通向自然的天路：川藏线——修筑川藏线一定要懂得：惹不起躲着走

把人与自然的和谐看作两者利益的最大公约数，这是王世麟将军的见解，这个说法倒是很精辟。他是我们这次访问中军阶最高的。1951年参军至今，他一辈子都在跟川藏线打交道，从最初的修筑公路，到后来的负责运输后勤工作，甚至有过步行墨脱21天的经历。坐在他家精致的小院里，离休的老人，心又飞回了修路的年代。多少年的军旅生涯，养成了他讲话干脆利落的风格。[编者按]     

在川藏线上走尽量避开灾害季节

“走在川藏线上,最安全的办法是避开灾害季节”,这是张全林反复强调的一句话。他现任成都军区川藏兵站部部长,军衔大校。从20岁当兵至今,33年来,在这条生死线上往返了150多次。听说,他不知多少次替新兵将车一辆辆开过最险地段。但是出乎意料,坐在我们面前的他,不是单一的英雄色彩,纵然坚强,纵然无畏,但谈到与自然打交道时,他极度冷静和理性的话语,让我们无法不敬佩。如果说川藏线打炼出来的人同时兼备勇敢和理性的话,那么在张全林的身上我们看到了这种品格的完美和极致。[编者按]     

川藏线记载着无尽的故事——寻找泡桐岗

我跑横断山那几年．爸爸已经90高龄．他天天自己“北京拨电话来询问我的行踪 ．连犄角旮旯的小地名也不放过。可惜当时我并不理解。我所追踪的那片珍稀植物的避难所,那个被称为“地球表面最凶险的褶皱区”．正是长征中爸爸最难忘的地方。[编者按]     

保护区内的建设项目一定要慎之又慎

中国的自然保护区所面临的困境折射出我们国家在社会经济发展中的深层次矛盾。保护与发展常常遇到的是两难的选择和多种利益的博弈与协调。而在博弈与协调过程中我们需要制度的完善和创新。老铁山作为千万只候鸟迁飞的驿站,湿地对乌的影响很大,因为它们要在这里补充足够的营养才能飞越渤海,所以,保护好蛇岛和老铁山,以及湿地是非常重要的。当这些生态系统改变其功能时,它会对鸟类及当地生态环境带来什么样的影响,需要有科学依据,特别是进行科学的环境影响评价。但是,目前我国现有的环境影响评价存在制度上的漏洞,比如对会带来一些未知影响的项目应当如何考虑,这是我国保护区面临的现实问题。许多保护区尽管在人力物力严重短缺的情况下开展了很多科研工作,积累了一定的基础数据,但仍然有很多问题需要进一步研究探讨,才能对一些建设项目的影响作出预测。从这一点来看,保护区内的科研和监测需要国家、科研单位、社会给予更多支持。同时,对尚未能够预测的项目一定要慎重评价,许多保护区对看不准影响的项目采取暂不实施的做法,很值得借鉴,因为一旦造成不可逆转的影响,也许将是人类的悲哀。像蛇岛老铁山这样一个没有纳入遗产名录的“遗产”,应该引起全社会的关注和重视,在它的里边和周边的一切建设项目一定要慎之又慎。     

科学技术这一仗一定要打好

我们厂共有300余人,以生产味精为主。几年来,在毛主席革命路线指引下,放手发动群众,充分发挥技术人员的作用,大搞科学实验,有力的促进了生产发展。1974年味精产量创造了年产最高记录,比1973年增长23.5％,生产成本比1966年降低42％。     

"是牛羊养了我,我要懂得养育之恩"

今天,生态文化节已经开幕了,从最开始的庄严的煨桑仪式到转山活动,牧人们个个都带着虔敬的表情参与其中,而我们则离开了飘洒着风马的赛马场,继续我们的访问。今天要找到合适的访问对象恐怕更加困难了,大部     

Detours in bird migration

Bird migration routes often follow detours where passages across ecological barriers are reduced in extent. This occurs in spite of the fact that long barrier crossings are within the birds' potential flight range capacity. Long-distance flights are associated with extra energy costs for transport of the heavy fuel loads required. This paper explores how important the fuel transport costs, estimated on the basis of flight mechanics, may be to explain detours for birds migrating by flapping flight. Maximum detours in relation to expanse of the barrier are predicted for cases where birds travel along the detour by numerous short flights and small fuel reserves, divide the detour into a limited number of flight steps, and where a reduced barrier passage is included in the detour. The principles for determining the optimum route, often involving a shortcut across part of the barrier, are derived. Furthermore, the effects of differences in fuel deposition rates and in transport costs for the profitability of detours are briefly considered. An evaluation of a number of observed and potential detours in relation to the general predictions of maximum detours, indicates that reduction of fuel transport costs may well be a factor of widespread importance for the evolution of detours in bird migration at wide ecological barriers.     

