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  • 1
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background. Reinfection of Helicobacter pylori after eradication is rare in developed countries but most often occurs within 1 year. In the present study, we attempted to differentiate between reinfection and recrudescence of H. pylori strains between 6 months and 6 years after successful eradication in Japan, a country with a high prevalence of H. pylori infection.Materials and Methods. After successful eradication of H. pylori, 274 patients were followed up by endoscopy and urea breath test. In recurrent patients, H. pylori strains isolated initially and after recurrence were compared using PCR-based restriction fragment length polymorphism (RFLP) analysis.Results. Recurrence of H. pylori occurred in 15 of 274 patients (5.5%) at 6 months after eradication and the annual recurrence rate was 2.0% per patient year (between 1 and 6 years). PCR-based RFLP analysis of H. pylori strains isolated initially and after recurrence showed that 62.5% (at 6 months) and 100% (after 1 years) of bacteria were of different strains.Conclusion. Reinfection of H. pylori was not as rare at 6 months after eradication as reported previously, and up to 6 years after eradication, the annual reinfection rate is 2.0% per patient year in Japan.
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  • 2
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background. Helicobacter pylori is accepted as a definite human gastric carcinogen from an epidemiological point of view despite insufficient experimental data. Although we previously showed that the number of p53 immunopositive cells in the atrophic gastric mucosa of H. pylori-infected Japanese monkeys gradually increased over time, data on p53 gene mutations were not obtained in that study. To obtain direct evidence of carcinogenesis associated with H. pylori infection, we investigated whether p53 gene mutations are present in the gastric mucosa of a nonhuman primate model susceptible to H. pylori.Materials and Methods. Using the DNA from gastric tissues obtained from six H. pylori-uninfected monkeys of different ages, nucleotide sequence of the wild-type p53 gene was determined by amplification of exons (Ex) 5, 6, 7 and 8 and sequencing. Gastric specimens obtained from eight Japanese monkeys that had been infected with H. pylori for different lengths of time (1.5–7.5 years), were analyzed for mutations in exons 5–8 of p53.Results. In the six H. pylori-uninfected monkeys, nucleotide sequences of p53 Ex 5–8 were completely common and no mutations were noted. However, among the monkeys that were infected with H. pylori over various periods of time, there was an accumulation of p53 nucleotide (amino acid) substitutions as the gastric atrophy score increased.Conclusions. We conclude that the appearance of p53 gene mutation may be closely associated with the degree of gastric mucosal atrophy, which depends on the duration of H. pylori infection. Searching for p53 gene mutations may be useful for studying the progression of gastric carcinogenesis associated with H. pylori.
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  • 3
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background. Gastric carcinoids are strongly associated with chronic atrophic gastritis A, and it is suggested that hypergastrinemia plays a critical role in development of gastric carcinoids. Since Helicobacter pylori infection causes hypergastrinemia, it is held that H. pylori infection produces gastric carcinoids. We followed the histological changes of H. pylori-infected stomachs of Mongolian gerbils for a long time.Materials and Methods. Five-week-old-male Mongolian gerbils were infected with H. pylori ATCC 43504 with cagA gene, expressing vacuolating cytotoxin. Determination of the serum gastrin and histopathological examination of the stomach at 6, 12, 18, and 24 months after H. pylori inoculation was studied and compared with uninfected animals.Results In infected animals, the gastric carcinomas appeared 18 and 24 months after infection. Endocrine cell dysplasias and carcinoids with marked atrophic gastritis of the oxyntic mucosa were observed in the infected animals 24 months after H. pylori inoculation. The serum gastrin level in the infected group increased from an average of 86.2 pg/ml at the beginning of the study to an average of 498 pg/ml and 989 pg/ml at 18 and 24 months after infection, respectively. These changes in the serum gastrin levels were significant compared with uninfected controls that showed no changes.Conclusions. H. pylori infection caused not only gastric carcinomas but also enterochromaffin-like cell tumors in Mongolian gerbils, due to hypergastrinemia. This model is thought to be useful to study the relationship between hypergastrinemia and gastric carcinoids.
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  • 4
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Recent evidence has implicated bacterial involvement in the production of paralytic shellfish poison toxins, which are normally associated with bloom-forming algal species, specifically toxic dinoflagellate algae. Preliminary reports of the identification of toxin-producing bacteria isolated from the toxic marine dinoflagellate Alexandrium tamarense suggested that they belonged to the gamma sub-division of the Proteobacteria, specifically related to the bacterium Moraxella. Digoxigenin-labelled alpha, beta and gamma ribosomal rRNA probes, hybridized to both toxigenic and non-toxigenic bacteria isolated from several strains of Alexandrium tamarense, indicated that the bacteria belonged to the alpha sub-division of the Proteobacteria. Phylogenetic analysis of small subunit ribosomal RNA coding regions confirmed this and provided strong evidence that these bacteria are likely to represent a new genus in that group.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 2 (1990), S. 351-356 
    ISSN: 1573-5176
    Keywords: Alexandrium cohorticula ; paralytic shellfish toxins ; gonyautoxins ; saxitoxin ; Sagami Bay ; Japan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two clones ofAlexandrium cohorticula were isolated at Aburatsubo, Sagami Bay, Japan. Cultured cells of both contained high amounts of paralytic shellfish toxins. The toxicity of these isolates was comparable with that of highly toxic Thai clones. No significant difference in toxin components or their proportions was observed between Japanese and Thai strains. The optimum growth temperature of both strains was around 25 °C. Japanese strains survived at 15 °C, whereas Thai strains did not; the latter grew faster than the former at 30 °C.
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