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951.
952.
The anticholinergic agent atropine decreases acetylcholine concentrations and increases high-affinity choline uptake in cortical and hippocampal regions of rat brain. Administration of choline 1 hour before atropine prevents both of these atropine-induced alterations. These findings suggest that alterations in acetylcholine precursor availability may modify the effects of centrally active anticholinergic agents. 相似文献
953.
Schmidt B 《Science (New York, N.Y.)》2005,308(5726):1265-1266
954.
955.
Heckenberger MJ Kuikuro A Kuikuro UT Russell JC Schmidt M Fausto C Franchetto B 《Science (New York, N.Y.)》2003,301(5640):1710-1714
Archaeology and indigenous history of Native Amazonian peoples in the Upper Xingu region of Brazil reveal unexpectedly complex regional settlement patterns and large-scale transformations of local landscapes over the past millennium. Mapping and excavation of archaeological structures document pronounced human-induced alteration of the forest cover, particularly in relation to large, dense late-prehistoric settlements (circa 1200 to 1600 A.D.). The findings contribute to debates on human carrying capacity, population size and settlement patterns, anthropogenic impacts on the environment, and the importance of indigenous knowledge, as well as contributing to the pride of place of the native peoples in this part of the Amazon. 相似文献
956.
Preserved soft parts of ostracod specimens were recovered from beach and lagoon sediments from the Gubik Formation, of Quaternary age, at Barrow, Alaska. 相似文献
957.
Summary Somaclonal variation, which is a welcome source of genetic variation for crop breeding, is unwanted when direct regenerants have to be used in tissue culture mass propagation (eg. in many forest trees), or in the regeneration of genetically transformed plants. Random amplified polymorphic DNA (RAPD) was used to analyse somatic embryos and plants regenerated from embryogenic cell lines in Norway spruce, Picea abies (L.) Karst. RAPD facilitated the identification of clones, as material from the same cell lines shared identical patterns of amplified fragments, whereas regenerants from different cell lines were easily distinguishable by their respective patterns. For comparisons with explant donor genotypes, cell lines were initiated from cotyledons. Some of the seedlings that had parts of their cotyledons removed were grown on as control plants. Somatic embryos regenerated from cotyledon cell lines showed no aberrations in RAPD banding patterns with respect to donor plants. We conclude that gross somaclonal variation is absent in our plant regeneration system.Abbreviations ESM
embryogenic suspensor mass
- RAPD
random amplified polymorphic DNA
- RFLP
restriction fragment length polymorphism
- (2,4-dichlorophenoxy)acetic acid
2,4-D
- 1-naphthaleneacetic acid
NAA 相似文献
958.
Squyres SW Arvidson RE Ruff S Gellert R Morris RV Ming DW Crumpler L Farmer JD Marais DJ Yen A McLennan SM Calvin W Bell JF Clark BC Wang A McCoy TJ Schmidt ME de Souza PA 《Science (New York, N.Y.)》2008,320(5879):1063-1067
Mineral deposits on the martian surface can elucidate ancient environmental conditions on the planet. Opaline silica deposits (as much as 91 weight percent SiO2) have been found in association with volcanic materials by the Mars rover Spirit. The deposits are present both as light-toned soils and as bedrock. We interpret these materials to have formed under hydrothermal conditions and therefore to be strong indicators of a former aqueous environment. This discovery is important for understanding the past habitability of Mars because hydrothermal environments on Earth support thriving microbial ecosystems. 相似文献
959.
960.
The number of eggs laid by the parasitoid wasp Trichogramma varies with host volume. The duration of the wasp's initial transit across the host surface during host examination is used to determine the number of eggs laid. A 2.5-second reduction in initial transit resulted in a 30% reduction in eggs oviposited, demonstrating that these wasps measure short time intervals. This measure is used for progeny allocation independent of host body size. 相似文献