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David Y Graham

Publications and source records attributed to David Y Graham.

103 records · Page 6Linked to original sources
PubMed2002

Helicobacter pylori impairs DNA mismatch repair in gastric epithelial cells.

BACKGROUND & AIMS: Helicobacter pylori infection is a major gastric cancer risk factor. H. pylori gastritis occurs more frequently in individuals with microsatellite instability-positive than those with microsatellite instability-negative gastric cancers, raising the possibility that H. pylori infection affects DNA mismatch repair (MMR). The aim of this study was to determine the effect of H. pylori on the expression of DNA MMR proteins and RNA in gastric epithelial cells. METHODS: Gastric cancer cell lines were cocultured with H. pylori, bacterial extracts, and Campylobacter jejuni or Escherichia coli. MutS (hMSH2 and hMSH6) and MutL (hMLH1, hPMS2, and hPMS1) DNA MMR protein and RNA levels were determined. RESULTS: All cell lines examined showed decreased levels of MutS and MutL DNA MMR proteins in a dose-dependent manner after coculture with H. pylori strains. The reduction in DNA MMR protein levels was caused by heat-sensitive H. pylori products. The levels of DNA MMR proteins were affected by C. jejuni but not by E. coli. RNA levels of hMSH2 and hMSH6 were also reduced after exposure to H. pylori. CONCLUSIONS: H. pylori infection of gastric epithelial cells leads to a decrease in DNA MMR proteins that is at least in part related to an H. pylori-induced decrease in messenger RNA levels of repair genes. These data suggest that H. pylori infection might lead to a deficiency of DNA MMR in gastric epithelial cells that may increase the risk of mutation accumulation in gastric mucosa cells and the risk of gastric cancer during chronic H. pylori infection.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Importance of Helicobacter pylori oipA in clinical presentation, gastric inflammation, and mucosal interleukin 8 production.

BACKGROUND & AIMS: Disease-associated virulence factors of Helicobacter pylori may not be independent of one another. The aim was to determine which H. pylori virulence factor(s) was the most important predictor of severity of gastric inflammation or clinical outcome. METHODS: cag Pathogenicity island (PAI), vacA babA2, and iceA status were determined by polymerase chain reaction (PCR). oipA functionality was based on switch status determined by PCR-based sequencing. A backward stepwise multiple regression analysis was performed to determine which factor(s) was the most discriminating for clinical outcome as well as the relationship to mucosal histology (H. pylori density, neutrophil infiltration, intestinal metaplasia, and gastric atrophy) and mucosal interleukin 8 (IL-8) production. RESULTS: H. pylori were obtained from 247 patients (86 with gastritis, 86 with duodenal ulcer, and 75 with gastric carcinoma). Although oipA status was closely linked to specific cag PAI, vacA, and babA2 genotypes, only oipA status remained in the final model to discriminate duodenal ulcer from gastritis (adjusted odds ratio [OR] = 5 and 95% confidence interval [CI] = 2.1-11.9). Among the factors, only a functional oipA was significantly associated with high H. pylori density, severe neutrophil infiltration, and high mucosal IL-8 levels (P < 0.001). oipA status had no relationship to gastric atrophic changes. CONCLUSIONS: oipA functional status was related to clinical presentation, H. pylori density, and gastric inflammation. cag PAI, babA2, or vacA status appear important only as surrogate markers for a functional oipA gene.

Amino Acid Sequence↗
PubMed2002

Effect of interleukin 1 polymorphisms on gastric mucosal interleukin 1beta production in Helicobacter pylori infection.

