste mediante filamentos LSB, hay un objeto de isofotas aproximadamente circulares. Este objeto tiene en sí mismo algunas zonas brillantes, pero su población estelar subyacente es significativamente más azul que la del cuerpo principal de la galaxia. Esto indica que ambos objetos han tenido distintas historias evolutivas. Estructuralmente, el objeto del norte es muy similar a algunas de las galaxias elípticas enanas más débiles que pueblan el Cúmulo de Fornax. Se discute la posible relación entre este objeto y la galaxia en si.

Cellone, S. A.; Forte, J. C.

212

Screening Helicobacter pylori genes induced during infection of mouse stomachs  

PubMed Central

AIM: To investigate the effect of in vivo environment on gene expression in Helicobacter pylori (H. pylori) as it relates to its survival in the host. METHODS: In vivo expression technology (IVET) systems are used to identify microbial virulence genes. We modified the IVET-transcriptional fusion vector, pIVET8, which uses antibiotic resistance as the basis for selection of candidate genes in host tissues to develop two unique IVET-promoter-screening vectors, pIVET11 and pIVET12. Our novel IVET systems were developed by the fusion of random Sau3A DNA fragments of H. pylori and a tandem-reporter system of chloramphenicol acetyltransferase and beta-galactosidase. Additionally, each vector contains a kanamycin resistance gene. We used a mouse macrophage cell line, RAW 264.7 and mice, as selective media to identify specific genes that H. pylori expresses in vivo. Gene expression studies were conducted by infecting RAW 264.7 cells with H. pylori. This was followed by real time polymerase chain reaction (PCR) analysis to determine the relative expression levels of in vivo induced genes. RESULTS: In this study, we have identified 31 in vivo induced (ivi) genes in the initial screens. These 31 genes belong to several functional gene families, including several well-known virulence factors that are expressed by the bacterium in infected mouse stomachs. Virulence factors, vacA and cagA, were found in this screen and are known to play important roles in H. pylori infection, colonization and pathogenesis. Their detection validates the efficacy of these screening systems. Some of the identified ivi genes have already been implicated to play an important role in the pathogenesis of H. pylori and other bacterial pathogens such as Escherichia coli and Vibrio cholerae. Transcription profiles of all ivi genes were confirmed by real time PCR analysis of H. pylori RNA isolated from H. pylori infected RAW 264.7 macrophages. We compared the expression profile of H. pylori and RAW 264.7 coculture with that of H. pylori only. Some genes such as cagA, vacA, lpxC, murI, tlpC, trxB, sodB, tnpB, pgi, rbfA and infB showed a 2-20 fold upregulation. Statistically significant upregulation was obtained for all the above mentioned genes (P < 0.05). tlpC, cagA, vacA, sodB, rbfA, infB, tnpB, lpxC and murI were also significantly upregulated (P < 0.01). These data suggest a strong correlation between results obtained in vitro in the macrophage cell line and in the intact animal. CONCLUSION: The positive identification of these genes demonstrates that our IVET systems are powerful tools for studying H. pylori gene expression in the host environment.

Singh, Aparna; Hodgson, Nathaniel; Yan, Ming; Joo, Jungsoo; Gu, Lei; Sang, Hong; Gregory-Bryson, Emmalena; Wood, William G; Ni, Yisheng; Smith, Kimberly; Jackson, Sharon H; Coleman, William G

2012-01-01

213

Proteins Released by Helicobacter pylori In Vitro  

PubMed Central

Secretion of proteins by Helicobacter pylori may contribute to gastric inflammation and epithelial damage. An in vitro analysis was designed to identify proteins released by mechanisms other than nonspecific lysis. The radioactivity of proteins in the supernatant was compared with that of the intact organism by two-dimensional gel phosphorimaging following a 4-h pulse-chase. The ratio of the amount of UreB, a known cytoplasmic protein, in the supernatant to that in the pellet was found to be 0.25, and this was taken as an index of lysis during the experiments (n = 6). Ratios greater than that of UreB were used to distinguish proteins that were selectively released into the medium. Thus, proteins enriched more than 10-fold in the supernatant compared to UreB were identified by mass spectrometry. Sixteen such proteins were present in the supernatant: VacA; a conserved secreted protein (HP1286); putative peptidyl cis-trans isomerase (HP0175); six proteins encoded by HP0305, HP0231, HP0973, HP0721, HP0129, and HP0902; thioredoxin (HP1458); single-stranded-DNA-binding 12RNP2 precursor (HP0827); histone-like DNA-binding protein HU (HP0835); ribosomal protein L11 (HP1202); a putative outer membrane protein (HP1564); and outer membrane proteins Omp21 (HP0913) and Omp20 (HP0912). All except HP0902, thioredoxin, HP0827, HP0835, and HP1202 had a signal peptide. When nalidixic acid, a DNA synthesis inhibitor, was added to inhibit cell division but not protein synthesis, to decrease possible contamination due to outer membrane shedding, two outer membrane proteins (Omp21 and Omp20) disappeared from the supernatant, and the amount of VacA also decreased. Thus, 13 proteins were still enriched greater than 10-fold in the medium after nalidixic acid treatment, suggesting these were released specifically, possibly by secretion. These proteins may be implicated in H. pylori-induced effects on the gastric epithelium.

Kim, Nayoung; Weeks, David L.; Shin, Jai Moo; Scott, David R.; Young, Mary K.; Sachs, George

2002-01-01

214

Mesozoic inversion in southeastern parts of the Neuquén Basin, west-central Argentina: Implications for tectonic deformation and stratigraphic development across the Andean foreland of Argentina  

NASA Astrophysics Data System (ADS)

The Neuquén Basin of west-central Argentina is a segment of the Andean foreland that has significant structural complexity due to protracted intraforeland deformation between Late Triassic to Recent time. Some structural features in the Neuquén Basin predate the main phases of the Andean orogeny although these structures were reactivated later and influenced basin configuration during the foreland-basin stage. The most conspicuous of these structures is the Huincul Arch, a 200-km-long right-lateral shear zone that was most active during Jurassic to Cretaceous time. Inversion structures along the Huincul Arch are associated with a restraining bend along the main east-west trending shear zone that cuts across the Argentine foreland. An extensive seismic and borehole data set was analyzed to evaluate the styles and intensity of Mesozoic foreland deformation in an approximately 10,000 sq km area north of the Huincul Arch. Transpressional and transtensional deformation is broadly distributed across the study area and other parts of the Neuquén foreland, although a series of inversion structures (e.g., Sierra Barrosa and Aguada Toledo anticlines) reflect more intense, localized deformation. These structures are the result of inversion of Late Triassic half-grabens and produced fault-propagation folds that affected the post-rift fill up to the Upper Jurassic (Tithonian). The most significant reactivation along the Huincul Arch south of our study area occurred during Kimmeridgian (Late Jurassic) time along the main displacement zone. To the north, however, significant inversion was slightly younger and occurred during and after deposition of the Tithonian to Berriasian (latest Jurassic-earliest Cretaceous) Vaca Muerta and Quintuco formations. Thus, early phases of tectonic inversion across the Argentine foreland were diachronous and likely reflect an accumulation of strain along the Huincul Arch was necessary before additional strain could propagate northward into our study area. Seismic-stratigraphic analyses also show that the growing inversion structures created bathymetric perturbations that affected sediment dispersal and stratigraphic development north of the Huincul Arch during deposition of the Vaca Muerta-Quintuco interval. This study contributes to the understanding of Pre-Andean deformation in the Neuquén Basin. 3D seismic data across the study area also provides a unique opportunity to investigate the geometries and kinematic history of inversion across the Andean foreland, as well as to evaluate tectonic controls on Mesozoic stratigraphic development in the poorly understood Northern Sub-basin of the Neuquén Basin.

Grimaldi, G. O.; Dorobek, S. L.

2004-12-01

215

Taking Geoscience to Public Schools: Attitude and Knowledge Relationships  

NASA Astrophysics Data System (ADS)

The Cabeza de Vaca Earthmobile Program is an ongoing project that is designed to strengthen geoscience education in South Texas public schools. It began in June 2003 and is funded by the National Science Foundation. This outreach program involves collaboration between Texas A&M University-Corpus Christi and four independent school districts in South Texas with support from the South Texas Rural Systemic Initiative, another NSF-funded project. Additional curriculum support has been provided by various local and state organizations. Across Texas, fifth grade students are demonstrating a weakness in geoscience concepts as evidenced by their scores on the Texas Assessment of Knowledge and Skills. As a result, fifth and sixth grade public school students from low-income school districts were selected to participate in this program. At this age students are already making decisions that will affect their high school and college years. The main purpose of this project is to encourage these students, many of whom are Hispanic, to become geoscientists. This purpose is accomplished by enhancing their geoscience knowledge, nurturing their interest in geoscience and showing them what careers are available in the geosciences. Educators and scientists collaborate to engage students in scientific discovery through hands-on laboratory exercises and exposure to state-of-the-art technology (laptop computers, weather stations, telescopes, etc.). Students' family members become involved in the geoscience learning process as they participate in Family Science Night activities. Family Science Nights constitute an effective venue to reach the public. During the course of the Cabeza de Vaca Earthmobile Program, investigators have measured success in two ways: improvement in students' knowledge of geoscience concepts and change in students' attitudes towards geoscience. Findings include significant improvement in students' knowledge of geoscience. Students also report more positive attitudes toward geoscience after having participated in laboratory activities and Family Science Nights. Preliminary findings on the extent to which geoscience and geoscience careers become part of families' purviews, discourses and planning through involvement in Family Science Nights will be presented. Implications related to the success of this program, as indicated by measurement of students' knowledge and attitudes of geoscience as well as engagement of this program by families, will be discussed.

Silliman, J. E.; Hansen, A.; McDonald, J.; Martinez, M.

2005-12-01

216

Reversible cerebral vasoconstriction syndrome and migraine: sonography study.  

PubMed

RCVS is characterized by severe headaches with or without focal neurologic deficits and segmental constriction of cerebral arteries that resolves within 3 months. The primary clinical manifestation is recurrent sudden-onset and thunderclap headache. Diagnosis requires cerebral or magnetic resonance angiography (MRA) confirmation and ultrasound monitoring. Our purpose is to discover the difference of ultrasound data between RCVS and migraine. 61 patients (age range 17-60y., 41-female, 20-male) underwent sonography examination using Transcranial Dopplerography (TCD) and Transcranial Color-Coded Duplex Sonography (TCCD) methods. In 29 patients MRA examinations were performed. Group I- 27 patients with RCVS with typical acute-onset of severe headaches. Group II-34 patients- migraine in anamnesis, with 1-2 attacks monthly, control group -15 healthy persons. Ultrasound examinations were performed during 2 months with time intervals of 1-20, 21-40, and 41-60 days. Markedly in migraine group examinations were performed in interictal periods also. Group I-the mean maximum (MM) V(CS)-77,8 ± 14,7 cm/sec, V(MCA)- 127,5 ± 22.8 cm/sec, V(ACA) -115.7 ± 18.4, V(BA)- 74.7 ± 20.1. Lindegaard Index (LI) -3.1 ± 0.5. MRA revealed segmental cerebral artery vasoconstriction. The MCA was involved in 62.9%, the ACA- in 51.8%, the PCA- in 37% and the BAS- in 40.7% of patients. Group II- the MM V (CS)-72.8 ± 12.5 cm/sec, V (MCA)- 118,4 ± 26.7 cm/sec, V(ACA) -105.8 ± 17.6, V(BA)- 74.5 ± 18.1, averaged LI -2,9 ± 0.7. In the majority (61.7%) of this group revealed increased MM V in several cerebral arteries with different combination of involving vessels. No correlation was found between incidence side of pain and /or pain intensity. Both groups exceeded of controls -V (MCA) (63.2 ± 9.5 cm/sec), LI (2.1 ± 0.2), p<0.001) and revealed vasospasm. All data were calculated by nonparametric Binomial test. Obtained data showed no significant difference regarding the vasospasm degree between typical RCVS and migraine, whereas revealed that vasospasm in migraine is more determined to posterior circulation but in RCVS vasospasm has the more diffuse character. Despite the extensive knowledge concerning RCVS and migraine, many uncertainties still exist and further randomized controlled trials are needed for understanding the underlying pathophysiology factors. PMID:24743119

Alpaidze, M; Beridze, M

2014-03-01

217

Helicobacter pylori antibody patterns in Germany: a cross-sectional population study  

PubMed Central

Background Helicobacter pylori infection that is usually acquired in childhood and lasts for lifetime is mostly asymptomatic but associated with severe gastrointestinal disease including cancer. During chronic infection, the gastric mucosa is histologically changing. This forces H. pylori to permanent adaptation in its gastric habitat by expression of different proteins which might be reflected in distinctive antibody patterns. Methods To characterize dynamics of the immune response to H. pylori we analysed 1797 sera of a cross-sectional study representative for the German population (age range 1–82 years) with multiplex serology, a fluorescent bead-based antibody binding assay that allows simultaneous and quantitative detection of antibodies. Fifteen recombinant, affinity-purified H. pylori proteins (UreA, GroEL, Catalase, NapA, CagA, CagM, Cag?, HP0231, VacA, HpaA, Cad, HyuA, Omp, HcpC and HP0305) were used as antigens. Results H. pylori seroprevalence (positivity for at least three antigens) was 48% and increased with age from 12% in children <15 years to 69% in females and 90% in males >65 years. Prevalences were highest (>83%) for Omp, VacA and GroEL. For 11 proteins, seroprevalence was higher in males than females (P?65 years stronger in females (P?=?0.02). Antibody reactivities to GroEL, HyuA, CagM, Catalase, NapA and UreA also increased stronger in females (average 1.7-fold/decade, SD 0.5) than in males (1.5-fold/decade, SD 0.4). Conclusion H. pylori antibody response accumulates qualitatively and quantitatively with age. This may reflect a lifelong stimulation of the immune response by chronically active infection.

2014-01-01

218

Multiple Infection and Microdiversity among Helicobacter pylori Isolates in a Single Host in India  

PubMed Central

Helicobacter pylori is one of the most diverse bacterial species that chronically infects more than 70% of Indian population. Interestingly, data showing microdiversity of the H. pylori strains within a particular gastric niche remained scarce. To understand the extent of genetic diversity among H. pylori strains within a given host, 30 patients with gastro-duodenal problems were subjected to endoscopy and from each patient 10 single colonies were isolated. Characterization of each of these 10 single colonies by DNA fingerprinting as well as genotyping of several important genetic markers viz. cagA, vacA, iceA, vapD, cag PAI empty site, IS605, RFLP and two other genetic segments within cag PAI revealed that all of the 30 patients were infected with more than one strain and sometimes strains with 5 to 6 types of genetic variants. Analyses of certain genetic loci showed the microdiversity among the colonies from single patient, which may be due to the recombination events during long-term carriage of the pathogen. These results suggest that most of the patients have acquired H. pylori due to repeated exposure to this pathogen with different genetic make-up, which may increase the possibility of super infections. Genetic exchanges between these unrelated H. pylori strains may support certain H. pylori variant to grow better in a given host than the parental strain and thereby increasing the possibility for the severity of the infection.

Patra, Rajashree; Chattopadhyay, Santanu; De, Ronita; Ghosh, Prachetash; Ganguly, Mou; Chowdhury, Abhijit; Ramamurthy, T.; Nair, G. B.; Mukhopadhyay, Asish K.

2012-01-01

219

Pathogenesis of Helicobacter pylori-Related Gastroduodenal Diseases from Molecular Epidemiological Studies  

PubMed Central

Helicobacter pylori is a major human pathogen that infects the stomach and produces inflammation that is responsible for various gastroduodenal diseases. Despite the high prevalence of H. pylori infections in Africa and South Asia, the incidence of gastric cancer in these areas is much lower than in other countries. The incidence of gastric cancer also tends to decrease from north to south in East Asia. Data from molecular epidemiological studies show that this variation in different geographic areas could be explained in part by different types of H. pylori virulence factors, especially CagA, VacA, and OipA. H. pylori infection is thought to be involved in both gastric cancer and duodenal ulcer, which are at opposite ends of the disease spectrum. This discrepancy can also be explained in part by another H. pylori factor, DupA, as well as by CagA typing (East Asian type versus Western type). H. pylori has a genome of approximately 1,600 genes; therefore, there might be other novel virulence factors. Because genome wide analyses using whole-genome sequencing technology give a broad view of the genome of H. pylori, we hope that next-generation sequencers will enable us to efficiently investigate novel virulence factors.

Yamaoka, Yoshio

2012-01-01

220

Comparative analysis of transcription profiles of Helicobacter pylori clinical isolates.  

