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排序方式: 共有1335条查询结果,搜索用时 15 毫秒
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Elisa Villa Aleksander S. Alekseev James E. Barrick Darwin R. Boardman Alexandra V. Djenchuraeva Beate Fohrer Holger Forke Natalya V. Goreva Philip H. Heckel Tatiana N. Isakova Olga Kossovaya Lance L. Lambert María-Luisa Martínez-Chacn Carlos A. Mndez Tamara I. Nemyrovska Svetlana Remizova Elias Samankassou Luis C. Snchez de Posada Katsumi Ueno Greg Wahlman David M. Work 《Palaeoworld》2009,18(2-3):114-119
Studies carried out for more than 10 years by the Task Group to establish GSSPs at the base of the Moscovian–Kasimovian and Kasimovian–Gzhelian boundaries have resulted in the proposal that the level at which the conodont species Idiognathodus simulator (Ellison, 1941) first appears be selected to mark the base of the Gzhelian Stage. This expands this eastern European chronostratigraphic unit to a global scale.I. simulator (sensu Barrick et al., 2008) has been identified so far in Midcontinent and eastern North America, the Moscow and Donets basins and southern Urals of eastern Europe, and in south-central China. Correlation of this level based on this species and other conodont species can be reinforced in some areas by ammonoid and fusulinid data. 相似文献
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Mitsuaki Yamashita Masafumi Kaneko Harukuni Tokuda Katsumi Nishimura Yuko Kumeda Akira Iida 《Bioorganic & medicinal chemistry》2009,17(17):6286-6291
A series of naphthoquinones based on the naphtho[2,3-b]furan-4,9-dione skeleton such as (−)-5-hydroxy-2-(1′-hydoxyethyl)naphtho[2,3-b]furan-4,9-dione (1) and its positional isomer, (−)-8-hydroxy-2-(1′-hydoxyethyl)naphtho[2,3-b]furan-4,9-dione (2), which are secondary metabolites found in the inner bark of Tabebuia avellanedae, were stereoselectively synthesized and their biological activities were evaluated in conjunction with those of their corresponding enantiomers. Compound 1 exhibited potent antiproliferative effect against several human tumor cell lines, but its effect against some human normal cell lines was much lower than that of mitomycin. On the other hand, its enantiomer (R)-1 was less active toward the above tumor cell lines than 1. The antiproliferative effect of 2 against all tumor cell lines was significantly reduced. These results indicated the presence of the phenolic hydroxy group at C-5 is of great important for increasing antiproliferative effect. In addition, 1 also showed higher cancer chemopreventive activity than 2, while there were no significant differences between 1 and 2 in antimicrobial activity. Both compounds displayed modest antifungal and antibacterial activity (Gram-positive bacteria), whereas they were inactive against Gram-negative bacteria. 相似文献
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Katsumi Togashi 《Population Ecology》1991,33(2):245-256
To understand the mechanism of spread of pine wilt disease caused by the pinewood nematode, Bursaphelenchus xylophilus, which is vectored by a cerambycid, Monochamus alternatus, the spatial distribution of trees weakened by the nematode was examined within a Pinus thunbergii stand from June to October for 4 years. The weakened trees were distributed in a clumped pattern in 1980 and 1981, at an early stage of infestation. In many cases, they showed a double-clumped pattern. The degree of aggregation was higher in June or July than after August. They were uniformly distributed in June or July 1982 and in June 1983 whereas they showed a double-clumped pattern after August. The trees were frequently weakened in June or July when they were near the trees weakened during the previous year. At quadrat sizes of more than 25 m2, spatial overlapping was pronounced between trees weakened during June–July of the current year and those weakened in the previous year. The seasonal changes in spatial distribution of weakened trees were explained by the interaction among M. alternatus, B. xylophilus and Pinus trees. 相似文献
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Staphylococcal gamma-hemolysin and leukocidin are bi-component cytolysins, consisting of LukF (or Hlg1)/Hlg2 and LukF/LukS, respectively. Here, we purified serum inhibitors of gamma-hemolysin and leukocidin from human plasma. Protein sequencing showed that the purified inhibitors of 62, 57, 50 and 38 kDa were the vitronectin fragments with truncation(s) of the C-terminal or both N- and C-terminal regions. The purified vitronectin fragments specifically bound to the Hlg2 component of gamma-hemolysin and the LukS component of leukocidin to form high-molecular-weight complexes with them, leading to inhibition of the toxin-induced lysis of human erythrocytes and human polymorphonuclear leukocytes, respectively. Intact vitronectin also showed inhibitory activity to the toxins. The ability of gamma-hemolysin and leukocidin to bind vitronectin and its fragments is a novel function of the pore-forming cytolysins. 相似文献
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Yasuhiro Morisawa Yukichi Kishida Katsumi Tanabe 《Bioscience, biotechnology, and biochemistry》2013,77(11):788-800
3β-Acetoxy-B-nor-5β-cholestan-6-one (Ia) afforded only one isolatable oxime (IIa), while oximation of 3β, 17β-diacetoxy-B-nor-5β-androstan-6-one (Ib) yielded two isomeric oximes (IIb and IIIb). 7-Aza-5β-cholestan-3β-ol (VIa), 7-aza-5β-androstane-3β, 17β-diol (VIc), and 6-aza-5β-androstane-3β, 17β-diol (VIIc) were synthesized by Beckmann rearrangement of these oximes, followed by reduction with lithium aluminium hydride. The structure of the aza-steroids were established by conversion of the intermediate lactams (IVa, b) into the lactones (IXa, b), prepared from the 3β-acetoxy-B-nor-6-oxo-5β-steroids (Ia, b) by Baeyer Villiger reaction. 相似文献
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Katsumi Kakinuma Noboru Ōtake Hiroshi Yonehara 《Bioscience, biotechnology, and biochemistry》2013,77(12):2529-2538
The structure of detoxin D1, one of the main active principles of detoxio complex, has been established on the basis of the degradative studies and spectral evidences as depicted in formula (I).Detoxin D1 has been demonstrated to belong to a new class of the depsipeptide contained an amino acid designated detoxinine which was newly isolated as a natural product. 相似文献
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