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1

Prevalence of Helicobacter pylori vacA different genotypes in Isfahan, Iran  

PubMed Central

Background: It is believed that the Helicobacter pylori (H. pylori) vacA gene, as a major virulence determinant (One of the major virulence determinant, not major), may be a risk factor for the development of gastroduodenal diseases. The frequency of vacA genotypes varies in different human populations. This study evaluated the prevalence of vacA alleles/genotypes among dyspeptic patients in Isfahan. Materials and Methods: One-hundred H. pylori-positive adult patients were examined in this study. After culture of gastric biopsies and DNA extraction from individual H. pylori isolates, the (all H. pylori strains harbor vacA alleles, please replace “presence” with “genotypes”) of the vacA s and m alleles were determined using polymerase chain reaction (PCR). Results: There were four vacA mosaicisms, including 28 for s1a/m1 (28%), 23 for s1b/m1 (23%), 26 for s1a/m2 (26%) and 23 for s1b/m2 (23%). The s2 allele was not found. The predominant vacA genotype in patients with non-ulcer dyspepsia and duodenal ulcer was s1a/m2, whereas in patients with adenocarcinoma was s1a/m1. Conclusion: The results showed there was no significant correlation between different genotypes of the vacA and the clinical outcomes and appears to vacA genotypes were not useful determinants for gastrointestinal diseases in our area. PMID:24627856

Havaei, S. Asghar; Mohajeri, Parviz; Khashei, Reza; Salehi, Rasoul; Tavakoli, Hamid

2014-01-01

2

Protein-tyrosine phosphatase alpha, RPTP alpha, is a Helicobacter pylori VacA receptor.  

PubMed

Helicobacter pylori vacuolating cytotoxin, VacA, induces vacuolation, mitochondrial damage, cytochrome c release, and apoptosis of gastric epithelial cells. To detect gastric proteins that serve as VacA receptors, we used VacA co-immunoprecipitation techniques following biotinylation of the cell surface and identified p250, a receptor-like protein-tyrosine phosphatase beta (RPTP beta) as a VacA-binding protein (Yahiro, K., Niidome, T., Kimura, M., Hatakeyama, T., Aoyagi, H., Kurazono, H., Imagawa, K., Wada, A., Moss, J., and Hirayama, T. (1999) J. Biol. Chem. 274, 36693-36699). VacA causes vacuolation of G401 cells, a human kidney tumor cell line, although they do not express RPTP beta. By co-immunoprecipitation with VacA, we identified p140 as a potential receptor in those cells. p140 purified by chromatography on a peanut agglutinin affinity matrix contained internal amino acid sequences of RGEENTDYVNASFIDGYRQK and AEGILDVFQTVK, which are identical to those in RPTP alpha. The peptide mass fingerprinting of p140 by time of flight-MS analysis also supported this identification. Treatment of G401 cells with RPTP alpha-morpholino antisense oligonucleotide before exposure to toxin inhibited vacuolation. These data suggest that RPTP alpha acts as a receptor for VacA in G401 cells. Thus, two receptor tyrosine phosphatases, RPTP alpha and RPTP beta, serve as VacA receptors. PMID:12626515

Yahiro, Kinnosuke; Wada, Akihiro; Nakayama, Masaaki; Kimura, Takahiro; Ogushi, Ken-ichi; Niidome, Takuro; Aoyagi, Haruhiko; Yoshino, Ken-ichi; Yonezawa, Kazuyoshi; Moss, Joel; Hirayama, Toshiya

2003-05-23

3

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. PMID:18497859

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

2008-01-01

4

Effect of Helicobacter pylori VacA on gene expression of gastric cancer cells  

PubMed Central

AIM: To determine the effect of Helicobacter pylori VacA on gene expression of gastric cancer cells. METHODS: Gene expression profile of a gastric cancer cell line, SGC7901, after challenged by VacA+ and VacA- H pylori broth culture supernatants (BCS), was detected by the cDNA microarray technique. Cytoskeleton changes of SGC7901 and HeLa cells were observed through high-resolution laser scanning confocal microscopy. RESULTS: A total of 16000 cDNA clones were detected. The percentage of genes with heterogeneous expression in SGC7901 cells challenged by VacA+ BCS reached 5%, compared with that challenged by VacA- BCS. There were 865 genes/EST with 2-fold differential expression levels and 198 genes/EST with 3-fold differential expression levels. Most of these genes were involved in vital cell events including signal transduction, regulation of gene expression, cytoskeleton, apoptosis, stress response and inflammation, cell cycle and tumor development. Cells co-cultured with VacA+ BCS showed collapsed and disrupted microtubular cytoarchitecture. CONCLUSION: VacA+ BCS can disrupt cytoskeletal architecture, likely through affecting the expression of cytoskeleton-associated genes, directly induce the expression of tumor promoter-related genes and inhibit the expression of tumor suppressor genes, thus favoring the development of tumors. VacA+ BCS can also alter the expression of inflammation and stress response genes. This suggests that VacA may play an important role in the pathogenicity of H pylori. PMID:15609407

Wang, Hong-Tao; Li, Zhen-Hong; Yuan, Jian-Ping; Zhao, Wei; Shi, Xiao-Dong; Tong, Shan-Qing; Guo, Xiao-Kui

2005-01-01

5

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

6

A Novel Method for Genotyping the Helicobacter pylori vacA Intermediate Region Directly in Gastric Biopsy Specimens  

PubMed Central

The present report describes a novel method for genotyping the virulence-associated vacA intermediate (i) region of Helicobacter pylori in archive material. vacA i-region genotypes as determined by the novel method were completely concordant with those of sequence analysis and with those of functional vacuolation activity. The method was further validated directly in gastric biopsy specimens of 386 H. pylori-positive cases, and effective characterization of the vacA i region was obtained in 191 of 192 (99.5%) frozen and in 186 of 194 (95.9%) formalin-fixed paraffin-embedded gastric biopsy specimens, respectively. The genotyping method was next used to address the relationship between the vacA genotypes and the cagA status. The vacA i1 genotype was associated with vacA s1 (where s indicates signal region), vacA m1 (where m indicates middle region), and cagA-positive genotypes (P < 0.0001), while the vacA i2 genotype was closely related with vacA s2, vacA m2, and cagA-negative genotypes (P < 0.0001). The relationship between H. pylori vacA i-region genotypes and gastric disease development was subsequently evaluated in the Portuguese population. Patients infected with vacA i1 strains showed an increased risk for gastric atrophy and for gastric carcinoma, with odds ratios of 8.0 (95% confidence interval [CI], 2.3 to 27) and of 22 (95% CI, 7.9 to 63), respectively. Taken together, the results show that this novel H. pylori vacA i-region genotyping method can be applied directly to archive material, providing a fast evaluation of strain virulence determinants without the need of culture. The results further emphasize that the characterization of the vacA i region may be useful to identify patients at higher risk of gastric carcinoma development. PMID:23035185

Ferreira, Rui M.; Machado, Jose C.; Letley, Darren; Atherton, John C.; Pardo, Maria L.; Gonzalez, Carlos A.; Carneiro, Fatima

2012-01-01

7

Remodeling the host environment: modulation of the gastric epithelium by the Helicobacter pylori vacuolating toxin (VacA)  

PubMed Central

Virulence mechanisms underlying Helicobacter pylori persistence and disease remain poorly understood, in part, because the factors underlying disease risk are multifactorial and complex. Among the bacterial factors that contribute to the cumulative pathophysiology associated with H. pylori infections, the vacuolating cytotoxin (VacA) is one of the most important. Analogous to a number of H. pylori genes, the vacA gene exhibits allelic mosaicism, and human epidemiological studies have revealed that several families of toxin alleles are predictive of more severe disease. Animal model studies suggest that VacA may contribute to pathogenesis in several ways. VacA functions as an intracellular-acting protein exotoxin. However, VacA does not fit the current prototype of AB intracellular-acting bacterial toxins, which elaborate modulatory effects through the action of an enzymatic domain translocated inside host cells. Rather, VacA may represent an alternative prototype for AB intracellular acting toxins that modulate cellular homeostasis by forming ion-conducting intracellular membrane channels. Although VacA seems to form channels in several different membranes, one of the most important target sites is the mitochondrial inner membrane. VacA apparently take advantage of an unusual intracellular trafficking pathway to mitochondria, where the toxin is imported and depolarizes the inner membrane to disrupt mitochondrial dynamics and cellular energy homeostasis as a mechanism for engaging the apoptotic machinery within host cells. VacA remodeling of the gastric environment appears to be fine-tuned through the action of the Type IV effector protein CagA which, in part, limits the cytotoxic effects of VacA in cells colonized by H. pylori. PMID:22919629

Kim, Ik-Jung; Blanke, Steven R.

2012-01-01

8

Association between vacA genotypes and the risk of duodenal ulcer: a meta-analysis.  

PubMed

Epidemiological studies have reported the relationship between vacuolating cytotoxin A (vacA) s-/m- region genotypes and duodenal ulcer (DU), but the results remained inconclusive. We performed the present meta-analysis to investigate a more authentic association between vacA s-/m- region genotypes and DU. Literature search was performed by searching Embase, PubMed and ISI Web of Science databases as well as checking references from identified articles, reviews and the abstracts presented at related scientific societies meetings. The association was assessed by combined odds ratio (OR) with 95 % confidence interval (CI). A total of 42 studies were included in our final meta-analysis. The combined ORs (95 % CIs) showed that vacA s1 (OR = 2.96, 95 % CI = 2.34-3.75), m1 (OR = 1.46, 95 % CI = 1.05-2.04) and s1m1 (OR = 1.89, 95 % CI = 1.47-2.42) were associated with increased DU risk significantly in the overall studied population. Subgroup analyses by ethnicity showed that vacA s1 increased the risk of DU in Asian countries (OR = 1.92, 95 % CI = 1.30-2.83), European countries (OR = 3.58, 95 % CI = 2.13-6.03) and Latin American countries (OR = 4.20, 95 % CI = 2.21-7.98); vacA m1 increased the risk of DU in Latin American countries (OR = 2.98, 95 % CI = 1.59-5.56); vacA s1m1 increased the risk of DU in Asian countries (OR = 2.04, 95 % CI = 1.12-3.73) and Latin American countries (OR = 2.05, 95 % CI = 1.20-3.48); vacA s2m1 increased the risk of DU in Latin American countries (OR = 2.30, 95 % CI = 1.17-4.50). The data suggest that genotype testing of vacA s- and m- region will be useful in screening susceptible individuals for DU development. PMID:25063579

Zhang, Bei-Bei; Li, Yong; Liu, Xue-Qiang; Wang, Pei-Jian; Yang, Bo; Bian, Dong-Lin

2014-11-01

9

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-López, Luis R.

2004-01-01

10

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

11

cagA and vacA in strains of Helicobacter pylori from ulcer and non-ulcerative dyspepsia patients  

Microsoft Academic Search

BACKGROUND: The cytotoxin associated gene A (cagA), and the vacuolating cytotoxin gene A (vacA) of Helicobacter pylori have been associated to phenotypic characteristics of virulence. The objectives of this study were to detect the presence of cagA and to characterize the allelic variants of vacA in 63 strains of H. pylori isolated from colonized individuals with different clinical outcomes. METHODS:

Gustavo Faundez; Miriam Troncoso; Guillermo Figueroa

2002-01-01

12

The association of vacA genotype and Helicobacter pylori-related disease in Latin American and African populations  

PubMed Central

In the populations of Western countries, particular genotypes of the vacuolating cytotoxin gene, vacA (vacA s, signal region variants; vacA m, middle region variants) of Helicobacter pylori are believed to be risk factors for the development of peptic ulcers and gastric cancer. However, it was unclear whether these vacA gene variants are associated with the development of gastrointestinal diseases in developing nations. The relationship between vacA genotypes and H. pylori-related disease development in Latin American and African populations was investigated using meta-analysis of 2612 patients from Latin America (2285 strains) and 520 patients from Africa (434 strains). The frequencies of vacA s and m genotypes differed between strains from Latin America (77.2% for s1 and 68.1% for m1) and Africa (83.9% for s1 and 56.7% for m1). Latin American strains with s1 and m1 genotypes increased the risk of gastric cancer (OR 4.17, 95% CI 2.49–6.98 for s1, and 3.59, 2.27–5.68 for m1) and peptic ulcers (e.g. 1.73, 1.37–2.20 for s1). African strains with the s1 or m1 genotypes also increased the risk of peptic ulcers (8.69, 1.16–64.75 for s1) and gastric cancer (10.18, 2.36–43.84 for m1). The cagA-positive genotype frequently coincided with s1 and m1 genotypes in both populations. Overall, the vacA s and m genotypes were related to gastric cancer and peptic ulcer development and might be useful markers of risk factors for gastrointestinal disease, especially in Latin America. Further studies will be required to evaluate the effects of vacA genotypes in African populations because of the small sample number currently available. PMID:19392900

Sugimoto, M.; Yamaoka, Y.

2011-01-01

13

vacA Genotypes of Helicobacter pylori in Relation to cagA Status and Clinical Outcomes in Iranian Populations  

PubMed Central

SUMMARY 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, Leila; Dabiri, Hossein; Baghaei, Kaveh; Yamaoka, Yoshio; Zojaji, Homayon; Haghazali, Mehrdad; Molaei, Mahsa; Zali, Mohammad Reza

2013-01-01

14

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

15

A Role for the Vacuolating Cytotoxin, VacA, in Colonization and Helicobacter pylori-Induced Metaplasia in the Stomach  

PubMed Central

Carriage of Helicobacter pylori strains producing more active (s1/i1) forms of VacA is strongly associated with gastric adenocarcinoma. To our knowledge, we are the first to determine effects of different polymorphic forms of VacA on inflammation and metaplasia in the mouse stomach. Bacteria producing the less active s2/i2 form of VacA colonized mice more efficiently than mutants null for VacA or producing more active forms of it, providing the first evidence of a positive role for the minimally active s2/i2 toxin. Strains producing more active toxin forms induced more severe and extensive metaplasia and inflammation in the mouse stomach than strains producing weakly active (s2/i2) toxin. We also examined the association in humans, controlling for cagPAI status. In human gastric biopsy specimens, the vacA i1 allele was strongly associated with precancerous intestinal metaplasia, with almost complete absence of intestinal metaplasia in subjects infected with i2-type strains, even in a vacA s1, cagA+ background. PMID:24625807

Winter, Jody A.; Letley, Darren P.; Cook, Katherine W.; Rhead, Joanne L.; Zaitoun, Abed A. M.; Ingram, Richard J. M.; Amilon, Karin R.; Croxall, Nicola J.; Kaye, Phillip V.; Robinson, Karen; Atherton, John C.

2014-01-01

16

The recurrence interval of forest fires in Cabeço da Vaca (Cabreira Mountain--northwest of Portugal).  

PubMed

The recurrence of forest fires is degrading an important part of the Portuguese natural heritage namely its forest and soils. In this paper we present the case study of Cabeço da Vaca (Cabreira Mountain-northwest Portugal), where in recent decades, particularly in the 70s, there was a significant increase in the number of forest fires and in the areas scorched annually. There is thus a turning point between a period when fire was an integral part of the ecosystems and when fire has become a serious threat to woodland management and development (Bento Gonçalves, 2006). Starting with a thorough characterization of forest fires and based on the mapping of scorched areas between 1990 and 2006, we have proceeded to identify the annual pattern of maximum recurrence and the definition of the return interval in Cabeço da Vaca, producing thus a valuable document to support management and forestry development in general. PMID:20576260

Ferreira Leite, Flora; Bento Gonçalves, António; Vieira, António

2011-02-01

17

Role of deletion located between the intermediate and middle regions of the Helicobacter pylori vacA gene in cases of gastroduodenal diseases.  

