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41.
Stearoyl CoA desaturase activity in liver microsomes, and insulin, thyroxine, and triiodothyronine levels in serum were measured after administration of streptozocin (STZ) and its antagonists to rats. The effect of STZ, which caused hyperglycemia and inhibited the desaturase activity, was antagonized by 2-desoxyglucose and 3-O-methyl-glucose; 1-O-methyl-3-desoxyglucose and 1-O-methyl-3-O-methylglucose were without any effect. The enzyme activity plotted against insulin levels showed a broad sigmoidal curve, whereas the activities versus thyroid hormone levels showed steeper sigmoidal curves. 相似文献
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The present study discusses the relationships between two independently developed models of games with incomplete information,hypergames(Bennett,1977) and Bayesian games(Harsanyi, 1967).The authors first show that any hypergame can naturally be reformulated in terms of Bayesian games in an unified way.The transformation procedure is called Bayesian representation of hypergame. The authors then prove that some equilibrium concepts defined for hypergames are in a sense equivalent to those for Bayesian games.Furthermore,the authors discuss carefully based on the proposed analysis how each model should be used according to the analyzer’s purpose. 相似文献
44.
Electrical signals control wound healing through phosphatidylinositol-3-OH kinase-gamma and PTEN 总被引:2,自引:0,他引:2
Zhao M Song B Pu J Wada T Reid B Tai G Wang F Guo A Walczysko P Gu Y Sasaki T Suzuki A Forrester JV Bourne HR Devreotes PN McCaig CD Penninger JM 《Nature》2006,442(7101):457-460
Wound healing is essential for maintaining the integrity of multicellular organisms. In every species studied, disruption of an epithelial layer instantaneously generates endogenous electric fields, which have been proposed to be important in wound healing. The identity of signalling pathways that guide both cell migration to electric cues and electric-field-induced wound healing have not been elucidated at a genetic level. Here we show that electric fields, of a strength equal to those detected endogenously, direct cell migration during wound healing as a prime directional cue. Manipulation of endogenous wound electric fields affects wound healing in vivo. Electric stimulation triggers activation of Src and inositol-phospholipid signalling, which polarizes in the direction of cell migration. Notably, genetic disruption of phosphatidylinositol-3-OH kinase-gamma (PI(3)Kgamma) decreases electric-field-induced signalling and abolishes directed movements of healing epithelium in response to electric signals. Deletion of the tumour suppressor phosphatase and tensin homolog (PTEN) enhances signalling and electrotactic responses. These data identify genes essential for electrical-signal-induced wound healing and show that PI(3)Kgamma and PTEN control electrotaxis. 相似文献
45.
Green revolution: a mutant gibberellin-synthesis gene in rice 总被引:36,自引:0,他引:36
Sasaki A Ashikari M Ueguchi-Tanaka M Itoh H Nishimura A Swapan D Ishiyama K Saito T Kobayashi M Khush GS Kitano H Matsuoka M 《Nature》2002,416(6882):701-702
The chronic food shortage that was feared after the rapid expansion of the world population in the 1960s was averted largely by the development of a high-yielding semi-dwarf variety of rice known as IR8, the so-called rice 'green revolution'. The short stature of IR8 is due to a mutation in the plant's sd1 gene, and here we identify this gene as encoding an oxidase enzyme involved in the biosynthesis of gibberellin, a plant growth hormone. Gibberellin is also implicated in green-revolution varieties of wheat, but the reduced height of those crops is conferred by defects in the hormone's signalling pathway. 相似文献
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The origin of multiple superconducting gaps in MgB2 总被引:3,自引:0,他引:3
Souma S Machida Y Sato T Takahashi T Matsui H Wang SC Ding H Kaminski A Campuzano JC Sasaki S Kadowaki K 《Nature》2003,423(6935):65-67
Magnesium diboride, MgB2, has the highest transition temperature (T(c) = 39 K) of the known metallic superconductors. Whether the anomalously high T(c) can be described within the conventional BCS (Bardeen-Cooper-Schrieffer) framework has been debated. The key to understanding superconductivity lies with the 'superconducting energy gap' associated with the formation of the superconducting pairs. Recently, the existence of two kinds of superconducting gaps in MgB2 has been suggested by several experiments; this is in contrast to both conventional and high-T(c) superconductors. A clear demonstration of two gaps has not yet been made because the previous experiments lacked the ability to resolve the momentum of the superconducting electrons. Here we report direct experimental evidence for the two-band superconductivity in MgB2, by separately observing the superconducting gaps of the sigma and pi bands (as well as a surface band). The gaps have distinctly different sizes, which unambiguously establishes MgB2 as a two-gap superconductor. 相似文献
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Valla T Johnson PD Yusof Z Wells B Li Q Loureiro SM Cava RJ Mikami M Mori Y Yoshimura M Sasaki T 《Nature》2002,417(6889):627-630
The properties of an interacting electron system depend on the electron correlations and the effective dimensionality. For example, Coulomb repulsion between electrons may inhibit, or completely block, conduction by intersite electron hopping, thereby determining whether a material is a metal or an insulator. Furthermore, correlation effects increase as the number of effective dimensions decreases; in three-dimensional systems, the low-energy electronic states behave as quasiparticles, whereas in one-dimensional systems, even weak interactions break the quasiparticles into collective excitations. Dimensionality is particularly important for exotic low-dimensional materials where one- or two-dimensional building blocks are loosely connected into a three-dimensional whole. Here we examine two such layered metallic systems with angle-resolved photoemission spectroscopy and electronic transport measurements, and we find a crossover in the number of effective dimensions from two to three with decreasing temperature. This is apparent from the observation that, in the direction perpendicular to the layers, the materials have an insulating character at high temperatures but become metal-like at low temperatures, whereas transport within the layers remains metallic over the whole temperature range. We propose that this change in effective dimensionality correlates with the presence of coherent quasiparticles within the layers. 相似文献