Stable carbon cycle-climate relationship during the Late Pleistocene   总被引：2，自引：0，他引：2  

Siegenthaler U  Stocker TF  Monnin E  Lüthi D  Schwander J  Stauffer B  Raynaud D  Barnola JM  Fischer H  Masson-Delmotte V  Jouzel J 《Science (New York, N.Y.)》2005,310(5752):1313-1317

A record of atmospheric carbon dioxide (CO2) concentrations measured on the EPICA (European Project for Ice Coring in Antarctica) Dome Concordia ice core extends the Vostok CO2 record back to 650,000 years before the present (yr B.P.). Before 430,000 yr B.P., partial pressure of atmospheric CO2 lies within the range of 260 and 180 parts per million by volume. This range is almost 30% smaller than that of the last four glacial cycles; however, the apparent sensitivity between deuterium and CO2 remains stable throughout the six glacial cycles, suggesting that the relationship between CO2 and Antarctic climate remained rather constant over this interval.  相似文献   

Detection of GTP-tubulin conformation in vivo reveals a role for GTP remnants in microtubule rescues     

Dimitrov A  Quesnoit M  Moutel S  Cantaloube I  Poüs C  Perez F 《Science (New York, N.Y.)》2008,322(5906):1353-1356

Microtubules display dynamic instability, with alternating phases of growth and shrinkage separated by catastrophe and rescue events. The guanosine triphosphate (GTP) cap at the growing end of microtubules, whose presence is essential to prevent microtubule catastrophes in vitro, has been difficult to observe in vivo. We selected a recombinant antibody that specifically recognizes GTP-bound tubulin in microtubules and found that GTP-tubulin was indeed present at the plus end of growing microtubules. Unexpectedly, GTP-tubulin remnants were also present in older parts of microtubules, which suggests that GTP hydrolysis is sometimes incomplete during polymerization. Observations in living cells suggested that these GTP remnants may be responsible for the rescue events in which microtubules recover from catastrophe.  相似文献   

A physical map of the 1-gigabase bread wheat chromosome 3B   总被引：2，自引：0，他引：2  

Paux E  Sourdille P  Salse J  Saintenac C  Choulet F  Leroy P  Korol A  Michalak M  Kianian S  Spielmeyer W  Lagudah E  Somers D  Kilian A  Alaux M  Vautrin S  Bergès H  Eversole K  Appels R  Safar J  Simkova H  Dolezel J  Bernard M  Feuillet C 《Science (New York, N.Y.)》2008,322(5898):101-104

As the staple food for 35% of the world's population, wheat is one of the most important crop species. To date, sequence-based tools to accelerate wheat improvement are lacking. As part of the international effort to sequence the 17-billion-base-pair hexaploid bread wheat genome (2n = 6x = 42 chromosomes), we constructed a bacterial artificial chromosome (BAC)-based integrated physical map of the largest chromosome, 3B, that alone is 995 megabases. A chromosome-specific BAC library was used to assemble 82% of the chromosome into 1036 contigs that were anchored with 1443 molecular markers, providing a major resource for genetic and genomic studies. This physical map establishes a template for the remaining wheat chromosomes and demonstrates the feasibility of constructing physical maps in large, complex, polyploid genomes with a chromosome-based approach.  相似文献   

On the origin of interictal activity in human temporal lobe epilepsy in vitro     

Cohen I  Navarro V  Clemenceau S  Baulac M  Miles R 《Science (New York, N.Y.)》2002,298(5597):1418-1421

The origin and mechanisms of human interictal epileptic discharges remain unclear. Here, we describe a spontaneous, rhythmic activity initiated in the subiculum of slices from patients with temporal lobe epilepsy. Synchronous events were similar to interictal discharges of patient electroencephalograms. They were suppressed by antagonists of either glutamatergic or gamma-aminobutyric acid (GABA)-ergic signaling. The network of neurons discharging during population events comprises both subicular interneurons and a subgroup of pyramidal cells. In these pyramidal cells, GABAergic synaptic events reversed at depolarized potentials. Depolarizing GABAergic responses in neurons downstream to the sclerotic CA1 region contribute to human interictal activity.  相似文献   

Stochastic pulse regulation in bacterial stress response     

Locke JC  Young JW  Fontes M  Hernández Jiménez MJ  Elowitz MB 《Science (New York, N.Y.)》2011,334(6054):366-369

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Arabidopsis EDS1 connects pathogen effector recognition to cell compartment-specific immune responses     

Heidrich K  Wirthmueller L  Tasset C  Pouzet C  Deslandes L  Parker JE 《Science (New York, N.Y.)》2011,334(6061):1401-1404