PubMed

The vacuolating cytotoxin gene of Helicobacter pylori, vacA, induces cytoplasmic vacuolation in gastric epithelial cells. Recently, the vacA intermediate (i) region, which is located between the signal (s) and middle (m) regions, was identified as a third polymorphic determinant of vacA activity. In vacA, there are approximately 81-bp deletions between the vacA i and m regions (denoted the d region). The aim was to clarify the roles of the vacA d region in relation to H. pylori-related diseases and histopathological gastric mucosal changes. We assessed the vacA signal s-, m-, i-, and d-region genotypes and cagA status in H. pylori isolates recovered from Western countries (n = 266) and East Asian countries (n = 244) by PCR. In East Asian countries, there were no relationships between the vacA genotypes and the clinical outcomes and histopathological changes. In Western countries, strains with the vacA s1, m1, i1, or d1 (no deletion) genotype significantly increased the risk for the development of gastric cancer compared with the risk from strains with the s2, m2, i2, or d2 genotype (adjusted odd ratios, 3.17 [95% confidence interval {CI}, 1.07 to 9.45] for s1, 10.65 [95% CI, 3.36 to 31.35] for m1, 8.57 [95% CI, 2.85 to 25.81] for i1, and 8.04 [95% CI, 2.67 to 24.16] for d1). The highly virulent vacA genotypes significantly enhanced neutrophil infiltration and gastric atrophy in univariant analysis, whereas only the vacA d-region genotype was significantly associated with neutrophil infiltration and gastric atrophy in both the antrum and the corpus by multiple linear regression analysis. The presence of the vacA d1 genotype in H. pylori strains could be an improved predictor of histological inflammation and the potential for atrophy compared with the presence of the vacA s-, m-, and i-region genotypes in Western countries. PMID:19726606

Ogiwara, Hiroaki; Sugimoto, Mitsushige; Ohno, Tomoyuki; Vilaichone, Ratha-Korn; Mahachai, Varocha; Graham, David Y; Yamaoka, Yoshio

2009-11-01

18

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. PMID:19551413

Sugimoto, M.; Zali, M. R.

2011-01-01

19

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. PMID:21569518

2011-01-01

20

Characterization of Helicobacter pylori cagA and vacA Genotypes among Alaskans and Their Correlation with Clinical Disease?  

PubMed Central

Helicobacter pylori infection is common in Alaska. The development of severe H. pylori disease is partially determined by the virulence of the infecting strain. Here we present vacA and cagA genotype data for H. pylori strains isolated from Alaskans and their correlation with clinical disease. We enrolled patients scheduled for esophagogastroduodenoscopy and positive for H. pylori infection. Gastric biopsy specimens from the stomach antrum and fundus were cultured. We performed PCR analysis of the H. pylori vacA gene and for the presence of the cagA gene and cagA empty site. We genotyped 515 H. pylori samples from 220 Native and 66 non-Native Alaskans. We detected the cagA gene in 242/286 (85%) persons; of 222 strains that could be subtyped, 95% (212) were non-Asian cagA and 3% (6) were East Asian cagA. After removing mixed infections (n = 17), 83% of H. pylori strains had either the vacA s1m1 (120/269) or s2m2 (103/269) genotype. Sixty-six percent (68/103) of H. pylori strains with the vacA s2m2 genotype also contained the cagA gene. Infection with an H. pylori strain having the cagA gene or vacA s1m1 genotype (compared with s1m2 and s2m2) was associated with a decreased risk of esophagitis (P = 0.003 and 0.0003, respectively). Infection with an H. pylori strain having the vacA s1m1 genotype (compared with s1m2 and s2m2) was associated with an increased risk of peptic ulcer disease (PUD) (P = 0.003). The majority of H. pylori strains in this study carried the non-Asian cagA gene and either the vacA s1m1 or s2m2 genotype. A majority of H. pylori strains with the vacA s2m2 genotype also contained the cagA gene. There was an association of H. pylori genotype with esophagitis and PUD. PMID:21752979

Miernyk, Karen; Morris, Julie; Bruden, Dana; McMahon, Brian; Hurlburt, Debby; Sacco, Frank; Parkinson, Alan; Hennessy, Thomas; Bruce, Michael

2011-01-01

21

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. PMID:24800016

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

2013-01-01

22

The Cell-Specific Phenotype of the Polymorphic vacA Midregion Is Independent of the Appearance of the Cell Surface Receptor Protein Tyrosine Phosphatase  

Microsoft Academic Search

There are two alleles, m1 and m2, of the midregion of the vacuolating cytotoxin gene (vacA )o fHelicobacter pylori which code for toxins with different cell specificities. Here we describe the construction of five chimeric strains in which regions of vacA were exchanged between the two genotypes. By analyzing the toxicity of these strains for HeLa and RK13 cells we

David A. G. Skibinski; Christophe Genisset; Silvia Barone; John L. Telford

2006-01-01

23

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

24

Helicobacter pylori cagA, iceA and vacA genotypes in patients with gastric cancer in Taiwan  

Microsoft Academic Search

AIM: Helicobacter pylori (H pylori ) has been linked to chronic gastritis, peptic ulcer, gastric cancer and MALT-lymphoma. The link of genotypes of H pylori to gastric cancer remains controversial. The aim of this study was to investigate the H pylori vacA alleles, cagA and iceA in patients with gastric cancer in Taiwan. METHODS: Patients with gastric cancer, peptic ulcer

Hwai-Jeng Lin; Chin-Lin Perng; Wen-Ching Lo; Chew-Wun Wu; Guan-Ying Tseng; Anna Fen-Yau Li; I-Chen Sun; Yueh-Hsing Ou

25

Role of Helicobacter pylori cagA EPIYA motif and vacA genotypes for the development of gastrointestinal diseases in Southeast Asian countries: a meta-analysis  

PubMed Central

Background Infection with cagA-positive, cagA EPIYA motif ABD type, and vacA s1, m1, and i1 genotype strains of Helicobacter pylori is associated with an exacerbated inflammatory response and increased risk of gastroduodenal diseases. However, it is unclear whether the prevalence and virulence factor genotypes found in Southeast Asia are similar to those in Western countries. Here, we examined the cagA status and prevalence of cagA EPIYA motifs and vacA genotypes among H. pylori strains found in Southeast Asia and examined their association with gastroduodenal disease. Methods To determine the cagA status, cagA EPIYA motifs, and vacA genotypes of H. pylori, we conducted meta-analyses of 13 previous reports for 1,281?H. pylori strains detected from several Southeast Asian countries. Results The respective frequencies of cagA-positive and vacA s1, m1, and i1 genotypes among examined subjects were 93% (1,056/1,133), 98% (1,010/1,033), 58% (581/1,009), and 96% (248/259), respectively. Stratification showed significant variation in the frequencies of cagA status and vacA genotypes among countries and the individual races residing within each respective country. The frequency of the vacA m-region genotype in patients infected with East Asian-type strains differed significantly between the northern and southern areas of Vietnam (p?vacA m1 type or cagA-positive strains was associated with an increased risk of peptic ulcer disease (odds ratio: 1.46, 95%CI: 1.01-2.12, p?=?0.046 and 2.83, 1.50-5.34, p?=?0.001, respectively) in the examined Southeast Asian populations. Conclusions Both Western- and East Asian-type strains of H. pylori are found in Southeast Asia and are predominantly cagA-positive and vacA s1 type. In Southeast Asia, patients infected with vacA m1 type or cagA-positive strains have an increased risk of peptic ulcer disease. Thus, testing for this genotype and the presence of cagA may have clinical usefulness. PMID:22994150

2012-01-01

26

Diversity of Helicobacter Pylori cagA and vacA Genes and Its Relationship with Clinical Outcomes in Azerbaijan, Iran  

PubMed Central

Purpose: The purpose of this research was to analyze cagA and vacA genotypes status in H. pylori isolates and relationship with clinical outcomes. Methods: Gastric biopsy specimens were cultured for H. pylori isolation and cagA and vacA genes were detected in these isolates. Data were collected and the results were analyzed using ?2 and Fishers exact tests by SPSS software version. 16. Results: Of the total 115 H. pylori isolates, 79 (68.7 %) were cagA positive and 82 (71.3%) of isolates contained the s1 allele which 33 (28.7%) were subtype s2. s1m2 was the most frequent vacA allelic combination in the H. pylori isolates examined (63 cases), followed by s2m2 (31 cases), s1m1 (19 cases) and s2m1 (2 case). Strains cagA positive were more frequent in peptic ulcer diseases patients than non ulcer diseases patients, as 47 (59.5%) and 32 (40.5%), while cagA negative were low, as 15 (41.7%) and 21 (58.3%), respectively. Conclusion: We found that the cagA and vacA status were not related to clinical outcomes in this area. Overall, in the present study, vacA s1/m2, cagA-positive strains were predominant irrespective of clinical outcome, but s2/m1 was rare. PMID:24312813

Ghotaslou, Reza; Milani, Morteza; Akhi, Mohammad Taghi; Nahaei, Mohammad Reza; Hasani, Alka; Hejazi, Mohammad Saeid; Meshkini, Mohammad

2013-01-01

27

H. pylori Escape Host Immunoreaction Through Inhibiting ILK Expression by VacA  

PubMed Central

Helicobacter pylori (H. pylori) persistently colonizes the gastric mucosa despite a vigorous immune response. Vacuolating cytotoxin secreted by H. pylori has turned out to be a potent immunomodulatory toxin, but the signal transduction pathways involved has not been studied in macrophages. We observed in this study that vacA-deficient H. pylori induced significantly higher expression of integrin-linked kinase (ILK) and endothelial nitric oxygen synthase (eNOS), and significantly more production of reactive oxygen species (ROS) in monocyte/macrophage-like U937 cells, as compared with isogenic vacA+H. pylori. The expression of eNOS mRNA in U937 cells overexpressing ILK was markedly increased compared with those transfected with empty vectors. Thus, vacA-deficient H. pylori appears to upregulate ILK expression, which modulates the expression of eNOS and as a result, stimulates the production of ROS. It is VacA that prevents such a process by inhibiting ILK expression, helping H. pylori escape host immunoreaction. This mechanism explains, at least in part, persistent infection of H. pylori in the stomach. PMID:19567202

Yuan, Jianping; Li, Ping; Tao, Jing; Shi, Xiaodong; Hu, Baoyu; Chen, Huabiao; Guo, Xiaokui

2009-01-01

28

Characterization of virulence genes cagA and vacA in Helicobacter Pylori and their prevalence in gastrointestinal disorders  

PubMed Central

Prevalence of H. pylori infection was determined using cultures of gastric biopsy samples of patients attended at the academic hospital of the Federal University of Paraná, Curitiba, Paraná, Brazil. Molecular methods were used to characterize the cagA and vacA genes from bacterial isolates associated with different diseases presented by patients. Out of a total of 81, forty-two gastric biopsy samples tested were positive for H. pylori, with a prevalence of 51.9%. No significant difference was found with regard to the gender (p=0.793) and age (p=0.183) of the patients. Genotype s1m1 vacA gene was found in 67% of the cases of peptic ulcer investigated (p=1.0), despite the limited number of patients with this disease (n=3). A correlation between the presence of less virulent strains (s2m2) and reflux esophagitis was found in the majority of the cases (45%), but without statistical significance. An association between the prevalence of cagA gene, found in 92% of isolates, and peptic ulcer was not observed (p=1.0), suggesting that this gene cannot be considered a specific marker of severity in our environment. The results reinforce the importance of conducting regional studies and the need to characterize H. pylori virulence genes associated with different diseases. PMID:24031754

Cogo, Laura Lucia; Monteiro, Cristina Leise Bastos; Nogueira, Keite da Silva; Palmeiro, Jussara Kasuko; Ribeiro, Marcelo Lima; de Camargo, Eloa Ramalho; Neves, Daniel Locatelli; do Nascimento, Aguinaldo Jose; Costa, Libera Maria Dalla

2011-01-01

29

Helicobacter pylori vacuolating cytotoxin A (VacA) engages the mitochondrial fission machinery to induce host cell death  

PubMed Central

A number of pathogenic bacteria target mitochondria to modulate the host's apoptotic machinery. Studies here revealed that infection with the human gastric pathogen Helicobacter pylori disrupts the morphological dynamics of mitochondria as a mechanism to induce host cell death. The vacuolating cytotoxin A (VacA) is both essential and sufficient for inducing mitochondrial network fragmentation through the mitochondrial recruitment and activation of dynamin-related protein 1 (Drp1), which is a critical regulator of mitochondrial fission within cells. Inhibition of Drp1-induced mitochondrial fission within VacA-intoxicated cells inhibited the activation of the proapoptotic Bcl-2–associated X (Bax) protein, permeabilization of the mitochondrial outer membrane, and cell death. Our data reveal a heretofore unrecognized strategy by which a pathogenic microbe engages the host's apoptotic machinery. PMID:21903925

Jain, Prashant; Luo, Zhao-Qing; Blanke, Steven R.

2011-01-01

30

Distribution of Helicobacter pylori cagA, cagE, oipA and vacA in different major ethnic groups in Tehran, Iran  

PubMed Central

Background and Aim There are geographical variations in Helicobacter pylori virulence genes; cagA, cagE, vacA and oipA. The present study compared the distribution of these genotypes in major ethnic groups residing in Tehran, Iran and their association with clinical outcomes. Methods A total of 124 H. pylori-positive patients living in Tehran were enrolled in this study. The ethnic distribution was 74 Persians, 33 Turks and 17 other ethnics including Kurds, Lurs, Afghanis and Arabs. The presence of the cagA, cagE and oipA genes and vacA alleles (signal [s] and middle [m] region) were determined by polymerase chain reaction (PCR) from H. pylori DNA. Results The cagA-positive status was predominant in all three ethnic groups (e.g. 65% in Persians and 73% in Turks). In contrast, the cagE-positive status was less than half in Persians (47%) and Turks (30%), whereas it was 77% in other ethnicities (P = 0.008). The predominant vacA genotypes were s1 and m1 in all three ethnic groups (e.g. 68% in Persians and 70% in Turks were s1). There was no significant association between cagA and cagE status or vacA genotypes and clinical outcomes. The oipA-positive strains were more common in non-ulcer dyspepsia (NUD) (63%) than in peptic ulcer patients (15%) (P = 0.001) in Persians, but the association was not observed in other ethnic groups. Conclusion There are some differences in the H. pylori genotypes among the ethnic groups in Iran. However, none of these markers seemed to be clinically helpful in predicting the clinical presentation of a H. pylori infection in Iran. PMID:19702906

Dabiri, Hossein; Maleknejad, Parviz; Yamaoka, Yoshio; Feizabadi, Mohammad M; Jafari, Fereshteh; Rezadehbashi, Maryam; Nakhjavani, Farrokh A; Mirsalehian, Akbar; Zali, Mohammad R

2011-01-01

31

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. PMID:24349721

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

2013-01-01

32

Helicobacter pylori genotyping from American indigenous groups shows novel Amerindian vacA and cagA alleles and Asian, African and European admixture.  

