Helicobacter pylori and Epstein-Barr virus infection and the p53 tumour suppressor pathway in gastric stump cancer compared with carcinoma in the non-operated stomach

AIM: To evaluate similarities and differences between gastric stump cancer and conventional carcinoma in the non-operated stomach. METHODS: 26 stump carcinomas were compared with 24 conventional stomach cancers. Stage, histological type, and demographics were comparable in the two groups. Expression of p53 and p21-Waf1/Cip1 was evaluated by immunohistochemical staining. Helicobacter pylori infection was evaluated by examining haematoxylin-eosin stained slides and immunohistochemistry. Epstein-Barr virus infection was evaluated by RNA in situ hybridisation. RESULTS: Expression of p53 and p21-Waf1/Cip1 was similar in both groups and positive in more than half of the patients. H pylori infection was observed in six stump carcinomas and 17 conventional carcinomas in the intact stomach (p < 0.01). RNA in situ hybridisation (EBER1-ISH) for Epstein-Barr virus was positive in nine stump carcinomas and two carcinomas in the non-operated stomach (p < 0.05). CONCLUSIONS: There appear to be aetiological differences between stump carcinoma and cancer in the intact stomach. Further study of these differences may improve our understanding of gastric carcinogenesis in general.     

Reactions of ethylbenzene in the presence of toluene over external surface passivated MFI zeolite

The reactions of ethylbenzene in the presence of toluene were studied over external surface passivated MFI zeolite. With increase in extent of external surface passivation the para selectivity of both transalkylation and disproportionation reactions enhanced. The effects of mole ratio of ethylbenzene to toluene, reaction temperature and WHSV on the performance of the modified zeolite are discussed. It was observed that the high para selectivity feature of the modified zeolite is not influenced by changes in reaction conditions.     

Helicobacter pylori and the birth cohort effect: evidence of a continuous decrease of infection rates in childhood

OBJECTIVE: To investigate whether the decrease in rate of Helicobacter pylori infection in subsequent birth cohorts has continued during the last decades. METHODS: Determination by ELISA of IgG H. pylori antibodies in 314 serum samples from Dutch children (age 6-8 yr, n = 154) and young adolescents (age 12-15 yr, n = 160), collected in 1978 and 1993. RESULTS: The prevalence of H. pylori declined from 19% to 9% at age 6-8 yr and from 23% to 11% at age 12-15 yr. For the whole study population, a decline from 21% to 10% (p = 0.01) was observed between 1978 and 1993. On the basis of these data and an incidence of infection with H. pylori of 0.3% per year during the same period, a model for both past and future prevalence rates of H. pylori in the Dutch population was calculated. The outcome demonstrates a decrease from more than 50% around World War II to less than 20% for the whole population around year 2040. CONCLUSIONS: H. pylori infection rates in childhood have continued to decline until recent decades, demonstrating a persistent birth cohort effect. This decline will result in a very low prevalence of H. pylori infection in the Dutch population during the next decades, becoming even lower as the observed decline in children and young adolescents continues.     

The prevalence of antibiotic-resistant faecal Escherichia coli in healthy volunteers in Venezuela

Faecal samples were collected from healthy volunteers in two regions in Venezuela, the village of Grulla (n = 195) and the city of Mérida (n = 181), and analysed for the prevalence of antibiotic resistant faecal Escherichia coli as well as the antibiotic susceptibility of the strains isolated. The highest prevalences of resistance were observed for amoxicillin, oxytetracycline, sulfamethoxazole and trimethoprim. The percentages found for Grulla were 46, 38, 44 and 30%, respectively; for Mérida 39, 65, 56 and 36%, respectively. In Mérida, a significantly higher prevalence of resistance for oxytetracycline was found (P < 0.05). Significant differences in the distribution of the MIC values between Grulla and Mérida were observed for amoxicillin, chloramphenicol and oxytetracycline (P < 0.05). In Grulla, the most frequent pattern was resistance to amoxicillin only and in Mérida to oxytetracycline only. Amoxicillin resistance was due to production of TEM1 beta-lactamase.     

Oncological implications of RET gene mutations in Hirschsprung's disease

BACKGROUND: Germline mutations of the RET proto-oncogene identical to those found in the tumour predisposition syndrome multiple endocrine neoplasia type 2A (MEN2A), were detected in 2.5-5% of sporadic and familial cases of Hirschsprung's disease. Some patients with Hirschsprung's disease may therefore be exposed to a highly increased risk of tumours. AIMS: To define clinical use of RET gene testing in Hirschsprung's disease and related patient management from an oncological point of view. METHODS: Sixty patients with Hirschsprung's disease were screened for RET mutations. In three, MEN2A type RET mutations were detected. Case reports for these three patients are presented. RESULTS AND CONCLUSIONS: Only 22 families or sporadic patients with Hirschsprung's disease and MEN2A type RET mutations have been reported. Therefore, it is difficult to predict tumour risk for patients with familial or sporadic Hirschsprung's disease, and their relatives, who carry these mutations. For these mutation carriers, periodic screening for tumours as in MEN2A is advised, but prophylactic thyroidectomy is offered hesitantly. RET gene testing in familial or sporadic Hirschsprung's disease is not recommended at present outside a complete clinical research setting. In combined MEN2A/Hirschsprung's disease families RET gene testing, tumour screening, and prophylactic thyroidectomy are indicated as in MEN2A.     

Sequence specificity of illegitimate plasmid recombination in Bacillus subtilis: possible recognition sites for DNA topoisomerase I

Previous work in our group indicated that structural plasmid instability in Bacillus subtilis is often caused by illegitimate recombination between non-repeated sequences, characterized by a relatively high AT content. Recently we developed a positive selection vector for analysis of plasmid recombination events in B. subtilis which enables measurement of recombination frequencies without interference of selective growth differences of cells carrying wild-type or deleted plasmids. Here we have used this system to further analyse the sequence specificity of illegitimate plasmid recombination events and to assess the role of the host-encoded DNA topoisomerase I enzyme in this process. Several lines of evidence suggest that single-strand DNA nicks introduced by DNA topoisomerase I are a major source of plasmid deletions in pGP100. First, strains overproducing DNA topoisomerase I showed increased levels of plasmid deletion. Second, these deletions occurred predominantly (>90% of the recombinants) between non-repeated DNA sequences, the majority of which resemble potential DNA topoisomerase I target sites. Sequence alignment of 66 deletion end-points confirmed the previously reported high AT content and, most importantly, revealed a highly conserved C residue at position -4 relative to the site of cleavage at both deletion termini. Based on these genetic data we propose the following putative consensus cleavage site for DNA topoisomerase I of B.subtilis: 5'-A/TCATA/TTAA/TA/TA-3'.