PubMed

The transcription profiles of four Helicobacter pylori clinical isolates (two cag-negative and two cag-positive) were compared in stationary growth phase using a cDNA-macroarray. The correlation coefficient value between total transcription profiles of clinical isolates H. pylori varied from 0.70 to 0.83. For 44 groups of genes (total number 66) belonging to various functional classes of H. pylori, the correlation coefficient value between these isolates exceeded 0.7, and for 14 groups the value exceeded 0.9. These groups included genes encoding components involved in cell division, adaptations to atypical conditions, electron transport, salvage of nucleosides and nucleotides, glycolysis/gluconeogenesis, folding and stabilization of proteins, translation factors, anaerobic metabolism, and amino acids and amine metabolism. Expression of 52 genes significantly differed between H. pylori clinical isolates. Some of these genes determine microorganism virulence. They include: cytotoxin-associated gene (cagA), genes encoding neutrophil-activating protein (napA), major flagellar protein (flaA), and vacuolizing cytotoxin (vacA), some genes encoding outer membrane proteins (omp), urease alpha and beta subunits (ureA and ureB), and some regulatory proteins, and genes encoding stress-related proteins, such as the chaperone and heat shock protein genes (groEL and dnaK). PMID:15892605

Momynaliev, K T; Rogov, S I; Selezneva, O V; Chelysheva, V V; Akopian, T A; Govorun, V M

2005-04-01

221

Signal transduction of Helicobacter pylori during interaction with host cell protein receptors of epithelial and immune cells.  

PubMed

Helicobacter pylori infections can induce pathologies ranging from chronic gastritis, peptic ulceration to gastric cancer. Bacterial isolates harbor numerous well-known adhesins, vacuolating cytotoxin VacA, protease HtrA, urease, peptidoglycan, and type IV secretion systems (T4SS). It appears that H. pylori targets more than 40 known host protein receptors on epithelial or immune cells. A series of T4SS components such as CagL, CagI, CagY, and CagA can bind to the integrin ? 5? 1 receptor. Other targeted membrane-based receptors include the integrins ?v? 3, ?v? 5, and ? 2 (CD18), RPTP-?/?, GP130, E-cadherin, fibronectin, laminin, CD46, CD74, ICAM1/LFA1, T-cell receptor, Toll-like receptors, and receptor tyrosine kinases EGFR, ErbB2, ErbB3, and c-Met. In addition, H. pylori is able to activate the intracellular receptors NOD1, NOD2, and NLRP3 with important roles in innate immunity. Here we review the interplay of various bacterial factors with host protein receptors. The contribution of these interactions to signal transduction and pathogenesis is discussed. PMID:24280762

Pachathundikandi, Suneesh Kumar; Tegtmeyer, Nicole; Backert, Steffen

2013-01-01

222

NMR-based Molecular Rheology of Entangled Polymers in Bulk and in Nanoscopic Confinement  

NASA Astrophysics Data System (ADS)

We demonstrate the use of simple proton low-field NMR to probe the validity of the tube model of polymer dynamics. The method yields a time-domain measure of the segmental orientation autocorrelation function C(t), which in turn is directly related to the stress relaxation modulus G(t), thus providing a true molecular measure of rheologically relevant quantities. The fixed-tube model does not describe actual data well, and current work focuses on deuteron labeling schemes to investigate the relevance of contour-length fluctuation (CLF) or constraint release (CR) effects. As first results, we found that unexpectedly, CR processes are responsible for modified chain modes faster than actual reptation [1], and also that the dynamics is inhomogeneous along a given chain, stressing also the significance of CLF. We also present recent results for melt dynamics in nanoscopic confinement of long cylindrical channels of 20-400 nm diameter [2]. We consistently observe a fraction of chains whose dynamics is less isotropic on long time scales, i.e., in the Doi-Edwards regimes III (reptation) and IV (disentangled dynamics)[0pt] [1] F. Vaca Ch'avez, K. Saalw"achter, Phys. Rev. Lett. 104, 198305 (2010), [2] S. Ok et al., Macromolecules 43, 4429 (2010)

Saalwachter, Kay; Trutschel, Marie-Luise; Vaca Chavez, Fabian

2012-02-01

223

Helicobacter pylori and gastric cancer.  

PubMed

Infection with Helicobacter pylori is established as the major risk factor for gastric cancer development. Damage of the mucosal barrier due to H. pylori-induced inflammation enhances the carcinogenic effect of other risk factors such as salt intake or tobacco smoking. The genetic disposition of both the bacterial strain and the host can increase the potential towards gastric cancer formation. Genetic variance of the bacterial proteins CagA and VacA is associated with a higher gastric cancer risk, as are polymorphisms and epigenetic changes in host gene coding for interleukins (IL1?, IL8), transcription factors (CDX2, RUNX3) and DNA repair enzymes. Application of high-throughput assays for genome-wide assessment of either genetic structural variance or gene expression patterns may lead to a better understanding of the pathobiological background of these processes, including the underlying signaling pathways. Understanding of the stepwise alterations that take place in the transition from chronic atrophic gastritis, via metaplastic changes, to invasive neoplasia is vital to define the 'point of no return' before which eradication of H. pylori has the potential to prevent gastric cancer. Currently, eradication as preventive strategy is only recommended for high-incidence regions in Asia; large population studies with an adequate follow-up are required to demonstrate the effectiveness of such an approach in Western populations. PMID:24732191

Bornschein, Jan; Malfertheiner, Peter

2014-01-01

224

High CO/sub 2/, high H/sub 2/S removal with selexol solvent  

SciTech Connect

The Selexol Solvent process of Allied Chemical Corp. for treating both sour natural gases and coal- or oil-derived synthesis gases, uses strong solubility differences of various gaseous components in Selexol that acts as physical solvent. This permits a variety of uses in any gas purification service, including bulk removal of CO/sub 2/ alone or combined with water dew point control and recovery of C/sub 5/+ paraffins, as in the Lo-Vaca Gathering Co.'s Grey Ranch gas plant; removal of small amounts of H/sub 2/S (< 1 g/100 cu ft) together with CO/sub 2/, or for higher concentrations, by using a split cycle scheme with H/sub 2/S stripping, as in Northern Natural Gas Co.'s Oates, Tex., plant; the two-stage H/sub 2/S-CO/sub 2/ absorption required in SNG or synthesis gas generation from coal to minimize air pollution by H/sub 2/S, as in Bituminous Coal Research Inc.'s Bi-Gas pilot plant; and bulk removal of H/sub 2/S together with CO/sub 2/, mercaptans, and carbonyl sulfide in a single absorber, as in Norddeutsche Erdgasaufbereitungsges. m.b.H.'s NEAG II plant.

Sweny, J.W.

1980-01-01

225

Dynamics of the Cag-type IV secretion system of Helicobacter pylori as studied by bacterial co-infections.  

PubMed

Many pathogenic Gram-negative bacteria possess type IV secretion systems (T4SS) to inject effector proteins directly into host cells to modulate cellular processes to their benefit. The human bacterial pathogen Helicobacter pylori, a major aetiological agent in the development of chronic gastritis, duodenal ulcer and gastric carcinoma, harbours the cag-T4SS to inject the cytotoxin associated Antigen (CagA) into gastric epithelial cells. This results in deregulation of major signalling cascades, actin-cytoskeletal rearrangements and eventually gastric cancer. We show here that a pre-infection with live H.?pylori has a dose-dependent negative effect on the CagA translocation efficiency of a later infecting strain. This effect of the 'first' strain was independent of any of its T4SS, the vacuolating cytotoxin (VacA) or flagella. Other bacterial pathogens, e.g. pathogenic Escherichia coli, Campylobacter jejuni, Staphylococcus aureus, or commensal bacteria, such as lactobacilli, were unable to interfere with H.?pylori's CagA translocation capacity in the same way. This interference was independent of the ?1 integrin receptor availability for H.?pylori, but certain H.?pylori outer membrane proteins, such as HopI, HopQ or AlpAB, were essential for the effect. We suggest that the specific interference mechanism induced by H.?pylori represents a cellular response to restrict and control CagA translocation into a host cell to control the cellular damage. PMID:23844976

Jiménez-Soto, Luisa F; Clausen, Sabine; Sprenger, Annika; Ertl, Claudia; Haas, Rainer

2013-11-01

226

Emplacement of bitumen (asphalite) veins in the Nequen Basin, Argentina  

SciTech Connect

Veins of solid bitumen (asphaltite) have been commerically exploited in the Neuquen basin, Argentina, for over 100 yr. Veins are up to 5 m wide and several kilometers in length, over a region of 15,000 km{sup 2}. These veins were emplaced in fractures both parallel and at high angles to bedding, in close proximity to their source rocks in the Vaca Muetra and Agrio formation (Late Jurassic-Early Cretaceous). Two or more phases of bitumen emplacement can be recognized in several localities; structures bearing viscous oil are younger than structures having solid bitumen. Bitumen emplacement was vigorous and caused brecciation and spalling of the host rocks. The bitumen was also viscous, and supports rock debris ranging in size from sand grains up to meter-scale slabs. Brecciation, bedding-parallel injection, and wall rock impregnation suggest high fluid pressures during emplacement. High fluid pressure may have been engendered by substantial hydrocarbon generation from rich source rocks in a low-permeability sequence, and probably caused the fractures into which the bitumen migrated. The bedding-parallel veins facilitated decollement during thrusting that took place during and after bitumen emplacement. The timing of emplacement relative to thrusting and oil migration constrains bitumen emplacement to the Eocene-Oligocene.

Parnell, J.; Carey, P.F. [The Queen`s Univ. of Belfast (United Kingdom)

1995-12-01

227

Late Holocene environmental reconstruction using cave sediments from Belize  

NASA Astrophysics Data System (ADS)

Cave sediments collected from Reflection Cave on the Vaca Plateau, Belize show variations in the ?13C values of their fulvic acids (FAs), which indicate periods of vegetation change caused by climatic and Maya influences during the late Holocene. The ?13C values range from - 27.11‰ to - 21.52‰, a shift of ˜ 5.59‰, which suggests fluctuating contributions of C 3 and C 4 plants throughout the last 2.5 ka, with C 4 plant input reflecting periods of Maya agriculture. Maya activity in the study area occurred at different intensities from ˜ 2600 cal yr BP until ˜ 1500 cal yr BP, after which agricultural practices waned as the Maya depopulated the area. These changes in plant assemblages were in response to changes in available water resources, with increased aridity leading to the eventual abandonment of agricultural areas. The Ix Chel archaeological site, located in the study area, is a highland site that would have been among the first agricultural settlements to be affected during periods of aridity. During these periods, minimal water resources would have been available in this highly karstified, well-drained area, and supplemental groundwater extraction would have been difficult due to the extreme depth of the water table.

Polk, Jason S.; van Beynen, Philip E.; Reeder, Philip P.

2007-07-01

228

Compositional differences between basaltic and gabbroic clasts in mesosiderites  

NASA Astrophysics Data System (ADS)

Two gabbroic pebbles and one pebble with basaltic textural affinities from the Vaca Muerta mesosiderite were analyzed by instrumental neutron activation analysis and electron microprobe. These analyses plus literature data reveal remarkable compositional differences between basaltic and gabbroic clasts in mesosiderites. On average, basaltic clasts have small (15%) depletions in light relative to heavy rare earth elements (REEs) and moderate positive Eu anomalies (i.e., H-chondrite-normalized La/Lu= 0.85; Eu/Sm= 1.30). The mean La/Lu and Eu/Sm abundance ratios of gabbroic clasts are at least 3.3 × smaller and 28 × greater, respectively. Intense meteoroid bombardment probably persisted until after the mesosiderite parent body had differentiated. Near-surface mixtures of major amounts of basalt and lesser amounts of cumulate eucritic rocks were essentially totally melted and rapidly cooled, accounting for the moderately fractionated REE patterns of most basaltic clasts. At greater depths, impact-heating partially melted cumulate gabbros; incompatible-element-rich eutectic liquids drained away, creating large REE fractionations in the residual rocks. These rocks cooled slowly and developed gabbroic textures.

Rubin, Alan E.; Jerde, Eric A.

1988-03-01

229

High Prevalence of Helicobacter pylori hopQ II Genotype Isolated from Iranian Patients with Gastroduodenal Disorders.  

PubMed

Helicobacter pylori plays an important role in the pathogenesis of chronic gastritis, peptic ulceration, and noncardia gastric cancer. Several putative virulence factors for H. pylori have been identified including vacA, babA, and iceA. HopQ is one of the outer membrane proteins involved in bacterial adherence to gastric mucosa and has been suggested to also play a role in the virulence of H. pylori. Due to the substantial geographic differences in the prevalence of H. pylori virulence factors reported, the main purpose of the current study was to investigate the association between different H. pylori virulence hopQ alleles (types I and II) and patients with gastroduodenal disorders. The presence of H. pylori and hopQ alleles in gastric biopsy specimens was identified by specific PCR assays. H. pylori type II hopQ was found to be significantly associated with gastric cancer patients (odds ratio: 3.47, 95% CI: 1.56-5.89). Information about the prevalence of H. pylori hopQ type II can be used for determining the high-risk diseases type which is actually colonized by H. pylori hopQ type II positive strains. The presence of H. pylori hopQ type II should be investigated in different geographical regions as confirmatory findings may provide a definite biomarker attributed to the pathogenesis of certain severe digestive diseases. PMID:24672729

Talebi Bezmin Abadi, Amin; Mohabbati Mobarez, Ashraf

2014-01-01

230

Earthquake-induced soft-sediment deformation structures in Upper Jurassic open-marine microbialites (Neuquén Basin, Argentina)  

NASA Astrophysics Data System (ADS)

Penecontemporaneous decimetre-scale soft-sediment deformation structures are reported from the basal part of the Upper Jurassic-Lower Cretaceous Vaca Muerta Formation, in the Malargüe-Las Leñas area of the back-arc Neuquén Basin (Mendoza Province, Central Andes). The deformed interval (Amarillas bed) is only 0.3 to 0.9 m thick but occurs in a wide area, larger than 1500 km 2. Its age, determined by ammonite biostratigraphy, is Early Tithonian. The soft-sediment deformation structures were generated in finely laminated, partially consolidated, organic-rich, carbonate microbialites that were deposited in open-marine, poorly oxygenated settings, apparently devoid of any significant slope. Those structures include boudins of different sizes and complexity, a variety of folds, normal (listric) dm-scale faults, sub-horizontal detachment surfaces and other features, which are part of several larger-scale, complex slump structures. Deformation was dominantly plastic but near to the ductile-brittle field transition. On the basis of the observed soft-deformation structures, their geographic distribution, their lateral homogeneity, and the geodynamic framework of the basin in which it was generated, the Amarillas bed can be tentatively attributed to a large, intermediate-depth earthquake that occurred within the plate that subducted beneath the Andean continental margin and the Neuquén back-arc basin.

Martín-Chivelet, Javier; Palma, Ricardo M.; López-Gómez, José; Kietzmann, Diego A.

2011-04-01

231

Salt glands in the Jurassic metriorhynchid Geosaurus: implications for the evolution of osmoregulation in Mesozoic marine crocodyliforms  

NASA Astrophysics Data System (ADS)

The presence of salt-excreting glands in extinct marine sauropsids has been long suspected based on skull morphology. Previously, we described for the first time the natural casts of salt-excreting glands in the head of the Jurassic metriorhynchid crocodyliform Geosaurus araucanensis from the Tithonian of the Vaca Muerta Formation in the Neuquén Basin (Argentina). In the present study, salt-excreting glands are identified in three new individuals (adult, a sub-adult and a juvenile) referable to the same species. New material provides significant information on the salt glands form and function and permit integration of evolutionary scenarios proposed on a physiological basis in extant taxa with evidence from the fossil record. G. araucanensis represents an advanced stage of the basic physiological model to marine adaptations in reptiles. G. araucanensis salt glands were hypertrophied. On this basis, it can be hypothesized that these glands had a high excretory capability. This stage implies that G. araucanensis (like extant pelagic reptiles, e.g. cheloniids) could have maintained constant plasma osmolality even when seawater or osmoconforming prey were ingested. A gradual model of marine adaptation in crocodyliforms based on physiology (freshwater to coastal/estuarine to estuarine /marine to pelagic life) is congruent with the phylogeny of crocodyliforms based on skeletal morphology. The fossil record suggests that the stage of marine pelagic adaptation was achieved by the Early Middle Jurassic. Salt gland size in the juvenile suggests that juveniles were, like adults, pelagic.

