克雷德·汤波(1906—1997)

1997年元月17日，克雷德·汤波（ClydeWilliamTombaugh）在他新墨西哥州的家中溘然长逝，享年90岁。作为冥王星的发现者，长寿的汤波很幸运地在他生命的最后几年，看到人们终于解开了这颗本世纪行星研究史上最为扑朔迷离的“发现之谜”。汤波1906年生于伊利诺斯州斯特雷特（Streator）的一个农民家庭。当时，劳威尔（PercivalLowell）和皮克林（WilliamPickering）根据天文星与海王星轨道的不规则扰动，推测海王星之外应该还有一颗未知的行星存在。然而直至1916年劳威尔去世，人们仍然一无所获。汤波少年时代发即对天文学产生了浓厚的兴…     

远离认识偏见——直面科技界的利益冲突、义务冲突

当代科学不但发展速度惊人 ,而且对经济的影响力也在不断增加。近 2 0年来 ,在基础研究所需经费急剧上升的同时 ,科研成果到实际应用的距离越来越短 ,纯科学与应用科学的界限日趋模糊。今天的科学 ,业已成为一项可以带来巨大经济效益的投资对象。例如 ,美国自 1 980年通过“Ｂａｙｈ -Ｄｏｌｅ专利商标修正案”、 1 986年颁布“联邦政府转让法令”之后 ,出台了一系列旨在鼓励企业与大学、研究机构合作 ,加快技术转移的强有力政策。[1] 这些举措极大地推进了企业赞助大学Ｒ＆Ｄ的积极性 ,并使大学和科学家日益关注其研究成果的商业前景、知识…     

Observation of high-energy neutrinos using Cerenkov detectors embedded deep in Antarctic ice

Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations.     

Postsynaptic translation affects the efficacy and morphology of neuromuscular junctions

Long-term synaptic plasticity may be associated with structural rearrangements within the neuronal circuitry. Although the molecular mechanisms governing such activity-controlled morphological alterations are mostly elusive, polysomal accumulations at the base of developing dendritic spines and the activity-induced synthesis of synaptic components suggest that localized translation is involved during synaptic plasticity. Here we show that large aggregates of translational components as well as messenger RNA of the postsynaptic glutamate receptor subunit DGluR-IIA are localized within subsynaptic compartments of larval neuromuscular junctions of Drosophila melanogaster. Genetic models of junctional plasticity and genetic manipulations using the translation initiation factors eIF4E and poly(A)-binding protein showed an increased occurrence of subsynaptic translation aggregates. This was associated with a significant increase in the postsynaptic DGluR-IIA protein levels and a reduction in the junctional expression of the cell-adhesion molecule Fasciclin II. In addition, the efficacy of junctional neurotransmission and the size of larval neuromuscular junctions were significantly increased. Our results therefore provide evidence for a postsynaptic translational control of long-term junctional plasticity.     

Selection and validation of differentially expressed genes in head and neck cancer

We applied a robust combinatorial (multi-test) approach to microarray data to identify genes consistently up- or down-regulated in head and neck squamous cell carcinoma (HNSCC). RNA was extracted from 22 paired samples of HNSCC and normal tissue from the same donors and hybridized to the Affymetrix U95A chip. Forty-two differentially expressed probe sets (representing 38 genes and one expressed sequence tag) satisfied all statistical tests of significance and were selected for further validation. Selected probe sets were validated by hierarchical clustering, multiple probe set concordance, and target-subunit agreement. In addition, real-time PCR analysis of 8 representative (randomly selected from 38) genes performed on both microarray-tested and independently obtained samples correlated well with the microarray data. The genes identified and validated by this method were in comparatively good agreement with other rigorous HNSCC microarray studies. From this study, we conclude that combinatorial analysis of microarray data is a promising technique for identifying differentially expressed genes with few false positives.Received 12 February 2004; received after revision 22 March 2004; accepted 14 April 2004     

β2-integrins mediate a novel form of chemoresistance in cycloheximide-induced U937 apoptosis

In this study with cycloheximide (CHX, an inhibitor of protein synthesis) and the human leukaemic cell line U937, a novel form of chemoresistance, which we termed sudden drug resistance (SDR), was identified using Hoechst33258 staining, Western blott and DNA Ladder. CHX^high (10–100 g/ml)-induced apoptosis can spontaneously subside after 4–6 h or can be inhibited by short-term preincubation with CHXlow (2.5 g/ml). Unlike typical multidrug resistance, SDR is not caused by reduced drug accumulation or altered protein expression, and may be associated with a non-P-glycoprotein mechanism. To uncover this underlying mechanism, we focused on U937 cell aggregation promoted by CHX, because cell adhesion has been suggested to influence cell survival and prevent apoptosis. EDTA, or anti-CD18 monoclonal antibody, but not EGTA, acetylsalicylic acid or RGDS tetrapeptide, abrogated this homotypic aggregation and greatly increased CHX-induced apoptosis in a time-dependent manner, while fibrinogen and soluble intercellular adhesion molecule-1 exerted opposite effects. These results establish that ₂-integrin engagement is a key mediator of SDR, although it may be non-exclusive. This finding supplements the classical basis of chemoresistance and may provide another opportunity for improved leukemia therapy.Received 15 April 2004; received after revision 18 May 2004; accepted 21 June 2004     

发展中国家的科学和科学家

我1926年生于章马吉亚纳,当时为英属印度的辖地,如今属于巴基斯坦.我的家庭出身很平凡,父亲先为教师,后在当地教育部门任职;母亲是家庭妇女.我有六个兄弟和一位姐姐.虽然家境并不宽裕,但父亲极为重视我的学业,望子成龙之心甚切.他非常希望我能在竞争激烈的印度公务员考试中脱颖而出,谋得一份好工作.不过,父亲的这一愿望因为战争等原因而落空了.但对我而言,没有成为公务员却是我今生几次重要的人生转折之一.     

成为科学家意味着什么

通常将科学家描绘为知识渊博之人,这种想法是有一定道理的.为了胜任科学研究,你至少得接受某一门科学的专项训练,数学、物理学、化学或者生物学.事实上,大多数时候,通常还需要学习更多学科的知识、接受多方面的锻炼.此外,你得对自己的专业领域有真切的了解,特别是应当清楚同行正在做什么.当然,成为科学家所应知道的远远不止这些.但是,"无所不知"并非成为科学家的充分条件--正如名画收藏者并不必然是艺术家一样.衡量科学家的真正标准,是看其能否产生新的知识,或者更准确而言,看其是否具有从事科学所需的理解力.因为,科学的使命正在于理解世界.