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91.
Sicardy B Ortiz JL Assafin M Jehin E Maury A Lellouch E Hutton RG Braga-Ribas F Colas F Hestroffer D Lecacheux J Roques F Santos-Sanz P Widemann T Morales N Duffard R Thirouin A Castro-Tirado AJ Jelínek M Kubánek P Sota A Sánchez-Ramírez R Andrei AH Camargo JI da Silva Neto DN Gomes AR Martins RV Gillon M Manfroid J Tozzi GP Harlingten C Saravia S Behrend R Mottola S Melendo EG Peris V Fabregat J Madiedo JM Cuesta L Eibe MT Ullán A Organero F Pastor S de Los Reyes JA Pedraz S Castro A 《Nature》2011,478(7370):493-496
The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1?AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163?±?6?kilometres, density 2.52?±?0.05 grams per cm(3) and a high visible geometric albedo, Pv = 0.96(+0.09)(-0.04). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1?nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun. 相似文献
92.
In this paper, we assess the predictive content of latent economic policy uncertainty and data surprise factors for forecasting and nowcasting gross domestic product (GDP) using factor-type econometric models. Our analysis focuses on five emerging market economies: Brazil, Indonesia, Mexico, South Africa, and Turkey; and we carry out a forecasting horse race in which predictions from various different models are compared. These models may (or may not) contain latent uncertainty and surprise factors constructed using both local and global economic datasets. The set of models that we examine in our experiments includes both simple benchmark linear econometric models as well as dynamic factor models that are estimated using a variety of frequentist and Bayesian data shrinkage methods based on the least absolute shrinkage operator (LASSO). We find that the inclusion of our new uncertainty and surprise factors leads to superior predictions of GDP growth, particularly when these latent factors are constructed using Bayesian variants of the LASSO. Overall, our findings point to the importance of spillover effects from global uncertainty and data surprises, when predicting GDP growth in emerging market economies. 相似文献
93.
Dmitri B. Papkovsky Ruslan I. Dmitriev 《Cellular and molecular life sciences : CMLS》2018,75(16):2963-2980
Molecular oxygen (O2) is a key player in cell mitochondrial function, redox balance and oxidative stress, normal tissue function and many common disease states. Various chemical, physical and biological methods have been proposed for measurement, real-time monitoring and imaging of O2 concentration, state of decreased O2 (hypoxia) and related parameters in cells and tissue. Here, we review the established and emerging optical microscopy techniques allowing to visualize O2 levels in cells and tissue samples, mostly under in vitro and ex vivo, but also under in vivo settings. Particular examples include fluorescent hypoxia stains, fluorescent protein reporter systems, phosphorescent probes and nanosensors of different types. These techniques allow high-resolution mapping of O2 gradients in live or post-mortem tissue, in 2D or 3D, qualitatively or quantitatively. They enable control and monitoring of oxygenation conditions and their correlation with other biomarkers of cell and tissue function. Comparison of these techniques and corresponding imaging setups, their analytical capabilities and typical applications are given. 相似文献
94.
Snake envenomation is a socio-medical problem of considerable magnitude. About 2.5 million people are bitten by snakes annually,
more than 100,000 fatally. However, although bites can be deadly, snake venom is a natural biological resource that contains
several components of potential therapeutic value. Venom has been used in the treatment of a variety of pathophysiological
conditions in Ayurveda, homeopathy and folk medicine. With the advent of biotechnology, the efficacy of such treatments has
been substantiated by purifying components of venom and delineating their therapeutic properties. This review will focus on
certain snake venom components and their applications in health and disease.
Received 6 July 2006; received after revision 14 August 2006; accepted 28 September 2006 相似文献
95.
Glycogen synthase kinase 3β and Alzheimer’s disease: pathophysiological and therapeutic significance 总被引:3,自引:0,他引:3
Balaraman Y Limaye AR Levey AI Srinivasan S 《Cellular and molecular life sciences : CMLS》2006,63(11):1226-1235
Alzheimer’s disease (AD) is a neurodegenerative disorder associated with cognitive and behavioral dysfunction and is the leading
cause of dementia in the elderly. Several studies have implicated molecular and cellular signaling cascades involving the
serine-threonine kinase, glycogen synthase kinase β(GSK-3β) in the pathogenesis of AD. GSK-3β may play an important role in
the formation of neurofibrillary tangles and senile plaques, the two classical pathological hallmarks of AD. In this review,
we discuss the interaction between GSK-3β and several key molecules involved in AD, including the presenilins, amyloid precursor
protein, tau, and β-amyloid. We identify the signal transduction pathways involved in the pathogenesis of AD, including Wnt,
Notch, and the PI3 kinase/Akt pathway. These may be potential therapeutic targets in AD.
