DNA contents inPaspalum spp. determined by flow cytometry     

R. L. Jarret  P. Ozias-Akins  S. Phatak  R. Nadimpalli  R. Duncan  S. Hiliard 《Genetic Resources and Crop Evolution》1995,42(3):237-242

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Characterization of the supernumerary chromosome in cat eye syndrome   总被引：18，自引：0，他引：18  

H E McDermid  A M Duncan  K R Brasch  J J Holden  E Magenis  R Sheehy  J Burn  N Kardon  B Noel  A Schinzel 《Science (New York, N.Y.)》1986,232(4750):646-648

Most individuals with cat eye syndrome (CES) have a supernumerary bisatellited chromosome which, on the basis of cytogenetic evidence, has been reported to originate from either chromosome 13 or 22. To resolve this question, a single-copy DNA probe, D22S9, was isolated and localized to 22q11 by in situ hybridization to metaphase chromosomes. The number of copies of this sequence was determined in CES patients by means of Southern blots and densitometry analysis of autoradiographs. In patients with the supernumerary chromosome, four copies were found, whereas in one patient with a duplication of part of chromosome 22, there were three copies. Therefore, the syndrome results from the presence of either three or four copies of DNA sequences from 22q11; there is no evidence that sequences from other chromosomes are involved. This work demonstrates how DNA sequence dosage analysis can be used to study genetic disorders that are not readily amenable to standard cytogenetic analysis.  相似文献   

Timing of hot spot--related volcanism and the breakup of madagascar and India   总被引：1，自引：0，他引：1  

Storey M  Mahoney JJ  Saunders AD  Duncan RA  Kelley SP  Coffin MF 《Science (New York, N.Y.)》1995,267(5199):852-855

Widespread basalts and rhyolites were erupted in Madagascar during the Late Cretaceous. These are considered to be related to the Marion hot spot and the breakup of Madagascar and Greater India. Seventeen argon-40/argon-39 age determinations reveal that volcanic rocks and dikes from the 1500-kilometer-long rifted eastern margin of Madagascar were emplaced rapidly (mean age = 87.6 +/- 0.6 million years ago) and that the entire duration of Cretaceous volcanism on the island was no more than 6 million years. The evidence suggests that the thick lava pile at Volcan de l'Androy in the south of the island marks the focal point of the Marion hot spot at approximately 88 million years ago and that this mantle plume was instrumental in causing continental breakup.  相似文献   

Welfare dependence within and across generations   总被引：2，自引：0，他引：2  

G J Duncan  M S Hill  S D Hoffman 《Science (New York, N.Y.)》1988,239(4839):467-471

A central question in the debate about the effects of welfare programs is whether their intended positive results--providing needed resources to recipients and their children--outweigh any unintended negative results--for example, the breaking up of families, reduction in work effort, or the fostering of a welfare "culture" that is passed on from parent to child. Recent research shows that although work effort is affected adversely by the generosity of welfare programs, effects on family structure appear quite weak, most welfare experiences are relatively short, and the majority of women who grew up in homes heavily dependent on welfare do not rely on those programs when they are young adults.  相似文献   

镉对鲫非特异性免疫力的影响   总被引：7，自引：2，他引：7  

丁磊  黄鹤忠  吴康  蔡春芳  吴萍 《农业环境科学学报》2004,23(1):64-66

采用毒性实验方法研究了镉对鲫非特异性免疫力的影响,确定镉诱导免疫毒性效应及其毒性参数。在试验剂量和时间范围内的结果显示,镉对鲫白细胞数量(WBC)、中性粒细胞的吞噬率(PR)和补体50%溶血活性(CH50)均有剂量-效应关系、时间-效应关系和Hormesis现象,1.25mg·kg-1注射染Cd2+胁迫时对WBC、PR和CH50有激活作用,2.5和3.75mg·kg-1注射染Cd2+胁迫时对WBC、PR和CH50有抑制作用;WBC顶点所对应的时间为染Cd2+后4d,PR顶点所对应的时间为染Cd2+后2d,CH50顶点所对应的时间为染Cd2+后1d。所以Cd2+对鲫具有明显的免疫毒性。  相似文献   