Fernández, Marta; Gasparini, Zulma

2008-01-01

232

Phylogeographic Origin of Helicobacter pylori Determines Host-Adaptive Responses upon Coculture with Gastric Epithelial Cells  

PubMed Central

While Helicobacter pylori infects over 50% of the world's population, the mechanisms involved in the development of gastric disease are not fully understood. Bacterial, host, and environmental factors play a role in disease outcome. To investigate the role of bacterial factors in H. pylori pathogenesis, global gene expression of six H. pylori isolates was analyzed during coculture with gastric epithelial cells. Clustering analysis of six Colombian clinical isolates from a region with low gastric cancer risk and a region with high gastric cancer risk segregated strains based on their phylogeographic origin. One hundred forty-six genes had increased expression in European strains, while 350 genes had increased expression in African strains. Differential expression was observed in genes associated with motility, pathogenicity, and other adaptations to the host environment. European strains had greater expression of the virulence factors cagA, vacA, and babB and were associated with increased gastric histologic lesions in patients. In AGS cells, European strains promoted significantly higher interleukin-8 (IL-8) expression than did African strains. African strains significantly induced apoptosis, whereas only one European strain significantly induced apoptosis. Our data suggest that gene expression profiles of clinical isolates can discriminate strains by phylogeographic origin and that these profiles are associated with changes in expression of the proinflammatory and protumorigenic cytokine IL-8 and levels of apoptosis in host epithelial cells. These findings support the hypothesis that bacterial factors determined by the phylogeographic origin of H. pylori strains may promote increased gastric disease.

Sheh, Alexander; Chaturvedi, Rupesh; Merrell, D. Scott; Correa, Pelayo; Wilson, Keith T.

2013-01-01

233

Fine resolution chronology based on initial Sr-87/Sr-86  

NASA Technical Reports Server (NTRS)

It has been recognized that small variations in initial Sr-87/Sr-86 (Sr(sub I)), can provide a fine scale relative chronology for the chemical fractionation of materials with low Rb/Sr from parent reservoirs with high Rb/Sr. Similarly, Sr(sub I), as determined for low Rb/Sr phases in meteorites, may permit a fine resolution chronology of the recrystallization or metamorphism of planetary materials. For the establishment of a primitive Sr-87/Sr-86 chronology, it is important to search for samples with extremely low Rb/Sr for which the measured Sr-87/Sr-86 is below BABI, in which case the primitive nature of the Sr can be directly established. Using the measured Rb/Sr to calculate an initial Sr-87/Sr-86 can introduce substantial uncertainty if the Rb-Sr are disturbed. We report Sr-87/Sr-86 in plagioclase from silicate pebbles from the Vaca Muerta mesosiderite on which we have reported Sm-147-Nd-143 and Ne-142 correlations. For the purpose of cross-calibration with our previous work we have performed extensive new measurements on Angra dos Reis and on anorthite from Moore County, which have very low Rb/Sr and primitive Sr-87/Sr-86.

Stewart, B. W.; Papanastassiou, D. A.; Capo, R. C.; Wasserburg, G. J.

1993-01-01

234

Inhibition of cell-cycle progression in HeLa cells by HY52, a novel cyclin-dependent kinase inhibitor isolated from Bauhinia forficata.  

PubMed

In the course of screening for a novel inhibitor of cyclin-dependent kinase (CDK), HY52 (C17H30O2N2; molecular weight 294) was isolated from the leaves of Pata de Vaca (Bauhinia forficata). The growth of HeLa cells was inhibited in a dose-dependent manner when treated with 0.07 to 0.41 mM of HY52 for 24 h (IC50:0.11 mM). Furthermore, HY52 showed the selective inhibitory activity on CDC2 kinase purified using immunoprecipitation with an IC 50 value of 0.45 mM. A flow cytometric analysis of the HeLa cells treated with HY52 revealed an appreciable cell-cycle arrest in the G1 phase. Moreover, a TUNEL assay exhibited the apoptotic induction of HeLa cells treated with HY52. To obtain further information on the cell-cycle arrest induced by HY52, the expression of certain cell-cycle-associated proteins was examined using a Western blot analysis. The results revealed that HY52 was found to inhibit the proliferation of HeLa cells through inducing a G1-phase arrest by inhibiting pRb phosphorylation via an up-regulation of p21WAF1/CIP1 and p27KIP1, and G2/M-phase arrest by down-regulation of CDC2, cyclin A, and cyclin B1. PMID:16473670

Lim, Haeyoung; Kim, Min Kyoung; Lim, Yoongho; Cho, Youl-Hee; Lee, Chul-Hoon

2006-02-20

235

Antibacterial activities of almond skins on cagA-positive and-negative clinical isolates of Helicobacter pylori.  

PubMed

BACKGROUND: Helicobacter pylori is known to be a gastric pathogen of humans. Eradication regimens for H. pylori infection have some side effects, compliance problems, relapses, and antibiotic resistance. Therefore, the need for alternative therapies for H. pylori infections is of special interest. We have previously shown that polyphenols from almond skins are active against a range of food-borne pathogens. The aim of this study was to evaluate the antibacterial effects of natural almond skins before and after simulated human digestion and the pure flavonoid compounds epicatechin, naringenin and protocatechuic acid against H. pylori. RESULTS: H. pylori strains were isolated from gastric biopsy samples following standard microbiology procedures. Also, cagA and vacA genes were identified using PCR. Susceptibility studies on 34 strains of H. pylori, including two reference strains (ATCC 43504, ATCC 49503), were performed by the standard agar dilution method.Natural almond skin was the most effective compound against H. pylori (MIC range, 64 to 128 mug/ml), followed by natural skin post gastric digestion (MIC range, 128 to 512 mug/ml), and natural almond skin post gastric plus duodenal digestion (MIC range, 256 to 512 mug/ml). Amongst the pure flavonoid compounds, protocatechuic acid showed the greatest activity (MIC range, 128 to 512 mug/ml) against H. pylori strains. CONCLUSIONS: The Polyphenols from almond skins were effective in vitro against H. pylori, irrespective of genotype status and could therefore be used in combination with antibiotics as a novel strategy for antibiotic resistance. PMID:23659287

Bisignano, Carlo; Filocamo, Angela; La Camera, Erminia; Zummo, Sebastiana; Fera, Maria Teresa; Mandalari, Giuseppina

2013-05-01

236

Pathogenesis of Helicobacter pylori Infection  

PubMed Central

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori.

Kusters, Johannes G.; van Vliet, Arnoud H. M.; Kuipers, Ernst J.

2006-01-01

237

CagA-positive Helicobacter pylori infection is not associated with decreased risk of Barrett's esophagus in a population with high H. pylori infection rate  

PubMed Central

Background & aim The role that H. pylori infection plays in the development of and Barrett's esophagus (BE) is uncertain. We tested the hypothesis that infection with cagA+ Helicobacter pylori strains protects against the development of BE. Methods We studied 104 consecutive patients, residents in an area with a high prevalence of H. pylori infection, with BE and 213 sex- and age-matched controls. H. pylori infection and CagA antibody status were determined by western blot serology. Results H. pylori prevalence was higher in patients with BE than in controls (87.5% vs. 74.6%; OR. 2.3; 95% CI: 1.23–4.59). Increasing age was associated with a higher prevalence of H. pylori (p < 0.05). The prevalence of CagA+ H. pylori serology was similar in patients with BE and controls (64.4% vs. 54.5%; NS). Type I H. pylori infection (CagA+ and VacA+) was similar in patients with BE and controls (44.2% vs. 41.3%; NS). Logistic regression analysis identified alcohol (O.R. 7.09; 95% CI 2.23–22.51), and H. pylori infection (OR: 2.41; 95%CI: 1.20–4.84) but not CagA+ serology as independent factors. Conclusion Neither H. pylori infection nor H. pylori infection by CagA+ strains reduce the risk of BE in a population with high prevalence of H. pylori infection.

Ferrandez, Angel; Benito, Rafael; Arenas, Juan; Garcia-Gonzalez, Maria Asuncion; Sopena, Federico; Alcedo, Javier; Ortego, Javier; Sainz, Ricardo; Lanas, Angel

2006-01-01

238

Flagellar Localization of a Helicobacter pylori Autotransporter Protein  

PubMed Central

ABSTRACT Helicobacter pylori contains four genes that are predicted to encode proteins secreted by the autotransporter (type V) pathway. One of these, the pore-forming toxin VacA, has been studied in great detail, but thus far there has been very little investigation of three VacA-like proteins. We show here that all three VacA-like proteins are >250 kDa in mass and localized on the surface of H. pylori. The expression of the three vacA-like genes is upregulated during H. pylori colonization of the mouse stomach compared to H. pylori growth in vitro, and a wild-type H. pylori strain outcompeted each of the three corresponding isogenic mutant strains in its ability to colonize the mouse stomach. One of the VacA-like proteins localizes to a sheath that overlies the flagellar filament and bulb, and therefore, we designate it FaaA (flagella-associated autotransporter A). In comparison to a wild-type H. pylori strain, an isogenic faaA mutant strain exhibits decreased motility, decreased flagellar stability, and an increased proportion of flagella in a nonpolar site. The flagellar localization of FaaA differs markedly from the localization of other known autotransporters, and the current results reveal an important role of FaaA in flagellar localization and motility.

Radin, Jana N.; Gaddy, Jennifer A.; Gonzalez-Rivera, Christian; Loh, John T.; Algood, Holly M. Scott; Cover, Timothy L.

2013-01-01

239

A Novel Line Immunoassay Based on Recombinant Virulence Factors Enables Highly Specific and Sensitive Serologic Diagnosis of Helicobacter pylori Infection  

PubMed Central

Helicobacter pylori colonizes half of the world's population, and infection can lead to ulcers, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. Serology is the only test applicable for large-scale, population-based screening, but current tests are hampered by a lack of sensitivity and/or specificity. Also, no serologic test allows the differentiation of type I and type II strains, which is important for predicting the clinical outcome. H. pylori virulence factors have been associated with disease, but direct assessment of virulence factors requires invasive methods to obtain gastric biopsy specimens. Our work aimed at the development of a highly sensitive and specific, noninvasive serologic test to detect immune responses to important H. pylori virulence factors. This line immunoassay system (recomLine) is based on recombinant proteins. For this assay, six highly immunogenic virulence factors (CagA, VacA, GroEL, gGT, HcpC, and UreA) were expressed in Escherichia coli, purified, and immobilized to nitrocellulose membranes to detect serological immune responses in patient's sera. For the validation of the line assay, a cohort of 500 patients was screened, of which 290 (58.0%) were H. pylori negative and 210 (42.0%) were positive by histology. The assay showed sensitivity and specificity of 97.6% and 96.2%, respectively, compared to histology. In direct comparison to lysate blotting and enzyme-linked immunosorbent assay (ELISA), the recomLine assay had increased discriminatory power. For the assessment of individual risk for gastrointestinal disease, the test must be validated in a larger and defined patient cohort. Taking the data together, the recomLine assay provides a valuable tool for the diagnosis of H. pylori infection.

Formichella, Luca; Romberg, Laura; Bolz, Christian; Vieth, Michael; Geppert, Michael; Gottner, Gereon; Nolting, Christina; Walter, Dirk; Schepp, Wolfgang; Schneider, Arne; Ulm, Kurt; Wolf, Petra; Busch, Dirk H.; Soutschek, Erwin

2013-01-01

240

Cytopathic effects of toxogenic strains of Helicobacter pylori on different cell lines.  

PubMed

Purpose: Many virulence factors are involved in the pathomechanism of infection caused by Helicobacter pylori. Toxins such as vacuolating cytotoxin, encoded by the vacA gene and the immunogenic protein cagA, encoded by the cagA gene (cytotoxin-associated gene) are major factors conferring the property of virulence. The current study is aimed at isolation of H. pylori and separation of its toxin from antral biopsies of patients. Materials and Methods: The following cell lines were used to demonstrate the cytopathic effect (CPE) of the separated toxin: African green monkey kidney (Vero), baby hamster kidney, human lung carcinoma (LLC-MK2), and human epithelial. Results: H. pylori was isolated from 27 out of 45 patients (60%) selected for the study. CPE of H. pylori toxin was highly significant on Vero cells than other cell lines used as it reached a high dilution titer of toxin (1/16) in 13 isolated strains (48.15%). No significant difference in CPE of toxin in different dilutions was detected among other cell lines used in different groups. H. pylori toxin could be detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis as a distinct band with a molecular weight ranging between 66 and 97 kDa and closely related to 87 kDa. Conclusion: H. pylori vacuolating cytotoxin plays a vital role in the pathogenesis of gastroduodenal diseases (gastritis, gastric ulcer, duodenal ulcer, and gastric cancer). The Vero cell lines were found to be the most suitable form of tissue culture when compared with other cell lines used in our study for demonstrating the activity of H. pylori toxin. PMID:24943747

Gowda, K Lakshmana; Marie, Mohammed Ali M; John, James; Pradeep, C S; Dabwan, Khaled Homoud M; Sangeetha, G

2014-01-01

241

Association between Helicobacter pylori Virulence Factors and Gastroduodenal Diseases in Okinawa, Japan  

PubMed Central

The incidence of gastric cancer in Okinawa is lowest in Japan. Some previous reports using small number of strains suggested that the high prevalence of Helicobacter pylori with Western-type cagA in Okinawa compared to other areas in Japan might contribute to the low incidence of gastric cancer. It has still not been confirmed why the prevalence of Western-type cagA strains is high in Okinawa. We examined the association between the virulence factors of H. pylori and gastroduodenal diseases in Okinawa. The genotypes of cagA and vacA of 337 H. pylori strains were determined by PCR and gene sequencing. The genealogy of these Western-type cagA strains in Okinawa was analyzed by multilocus sequence typing (MLST). Overall, 86.4% of the strains possessed cagA: 70.3% were East-Asian type and 16.0% were Western type. After adjustment by age and sex, the presence of East-Asian-type cagA/vacA s1m1 genotypes was significantly associated with gastric cancer compared to gastritis (odds ratio = 6.68, 95% confidence interval = 1.73 to 25.8). The structure of Western-type CagA in Okinawa was different from that of typical Western-type CagA found in Western countries. Intriguingly, MLST analysis revealed that the majority of Western-type cagA strains formed individual clusters but not hpEurope. Overall, low prevalence of gastric cancer in Okinawa may result from the high prevalence of non-East-Asian-type cagA strains. The origin of Western-type cagA strains in Okinawa may be different from those of Western countries.

Matsunari, Osamu; Shiota, Seiji; Suzuki, Rumiko; Watada, Masahide; Kinjo, Nagisa; Murakami, Kazunari; Fujioka, Toshio; Kinjo, Fukunori

2012-01-01

242

Helicobacter pylori in Iran: A systematic review on the association of genotypes and gastroduodenal diseases  

PubMed Central

Background: Helicobacter pylori (H. pylori) infection is known as a major etiologic factor for a variety of gastroduodenal diseases. In Iran, with a high rate of H. pylori infection close to 90%, numerous studies have revealed many aspects of interaction between the bacterium, mucosal surface and induction of disease outcome. The organism is genetically diverse and several virulence factors are attributed to the more virulent strains. The well-characterized virulence factors of H. pylori are cytotoxin associated gene A and vacuolating cytotoxin gene A. The distribution pattern of H. pylori genotypes and its association with disease status varies geographically. The present review focused on the virulence factors and genotyping of H. pylori in relation to gastroduodenal disorders in different regions of Iran. Methods: In total, 398 studies were reported on different aspects related to H. pylori in our electronic search from 1995-2011. H. pylori infection and its virulence factors in association with disease status were investigated in 159 reports. Looking specifically at the gastrointestinal tract disorders, the most relevant reports including 37 papers were selected. Results: We found no correlation of cagA genotype and disease status in the majority of studies, whereas vacA was demonstrated as a useful marker in predicting the disease outcome. The results of reports on other virulence factors of H. pylori such as blood group antigen-binding adhesion gene A, the induced by contact with epithelium gene A, the outer inflammatory protein A, the duodenal ulcer promoting gene A, and Helicobacter outer membrane gene and their relation with disease status were contradictory. Conclusions: Although different markers of H. pylori were emphasized as useful when predicting disease outcomes in some studies, the inconsistent researches and the scarcity of data made any conclusion or even comparison impossible. Considering the gap of information observed during our search relating to genotyping and other aspects of H. pylori infection, further investigations are suggested.

Hosseini, Elham; Poursina, Farkhondeh; de Wiele, Tom Van; Safaei, Hajieh Ghasemian; Adibi, Peyman

2012-01-01

243

39Ar- 40Ar ages and thermal history of mesosiderites  

NASA Astrophysics Data System (ADS)

Determinations of 39Ar- 40Ar ages for plagioclase separates of three clasts from the Vaca Muerta and Mount Padbury mesosiderites give similar results. Ages increase monotonically by ˜0.2-0.3 Ga when plotted against increasing 39Ar release from the samples and give average values of ˜3.95 Ga. When combined with revised ages for mesosiderite analyses previously reported, nineteen analyses of thirteen mesosiderites give an average Ar-Ar age of 3.94 ± 0.10 Ga. The average age at 90% 39Ar release is 4.13 ±0.14 Ga, and the ages at 10% 39Ar release range over 3.32-3.97 Ga. It seems unlikely that the 39Ar- 40Ar ages were produced by direct impact heating, but they probably are independent evidence for slow cooling deep within the mesosiderite parent body. We conclude that the sloped age plateaus and the significant range in Ar-Ar closure temperatures calculated for these mesosiderites (˜75-340°C) are due to significant differences in Ar diffusion properties among samples. From the Ar diffusion data, we estimate an approximate mesosiderite cooling rate of ˜0.2°C/Ma, which is similar to the preferred cooling rate of 0.1-0.5°C/Ma derived by others from Ni diffusion and metal textures. The 39Ar/ 40Ar ages seem incompatible with very slow cooling rates of <0.2°C/Ma, unless the closure temperatures for Ar diffusion and formation of metal cooling textures on the parent body substantially overlap. Any possible role of fragmentation of the mesosiderite parent body in producing the younger Ar-Ar ages and the very slow cooling rates is unclear.

