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Human colorectal carcinomas may be induced from adenomas or they may occur de novo. To examine which is the main pathway, we analyzed point mutations at codon 12 in the c‐K‐ras 2 gene in 73 colorectal carcinomas, 13 metastatic tumors, 72 adenomas and 30 normal tissues. The c‐K‐ras 2 codon 12 mutation frequency was 0/30 in normal tissues, 0/17 in adenomas with mild atypia, 3/37 (8.1%) in adenomas with moderate atypia, 15/18 (83.3%) in adenomas with severe atypia, 19/73 (26.0%) in primary carcinomas and 3/13 (23.1%) in metastatic tumors. The mutation frequency in adenomas with severe atypia was much higher than that in carcinomas. These results indicate that many colorectal carcinomas may not be induced through adenomas with severe atypia.

We developed a method for direct DNA isolation from phyllosphere microbial communities, designated Direct-DIP. This method comprises DNA extraction from non-shredded leaves with benzyl chloride, and DNA purification by gel filtration. Scanning electron microscopy showed that epiphytic microorganisms were completely removed from the leaf surface after benzyl chloride treatment, while microstructures of the leaf were not damaged. Clear DGGE profiles were obtained regardless of the plant species. Shannon diversity indices of DGGE profiles by Direct-DIP were higher than those by a conventional method. Our findings suggest that Direct-DIP is a rapid, simple, and cost-effective method of extracting DNA from phyllosphere microbial communities.

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