Behavioral effects of progesterone associated with rapid modulation of oxytocin receptors   总被引：4，自引：0，他引：4  

M Schumacher  H Coirini  D W Pfaff  B S McEwen 《Science (New York, N.Y.)》1990,250(4981):691-694

The ventromedial nuclei of the hypothalamus (VMN) are important for the control of feminine mating behavior, and hormone action within these nuclei has been causally related to behavior. Estradiol induces receptors for oxytocin in the VMN and in the area lateral to these nuclei over the course of 1 to 2 days, and progesterone causes, within 30 minutes of its application, a further increase in receptor binding and an expansion of the area covered by these receptors lateral to the VMN. The rapid progesterone effect appears to be a direct and specific effect of this steroid on the receptor or membrane, because it was produced in vitro as well as in vivo and was not mimicked by a variety of other steroids. The effect of progesterone occurred in the posterior part of the VMN, where oxytocin infusion facilitated feminine mating behavior; it did not take place in the anterior part of the VMN, where oxytocin infusion had no effect on mating behavior.  相似文献   

Productivity is a poor predictor of plant species richness   总被引：5，自引：0，他引：5  

Adler PB  Seabloom EW  Borer ET  Hillebrand H  Hautier Y  Hector A  Harpole WS  O'Halloran LR  Grace JB  Anderson TM  Bakker JD  Biederman LA  Brown CS  Buckley YM  Calabrese LB  Chu CJ  Cleland EE  Collins SL  Cottingham KL  Crawley MJ  Damschen EI  Davies KF  DeCrappeo NM  Fay PA  Firn J  Frater P  Gasarch EI  Gruner DS  Hagenah N  Hille Ris Lambers J  Humphries H  Jin VL  Kay AD  Kirkman KP  Klein JA  Knops JM  La Pierre KJ  Lambrinos JG  Li W  MacDougall AS  McCulley RL  Melbourne BA  Mitchell CE  Moore JL  Morgan JW  Mortensen B 《Science (New York, N.Y.)》2011,333(6050):1750-1753

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters(-2)) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.  相似文献   

Structures of the bacterial ribosome in classical and hybrid states of tRNA binding     

Dunkle JA  Wang L  Feldman MB  Pulk A  Chen VB  Kapral GJ  Noeske J  Richardson JS  Blanchard SC  Cate JH 《Science (New York, N.Y.)》2011,332(6032):981-984

During protein synthesis, the ribosome controls the movement of tRNA and mRNA by means of large-scale structural rearrangements. We describe structures of the intact bacterial ribosome from Escherichia coli that reveal how the ribosome binds tRNA in two functionally distinct states, determined to a resolution of ~3.2 angstroms by means of x-ray crystallography. One state positions tRNA in the peptidyl-tRNA binding site. The second, a fully rotated state, is stabilized by ribosome recycling factor and binds tRNA in a highly bent conformation in a hybrid peptidyl/exit site. The structures help to explain how the ratchet-like motion of the two ribosomal subunits contributes to the mechanisms of translocation, termination, and ribosome recycling.  相似文献   

TGF-beta signaling in fibroblasts modulates the oncogenic potential of adjacent epithelia     

Bhowmick NA  Chytil A  Plieth D  Gorska AE  Dumont N  Shappell S  Washington MK  Neilson EG  Moses HL 《Science (New York, N.Y.)》2004,303(5659):848-851

Stromal cells can have a significant impact on the carcinogenic process in adjacent epithelia. The role of transforming growth factor-beta (TGF-beta) signaling in such epithelial-mesenchymal interactions was determined by conditional inactivation of the TGF-beta type II receptor gene in mouse fibroblasts (Tgfbr2fspKO). The loss of TGF-beta responsiveness in fibroblasts resulted in intraepithelial neoplasia in prostate and invasive squamous cell carcinoma of the forestomach, both associated with an increased abundance of stromal cells. Activation of paracrine hepatocyte growth factor (HGF) signaling was identified as one possible mechanism for stimulation of epithelial proliferation. Thus, TGF-beta signaling in fibroblasts modulates the growth and oncogenic potential of adjacent epithelia in selected tissues.  相似文献   

Malaria control with genetically manipulated insect vectors     

Alphey L  Beard CB  Billingsley P  Coetzee M  Crisanti A  Curtis C  Eggleston P  Godfray C  Hemingway J  Jacobs-Lorena M  James AA  Kafatos FC  Mukwaya LG  Paton M  Powell JR  Schneider W  Scott TW  Sina B  Sinden R  Sinkins S  Spielman A  Touré Y  Collins FH 《Science (New York, N.Y.)》2002,298(5591):119-121

At a recent workshop, experts discussed the benefits, risks, and research priorities associated with using genetically manipulated insects in the control of vector-borne diseases.  相似文献   

An octane-fueled solid oxide fuel cell     

Zhan Z  Barnett SA 《Science (New York, N.Y.)》2005,308(5723):844-847

There are substantial barriers to the introduction of hydrogen fuel cells for transportation, including the high cost of fuel-cell systems, the current lack of a hydrogen infrastructure, and the relatively low fuel efficiency when using hydrogen produced from hydrocarbons. Here, we describe a solid oxide fuel cell that combines a catalyst layer with a conventional anode, allowing internal reforming of iso-octane without coking and yielding stable power densities of 0.3 to 0.6 watts per square centimeter. This approach is potentially the basis of a simple low-cost system that can provide substantially higher fuel efficiency by using excess fuel-cell heat for the endothermic reforming reaction.  相似文献   

Mirrorless lasing from mesostructured waveguides patterned by soft lithography     

Yang P  Wirnsberger G  Huang HC  Cordero SR  McGehee MD  Scott B  Deng T  Whitesides GM  Chmelka BF  Buratto SK  Stucky GD 《Science (New York, N.Y.)》2000,287(5452):465-468

Mesostructured silica waveguide arrays were fabricated with a combination of acidic sol-gel block copolymer templating chemistry and soft lithography. Waveguiding was enabled by the use of a low-refractive index (1.15) mesoporous silica thin film support. When the mesostructure was doped with the laser dye rhodamine 6G, amplified spontaneous emission was observed with a low pumping threshold of 10 kilowatts per square centimeter, attributed to the mesostructure's ability to prevent aggregation of the dye molecules even at relatively high loadings within the organized high-surface area mesochannels of the waveguides. These highly processible, self-assembling mesostructured host media and claddings may have potential for the fabrication of integrated optical circuits.  相似文献   

Emergent biogeography of microbial communities in a model ocean     

Follows MJ  Dutkiewicz S  Grant S  Chisholm SW 《Science (New York, N.Y.)》2007,315(5820):1843-1846

A marine ecosystem model seeded with many phytoplankton types, whose physiological traits were randomly assigned from ranges defined by field and laboratory data, generated an emergent community structure and biogeography consistent with observed global phytoplankton distributions. The modeled organisms included types analogous to the marine cyanobacterium Prochlorococcus. Their emergent global distributions and physiological properties simultaneously correspond to observations. This flexible representation of community structure can be used to explore relations between ecosystems, biogeochemical cycles, and climate change.  相似文献   

Internal Suberization of Plant Tissues     

Scott FM 《Science (New York, N.Y.)》1948,108(2815):654-655

  相似文献   

Exchange of Sodium Ion in Ulva lactuca     

Scott GT  DE Voe R  Hayward H  Craven G 《Science (New York, N.Y.)》1957,125(3239):160

  相似文献