Received 19 December 2005; received after revision 24 January 2006; accepted 6 February 2006 相似文献
96.
Foser S Redwanz I Ebeling M Heizmann CW Certa U 《Cellular and molecular life sciences : CMLS》2006,63(19-20):2387-2396
A hallmark of resistance to type I interferons (IFNs) is the lack of antiproliferative responses. We show here that costimulation with IFN-alpha and transforming growth factor beta-1 (TGF-beta) potentiates antiproliferative activity in a sensitive (ME15) and resistant (D10) human melanoma cell line. A DNA microarray-based search for proliferation control genes involved that are cooperatively activated by IFN-alpha and TGF-beta, yielded 28 genes. Among these are the insulin-like growth factor-binding protein 3 (IGFBP3) and the calcium-binding protein S100A2; we demonstrate, that recombinant IGFBP3 protein is a potent growth inhibitor requiring TGF-beta activity. The antiproliferative activity of S100A2 is significantly enhanced by IFN-alpha in stably transfected ME15 or D10 cell lines. We show for the first time that IFN-alpha is a potent inducer of intracellular calcium release required for activation of S100A2. Our study provides a functional link between IFN-alpha and TGF-beta signaling and extends the function of IFN signaling to calcium-sensitive processes. 相似文献
97.
Niimura N Arai S Kurihara K Chatake T Tanaka I Bau R 《Cellular and molecular life sciences : CMLS》2006,63(3):285-300
Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins, a technique complimentary to ultra-high-resolution [1, 2] X-ray diffraction. Three different types of neutron diffractometers for biological macromolecules have been constructed in Japan, France and the United States, and they have been used to determine the crystal structures of proteins up to resolution limits of 1.5-2.5 A. Results relating to hydrogen positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, H/D exchange in proteins and oligonucleotides, the role of hydrogen atoms in enzymatic activity and thermostability, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed. Other techniques, such as the growth of large single crystals, the preparation of fully deuterated proteins, the use of cryogenic techniques, and a data base of hydrogen and hydration in proteins, will be described. 相似文献
98.
Shin JM Vagin O Munson K Kidd M Modlin IM Sachs G 《Cellular and molecular life sciences : CMLS》2008,65(2):264-281
Inhibition of gastric acid secretion is the mainstay of the treatment of gastroesophageal reflux disease and peptic ulceration;
therapies to inhibit acid are among the best-selling drugs worldwide. Highly effective agents targeting the histamine H2 receptor
were first identified in the 1970s. These were followed by the development of irreversible inhibitors of the parietal cell
hydrogen-potassium ATPase (the proton pump inhibitors) that inhibit acid secretion much more effectively. Reviewed here are
the chemistry, biological targets and pharmacology of these drugs, with reference to their current and evolving clinical utilities.
Future directions in the development of acid inhibitory drugs include modifications of current agents and the emergence of
a novel class of agents, the acid pump antagonists.
Received 30 May 2007; received after revision 15 August 2007; accepted 13 September 2007 相似文献
99.
Dolezel D Zdechovanova L Sauman I Hodkova M 《Cellular and molecular life sciences : CMLS》2008,65(6):964-969
Current models state that insect peripheral oscillators are directly responsive to light, while mammalian peripheral clock
genes are coordinated by a master clock in the brain via intermediate factors, possibly hormonal. We show that the expression
levels of two circadian clock genes, period (per) and Par Domain Protein 1 (Pdp1) in the peripheral tissue of an insect model species, the linden bug Pyrrhocoris apterus, are inversely affected by contrasting photoperiods. The effect of photoperiod on per and Pdp1 mRNA levels was found to be mediated by the corpus allatum, an endocrine gland producing juvenile hormone. Our results
provide the first experimental evidence for the effect of an endocrine gland on circadian clock gene expression in insects.
Received 31 October 2007; received after revision 7 January 2008; accepted 9 January 2008
D. Dolezel, L. Zdechovanova: These authors contributed equally to this work. 相似文献
100.