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91.
Summary No qualitative differences have been found between the electrophoretic protein patterns observed in normal and in aneuploid embryos ( 3n × 2n). The overall amount of extractable protein increases, however, less rapidly in aneuploid than in normal embryos. 相似文献
92.
93.
Pryor WR Rymer AM Mitchell DG Hill TW Young DT Saur J Jones GH Jacobsen S Cowley SW Mauk BH Coates AJ Gustin J Grodent D Gérard JC Lamy L Nichols JD Krimigis SM Esposito LW Dougherty MK Jouchoux AJ Stewart AI McClintock WE Holsclaw GM Ajello JM Colwell JE Hendrix AR Crary FJ Clarke JT Zhou X 《Nature》2011,472(7343):331-333
Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus could lead to electrodynamic coupling between Enceladus and Saturn like that which links Jupiter with Io, Europa and Ganymede. Powerful field-aligned electron beams associated with the Io-Jupiter coupling, for example, create an auroral footprint in Jupiter's ionosphere. Auroral ultraviolet emission associated with Enceladus-Saturn coupling is anticipated to be just a few tenths of a kilorayleigh (ref. 12), about an order of magnitude dimmer than Io's footprint and below the observable threshold, consistent with its non-detection. Here we report the detection of magnetic-field-aligned ion and electron beams (offset several moon radii downstream from Enceladus) with sufficient power to stimulate detectable aurora, and the subsequent discovery of Enceladus-associated aurora in a few per cent of the scans of the moon's footprint. The footprint varies in emission magnitude more than can plausibly be explained by changes in magnetospheric parameters--and as such is probably indicative of variable plume activity. 相似文献
94.
Jacquemont S Reymond A Zufferey F Harewood L Walters RG Kutalik Z Martinet D Shen Y Valsesia A Beckmann ND Thorleifsson G Belfiore M Bouquillon S Campion D de Leeuw N de Vries BB Esko T Fernandez BA Fernández-Aranda F Fernández-Real JM Gratacòs M Guilmatre A Hoyer J Jarvelin MR Kooy RF Kurg A Le Caignec C Männik K Platt OS Sanlaville D Van Haelst MM Villatoro Gomez S Walha F Wu BL Yu Y Aboura A Addor MC Alembik Y Antonarakis SE Arveiler B Barth M Bednarek N Béna F Bergmann S Beri M Bernardini L 《Nature》2011,478(7367):97-102
95.
Roppolo D De Rybel B Tendon VD Pfister A Alassimone J Vermeer JE Yamazaki M Stierhof YD Beeckman T Geldner N 《Nature》2011,473(7347):380-383
Polarized epithelia are fundamental to multicellular life. In animal epithelia, conserved junctional complexes establish membrane diffusion barriers, cellular adherence and sealing of the extracellular space. Plant cellular barriers are of independent evolutionary origin. The root endodermis strongly resembles a polarized epithelium and functions in nutrient uptake and stress resistance. Its defining features are the Casparian strips, belts of specialized cell wall material that generate an extracellular diffusion barrier. The mechanisms localizing Casparian strips are unknown. Here we identify and characterize a family of transmembrane proteins of previously unknown function. These 'CASPs' (Casparian strip membrane domain proteins) specifically mark a membrane domain that predicts the formation of Casparian strips. CASP1 displays numerous features required for a constituent of a plant junctional complex: it forms complexes with other CASPs; it becomes immobile upon localization; and it sediments like a large polymer. CASP double mutants display disorganized Casparian strips, demonstrating a role for CASPs in structuring and localizing this cell wall modification. To our knowledge, CASPs are the first molecular factors that are shown to establish a plasma membrane and extracellular diffusion barrier in plants, and represent a novel way of epithelial barrier formation in eukaryotes. 相似文献
96.
Alexandre Lipschutz 《Cellular and molecular life sciences : CMLS》1946,2(11):460-461
Summary Experimental proofs are given that the antifibromatogenic action of certain steroids is not simply concomitant with their physiological activities (progestational, androgenic, cortical). It is an antiplastic actionper se, taking place directly on the territory sensitive to the neoplastic action of the strogen. Antiplastic steroids are probably an integrant part of a physiological anti-tumoural autodefensive system. 相似文献
97.
Wen‐Den Chen 《Journal of forecasting》2006,25(3):193-200
This paper discusses the Granger causality test by a spectrum estimator which allows the transfer function to have long memory properties. In traditional methodology the relationship among variables is usually assumed to be short memory or contemporaneous. Hence, we have to make sure they are of the same integrated order, else there might be a spurious regression problem. In practice, not all the variables are fractionally co‐integrated in the economic model. They may have the same random resources, but under a different integrated order. This paper focuses on how to capture the long memory Granger causality effect in the transfer function. This does not necessarily assume the variables are of the same fractional integrated order. Moreover, by the transfer function we construct an estimator to test the long memory effect with the Granger causality sense. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
98.
In this paper we present an extensive study of annual GNP data for five European countries. We look for intercountry dependence and analyse how the different economies interact, using several univariate ARIMA and unobserved components models and a multivariate model for the GNP incorporating all the common information among the variables. We use a dynamic factor model to take account of the common dynamic structure of the variables. This common dynamic structure can be non‐stationary (i.e. common trends) or stationary (i.e. common cycles). Comparisons of the models are made in terms of the root mean square error (RMSE) for one‐step‐ahead forecasts. For this particular group of European countries, the factor model outperforms the remaining ones. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
99.
J Brachet H Alexandre 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(11):895-898
The K+ ionophore valinomycin very quickly arrests cleavage in sea urchin and mouse eggs at concentrations ranging between 10 and 3 micron. Development of Axolotl and Xenopus eggs is not arrested before the blastula or gastrula stage. The motility of sea urchin sperm, blastulae and gastrulae is suppressed, within a few minutes, by 1-9 micron valinomycin. 相似文献
100.
Summary The action of angiotensin II on cardiac uptake of norepinephrine was investigated in the rat in vivo and in vitro. In contrast to desipramine, neither infusion of subpressive (10 ng/kg/min) or pressive (50–150 ng/kg/min) amounts of angiotensin on intact and/or binephrectomized rats, nor incubation of cardiac slices with angiotensin II (10–5; 10–9
M) impair the accumulation of tritiated norepinephrine and the level of metabolites. It is thus concluded that there is no inhibiting action of angiotensin II on the cardiac uptake of norepinephrine. 相似文献