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排序方式: 共有80条查询结果,搜索用时 15 毫秒
31.
Hirotaka Imai Kyoko Shinya Ryo Takano Maki Kiso Yukiko Muramoto Saori Sakabe Shin Murakami Mutsumi Ito Shinya Yamada Mai thi Quynh Le Chairul A. Nidom Yuko Sakai-Tagawa Kei Takahashi Yasuyuki Omori Takeshi Noda Masayuki Shimojima Satoshi Kakugawa Hideo Goto Kiyoko Iwatsuki-Horimoto Taisuke Horimoto Yoshihiro Kawaoka 《PLoS pathogens》2010,6(9)
Highly pathogenic H5N1 influenza A viruses have spread across Asia, Europe, and Africa. More than 500 cases of H5N1 virus infection in humans, with a high lethality rate, have been reported. To understand the molecular basis for the high virulence of H5N1 viruses in mammals, we tested the virulence in ferrets of several H5N1 viruses isolated from humans and found A/Vietnam/UT3062/04 (UT3062) to be the most virulent and A/Vietnam/UT3028/03 (UT3028) to be avirulent in this animal model. We then generated a series of reassortant viruses between the two viruses and assessed their virulence in ferrets. All of the viruses that possessed both the UT3062 hemagglutinin (HA) and nonstructural protein (NS) genes were highly virulent. By contrast, all those possessing the UT3028 HA or NS genes were attenuated in ferrets. These results demonstrate that the HA and NS genes are responsible for the difference in virulence in ferrets between the two viruses. Amino acid differences were identified at position 134 of HA, at positions 200 and 205 of NS1, and at positions 47 and 51 of NS2. We found that the residue at position 134 of HA alters the receptor-binding property of the virus, as measured by viral elution from erythrocytes. Further, both of the residues at positions 200 and 205 of NS1 contributed to enhanced type I interferon (IFN) antagonistic activity. These findings further our understanding of the determinants of pathogenicity of H5N1 viruses in mammals. 相似文献
32.
N Watanabe K Sakabe N Sakabe T Higashi K Sasaki S Aibara Y Morita K Yonaha S Toyama H Fukutani 《Journal of biochemistry》1989,105(1):1-3
The three-dimensional structure of omega-amino acid:pyruvate aminotransferase from Pseudomonas sp. F-126, an isologous alpha 4 tetramer containing pyridoxal 5'-phosphate (PLP) as a cofactor, has been determined at 2.0 A resolution. The diffraction data were collected with a newly developed Weissenberg camera with a Fuji Imaging Plate, using synchrotron radiation. The mean figure-of-merit was 0.57. The subunit is rich in secondary structure and comprises two domains. PLP is located in the large domain. The high homology in the secondary structure between this enzyme and aspartate aminotransferase strongly indicates that these two types of enzymes have evolved from a common ancestor. 相似文献
33.
The Influence of Hypoxia on the Concentrations of Cyclic Nucleotides in the Rat Brain 总被引:1,自引:0,他引:1
Abstract: In order to study the influence of hypoxia on cyclic nucleotides in the brain, we reduced arterial Po, for 15–30 min in lightly anaesthetised and artificially ventilated rats to obtain values ranging from about 45 to about 10 mm Hg. In an additional group (arterial Po2 18–22 mm Hg), the tissue hypoxia was aggravated by moderate arterial hypotension (mean arterial blood pressure about 80 mm Hg). In all animals, electrocortical activity was recorded. Cyclic GMP concentrations in cerebral cortex were unchanged in all groups but one. In that group, in which tissue hypoxia was severe enough to induce a suppression-burst EEG pattern and a measurable reduction in the adenylate energy charge, cyclic GMP concentrations were slightly increased ( p < 0.05). Cyclic AMP concentrations remained unaltered at all degrees of hypoxia studied. It is concluded that changes in cyclic nucleotides in brain tissue occur first at such severe degrees of hypoxia of the duration studied that function and metabolism are profoundly altered. 相似文献
34.
H Matsushita O Endo S Goto H Shimizu H Matsumoto K Tamakawa T Endo Y Sakabe H Tokiwa M Ando 《Mutation research》1992,271(1):1-12
A collaborative study has been performed over a period of 3 years to develop a suitable method for monitoring the mutagenicity of airborne particulate matter. The study was organized with 8 laboratories and performed in the following steps: (1) selection of a suitable technique for each process involved in the mutagenicity monitoring, (2) developing a tentative protocol by combining systematically the selected techniques, (3) evaluation of the protocol by intra- and inter-laboratory studies, (4) modification of the protocol according to the evaluation, and (5) evaluation of the modified protocol by conducting an interlaboratory study. We found a suitable method for mutagenicity monitoring of particles in the atmosphere. Airborne particles were sampled with a high-volume sampler, the samples were stored at -80 degrees C, extracted by sonication using dichloromethane, solvent-exchanged, and assayed by the preincubation method using Salmonella typhimurium TA98 and TA100. The observed mutagenic activity was normalized with that of an internal standard. Round robin tests revealed that the method resulted in excellent reproducibility. The coefficient of variation for mutagenic activities of airborne particulate samples collected in various districts of Japan were in the range of 14.7 +/- 6.6% to 19.6 +/- 4.0% for strains TA98 and TA100 with and without metabolic activation. We also found that the plate incorporation method was equivalent to the preincubation method for airborne particulate extracts. 相似文献
35.