Bogard, Donald D.; Garrison, Daniel H.

1998-04-01

244

Bitumen veins and Eocene transpression, Neuquén Basin, Argentina  

NASA Astrophysics Data System (ADS)

In the northwestern part of the petroleum-rich Neuquén Basin, veins of solid hydrocarbon (bitumen) have been reported from over 150 localities. The bitumen veins are mostly steeply-dipping and show intrusive relationships with their wall rocks. The largest are some 8 m wide, 8 km long and probably several kilometres deep. The bitumen probably formed in the earliest stages of thermal maturation of organically-rich source rocks. The most likely source rocks for the bitumen, as well as for most of the oil and gas in the Neuquén Basin, are black marine shales of the Vaca Muerta and Agrio formations. These were deposited in a rift setting during the late Jurassic and Early Cretaceous. According to subsidence models, the source rocks should have reached thermal maturity in the latest Cretaceous or Paleocene and should have remained in the oil window ever since. Although the bitumen has not been dated directly, the veins probably formed soon after maturation of the source rocks, in other words, in the Paleocene or Eocene. The wall rocks of the veins are mostly the source rocks themselves. Other veins have been emplaced into overlying strata of Early Cretaceous to Paleocene ages or into underlying sediments of Jurassic age. The bitumen veins have preferred orientations. The dominant trend is 060° and subsidiary trends are either 000° to 020° or 100°. As in other basins worldwide, the majority of bitumen veins in the Neuquén Basin probably formed by tensile failure, in orientations perpendicular to the least compressive stress, under the combined effects of regional tectonics and fluid overpressures. The orientations of the veins are compatible with the direction of oblique convergence between continental South America and the oceanic Nazca plate in the Eocene. Many major structures in the Neuquén Basin are also of Eocene age and may have formed under right-lateral transpression.

Cobbold, P. R.; Diraison, M.; Rossello, E. A.

1999-12-01

245

Classification of mafic clasts from mesosiderites: Implications for endogenous igneous processes  

SciTech Connect

The authors have analyzed thirteen igneous pebbles from the Vaca Muerta, EET87500, and Bondoc mesosiderites by electron microprobe and instrumental neutron activation and combined these data with literature data for forty-three analyzed mesosiderite clasts. They classify these well-characterized clasts into the following five principal groups: (1) Polygenic and monogenic cumulates (39%) are coarse-grained gabbros that are highly depleted in incompatible elements (relative to H chondrites); they formed at moderate depth either as residues of low-degree partial melting of pre-existing cumulate eucrites or as cumulates from parent melts similar to cumulate eucrites. (2) Polygenic basalts (30%) are finer-grained rocks with positive europium anomalies, La/Lu ratios < 1, and lower rare earth element abundances than basaltic eucrites. It seems likely that these rocks were formed near their parent body surface by remelting mixtures of major amounts of basaltic eucrites and lesser amounts of cumulate eucrites. (3) Quench-textured rocks comprise two compositional groups, (a) those which resemble basaltic eucrites (5%), and (b) those which resemble cumulate eucrites (2%). The quench-textured rocks are probably monogenic; they formed most likely when small-scale impacts at their parent body surface totally melted small amounts of basaltic or cumulate eucrite material. (4) Monogenic basalts (11%) resemble basaltic eucrites and formed by endogenous igneous processes on the mesosiderite parent body (MPB). (5) Ultramafic rocks are cumulates consisting mainly of large crystals of orthopyroxene (9%) or olivine (4%). Orthopyroxenite clasts closely resemble diogenites and were formed most likely by endogenous igneous processes.

Rubin, A.E. (Univ. of California, Los Angeles (United States)); Mittlefehldt, D.W. (Lockheed Engineering and Science Co., Houston, TX (United States))

1992-02-01

246

A novel line immunoassay based on recombinant virulence factors enables highly specific and sensitive serologic diagnosis of Helicobacter pylori infection.  

PubMed

Helicobacter pylori colonizes half of the world's population, and infection can lead to ulcers, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. Serology is the only test applicable for large-scale, population-based screening, but current tests are hampered by a lack of sensitivity and/or specificity. Also, no serologic test allows the differentiation of type I and type II strains, which is important for predicting the clinical outcome. H. pylori virulence factors have been associated with disease, but direct assessment of virulence factors requires invasive methods to obtain gastric biopsy specimens. Our work aimed at the development of a highly sensitive and specific, noninvasive serologic test to detect immune responses to important H. pylori virulence factors. This line immunoassay system (recomLine) is based on recombinant proteins. For this assay, six highly immunogenic virulence factors (CagA, VacA, GroEL, gGT, HcpC, and UreA) were expressed in Escherichia coli, purified, and immobilized to nitrocellulose membranes to detect serological immune responses in patient's sera. For the validation of the line assay, a cohort of 500 patients was screened, of which 290 (58.0%) were H. pylori negative and 210 (42.0%) were positive by histology. The assay showed sensitivity and specificity of 97.6% and 96.2%, respectively, compared to histology. In direct comparison to lysate blotting and enzyme-linked immunosorbent assay (ELISA), the recomLine assay had increased discriminatory power. For the assessment of individual risk for gastrointestinal disease, the test must be validated in a larger and defined patient cohort. Taking the data together, the recomLine assay provides a valuable tool for the diagnosis of H. pylori infection. PMID:24006137

Formichella, Luca; Romberg, Laura; Bolz, Christian; Vieth, Michael; Geppert, Michael; Göttner, Gereon; Nölting, Christina; Walter, Dirk; Schepp, Wolfgang; Schneider, Arne; Ulm, Kurt; Wolf, Petra; Busch, Dirk H; Soutschek, Erwin; Gerhard, Markus

2013-11-01

247

Inter- and intra-plate deformation at North American plate boundaries  

NASA Astrophysics Data System (ADS)

A geodetic network which spans the region between San Francisco and Lake Tahoe has been measured 5 times completely with triangulation in 1880, 1922, 1929, 1943, 1963. A resurvey with the Global Positioning System (GPS) in 1991 allows the formation of 1 coseismic and 4 interseismic epochs. The data from this network provide a unique opportunity to examine the temporal and spatial evolution of the strain field associated with the 1906 San Francisco earthquake in particular and with the Pacific-North American plate boundary in general. Calculations of strain rate from the network data lead to the following conclusions. (1) There is no resolvable (greater than 0.05 microradians/yr) strain in between Sutter Buttes and the Sierra Nevada. (2) Throughout the time since the 1906 earthquake, a region extending at least as far east as the westernmost Great Valley has been undergoing deformation related to Pac:Nam interaction and the associated earthquake cycle. (3) In the time and space of overlap, our results agree with those from the United States Geological Survey (USGS) trilateration data. Both data sets indicate that strain must be accumulating to the east of Vaca. (4) The San Andreas discrepancy cannot be accommodated in the Great Valley at the 1 sigma level of our results. It is possible to absorb it in that region at the 2 sigma level. (5) Strain rate is elevated in the years following the earthquake and decays slowly with time. It is possible that the rate in the Coast Ranges increases until around 1950 and then decays. With the exception of one epoch, strain rate in the Coast Ranges is consistently fault parallel, shows no sign changes, and is consistent with monotonic strain accumulation.

Beavan, John; Gilbert, Lewis E.; Scholz, Chris

1992-07-01

248

Volatile (sulphur and chlorine), major, and trace element geochemistry of mafic to intermediate tephras from the Chilean Southern Volcanic Zone (33-43°S)  

NASA Astrophysics Data System (ADS)

Here we present the first systematic investigation of volatile geochemistry along the Southern Volcanic Zone (SVZ) of Chile. Holocene olivine-hosted melt inclusions in the most mafic tephras sampled from 16 volcanoes along the volcanic front of the SVZ between 33°S and 43°S were analysed for pre-eruptive sulphur, chlorine, and major element contents. These results are combined with trace element compositions of the host whole rocks. The highest fractionation-corrected gas contents occur in the least-degassed melt inclusions from small monogenetic cones of Los Hornitos, Cabeza de Vaca, and Apagado from both the transitional and the southern-central SVZ, reaching ~3,000 ?g/g S and 1,400 ?g/g Cl, while the lowest abundances of ~1,100 ?g/g S and ~600 ?g/g Cl were found in the central SVZ at Volcán Lonquimay, Volcán Llaima, and Volcán Villarrica. Chlorine co-varies with trace element indicators for the degree of melting and/or source enrichment, such that the lowest Cl contents are found in high-degree melts from the most depleted mantle sources. The size of the volcanic edifices correlates inversely with Cl abundances in the melt. This could reflect more extensive degassing during ascent through the complex magma plumbing systems beneath the stratovolcanoes or greater dilution during larger degrees of melting of more depleted sources, or a combination of these factors. Compared to other subduction zones, the SVZ melt inclusions exhibit Cl and S abundances in the same range as most of those from the Central American and those from the Marianas arcs.

Wehrmann, Heidi; Hoernle, Kaj; Jacques, Guillaume; Garbe-Schönberg, Dieter; Schumann, Kai; Mahlke, Julia; Lara, Luis E.

2014-03-01

249

Vacuoles of Candida yeast as a specialized niche for Helicobacter pylori.  

PubMed

Helicobacter pylori (H. pylori) are resistant to hostile gastric environments and antibiotic therapy, reflecting the possibility that they are protected by an ecological niche, such as inside the vacuoles of human epithelial and immune cells. Candida yeast may also provide such an alternative niche, as fluorescently labeled H. pylori were observed as fast-moving and viable bacterium-like bodies inside the vacuoles of gastric, oral, vaginal and foodborne Candida yeasts. In addition, H. pylori-specific genes and proteins were detected in samples extracted from these yeasts. The H. pylori present within these yeasts produce peroxiredoxin and thiol peroxidase, providing the ability to detoxify oxygen metabolites formed in immune cells. Furthermore, these bacteria produce urease and VacA, two virulence determinants of H. pylori that influence phago-lysosome fusion and bacterial survival in macrophages. Microscopic observations of H. pylori cells in new generations of yeasts along with amplification of H. pylori-specific genes from consecutive generations indicate that new yeasts can inherit the intracellular H. pylori as part of their vacuolar content. Accordingly, it is proposed that yeast vacuoles serve as a sophisticated niche that protects H. pylori against the environmental stresses and provides essential nutrients, including ergosterol, for its growth and multiplication. This intracellular establishment inside the yeast vacuole likely occurred long ago, leading to the adaptation of H. pylori to persist in phagocytic cells. The presence of these bacteria within yeasts, including foodborne yeasts, along with the vertical transmission of yeasts from mother to neonate, provide explanations for the persistence and propagation of H. pylori in the human population. This Topic Highlight reviews and discusses recent evidence regarding the evolutionary adaptation of H. pylori to thrive in host cell vacuoles. PMID:24833856

Siavoshi, Farideh; Saniee, Parastoo

2014-05-14

250

Helicobacter pylori infection induces duodenitis and superficial duodenal ulcer in Mongolian gerbils  

PubMed Central

Background: There is no direct evidence for an animal model of Helicobacter pylori induced duodenal ulcer. Aim: In this study we evaluated the roles of bacterial strain and age of experimental animals in induction of duodenitis and duodenal ulcer in Mongolian gerbils after H pylori infection. Methods: Specific pathogen free Mongolian gerbils were inoculated orally with three bacterial strains (H pylori ATCC 43504, TN2GF4, and K-6, a clinical isolate from a patient with gastric cancer in our clinic). These strains have both the cagA gene and VacA. Five week old gerbils were used to emulate prematurity infection and 14 week old animals were used as mature test subjects. Animals were observed for 12 weeks after inoculation. Interleukin 8 (IL-8) production in gastric epithelial cells (MKN74) after coculture with the H pylori strains was measured by ELISA. Results: Gastritis and gastric ulcers were found in all gerbils infected with the three strains. However, duodenitis and gastric metaplasia were seen more frequently in gerbils infected with TN2GF4 and K-6 strains than in the ATCC 43504 infected or control groups (p<0.05). Superficial duodenal ulcers with severe duodenitis and gastric metaplasia were found in two gerbils inoculated at 14 weeks with the TN2GF4 strain but none at five weeks. The TN2GF4 strain stimulated significantly higher levels of IL-8 than ATCC 43504 and K6 strains (p=0.0039). Conclusions: When injected into adult Mongolian gerbils, a specific strain (TN2GF4) of H pylori can induce duodenitis with gastric metaplasia and superficial duodenal ulcers. Induction of duodenal ulcer in an animal model fulfills the requirements of Koch’s postulates for establishing a role for H pylori as a causative agent.

Ohkusa, T; Okayasu, I; Miwa, H; Ohtaka, K; Endo, S; Sato, N

2003-01-01

251

Prospective study of Helicobacter pylori biomarkers for gastric cancer risk among Chinese men  

PubMed Central

Background Helicobacter pylori is the leading risk factor for gastric cancer, yet only a fraction of infected individuals ever develop neoplasia. Methods To identify potential predictive biomarkers, we assessed the association of 15 antibodies to Helicobacter pylori proteins and gastric cancer in a nested case-control study. Blood levels of antibodies were assessed using multiplex serology for 226 incident cases and 451 matched controls from the Shanghai Men’s Health Study. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression. Results Sero-positivity to four (Omp, HP0305, HyuA, and HpaA) proteins were associated with a one-and-a-half to three-fold increased risk for gastric cancer. When excluding cases diagnosed within two years of study enrollment, sero-positivity to two additional proteins (CagA and VacA) showed significant associations with risk. Compared to individuals with ?3 sero-positive results to the six virulent proteins identified in this population, individuals with 4–5 sero-posit ive results were at a two-fold increased risk (OR=2.08, 95% CI: 1.31–3.30) and individuals sero-positive to all 6 proteins had a three-and-a-half-fold increase in risk (OR=3.49, 95% CI: 2.00–6.11) for gastric cancer. Among individuals diagnosed at least two years after study enrollment, these associations were even stronger (OR=2.79 and OR=4.16, respectively). Conclusions Increasing number of sero-positives to six H. pylori proteins may be a risk marker for distal gastric cancer in China. Impact In a population with a 90% prevalence of CagA-positive H. pylori infection, assessment of additional virulent H. pylori proteins might better identify individuals at high risk for gastric cancer.

Epplein, Meira; Zheng, Wei; Xiang, Yong-Bing; Peek, Richard M.; Li, Honglan; Correa, Pelayo; Gao, Jing; Michel, Angelika; Pawlita, Michael; Cai, Qiuyin; Shu, Xiao-Ou

2012-01-01

252

Inhibition of Helicobacter pylori growth and its cytotoxicity by 2-hydroxy 4-methoxy benzaldehyde of Decalepis hamiltonii (Wight & Arn); a new functional attribute.  