PubMed

It is valuable to extend genotyping studies of Helicobacter pylori to strains from indigenous communities across the world to better define adaption, evolution, and associated diseases. We aimed to genetically characterize both human individuals and their infecting H. pylori from indigenous communities of Mexico, and to compare them with those from other human groups. We studied individuals from three indigenous groups, Tarahumaras from the North, Huichols from the West and Nahuas from the center of Mexico. Volunteers were sampled at their community site, DNA was isolated from white blood cells and mtDNA, Y-chromosome, and STR alleles were studied. H. pylori was cultured from gastric juice, and DNA extracted for genotyping of virulence and housekeeping genes. We found Amerindian mtDNA haplogroups (A, B, C, and D), Y-chromosome DYS19T, and Amerindian STRs alleles frequent in the three groups, confirming Amerindian ancestry in these Mexican groups. Concerning H.pylori cagA phylogenetic analyses, although most isolates were of the Western type, a new Amerindian cluster neither Western nor Asian, was formed by some indigenous Mexican, Colombian, Peruvian and Venezuelan isolates. Similarly, vacA phylogenetic analyses showed the existence of a novel Amerindian type in isolates from Alaska, Mexico and Colombia. With hspA strains from Mexico and other American groups clustered within the three major groups, Asian, African or European. Genotyping of housekeeping genes confirmed that Mexican strains formed a novel Asian-related Amerindian group together with strains from remote Amazon Aborigines. This study shows that Mexican indigenous people with Amerindian markers are colonized with H. pylori showing admixture of Asian, European and African strains in genes known to interact with the gastric mucosa. We present evidence of novel Amerindian cagA and vacA alleles in indigenous groups of North and South America. PMID:22073291

Camorlinga-Ponce, Margarita; Perez-Perez, Guillermo; Gonzalez-Valencia, Gerardo; Mendoza, Irma; Peñaloza-Espinosa, Rosenda; Ramos, Irma; Kersulyte, Dangeruta; Reyes-Leon, Adriana; Romo, Carolina; Granados, Julio; Muñoz, Leopoldo; Berg, Douglas E; Torres, Javier

2011-01-01

33

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

34

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

35

Linking sedimentological, stratigraphic and diagenetic processes to understand unconventional reservoirs: the Upper Jurassic Vaca  

E-print Network

Linking sedimentological, stratigraphic and diagenetic processes to understand unconventional as to the scale of sedimentological variability within mudstone successions, and how related diagenetic alteration by Profs Taylor and Flint, to document the scale of sedimentological and diagenetic variability

Henderson, Gideon

36

ADHESION TESTING OF EPOXY COATING Enrique Vaca-Corts, Miguel A. Lorenzo, James O. Jirsa,  

E-print Network

, Harovel G. Wheat, Ramón L. Carrasquillo Research Report No. 1265-6 Research Project 0-1265 Structural FOR TRANSPORTATION RESEARCH BUREAU OF ENGINEERING RESEARCH THE UNIVERSITY OF TEXAS AT AUSTIN September 1998 #12;KX, method, process, machine, manufacture, design or composition of matter, or any new and useful improvement

Texas at Austin, University of

37

Demagnetization of spin systems at low temperature J. Marro and J. A. Vacas  

E-print Network

, fluctuations with power spectrum S( ) , 0, i.e., more correlated than white noise, have been reported, e results for the time evolution of a lattice model of ferromagnetic particles after field inversion-state condition asymptotically. Critical avalanches and constant magnetic viscosity at low T ensue as two key

Marro, Joaquín

38

Demagnetization of spin systems at low temperature J. Marro and J. A. Vacas  

E-print Network

, fluctuations * *with power spectrum S ( ) ~ -ff, ff > 0, i.e., more correlated than white noise, ha* *ve* * a (lattice) model of ferromagnetic particle after field inversion. Relaxatio* *n from the metastable-state condition asymptotically. Critical avalanche* *s, and constant magnetic viscosity at low T ensue

Marro, Joaquín

39

VaCAS Seminar 11:00 AM to 12:00 PM  

E-print Network

techniques to automatically track productivity, safety, quality, and carbon footprint of operations. #12;/Engineering/Construction and Facility Management activities is critical to project management as it provides an opportunity to initiate proactive actions to avoid them or minimize their impacts. Despite the importance, current monitoring

Virginia Tech

40

The hero's story: typology, biblical allusion, and persona in Alvar Nu?n?ez Cabeza de Vaca's Narrative  

E-print Network

possibly somewhat obscure. It is as if the author, in consequence of long isolation and constant intercourse with people of another speech had lost touch with his native tongue. (Ad. F. Bandelier xxii) Nevertheless, Fanny Bandelier's translation (based... "burning tree" and presumes God sent it: "It pleased God to let me find a burning tree, by the fire of which I spent that very cold night, (F. Bandelier 102) Here the bond he forms between himself and Moses, who 37 found a burning bush, thanks to God...

Bell, Glenna Gail

2012-06-07

41

Low Stress Cattle Handling in Dairy Environments (Spanish)  

E-print Network

huida): Si a las vacas lecheras se les acerca primero voltean de frente y si se contin?a acerc?ndoseles se mueven. Movimiento en una sola fila: Las vacas lecheras siguen al l?der formando una sola fila. Maneje grupos de vacas en una sola fila para... huida): Si a las vacas lecheras se les acerca primero voltean de frente y si se contin?a acerc?ndoseles se mueven. Movimiento en una sola fila: Las vacas lecheras siguen al l?der formando una sola fila. Maneje grupos de vacas en una sola fila para...

Villarino, Mario A.

2009-05-04

42

Increased in-vitro and in-vivo biological activity of lipopolysaccharide extracted from clinical low virulence vacA genotype Helicobacter pylori strains  

Microsoft Academic Search

Helicobacter pylori infection in man is associated with chronic gastritis and peptic ulcer disease. The virulence factors of the species are still under investigation. Among these, the lipopolysaccharide (LPS) is a potential pathogenic factor of the micro-organism, whose biological activity can be estimated by immunological parameters. The aim of this study was to determine the ability of pure LPS extracted

FERNANDO SALGADO; APOLINARIA GARCIA; ANGEL ONATE; CARLOS GONZALEZ; FERNANDO KAWAGUCHI

43

Resistencia bacteriana en cepas patógenas aisladas de mastitis en vacas lecheras de la V Región, Región Metropolitana y Xª Región, Chile* Bacterial resistance of mastitis pathogens isolated from dairy cows in the Vth Region, Metropolitan Region and Xth Region, Chile  

Microsoft Academic Search

3 Cooprinsem, Casilla 827, Osorno, Chile. SUMMARY Antimicrobial chemotherapy in human and veterinary medicine is one of the most important therapeutic tool against pathogenic agents causing infectious diseases; nevertheless, the development of multiple resistant strains during the last years has been reported. Some of the measures adopted to control this problem have been the veterinary prescription of antimicrobials for animal

B. SAN MARTIN

44

The vacuolating toxin from Helicobacter pylori forms hexameric pores in lipid bilayers at low pH  

PubMed Central

Pathogenic strains of Helicobacter pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predominantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH ?5, VacA associates with anionic lipid bilayers to form hexameric membrane-associated complexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into membrane-spanning hexamers. The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measurements indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar lipid bilayers. This low pH-triggered pore formation is likely a critical step in VacA activity. PMID:10051584

Czajkowsky, Daniel M.; Iwamoto, Hideki; Cover, Timothy L.; Shao, Zhifeng

1999-01-01

45

Diagnostico de Prenez en Ganado Vacuno.  

E-print Network

Becerros logrados (por 100 vacas) 550' 500 450 400 350 1 90 19.2 21.1 23.5 26.4 30.2 330 300 270 240 21 0 60 28.8 31.7 35.2 39.6 45.2 'Los nlimeros de arriba indican libras de becerro producido por vaca. CARUNCULAS \\ VULVA Figura 2. Anatornia del... Becerros logrados (por 100 vacas) 550' 500 450 400 350 1 90 19.2 21.1 23.5 26.4 30.2 330 300 270 240 21 0 60 28.8 31.7 35.2 39.6 45.2 'Los nlimeros de arriba indican libras de becerro producido por vaca. CARUNCULAS \\ VULVA Figura 2. Anatornia del...

Sorensen, A. M. Jr.; Beverly, J. R.; Arias, A. A.

1975-01-01

46

Programa de CaPaCitaCin y eduCaCin en Seguridad y Salud Para trabajadoreS  

E-print Network

trabajar con seguridad con el ganado, necesitas entender a los animales. Hablemos de algunas cosas escape, el ganado volteará sus cuerpos de manera que puedan ver al trabajador. Las vacas son animales

Leistikow, Bruce N.

47

VACAS TERMINADAS EM CAMPO NA TIVO SUPLEMENT ADAS COM F ARELO DE TRIGO OU F ARELO DE ARROZ INTEGRAL CONTENDO OU NÃO MONENSINA SÓDICA Finished cows in native grass supplemented with wheat bran or rice bran with or without sodic monensin  

Microsoft Academic Search

The performance, physical composition, income of commercial cuts the quality of the meat of twenty eight cows Charolais, Nellore and its cross, were evaluated with initial average live weight of 409kg, finished in native grass with high participation of Eragrostis plana Nees., supplemented per 99 days with wheat bran or rice bran 0.5% of the alive weight in the DM

Milene Puntel Osmari; Miguelangelo Ziegler Arboitte; Ivan Luiz Brondani; Fernando Kuss; Dari Celstino; Alves Filho; João Restle

48

Efectos genéticos directos, maternos y heterosis individual para tasas de estro, gestación, parición y destete de vacas Criollo, Guzerat y sus cruzas F1 Breed effects and individual heterosis for pregnancy, calving and weaning rates in Criollo, Guzerat and F1 cows  

Microsoft Academic Search

Reproductive records of beef cows were collected in 2000, 2001, 2002 and 2003 to estimate direct and maternal genetic effects and to compare estrous (ER), pregnancy (PR), calving (CR) and weaning (WR) rates. Data was collected from Guzerat (G, n=202), Criollo (C, n=126), Criollo x Guzerat (CG, n=101) and Guzerat x Criollo (GC, n=35) cows. Analyses were carried out with

Guillermo Martínez Velázquez; Moisés Montaño Bermúdez; José Antonio Palacios Fránquezb

49

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. 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

50

Assisting Difficult Calving (Spanish)  

E-print Network

etapa. El segundo saco de fluidos (saco amni?tico) normalmente es forzado a trav?s de la vulva despu?s de iniciada la labor de parto. El *Professor and Extension Program Leader for Veterinary Medicine and Extension Associate?Animal Science, Texas... presi?n abdominal por dos horas sin presentaci?n del becerro, la vaca deber? ser examinada. Si la vaca presenta el saco amni?tico a trav?s de la vulva y no ha parido en dos horas, se deber? ayudar con el parto. Una vez que las primeras partes del...

Faries Jr., Floron C.; Villarino, Mario A.

2009-03-05

51

Promoter DNA Hypermethylation in Gastric Biopsies from Subjects at High and Low Risk for Gastric Cancer  

PubMed Central

Gene promoter CpG island hypermethylation is associated with Helicobacter pylori (H. pylori) infection and may be an important initiator of gastric carcinogenesis. To examine factors influencing methylation, we utilized bisulfite Pyrosequencing® technology for quantitative analysis of promoter DNA methylation in RPRM, APC, MGMT and TWIST1 genes using DNA from 86 gastric biopsies from Colombian residents of areas with high and low incidence of gastric cancer. H. pylori colonies were cultured from the same subjects, and gastric pathology was evaluated. Virulence factors cagA (including EPIYA polymorphisms of the 3’ end) and vacA s and m regions were characterized in the H. pylori strains. Using univariate analysis, we found significantly elevated levels of RPRM and TWIST1 promoter DNA methylation in biopsies from residents of the high risk region compared to those from residents of the low risk region. The presence of cagA and vacA s1m1 alleles were independently associated with elevated levels of promoter DNA methylation of RPRM and MGMT. Using multivariate analysis, DNA methylation of RPRM was associated with location of residence, cagA and vacA s1m1 status, and methylation of TWIST1. We conclude that cagA and vacA virulence determinants are significantly associated with quantitative differences in promoter DNA methylation in these populations, but that other as yet undefined factors that differ between the populations may also contribute to variation in methylation status. PMID:20178103

Schneider, Barbara G.; Peng, Dun-Fa; Camargo, M. Constanza; Piazuelo, M. Blanca; Sicinschi, Liviu A.; Mera, Robertino; Romero-Gallo, Judith; Delgado, Alberto G.; Bravo, Luis E.; Wilson, Keith T.; Peek, Richard M.; Correa, Pelayo; El-Rifai, Wael

2010-01-01

52

Linking Accelerating Laboratory Test with Outdoor Performance Results for a Model Epoxy Coating System  

E-print Network

Linking Accelerating Laboratory Test with Outdoor Performance Results for a Model Epoxy Coating System Xiaohong Gu1 , Brian Dickens1 , Debbie Stanley1 , Walter E. Byrd1 , Tinh Nguyen1 , Iliana Vaca Iowa State University, Ames, IA 50011 1 #12;ABSTRACT Laboratory and outdoor exposure results have been

53

Una vez concluido el plazo de presentacin, y revisadas las solicitudes, se resuelve la VI Convocatoria de Ayudas, de acuerdo a la relacin que figura debajo. Los solicitantes excluidos  

E-print Network

Figueroa Domeq, Cristina Turismo y Deporte Grande Pesquero, Mª del Carmen El Impacto de la Ordenación del DIRECTOR/ES III Jornadas de Turismo Sostenible Bonilla Priego, Mª Jesús y Vacas Guerrero, Trinidad Enciso Alonso-Muñumer, Isabel Luisa III Jornada Internacional de Nuevo Turismo en la URJC: " From Service

Rey Juan Carlos, Universidad

54

A Stable Marriage Framework for Distributed Virtual MIMO Coalition Formation  

E-print Network

A Stable Marriage Framework for Distributed Virtual MIMO Coalition Formation Rodrigo A. Vaca Ram Multiple-input Multiple-output (MIMO) coalition formation is proposed. We model cooperation as a game. INTRODUCTION Multi-antenna systems have emerged as an effective way to improve capacity and energy efficiency

Paris-Sud XI, Université de

55

29 June 2010 Aristotle put together a list of birds (n =170)  

E-print Network

1920s John Muir (1838 ­ 1914) One of the first modern preservationists Essays on nature & wildlife birds passing." - Christopher Columbus De Vaca (1528), Castenada (1541-1542) noted birds John White (1585) painted watercolors The Ornithology of Francis Willughby (1678) by Willughby and John Ray

Butler, Christopher J.

56

November already? We will soon be planning for  

E-print Network

November already? We will soon be planning for holiday time and looking forward to a little vaca- tion. The staff are doing a great job with the pro- gram plans and I look forward to seeing the children excel in their learning. We are pleased that Car- melita is back Oct 15th - 3 days per week Tues

57

Markov Indecision Processes: A Formal Model of Decision-Making Under Extreme Confusion  

E-print Network

and the stock market. 1. Introduction It has been claimed that any goal- or gain-oriented human endeavor, from the belief that modeling confused human agents is beyond the scope of current techniques. Therefore, we nature; vaca- tion and wedding planning; and naming and raising children. In this paper, we aim

Goldsmith, Judy

58

El sexo recompensado: una práctica en el centro de las vulnerabilidades (ITS\\/VIH\\/SIDA) de las jóvenes mexicanas  

Microsoft Academic Search

Objective. To discuss the risks for Mexican young women who engage in sexual relations in exchange for social or economic benefits, also known as compensated sex (CS), with the objective of exploring its possible public health implications. Material and Methods. This is a qualitative study conducted in youths 15 to 25 years of age in Cuerna- vaca, Morelos, Mexico, between

Florence Lise Théodore; Juan Pablo Gutiérrez; Pilar Torres; Gabriela Luna

2004-01-01

59

Cell culture assays to evaluate bacterial toxicity and virulence.  

PubMed

Helicobacter pylori CagA and VacA are two critical virulence factors that modulate disease severity in the infected host. The following chapter outlines methods employed to study the effects of these virulence factors on several key signaling pathways in epithelial cells. PMID:23015494

Raju, Deepa; Rizzuti, David; Jones, Nicola L

2012-01-01

60

Blood types in cattle of Iberian ancestry and in Holsteins at various altitudes.  

