Porcine reproductive and respiratory syndrome viruses (PRRSV) are divided into North American and European types, which show about 40% difference in their amino acid sequences. The divergence time of these two types has been estimated to be about 1980 from epidemiological data. This suggested that PRRSV have evolved at a higher evolutionary rate (order of 10(-2)/site/year) compared with other RNA viruses of 10(-3) to 10(-5)/site/year. Here, to test the evolutionary history of PRRSV speculated by the epidemiological background, we estimated the divergence time and evolutionary rate of PRRSV with molecular evolutionary analysis. Estimated divergence time (1972-1988) corresponded well to that estimated by the epidemiological data, and the evolutionary rate (4.71-9.8) x 10(-2) of PRRSV was indeed the highest among RNA viruses so far reported. Furthermore, we inferred important sites for the adaptation in order to examine how PRRSV have adapted to swine since they emerged. The adaptive sites were located not only in the epitopes related to immunity but also in the transmembrane regions including a signal peptide. In particular, the adaptive sites in the transmembrane regions were considered to affect compatibility to the host cell membrane. We conclude that PRRSV were transmitted from another host species to swine in about 1980 and have adapted to swine by altering the transmembrane regions.

Four Gram-positive, non-motile, non-spore-forming bacterial strains, LC4 T , LC6 T , LC10 T and LC13 T , were isolated from a filtration substrate made from trass, a volcanic rock, and their taxonomic positions were investigated by a polyphasic taxonomic approach. The novel strains grew over a temperature range of 5-40 6C, at pH values of 6-11 and in the presence of 3-7 % (w/v) NaCl. A phylogenetic tree based on 16S rRNA gene sequences showed the novel strains formed a distinct evolutionary lineage within the genus Arthrobacter. Chemotaxonomic analyses demonstrated that the major menaquinone was MK-9(H 2 ), a menaquinone typical of the Arthrobacter globiformis group. The major fatty acid was anteiso-C 15 : 0 and the major amino acid present in the cell-wall peptidoglycan was L-lysine. These observations supported the affiliation of the novel strains to the genus Arthrobacter. On the basis of their morphological, physiological and genotypic characteristics, the new isolates are considered to represent four novel species of the genus Arthrobacter, for which the names Arthrobacter niigatensis sp. nov.

Amycolatopsis echigonensis sp. nov. and Amycolatopsis niigatensis sp. nov., novel actinomycetes isolated from a filtration substrate

[Purpose] To clarify factors associated with falls in the elderly who are regarded as individuals with a lower risk of falls (low-risk elderly) based on their TUG test results, and consider effective fall prevention approaches.[Subjects and Methods] Twenty-nine elderly females with a TUG time of 13.5 seconds or shorter were divided into fall and non-fall groups based on the history of falls to compare the following items between them: the numbers of steps needed to walk normally during walk and sit-to-walk tasks; velocity of a forward shift in the center of gravity when standing during the sit-to-walk task; motor functions; and the level of fear of falling.[Results] Compared with the non-fall group (19), the fall group (10) needed 1 more step to walk normally during the sit-to-walk task, and their velocity of a forward shift in the center of gravity was significantly lower. Their markedly higher level of fear of falling was also noted. [Conclusion] A higher level of fear of falling was the most important factor associated with falls in the low-risk elderly with a history of falls, suggesting the necessity of improving their movement patterns as a fall prevention approach. Key words: the elderly with a lower risk of falls, factors associated with falls, fall prevention