Ptaquiloside (1) is a potent carcinogen isolated from bracken fern. Under weakly alkaline conditions, the carcinogen is converted into dienone 2 which is thought to be the ultimate agent responsible for bracken fern carcinogenicity.This study details the selective alkylation and strand scission of DNA with dienone 2. Dienone 2 forms covalent adducts through N-3 of adenine or N-7 of guanine with opening of the cyclopropyl ring. Under physiological conditions, spontaneous cleavage of the N-glycosidic linkage occurs primarily at the modified adenines to produce abasic sites. The abasic sites are so unstable that subsequent backbone breakage occurs via a (3-elimination reaction. Product analyses on sequencing gels and HPLC reveal evolution of the structures of the 5'and 3'-termini that result from the abasic sites. In addition, the sequence selectivity for the DNA cleavage is demonstrated. The cleavage rates at the target adenine residues are affected by both 5'and 3'-flanking nucleotides. The rank orders are 5'-AT > 5'-AG >
The lizard genus Gekko consists of over 30 species distributed in Asia and Oceania. From the insular region of East Asia including Japan and Taiwan, 9 species (G. hokouensis, G. japonicus, G. shibatai, G. tawaensis, G. vertebralis,G. yakuensis, and 3 undescribed species) are currently recognized. We made karyological analyses for all these species. Their karyotypes invariably consisted of 2N = 38 chromosomes, but exhibited considerable variation in fundamental number (ranging from 56–62). Substantial chromosomal variation was detected even among populations of a morphologically relatively uniform species, G. hokouensis. Populations of G. hokouensis from the central and northern Ryukyus exhibited prominent female heteromorphic (i.e., ZW type) sex chromosomes. Populations of the southern Ryukyus exclusive of Yonagunijima also had ZW sex chromosomes, whose heteromorphisms were, however, much less prominent. The other G. hokouensis populations including the topotypic continental representatives and the population from Yonagunijima of the southern Ryukyus exhibited no sex chromosome heteromorphism at all. These results strongly suggest that G. hokouensis in the current taxonomic definition actually includes more than 2 species. The process of chromosomal evolution in the East Asian Gekko is hypothesized.
Two human cases of gnathostomiasis from ingestion of raw native Japanese loaches, Misgurnus anguillicaudatus, are reported. Seven early third-stage larval Gnathostoma nipponicum were recovered from 3,098 loaches in the same district in which 2 human patients had obtained and eaten raw loaches. Encapsulated G. nipponicum larvae were also recovered from loaches infected under laboratory conditions. All 6 weasels captured in the same district in which the naturally infected loaches were found and where the humans had become infected were infected with adult worms of the same species. This is the first report of M. anguillicaudatus serving as a second intermediate host of G. nipponicum.
A nanometric lateral scale (design pitch: 25 nm) with Si/SiO 2 multilayer thin-film structures was developed. The pitch of the developed nanometric lateral scale was calibrated using an atomic force microscope with a differential laser interferometer, and the uncertainty in pitch measurement was evaluated. In the uncertainty evaluation, two evaluation methods were revised to avoid overestimation. The analysis of variance was applied to the evaluation of uncertainties caused by the nonuniformity of the scale and the repeatability of the measurements in the same location. The expanded uncertainties (k = 2) were 29-154 pm in this study and became smaller than 0.43 nm, which is the expanded uncertainty evaluated in our previous study.
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