Aldehyde dehydrogenase-2 (ALDH2) eliminates most of the acetaldehyde produced during alcohol metabolism. In some drinkers, a mutant ALDH2 allele contributes to diminished activity of the enzyme, dramatically increasing the risk for esophageal cancer. This study was designed to evaluate the ALDH2 gene polymorphism as a predictor of the development of cancers prevalent in Japanese alcoholics. We performed ALDH2 genotyping on lymphocyte DNA samples from Japanese alcoholic men (487 cancer-free; 237 with cancer, including 34 oropharyngolaryngeal, 87 esophageal, 58 stomach, 46 colon, 18 liver, 7 lung, 9 other sites, and 19 multiple primary cancers in two or three organs). The frequencies of the mutant ALDH2*2 allele were significantly higher in alcoholics with oropharyngolaryngeal (52.9%), esophageal (52.9%), stomach (22.4%), colon (21.7%) and esophageal cancer concomitant with oropharyngolaryngeal and/or stomach cancer (78.6%), than in cancer-free alcoholics (9.0%). After adjustment for age, daily alcohol consumption and amount of cigarette smoking, significantly increased risks (odds ratios) in the presence of the ALDH2 *2 allele were found for oropharyngolaryngeal (11.14), esophageal (12.50), stomach (3.49), colon (3.35), lung (8.20) and esophageal cancer concomitant with oropharyngolaryngeal and/or stomach cancer (54.20) but not for liver or other cancers. These results suggest a general role of acetaldehyde, a recognized animal carcinogen, in the development of human cancers.
Polycarbosilane as the precursor of continuous SiC fibre was synthesized by thermal decomposition of polydimethylsilane. The structure of the polycarbosilane is concluded to be similar to that of polysilapropylene by the measurements of i.r. spectra, NM R spectra and chemical analyses. Its formation mechanisms are initially the formation ofcarbosilane by thermal decomposition of polydimethylsilane and then the increase in molecular weight by dehydrogenation-condensation of the carbosilane. Molecular structure and molecular weight distribution of the polycarbosilane depend on the reaction temperature.
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