PubMed

Helicobacter pylori mediated gastric ulcer and cancers are common global problems since it was found to colonize in ?50% of gastric ulcer/cancer patients. Decalepis hamiltonii, (Asclepiadaceae family) extracts have been depicted with medicinal properties supporting the traditional knowledge of health beneficial attributes of D. hamiltonii. Previously we have shown that both aqueous as well as methanol extracts of D. hamiltonii containing abundant phenolics with predominant levels (20-40% of total phenolics) of 2-hydroxy-4-methoxy benzaldehyde (HMBA). Despite higher levels, HMBA contributed very little to the antioxidant activity (<10%) when compared to other phenolic compounds in the extract. In the current study we attempted to explore antimicrobial property, particularly anti-H. pylori activity, since traditional users document D. hamiltonii as a fighter of microbial infections. HMBA was isolated from the roots of D. hamiltonii by hydrodistillation and cold crystallization method; identified by HPLC and characterized using ESI-MS and confirmed by NMR studies as a compound of molecular mass 152 Da. Isolated HMBA was found to inhibit the growth of H. pylori, a potential ulcerogen in a dose dependent manner with MIC of ?39 ?g/mL as apposed to that of amoxicillin (MIC - 26 ?g/mL) for which H. pylori is susceptible. Results were further substantiated by the lysis of H. pylori by electron microscopy and electrophoretic studies. Studies on the mechanism of action indicated the counteracting effect of vacuolating toxin (VacA) of H. pylori which otherwise would lead to host cell cytotoxicity. Further the increased binding ability of HMBA to DNA and protein offered an impact on DNA protectivity and bioavailability. Results for the first time provide a direct evidence for anti-microbial attribute of HMBA. Insignificant antioxidant attribute of HMBA also reveals the anti-H. pylori activity via mechanisms other than antioxidative routes. PMID:21185348

Srikanta, Belagihalli M; Nayaka, Mysore A Harish; Dharmesh, Shylaja M

2011-04-01

253

J-Western Forms of Helicobacter pylori cagA Constitute a Distinct Phylogenetic Group with a Widespread Geographic Distribution  

PubMed Central

Chronic infection with Helicobacter pylori strains expressing the bacterial oncoprotein CagA confers an increased risk of gastric cancer. While much is known about the ancestry and molecular evolution of Western, East Asian, and Amerindian cagA sequences, relatively little is understood about a fourth group, known as “J-Western,” which has been detected mainly in strains from Okinawa, Japan. We show here that J-Western cagA sequences have a more widespread global distribution than previously recognized, occur in strains with multiple different ancestral origins (based on multilocus sequence typing [MLST] analysis), and did not arise recently. As shown by comparisons of Western and J-Western forms of CagA, there are 45 fixed or nearly fixed amino acid differences, and J-Western forms contain a unique 4-amino-acid insertion. The mean nucleotide diversity of synonymous sites (?s) is slightly lower in the J-Western group than in the Western and East Asian groups (0.066, 0.086, and 0.083, respectively), which suggests that the three groups have comparable, but not equivalent, effective population sizes. The reduced ?s of the J-Western group is attributable to ancestral recombination events within the 5? region of cagA. Population genetic analyses suggest that within the cagA region encoding EPIYA motifs, the East Asian group underwent a marked reduction in effective population size compared to the Western and J-Western groups, in association with positive selection. Finally, we show that J-Western cagA sequences are found mainly in strains producing m2 forms of the secreted VacA toxin and propose that these functionally interacting proteins coevolved to optimize the gastric colonization capacity of H. pylori.

Duncan, Stacy S.; Valk, Pieter L.; Shaffer, Carrie L.

2012-01-01

254

Proteasome Particle-Rich Structures Are Widely Present in Human Epithelial Neoplasms: Correlative Light, Confocal and Electron Microscopy Study  

PubMed Central

A novel cytoplasmic structure has been recently characterized by confocal and electron microscopy in H. pylori-infected human gastric epithelium, as an accumulation of barrel-like proteasome reactive particles colocalized with polyubiquitinated proteins, H. pylori toxins and the NOD1 receptor. This proteasome particle-rich cytoplasmic structure (PaCS), a sort of focal proteasome hyperplasia, was also detected in dysplastic cells and was found to be enriched in SHP2 and ERK proteins, known to play a role in H. pylori-mediated gastric carcinogenesis. However, no information is available on its occurrence in neoplastic growths. In this study, surgical specimens of gastric cancer and various other human epithelial neoplasms have been investigated for PaCSs by light, confocal and electron microscopy including correlative confocal and electron microscopy (CCEM). PaCSs were detected in gastric cohesive, pulmonary large cell and bronchioloalveolar, thyroid papillary, parotid gland, hepatocellular, ovarian serous papillary, uterine cervix and colon adenocarcinomas, as well as in pancreatic serous microcystic adenoma. H. pylori bodies, their virulence factors (VacA, CagA, urease, and outer membrane proteins) and the NOD1 bacterial proteoglycan receptor were selectively concentrated inside gastric cancer PaCSs, but not in PaCSs from other neoplasms which did, however, retain proteasome and polyubiquitinated proteins reactivity. No evidence of actual microbial infection was obtained in most PaCS-positive neoplasms, except for H. pylori in gastric cancer and capsulated bacteria in a colon cancer case. Particle lysis and loss of proteasome distinctive immunoreactivities were seen in some tumour cell PaCSs, possibly ending in sequestosomes or autophagic bodies. It is concluded that PaCSs are widely represented in human neoplasms and that both non-infectious and infectious factors activating the ubiquitin-proteasome system are likely to be involved in their origin. PaCS detection might help clarify the role of the ubiquitin-proteasome system in carcinogenesis.

Vanoli, Alessandro; Manca, Rachele; Ricci, Vittorio; Solcia, Enrico

2011-01-01

255

Prevalence of virulent Helicobacter pylori strains in patients affected by idiopathic dysrhythmias.  

PubMed

Helicobacter pylori virulent strains have been shown to affect cardiovascular diseases through molecular mimicry mechanisms. Silent autoimmune myocarditis has been hypothesized to be the cause of idiopathic dysrhythmias (IA). The aim of this study is to assess the prevalence of virulent H. pylori strains in patients affected by IA. In this study,54 patients (40 men, mean age 44 ± 17 years) affected by IA and 50 healthy subjects (34 men, mean age 45 ± 9) were evaluated. IA, defined as dysrhythmias with no evidence of other cardiac pathology, were either supraventricular (SVA, 23 patients; mean age 45 ± 15 years) or ventricular (VA, 31 patients; mean age 42 ± 18 years). H. pylori infection and gastrointestinal (GI) symptoms were evaluated. H. pylori strains expressing the cytotoxin-associated gene A (cagA) and the vacuolating-cytotoxin A (vacA) were also assessed through western blot. The prevalence of H. pylori is similar in IA patients and in controls (42 vs. 44%; p > 0.05); H. pylori infection is observed in 48 and 39% of the patients are affected by SVA and VA, respectively. The prevalence of CagA-positive strains is increased in IA patients compared to controls (65 vs. 42%; p < 0.01); similarly, the prevalence of VacA-positive strains is also increased in IA patients (74 vs. 46%; p < 0.006). Excluding belching, infected patients did not show any difference in GI symptoms, when compared to non-infected subjects. From this study it is concluded that there is an epidemiological link between CagA and VacA-positive H. pylori strains in IA patients. PMID:21562783

Franceschi, Francesco; Brisinda, Donatella; Buccelletti, Francesco; Ruggieri, Maria Pia; Gasbarrini, Antonio; Sorbo, Annarita; Marsiliani, Davide; Venuti, Angela; Fenici, Peter; Gasbarrini, Giovanni; Silveri, Nicolò Gentiloni; Fenici, Riccardo

2013-06-01

256

Helicobacter pylori represses proton pump expression and inhibits acid secretion in human gastric mucosa  

PubMed Central

Background and aims Helicobacter pylori infection of gastric mucosa causes gastritis and transient hypochlorhydria, which may provoke emergence of a mucosal precancer phenotype; H pylori strains containing a cag pathogenicity island (PAI) augment cancer risk. Acid secretion is mediated by the catalytic ? subunit of parietal cell H,K-ATPase (HK?). In AGS gastric epithelial cells, H pylori induces nuclear factor-?B (NF-?B) binding to and repression of transfected HK? promoter activity. This study sought to identify bacterial genes involved in HK? repression and to assess their impact on acid secretion. Methods and results AGS cells transfected with an HK? promoter construct or human gastric body biopsies were infected with wild-type (wt) or isogenic mutant (IM) H pylori strains. AGS cell HK? promoter activity, and biopsy HK? mRNA, protein and H+ secretory activity were measured by luminometry, reverse transcription—PCR, immunoblotting and extracellular acidification, respectively. Wt H pylori and ?vacA, ?ureA, ?slt and ?flaA IM strains repressed HK? promoter activity by ~50%, a ?cagA IM strain repressed HK? by ~33%, and ?cagE, ?cagM and ?cagL IM strains elicited no HK? repression. Wt H pylori-infected biopsies had markedly reduced HK? mRNA and protein compared with IM strain infections or mock-infected controls. Histamine-stimulated, SCH28080-sensitive biopsy acid secretion was significantly inhibited by wt but not by ?cagL IM H pylori infection compared with vehicle-only controls. Conclusions It is concluded that H pylori cag PAI gene products CagE, CagM, CagL and, possibly, CagA are mechanistically involved in repression of HK? transcription. Further, acute H pylori infection of human gastric mucosa downregulates parietal cell H,K-ATPase expression, significantly inhibiting acid secretion.

Saha, Arindam; Hammond, Charles E; Beeson, Craig; Peek, Richard M; Smolka, Adam J

2010-01-01

257

Molecular epidemiology, population genetics, and pathogenic role of Helicobacter pylori  

PubMed Central

Helicobacter pylori infection is linked to various gastroduodenal diseases; however, only approximately 20% of infected individuals develop severe diseases. Despite the high prevalence of H. pylori infection in Africa and South Asia, the incidence of gastric cancer in these areas is much lower than in other countries. Furthermore, the incidence of gastric cancer tends to decrease from north to south in East Asia. Such geographic differences in the pathology can be explained, at least in part, by the presence of different types of H. pylori virulence factors, especially cagA, vacA, and the right end of the cag pathogenicity island. The genotype of the virulence genes is also useful as a tool to track human migration utilizing the high genetic diversity and frequent recombination between different H. pylori strains. Multilocus sequence typing (MLST) analysis using 7 housekeeping genes can also help predict the history of human migrations. Population structure analysis based on MLST has revealed 7 modern population types of H. pylori, which derived from 6 ancestral populations. Interestingly, the incidence of gastric cancer is closely related to the distribution of H. pylori populations. The different incidence of gastric cancer can be partly attributed to the different genotypes of H. pylori circulating in different geographic areas. Although approaches by MLST and virulence factors are effective, these methods focus on a small number of genes and may miss information conveyed by the rest of the genome. Genome-wide analyses using DNA microarray or whole-genome sequencing technology give a broad view on the genome of H. pylori. In particular, next-generation sequencers, which can read DNA sequences in less time and at lower costs than Sanger sequencing, enabled us to efficiently investigate not only the evolution of H. pylori, but also novel virulence factors and genomic changes related to drug resistance.

Suzuki, Rumiko; Shiota, Seiji; Yamaoka, Yoshio

2012-01-01

258

Commercial PCV2a-based vaccines are effective in protecting naturally PCV2b-infected finisher pigs against experimental challenge with a 2012 mutant PCV2.  

PubMed

Current commercial PCV2 vaccines are all based on PCV2a and have been shown to be effective in reducing PCV2a and PCV2b viremia and PCV2-associated lesions and disease. The recent emergence of novel mutant PCV2 (mPCV2) strains and linkage of mPCV2 with cases of porcine circovirus associated disease (PCVAD) in vaccinated herds have raised concerns over emergence of vaccine-escape mutants and reduced efficacy of PCV2a-based vaccines. The aim of this study was to determine the ability of three commercial PCV2a-based vaccines administered in the presence of an ongoing PCV2b infection and passively-acquired anti-PCV2 antibodies to protect conventional pigs against experimental challenge with mPCV2 at 11 weeks of age. Fifty naturally PCV2b-infected 2-week-old pigs were divided into five treatment groups with 10 pigs each. Pigs were unvaccinated (positive and negative controls) or vaccinated at 3 (VAC-A, VAC-B, VAC-C) and at 5 weeks of age (VAC-C). At 11 weeks of age, all pigs except the negative controls were challenged with a 2012 U.S. strain of mPCV2. The experiment was terminated 21 days after challenge. Under the conditions of this study, vaccinated pigs were protected against PCV2 viremia and lesions whereas non-vaccinated pigs were not. Moreover, concurrent PCV2b and mPCV2 infection was demonstrated in all positive controls and 3/10 had microscopic lesions consistent with PCVAD while negative controls infected with PCV2b alone did not develop PCVAD. The results indicate that concurrent PCV2b/mPCV2 infection can trigger PCVAD development and that commercial vaccines are effective in protecting conventional pigs against emerging mPCV2 strains. PMID:24929119

Opriessnig, Tanja; Gerber, Priscilla F; Xiao, Chao-Ting; Halbur, Patrick G; Matzinger, Shannon R; Meng, Xiang-Jin

2014-07-23

259

Helicobacter pylori Induces miR-155 in T Cells in a cAMP-Foxp3-Dependent Manner  

PubMed Central

Amongst the most severe clinical outcomes of life-long infections with Helicobacter pylori is the development of peptic ulcers and gastric adenocarcinoma - diseases often associated with an increase of regulatory T cells. Understanding H. pylori-driven regulation of T cells is therefore of crucial clinical importance. Several studies have defined mammalian microRNAs as key regulators of the immune system and of carcinogenic processes. Hence, we aimed here to identify H. pylori-regulated miRNAs, mainly in human T cells. MicroRNA profiling of non-infected and infected human T cells revealed H. pylori infection triggers miR-155 expression in vitro and in vivo. By using single and double H. pylori mutants and the corresponding purified enzymes, the bacterial vacuolating toxin A (VacA) and ?-glutamyl transpeptidase (GGT) plus lipopolysaccharide (LPS) tested positive for their ability to regulate miR-155 and Foxp3 expression in human lymphocytes; the latter being considered as the master regulator and marker of regulatory T cells. RNAi-mediated knockdown (KD) of the Foxp3 transcription factor in T cells abolished miR-155 expression. Using adenylate cyclase inhibitors, the miR-155 induction cascade was shown to be dependent on the second messenger cyclic adenosine monophosphate (cAMP). Furthermore, we found that miR-155 directly targets the protein kinase A inhibitor ? (PKI?) mRNA in its 3?UTR, indicative of a positive feedback mechanism on the cAMP pathway. Taken together, our study describes, in the context of an H. pylori infection, a direct link between Foxp3 and miR-155 in human T cells and highlights the significance of cAMP in this miR-155 induction cascade.

Fassi Fehri, Lina; Koch, Manuel; Belogolova, Elena; Khalil, Hany; Bolz, Christian; Kalali, Behnam; Mollenkopf, Hans J.; Beigier-Bompadre, Macarena; Karlas, Alexander; Schneider, Thomas; Churin, Yuri; Gerhard, Markus; Meyer, Thomas F.

2010-01-01

260

Vacuoles of Candida yeast as a specialized niche for Helicobacter pylori  

PubMed Central

Helicobacter pylori (H. pylori) are resistant to hostile gastric environments and antibiotic therapy, reflecting the possibility that they are protected by an ecological niche, such as inside the vacuoles of human epithelial and immune cells. Candida yeast may also provide such an alternative niche, as fluorescently labeled H. pylori were observed as fast-moving and viable bacterium-like bodies inside the vacuoles of gastric, oral, vaginal and foodborne Candida yeasts. In addition, H. pylori-specific genes and proteins were detected in samples extracted from these yeasts. The H. pylori present within these yeasts produce peroxiredoxin and thiol peroxidase, providing the ability to detoxify oxygen metabolites formed in immune cells. Furthermore, these bacteria produce urease and VacA, two virulence determinants of H. pylori that influence phago-lysosome fusion and bacterial survival in macrophages. Microscopic observations of H. pylori cells in new generations of yeasts along with amplification of H. pylori-specific genes from consecutive generations indicate that new yeasts can inherit the intracellular H. pylori as part of their vacuolar content. Accordingly, it is proposed that yeast vacuoles serve as a sophisticated niche that protects H. pylori against the environmental stresses and provides essential nutrients, including ergosterol, for its growth and multiplication. This intracellular establishment inside the yeast vacuole likely occurred long ago, leading to the adaptation of H. pylori to persist in phagocytic cells. The presence of these bacteria within yeasts, including foodborne yeasts, along with the vertical transmission of yeasts from mother to neonate, provide explanations for the persistence and propagation of H. pylori in the human population. This Topic Highlight reviews and discusses recent evidence regarding the evolutionary adaptation of H. pylori to thrive in host cell vacuoles.

Siavoshi, Farideh; Saniee, Parastoo

2014-01-01

261

Abundâncias químicas de estrelas T Tauri fracas  

NASA Astrophysics Data System (ADS)

Apresentamos resultados do estudo de 44 estrelas pré-seqüência principal, para as quais buscamos realizar uma classificação espectroscópica e determinar parâmetros estelares e abundâncias químicas. A amostra foi escolhida da seguinte maneira : 21 objetos selecionados a partir de catálogos de objetos jovens, como o Pico dos Dias Survey e o Herbig Bell Catalogue, e 23 objetos selecionados a partir de contrapartidas ópticas de fontes de raios X detectadas pelo satélite ROSAT. Dentre 24 objetos previamente classificados como estrelas T Tauri Fracas, apenas 7 revelaram ser realmente pertencentes à essa classe, sendo os demais objetos T Tauri Clássicas ou estrelas evoluídas da pré-seqüência principal. Esse resultado demonstra que o critério mais utilizado para distinguir as T Tauri Clássicas das T Tauri Fracas, baseado na largura equivelente da emissão Ha, não é suficiente para determinar o estágio evolutivo desses objetos. Para o cálculo de parâmetros estelares e abundâncias, foram escolhidas as estrelas que apresentam características ideais para esse tipo de estudo, como ausência de velamento, baixa velocidade de rotação e espectros com razão sinal-ruído adequada. Os parâmetros estelares como temperatura efetiva e gravidade foram determinados através do equilíbrio de excitação e ionização das linhas de Ferro, e as abundâncias químicas foram calculadas utilizando o método de síntese espectral. Serão apresentados os parâmetros estelares e as abundâncias de Lítio para toda a amostra, e abundâncias de vários elementos quimicos para 7 estrelas estudadas em maior detalhe

Rojas, G. A.; Gregorio-Hetem, J.