BACKGROUND & AIMS: Although epidemiological studies suggest that interleukin (IL)-1 genetic polymorphisms are involved in Helicobacter pylori-related gastric carcinogenesis, the data are conflicting regarding the effects of these polymorphisms on IL-1beta production. METHODS: IL-1B-511 polymorphism was genotyped by polymerase chain reaction (PCR)-restriction fragment length polymorphism, and IL-1RN variable number of tandem repeats was determined by PCR. Mucosal IL-1beta levels were measured by enzyme-linked immunosorbent assay. To determine which factors influence mucosal IL-1beta levels, gastric inflammation, and atrophy, multiple regression analyses were performed. RESULTS: We studied 117 H. pylori-infected Japanese patients. Carriers of the IL-1B-511T/T genotype or IL-1RN*2 allele had higher mucosal IL-1beta levels than noncarriers (partial regression coefficient [PRC] +/- SE), TT versus CC: 37.6 +/- 6 [antrum] and 32.1 +/- 6 [corpus] pg/mg protein (P < 0.001 for each), *1/*2 versus *1/*1: 24 +/- 8 [antrum] (P <0.01) and 36.5 +/- 7 [corpus] (P <0.001). Simultaneous carriers of IL-1B-511T/T genotype and IL-1RN*2 allele had the highest IL-1beta levels (82.9 +/- 12 [antrum] and 87.2 +/- 11 [corpus]) and showed a synergistic effect between 2 loci. The *1/*2 carriers were closely related to atrophy (PRC +/- SE; 0.87 +/- 0.4 [antrum] and 0.93 +/- 0.4 [corpus], P < 0.05), whereas being a carrier of the -511T/T genotype was related to severe gastric inflammation. CONCLUSIONS: IL-1 genetic polymorphisms influenced H. pylori-related gastric mucosal IL-1beta levels and were related to gastric inflammation and atrophy, factors thought to be important in gastric carcinogenesis.

Adult↗
PubMed2002

Helicobacter pylori infection in mice: Role of outer membrane proteins in colonization and inflammation.

BACKGROUND & AIMS: Mouse models of Helicobacter pylori infection have yielded variable results with respect to colonization and inflammation. We examined whether outer membrane proteins (OMPs) or the cag pathogenicity island (PAI) was responsible for some of this variability. METHODS: C57BL/6 mice received clinical H. pylori isolates with different genotypes for the cag PAI and OMP gene switch status, as well as isogenic gene knockout mutants for cagE, oipA, babA2, hopZ, cagE/oipA, or oipA/hopZ. Bacterial density, histology, and mucosal cytokine/chemokine levels were measured after 4 and 12 weeks. RESULTS: oipA, hopZ, hopO, and hopP switch status influenced both H. pylori density and colonization ability in mice. When 2 or more of the genes were "off," colonization rates were markedly reduced compared with those for strains with all genes "on" (from 58% to 0% after 12 weeks). oipA knockout mutants caused reduced inflammation and decreased mucosal interleukin 6 messenger RNA and KC messenger RNA and protein levels. H. pylori density and colonization ability were reduced if hopO or hopP switch status was changed from "on" to "off." There was a close relationship (r > 0.7) between the H. pylori density of the gastric mucosa of humans and mice when using the same H. pylori strains. CONCLUSIONS: Many of the differences reported with mouse models may reflect subtle unrecognized differences (e.g., switch status of an OMP gene), emphasizing the necessity of characterizing isolates before and after experiments. The mouse model may be suitable for investigating factors related to colonization ability, H. pylori density, and gastric mucosal inflammation.

Animals↗
PubMed2002

Helicobacter pylori infection in asymptomatic children: impact of epidemiologic factors on accuracy of diagnostic tests.

