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21.
J T Wilson 《Nature》1970,225(5235):861-863
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Apart from echolocation and the pursuit of prey by bats, the function of ultrasound in animal communication is poorly understood. This is mainly because of the broad range of responses that it can evoke and the widely varied contexts in which it is used (for example, in rodents of the Muridae family it may indicate distress in infants or a sexual or predatory encounter in adults). Here we find that a purely ultrasonic signal is produced in the wild by a rodent of the Sciuridae family, Richardson's ground squirrel, and show that its function is to warn conspecifics of impending danger. To our knowledge, ultrasonic alarm calls have not previously been detected in any animal group, despite their twin advantages of being highly directional and inaudible to key predators. 相似文献
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Speer RJ Garton WR Morgan JF Nicholls RW Goldberg L Parkinson WH Reeves EM Jones TJ Paxton HJ Shenton DB Wilson R 《Nature》1970,226(5242):249-250
Flash spectra of the total solar eclipse throughout all its phases have been obtained in the extreme ultraviolet for the first time. 相似文献
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Marijuana affects brain function primarily by activating the G-protein-coupled cannabinoid receptor-1 (CB1), which is expressed throughout the brain at high levels. Two endogenous lipids, anandamide and 2-arachidonylglycerol (2-AG), have been identified as CB1 ligands. Depolarized hippocampal neurons rapidly release both anandamide and 2-AG in a Ca2+-dependent manner. In the hippocampus, CB1 is expressed mainly by GABA (gamma-aminobutyric acid)-mediated inhibitory interneurons, where CB1 clusters on the axon terminal. A synthetic CB1 agonist depresses GABA release from hippocampal slices. These findings indicate that the function of endogenous cannabinoids released by depolarized hippocampal neurons might be to downregulate GABA release. Here we show that the transient suppression of GABA-mediated transmission that follows depolarization of hippocampal pyramidal neurons is mediated by retrograde signalling through release of endogenous cannabinoids. Signalling by the endocannabinoid system thus represents a mechanism by which neurons can communicate backwards across synapses to modulate their inputs. 相似文献
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Infection by porcine endogenous retrovirus after islet xenotransplantation in SCID mice 总被引:56,自引:0,他引:56
van der Laan LJ Lockey C Griffeth BC Frasier FS Wilson CA Onions DE Hering BJ Long Z Otto E Torbett BE Salomon DR 《Nature》2000,407(6800):90-94
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Tat-specific cytotoxic T lymphocytes select for SIV escape variants during resolution of primary viraemia 总被引:55,自引:0,他引:55
Allen TM O'Connor DH Jing P Dzuris JL Mothé BR Vogel TU Dunphy E Liebl ME Emerson C Wilson N Kunstman KJ Wang X Allison DB Hughes AL Desrosiers RC Altman JD Wolinsky SM Sette A Watkins DI 《Nature》2000,407(6802):386-390
Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are characterized by early peaks of viraemia that decline as strong cellular immune responses develop. Although it has been shown that virus-specific CD8-positive cytotoxic T lymphocytes (CTLs) exert selective pressure during HIV and SIV infection, the data have been controversial. Here we show that Tat-specific CD8-positive T-lymphocyte responses select for new viral escape variants during the acute phase of infection. We sequenced the entire virus immediately after the acute phase, and found that amino-acid replacements accumulated primarily in Tat CTL epitopes. This implies that Tat-specific CTLs may be significantly involved in controlling wild-type virus replication, and suggests that responses against viral proteins that are expressed early during the viral life cycle might be attractive targets for HIV vaccine development. 相似文献