Pollination of the invasive exotic shrub Lupinus arboreus (Fabaceae) by introduced bees in Tasmania     

Jane C. Stout  Andrea R. KellsDave Goulson 《Biological conservation》2002,106(3):425-434

Exotic plant invasions threaten ecological communities world-wide. Some species are limited by a lack of suitable pollinators, but the introduction of exotic pollinators can facilitate rapid spread. In Tasmania, where many non-native plants are naturalised, exotic honeybees (Apis mellifera) and bumblebees (Bombus terrestris) have become established. We determined how these species affect the pollination of Lupinus arboreus, an invasive, nitrogen-fixing shrub, which is rarely visited by native pollinators. The proportion of flowers setting seed and the number of ovules fertilised per flower were positively related to the visitation rates of both exotic bee species. There was no effect of bee visitation rates on the proportion of seeds aborted prior to maturity, possibly due to post-fertilisation environmental constraints. We conclude that the spread of B. terrestris may not alter the fecundity of L. arboreus because of the pollination service provided by A. mellifera, and discuss potential interactions between these two bee species.  相似文献   

Characterization of flavonols in cranberry (Vaccinium macrocarpon) powder     

Vvedenskaya IO  Rosen RT  Guido JE  Russell DJ  Mills KA  Vorsa N 《Journal of agricultural and food chemistry》2004,52(2):188-195

Flavonoids were extracted from cranberry powder with acetone and ethyl acetate and subsequently fractionated with Sephadex LH-20 column chromatography. The fraction eluted with a 60% methanol solution was composed primarily of phenolic constituents with maximum absorbance at 340 nm. A high-performance liquid chromatography procedure was developed, which resolved 22 distinct peaks with UV/vis and mass spectra corresponding to flavonol glycoside conjugates. Six new constituents not previously reported in cranberry or in cranberry products were determined through NMR spectroscopy to be myricetin-3-beta-xylopyranoside, quercetin-3-beta-glucoside, quercetin-3-alpha-arabinopyranoside, 3'-methoxyquercetin-3-alpha-xylopyranoside, quercetin-3-O-(6' '-p-coumaroyl)-beta-galactoside, and quercetin-3-O-(6' '-benzoyl)-beta-galactoside. Quercetin-3-O-(6' '-p-coumaroyl)-beta-galactoside and quercetin-3-O-(6' '-benzoyl)-beta-galactoside represent a new class of cranberry flavonol compounds with three conjugated components consisting of a flavonol, sugar, and carboxylic acid (benzoic or hydroxycinnamic acids). This is also the first report identifying quercetin-3-arabinoside in both furanose and pyranose forms in cranberry. Elucidation of specific flavonol glycosides in cranberry is significant since the specificity of the sugar moiety may play a role in the bioavailability of the flavonol glycosides in vivo.  相似文献   

Spread of HTLV-I between lymphocytes by virus-induced polarization of the cytoskeleton     

Igakura T  Stinchcombe JC  Goon PK  Taylor GP  Weber JN  Griffiths GM  Tanaka Y  Osame M  Bangham CR 《Science (New York, N.Y.)》2003,299(5613):1713-1716

Cell contact is required for efficient transmission of human T cell leukemia virus- type 1 (HTLV-I) between cells and between individuals, because naturally infected lymphocytes produce virtually no cell-free infectious HTLV-I particles. However, the mechanism of cell-to-cell spread of HTLV-I is not understood. We show here that cell contact rapidly induces polarization of the cytoskeleton of the infected cell to the cell-cell junction. HTLV-I core (Gag protein) complexes and the HTLV-I genome accumulate at the cell-cell junction and are then transferred to the uninfected cell. Other lymphotropic viruses, such as HIV-1, may similarly subvert normal T cell physiology to allow efficient propagation between cells.  相似文献   

Identification of active edge sites for electrochemical H2 evolution from MoS2 nanocatalysts     

Jaramillo TF  Jørgensen KP  Bonde J  Nielsen JH  Horch S  Chorkendorff I 《Science (New York, N.Y.)》2007,317(5834):100-102

