European Union R&D spending     

May RM 《Science (New York, N.Y.)》2003,302(5645):565-6; author reply 565-6

  相似文献   

Broader themes in paleoecology     

May RM 《Science (New York, N.Y.)》1976,194(4272):1410

  相似文献   

Taxonomic bias in conservation research     

Clark JA  May RM 《Science (New York, N.Y.)》2002,297(5579):191-192

  相似文献   

IkappaB kinases: kinsmen with different crafts     

May MJ  Ghosh S 《Science (New York, N.Y.)》1999,284(5412):271-273

  相似文献   

FRENCH INSTRUCTION AND RESEARCH IN BIOLOGY     

May RM 《Science (New York, N.Y.)》1927,65(1673):53-55

  相似文献   

Monocyte-derived human B-cell growth factor identified as interferon-beta 2 (BSF-2, IL-6)   总被引：36，自引：0，他引：36  

G Tosato  K B Seamon  N D Goldman  P B Sehgal  L T May  G C Washington  K D Jones  S E Pike 《Science (New York, N.Y.)》1988,239(4839):502-504

Soluble products of either Epstein-Barr virus (EBV)-infected B cells or activated monocytes promote the proliferation of EBV-infected B cells and permit their growth at low cell densities. This suggests that growth factors are important for B-cell immortalization by EBV. In this study, a monocyte-derived factor that promotes the growth of EBV-infected b cells was purified and identified as interferon-beta 2 (IFN-beta 2), which is also known as 26-kilodalton protein, B-cell differentiation factor (BSF-2), and interleukin-6 (IL-6). The purified protein has a specific activity of approximately 4 X 10(7) units per milligram of protein in assays of B-cell growth. Thus, IFN-beta 2/BSF-2 is a B-cell growth factor that promotes the proliferation of human B cells infected with EBV.  相似文献   

Biological populations with nonoverlapping generations: stable points, stable cycles, and chaos   总被引：24，自引：0，他引：24  

R M May 《Science (New York, N.Y.)》1974,186(4164):645-647

Some of the simplest nonlinear difference equations describing the growth of biological populations with nonoverlapping generations can exhibit a remarkable spectrum of dynamical behavior, from stable equilibrium points, to stable cyclic oscillations between 2 population points, to stable cycles with 4, 8, 16, . . . points, through to a chaotic regime in which (depending on the initial population value) cycles of any period, or even totally aperiodic but boundedpopulation fluctuations, can occur. This rich dynamical structure is overlooked in conventional linearized analyses; its existence in such fully deterministic nonlinear difference equations is a fact of considerable mathematical and ecological interest.  相似文献   

Effect of Transgene Introduction and Recloning on Efficiency of Porcine Transgenic Cloned Embryo Production In Vitro     

SJ Uhm  MK Gupta  ZC Das  JH Kim  C Park  T Kim  HT Lee 《Reproduction in domestic animals》2009,44(1):106-115

Retrovirus-mediated exogenous gene transfection of somatic cells is an efficient method to produce transgenic embryos by somatic cell nuclear transfer (SCNT). This study evaluated whether efficiency of transgenic embryos production, by SCNT using fibroblast cells transfected by retrovirus vector, is influenced by the introduced transgene and whether recloning could further improve its efficiency. Transgenic cloned embryos were produced by SCNT of porcine foetal fibroblast cells transfected by either LNβ-Z or LNβ-enhanced green fluorescent protein (EGFP) retrovirus vector and evaluated for their developmental ability in vitro . Blastomeres from four-cell stage porcine embryos, produced by SCNT of foetal fibroblast cells transfected with LNβ-EGFP retroviral vector, were subsequently recloned into enucleated metaphase II oocytes and evaluated for changes in chromatin configuration, in vitro embryo development and gene expression. Analysis of results showed that cleavage and blastocyst rates of porcine SCNT embryos, using LacZ (53.6 ± 6.4%; 12.0 ± 5.7%) or EGFP (57.5 ± 6.3%; 10.1 ± 4.1%) transfected fibroblasts, did not differ (p > 0.05) from those of non-transfected controls (60.9 ± 8.2%; 12.3 ± 4.0%). Recloning of blastomeres did not further improve the in vitro development rate. Interestingly, the nuclei of blastomere underwent slower remodelling process than somatic cell nuclei. Both cloned and recloned embryos showed 100% transgene expression and there were no evidence of mosaicism. In conclusion, our data shows that the efficiency of transgenic cloned embryos production by SCNT of somatic cells transfected with replication-defective retrovirus vector is not influenced by the transgene introduction into donor cells and recloning of four-cell stage blastomere could not further improve its efficiency.  相似文献