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排序方式: 共有388条查询结果,搜索用时 31 毫秒
41.
Imprinted microRNA genes transcribed antisense to a reciprocally imprinted retrotransposon-like gene 总被引:18,自引:0,他引:18
Seitz H Youngson N Lin SP Dalbert S Paulsen M Bachellerie JP Ferguson-Smith AC Cavaillé J 《Nature genetics》2003,34(3):261-262
MicroRNAs (miRNAs) are an abundant class of RNAs that are approximately 21-25 nucleotides (nt) long, interact with mRNAs and trigger either translation repression or RNA cleavage (RNA interference, RNAi) depending on the degree of complementarity with their targets. Here we show that the imprinted mouse distal chromosome 12 locus encodes two miRNA genes expressed from the maternally inherited chromosome and antisense to a retrotransposon-like gene (Rtl1) expressed only from the paternal allele. 相似文献
42.
Experimental demonstration of a robust,high-fidelity geometric two ion-qubit phase gate 总被引:8,自引:0,他引:8
Leibfried D DeMarco B Meyer V Lucas D Barrett M Britton J Itano WM Jelenković B Langer C Rosenband T Wineland DJ 《Nature》2003,422(6930):412-415
Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits. 相似文献
43.
Convergent evolution of cytokines. 总被引:1,自引:0,他引:1
44.
Astrid Musnier Domitille Heitzler Thomas Boulo Sophie Tesseraud Guillaume Durand Charlotte Lécureuil Hervé Guillou Anne Poupon Eric Reiter Pascale Crépieux 《Cellular and molecular life sciences : CMLS》2009,66(21):3487-3503
The mechanisms whereby G protein-coupled receptors (GPCR) activate signalling pathways involved in mRNA translation are ill-defined,
in contrast to tyrosine kinase receptors (TKR). We compared a GPCR and a TKR, both endogenously expressed, for their ability
to mediate phosphorylation of 70-kDa ribosomal S6 kinase p70S6K in primary rat Sertoli cells at two developmental stages.
In proliferating cells stimulated with follicle-stimulating hormone (FSH), active p70S6K was phosphorylated on T389 and T421/S424,
through cAMP-dependent kinase (PKA) and phosphatidyl-inositide-3 kinase (PI3K) antagonizing actions. In FSH-stimulated differentiating
cells, active p70S6K was phosphorylated solely on T389, PKA and PI3K independently enhancing its activity. At both developmental
stages, insulin-induced p70S6K regulation was consistent with reported data. Therefore, TKR and GPCR trigger distinct p70S6K
active conformations. p70S6K developmental regulation was formalized in a dynamic mathematical model fitting the data, which
led to experimentally inaccessible predictions on p70S6K phosphorylation rate. 相似文献
45.
The utilization of the stinger and the predatory technique of the scorpion, Paruroctonus boreus, was studied under laboratory conditions. During the study, 83 feedings were observed. Age of the scorpions and the percentage of prey stung by them were used to classify the scorpions into groups. The scorpions aged 13–61 days always stung prey. After 62 days the scorpions began to selectively utilize the stinger. Utilization declined until it reached 30 percent in the adult stage. The stinger is apparently necessary for prey capture only in the early life stages. 相似文献
46.
Spatial heterogeneity in visually similar sites under Utah juniper canopy in Colorado National Monument was examined. Sample sites were arranged in a transect 24 m long, such that distances between samples were 0.013 m, 0.03 m, 1.0 m, 12 m, and 24 m. Twenty-five taxa of algae were observed, mostly belonging to Cyanophyta. Algal density varied by more than an order of magnitude within the 46 samples examined. The coefficients of variation for each distance class were very similar, demonstrating that algal patchiness can be as significant on a scale less than 0.013 m as it is on a scale of 24 m. Goodall's random pairing analysis of spatial pattern supported this conclusion by indicating that the minimal area for sampling soil algal crust populations at this site was equal to or less than 0.013 m. Because of the microscale heterogeneity in algal communities in this study, we recommend that future researchers take composite samples if they wish to quantify algae of microbiotic crusts. 相似文献
47.