2003-08-01

262

Mesosiderites: A Chronologic and Petrologic Synthesis  

NASA Astrophysics Data System (ADS)

Recent petrologic, chemical, and isotopic analyses of mesosiderite clasts and whole rocks allow construction of the evolutionary history of the mesosiderite parent body (MPB) as shown in the figure. I. Initial Melting ~4.56 Ga Ago. Numerous chronologic measurements indicate that initial melting of the MPB occurred shortly after accretion, at about the same time that the eucrites and angrites formed. For example, a zircon grain from a basaltic clast in Vaca Muerta yielded a Pb-Pb age of 4.563 Ga (Ireland and Wlotzka, 1992). The 4.56-Ga event on the MPB is probably responsible for forming the monogenic basaltic clasts that compositionally resemble typical eucrites (Rubin and Mittlefehldt, 1992). II. Crustal Remelting ~4.47 Ga Ago. Internal Sm-Nd isochron ages of 4.47 Ga have been determined for gabbroic pebble 12 from Vaca Muerta and a basaltic clast from Mt. Padbury (Stewart et al., 1991). Pebble 12 is one of many clasts in mesosiderites that are highly depleted in incompatible elements and probably represent remelted crustal rocks (Rubin and Mittlefehldt, 1992). Because variation of Fe/Mn with Fe/Mg in pyroxenes from these clasts follows a trend defined by FeO reduction from a melt (Mittlefehldt, 1990), and because the reducing agents (e.g., P) were likely to have been introduced during metal-silicate mixing, the age of pebble 12 indicates that metal-silicate mixing had to have occurred >=4.47 Ga ago. III. Localized Impact Melting 4.5-3.9 Ga Ago. Localized impact melting and metamorphism were widespread on the eucrite parent body as indicated by many ages that were partially or totally reset <4.56 Ga ago. Impact melt material is common in mesosiderites of all petrologic types, and ages between 4.5-3.9 Ga are preserved. Quench-textured pebble 5 from Vaca Muerta, which is likely to have formed from a localized impact melt of material resembling a cumulate eucrite (Rubin and Jerde, 1987), has an internal isochron age of 4.42 Ga (Stewart et al., 1992). The high temperature of these localized events places them before the 3.9-Ga event (below); however, because no extensive crustal remelting is evident, the metamorphism must have occurred after 4.47 Ga ago. The mesosiderite breccias were assembled during this phase of MPB history. IV. Collisional Disruption and Reassembly ~3.9 Ga Ago. Mesosiderites were degassed by a major thermal event ~3.9 Ga ago that heated the rocks to ~500 degrees C; this event may mark collisional disruption and gravitational reassembly of the MPB (Bogard et al., 1990). The surface breccias were deeply buried at this time and heated somewhat above the Fe-Ni solvus, resetting the metallographic cooling rates to ~1 degree C/Ma. This event may also account for some of the reported disturbances in the Rb- Sr, Sm-Nd, and Pb-Pb ages of a few mesosiderites. V. Impact Excavation and Ejection <<3.9 Ga Ago. Mesosiderites have cosmic ray exposure ages ranging from ~10-150 Ma, which represent the epoch when individual mesosiderites were excavated from the MPB or from a >=10-m-size MPB fragment. References: Bogard D.D., Garrison D.H., Jordan J.L. and Mittlefehldt D. (1990) Geochim. Cosmochim. Acta 54, 2549-2564. Ireland T.R. and Wlotzka F. (1992) Earth Planet. Sci. Lett. 109, 1-10. Mittlefehldt D.W. (1990) Geochim. Cosmochim. Acta 54, 1165-1173. Rubin A.E. and Jerde E.A. (1987) Earth Planet. Sci. Lett. 84, 1-14. Rubin A.E. and Mittlefehldt D.W. (1992) Geochim. Cosmochim. Acta 56, 827-840. Stewart B.W., Cheng Q.C., Papanastassiou D.A. and Wasserburg G.J. (1991) Lunar Planet. Sci. (abstract) 22, 1333. Stewart B.W., Papanastassiou D.A. and Wasserburg G.J. (1992) Lunar Planet. Sci. (abstract) 23, 1365.

Rubin, A. E.; Mittlefehldt, D. W.

1992-07-01

263

Moléculas orgánicas obtenidas en simulaciones experimentales del medio interestelar.  

NASA Astrophysics Data System (ADS)

Las nubes moleculares son regiones de formación de estrellas, con temperaturas cinéticas entre 10-50 K y densidades de 103-106 átomos cm-3. Su materia está formada por gas y polvo interestelar. Estas partículas de polvo están cubiertas por una fina capa de hielo, de unos 0.01 ?m, que contiene H2O y a menudo CO, CO2, CH3OH y NH3. El hielo es presumiblemente irradiado por fotones ultravioleta y rayos cósmicos en las zonas poco profundas de las nubes moleculares y las regiones circunestelares. En un sistema de vacío, P ˜ 10-7 mbar, simulamos la deposición de hielo a partir de 10 K y la irradiación ultravioleta por medio de una lámpara de descarga de hidrógeno activada con microondas. La evolución del hielo se observa por medio de un espectrómetro infrarrojo. De este modo es posible determinar la composición del hielo observado en el medio interestelar y predecir la presencia de moléculas aún no detectadas en el espacio, que han sido producto del procesamiento del hielo en nuestros experimentos. También es posible calentar el sistema hasta temperatura ambiente para sublimar el hielo depositado. Cuando el hielo ha sido previamente irradiado, se observa un residuo compuesto por moléculas orgánicas complejas, algunas prebióticas, como varios ácidos carboxílicos, aminas, amidas, ésteres y en menor proporción moléculas heterocíclicas y aminoácidos. Algunas de estas moléculas podrían detectarse en estado gaseoso por medio de observaciones milimétricas y de radio. También podrían estar presentes en el polvo cometario, cuyo análisis químico está planeado por las misiones Stardust y Rosetta. Mientras tanto, nuestro grupo está llevando a cabo el análisis de partículas de polvo interplanetario (IDPs), algunas de las cuales pueden ser de origen cometario. Al igual que ocurre con los productos obtenidos por irradiación del hielo en nuestros experimentos, algunas IDPs son ricas en material orgánico que contiene oxígeno.

Muñoz-Caro, Guillermo Manuel

264

Method for cutting steam heat losses during cyclic steam injection of wells. Second quarterly report  

SciTech Connect

The Midway-Sunset Field (CA) is the largest Heavy Oil field in California and steam injection methods have been successfully used for more than 30 years to produce the Heavy Oil from many of its unconsolidated sand reservoirs. In partnership with another DOE/ERIP grantee, our Company has acquired an 80 ac. lease in the SE part of this field, in order to demonstrate our respective technologies in the Monarch sand, of Miocene Age, which is one of the reservoirs targeted by the DOE Class 3 Oil Program. This reservoir contains a 13 API oil, which has a much higher market value, as a Refinery Feedstock, than the 5 to 8 API Vaca Tar, used only as road paving material. This makes it easier to justify the required investment in a vertical well equipped with two horizontal drainholes. The economic viability of such a project is likely to be enhanced if Congress approves the export to Japan of a portion of the 27 API (1% Sulfur) AK North Slope oil, which currently is landed in California in preference to lighter and sweeter Far East imported crudes. This is a major cause of the depressed prices for California Heavy Oil in local refineries, which have reduced the economic viability of all EOR methods, including steam injection, in California. Two proposals, for a Near-Term (3 y.) and for a Mid-Term (6 y.) project respectively, were jointly submitted to the DOE for Field Demonstration of the Partners` new technologies under the DOE Class 3 Oil Program. The previous design of a special casing joint for the Oxnard field well was reviewed and adapted to the use of existing Downhole Hardware components from three suppliers, instead of one. The cost of drilling and completion of a well equipped with two horizontal drainholes was re-evaluated for the conditions prevailing in the Midway Sunset field, which are more favorable than in the Oxnard field, leading to considerable reductions in drilling rig time and cost.

Not Available

1994-08-01

265

Helicobacter pylori infection affects gastric ulcer healing in Japanese monkeys.  

PubMed

Although peptic ulcer frequently recurs in the presence of Helicobacter pylori infection, the effects of H. pylori on ulcer healing have yet to be studied in detail. Using an animal model, we examined the effects of H. pylori infection on the healing of peptic ulcer in Japanese macaques. Forty-four Japanese macaques, aged 5 years, were randomly divided into two groups, an H. pylori-infected group and a control group, with 22 animals in each. A total of 10(9) colony forming units per ml of an H. pylori strain clinically isolated from patients positive for the cagA gene, the vacA gene, and vacuolizing toxin production, was inoculated into the stomachs of the monkeys to induce H. pylori-associated gastritis. The monkeys were examined by endoscopy, and then 0.1 ml of 10% ammonia solution was injected into the angulus to produce an active ulcer. Endoscopic observations was performed every week for 8 weeks. Acid-reducing drugs and other cytoprotective agents were not administered during the 8-week observation period. No difference in the healing of the ulcers was seen between the two groups from the first to the third week. However, a significant delay in healing was noted in the H. pylori-infected group from the fourth week on wards (P < 0.05). At the sixth week, the proportion of ulcers in the S2 stage (presence of a complete scar) was 0% in the H. pylori-infected group and 38% in the control group, again indicating that healing was significantly delayed in the H. pylori-infected group (P = 0.0187). By the eighth week, the proportion of ulcers in S2 stage had increased to 18% in the H. pylori-infected group and 67% in the control group (P = 0.0719). In Japanese macaques with persistent H. pylori infection in the stomach, the speed of repair of the ulcer surface was reduced, leading to delayed ulcer healing, compared with the controls. PMID:9840013

Okui, M; Fukuda, Y; Yamamoto, I; Shintani, S; Shimoyama, T

1998-01-01

266

In vitro effect of amoxicillin and clarithromycin on the 3' region of cagA gene in Helicobacter pylori isolates  

PubMed Central

AIM: To evaluate the in vitro effect of amoxicillin and clarithromycin on the cag pathogenicity island (cag PAI). METHODS: One hundred and forty-nine clinical isolates of Helicobacter pylori (H. pylori) cultured from gastric biopsies from 206 Colombian patients with dyspeptic symptoms from a high-risk area for gastric cancer were included as study material. Antimicrobial susceptibility was determined by the agar dilution method. Resistant isolates at baseline and in amoxicillin and clarithromycin serial dilutions were subjected to genotyping (cagA, vacA alleles s and m), Glu-Pro-Ile-Tyr-Ala (EPIYA) polymerase chain reaction and random amplified polymorphic DNA (RAPD). Images of the RAPD amplicons were analyzed by Gel-Pro Analyzer 4.5 program. Cluster analyses was done using SPSS 15.0 statistical package, where each of the fingerprint bands were denoted as variables. Dendrograms were designed by following Ward’s clustering method and the estimation of distances between each pair of H. pylori isolates was calculated with the squared Euclidean distance. RESULTS: Resistance rates were 4% for amoxicillin and 2.7% for clarithromycin with 2% double resistances. Genotyping evidenced a high prevalence of the genotype cagA-positive/vacA s1m1. The 3’ region of cagA gene was successfully amplified in 92.3% (12/13) of the baseline resistant isolates and in 60% (36/60) of the resistant isolates growing in antibiotic dilutions. Upon observing the distribution of the number of EPIYA repetitions in each dilution with respect to baseline isolates, it was found that in 61.5% (8/13) of the baseline isolates, a change in the number of EPIYA repetitions lowered antibiotic pressure. The gain and loss of EPIYA motifs resulted in a diversity of H. pylori subclones after bacterial adjustment to changing conditions product of antibiotic pressure. RAPD PCR evidenced the close clonal relationship between baseline isolates and isolates growing in antibiotic dilutions. CONCLUSION: Antibiotic pressure does not induce loss of the cag pathogenicity island, but it can lead - in most cases - to genetic rearrangements within the 3’ region cagA of the founding bacteria that can affect the level of tyrosine phosphorylation impacting on its cellular effects and lead to divergence of cagA-positive subclones.

Bustamante-Rengifo, Javier Andres; Matta, Andres Januer; Pazos, Alvaro; Bravo, Luis Eduardo

2013-01-01

267

Anisotropy of Magnetic Susceptibility: a petrofrabric tool for understanding mechanisms of fold and thrust belt evolution. Application in Malargüe FTB, Argentina  

NASA Astrophysics Data System (ADS)

In fold and thrust belts (FTB), sedimentary beds are folded and faulted but rocks do not always show evidence of strong internal deformation. Nevertheless, several studies have demonstrated that a weak internal deformation (layer parallel shortening) can be recorded at the matrix scale before any macroscopic deformation. The Anisotropy of Magnetic susceptibility (AMS) provides information about the preferred orientation of billions of magnetic minerals. It enables the definition of a magnetic fabric, which may be visualized as an ellipsoid with principal axes K1 ? K2 ? K3. Basic elements of a magnetic fabric are the magnetic foliation (K1-K2 plane) and the magnetic lineation (K1 axe), when they are statistically defined. Both are related to strain-controlled petrofrabric. The Neuquén Basin is a wide intracratonic sag basin with complex and polyphased/diachronic evolution. The Pacific subduction and south Atlantic opening were the mechanisms controlling the large scale geodynamic framework. By late Triassic times, continental scale extension initiated fault-related narrow rift depocenters which later evolved toward a sag basin from middle Jurassic to upper Cretaceous. At that time, the basin started to record the compressive stress regime from the Pacific subduction. Three pulses of compressive deformation (Cretaceous, Paleogene and Miocene) are recorded in this retro-arc foreland setting. Approximately 300 samples have been collected from 30 sites in terrigenous rocks located along three cross sections from foothills to uplifted foreland area in Malargüe FTB. We mainly sample Kimmeridgian red beds of the Tordillo formation, Tithonian shales from the Vaca Muerta Fm, and late cretaceous red beds of the Neuquén Group. AMS fabrics are used as a proxy to measure accumulated microscopic finite strain and compares it with mesoscale (fractures) and macroscale structures (faults, folds…). This multi-scaled approach helps in defining a kinematic scenario for Malargüe FTB evolution by classifying magnetic fabrics related either to (1) sedimentary processes or (2) pre-folding layer parallel shortening (LPS) or (3) syn-folding kinematics depending on folding mode. Propagation of deformation in this case is neither uniform nor gradual. Therefore Malargüe FTB cannot be defined as a classical critical wedge; On the contrary extensional inheritance exerts a strong influence in localization of compressive deformation (LPS).

Branellec, Matthieu; Callot, Jean Paul; Aubourg, Charles; Nivière, Bertrand; Ringenbach, Jean Claude

2013-04-01

268

Coastal Upwelling off Chile: Ocean Productivity and Surface Sediments  

NASA Astrophysics Data System (ADS)

The coastal upwelling system of the Peru-Chile Current belongs to the most productive regions in the world oceans. In spite of this fact only very little is known about the sediment distribution in its southern part off the coast of Chile. To increase the knowledge about this region a multi-parameter study of the surface sediment distribution at over 100 sampling sites along the Chilean continental slope between 23°S and 45°S has been carried out. Detailed analyses of sedimentary data (TOC, carbonate, and biogenic opal contents, delta 15N) reveal a close relation to environmental conditions in the region. Coastal upwelling along the Chilean coast, centered around main upwelling centers such as off Antofagasta (23°S), off Lengua de Vaca (30°S), off Valparaiso (33°S), and off Concepci¢n (35-38°S), sustains the high productivity observed in satellite pigment data and in sediment data. However, the highest pigment concentrations are found south of 40°S where prevailing onshore winds of the Southern Westerlies generally prevent coastal upwelling. There, also highest estimated accumulation rates of organic carbon and biogenic opal at the sea floor are found. Thus, the general pattern of a southward increase of surface water productivity known from satellite data is closely reflected in the organic carbon, biogenic opal and ?15N data, although the observation of highest productivity south of the upwelling area is surprising. Probably, this high productivity in the south can be attributed to the advection of (macro-) nutrients by the Antarctic Circumpolar Current, supplying so-called high nutrient-low chlorophyll (HNLC) waters to the Chilean margin. Impinging on the Chilean margin these waters can take up micronutrients such as iron from the strong riverine input and from benthic exchange processes. The combination of macro- and micro-nutrients in this area most likely results in the high productivity of the area between 40°S and 45°S. From there these fertile waters are transported to the north by the Peru-Chile Current. Although the nutrients are kept in the system by coastal upwelling processes on their way north, total productivity is decreasing as the nutrients are gradually consumed on their way north and taken out of the system by sedimentation.