Self-excitation in a porous membrane doped with sorbitan monooleate (Span-80) induced by an Na+/K+ concentration gradient 总被引:1,自引:0,他引:1
The electrical potential across a fine-pore membrane doped with sorbitan monooleate (Span-80) imposed between aqueous solutions of NaCl and KCl was studied. It was found that this system showed rhythmic and sustained oscillations of electrical potential between the two aqueous solutions. These oscillations were attributed to the change of permeability of Na+ and K+ across the membrane, which originated from the phase transition of Span-80 molecules within the fine pores. Impedance measurement across the membrane also suggested a change in permeability. It was found that this membrane exhibited the property of differential negative resistance. In relation to this, it was shown that Na+ and K+ have different effects on the aggregation of Span-80 molecules. The mechanism of oscillation is discussed in relation to the ability of Span-80 molecules to behave as a dynamic channel through the membrane. This oscillatory phenomenon is interesting because in biological nervous membranes a difference between the concentrations of Na+ and K+ across the membranes is essential for excitability. 相似文献
36.
Hattori T Sakabe Y Ogata M Michishita K Dohra H Kawagishi H Totani K Nikaido M Nakamura T Koshino H Usui T 《Carbohydrate research》2012,347(1):16-22
The enzymatic synthesis of an α-chitin-like substance via a non-biosynthetic pathway has been achieved by transglycosylation in an aqueous system of the corresponding substrate, tri-N-acetylchitotriose [(GlcNAc)(3)] for lysozyme. A significant amount of water-insoluble product precipitated out from the reaction system. MALDI-TOFMS analysis showed that the resulting precipitate had a degree of polymerization (DP) of up to 15 from (GlcNAc)(3). Solid-state (13)C NMR analysis revealed that the resulting water-insoluble product is a chitin-like substance consisting of N-acetylglucosamine (GlcNAc) residues joined exclusively in a β-(1→4)-linked chain with stringent regio-/stereoselection. X-ray diffraction (XRD) measurement as well as (13)C NMR analysis showed that the crystal structure of synthetic product corresponds to α-chitin with a high degree of crystallinity. We propose that the multiple oligomers form an α-chitin-like substance as a result of self-assembly via oligomer-oligomer interaction when they precipitate. 相似文献
37.
Yanagawa N Sakabe M Sakata H Yamagishi T Nakajima Y 《Development, growth & differentiation》2011,53(3):366-377
During axis formation in amniotes, posterior and lateral epiblast cells in the area pellucida undergo a counter-rotating movement along the midline to form primitive streak (Polonaise movements). Using chick blastoderms, we investigated the signaling involved in this cellular movement in epithelial-epiblast. In cultured posterior blastoderm explants from stage X to XI embryos, either Lefty1 or Cerberus-S inhibited initial migration of the explants on chamber slides. In vivo analysis showed that inhibition of Nodal signaling by Lefty1 affected the movement of DiI-marked epiblast cells prior to the formation of primitive streak. In Lefty1-treated embryos without a primitive streak, Brachyury expression showed a patchy distribution. However, SU5402 did not affect the movement of DiI-marked epiblast cells. Multi-cellular rosette, which is thought to be involved in epithelial morphogenesis, was found predominantly in the posterior half of the epiblast, and Lefty1 inhibited the formation of rosettes. Three-dimensional reconstruction showed two types of rosette, one with a protruding cell, the other with a ventral hollow. Our results suggest that Nodal signaling may have a pivotal role in the morphogenetic movements of epithelial epiblast including Polonaise movements and formation of multi-cellular rosette. 相似文献
38.
39.
Kaori Suyama Masahiko Watanabe Kou Sakabe Asako Otomo Yoshinori Okada Hayato Terayama Takeshi Imai Joji Mochida 《PloS one》2014,9(1)
Oxidative stress, caused by the over production of reactive oxygen species (ROS), has been shown to contribute to cell damage associated with neurotrauma and neurodegenerative diseases. ROS mediates cell damage either through direct oxidation of lipids, proteins and DNA or by acting as signaling molecules to trigger cellular apoptotic pathways. The 78 kDa glucose-regulated protein (GRP78) is an ER chaperone that has been suggested to protect cells against ROS-induced damage. However, the protective mechanism of GRP78 remains unclear. In this study, we used C6 glioma cells transiently overexpressing GRP78 to investigate the protective effect of GRP78 against oxidative stress (hydrogen peroxide)-induced injury. Our results showed that the overexpression of GRP78 significantly protected cells from ROS-induced cell damage when compared to non-GRP78 overexpressing cells, which was most likely due to GRP78-overexpressing cells having higher levels of glutathione (GSH) and NAD(P)H:quinone oxidoreductase 1 (NQO1), two antioxidants that protect cells against oxidative stress. Although hydrogen peroxide treatment increased lipid peroxidation in non-GRP78 overexpressing cells, this increase was significantly reduced in GRP78-overexpressing cells. Overall, these results indicate that GRP78 plays an important role in protecting glial cells against oxidative stress via regulating the expression of GSH and NQO1. 相似文献
40.