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排序方式: 共有100条查询结果,搜索用时 15 毫秒
91.
Thirteen of 265 deer (4.9 percent) from central Utah were positive for Elaeophora schneideri, and 180 (67.9 percent) were infected with Onchocerca cervipedis. The rate of infection for E. schneideri and O. cervipedis increased significantly with age of the host (chi - square of 17.5 and 15.5, respectively, p 相似文献
92.
A de novo Alu insertion results in neurofibromatosis type 1. 总被引:43,自引:0,他引:43
M R Wallace L B Andersen A M Saulino P E Gregory T W Glover F S Collins 《Nature》1991,353(6347):864-866
93.
Allgén L. -G. Jönsson B. Nauckhoff B. Andersen M. -L. Huus I. Møller Nielsen I. 《Cellular and molecular life sciences : CMLS》1960,16(7):325-325
Zusammenfassung Die Ausscheidung des neuen Neuroleptikums, Chlorprothixen, bei Menschen und Ratten wurde in Urin, Galle und Faeces untersucht und als einziges Abbauprodukt Chlorprothixen-Sulfoxyd gefunden. Ausscheidungsprodukte in % der verabreichten Dosis: Beim Menschen (orale Verabreichung) im Urin: 5–29% Sulfoxyd, Faeces: 0–41% unveränderter Stoff + Sulfoxyd. Bei der Ratte (orale oder parenterale Verabreichung) im Urin: bis zu 5% Sulfoxyd, Faeces: 1–7% Sulfoxyd, keine unveränderte Substanz, Galle: bis zu 24% Sulfoxyd. 相似文献
94.
95.
Redox regulation of protein tyrosine phosphatase 1B involves a sulphenyl-amide intermediate 总被引:16,自引:0,他引:16
The second messenger hydrogen peroxide is required for optimal activation of numerous signal transduction pathways, particularly those mediated by protein tyrosine kinases. One mechanism by which hydrogen peroxide regulates cellular processes is the transient inhibition of protein tyrosine phosphatases through the reversible oxidization of their catalytic cysteine, which suppresses protein dephosphorylation. Here we describe a structural analysis of the redox-dependent regulation of protein tyrosine phosphatase 1B (PTP1B), which is reversibly inhibited by oxidation after cells are stimulated with insulin and epidermal growth factor. The sulphenic acid intermediate produced in response to PTP1B oxidation is rapidly converted into a previously unknown sulphenyl-amide species, in which the sulphur atom of the catalytic cysteine is covalently linked to the main chain nitrogen of an adjacent residue. Oxidation of PTP1B to the sulphenyl-amide form is accompanied by large conformational changes in the catalytic site that inhibit substrate binding. We propose that this unusual protein modification both protects the active-site cysteine residue of PTP1B from irreversible oxidation to sulphonic acid and permits redox regulation of the enzyme by promoting its reversible reduction by thiols. 相似文献
96.
Hjorth J Sollerman J Møller P Fynbo JP Woosley SE Kouveliotou C Tanvir NR Greiner J Andersen MI Castro-Tirado AJ Castro Cerón JM Fruchter AS Gorosabel J Jakobsson P Kaper L Klose S Masetti N Pedersen H Pedersen K Pian E Palazzi E Rhoads JE Rol E van den Heuvel EP Vreeswijk PM Watson D Wijers RA 《Nature》2003,423(6942):847-850
Over the past five years evidence has mounted that long-duration (>2 s) gamma-ray bursts (GRBs)-the most luminous of all astronomical explosions-signal the collapse of massive stars in our Universe. This evidence was originally based on the probable association of one unusual GRB with a supernova, but now includes the association of GRBs with regions of massive star formation in distant galaxies, the appearance of supernova-like 'bumps' in the optical afterglow light curves of several bursts and lines of freshly synthesized elements in the spectra of a few X-ray afterglows. These observations support, but do not yet conclusively demonstrate, the idea that long-duration GRBs are associated with the deaths of massive stars, presumably arising from core collapse. Here we report evidence that a very energetic supernova (a hypernova) was temporally and spatially coincident with a GRB at redshift z = 0.1685. The timing of the supernova indicates that it exploded within a few days of the GRB, strongly suggesting that core-collapse events can give rise to GRBs, thereby favouring the 'collapsar' model. 相似文献
97.
98.
Résumé Après électrophorèse en gélose des protéines extraites de leucocytes humains, l'activité estérasique des fractions fut comparée à leur affinité pour DFP32. Les deux méthodes montraient trois fractions actives, tant en leucocytes normaux qu'en leucocytes de leucémie myéloïde. 相似文献
99.
A back-propagation programmed network that simulates response properties of a subset of posterior parietal neurons 总被引:14,自引:0,他引:14
Neurons in area 7a of the posterior parietal cortex of monkeys respond to both the retinal location of a visual stimulus and the position of the eyes and by combining these signals represent the spatial location of external objects. A neural network model, programmed using back-propagation learning, can decode this spatial information from area 7a neurons and accounts for their observed response properties. 相似文献
100.