Hebbeln, D.; Lamy, F.

2002-12-01

269

The belt of metagabbros of La Pampa: Lower Paleozoic back-arc magmatism in south-central Argentina  

NASA Astrophysics Data System (ADS)

Combined geological, geochronological, geochemical and geophysical studies have led to identification of a large (˜300 km long, ˜5 km wide) N-S trending belt of metagabbros in the province of La Pampa, south-central Argentina. This belt, though only poorly exposed in the localities of Valle Daza and Sierra de Lonco Vaca, stands out in the geophysical data (aeromagnetics and gravity). Modeling of the aeromagnetic data permits estimation of the geometry of the belt of metagabbros and surrounding rocks. The main rock type exposed is metagabbros with relict magmatic nucleii where layering is preserved. A counterclockwise P-T evolution affected these rocks, i.e., during the Middle Ordovician the protolith reached an initial granulite facies of metamorphism (M1), evolving to amphibolite facies (M2). During the Upper Devonian, a retrograde, greenschist facies metamorphism (M3) partially affected the metagabbros. The whole-rock Sm-Nd data suggest a juvenile source from a depleted mantle, with model ages ranging from 552 to 574 Ma, and positive Epsilon values of 6.51-6.82. A crystallization age of 480 Ma is based on geological considerations, i.e. geochronological data of the host rocks as well as comparisons with the Las Aguilas mafic-ultramafic belt of Sierra de San Luis (central Argentina). The geochemical studies indicate an enriched MORB and back-arc signature. The La Pampa metagabbros are interpreted to be originated as a result of the extension that took place in a back-arc setting coevally with the Famatinian magmatic arc (very poorly exposed in the western part of the study area). The extensional event was 'aborted' by the collision of the Cuyania terrane with Pampia-Gondwana in the Middle Ordovician, causing deformation and metamorphism throughout the arc-back-arc region. The similarities between the La Pampa metagabbros and the mafic-ultramafic Las Aguilas belt of the Sierra de San Luis are very conspicuous, for example, the age (Lower Paleozoic), geochemical signature and timing of metamorphism (dated at ca. 465 Ma in the study area), which allow definition of a single, mafic back-arc belt in central Argentina, from San Luis to La Pampa.

Chernicoff, Carlos J.; Zappettini, Eduardo O.; Villar, Luisa M.; Chemale, Farid, Jr.; Hernández, Laura

2009-12-01

270

Host genetic factors respond to pathogenic step-specific virulence factors of Helicobacter pylori in gastric carcinogenesis.  

PubMed

The interindividual differences in risk of Helicobacter pylori (H. pylori)-associated gastric cancer involve significant heterogeneities of both host genetics and H. pylori strains. Several recent studies proposed a distinct sequence for H. pylori exerting its virulence in the host stomach: (i) adhering to and colonizing the surface of gastric epithelial cells, (ii) evading and attenuating the host defense, and (iii) invading and damaging the gastric mucosa. This review focuses on several key issues that still need to be clarified, such as which virulence factors of H. pylori are involved in the three pathogenic steps, which host genes respond to the step-specific virulence factors, and whether and/or how the corresponding host genetic variations influence the risk of gastric carcinogenesis. Urease, BabA and SabA in the adhesion-step, PGN and LPS in the immune evasion-step, and CagA, VacA and Tip? in the mucosal damage-step were documented to play an important role in step-specific pathogenicity of H. pylori infection. There is evidence further supporting a role of potentially functional polymorphisms of host genes directly responding to these pathogenic step-specific virulence factors in the susceptibility of gastric carcinogenesis, especially for urease-interacting HLA class II genes, BabA-interacting MUC1, PGN-interacting NOD1, LPS-interacting TLR4, and CagA-interacting PTPN11 and CDH1. With the continuous improvement of understanding the genetic profile of H. pylori-associated gastric carcinogenesis, a person at increased risk for gastric cancer may benefit from several aspects of efforts: (i) prevent H. pylori infection with a vaccine targeting certain step-specific virulence factor; (ii) eradicate H. pylori infection by blocking step-specific psychopathological characteristics of virulence factors; and (iii) adjust host physiological function to resist the carcinogenic role of step-specific virulence factors or interrupt the cellular signal transduction of the interplay between H. pylori and host in each pathogenic step, especially for the subjects with precancerous lesions in the stomach. PMID:24076409

He, Caiyun; Chen, Moye; Liu, Jingwei; Yuan, Yuan

2014-01-01

271

Sm-Nd chronology and petrogenesis of mesosiderites  

NASA Astrophysics Data System (ADS)

We have obtained Sm-Nd data from four mesosiderite silicate clasts, including three clasts with a variety of textures from the Vaca Muerta type 1A mesosiderite and one gabbroic clast from the Mt. Padbury mesosiderite. The gabbroic Vaca Muerta Pebble 12 and basaltic Pebble 16 yield identical 147Sm- 143Nd ages of 4.48 ± 0.19 AE and 4.48 ± 0.09 AE, respectively, while the highly recrystallized Pebble 5 gives an age of 4.42 ± 0.02 AE; Mt. Padbury yields an age of 4.52 ± 0.04 AE. All clasts show a correlation of 142Nd /144Nd with 147Sm /144Nd , and provide unequivocal evidence for the presence of live 146Sm at the time of their formation. Calculated initial 146Sm /144Sm values range from 0.004 (Pebble 5) to 0.006 (Pebbles 12, 16, and Mt. Padbury) and are generally consistent with the 147Sm- 143Nd ages. However, discordance of whole-rock leach and residue data and some disagreement between 146Sm- 142Nd relative ages and 147Sm- 143Nd absolute ages indicate small but significant disturbances to the Sm-Nd systematics. The ranges of ages and initial 146Sm /144Sm and 143Nd /144Nd values suggest that each of these silicate clasts underwent a separate, protracted evolution on its parent body prior to mixing with metal. Textural and trace element criteria indicate that individual clasts from the same mesosiderite often had very different igneous sources and thermal histories prior to their incorporation in the meteorite. Pebble 12 is extremely LREE depleted, probably a result of several melt extraction events, whereas Pebbles 5 and 16 and Mt. Padbury have nearly chondritic Sm/Nd with bulk REE concentrations higher than chondrites by factors of 5 to 15. In general, the Sm-Nd systematics of mesosiderite silicates require formation of the silicates on a parent planet which underwent relatively early and extreme differentiation. Preservation of diverse, old ages and the presence of 146Sm imply that metal-silicate mixing did not seriously alter the Sm-Nd isotopic memories of these clasts. We present a model for metal-silicate mixing which combines the cooling history with isotopic reequilibration for the case of thermal blanketing. We show that the total amount of isotopic reequilibration in a sample can be related to the initial temperature, depth of burial, grain size, and diffusion parameters. Application of this model to the silicate clasts measured in this study indicates that if the metal and silicate were thermally equilibrated above the metal solidus temperature during mixing, then the clasts must have been buried no deeper than 1-10 m in regolith during the initial high-temperature cooling phase in order to prevent the Sm-Nd systems from being extensively reset. In order to reconcile these results with the slow cooling rates at lower temperatures determined from studies of exsolution in the metal phase, we infer that heat was transferred rapidly from hot metal to cold silicate material during initial metal-silicate mixing, and that the deeply buried portions of the mixture then cooled slowly after reaching thermal equilibrium at ~600-700°C. The data from this study point to the following history for the mesosiderite parent body: (1) differentiation of a silicate parent body within the first ~50 m.y. of solar system history to form diverse parent magmas; (2) emplacement of primitive and differentiated mafic magmas near the planetary surface, and extensive differentiation in the near surface environment; (3) formation and reworking of regolith breccias through impact gardening at the near surface of the body; (4) mixing of molten Fe-Ni metal with the regolith followed by rapid cooling 100-150 m.y. after the origin of the solar system; (5) slow cooling from temperatures of ~700°C to produce the observed nickel diffusion profiles in the iron phase; (6) mild impact metamorphism and brecciation to obtain the much younger K-Ar ages; and (7) recent collisions or perturbations sending mesosiderite fragments into Earth-crossing trajectories.

Stewart, Brian W.; Papanastassiou, D. A.; Wasserburg, G. J.

1994-08-01

272

Delineation of the High Enthalpy Reservoirs of the Sierra Nevada Volcanic Geothermal System, South-Central Chile  

NASA Astrophysics Data System (ADS)

Geothermal system associated with the Pleistocene-Holocene Sierra Nevada volcano (SNVGS) in the Araucanía Region of Chile has surface manifestations from the north-western flank of the volcano, up to Manzanar and Malalcahuello. Baños del Toro, located on the northwestern flank of the volcano, has numerous fumaroles and acid pools (acid sulfate waters, T=~90°C, pH=2.1, TDS=3080 mg/L); while Aguas de la Vaca, near the base of the volcano, has a bubbling spring (chloride-sulfate waters, T=~60°C, pH=7.0, TDS=950 mg/L). Five shallow (<120m) wells (2 at Manzanar and 3 at Malalcahuello) dug and drilled in the Cautín River Valley discharge alkaline (pH= 9-10) waters with relatively low TDS (130-210mg/L). The main heat source of the geothermal system is apparently the magmatic system of the Sierra Nevada volcano. Liquiñe-Ofqui Fault Zone (LOFZ) that transects the area forms excellent conduits for the flow of the geothermal waters. The geothermal reservoirs are hosted in the volcanic rocks interceded with glacial deposits over the North Patagonian Batholith that forms an impermeable barrier, and thus constitutes the lower boundary of the geothermal system and also controls the lateral flow of the fluids. An equilibrium temperature of ~210°C is derived from gas geothermometry (CO2/Ar-H2/Ar) of the discharges at Baños del Toro. Geothermal fluids from the upflow area on the northwestern flank of the volcano migrate northwards to the Cautín River Valley. The geothermal system has a high enthalpy reservoir(s) on the northwestern flank of the Sierra Nevada volcano and low-enthalpy reservoirs in the Cautín River Valley that have been tapped to form spas at Manzanar and Malalcahuello. While sub-vertical fractures of LOFZ facilitate the recharge of the system, lateral flow of the geothermal fluids is apparently controlled by lithology; Melipueclo Pluton in particular prevents the westward flow from the upflow zone, causing the flow only northwards to Malalcahuello and subsequently westward on meeting poorly permeable Guapitrío Member of the Cura-Mallín Formation. This change in the flow direction from northwestward up to Malalcahuello to westward towards Manzanar is supported by topographic and hydrographic conditions as well, besides available geological and geophysical data. SNVGS is perhaps the most promising geothermal system in the area, considering the presence of high enthalpy reservoir and stable heat source, ideal for its development as geothermal resource. Acknowledgments: Authors would like to acknowledge the funding for this work through the PBCT PDA-07 project of CONICYT and Geothermal Program (Cátedra de Geotermia) of the Ministry of Energy and Mining, Government of Chile.

Alam, M.; Muñoz, M.; Parada, M.

2011-12-01

273

Substrate-controlled ichnofacies along a marine sequence boundary: The Intra-Valanginian Discontinuity in central Neuquén Basin (Argentina)  

NASA Astrophysics Data System (ADS)

The Intra-Valanginian Discontinuity in the Neuquén Basin (Argentina) marks a dramatic sea-level fall within Lower Cretaceous strata, and can be mapped for tens of kilometers both along depositional strike and dip. In the proximal region of the lowstand configuration, the subaerial segment of the sequence boundary is demarcated by alluvial conglomerates (basal Mulichinco Formation) onto deep-marine black shales (Vaca Muerta Formation). In the distal marine realm, the time-equivalent marine sequence boundary separates black shales and marls beneath from shallow-marine carbonate deposits above. This paper documents and discusses substrate-controlled trace fossils demarcating the marine sequence boundary across more than 30 km in a proximal-distal transect in order to shed light onto processes affecting the sea-floor during the generation, biogenic modification, and preservation of this regionally extensive omission surface. The downdip expression of the marine sequence boundary is well-exposed across a 20-km long, strike-oriented outcrop. Everywhere in this region the discontinuity is demarcated by robust Thalassinoides with well-defined walls and circular cross-sections, suggesting that the marly substrate was relatively firm during excavation. The burrow system is filled with bioclasts of echinoids and bivalves not present in underlying strata, up to pebble-size intraclasts that were eroded from the underlying succession, and authigenic minerals (glauconite, phosphates). This trace-fossil suite illustrates the Glossifungites Ichnofacies. The updip expression of the marine sequence boundary in the study area was recorded in a cored well located about 20 km from the outcrops. As in the distal region, a first generation of passively filled Thalassinoides excavated into a firm marly substrate is attributed to the Glossifungites Ichnofacies. However, this suite is cross-cut at the top by Gastrochaenolites and other unidentified borings. Bored intraclasts also occur above the omission surface. This trace-fossil suite represents the Trypanites Ichnofacies. The Intra-Valanginian Discontinuity records a complex history after the onset of the dramatic sea-level fall. Extensive erosion and exhumation of previous sediments, as well as early cementation, combined to produce different types of substrates during the generation of the omission surface (firmgrounds and hardgrounds). Colonization of firm substrates probably started firstly in proximal regions, when relative sea-level was still falling. During early transgression, firmgrounds were occupied in distal regions and borers colonized the hardgrounds developed in proximal regions. Thus, the surface demarcates a composite surface, involving a sequence boundary plus a transgressive surface, draped in turn by a mixing of sediments suggesting siliciclastic starvation. The generation and preservation of the features associated with the Intra-Valanginian Discontinuity are thought to result from the combination of a ramp-type pre-existing morphology, coupled with a high-amplitude sea-level fall and a relatively deep-marine setting prior to the formation of the omission surface.

Schwarz, Ernesto; Buatois, Luis A.

2012-11-01

274

Zircons in Eucrites: Pristine and Disturbed U-Pb Systematics  

NASA Astrophysics Data System (ADS)

In our previous studies of HED zircons we have found that the zircon U-Pb systems have been undisturbed and consistent with a formation age of 4.56 Ga. Zi from the eucrites Padvarninkai [1], Stannern [2], and Yamato 791438 [3] all show concordant compositions and even the eucritic enclaves in the Vaca Muerta mesosiderite appear to be undisturbed [4]. We have analyzed zircons found in pol sections from another six eucrites, Bereba, Cachari, Jonzac, Juvinas, Millbillil and Pasamonte. In addition, a relatively large (~10 micrometers) baddeleyite was discovered in Pasamonte and gives us a chance to examine the systematics of this phase in comparison to zircon. The zircons in these meteorites are typically less than 10 micrometer and occur in close association with ilmenite and chromite. Zircons and baddeleyite were analyzed for U-Th-Pb isotopes and trace-element abundances with the SHRIMP ion microprobe. The analytical techniques for ion microprobe analysis are described [4]. Owing to the small size of the zircons, most of them were entirely consumed during the U-Pb analyses and REE patterns were not measured. In addition, the sm size of the grains meant that there was significant beam overlap onto the surrou chromite and ilmenite with the possibility that the U-Pb normalization could be affected. The zircons are fairly typical of meteoritic zircons with U concentrat around 50-100 ppm with a high value of 300 ppm in a Pasamonte zircon. REE are al the range previously observed for meteoritic zircon. The baddeleyite has ~60 ppm and, in contrast to the extreme heavy REE enriched zircon patterns, has a slight light REE ennched pattern (La 1800 x CI; Lu 800 x CI) with a large Eu depletion. All U-Pb analyses are either concordant or reverse discordant (i.e. they have excess radiogenic Pb). Three of the sections (Jonzac, Juvinas, Millbillillie) ha large surface Pb contributions, but their compositions were consistent with concordant 4.56 Ga U-Pb. Pasamonte zircon was also concordant at 4.56 Ga and Ber was concordant to slightly reverse discordant at 4.534 +- 0.016 Ga. Cachari, how is distinct in that it shows a mixing line between concordant 4.56 Ga and a radiogenic common Pb with a ^207Pb/^206Pb of ~0.4. The lowest apparent ^207Pb/^2 age is 4.20 Ga. Cachan also has a number of petrographic features associated wit deformation; in particular one of the zircons has been sheared with an offset th the center of the grain. It is possible that the U-Pb systematics are reflecting event, which has caused isotopic disturbance in the mesosiderites. The Pasamonte baddeleyite may also be slightly disturbed with a young ^207Pb/^206Pb age of ~4. Ga; as yet we have no standard to calibrate U-Pb ratios. References: [1] Bukovanska M. et al. (1991) Meteoritics, 26, 325. [2] Ireland T. R. and Bukovanska M. (1992) Meteoritics 27, 237. [3] Ireland T. R. et al. (1992) XXIII, 569-570. [4] Ireland T. R. and Wlotzka F. (1992) EPSL, 109, 1-10.

