Intra and interspecific nucleotide sequence variation of rDNA first internal transcribed spacer (ITS1) was analysed using all eight species of the genus Thunnus plus two out-group species within the same family, skipjack tuna Katsuwonus pelamis and striped bonito Sarda orientalis. Intraspecific nucleotide sequence variation in ITS1, including intra-genomic variation, was low, ranging from 0Á003 to 0Á014 [Kimura's two parameter distance (K2P)], whereas variation between species within the genus Thunnus ranged from 0Á009 to 0Á05. The Atlantic and Pacific northern bluefin tunas Thunnus thynnus thynnus and Thunnus thynnus orientalis, recently proposed to be distinct species, were found to share nearly identical ITS1 sequences (mean K2P ¼ 0Á006) well within the range of intraspecific variation. The northern bluefin tuna appeared to be a sister group to albacore Thunnus alalunga, with all other Thunnus species in a distinct clade. The ITS1 phylogeny was consistent with mtDNA phylogeny in clustering the three tropical Thunnus species (T. albacares, T. atlanticus and T. tonggol). Southern bluefin Thunnus maccoyii and bigeye Thunnus obesus tunas showed a closer affinity to this tropical tuna group than to the northern bluefin tuna and albacore. The molecular data supported mitochondrial introgression between species and contradicted morphological subdivision of the genus into two subgenera Neothunnus and Thunnus.

No abstract

No abstract

An inhibitor of factor Xa (fXa), the m-substituted benzamidine AXC1578 (1a), was structurally modified with the aim of increasing its potency. In particular, pyruvic acid and propionic acid substituents were incorporated into the P1 benzamidine moiety to introduce a favorable interaction with the oxy-anion hole in the catalytic triad region of fXa. This strategy was based on computational docking studies using the extracted active site of fXa. The validity of the computational model was supported by the acquisition of X-ray crystal structures of the 1a-trypsin and 3b-trypsin complexes (the homology around the active sites of fXa and trypsin is high). The above modifications significantly increased the inhibitory activity toward fXa, whereas the high selectivity for fXa versus thrombin was maintained or enhanced. Compounds 3b, 3c, 3e, and 4b are considered to be potential lead compounds for the development of orally active anticoagulant drugs because they demonstrated potent activity when administered orally to cynomolgus monkeys.