PubMed

Gene frequencies of RBC antigens were determined in Holsteins and Colombian (criollas) cattle living at 3,000 m, and in cattle descended from fighting bulls (Vacas de lidia) living at 2,500 m. These frequencies were compared with those of Holsteins, cattle native to Florida (scrub cattle), longhorns, and native cattle from Brazil (caracu cattle) living at sea level. The criollas, Vacas de lidia, scrub cows, longhorns, and caracu are descendants of original Iberian stock introduced to the Americas. We found that despite common ancestry (scrub cattle, long-horns, criollas, and caracu), genetic differences may have been derived through years of demographic isolation. The most remarkable blood-group differences were found in the high prevalence of the B system phenogroup (heritable group of antigenic factors) BQA'G'34 in the Vacas de lidia, and of the S system phenogroup U1H' in these cattle and in caracu. Furthermore, the gene frequencies differed in the Holsteins maintained at moderately high altitude (descended from Holsteins kept at sea level), and may have been reflective of the need to adapt to moderately high altitude and chronic hypoxemic conditions. Blood group polymorphism was found in all groups of cattle, although it was reduced in the Vacas de lidia, possibly because their breeding has been carefully controlled and they appear to be highly inbred. PMID:1497198

Ramirez, G; Miller, W J; Bittle, P A; Hidalgo, A; Santacruz, R; Colice, G

1992-07-01

61

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

62

Ethnicity association of Helicobacter pylori virulence genotype and metronidazole susceptibility  

PubMed Central

AIM: To characterise the cag pathogenicity island in Helicobacter pylori (H. pylori) isolates by analysing the strains’ vacA alleles and metronidazole susceptibilities in light of patient ethnicity and clinical outcome. METHODS: Ninety-five H. pylori clinical isolates obtained from patients with dyspepsia living in Malaysia were analysed in this study. Six genes in the cagPAI region (cagE, cagM, cagT, cag13, cag10 and cag67) and vacA alleles of the H. pylori isolates were identified by polymerase chain reaction. The isolates’ metronidazole susceptibility was also determined using the E-test method, and the resistant gene was characterised by sequencing. RESULTS: More than 90% of the tested isolates had at least one gene in the cagPAI region, and cag67 was predominantly detected in the strains isolated from the Chinese patients, compared with the Malay and Indian patients (P < 0.0001). The majority of the isolates (88%) exhibited partial deletion (rearrangement) in the cagPAI region, with nineteen different patterns observed. Strains with intact or deleted cagPAI regions were detected in 3.2% and 8.4% of isolates, respectively. The prevalence of vacA s1m1 was significantly higher in the Malay and Indian isolates, whereas the isolates from the Chinese patients were predominantly genotyped as vacA s1m2 (P = 0.018). Additionally, the isolates from the Chinese patients were more sensitive to metronidazole than the isolates from the Malay and Indian patients (P = 0.047). Although we attempted to relate the cagPAI genotypes, vacA alleles and metronidazole susceptibilities to disease outcome, no association was observed. The vacA alleles were distributed evenly among the strains with intact, partially deleted or deleted cagPAI regions. Interestingly, the strains exhibiting an intact cagPAI region were sensitive to metronidazole, whereas the strains with a deleted cagPAI were more resistant. CONCLUSION: Successful colonisation by different H. pylori genotypes is dependent on the host’s genetic makeup and may play an important role in the clinical outcome. PMID:23483193

Alfizah, Hanafiah; Rukman, Awang Hamat; Norazah, Ahmad; Hamizah, Razlan; Ramelah, Mohamed

2013-01-01

63

Kinetics and Mechanisms of Extracellular Protein Release by Helicobacter pylori  

PubMed Central

To investigate the kinetics and mechanisms of extracellular protein release by Helicobacter pylori, we analyzed the entry of metabolically radiolabeled bacterial proteins into broth culture supernatant. At early time points, vacuolating cytotoxin (VacA) constituted a major extracellular protein. Subsequently, culture supernatants accumulated many proteins that were components of intact bacterial cells. This nonselective release of proteins was associated with a decreasing turbidity of cultures and loss of bacterial viability, indicative of an autolytic process. The rates of VacA secretion and autolysis were each influenced by medium composition, and therefore these may be regulated phenomena. Extracellular release of proteins by H. pylori may be an important adaptation that facilitates the persistence of H. pylori in the human gastric mucus layer. Moreover, entry of proinflammatory proteins into the gastric mucosa may contribute to the induction of a mucosal inflammatory response. PMID:10496902

Schraw, Wayne; McClain, Mark S.; Cover, Timothy L.

1999-01-01

64

A study of a special training approach for recreation and parks and resource development personnel  

E-print Network

. he c(uestionnaire reported Lotals 2. ~- Pu', l. -ti. :. c cr&-icy, cr &r&. re &nonsi&lered &-o be tiros a&or!ring a full s . &&edule 2 months of' the year. less regular vacaLion time. Part- t!sr, - e&nploye& s incl &le&! those wire worl- or& a full.... he c(uestionnaire reported Lotals 2. ~- Pu', l. -ti. :. c cr&-icy, cr &r&. re &nonsi&lered &-o be tiros a&or!ring a full s . &&edule 2 months of' the year. less regular vacaLion time. Part- t!sr, - e&nploye& s incl &le&! those wire worl- or& a full...

Smith, James Stephen

2012-06-07

65

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.

66

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

67

Analysis of Helicobacter pylori Genotypes in Afghani and Iranian Isolates  

PubMed Central

The geographical variation in Helicobacter pylori genotypes is an observed phenomenon. Cytotoxin associated genes A (cagA) and E (cagE), and vacuolating cytotoxin (vacA) genotypes of H. pylori are associated with peptic ulcer disease (PUD). This study compared the distribution of these genotypes in Iranian and Afghani isolates and their association with clinical outcomes. H. pylori infected patients, as proven by positive culture, were recruited prospectively. A total of 70 patients, 55 Iranian (26 men and 29 women, mean age 48±18 years) and 15 Afghani immigrants (13 men and 2 women, mean age 34.8±11 years) living in Tehran, Iran were enrolled in this study. DNA was extracted from isolated H. pylori and polymerase chain reaction was carried out to determine the cagA and cagE status and vacA alleles. The number of gastric cancer, peptic ulcer and gastritis cases was 11, 23 and 36, respectively. The cagA positive isolates were more common in Iranian (67%) than Afghani isolates (60%). cagE was positive in 53% of Afghani compared to 51% of Iranian isolates. The most common vacA s-region genotype was s1; 80% in Afghani and 67% in Iranian. The s1m1 was a frequently observed genotype in Afghani strains (53%) while s1m2 (47%) was more common in strains isolated from Iranian patients. There is a difference in the H. pylori strains between Iranian and Afghani groups, for instance Iranian isolates were similar to European isolates while Afghani isolates were similar to isolates from India. However, there was no significant association between cagA, cagE and vacA genotypes and clinical outcomes in Iranian and Afghani patients. PMID:20568532

Dabrii, Hossein; Bolfion, Mehdi; Mirsalehian, Akbar; Rezadehbashi, Maryam; Jafari, Fereshteh; Shokrzadeh, Leila; Sahebekhtiari, Navid; Zojaji, Homayon; Yamaoka, Yoshio; Mirsattari, Darioush; Zali, Mohammad Reza

2011-01-01

68

Cytotoxic Action of Serratia marcescens Hemolysin on Human Epithelial Cells  

Microsoft Academic Search

Incubation of human epithelial cells with nanomolar concentrations of chromatographically purified Serratia marcescens hemolysin (ShlA) caused irreversible vacuolation and subsequent lysis of the cells. Vacuolation differed from vacuole formation by Helicobacter pylori VacA. Sublytic doses of ShlA led to a reversible depletion of intracellular ATP. Restoration to the initial ATP level was presumably due to the repair of the toxin

RALF HERTLE; MARTINA HILGER; SANDRA WEINGARDT-KOCHER

69

Genotyping of Helicobacter pylori strains from gastric biopsies by multiplex polymerase chain reaction. How advantageous is it?  

PubMed

Recent application of multiplex polymerase chain reaction (PCR) for genotyping Helicobacter pylori direct from biopsies revealed variable results (detection of amplicons from DNA extracted by boiling biopsies, variable size amplicons and deletions, uniform intensity of amplicon bands). We aimed to look at how applicable the technique is for determining cagA and vacA genotypes and to correlate the results with the severity of the disease. H. pylori strains from 52 patients (35 duodenal ulcers [DUs], 7 gastric ulcers [GUs], 10 gastritis) were included. Three antral biopsies were obtained for Campylobacter-like organism (CLO) and PCR. Primers for cagA, vacA s1s2, and m1m2 alleles were used. No PCR amplicons were detected from boiling biopsies; thus, DNA was extracted by QIAamp kit. H. pylori was positive in 84.6% of the patients (85.7% DU, 100% GU, and 70% gastritis). The cagA gene was detected in 86.6% DU, 71.4% GU, and 57.0% gastritis patients. The vacA allelic distribution among cagA-positive strains was 80.7% s1m1 in DU and 60.0% in GU patients, whereas 75.0% of gastritis had s1m2. No variability in the amplicon sizes was found, and the intensity of the amplicon bands was not uniform. A deleted band of approximately 420 bp below the m1 band was detected in strains from 2 DU and 1 GU patients. Although the multiplex PCR is a rapid and an effective tool for detecting several genes in a single-step system, one has to adjust for optimization of the technique when genotyping H. pylori direct from biopsies. A significant association was found between the cagA-positive vacA-s1m1 genotype and peptic ulcers. PMID:17300903

Bolek, Bora Kazim; Salih, Barik A; Sander, Ersan

2007-05-01

70

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

71

Association of Helicobacter pylori genotype with gastroesophageal reflux disease and other upper gastrointestinal diseases  

Microsoft Academic Search

OBJECTIVE:Helicobacter pylori (H. pylori) is a recognized pathogen, but it may also have a protective effect for gastroesophageal reflux disease (GERD). We compared the prevalence of potential virulence factors (cagA, cagE, vacA genotypes) in GERD to other upper gastrointestinal diseases and controls.METHODS:A total of 405 patients underwent gastroscopy with H. pylori isolation and serum testing. Patient diagnostic subgroups were prospectively

Carlo A. Fallone; Alan N. Barkun; Markus U. Gottke; Linda M. Best; Vivian G. Loo; Sander Veldhuyzen van Zanten; Thanh Nguyen; Aviva Lowe; Toby Fainsilber; Kim Kouri; Robin Beech

2000-01-01

72

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. 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

73

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. PMID:21623037

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

2011-01-01

74

RIGIDECES INSTITUCIONALES Y FLEXIBILIDAD PRESUPUESTARIA: LOS CASOS DE ARGENTINA, COLOMBIA, MÉXICO Y PERÚ  

Microsoft Academic Search

En los últimos años se ha hecho evidente que los gobiernos cuentan con un margen de maniobra reducido en la elaboración del presupuesto, pues una proporción importante de los gastos se encuentra predeterminada por normas legales, mandatos constitucionales, compromisos previamente adquiridos por el gobierno, y requerimientos del actual ejercicio presupuestario. Este estudio analiza el fenómeno de las inflexibilidades presupuestales partiendo

Juan Carlos Echeverry; Jorge Alexander Bonilla; Andrés Moya

2006-01-01

75

Multivariate classification based on chemical and stable isotopic profiles in sourcing the origin of marijuana samples seized in Brazil  

Microsoft Academic Search

Este trabalho teve como principal objetivo verificar as diferenças existentes na composição elementar de amostras de Cannabis, apreendidas em diferentes regiões produtoras do país, previamente separadas através da análise de isótopos estáveis de carbono e nitrogênio, e utilizar estas diferenças para classificar as amostras de acordo com sua origem geográfica. A técnica analítica empregada foi a de espectrometria de massas

Elisa K. Shibuya; Jorge E. S. Sarkis; Osvaldo Negrini-Neto; Jean P. H. B. Ometto

2007-01-01

76

REGULAMENTO DIPLOMAS IST  

E-print Network

de aceitação das candidaturas apresentada pelo órgão próprio de coordenação do curso; b) Pelo numerus clausus do curso, previamente fixado pelo Conselho Científico do IST sob proposta do órgão próprio de

77

Study of Helicobacter pylori genotype status in saliva, dental plaques, stool and gastric biopsy samples  

PubMed Central

AIM: To compare genotype of Helicobacter pylori (H. pylori) isolated from saliva, dental plaques, gastric biopsy, and stool of each patient in order to evaluate the mode of transmission of H. pylori infection. METHODS: This cross-sectional descriptive study was performed on 300 antral gastric biopsy, saliva, dental plaque and stool samples which were obtained from patients undergoing upper gastrointestinal tract endoscopy referred to endoscopy centre of Hajar hospital of Shahrekord, Iran from March 2010 to February 2011. Initially, H. pylori strains were identified by rapid urease test (RUT) and polymerase chain reaction (PCR) were applied to determine the presence of H. pylori (ureC) and for genotyping of voculating cytotoxin gene A (vacA) and cytotoxin associated gene A (cagA) genes in each specimen. Finally the data were analyzed by using statistical formulas such as Chi-square and Fisher’s exact tests to find any significant relationship between these genes and patient’s diseases. P < 0.05 was considered statistically significant. RESULTS: Of 300 gastric biopsy samples, 77.66% were confirmed to be H. pylori positive by PCR assay while this bacterium were detected in 10.72% of saliva, 71.67% of stool samples. We were not able to find it in dental plaque specimens. The prevalence of H. pylori was 90.47% among patients with peptic ulcer disease (PUD), 80% among patients with gastric cancer, and 74.13% among patients with none ulcer dyspepsia (NUD) by PCR assay. The evaluation of vacA and cagA genes showed 6 differences between gastric biopsy and saliva specimens and 11 differences between gastric and stool specimens. 94.42% of H. pylori positive specimens were cagA positive and all samples had amplified band both for vacA s and m regions. There was significant relationship between vacA s1a/m1a and PUD diseases (P = 0.04), s2/m2 genotype and NUD diseases (P = 0.05). No statically significant relationship was found between cagA status with clinical outcomes and vacA genotypes (P = 0.65). The evaluation of vacA and cagA genes showed 6 differences between gastric biopsy and saliva specimens and 11 differences between gastric and stool specimens. CONCLUSION: Regard to high similarity in genotype of H. pylori isolates from saliva, stomach and stool, this study support the idea which fecal- oral is the main route of H. pylori transmission and oral cavity may serve as a reservoir for H. pylori, however, remarkable genotype diversity among stomach, saliva and stool samples showed that more than one H. pylori genotype may exist in a same patient. PMID:22563199

Momtaz, Hassan; Souod, Negar; Dabiri, Hossein; Sarshar, Meysam

2012-01-01

78

Mixed Infection with cagA Positive and cagA Negative Strains of Helicobacter pylori Lowers Disease Burden in The Gambia  

PubMed Central

Background The prevalence of Helicobacter pylori including strains with putatively virulent genotypes is high, whereas the H. pylori-associated disease burden is low, in Africa compared to developed countries. In this study, we investigated the prevalence of virulence-related H. pylori genotypes and their association with gastroduodenal diseases in The Gambia. Methods and Findings DNA extracted from biopsies and H. pylori cultures from 169 subjects with abdominal pain, dyspepsia or other gastroduodenal diseases were tested by PCR for H. pylori. The H. pylori positive samples were further tested for the cagA oncogene and vacA toxin gene. One hundred and twenty one subjects (71.6%) were H. pylori positive. The cagA gene and more toxigenic s1 and m1 alleles of the vacA gene were found in 61.2%, 76.9% and 45.5% respectively of Gambian patients harbouring H. pylori. There was a high prevalence of cagA positive strains in patients with overt gastric diseases than those with non-ulcerative dyspepsia (NUD) (p?=?0.05); however, mixed infection by cagA positive and cagA negative strains was more common in patients with NUD compared to patients with gastric disease (24.5% versus 0%; p?=?0.002). Conclusion This study shows that the prevalence of H. pylori is high in dyspeptic patients in The Gambia and that many strains are of the putatively more virulent cagA+, vacAs1 and vacAm1 genotypes. This study has also shown significantly lower disease burden in Gambians infected with a mixture of cag-positive and cag-negative strains, relative to those containing only cag-positive or only cag-negative strains, which suggests that harbouring both cag-positive and cag-negative strains is protective. PMID:22140492

Secka, Ousman; Antonio, Martin; Berg, Douglas E.; Tapgun, Mary; Bottomley, Christian; Thomas, Vivat; Walton, Robert; Corrah, Tumani; Thomas, Julian E.; Adegbola, Richard A.

2011-01-01

79

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-López, Luis R.