Bukovanska, M.; Ireland, T. R.

1993-07-01

275

Zircons from the Stannern Eucrite  

NASA Astrophysics Data System (ADS)

Zircons are becoming increasingly apparent in meteorites of the howardite-eucrite-diogenite association. The zircons generally occur as small (<=30 micrometers) inclusions closely associated with ilmenite and chromite. We have previously analyzed zircons from eucritic enclaves from Vaca Muerta [1], zircons from the brecciated eucrite Padvarninkai [2], and from the Yamato 791438 eucrite [3]. Here we report on our continued studies of meteoritic zircons with ion probe U-Th-Pb isotopic systematics and REE abundances of zircons from the Stannern eucrite. Eighteen zircons were identified and analyzed by electron probe in a polished section of the Stannern eucrite. An average composition is SiO2 31.78, TiO2 0.73, FeO 1.45, ZrO2 64.26, HfO2 1.04, total 99.26. The mean Zr/Hf ratio of 63 (range 21-129) is similar to the range observed in lunar zircons 30-60. Most of these zircons were not suitable for analysis (too small, proximity to cracks) and only four were analyzed for U-Th-Pb isotopes and trace-element abundances with the SHRIMP ion microprobe. All of these zircons occur in close association with ilmenite. The ilmenite grains range in size up to several hundred micrometers, but the zircons are at most only 20 micrometers in diameter. The analytical techniques for ion microprobe analysis are described in [1]. The U concentrations ranged from 30-80 ppm and the mean ^207Pb/^206Pb age of the four grains is 4550 +- 10 Ma (2 sigma); these values are very similar to the range in U concentrations (30-60 ppm) and the age (4553 +- 13 Ma) of the zircons analyzed from Padvarninkai [2]. The zircon age is compatible with the Sm-Nd age of Stannern (4.48 +- 0.07 Ga [4]) and the zircons have not been affected by the event(s) that disturbed the Rb-Sr system (3.1 +- 0.5 Ga [5]). The REE patterns (Fig. 1) are also very similar to the range shown in Padvarninkai. The LREE patterns are flat but the absolute abundances are different in the four grains ranging from chondritic to over 100 x chondritic. Europium is depleted in all zircons relative to the trend of the other REE. The HREE abundances are smoothly fractionated with overall absolute abundances that vary sympathetically with the overall LREE abundances. The similarity of the REE in zircons from Padvarninkai is noteworthy since the absolute abundances of REE in Stannern are 20 x CI compared with 10 x CI in Padvarninka. Therefore the zircon compositions do not appear to be controlled solely by the total REE inventory. References: [1] Ireland and Wlotzka (1992) EPSL 109, 1. [2] Bukovanska et al. (1991) Meteoritics 26, 325. [3] Ireland et al. (1992) Lunar Planet. Sci. XXIII, 569. [5] Birck and Allegre (1978) EPSL 39, 37. Figure 1, which in the hard copy appears here, shows Stannern REE.

Ireland, T. R.; Bukovanska, M.

1992-07-01

276

Mesosiderites: Young Meteorites from the Largest Sampled Asteroid?  

NASA Astrophysics Data System (ADS)

The 3.6-Gy ^39Ar-^40Ar age of mesosiderites has been interpreted in terms of a major impact around the time of major impacts on the Moon and the HED parent body [1;2]. We suggest instead that the young age of mesosiderites reflects lengthy primary cooling of the largest sampled asteroid; we calculate that its radius was 200-400 km. This conclusion is more consistent with the petrologic properties and our revised metallographic cooling rates of the mesosiderites. If correct, this would present us with a unique opportunity to calibrate the metallographic cooling rates. We have measured metallographic cooling rates of 5 mesosiderites (Vaca Muerta, Emery, Lowicz, Esterville, and Pinnaroo, see also [3]) using the revised phase-diagrams and diffusion constant of [4] and the local-bulk Ni technique of [5]. The metal structure indicates that the mesosiderites cooled slowly from at least 700 degrees C, where kamacite begins to precipitate, to below 320 degrees C, where tetrataenite forms. Cooling of the mesosiderites from 700 degrees C to below 300 degrees C in 900 My would require a cooling rate of more than 0.4 K/My. However, our preliminary results indicate metallographic cooling rates of approximately 0.05 K/My or almost an order of magnitude lower than the 0.4 K/My required to obtain Ar closure before 3.6 Gy ago. We find that the ^39Ar-^40Ar dates represent primary cooling for the following three reasons: 1) The metallographic cooling rates are the lowest known and--if taken at face value--inconsistent with cooling to Ar closure temperatures within 900 My. 2) Fresh shock features in the metal and silicates of mesosiderites are lacking but should be abundant if the parent body experienced a major impact 3.6 Gy ago. 3) The ^39Ar-^40Ar ages [1] are typically better defined than documented shock-ages of randomly sampled impact products since only small amounts of target material are heated sufficiently to remove Ar completely. Under the assumption that the Ar age represents primary cooling of the mesosiderites we have an independent measure of the cooling rate: 0.4 K/My. This would indicate that our revised mesosiderite cooling rates are too low by a factor of approximately 10. If, on the other hand, the Ar age represents a resetting of the Ar clock, then the cooling rate must have been even higher in order to obtain Ar closure prior to 3.6 Gy ago. A cooling rate of 0.4 K/My would require a parent body with a radius of 200 to 400 km. These radii are calculated assuming that the asteroid was covered with an insulating regolith with a thickness of between 600 and 0 m [6]. References: [1] Bogard D.D., Garrison D.H., Jordan J.L., and Mittlefehldt D. (1990) GCA, 54, 2549-2564 [2] Bogard D.D. and Garrison D.H. (1992) LPSC XXIII, 131-132. [3] Rasmussen K.L., Delaney J.S., and Prinz M. (1985) Meteoritics, 20, 738-739. [4] Saikumar V. and Goldstein J.I. (1988) GCA, 52, 715-726 [5] Rasmussen K.L. (1981) Icarus, 52, 564-576 [6] Haack H., Rasmussen, K.L., and Warren, P.H. (1990) JGR, 95, 5111-5124.

Haack, H.; Scott, E. R. D.; Rasmussen, K. L.

1992-07-01

277

Groundwater capture processes under a seasonal variation in natural recharge and discharge  

NASA Astrophysics Data System (ADS)

"Capture" is the increase in recharge and the decrease in discharge that occurs when pumping is imposed on an aquifer system that was in a previous state of approximate dynamic equilibrium. Regional groundwater models are usually used to calculate capture in a two-step procedure. A steady-state solution provides an initial-head configuration, a set of flows through the boundaries for the modeled region, and the initial basis for the capture calculation. The transient solutions provide the total change in flows through the boundaries. A difference between the transient and steady-state solutions renders the capture calculation. When seasonality is a modeling issue, the use of a single initial hydraulic head and a single set of boundary flows leads to miscalculations of capture. Instead, an initial condition for each season should be used. This approach may be accomplished by determining steady oscillatory solutions, which vary through the seasons but repeat from year to year. A regional groundwater model previously developed for a portion of the San Pedro River basin, Arizona, USA, is modified to illustrate the effect that different initial conditions have on transient solutions and on capture calculations. Résumé Les "prélèvements" sont constitués par l'augmentation de la recharge et par la diminution de l'écoulement qui se produit lorsqu'un pompage est imposéà un système aquifère qui était auparavant dans un état proche de l'équilibre dynamique. Les modèles régionaux de nappe sont en général utilisés pour calculer les prélèvements dans une procédure à deux étapes. Une solution en régime permanent donne la configuration piézométrique initiale, un jeu de conditions aux limites pour la région modélisée et les données de base pour le calcul des prélèvements. Les solutions transitoires donnent les modifications globales des conditions aux limites. Lorsque des variations saisonnières sont produites en sortie du modèle, le recours à une piézométrie initiale unique et à un seul jeu de données de conditions aux limites conduit à un mauvais calcul des prélèvements. Il faut alors utiliser une condition de recharge initiale pour chaque saison. Cette approche peut être réalisée en déterminant des solutions permanentes périodiques, variantes au cours des saisons, mais se répétant d'année en année. Un modèle de nappe régional, précédemment mis au point pour une partie du bassin de la rivière San Pedro (Arizona, États-Unis), a été modifié pour illustrer l'effet de conditions initiales différentes sur des solutions transitoires et sur le calcul des prélèvements. Resumen Se define como "captura" al aumento de recarga y descenso de descarga que tiene lugar cuando se impone un bombeo en un acuífero en estado de equilibrio dinámico. Se suelen utilizar modelos regionales de agua subterránea para calcular la captura en un procedimiento que consta de dos etapas. Una solución en régimen estacionario proporciona la distribución inicial de niveles piezométricos, los flujos a través de los contornos de la región modelada y el punto de partida para el cálculo de la captura. Las soluciones transitorias proporcionan los cambios en los flujos a través de los contornos. La diferencia entre las soluciones estacionaria y transitoria da el valor de la captura. Cuando los cambios estacionales son importantes, la utilización de un único estado inicial de niveles y de flujos en los contornos da lugar a errores en el cálculo de la captura. En este caso debe usarse una condición inicial para cada una de las estaciones. Esto se puede conseguir obteniendo soluciones periódicas estacionarias, que varíen a lo largo de las estaciones, pero que se repitan año a año. Un modelo regional desarrollado previamente para el estudio de una parte de la cuenca del Río San Pedro, en Arizona (EE.UU.) se modificó para ilustrar el efecto que las distintas condiciones iniciales tienen en el cálculo de la captura.

Maddock, Thomas, III.; Vionnet, Leticia Beatriz

278

Dinámica y crecimiento de los granos de polvo en la nebulosa protoplanetaria  

NASA Astrophysics Data System (ADS)

En el escenario estándar de la formación planetaria, los planetesimales (cuerpos de tamaño kilométrico) crecen a partir de granos de polvo, similares a los interestelares, embebidos en un disco gaseoso denominado nebulosa protoplanetaria. Durante esta etapa, los movimientos del gas pueden tener gran influencia en la dinámica y el crecimiento de los granos de polvo, dado que el flujo kepleriano del gas frena el movimiento de los mismos haciendo que caigan hacia el Sol, y la turbulencia inhibe la inestabilidad gravitacional de la capa de polvo. Aunque se acepta que los planetesimales fueron los elementos constituyentes de los planetas, todavía se desconoce cómo se produjo la formación de los mismos. Por esta razón, en los estudios más recientes, existe un renovado interés por comprender mejor la evolución de la capa de polvo inmersa en el disco gaseoso de la Nebulosa. El gas que fluye en el disco puede engendrar estructuras carentes de simetría axial, como por ejemplo ondas espirales y vórtices, a partir de gran variedad de mecanismos de excitación e inestabilidad. En 1995, Barge y Sommeria pusieron de manifiesto que la existencia de vórtices gaseosos persistentes en la nebulosa solar tendría importantes consecuencias sobre la formación de los planetesimales y el posterior crecimiento de los planetas gigantes. La investigación desarrollada en esta Tesis analiza la relación entre el polvo y el gas debida al acoplamiento por fricción dinámica entre ambos; en concreto, se estudia el efecto del flujo medio del gas sobre la dinámica de las partículas de polvo. El primer objetivo es investigar en profundidad los procesos de captura y crecimiento de los granos de polvo dentro de un vórtice y su posible relevancia en cuanto a la formación de los planetesimales. El segundo objetivo es la exploración de los efectos de ondas espirales propagándose en el disco gaseoso sobre la dinámica y el crecimiento de las partículas. La presencia de líneas de corriente no circulares perturba significativamente el movimiento de las partículas alrededor del Sol e incrementa su vida media en la Nebulosa. El flujo medio del gas se modela de forma simple, analizándose la dinámica y el crecimiento de las partículas mediante simulaciones numéricas. Al incrementarse la vida media y la densidad superficial de las partículas sólidas, los mecanismos de confinamiento derivados de la presencia de vórtices y ondas espirales actuan sobre el material sólido de la Nebulosa (mediante agregación colisional o inestabilidades gravitacionales) de manera mucho más eficiente que la previamente considerada. Esto ofrece nuevas posibilidades para la formación de planetesimales y núcleos de planetas gigantes, y puede explicar la formación rápida de planetas extrasolares gigantes. Además, esta Tesis analiza la respuesta de las partículas, en un disco protoplanetario con un radio de 100 UA en torno a una estrella de tipo solar, al campo gravitatorio derivado de la presencia de dos estrellas compañeras ligadas en una órbita relativamente elongada (300-1600 UA). Para llevar a cabo este análisis, se han realizado una serie de simulaciones numéricas de configuraciones jerárquicas coplanares utilizando un programa FORTRAN que integra directamente las ecuaciones del movimiento con el objeto de modelar la presencia de las fuerzas gravitacionales y viscosas. El disco protoplanetario masivo se encuentra en torno a una de las componentes de la binaria. La evolución temporal del subdisco de polvo depende directamente de la naturaleza (directa o retrógrada) de la revolución relativa de la compañera estelar, y de la temperatura y la masa del disco circunestelar.

de La Fuente Marcos, Carlos

2001-06-01

279

Hydrodynamic model of cells for designing systems of urban groundwater drainage  

NASA Astrophysics Data System (ADS)

An improved mathematical hydrodynamic quasi-two-dimensional model of cells, CELSUB3, is presented for simulating drainage systems that consist of pumping well fields or subsurface drains. The CELSUB3 model is composed of an assemblage of algorithms that have been developed and tested previously and that simulate saturated flow in porous media, closed conduit flow, and flow through pumping stations. A new type of link between aquifer cells and drainage conduits is proposed. This link is verified in simple problems with well known analytical solutions. The correlation between results from analytical and mathematical solutions was considered satisfactory in all cases. To simulate more complex situations, the new proposed version, CELSUB3, was applied in a project designed to control the water-table level within a sewer system in Chañar Ladeado Town, Santa Fe Province, Argentina. Alternative drainage designs, which were evaluated under conditions of dynamic recharge caused by rainfall in a critical year (wettest year for the period of record) and a typical year, are briefly described. After analyzing ten alternative designs, the best technical-economic solution is a subsurface drainage system of closed conduits with pumping stations and evacuation channels. Résumé. Un modèle hydrodynamique perfectionné de cellules en quasi 2D, CELSUB3, est présenté dans le but de simuler des systèmes de drainage qui consistent en des champs de puits de pompage ou de drains souterrains. Le modèle CELSUB3 est composé d'un assemblage d'algorithmes développés et testés précédemment et qui simulent des écoulements en milieu poreux saturé, en conduites et dans des stations de pompage. Un nouveau type de lien entre des cellules d'aquifères et des drains est proposé. Ce lien est vérifié dans des problèmes simples dont les solutions analytiques sont bien connues. La corrélation entre les résultats des solutions analytiques et des solutions mathématiques a été considérée comme satisfaisante dans tous les cas. Afin de simuler des situations plus complexes, la nouvelle version proposée, CELSUB3, a été mise en œuvre dans un projet destiné à contrôler le niveau de la nappe à l'intérieur d'un système d'égouts, dans la ville de Chaar Ladeado (province de Santa Fe, Argentine). Différentes organisations du projet de drainage, qui ont été testées pour des conditions de recharge dynamique causées par la pluie au cours d'une année critique (la plus humide de la chronique disponible) et une année typique, sont brièvement décrites. Après analyse de dix organisations différentes, la meilleure solution technico-économique retenue est un système de drainage souterrain de conduites avec des stations de pompage et des canaux d'évacuation. Resumen. Se presenta un modelo matemático hidrodinámico cuasi-bidimensional de celdas, CELSUB3, apto para la simulación integral de sistemas de drenaje subterráneo basados en campos de bombeo o drenes subsuperficiales. El modelo de simulación presenta un ensamble de algoritmos, previamente desarrollados y testeados, que representan al escurrimiento a través del medio poroso saturado, escurrimiento en conducciones cerradas, estaciones de bombeo, etc. En la estructura del modelo se propone un nuevo tipo de vinculación entre celdas acuíferas y conductos de drenaje, la cual es verificada en problemas simples con solución analítica conocida arrojando, en todos los casos, resultados satisfactorios. Abordando situaciones más complejas, la nueva versión propuesta fue aplicada en un proyecto de control de niveles freáticos que acompaña un sistema de conductos cloacales, en la localidad de Chañar Ladeado, Santa Fe, Argentina. Se describen las alternativas de drenaje consideradas las cuales fueron evaluadas bajo recargas dinámicas provocadas por años críticamente lluviosos y en situaciones típicas. Los resultados derivados permitieron definir, tras analizar una decena de proyectos alternativos, la mejor solución técnico-económica consistente en un sistema de drenes subte

Zimmermann, Eric; Riccardi, Gerardo

2000-08-01