The identification of the active sites in heterogeneous catalysis requires a combination of surface sensitive methods and reactivity studies. We determined the active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS2) by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution. By preparing MoS2 nanoparticles of different sizes, we systematically varied the distribution of surface sites on MoS2 nanoparticles on Au(111), which we quantified with scanning tunneling microscopy. Electrocatalytic activity measurements for hydrogen evolution correlate linearly with the number of edge sites on the MoS2 catalyst.  相似文献   

A homolog of Drosophila grainy head is essential for epidermal integrity in mice   总被引：1，自引：0，他引：1  

Ting SB  Caddy J  Hislop N  Wilanowski T  Auden A  Zhao LL  Ellis S  Kaur P  Uchida Y  Holleran WM  Elias PM  Cunningham JM  Jane SM 《Science (New York, N.Y.)》2005,308(5720):411-413

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Physics. Refining quantum cryptography     

Hughes R  Nordholt J 《Science (New York, N.Y.)》2011,333(6049):1584-1586

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Comparative genomics of trypanosomatid parasitic protozoa     

El-Sayed NM  Myler PJ  Blandin G  Berriman M  Crabtree J  Aggarwal G  Caler E  Renauld H  Worthey EA  Hertz-Fowler C  Ghedin E  Peacock C  Bartholomeu DC  Haas BJ  Tran AN  Wortman JR  Alsmark UC  Angiuoli S  Anupama A  Badger J  Bringaud F  Cadag E  Carlton JM  Cerqueira GC  Creasy T  Delcher AL  Djikeng A  Embley TM  Hauser C  Ivens AC  Kummerfeld SK  Pereira-Leal JB  Nilsson D  Peterson J  Salzberg SL  Shallom J  Silva JC  Sundaram J  Westenberger S  White O  Melville SE  Donelson JE  Andersson B  Stuart KD  Hall N 《Science (New York, N.Y.)》2005,309(5733):404-409

A comparison of gene content and genome architecture of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, three related pathogens with different life cycles and disease pathology, revealed a conserved core proteome of about 6200 genes in large syntenic polycistronic gene clusters. Many species-specific genes, especially large surface antigen families, occur at nonsyntenic chromosome-internal and subtelomeric regions. Retroelements, structural RNAs, and gene family expansion are often associated with syntenic discontinuities that-along with gene divergence, acquisition and loss, and rearrangement within the syntenic regions-have shaped the genomes of each parasite. Contrary to recent reports, our analyses reveal no evidence that these species are descended from an ancestor that contained a photosynthetic endosymbiont.  相似文献   

Unmasking the S-phase-promoting potential of cyclin B1     

Moore JD  Kirk JA  Hunt T 《Science (New York, N.Y.)》2003,300(5621):987-990

In higher eukaryotes, the S phase and M phase of the cell cycle are triggered by different cyclin-dependent kinases (CDKs). For example, in frog egg extracts, Cdk1-cyclin B catalyzes entry into mitosis but cannot trigger DNA replication. Two hypotheses can explain this observation: Either Cdk1-cyclin B fails to recognize the key substrates of its S-phase-promoting counterparts, or its activity is somehow regulated to prevent it from activating DNA synthesis. Here, we show that Cdk1-cyclin B1 has cryptic S-phase-promoting abilities that can be unmasked by relocating it from the cytoplasm to the nucleus and moderately stimulating its activity. Subcellular localization of vertebrate CDKs and the control of their activity are thus critical factors for determining their specificity.  相似文献   

Gastric cancer originating from bone marrow-derived cells     

Houghton J  Stoicov C  Nomura S  Rogers AB  Carlson J  Li H  Cai X  Fox JG  Goldenring JR  Wang TC 《Science (New York, N.Y.)》2004,306(5701):1568-1571

Epithelial cancers are believed to originate from transformation of tissue stem cells. However, bone marrow-derived cells (BMDCs), which are frequently recruited to sites of tissue injury and inflammation, might also represent a potential source of malignancy. We show that although acute injury, acute inflammation, or transient parietal cell loss within the stomach do not lead to BMDC recruitment, chronic infection of C57BL/6 mice with Helicobacter, a known carcinogen, induces repopulation of the stomach with BMDCs. Subsequently, these cells progress through metaplasia and dysplasia to intraepithelial cancer. These findings suggest that epithelial cancers can originate from marrow-derived sources and thus have broad implications for the multistep model of cancer progression.  相似文献   

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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