2003-01-01

80

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

81

Disease association with two Helicobacter pylori duplicate outer membrane protein genes, homB and homA  

PubMed Central

Background homB encodes a Helicobacter pylori outer membrane protein. This gene was previously associated with peptic ulcer disease (PUD) and was shown to induce activation of interleukin-8 secretion in vitro, as well as contributing to bacterial adherence. Its 90%-similar gene, homA, was previously correlated with gastritis. The present study aimed to evaluate the gastric disease association with homB and homA, as well as with the H. pylori virulence factors cagA, babA and vacA, in 415 H. pylori strains isolated from patients from East Asian and Western countries. The correlation among these genotypes was also evaluated. Results Both homB and homA genes were heterogeneously distributed worldwide, with a marked difference between East Asian and Western strains. In Western strains (n = 234, 124 PUD and 110 non-ulcer dyspepsia (NUD), homB, cagA and vacA s1 were all significantly associated with PUD (p = 0.025, p = 0.014, p = 0.039, respectively), and homA was closely correlated with NUD (p = 0.072). In East Asian strains (n = 138, 73 PUD and 65 NUD), homB was found more frequently than homA, and none of these genes was associated with the clinical outcome. Overall, homB was associated with the presence of cagA (p = 0.043) and vacA s1 (p < 0.001), whereas homA was found more frequently in cagA-negative (p = 0.062) and vacA s2 (p < 0.001) strains. Polymorphisms in homB and homA copy number were observed, with a clear geographical specificity, suggesting an involvement of these genes in host adaptation. A correlation between the homB two-copy genotype and PUD was also observed, emphasizing the role of homB in the virulence of the strain. Conclusion The global results suggest that homB and homA contribute to the determination of clinical outcome. PMID:19545429

Oleastro, Monica; Cordeiro, Rita; Yamaoka, Yoshio; Queiroz, Dulciene; Megraud, Francis; Monteiro, Lurdes; Menard, Armelle

2009-01-01

82

Comparison of the Virulence Markers of Helicobacter Pylori and their Associated Diseases in Patients from Pakistan and Afghanistan  

PubMed Central

Background/Aim: Helicobacter pylori is a Gram-negative bacteria, which is associated with development of gastroduodenal diseases. The prevalence of H. pylori and the virulence markers cytotoxin-associated gene A and E (cagA, cagE) and vacuolating-associated cytotoxin gene (vacA) alleles varies in different parts of the world. H. pylori virulence markers cagA, cagE, and vacA alleles in local and Afghan nationals with H. pylori-associated gastroduodenal diseases were studied. Patients and Methods: Two hundred and ten patients with upper gastrointestinal symptoms and positive for H. pylori by the urease test and histology were included. One hundred and nineteen were local nationals and 91 were Afghans. The cagA, cagE, and vacA allelic status was determined by polymerase chain reaction. Results: The nonulcer dyspepsia (NUD) was common in the Afghan patients (P = 0.025). In Afghan H. pylori strains, cagA was positive in 14 (82%) with gastric carcinoma (GC) compared with 29 (45%) with NUD (P = 0.006), whereas cagE was positive in 11 (65%) with GC and 4 (67%) with duodenal ulcer (DU) compared with 12 (18%) with NUD (P < 0.001 and 0.021, respectively). The vacA s1a/b1 was positive in 10 (59%) of GC compared with 20 (31%) in NUD (P = 0.033). In Pakistani strains, cagE was positive in 12 (60%) with GC, 7 (58%) with GU, 12 (60%) with DU compared with 11 (16%) with NUD (P < 0.001, 0.004, and < 0.001, respectively). In Pakistani strains, cagA/s1a/m1 was 39 (33%) compared with Afghans in 17 (19%) (P = 0.022). Moderate to severe mucosal inflammation was present in 51 (43%) Pakistani patients compared with 26 (28%) (P = 0.033) in Afghans. It was also associated with grade 1 lymphoid aggregate development in Pakistani patients 67 (56%) compared with 36 (40%) (P = 0.016) in Afghans. Conclusion: Distribution of H. pylori virulence marker cagE with DU was similar in Afghan and Pakistan H. pylori strains. Chronic active inflammation was significantly associated with Pakistani H. pylori strains. PMID:24045594

Yakoob, Javed; Abbas, Zaigham; Jafri, Wasim; Usman, Muhammad W.; Jafri, Fatima; Awan, Safia

2013-01-01

83

Life in the human stomach: persistence strategies of the bacterial pathogen Helicobacter pylori  

PubMed Central

The bacterial pathogen Helicobacter pylori has co-evolved with humans and colonizes roughly one half of the human population, but only causes overt gastric disease in a subset of infected hosts. In this Review, we discuss the pathogenesis of this bacterium and the mechanisms it uses to promote persistent colonization of the gastric mucosa, with a focus on recent insights into the role of the virulence factors VacA, CagA and CagL. We also describe the immunobiology of H. pylori infection and highlight how this bacterium manipulates the innate and adaptive immune systems of the host to promote its own persistence. PMID:23652324

Salama, Nina R.; Hartung, Mara L.; Muller, Anne

2013-01-01

84

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

85

Una obra uruguaya en Madrid  

E-print Network

SPRING 1986 103 Una obra uruguaya en Madrid Entre el 12 y el 15 de septiembre se ofrecieron al publico madrileño en el Centro Cultural de la Villa seis representaciones de Retrato de señora, con espejo (Vida y pasión de Margarita Xirgu). Este... sido una de las alumnas predilectas de Margarita Xirgu. Esta obra, previamente montada con éxito en Montevideo, Buenos Aires, Asunción y Barcelona, en Madrid ha sido un verdadero fracaso de taquilla, probablemente en gran medida porque ha coincidido...

Blaylock, Curtis

1986-04-01

86

Examen Final de Metodos Numericos (I. Q.) Problemas Fecha: 25 de junio de 2008 Tiempo total: 3 horas  

E-print Network

. Problema 4 [3 puntos]. En una planta desaladora de agua de mar, una parte del agua que se toma para desalar a la normal. Dicha agua se vierte previamente en un dep´osito de volumen V = 800m3, con un caudal de r1 antes de devolverla al mar, se vierte en el dep´osito agua procedente directamente del mar con un caudal

Casanellas, Marta

87

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

88

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

89

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. PMID:23043664

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

2012-01-01

90

Helicobacter pylori induced transactivation of SRE and AP-1 through the ERK signalling pathway in gastric cancer cells  

PubMed Central

BACKGROUND AND AIMS—Helicobacter pylori infection induces expression of proinflammatory cytokines such as interleukin (IL)-8 and tumour necrosis factor ? (TNF-?) in gastric mucosa, and their genes have AP-1 binding sites in the promoter region. c-Fos is important for transactivation of AP-1 which has SRE in the promoter region. We conducted this study to confirm H pylori induced transactivation of these binding sites.?METHODS—Transactivation of SRE and AP-1 was evaluated in human gastric cancer cells TMK1 and MKN45 by luciferase reporter assay in transient transfection. We compared the effects of coculture with four H pylori strains, a cag pathogenicity island (PAI) positive strain TN2, its isogenic vacA negative (TN2-?vacA) or cagE negative (TN2-?cagE) mutants, and a cag PAI negative clinical isolate T68. Phosphorylation of ERK1/2, JNK, and c-Jun was measured by immunoblot, induction of IL-8 secretion by ELISA, and the effects of MEK by inhibitor U0126.?RESULTS—Both SRE and AP-1 were transactivated by coculture with TN2. Although TN2-?vacA induced comparable transactivation, TN2-?cagE and T68 showed decreased transactivation of SRE (65% and 51%) and AP-1 (71% and 54%, respectively, of TN2). Heat killed TN2 or indirect contact using a permeable membrane inhibited transactivation. Levels of phosphorylated ERK1/2, JNK, and c-Jun were increased by coculture with TN2. MEK inhibitor U0126 reduced TN2 induced transactivation of SRE and AP1, as well as secretion of IL-8, by 83%, 87%, and 53%, respectively, of TN2.?CONCLUSIONS—Transactivation of SRE and AP-1, through ERK/MAPK and JNK/SAPK cascades, respectively, was found in gastric cancer cells cocultured with H pylori. Direct contact with viable bacteria possessing intact cag PAI is a prerequisite for the onset of intracellular signalling leading to AP-1 transactivation.???Keywords: Helicobacter pylori; SRE; AP-1; cag pathogenicity island PAI; gastric cancer PMID:11413105

Mitsuno, Y; Yoshida, H; Maeda, S; Ogura, K; Hirata, Y; Kawabe, T; Shiratori, Y; Omata, M

2001-01-01

91

Hospital volunteer can't sue employer for botched HIV test.  

PubMed

A California Court of Appeals affirmed a lower court ruling barring a hospital volunteer from bringing a medical malpractice suit against her employer, VacaValley Hospital. Volunteer [name removed] was injured as a result of an HIV antibody test. While blood was being drawn for the test, [name removed] suffered nerve damage to her right arm. She filed a claim for worker's compensation and sued the hospital for malpractice. A Circuit Court judge granted summary judgement that worker's compensation was [name removed]'s sole remedy under State law. The Court of Appeals agreed. [Name removed]'s HIV test was conducted following her on-the-job exposure to HIV and thus the procedures were provided as an employee health benefit available free of charge. In treating [name removed] was fulfilling its obligation under the protocol as her employer, not her health care provider. PMID:11364049

1996-11-29

92

The Wittliff Collection  

NSDL National Science Digital Library

Founded at Texas State University-San Marcos by Austin screenwriter and photographer Bill Wittliff and his wife Sally, the Wittliff Collections bring together "the Southwest's literature, film, and music." Visitors to the website can share in all of these cultural wonders, including materials from the Southwestern Writers Collection and several extensive photography collections. First-time visitors should head on over to "The Collections" area to take in the travel narrative of Cabeza de Vaca, found in the Southwestern Writers Collection "Research and Archives", and a wonderful tribute to the TV series and book, "Lonesome Dove". Moving on, the "Exhibitions & Events" area contains information about their various traveling exhibits, events, and writer talks. The site is rounded out by an online gift store and more details about their book series and anthologies of Southwestern writers.

93

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

PubMed Central

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, Jr, Richard M

2013-01-01

94

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

95

Why Range Forage Quality Changes (Spanish)  

E-print Network

/invierno Perenne 4-32 14-74 carga en el corto plazo en un pastizal previamente pastoreado de manera ligera o moderada, puede resultar en una menor calidad de forraje, debido a que los animales son forzados a consumir forra- je viejo o muerto. Si el potrero tiene... antecedentes de pastoreo o uso intenso, la calidad del forraje de los pastos ser? en general m?s alta, debido a que las plantas est?n menos maduras y hay menos material muerto. Estas diferencias en calidad de forraje no sig- nifican que el uso intensivo...

Lyons, Robert K.; Machen, Richard V.; Forbes, T. D. A.

2001-09-10

96

Study of Helicobacter pylori genotype status in cows, sheep, goats and human beings  

PubMed Central

Background Helicobacter pylori is one of the most controversial bacteria in the world causing diverse gastrointestinal diseases. The transmission way of this bacterium still remains unknown. The possibility of zoonotic transmission of H. pylori has been suggested, but is not proven in nonprimate reservoirs. In the current survey, we investigate the presence of H. pylori in cow, sheep and goat stomach, determine the bacterium virulence factors and finally compare the human H. pylori virulence factors and animals in order to examine whether H. pylori might be transmitted from these animals to human beings. Methods This cross- sectional study was performed on 800 gastric biopsy specimens of cows, sheep, goats and human beings. The PCR assays was performed to detection of H. pylori, vacA and cagA genes. The PCR products of Ruminant’s samples with positive H. pylori were subjected to DNA sequencing analysis. Statistical tests were applied for data analysis. Results Overall 6 (3%) cows, 32 (16%) sheep and 164 (82%) human beings specimens were confirmed to be H. pylori positive; however we were not able to detect this bacterium in all 200 goat samples. The vacA s1a/m1a was the predominant H. pylori genotype in all three kinds of studied population. There was 3.4–8.4% variability and 92.9-98.5% homology between sheep and human samples. Conclusions Considering the high sequence homology among DNA of H. pylori isolated from sheep and human, our data suggest that sheep may act as a reservoir for H. pylori and in the some extent share the ancestral host for the bacteria with human. PMID:24708464

2014-01-01

97

Comparison of Storage Capacity and Sedimentation Trends of Lago Guayabal, Puerto Rico-December 2001 and October 2006  

USGS Publications Warehouse

Lago Guayabal dam is located on the Rio Jacaguas in the municipality of Villalba in southern Puerto Rico, about 4 kilometers north of the town of Juana Diaz and about 5 kilometers south of Villalba (fig. 1). The dam is owned and operated by the Puerto Rico Electric Power Authority (PREPA) and was constructed in 1913 for the irrigation of croplands in the southern coastal plains of Puerto Rico. The reservoir impounds the waters of the Rio Jacaguas and those of the Rio Toa Vaca, when the Toa Vaca dam overflows or releases water. The reservoir has a drainage area of 53.8 square kilometers. The dam is a concrete gravity structure with a normal pool (at top of flashboards) elevation of 103.94 meters above mean sea level (Puerto Rico Electric Power Authority, 1988). During October 2006, the U.S. Geological Survey (USGS), Caribbean Water Science Center, in cooperation with the Puerto Rico Aqueduct and Sewer Authority (PRASA) conducted a bathymetric survey of Lago Guayabal to update the reservoir storage capacity and actualize the reservoir sedimentation rate by comparing the 2006 data with the previous 2001 bathymetric survey results. The purpose of this report is to describe and document the USGS sedimentation survey conducted at Lago Guayabal during October 2006, including the methods used to update the reservoir storage capacity, sedimentation rates, and areas of substantial sediment accumulation since December 2001. The Lago Guayabal sedimentation history up to 2001 was published by the USGS in 2003 (Soler-Lopez, 2003); therefore, this report focuses on the comparison between the 2001 and current bathymetric surveys of Lago Guayabal.

Soler-Lopez, Luis R.

2008-01-01

98

Analysis of Clinical Isolates of Helicobacter pylori in Pakistan Reveals High Degrees of Pathogenicity and High Frequencies of Antibiotic Resistance  

PubMed Central

Background Antibiotic resistance in Helicobacter pylori contributes to failure in eradicating the infection and is most often due to point and missense mutations in a few key genes. Methods The antibiotic susceptibility profiles of H. pylori isolates from 46 Pakistani patients were determined by Etest. Resistance and pathogenicity genes were amplified, and sequences were analyzed to determine the presence of mutations. Results A high percentage of isolates (73.9%) were resistant to metronidazole (MTZ), with considerable resistance to clarithromycin (CLR; 47.8%) and amoxicillin (AML; 54.3%) also observed. Relatively few isolates were resistant to tetracycline (TET; 4.3%) or to ciprofloxacin (CIP; 13%). However, most isolates (n = 43) exhibited resistance to one or more antibiotics. MTZ-resistant isolates contained missense mutations in oxygen-independent NADPH nitroreductase (RdxA; 8 mutations found) and NADH flavin oxidoreductase (FrxA; 4 mutations found). In the 23S rRNA gene, responsible for CLR resistance, a new point mutation (A2181G) and 4 previously reported mutations were identified. Pathogenicity genes cagA, dupA, and vacA s1a/m1 were detected frequently in isolates which were also found to be resistant to MTZ, CLR, and AML. A high percentage of CagA and VacA seropositivity was also observed in these patients. Phylogenetic analysis of partial sequences showed uniform distribution of the 3? region of cagA throughout the tree. Conclusions We have identified H. pylori isolates in Pakistan which harbor pathogenicity genes and worrying antibiotic resistance profiles as a result of having acquired multiple point and missense mutations. H. pylori eradication regimens should therefore be reevaluated in this setting. PMID:24827414

Rasheed, Faisal; Campbell, Barry James; Alfizah, Hanafiah; Varro, Andrea; Zahra, Rabaab; Yamaoka, Yoshio; Pritchard, David Mark

2014-01-01

99

Medicinal plant activity on Helicobacter pylori related diseases.  