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Conical intersection dynamics in NO2 probed by homodyne high-harmonic spectroscopy     

Wörner HJ  Bertrand JB  Fabre B  Higuet J  Ruf H  Dubrouil A  Patchkovskii S  Spanner M  Mairesse Y  Blanchet V  Mével E  Constant E  Corkum PB  Villeneuve DM 《Science (New York, N.Y.)》2011,334(6053):208-212

Conical intersections play a crucial role in the chemistry of most polyatomic molecules, ranging from the simplest bimolecular reactions to the photostability of DNA. The real-time study of the associated electronic dynamics poses a major challenge to the latest techniques of ultrafast measurement. We show that high-harmonic spectroscopy reveals oscillations in the electronic character that occur in nitrogen dioxide when a photoexcited wave packet crosses a conical intersection. At longer delays, we observe the onset of statistical dissociation dynamics. The present results demonstrate that high-harmonic spectroscopy could become a powerful tool to highlight electronic dynamics occurring along nonadiabatic chemical reaction pathways.  相似文献   

Development of transgenic fungi that kill human malaria parasites in mosquitoes     

Fang W  Vega-Rodríguez J  Ghosh AK  Jacobs-Lorena M  Kang A  St Leger RJ 《Science (New York, N.Y.)》2011,331(6020):1074-1077

Metarhizium anisopliae infects mosquitoes through the cuticle and proliferates in the hemolymph. To allow M. anisopliae to combat malaria in mosquitoes with advanced malaria infections, we produced recombinant strains expressing molecules that target sporozoites as they travel through the hemolymph to the salivary glands. Eleven days after a Plasmodium-infected blood meal, mosquitoes were treated with M. anisopliae expressing salivary gland and midgut peptide 1 (SM1), which blocks attachment of sporozoites to salivary glands; a single-chain antibody that agglutinates sporozoites; or scorpine, which is an antimicrobial toxin. These reduced sporozoite counts by 71%, 85%, and 90%, respectively. M. anisopliae expressing scorpine and an [SM1](8):scorpine fusion protein reduced sporozoite counts by 98%, suggesting that Metarhizium-mediated inhibition of Plasmodium development could be a powerful weapon for combating malaria.  相似文献   

Rubidium-87/strontium-87 age of juvinas basaltic achondrite and early igneous activity in the solar system     

Allégre CJ  Birck JL  Fourcade S  Semet MP 《Science (New York, N.Y.)》1975,187(4175):436-438

A (4.60+/-0.07)x10(9) year internal isochron has been drawn for the achondrite Juvinas by the rubidium-87/strontium-87 method. Earlier petrographic investigation of achondrites supplemented by a new ion microprobe study of Juvinas strongly suggest an igneous origin for this class of meteorites. The results thus indicate that igneous activity may have rapidly followed the formation of the achondrites' parent body 4.6x10(9) years ago.  相似文献   

Integrating GIS and homing experiments to study avian movement costs     

A. Desrochers  M. Bélisle  J. Morand-Ferron  J. Bourque 《Landscape Ecology》2011,26(1):47-58

Forest cover reduction may affect movements of forest animals, but resistance to animal movements in and out of forests remains unknown despite its importance for modelling. We tested whether ovenbird (Seiurus aurocapilla), a forest-interior songbird, responds similarly to the amount of forest cover while moving locally (~2 km) and over entire landscapes (~25 km). We compared spatially-explicit simulations to field data to address the issue of resistance to movement in open areas. We caught, banded and translocated 143 territorial males 0.8–27 km away from their territory early in the breeding season. Seventy-eight percent and 50% of translocated males returned (homed) within 10 days following “local” and “landscape” translocations respectively. Independent of translocation distance, homing times increased with decreasing forest in the landscape. With a Geographic Information System (GIS), we simulated “least-cost” paths that homing ovenbirds would ideally take, when resistance to movement in open areas ranged 1–1000 times the resistance to movement in forest. The length, the cumulative cost, and variability of simulated least-cost movement paths increased with increasing resistance in open areas. With landscape translocations, least-cost path length explained homing time better than Euclidean distance, and based on an information-theoretic approach, resistance to movement was estimated to be 27 times greater in open areas than in forests (95% confidence interval: 16–45). However, least-cost path length did not perform better than Euclidean distance with local translocations, and the cumulative cost of least-cost paths was not associated to homing time in either translocation scale. We conclude that resistance to animal movements in open areas can be addressed by a combination of GIS modelling and translocation experiments, and is between one and two orders of magnitude greater than resistance to movements in forests, in the case of ovenbirds.  相似文献