Lucas Matt Stylianos Michalakis Franz Hofmann Verena Hammelmann Andreas Ludwig Martin Biel Thomas Kleppisch 《Cellular and molecular life sciences : CMLS》2011,68(1):125-137
Neuronal hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are known to modulate spontaneous activity, resting
membrane potential, input resistance, afterpotential, rebound activity, and dendritic integration. To evaluate the role of
HCN2 for hippocampal synaptic plasticity, we recorded long-term potentiation (LTP) in the direct perforant path (PP) to CA1
pyramidal cells. LTP was enhanced in mice carrying a global deletion of the channel (HCN2−/−) but not in a pyramidal neuron-restricted knockout. This precludes an influence of HCN2 located in postsynaptic pyramidal
neurons. Additionally, the selective HCN blocker zatebradine reduced the activity of oriens-lacunosum moleculare interneurons
in wild-type but not HCN2−/− mice and decreased the frequency of spontaneous inhibitory currents in postsynaptic CA1 pyramidal cells. Finally, we found
amplified LTP in the PP of mice carrying an interneuron-specific deletion of HCN2. We conclude that HCN2 channels in inhibitory
interneurons modulate synaptic plasticity in the PP by facilitating the GABAergic output onto pyramidal neurons. 相似文献
48.
Didier Fraix-Burnet Philippe Choler Emmanuel J.P. Douzery Anne Verhamme 《Journal of Classification》2006,23(1):57-78
This series of papers is intended to evaluate astrocladistics in reconstructing phylogenies of galaxies. The objective of
this second paper is to formalize the concept of galaxy formation and to identify the processes of diversification. We show
that galaxy diversity can be expected to organize itself in a hierarchy. In order to better understand the role of mergers,
we have selected a sample of 43 galaxies from the GALICS database built from simulations with a hybrid model for galaxy formation
studies. These simulated galaxies, described by 119 characters and considered as representing still undefined classes, have
experienced different numbers of merger events during evolution. Our cladistic analysis yields a robust tree that proves the
existence of a hierarchy. Mergers, like interactions (not taken into account in the GALICS simulations), are probably a strong
driver for galaxy diversification. Our result shows that mergers participate in a branching type of evolution, but do not
seem to play the role of an evolutionary clock. 相似文献
49.
Anne R. Dain 《Cellular and molecular life sciences : CMLS》1980,36(12):1358-1360
Summary An account is given of stillborn male twins born to a female Saanen goat (Capra hircus) and a Barbary ram (Ammotragus lervia). The cytogenetics of the cultured hybrid cells are described and attention is drawn to the high proportion of cells which lacked one chromosome.Acknowledgment. I. gratefully acknowledge the help of Mr G.E. Embleton who took the skin biopsy of the Barbary ram. 相似文献
50.
Lotte Hulliger M. Allgöwer Anne Arcon 《Cellular and molecular life sciences : CMLS》1963,19(11):577-580
Zusammenfassung Monocyten des strömenden Blutes könnenin vitro die morphologischen und funktionellen (Hydroxyprolinbildung) Kriterien von Fibrocyten erwerben. Die quantitative Bedeutung dieses Phänomens für den reparativen Bindegewebsaufbau wurde mit folgender Versuchsanordnung geprüft: Vergleichbare Inokulate von Monocyten (enthalten in der Leucocytenhaut des zentrifugierten Blutes) und von Fibrocyten (aus subcutanem Bindegewebe) von Kaninchen verschiedenen Geschlechts, wurden in Millipore-Kammern eingeschlossen und für 14–21 Tage in das Abdomen eines Kaninchens implantiert. Die Auszählung des Sex-Chromatins in den fibrocytären Kernen am Ende der Züchtungsperiode ergibt, dass ca. 50% monocytären Ursprunges sind. Es wird gefolgert, dass dieses Phänomen bei der eigentlichen Wundheilung noch bedeutungsvoller sein dürfte, da der Zustrom teilungsfähiger Monocyten in einem Wundgebiet kontinuierlich vor sich geht und nicht auf ein initiales Inokulum beschränkt ist. 相似文献