PubMed

More than 50% of the world population is infected with Helicobacter pylori (H. pylori). The bacterium highly links to peptic ulcer diseases and duodenal ulcer, which was classified as a group?I?carcinogen in 1994 by the WHO. The pathogenesis of H. pylori is contributed by its virulence factors including urease, flagella, vacuolating cytotoxin A (VacA), cytotoxin-associated gene antigen (Cag A), and others. Of those virulence factors, VacA and CagA play the key roles. Infection with H. pylori vacA-positive strains can lead to vacuolation and apoptosis, whereas infection with cagA-positive strains might result in severe gastric inflammation and gastric cancer. Numerous medicinal plants have been reported for their anti-H. pylori activity, and the relevant active compounds including polyphenols, flavonoids, quinones, coumarins, terpenoids, and alkaloids have been studied. The anti-H. pylori action mechanisms, including inhibition of enzymatic (urease, DNA gyrase, dihydrofolate reductase, N-acetyltransferase, and myeloperoxidase) and adhesive activities, high redox potential, and hydrophilic/hydrophobic natures of compounds, have also been discussed in detail. H. pylori-induced gastric inflammation may progress to superficial gastritis, atrophic gastritis, and finally gastric cancer. Many natural products have anti-H. pylori-induced inflammation activity and the relevant mechanisms include suppression of nuclear factor-?B and mitogen-activated protein kinase pathway activation and inhibition of oxidative stress. Anti-H. pylori induced gastric inflammatory effects of plant products, including quercetin, apigenin, carotenoids-rich algae, tea product, garlic extract, apple peel polyphenol, and finger-root extract, have been documented. In conclusion, many medicinal plant products possess anti-H. pylori activity as well as an anti-H. pylori-induced gastric inflammatory effect. Those plant products have showed great potential as pharmaceutical candidates for H. pylori eradication and H. pylori induced related gastric disease prevention. PMID:25132753

Wang, Yuan-Chuen

2014-08-14

100

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

101

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. PMID:24782915

2014-01-01

102

Produccion Gaseosa del Cometa Halley: Erupciones Y Fotodisociacion del Radical OH  

NASA Astrophysics Data System (ADS)

RESUMEN:En este trabajo informamos la detecci6n de 20 erupciones en la li'nea de =18cm (1667MHz) del radical OH en el Cometa Halley.Las observaciones incluyen todos los monitoreos existentes y se extienden desde 120 dias antes del perihelio hasta 90 dias despues.Se detectan bruscos crecimientos en el flujo medido,hasta un factor 1O,seguidos por decaimientos lentos asociados con la fotodisociaci6n del OH. Se obtuvieron valores para el tiempo de vida fotoquimico del OH y del H2O basandose en el modelo desarrollado previamente por Silva(1988). Esos tiempos de vida estan de acuerdo con predicciones teoricas y con las observaciones en el Ultravioleta, y los resultados, los que son fuertemente dependientes de la velocidad heliocentrica del Coineta (variando hasta un factor 6), han sido calculados para varios rangos de velocidad entre +28 y -28 km/seg. Key wo'L :

Silva, A. M.; Mirabel, I. F.

1990-11-01

103

Diagn?stico diferencial en la encefalitis por anticuerpos contra el receptor NMDA  

PubMed Central

Resumen Introducción La encefalitis por anticuerpos contra el receptor de NMDA (NMDAR) suele desarrollarse como un síndrome característico de evolución multifásica y diagnóstico diferencial amplio. Pacientes Presentamos a 2 pacientes diagnosticadas de encefalitis por anticuerpos NMDAR con un cuadro clínico típico, pero que inicialmente señaló otras etiologías. Discusión La afectación frecuente de pacientes jóvenes con manifestaciones psiquiátricas prominentes indica frecuentemente otras consideraciones diagnósticas; las más frecuentes son las encefalitis virales, los procesos psiquiátricos y el síndrome neuroléptico maligno. Varios síndromes previamente definidos de manera parcial o descriptiva en adultos y pacientes pediátricos probablemente eran casos de encefalitis anti-NMDAR. Conclusiones La encefalitis anti-NMDAR debe considerarse en pacientes jóvenes con manifestaciones psiquiátricas subagudas, movimientos anormales y alteraciones autonómicas. La caracterización clínica e inmunológica de esta enfermedad ha llevado a la identificación de nuevos anticuerpos que afectan a procesos de memoria, aprendizaje, conducta y psicosis. PMID:20964986

Gonzalez-Valcarcel, J.; Rosenfeld, M.R.; Dalmau, J.

2011-01-01

104

Helicobacter pylori's virulence and infection persistence define pre-eclampsia complicated by fetal growth retardation  

PubMed Central

AIM: To better understand the pathogenic role of Helicobacter pylori (H. pylori) in pre-eclampsia (PE), and whether it is associated or not with fetal growth retardation (FGR). METHODS: Maternal blood samples were collected from 62 consecutive pregnant women with a diagnosis of PE and/or FGR, and from 49 women with uneventful pregnancies (controls). Serum samples were evaluated by immunoblot assay for presence of specific antibodies against H. pylori antigens [virulence: cytotoxin-associated antigen A (CagA); ureases; heat shock protein B; flagellin A; persistence: vacuolating cytotoxin A (VacA)]. Maternal complete blood count and liver enzymes levels were assessed at delivery by an automated analyzer. RESULTS: A significantly higher percentage of H. pylori seropositive women were found among PE cases (85.7%) compared to controls (42.9%, P < 0.001). There were no differences between pregnancies complicated by FGR without maternal hypertension (46.2%) and controls. Importantly, persistent and virulent infections (VacA/CagA seropositive patients, intermediate leukocyte blood count and aspartate aminotransferase levels) were exclusively associated with pre-eclampsia complicated by FGR, while virulent but acute infections (CagA positive/VacA negative patients, highest leukocyte blood count and aspartate aminotransferase levels) specifically correlated with PE without FGR. CONCLUSION: Our data strongly indicate that persistent and virulent H. pylori infections cause or contribute to PE complicated by FGR, but not to PE without feto-placental compromise. PMID:22215939

Cardaropoli, Simona; Rolfo, Alessandro; Piazzese, Annalisa; Ponzetto, Antonio; Todros, Tullia

2011-01-01

105

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

106

Helicobacter pylori and gastric cancer in the Middle East: A new enigma?  

PubMed Central

The Middle East is the home of ethnic groups from three main backgrounds: Semitic (Arabs and Jews), Indo-European (Persians and Kurdish) and Turkic (Turkish and Turkmens). Its geographic location, which has been under continuous influences from Asia, Europe and Africa, has made it an ideal site for epidemiological studies on Helicobacter pylori (H. pylori) infection and genotyping. The gastric cancer rate differs in this region from very high in Iran (26.1/105) to low in Israel (12.5/105) and very low in Egypt (3.4/105). Epidemiological studies showed that the prevalence of H. pylori is almost similar in those countries with a high level of infection in childhood. Importantly, the frequency of vacA s1 and m1 regions and cagA+ genotypes were higher in non Semitic populations who inhabit the North than Semitic populations, the inhabitants of Southern parts of the Middle East. H. pylori infection prevalence, distribution pattern of virulence factors, diet and smoking could not have explained the difference in cancer rate. This reflects the multifactorial aetiology of gastric cancer and suggests that H. pylori infection does not always directly correlate with the risk for gastrointestinal disease, such as gastric cancer. Further detailed investigations and international comparative studies of each risk factor need to be performed to investigate whether this represents a true enigma. PMID:20614477

Hussein, Nawfal R

2010-01-01

107

PA02.08. Role of herbs in psychosomatic disorders  

PubMed Central

Purpose: Stress is taking toll of the health of the people in this present competitive and challenging world. Ayurvedic acharayas have realized the role of mind on the body thousands of years ago. While mentioning the etiology of almost every disease our acharyas have mentioned the psychological factors like bhaya, shoka, kroda etc along with the physiological causes. It shows the effect of mind in causation of a disease. These psychological factors like bhaya, shoka etc when become excessive and uncontrollable they lead to manasika rogas. These manasika rogas are called as psychosomatic disorders. In Ayurveda a number of herbs have been mentioned as medhya rasayanas. The herbs like brahmi, mandookaparni, shankapuspi, aswagandha, yestimadhu, guduchi etc, have been mentioned at various contexts which work in different ways to help restore the health in psychosomatic disorders. Hence the present topic the “ROLE OF HERBS IN PSYCHOSOMATIC DISORDERS” was taken up to study the mode of action of herbs mentioned in manasika rogas. Method: The drugs mentioned by the brihatrayees under the treatment of manasika rogas like unmada and apasmara are enumerated and later the properties of most frequently mentioned herbs are studied. Result: The herbs like Brahmi, Shankapuspi act by their nootropic activity and the herbs like Lashuna, Vaca etc act by their high antioxidant property. Conclusion: The drugs by our acharyas act by their rasa, guna virya and vipaka help in the elimination of aggravated dosas their by helps the body to regain the homeostasis of tridoshas.

Ramgopal, KVRSS

2013-01-01

108

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

PubMed Central

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 ?g/ml), followed by natural skin post gastric digestion (MIC range, 128 to 512 ?g/ml), and natural almond skin post gastric plus duodenal digestion (MIC range, 256 to 512 ?g/ml). Amongst the pure flavonoid compounds, protocatechuic acid showed the greatest activity (MIC range, 128 to 512 ?g/ml) against H. pylori strains. Conclusions 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

2013-01-01

109

Differences in Genotypes of Helicobacter pylori from Different Human Populations  

PubMed Central

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution. PMID:10809702

Kersulyte, Dangeruta; Mukhopadhyay, Asish K.; Velapatino, Billie; Su, WanWen; Pan, ZhiJun; Garcia, Claudia; Hernandez, Virginia; Valdez, Yanet; Mistry, Rajesh S.; Gilman, Robert H.; Yuan, Yuan; Gao, Hua; Alarcon, Teresa; Lopez-Brea, Manuel; Balakrish Nair, G.; Chowdhury, Abhijit; Datta, Simanti; Shirai, Mutsunori; Nakazawa, Teruko; Ally, Reidwaan; Segal, Isidore; Wong, Benjamin C. Y.; Lam, S. K.; Olfat, Farzad O.; Boren, Thomas; Engstrand, Lars; Torres, Olga; Schneider, Roberto; Thomas, Julian E.; Czinn, Steven; Berg, Douglas E.

2000-01-01

110

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.

2014-10-01

111

Ulcerogenic Helicobacter pylori strains isolated from children: a contribution to get insight into the virulence of the bacteria.  

PubMed

Infection with Helicobacter pylori is the major cause for the development of peptic ulcer disease (PUD). In children, with no other etiology for the disease, this rare event occurs shortly after infection. In these young patients, habits of smoking, diet, consumption of alcohol and non-steroid anti-inflammatory drugs and stress, in addition to the genetic susceptibility of the patient, represent a minor influence. Accordingly, the virulence of the implicated H. pylori strain should play a crucial role in the development of PUD. Corroborating this, our in vitro infection assays comparing a pool of five H. pylori strains isolated from children with PUD to a pool of five other pediatric clinical isolates associated with non-ulcer dyspepsia (NUD) showed the greater ability of PUD strains to induce a marked decrease in the viability of gastric cells and to cause severe damage in the cells cytoskeleton as well as an impairment in the production/secretion of mucins. To uncover virulence features, we compared the proteome of these two groups of H. pylori strains. Two-dimensional gel electrophoresis followed by mass-spectrometry allowed us to detect 27 differentially expressed proteins between them. In addition to the presence of genes encoding well established virulence factors, namely cagA, vacAs1, oipA "on" status, homB and jhp562 genes, the pediatric ulcerogenic strains shared a proteome profile characterized by changes in the abundance of: motility-associated proteins, accounting for higher motility; antioxidant proteins, which may confer increased resistance to inflammation; and enzymes involved in key steps in the metabolism of glucose, amino acids and urea, which may be advantageous to face fluctuations of nutrients. In conclusion, the enhanced virulence of the pediatric ulcerogenic H. pylori strains may result from a synergy between their natural ability to better adapt to the hostile human stomach and the expression of the established virulence factors. PMID:22039453

Vitoriano, Inês; Saraiva-Pava, Kathy D; Rocha-Gonçalves, Alexandra; Santos, Andrea; Lopes, Ana I; Oleastro, Mónica; Roxo-Rosa, Mónica

2011-01-01

112

Clinical Relevance and Diversity of Two Homologous Genes Encoding Glycosyltransferases in Helicobacter pylori?  

PubMed Central

Helicobacter pylori is known to be a major cause of peptic ulceration. The jhp0562 gene, encoding a glycosyltransferase involved in the synthesis of the lipopolysaccharide, was associated with peptic ulcer disease (PUD) in children. The ?-(1,3)-galactosyltransferase [?-(1,3)GalT] gene (jhp0563), involved in Lewis (Le) antigen expression, is highly similar to jhp0562. The clinical significance and diversity of both genes were examined by PCR and sequencing of clinical strains (n = 117) isolated from children with PUD (n = 57) and nonulcer dyspepsia (NUD; n = 60). The prevalence of the jhp0562 gene was significantly higher in strains with a more-virulent profile (strains positive for the cag pathogenicity island [PAI], vacA sl allele, babA, homB, phase-variable gene oipA “on” [i.e., functional], and hopQ I allele). The distribution of genotypes according to clinical outcome showed that the presence of jhp0562 represented one of the greatest risks for the development of PUD. Moreover, the triple-positive genotype for the cag PAI, jhp0562, and homB provided the best discriminatory model for distinguishing PUD and NUD outcomes in children. Sequence and in vitro expression analyses of jhp0562 showed the presence of a complete open reading frame, while the ?-(1,3)GalT gene was shown to be a phase-variable gene. The regular presence of jhp0562 in strains with a truncated ?-(1,3)GalT gene suggests that jhp0562 may also be implicated in the regulation of Le antigen expression. Overall, the results of this study suggest that the jhp0562 gene is of great clinical relevance, being a useful comarker for severe H. pylori-related disease and contributing to host adaptation. PMID:20554820

Oleastro, Monica; Santos, Andrea; Cordeiro, Rita; Nunes, Baltazar; Megraud, Francis; Menard, Armelle

2010-01-01

113

Clinical relevance and diversity of two homologous genes encoding glycosyltransferases in Helicobacter pylori.  