BACKGROUND: Childhood is a time of high risk for acquiring H. pylori infection. Accurate information on the epidemiology of the infection requires accurate diagnostic tests. OBJECTIVE: To study the epidemiologic factors that influence the accuracy of diagnostic tests among asymptomatic children. METHODS: Two rapid, noninvasive assays (FlexSure whole-blood test and OraSure saliva test) were evaluated using the 13C-urea breath test ((13)C-UBT) as the gold standard. The three diagnostic tests were conducted in children from 10 licensed day care centers from various locations in Houston, Texas. Demographic information and socioeconomic factors evaluated included age, gender, ethnicity, and crowded living conditions in each center. The three tests were conducted on each child on the same day. We examined the effect of epidemiologic factors on the sensitivity, the specificity, and the positive and negative predictive values of both tests. RESULTS: Thirty-two percent of the 243 asymptomatic children who participated in the study tested positive for H. pylori using 13C-UBT. Among all the children, the sensitivities of FlexSure and OraSure were 47% (95% confidence interval, 35-57%) and 65% (95% confidence interval, 54-73%), respectively. Both tests had greater than 95% specificity. Positive and negative predictive values for FlexSure were 86% and 80%, respectively, and 98% and 86% for OraSure. Among children attending the more crowded day care centers, the sensitivities of FlexSure and OraSure were 40% and 63%, respectively, compared with 100% sensitivity for FlexSure and 80% sensitivity for OraSure among children attending the less-crowded centers. FlexSure and OraSure tests had the highest sensitivities among the 6-to 10-year-olds. Ethnicity had no effect on the sensitivity or the specificity of either test. CONCLUSION: Epidemiologic factors influenced the accuracy of serologic tests for diagnosing H. pylori infection in children. The lowest sensitivities of both tests were among children who attended the more crowded centers and among the youngest and oldest age groups, reflecting an increased proportion of recent infections. The strategy for choosing a diagnostic test for H. pylori infection in children varies based on the epidemiologic characteristics of the studied population.

Adolescent↗
PubMed2002

Histological patterns of gastritis in H. pylori-infected individuals with a family history of gastric cancer.

OBJECTIVE: Different types of chronic gastritis, including antral predominant, corpus predominant, and multifocal pangastritis, are associated with Helicobacter pylori infection. Specific patterns of H. pylori gastritis that might characterize individuals with family histories of noncardia gastric cancer (GC) were investigated. METHODS: Histopathological changes associated with H. pylori gastritis were assessed in 111 individuals with family histories of GC and in 77 without from a region with high prevalence of H. pylori infection and GC. Gastric biopsies were taken from 12 sites (antrum, five; corpus, six; and cardia, one). RESULTS: Individuals (age < 36 yr) with family histories of GC developed pangastritis and had higher H. pylori bacterial scores (p < 0.05) in the gastric corpus, whereas those without family histories of GC typically had antral predominant gastritis. The correlation between density of polymorphonuclear leukocytes and density of H. pylori at each biopsy site was statistically significant (p < 0.01). Pangastritis was associated with a higher density of lymphoid aggregates and follicles (p < 0.05) in the corpus of younger individuals (age < 36) and in the antrum of older individuals (age > or = 48) with positive family histories of GC. CONCLUSIONS: Pangastritis and high lymphoid follicle density associated with H. pylori infection were found in patients with family histories of GC. Because a family history of gastric carcinoma is associated with increased risk of gastric cancer development, characterization of histological patterns of gastritis may be applicable to gastric cancer screening and surveillance, especially in relatively young at-risk populations.

Adult↗
PubMed2002

Clinical presentation in relation to diversity within the Helicobacter pylori cag pathogenicity island.

OBJECTIVE: This study investigated the genetic diversity of the cag pathogenicity island (PAI) in Helicobacter pylori (H. pylori) in relation to clinical outcome and interleukin (IL)-8 production. METHODS: Seven genes in the cag PAI (cagA, cagE, cagG, cagM, cagT, open reading frame 13 and 10) were examined by polymerase chain reaction and Southern blot hybridization using H. pylori from 120 patients with different presentations (duodenal ulcer, gastric cancer, gastritis alone). IL-8 production from AGS cells (gastric cancer cell line) cocultured with H. pylori was measured by ELISA. RESULTS: An intact cag PAI was present in 104 (87%) isolates, and five (4%) had deletions within the cag PAI; 11 (9%) lacked the entire cag PAI. Clinical isolates containing the complete cag PAI induced a greater secretion of IL-8 as compared with those without the cag PAI (3048 +/- 263 vs 480 +/- 28 pg/ml, p < 0.001). Deletion of only cagG reduced IL-8 secretion by two thirds. Deletions of more than one locus reduced IL-8 secretion to background. A similar proportion of H. pylori from patients with gastritis, duodenal ulcer, or gastric cancer had intact cag PAI (88%, 88%, and 85%, respectively). Although the presence of cagG was a better predictor of the presence of an intact cag PAI than cagA or cagE, the presence or absence of any of these genes had no association with clinical presentation. CONCLUSION: Although the cag PAI plays an important role in IL-8 production, clinical presentation cannot be predicted by the presence of an intact cag PAI or any of these seven cag PAI genes.