小鼠血清抗磺胺二甲氧嘧啶抗体的研制   总被引：1，自引：0，他引：1  

曹盛丰 《上海交通大学学报(农业科学版)》2007,25(2):96-98,119

将磺胺二甲氧嘧啶(SDM)与载体牛甲状腺球蛋白(BTG)偶联,构建SDM完全抗原SDM-BTG。用SDM-BTG免疫小鼠,诱导小鼠产生血清抗SDM抗体。ELISA检测表明:SDM-BTG免疫小鼠所产生的多克隆抗体与SDM-BSA包被抗原的结合有较强的特异性和较高的亲和力。  相似文献   

Deformation on nearby faults induced by the 1999 Hector Mine earthquake   总被引：3，自引：0，他引：3  

Fialko Y  Sandwell D  Agnew D  Simons M  Shearer P  Minster B 《Science (New York, N.Y.)》2002,297(5588):1858-1862

Interferometric Synthetic Aperture Radar observations of surface deformation due to the 1999 Hector Mine earthquake reveal motion on several nearby faults of the eastern California shear zone. We document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer-wide zones centered on pre-existing faults. Portions of some faults experienced retrograde (that is, opposite to their long-term geologic slip) motion during or shortly after the earthquake. The observed deformation likely represents elastic response of compliant fault zones to the permanent co-seismic stress changes. The induced fault displacements imply decreases in the effective shear modulus within the kilometer-wide fault zones, indicating that the latter are mechanically distinct from the ambient crustal rocks.  相似文献   

Rational design of peptide-based HIV proteinase inhibitors   总被引：48，自引：0，他引：48  

N A Roberts  J A Martin  D Kinchington  A V Broadhurst  J C Craig  I B Duncan  S A Galpin  B K Handa  J Kay  A Kr?hn 《Science (New York, N.Y.)》1990,248(4953):358-361

A series of peptide derivatives based on the transition-state mimetic concept has been designed that inhibit the proteinase from the human immunodeficiency virus (HIV). The more active compounds inhibit both HIV-1 and HIV-2 proteinases in the nanomolar range with little effect at 10 micromolar against the structurally related human aspartic proteinases. Proteolytic cleavage of the HIV-1 gag polyprotein (p55) to the viral structural protein p24 was inhibited in chronically infected CEM cells. Antiviral activity was observed in the nanomolar range (with one compound active below 10 nanomolar) in three different cell systems, as assessed by p24 antigen and syncytium formation. Cytotoxicity was not detected at 10 and 5 micromolar in C8166 and JM cells, respectively, indicating a high therapeutic index for this new class of HIV proteinase inhibitors.  相似文献   

Artificial airglow excited by high-power radio waves   总被引：1，自引：0，他引：1  

Bernhardt PA  Duncan LM  Tepley CA 《Science (New York, N.Y.)》1988,242(4881):1022-1027

High-power electromagnetic waves beamed into the ionosphere from ground-based transmitters illuminate the night sky with enhanced airglow. The recent development of a new intensified, charge coupled-device imager made it possible to record optical emissions during ionospheric heating. Clouds of enhanced airglow are associated with large-scale plasma density cavities that are generated by the heater beam. Trapping and focusing of electromagnetic waves in these cavities produces accelerated electrons that collisionally excite oxygen atoms, which emit light at visible wavelengths. Convection of plasma across magnetic field lines is the primary source for horizontal motion of the cavities and the airglow enhancements. During ionospheric heating experiments, quasi-cyclic formation, convection, dissipation and reappearance of the cavites comprise a major source of long-term variability in plasma densities during ionospheric heating experiments.  相似文献   

Identity and search in social networks     

Watts DJ  Dodds PS  Newman ME 《Science (New York, N.Y.)》2002,296(5571):1302-1305

Social networks have the surprising property of being "searchable": Ordinary people are capable of directing messages through their network of acquaintances to reach a specific but distant target person in only a few steps. We present a model that offers an explanation of social network searchability in terms of recognizable personal identities: sets of characteristics measured along a number of social dimensions. Our model defines a class of searchable networks and a method for searching them that may be applicable to many network search problems, including the location of data files in peer-to-peer networks, pages on the World Wide Web, and information in distributed databases.  相似文献