PubMed

Helicobacter pylori is known to be a major cause of peptic ulceration. The jhp0562 gene, encoding a glycosyltransferase involved in the synthesis of the lipopolysaccharide, was associated with peptic ulcer disease (PUD) in children. The beta-(1,3)-galactosyltransferase [beta-(1,3)GalT] gene (jhp0563), involved in Lewis (Le) antigen expression, is highly similar to jhp0562. The clinical significance and diversity of both genes were examined by PCR and sequencing of clinical strains (n = 117) isolated from children with PUD (n = 57) and nonulcer dyspepsia (NUD; n = 60). The prevalence of the jhp0562 gene was significantly higher in strains with a more-virulent profile (strains positive for the cag pathogenicity island [PAI], vacA sl allele, babA, homB, phase-variable gene oipA "on" [i.e., functional], and hopQ I allele). The distribution of genotypes according to clinical outcome showed that the presence of jhp0562 represented one of the greatest risks for the development of PUD. Moreover, the triple-positive genotype for the cag PAI, jhp0562, and homB provided the best discriminatory model for distinguishing PUD and NUD outcomes in children. Sequence and in vitro expression analyses of jhp0562 showed the presence of a complete open reading frame, while the beta-(1,3)GalT gene was shown to be a phase-variable gene. The regular presence of jhp0562 in strains with a truncated beta-(1,3)GalT gene suggests that jhp0562 may also be implicated in the regulation of Le antigen expression. Overall, the results of this study suggest that the jhp0562 gene is of great clinical relevance, being a useful comarker for severe H. pylori-related disease and contributing to host adaptation. PMID:20554820

Oleastro, Mónica; Santos, Andrea; Cordeiro, Rita; Nunes, Baltazar; Mégraud, Francis; Ménard, Armelle

2010-08-01

114

Ulcerogenic Helicobacter pylori Strains Isolated from Children: A Contribution to Get Insight into the Virulence of the Bacteria  

PubMed Central

Infection with Helicobacter pylori is the major cause for the development of peptic ulcer disease (PUD). In children, with no other etiology for the disease, this rare event occurs shortly after infection. In these young patients, habits of smoking, diet, consumption of alcohol and non-steroid anti-inflammatory drugs and stress, in addition to the genetic susceptibility of the patient, represent a minor influence. Accordingly, the virulence of the implicated H. pylori strain should play a crucial role in the development of PUD. Corroborating this, our in vitro infection assays comparing a pool of five H. pylori strains isolated from children with PUD to a pool of five other pediatric clinical isolates associated with non-ulcer dyspepsia (NUD) showed the greater ability of PUD strains to induce a marked decrease in the viability of gastric cells and to cause severe damage in the cells cytoskeleton as well as an impairment in the production/secretion of mucins. To uncover virulence features, we compared the proteome of these two groups of H. pylori strains. Two-dimensional gel electrophoresis followed by mass-spectrometry allowed us to detect 27 differentially expressed proteins between them. In addition to the presence of genes encoding well established virulence factors, namely cagA, vacAs1, oipA “on” status, homB and jhp562 genes, the pediatric ulcerogenic strains shared a proteome profile characterized by changes in the abundance of: motility-associated proteins, accounting for higher motility; antioxidant proteins, which may confer increased resistance to inflammation; and enzymes involved in key steps in the metabolism of glucose, amino acids and urea, which may be advantageous to face fluctuations of nutrients. In conclusion, the enhanced virulence of the pediatric ulcerogenic H. pylori strains may result from a synergy between their natural ability to better adapt to the hostile human stomach and the expression of the established virulence factors. PMID:22039453

Vitoriano, Ines; Saraiva-Pava, Kathy D.; Rocha-Goncalves, Alexandra; Santos, Andrea; Lopes, Ana I.; Oleastro, Monica; Roxo-Rosa, Monica

2011-01-01

115

Phase Variation in the Helicobacter pylori Phospholipase A Gene and Its Role in Acid Adaptation  

PubMed Central

Previously, we have shown that Helicobacter pylori can spontaneously and reversibly change its membrane lipid composition, producing variants with low or high content of lysophospholipids. The “lyso” variant contains a high percentage of lysophospholipids, adheres better to epithelial cells, and releases more proteins such as urease and VacA, compared to the “normal” variant, which has a low content of lysophospholipids. Prolonged growth of the normal variant at pH 3.5, but not under neutral conditions, leads to enrichment of lyso variant colonies, suggesting that the colony switch is relevant to acid adaptation. In this study we show that the change in membrane lipid composition is due to phase variation in the pldA gene. A change in the (C) tract length of this gene results in reversible frameshifts, translation of a full-length or truncated pldA, and the production of active or inactive outer membrane phospholipase A (OMPLA). The role of OMPLA in determining the colony morphology was confirmed by the construction of an OMPLA-negative mutant. Furthermore, variants with an active OMPLA were able to survive acidic conditions better than variants with the inactive form. This explains why the lyso variant is selected at low pH. Our studies demonstrate that phase variation in the pldA gene, resulting in an active form of OMPLA, is important for survival under acidic conditions. We also demonstrated the active OMPLA genotype in fresh isolates of H. pylori from patients referred to gastroscopy for dyspepsia. PMID:11705905

Tannaes, Tone; Dekker, Niek; Bukholm, Geir; Bijlsma, Jetta J. E.; Appelmelk, Ben J.

2001-01-01

116

Comparative Whole Genome Sequence Analysis of the Carcinogenic Bacterial Model Pathogen Helicobacter felis  

PubMed Central

The gram-negative bacterium Helicobacter felis naturally colonizes the gastric mucosa of dogs and cats. Due to its ability to persistently infect laboratory mice, H. felis has been used extensively to experimentally model gastric disorders induced in humans by H. pylori. We determined the 1.67 Mb genome sequence of H. felis using combined Solexa and 454 pyrosequencing, annotated the genome, and compared it with multiple previously published Helicobacter genomes. About 1,063 (63.6%) of the 1,671 genes identified in the H. felis genome have orthologues in H. pylori, its closest relative among the fully sequenced Helicobacter species. Many H. pylori virulence factors are shared by H. felis: these include the gamma-glutamyl transpeptidase GGT, the immunomodulator NapA, and the secreted enzymes collagenase and HtrA. Helicobacter felis lacks a Cag pathogenicity island and the vacuolating cytotoxin VacA but possesses a complete comB system conferring natural competence. Remarkable features of the H. felis genome include its paucity of transcriptional regulators and an extraordinary abundance of chemotaxis sensors and restriction/modification systems. Helicobacter felis possesses an episomally replicating 6.7-kb plasmid and harbors three chromosomal regions with deviating GC content. These putative horizontally acquired regions show homology and synteny with the recently isolated H. pylori plasmid pHPPC4 and homology to Campylobacter bacteriophage genes (transposases, structural, and lytic genes), respectively. In summary, the H. felis genome harbors a variety of putative mobile elements that are unique among Helicobacter species and may contribute to this pathogen’s carcinogenic properties. PMID:21402865

Arnold, Isabelle C.; Zigova, Zuzana; Holden, Matthew; Lawley, Trevor D.; Rad, Roland; Dougan, Gordon; Falkow, Stanley; Bentley, Stephen D.; Muller, Anne

2011-01-01

117

Helicobacter hepaticus, a new pathogenic species of the Helicobacter genus: Similarities and differences with H. pylori  

PubMed Central

Helicobacter hepaticus was discovered in 1992 as a cause of liver cancer in the A/JCr mouse model. In susceptible mice, infection by H. hepaticus causes chronic gastrointestinal inflammation leading to neoplasia. It can also cause morphological changes in breast-glands leading to neoplasm and adenocarcinoma in mouse models. Studies performed on humans have revealed that H. hepaticus may also be a human pathogen since infection by H. hepaticus can be associated with cholecystitis, cholelithiasis and gallbladder cancer. H. hepaticus is a close relative of H. pylori, but it lacks the major virulence factors of H. pylori including vacoulating cytotoxin A (VacA) and cytotoxin associated gene (cagA). Moreover, SabA, AlpA, and BabA, three important adhesin proteins of H. pylori, are absent in its genome. In contrast, the genome of H. hepaticus contains genes encoding some orthologus virulence factors of Campylobacter jejuni such as cytolethal distending toxin (CDT), and PebI adhesin factor. Other genes including 16S rRNA, 18 KDa immunogenic protein, and urease structural subunits are related to H. pylori. Its genome contains a small island consisting of 71 Kbp named HHGI1, which probably encodes a secretion system type IV (T4SS), and some other virulence factors. As far as the immunogenic antigens are concerned, the lipopolysaccharide (LPS) and flagellin of H. hepaticus are weak stimulants of the immune system, while pro-inflammatory responses are mainly induced by its lipoproteins and most likely by the peptidoglycan. Concerning the multidrug efflux pumps, a homologue of H. pylori TolC, HefA, has been observed in H. hepaticus which contributes to resistance to amoxicillin and bile acids. PMID:24475322

Falsafi, Tahereh; Mahboubi, Mohaddese

2013-01-01

118

Soluble extracts from Helicobacter pylori induce dome formation in polarized intestinal epithelial monolayers in a laminin-dependent manner.  

PubMed

Helicobacter pylori colonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts from H. pylori. The extracts induced rapid "dome" formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate. H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding alpha 6 beta 4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific to H. pylori and independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements from H. pylori can alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response. PMID:12819097

Terrés, A M; Windle, H J; Ardini, E; Kelleher, D P

2003-07-01

119

Storage capacity and sedimentation trends of Lago Garzas, Puerto Rico, 1996-2007  

USGS Publications Warehouse

Lago Garzas is located in west-central Puerto Rico, about 3.5 kilometers southwest of the town of Adjuntas, in the confluence of the Río Vacas and three other unnamed tributaries (fig. 1). The dam is owned and operated by the Puerto Rico Electric Power Authority (PREPA), and was constructed in 1943 for hydroelectric power generation and municipal water use along the southern coast. The dam is a semi-hydraulic earthfill embankment lined with boulders, and has a height of 61.57 meters, a top width of 9.14 meters, a base width of 365.76 meters, and a crest length of 227.37 meters; State Road PR-518 crosses the top of the dam. A morning-glory-type spillway is located near the west abutment of the dam at an elevation of 736.12 meters above mean sea level (Puerto Rico Water Resources Authority, 1969). Figure 2 shows an aerial photograph of the Lago Garzas earthfill dam and the morning-glory spillway section. Additional information and operational procedures are provided in Soler-López and others (1999). During July 17-18, 2007, the U.S. Geological Survey (USGS) Caribbean Water Science Center, in cooperation with the Puerto Rico Aqueduct and Sewer Authority, conducted a bathymetric survey of Lago Garzas to update the reservoir storage capacity and update the reservoir sedimentation rate by comparing the 2007 data with the previous 1996 bathymetric survey results. The purpose of this report is to describe and document the USGS sedimentation survey conducted at Lago Garzas during July 2007, including the methods used to update the reservoir storage capacity, sedimentation rates, and areas of substantial sediment accumulation since 1996.

Soler-Lopez, L.R.

2012-01-01

120

Comparative genomics and proteomics of Helicobacter mustelae, an ulcerogenic and carcinogenic gastric pathogen  

PubMed Central

Background Helicobacter mustelae causes gastritis, ulcers and gastric cancer in ferrets and other mustelids. H. mustelae remains the only helicobacter other than H. pylori that causes gastric ulceration and cancer in its natural host. To improve understanding of H. mustelae pathogenesis, and the ulcerogenic and carcinogenic potential of helicobacters in general, we sequenced the H. mustelae genome, and identified 425 expressed proteins in the envelope and cytosolic proteome. Results The H. mustelae genome lacks orthologs of major H. pylori virulence factors including CagA, VacA, BabA, SabA and OipA. However, it encodes ten autotransporter surface proteins, seven of which were detected in the expressed proteome, and which, except for the Hsr protein, are of unknown function. There are 26 putative outer membrane proteins in H. mustelae, some of which are most similar to the Hof proteins of H. pylori. Although homologs of putative virulence determinants of H. pylori (NapA, plasminogen adhesin, collagenase) and Campylobacter jejuni (CiaB, Peb4a) are present in the H. mustelae genome, it also includes a distinct complement of virulence-related genes including a haemagglutinin/haemolysin protein, and a glycosyl transferase for producing blood group A/B on its lipopolysaccharide. The most highly expressed 264 proteins in the cytosolic proteome included many corresponding proteins from H. pylori, but the rank profile in H. mustelae was distinctive. Of 27 genes shown to be essential for H. pylori colonization of the gerbil, all but three had orthologs in H. mustelae, identifying a shared set of core proteins for gastric persistence. Conclusions The determination of the genome sequence and expressed proteome of the ulcerogenic species H mustelae provides a comparative model for H. pylori to investigate bacterial gastric carcinogenesis in mammals, and to suggest ways whereby cag minus H. pylori strains might cause ulceration and cancer. The genome sequence was deposited in EMBL/GenBank/DDBJ under accession number FN555004. PMID:20219135

2010-01-01

121

Electron Microscopic, Genetic and Protein Expression Analyses of Helicobacter acinonychis Strains from a Bengal Tiger  

PubMed Central

Colonization by Helicobacter species is commonly noted in many mammals. These infections often remain unrecognized, but can cause severe health complications or more subtle host immune perturbations. The aim of this study was to isolate and characterize putative novel Helicobacter spp. from Bengal tigers in Thailand. Morphological investigation (Gram-staining and electron microscopy) and genetic studies (16SrRNA, 23SrRNA, flagellin, urease and prophage gene analyses, RAPD DNA fingerprinting and restriction fragment polymorphisms) as well as Western blotting were used to characterize the isolated Helicobacters. Electron microscopy revealed spiral-shaped bacteria, which varied in length (2.5–6 µm) and contained up to four monopolar sheathed flagella. The 16SrRNA, 23SrRNA, sequencing and protein expression analyses identified novel H. acinonychis isolates closely related to H. pylori. These Asian isolates are genetically very similar to H. acinonychis strains of other big cats (cheetahs, lions, lion-tiger hybrid and other tigers) from North America and Europe, which is remarkable in the context of the great genetic diversity among worldwide H. pylori strains. We also found by immunoblotting that the Bengal tiger isolates express UreaseA/B, flagellin, BabA adhesin, neutrophil-activating protein NapA, HtrA protease, ?-glutamyl-transpeptidase GGT, Slt lytic transglycosylase and two DNA transfer relaxase orthologs that were known from H. pylori, but not the cag pathogenicity island, nor CagA, VacA, SabA, DupA or OipA proteins. These results give fresh insights into H. acinonychis genetics and the expression of potential pathogenicity-associated factors and their possible pathophysiological relevance in related gastric infections. PMID:23940723

Tegtmeyer, Nicole; Rivas Traverso, Francisco; Rohde, Manfred; Oyarzabal, Omar A.; Lehn, Norbert; Schneider-Brachert, Wulf; Ferrero, Richard L.; Fox, James G.; Berg, Douglas E.; Backert, Steffen

2013-01-01

122

The co-evolved Helicobacter pylori and gastric cancer: trinity of bacterial virulence, host susceptibility and lifestyle.  

PubMed

Helicobacter pylori is an important yet unproven etiological agent of gastric cancer. H. pylori infection is more prevalent in developing Asian countries like India and it is usually acquired at an early age. It has been two decades since Marshall and Warren (1984) first described curved bacilli in the stomach of ulcer and gastritis patients. This discovery has won them the Nobel Prize recently, but the debate whether H. pylori is a pathogen or a commensal organism is still hot. Associations with disease-specific factors remain elusive years after the genome sequences were made available. Cytotoxin-associated antigen A (CagA) and the so-called plasticity region cluster genes are implicated in pathogenesis of the carcinoma of stomach. Another virulence factor VacA whose role is still debatable, has recently been projected in pathology of gastric cancer. Studies of the evolution through genetic variation in H. pylori populations have provided a window into the history of human population migrations and a possible co-evolution of this pathogen with its human host. Possible symbiotic relationships were seriously debated since the discovery of this pathogen. The debate has been further intensified as some studies proposed H. pylori infection to be beneficial in some humans. In this commentary, we attempt to briefly discuss about H. pylori as a human pathogen, and some of the important issues linked to its pathophysiology in different hosts. 'We dance around in a ring and suppose, the secret sits in the middle and knows'--Robert Frost. PMID:17201930

Akhter, Yusuf; Ahmed, Irshad; Devi, S Manjulata; Ahmed, Niyaz

2007-01-01

123

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. PMID:24006137

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

124

Helicobacter pylori isolates from Greek children express type 2 and type 1 Lewis and ?1,6-glucan antigens in conjunction with a functional type IV secretion system.  