Adult↗
PubMed2002

New serological assay for detection of putative Helicobacter pylori virulence factors.

We evaluated a new immunoblot assay (Helicoblot 2.1) for Helicobacter pylori infection and CagA and VacA status by using serum samples from 222 patients. The test accurately detected H. pylori infection and VacA status, but improvements in the interpretation criteria are required before it can be recommended for determination of CagA status.

Antibodies, Bacterial↗
PubMed2002

Discrimination between cases of duodenal ulcer and gastritis on the basis of putative virulence factors of Helicobacter pylori.

The BabA, cagA, and vacA statuses of 827 Helicobacter pylori isolates were used in logistic regression models to discriminate duodenal ulcer from gastritis. Only BabA was a candidate for a universal virulence factor, but the low c statistic value (0.581) indicates that none of these factors were helpful in predicting the clinical presentation.

Adhesins, Bacterial↗
PubMed2002

Helicobacter pylori infection in Kazakhstan: effect of water source and household hygiene.

The epidemiology of Helicobacter pylori infection and risk factors associated with its transmission are not well understood. Kazakhstan is country with two ethnic groups, Asian (Kazakhs) and Western (Russians), living under similar socioeconomic conditions. The aim of this study was to examine the seroepidemiologic pattern of H. pylori and hepatitis A among the same individuals from both ethnic groups, with emphasis on water source and household sanitation practices. This was a cross-sectional seroepidemiologic study conducted among unrelated healthy individuals in Kazakhstan. From May through August 1999, individuals between the ages of 10 and 60 years from Almaty, Kazakhstan, were invited to participate. Demographic information, socioeconomic factors, living conditions, and various aspects of the local household environment including access to water were collected. A clean water index (CWI) was created based on combined factors, consistency of boiling water before drinking, frequency of storing and reusing water, and frequency of bathing and showering. H. pylori and hepatitis A antibodies were assessed by enzyme-linked immunosorbent assay. Two hundred eighty-eight individuals between the ages of 10 and 60 years participated. The prevalence of H. pylori infection was almost identical among the two ethnic groups (Russians 79% and Kazakhs 80%). H. pylori infection was inversely correlated with the CWI (i.e., 56%, 79%, and 95% for high, middle, and low, respectively (P < .05). Drinking river water had highest risk of H. pylori infection (OR = 13.6, 95% CI = 1.8-102.4; P < .01, compared with tap water). Crowding showed no significant effect on H. pylori prevalence. Anti-HAV antibodies were found in 86% of the population, 90% among the Russians versus 82% among the Kazakhs (OR = 1.8, 95% CI = 1.1-3.8, P = .05). Although the two infections were highly correlated (P < .001), antibody to both infections were present simultaneously in only 74%. The prevalence of H. pylori infection in Kazakhstan is very high. The data suggest that transmission of H. pylori can be water borne, related to poor sanitary practices, or both. The high prevalence of antibodies to H. pylori and HAV among this population is a marker for poor sanitation and hygienic practices. Reducing the rate of H. pylori transmission will require improvements in overall sanitation including clean water, waste disposal, as well as in household hygienic practices.

Adolescent↗
PubMed2002

Urea breath testing and analysis in the primary care office.

The 13C-urea breath test provides accurate, noninvasive diagnosis of active Helicobacter pylori infection and can document posttherapy cure. This study evaluated point-of-care testing with onsite sample analysis with the use of a desktop infrared spectrophotometer. Ambulatory patients (N=320) underwent 13C-urea breath testing, and breath samples were analyzed immediately by clinic staff with no prior breath testing experience. Duplicate samples were sent to a reference laboratory, and the results of both methods were compared. Point-of-care testing was simple, with an overall agreement of 99.1%. Accurate near-patient 13C-urea breath testing is now practical in the primary care setting even when done by inexperienced personnel.

Adolescent↗