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It has been found that a ;gastric' type of epithelium tends to develop in the first part of the duodenum in patients with duodenal ulceration and is found in the second part of the duodenum in a patient with the Zollinger-Ellison syndrome. It is likely that ;gastric' epithelium appears when the duodenal acidity is high and it is resistant to ulceration.
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A. H. James (1964) studied this question.
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