PubMed

Helicobacter pylori infection is often acquired in childhood and can persist for life. Previous studies in adult patients have shown that H. pylori isolates from North American and European hosts express predominantly type 2 Lewis x (Le(x)) and Le(y) epitopes, while Asian strains have the capacity to express type 1 Le(a) and Le(b) structures. In order to understand the influence of environmental and host factors on the expression of Le antigens, we analysed 50 Greek H. pylori isolates from symptomatic children. Both CagA-positive and -negative strains were evaluated. The expression of Le antigens was determined by whole-cell indirect ELISA (WCE), and LPS profiles were assessed by gel electrophoresis and immunoblotting. Occurrence of Le(x) and/or Le(y) antigens was confirmed in 35 of the isolates (70?%) while 15 of the isolates were non-typable. It was found that 11 of the paediatric isolates had the propensity to express type 1 Le(b) blood-group antigen (22?%), a feature relatively uncommon in H. pylori isolates from adults. One strain expressed both Le(b) and Le(a) antigens. The majority of the isolates (49/50, 98?%) expressed ?1,6-glucan, an antigenic non-Le determinant present in the outer core region of H. pylori LPS. All Le(x)- and Le(y)-expressing strains also carried a functional cag pathogenicity island-encoding a type IV secretion system, capable of translocating CagA protein, as well as the vacAs1 allele, suggesting that Le(x) and Le(y) epitopes may aid the persistence of more aggressive strains. No association between bacterial virulence characteristics and the histopathological observations was evident. PMID:22160312

Altman, Eleonora; Chandan, Vandana; Harrison, Blair A; Panayotopoulou, Effrosini G; Roma-Giannikou, Eleftheria; Li, Jianjun; Sgouras, Dionyssios N

2012-04-01

125

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

126

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. PMID:22197766

Suzuki, Rumiko; Shiota, Seiji; Yamaoka, Yoshio

2012-01-01

127

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

128

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

129

Concurrent genotyping of Helicobacter pylori virulence genes and human cytokine SNP sites using whole genome amplified DNA derived from minute amounts of gastric biopsy specimen DNA  

PubMed Central

Background Bacterial and cellular genotyping is becoming increasingly important in the diagnosis of infectious diseases. However, difficulties in obtaining sufficient amount of bacterial and cellular DNA extracted from the same human biopsy specimens is often a limiting factor. In this study, total DNA (host and bacterial DNA) was isolated from minute amounts of gastric biopsy specimens and amplified by means of whole genome amplification using the multiple displacement amplification (MDA) technique. Subsequently, MDA-DNA was used for concurrent Helicobacter pylori and human host cellular DNA genotyping analysis using PCR-based methods. Results Total DNA was isolated from gastric biopsy specimens of 12 subjects with gastritis and 16 control subjects having a normal mucosa. The DNA was amplified using a multiple displacement amplification (MDA) kit. Next, concurrent genotyping was performed using H. pylori-specific virulence gene PCR amplification assays, pyrosequencing of bacterial 16S rDNA and PCR characterisation of various host genes. This includes Interleukin 1-beta (IL1B) and Interferon-gamma receptor (IFNGR1) SNP analysis, and Interleukin-1 receptor antagonist (IL1RN) variable tandem repeats (VNTR) in intron 2. Finally, regions of the vacA-gene were PCR amplified using M13-sequence tagged primers which allowed for direct DNA sequencing, omitting cloning of PCR amplicons. H. pylori specific multiplex PCR assays revealed the presence of H. pylori cagA and vacA genotypic variations in 11 of 12 gastritis biopsy specimens. Using pyrosequencing, 16S rDNA variable V3 region signatures of H. pylori were found in 11 of 12 individuals with gastritis, but in none of the control subjects. Similarly, IL1B and IFNGR1-SNP and IL1RN-VNTR patterns could be established in all individuals. Furthermore, sequencing of M13-sequence tagged vacA-PCR amplicons revealed the presence of highly diverse H. pylori vacA-s/i/m regions. Conclusion The PCR-based molecular typing methods applied, using MDA-amplified DNA derived from small amounts of gastric biopsy specimens, enabled a rapid and concurrent molecular analysis of bacterial and host genes in the same biopsy specimen. The principles and technologies used in this study could also be applied to any situation in which human host and microbial genes of interest in microbial-host interactions would need to be sequenced. PMID:18842150

Ryberg, Anna; Borch, Kurt; Sun, Yi-Qian; Monstein, Hans-Jurg

2008-01-01

130

Mucosal polymerase chain reaction for diagnosing Helicobacter pylori infection in patients with bleeding peptic ulcers  

PubMed Central

AIM: Helicobacter pylori (H pylori) has been linked to chronic gastritis, peptic ulcers, gastric cancer and MALT-lymphoma. Conventional invasive tests are less sensitive than non-invasive tests in diagnosing H pylori infection in patients with bleeding peptic ulcers. Polymerase chain reaction is a sensitive and accurate method for diagnosing H pylori infection. The aim of this study was to evaluate the diagnostic role of mucosal polymerase chain reaction for H pylori infection in patients with bleeding peptic ulcers. METHODS: In patients with bleeding, non-bleeding peptic ulcers and chronic gastritis, we checked rapid urease test, histology, bacterial culture and mucosal polymerase chain reaction for detecting H pylori infection. Positive H pylori infection was defined as positive culture or both a positive histology and a positive rapid urease test. For mucosal polymerase chain reaction of H pylori, we checked vacA (s1a, s1b, s1c, s2, m1, m1T, m2), iceA1, iceA2 and cag A. RESULTS: Between October 2000 and April 2002, 88 patients with bleeding peptic ulcers (males/females: 60/28, gastric ulcers/duodenal ulcers: 55/33), 81 patients with non-bleeding peptic ulcers (males/females: 54/27, gastric ulcers/duodenal ulcers: 45/36) and 37 patients with chronic gastritis (males/females: 24/13) were enrolled in this study. In patients with bleeding peptic ulcers, non-bleeding peptic ulcers and chronic gastritis, 45 patients (51%), 71 patients (88%) and 20 patients (54%) respectively were found to have positive H pylori infection (P<0.001). In patients with bleeding peptic ulcers, non-bleeding peptic ulcers and chronic gastritis, polymerase chain reaction for H pylori infection was positive in 54 patients (61%), 70 patients (86%) and 20 patients (54%) respectively (P<0.001). The sensitivity, positive predictive value and diagnostic accuracy of mucosal polymerase reaction for H pylori infection were significantly lower in patients with bleeding peptic ulcers (84%, 79% and 81%) than in patients with non-bleeding peptic ulcers (99%, 99% and 98%) (P<0.001, P<0.01 and P<0.001 respectively). The sensitivity, negative predictive value and diagnostic accuracy of mucosal polymerase reaction for H pylori were significantly lower in patients with bleeding peptic ulcers (84%, 83% and 81%) than in patients with chronic gastritis (100%, 100% and 100%) (P = 0.02, P = 0.02 and P = 0.001). CONCLUSION: Mucosal polymerase chain reaction for detecting H pylori infection is not reliable in patients with bleeding peptic ulcers. PMID:15637749

Lin, Hwai-Jeng; Lo, Wen-Ching; Perng, Chin-Lin; Tseng, Guan-Ying; Li, Anna Fen-Yau; Ou, Yueh-Hsing

2005-01-01

131

Latitudinal Discontinuity in Thermal Conditions along the Nearshore of Central-Northern Chile.  

PubMed

Over the past decade, evidence of abrupt latitudinal changes in the dynamics, structure and genetic variability of intertidal and subtidal benthic communities along central-northern Chile has been found consistently at 30-32°S. Changes in the advective and thermal environment in nearshore waters have been inferred from ecological patterns, since analyses of in situ physical data have thus far been missing. Here we analyze a unique set of shoreline temperature data, gathered over 4-10 years at 15 sites between 28-35°S, and combine it with satellite-derived winds and sea surface temperatures to investigate the latitudinal transition in nearshore oceanographic conditions suggested by recent ecological studies. Our results show a marked transition in thermal conditions at 30-31°S, superimposed on a broad latitudinal trend, and small-scale structures associated with cape-and-bay topography. The seasonal cycle dominated temperature variability throughout the region, but its relative importance decreased abruptly south of 30-31°S, as variability at synoptic and intra-seasonal scales became more important. The response of shoreline temperatures to meridional wind stress also changed abruptly at the transition, leading to a sharp drop in the occurrence of low-temperature waters at northern sites, and a concurrent decrease in corticated algal biomass. Together, these results suggest a limitation of nitrate availability in nearshore waters north of the transition. The localized alongshore change results from the interaction of latitudinal trends (e.g., wind stress, surface warming, inertial period) with a major headland-bay system (Punta Lengua de Vaca at 30.25°S), which juxtaposes a southern stretch of coast characterized by upwelling with a northern stretch of coast characterized by warm surface waters and stratification. This transition likely generates a number of latitude-dependent controls on ecological processes in the nearshore that can explain species-specific effects, and add strength to the suggestion of an oceanography-driven, major spatial transition in coastal communities at 30-31°S. PMID:25334020

Tapia, Fabian J; Largier, John L; Castillo, Manuel; Wieters, Evie A; Navarrete, Sergio A

2014-01-01

132

Latitudinal Discontinuity in Thermal Conditions along the Nearshore of Central-Northern Chile  

PubMed Central

Over the past decade, evidence of abrupt latitudinal changes in the dynamics, structure and genetic variability of intertidal and subtidal benthic communities along central-northern Chile has been found consistently at 30–32°S. Changes in the advective and thermal environment in nearshore waters have been inferred from ecological patterns, since analyses of in situ physical data have thus far been missing. Here we analyze a unique set of shoreline temperature data, gathered over 4–10 years at 15 sites between 28–35°S, and combine it with satellite-derived winds and sea surface temperatures to investigate the latitudinal transition in nearshore oceanographic conditions suggested by recent ecological studies. Our results show a marked transition in thermal conditions at 30–31°S, superimposed on a broad latitudinal trend, and small-scale structures associated with cape-and-bay topography. The seasonal cycle dominated temperature variability throughout the region, but its relative importance decreased abruptly south of 30–31°S, as variability at synoptic and intra-seasonal scales became more important. The response of shoreline temperatures to meridional wind stress also changed abruptly at the transition, leading to a sharp drop in the occurrence of low-temperature waters at northern sites, and a concurrent decrease in corticated algal biomass. Together, these results suggest a limitation of nitrate availability in nearshore waters north of the transition. The localized alongshore change results from the interaction of latitudinal trends (e.g., wind stress, surface warming, inertial period) with a major headland-bay system (Punta Lengua de Vaca at 30.25°S), which juxtaposes a southern stretch of coast characterized by upwelling with a northern stretch of coast characterized by warm surface waters and stratification. This transition likely generates a number of latitude-dependent controls on ecological processes in the nearshore that can explain species-specific effects, and add strength to the suggestion of an oceanography-driven, major spatial transition in coastal communities at 30–31°S. PMID:25334020

Tapia, Fabian J.; Largier, John L.; Castillo, Manuel; Wieters, Evie A.; Navarrete, Sergio A.

2014-01-01

133

Variations in water clarity and bottom albedo in Florida Bay from 1985 to 1997  

USGS Publications Warehouse

Following extensive seagrass die-offs of the late 1980s and early 1990s, Florida Bay reportedly had significant declines in water clarity due to turbidity and algal blooms. Scant information exists on the extent of the decline, as this bay was not investigated for water quality concerns before the die-offs and limited areas were sampled after the primary die-off. We use imagery from the Advanced Very High Resolution Radiometer (AVHRR) to examine water clarity in Florida Bay for the period 1985 to 1997. The AVHRR provides data on nominal water reflectance and estimated fight attenuation, which are used here to describe turbidity conditions in the bay on a seasonal basis. In situ observations on changes in seagrass abundance within the bay, combined with the satellite data, provide additional insights into losses of seagrass. The imagery shows an extensive region to the west of Florida Bay having increased reflectance and fight attenuation in both winter and summer beginning in winter of 1988. These increases are consistent with a change from dense seagrass to sparse or negligible cover. Approximately 200 km2 of these offshore seagrasses may have been lost during the primary die-off (1988 through 1991), significantly more than in the bay. The imagery shows the distribution and timing of increased turbidity that followed the die-offs in the northwestern regions of the bay, exemplified in Rankin Lake and Johnson Key Basin, and indicates that about 200 km2 of dense seagrass may have been lost or severely degraded within the bay from the start of the die-off. The decline in water clarity has continued in the northwestern bay since 1991. The area west of the Everglades National Park boundaries has shown decreases in both winter turbidity and summer reflectances, suggestive of partial seagrass recovery. Areas of low reflectance associated with a major Syringodium filiforme seagrass meadow north of Marathon (Vaca Key, in the Florida Keys) appear to have expanded westward toward Big Pine Key, indicating changes in the bottom cover from before the die-off. The southern and eastern sections of the Bay have not shown significant changes in water clarity or bottom albedo throughout the entire time period.

Stumpf, R. P.; Frayer, M. L.; Durako, M. J.; Brock, J. C.

1999-01-01

134

Paleogene and Neogene magmatism in the Valle del Cura region: New perspective on the evolution of the Pampean flat slab, San Juan province, Argentina  

NASA Astrophysics Data System (ADS)

The Valle del Cura region is characterized by a thick volcanic and volcaniclastic sequence that records the Tertiary arc and backarc magmatic evolution of the Argentine Main Cordillera over the modern Pampean flatslab at 29.5-30°S. During the Eocene, a retroarc basin developed, represented by the Valle del Cura Formation synorogenic volcanosedimentary sequence, which includes rhyolites and dacitic tuffs. These silicic volcanic rocks have weak arc chemical signatures and high lithophile element concentrations and are isotopically enriched relative to the late Oligocene-early Miocene volcanic rocks that followed them. Their chemical characteristics fit with eruption through a thin crust. The Valle de Cura Formation was followed by the Oligocene-early Miocene Doña Ana Group volcanic sequence, which erupted at and near the arc front west of the border with Chile. The Doña Ana Group volcanic rocks have calc-alkaline chemical characteristics consistent with parental magmas forming in a mantle wedge and erupting through a normal thickness crust (35 km). Subsequent shallowing of the downgoing Nazca plate caused the volcanic front to migrate eastward. The volcanic sequences of the middle Miocene Cerro de las Tórtolas Formation erupted at this new arc front, essentially at the Argentine border. Two stages are recognized: an older one (16-14 Ma) in which magmas appear to have erupted through a normal thickness crust (30-35 km) and a younger one (13-10 Ma) in which the steeper REE pattern suggests the magmas last equilibrated with higher pressure residual mineral assemblages in a thicker crust. Isotopic ratios in the younger group are consistent with an increase in original crustal components and crust introduced into the mantle source by forearc subduction erosion. A peak in forearc subduction erosion near 12-10 Ma is consistent with when the main part of the Juan Fernandez Ridge began to subduct beneath the region. In addition to late Miocene Tambo Formation dacitic ignimbrites, the younger Cerro de las Tórtolas Formation volcanic rocks erupted at the height of contractional deformation in the Valle del Cura and to the east. The last important volcanic sequence to erupt in the Valle del Cura is the late Miocene Vacas Heladas Ignimbrite, the most isotopically enriched Tertiary magmas in the Valle del Cura that contain the highest proportion of crustal components. Subsequently volcanism ceased in the region in response to shallowing of the subduction zone.

Litvak, Vanesa D.; Poma, Stella; Kay, Suzanne Mahlburg

2007-09-01

135

Ecology, distribution, harvest, and conservation of the Amazonian manatee, Trichechus inunguis, in Ecuador  

E-print Network

Recent summaries of the distribution of the Amazonian manatee Trichechus inunguis record specimens from much of the Central Amazon Basin in Brazil, eastern Peru, and extreme southeastern Colombia, but not Ecuador. During October and November of 1983...Recientes sumarios de la distribución de los manaties amazónicos Trichechus inunguis registran especimenes de la mayor parte de la cuenca amazónica en Brasil, el oriente de Peru, y el suroriente de Colombia, pero no de Ecuador. Durante octubre y noviembre de 1983 nosotros fuimos en busca de manaties en los sistemas de los rios Aguarico y Cuyabeno de la Provincia del Napo, Ecuador oriental. Aqui documentamos la existencia de manaties amazónicos en Ecuador, proveemos estimaciones aproximadas de su actual distribución, describimos varios aspectos de su ecologia en Ecuador, documentamos el uso de manaties por gentes indigenas, y documentamos la cosecha comercial actual de manaties para carne. Manaties feuron observados por nosotros en varias localidades separadas en las tierras bajas del Ecuador oriental. Adicionalmente, reportamos varias observaciones por otros, asi como tambien registros históricos publicados que fueron previamente pasados por alto. Nuestras observaciones de manaties son de habitaciones en aguas negras en selva iluviosa primaria no alterada de tierras bajas, en aguas con un pH de 5.5 a 6.0 y temperatura de 25.0 a 30.7C. En la región del alto Cuyabeno, los indios de la tribu Siona, quienes han cosechado manaties por generaciones, se han impuesto asi mismos prohibiciones en la caza de manaties en Ecuador y tierras adyacentes de Peru. La mayoria de la carne obtenida es usada por los militares ya sea ecuatorianos o peruanos. Nosotros encontramos abundantes manaties sólo en una localidad, la Laguna Lagarto Cocha. Sin embargo, esta población esta siendo activamente cazada, y la carne es vendida a los destacamentos militares del lugar. Estimamos que si el nivel actual de caza continua al mismo ritmo los manaties amazónicos habran desaparecido del Ecuador en unos 10 a 15 anios....

Timm, Robert M.; Albuja V., Luis; Clauson, Barbara L.

1986-01-01

136

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