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61.
S. P. Singh D. G. Patel A. K. Snyder G. L. Pullen 《Cellular and molecular life sciences : CMLS》1986,42(1):58-60
Summary This study was done to delineate the role of - and -adrenergic receptors and cyclic AMP in the mechanism of ethanol effects on insulin release from isolated islets. Rats were given an -adrenergic blocker, phentolamine, or a -adrenergic blocker, propranolol. In addition, ethanol 1 g/kg was given intragastrically 1 h prior to sacrifice. Glucose mediated insulin release from isolated islets was enhanced by phentolamine and decreased by propranolol. Ethanol treatment inhibited glucose-induced insulin release from isolated islets of control rats as well as those given phentolamine and/or propranolol. Insulin release from isolated islets in response to dibutyryl-cyclic AMP was attenuated by ethanol. Theophylline enhanced glucose mediated insulin release from control islets but ethanol treatment produced a significant inhibition of insulin response. The data suggest that the site of action of the deleterious effects of ethanol on insulin release from isolated islets in rat does not involve adrenergic system and cyclic AMP.Supported by the U.S. Veterans Administration 相似文献
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63.
低碳锰钢中周期性带状组织 总被引:6,自引:0,他引:6
用扫描电镜和电子探针研究了低碳锰钢中的周期性带状组织,结果表明,在全部研究用钢中,钢锭经热轧后均出现这种组织,其严重程度随钢的成分而异,并随坯带加工顺序而增加,带状组织与锰的显微偏析等因素有关,适当的调整碳锰以及形成模跨铁素体带的转变产物可降低带状组织的严重程度。 相似文献
64.
Zauderer BA Berger E Soderberg AM Loeb A Narayan R Frail DA Petitpas GR Brunthaler A Chornock R Carpenter JM Pooley GG Mooley K Kulkarni SR Margutti R Fox DB Nakar E Patel NA Volgenau NH Culverhouse TL Bietenholz MF Rupen MP Max-Moerbeck W Readhead AC Richards J Shepherd M Storm S Hull CL 《Nature》2011,476(7361):425-428
Active galactic nuclei, which are powered by long-term accretion onto central supermassive black holes, produce relativistic jets with lifetimes of at least one million years, and the observation of the birth of such a jet is therefore unlikely. Transient accretion onto a supermassive black hole, for example through the tidal disruption of a stray star, thus offers a rare opportunity to study the birth of a relativistic jet. On 25 March 2011, an unusual transient source (Swift J164449.3+573451) was found, potentially representing such an accretion event. Here we report observations spanning centimetre to millimetre wavelengths and covering the first month of evolution of a luminous radio transient associated with Swift J164449.3+573451. The radio transient coincides with the nucleus of an inactive galaxy. We conclude that we are seeing a newly formed relativistic outflow, launched by transient accretion onto a million-solar-mass black hole. A relativistic outflow is not predicted in this situation, but we show that the tidal disruption of a star naturally explains the observed high-energy properties and radio luminosity and the inferred rate of such events. The weaker beaming in the radio-frequency spectrum relative to γ-rays or X-rays suggests that radio searches may uncover similar events out to redshifts of z?≈?6. 相似文献
65.
Li W Bloom JS Podsiadlowski P Miller AA Cenko SB Jha SW Sullivan M Howell DA Nugent PE Butler NR Ofek EO Kasliwal MM Richards JW Stockton A Shih HY Bildsten L Shara MM Bibby J Filippenko AV Ganeshalingam M Silverman JM Kulkarni SR Law NM Poznanski D Quimby RM McCully C Patel B Maguire K Shen KJ 《Nature》2011,480(7377):348-350
Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are two classes of models: double-degenerate (involving two white dwarfs in a close binary system) and single-degenerate models. In the latter, the primary white dwarf accretes material from a secondary companion until conditions are such that carbon ignites, at a mass of 1.38 times the mass of the Sun. The type Ia supernova SN 2011fe was recently detected in a nearby galaxy. Here we report an analysis of archival images of the location of SN 2011fe. The luminosity of the progenitor system (especially the companion star) is 10-100 times fainter than previous limits on other type Ia supernova progenitor systems, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf. 相似文献
66.
Collins PY Patel V Joestl SS March D Insel TR Daar AS;Scientific Advisory Board the Executive Committee of the Grand Challenges on Global Mental Health Anderson W Dhansay MA Phillips A Shurin S Walport M Ewart W Savill SJ Bordin IA Costello EJ Durkin M Fairburn C Glass RI Hall W Huang Y Hyman SE Jamison K Kaaya S Kapur S Kleinman A Ogunniyi A Otero-Ojeda A Poo MM Ravindranath V Sahakian BJ Saxena S Singer PA Stein DJ 《Nature》2011,475(7354):27-30
67.
68.
Riboswitches are metabolite-sensing RNAs, typically located in the non-coding portions of messenger RNAs, that control the synthesis of metabolite-related proteins. Here we describe a 2.05 angstroms crystal structure of a riboswitch domain from the Escherichia coli thiM mRNA that responds to the coenzyme thiamine pyrophosphate (TPP). TPP is an active form of vitamin B1, an essential participant in many protein-catalysed reactions. Organisms from all three domains of life, including bacteria, plants and fungi, use TPP-sensing riboswitches to control genes responsible for importing or synthesizing thiamine and its phosphorylated derivatives, making this riboswitch class the most widely distributed member of the metabolite-sensing RNA regulatory system. The structure reveals a complex folded RNA in which one subdomain forms an intercalation pocket for the 4-amino-5-hydroxymethyl-2-methylpyrimidine moiety of TPP, whereas another subdomain forms a wider pocket that uses bivalent metal ions and water molecules to make bridging contacts to the pyrophosphate moiety of the ligand. The two pockets are positioned to function as a molecular measuring device that recognizes TPP in an extended conformation. The central thiazole moiety is not recognized by the RNA, which explains why the antimicrobial compound pyrithiamine pyrophosphate targets this riboswitch and downregulates the expression of thiamine metabolic genes. Both the natural ligand and its drug-like analogue stabilize secondary and tertiary structure elements that are harnessed by the riboswitch to modulate the synthesis of the proteins coded by the mRNA. In addition, this structure provides insight into how folded RNAs can form precision binding pockets that rival those formed by protein genetic factors. 相似文献
69.
70.
Zusammenfassung Zwischen DNS normaler und neoplastischer Zellen besteht ein wesentlicher biochemischer Unterschied. 相似文献