两种pUC18高效T载体的构建

T载体是用于直接克隆PCR产物的线性载体.在此之前,克隆PCR片段时一般先用Klenow片段酶或T4DNA聚合酶削平PCR产物两端,克隆过程中又大都不能使用碱性磷酸酶为载体片段脱磷,因为绝大多数PCR引物5’端未磷酸化,T载体的诞生使分子生物学工作者摆脱了这一窘境,而且,T载体的3’端突出的T碱基与PCR产物3’端由于Taq酶非模板依赖的末端转移酶活性而添加的A碱基[1]互补,使载体与PCR产物的连接效率大大提高.由于具有上述优点,T载体从一产生就引起人们极大的兴趣,很多公司也相继推出了各自的T载体系统,并运用该技术改造了很多传统载体.本…     

Construction of a Highly Active Xylanase Displaying Oleaginous Yeast: Comparison of Anchoring Systems

Three Yarrowia lipolytica cell wall proteins (YlPir, YlCWP1 and YlCBM) were evaluated for their ability to display the xylanase TxXYN from Thermobacillus xylanilyticus on the cell surface of Y. lipolytica. The fusion proteins were produced in Y. lipolytica JMY1212, a strain engineered for mono-copy chromosomal insertion, and enabling accurate comparison of anchoring systems. The construction using YlPir enabled cell bound xylanase activity to be maximised (71.6 U/g). Although 48% of the activity was released in the supernatant, probably due to proteolysis at the fusion zone, this system is three times more efficient for the anchoring of TxXYN than the YlCWP1 system formerly developed for Y. lipolytica. As far as we know it represents the best displayed xylanase activity ever published. It could be an attractive alternative anchoring system to display enzymes in Y. lipolytica.     

Detours by the blind mole-rat follow assessment of location and physical properties of underground obstacles

Orientation by an animal inhabiting an underground environment must be extremely efficient if it is to contend effectively with the high energetic costs of excavating soil for a tunnel system. We examined, in the field, the ability of a fossorial rodent, the blind mole-rat, Spalax ehrenbergi, to detour different types of obstacles blocking its tunnel and rejoin the disconnected tunnel section. To create obstacles, we dug ditches, which we either left open or filled with stone or wood. Most (77%) mole-rats reconnected the two parts of their tunnel and accurately returned to their orginal path by digging a parallel bypass tunnel around the obstacle at a distance of 10-20 cm from the open ditch boundaries or 3-8 cm from the filled ditch boundaries. When the ditch was placed asymmetrically across the tunnel, the mole-rats detoured around the shorter side. These findings demonstrate that mole-rats seem to be able to assess the nature of an obstacle ahead and their own distance from the obstacle boundaries, as well as the relative location of the far section of disconnected tunnel. We suggest that mole-rats mainly use reverberating self-produced seismic vibrations as a mechanism to determine the size, nature and location of the obstacle, as well as internal self-generated references to determine their location relative to the disconnected tunnel section. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Construction and Characterization of a Highly Efficient Francisella Shuttle Plasmid

Francisella tularensis is a facultative intracellular pathogen that infects a wide variety of mammals and causes tularemia in humans. It is recognized as a potential agent of bioterrorism due to its low infectious dose and multiple routes of transmission. To date, genetic manipulation in Francisella spp. has been limited due to the inefficiency of DNA transformation, the relative lack of useful selective markers, and the lack of stably replicating plasmids. Therefore, the goal of this study was to develop an enhanced shuttle plasmid that could be utilized for a variety of genetic procedures in both Francisella and Escherichia coli. A hybrid plasmid, pFNLTP1, was isolated that was transformed by electroporation at frequencies of >1 × 10⁷ CFU μg of DNA⁻¹ in F. tularensis LVS, Francisella novicida U112, and E. coli DH5α. Furthermore, this plasmid was stably maintained in F. tularensis LVS after passage in the absence of antibiotic selection in vitro and after 3 days of growth in J774A.1 macrophages. Importantly, F. tularensis LVS derivatives carrying pFNLTP1 were unaltered in their growth characteristics in laboratory medium and macrophages compared to wild-type LVS. We also constructed derivatives of pFNLTP1 containing expanded multiple cloning sites or temperature-sensitive mutations that failed to allow plasmid replication in F. tularensis LVS at the nonpermissive temperature. In addition, the utility of pFNLTP1 as a vehicle for gene expression, as well as complementation, was demonstrated. In summary, we describe construction of a Francisella shuttle plasmid that is transformed at high efficiency, is stably maintained, and does not alter the growth of Francisella in macrophages. This new tool should significantly enhance genetic manipulation and characterization of F. tularensis and other Francisella biotypes.     

两种高效 RNA 干涉载体系统的构建及应用

在真核细胞基因功能研究中, RNA 干涉 (RNAi) 已成为一种强有力的选择性沉默基因表达的实验工具. 建立一套可在哺乳动物培养细胞中高效、经济地表达 siRNA 的载体系统是 RNA 干涉研究的必要前提之一. 从 HepG2 细胞基因组 DNA 中克隆得到 H1 全长启动子 (374 bp),以之为基础构建了两套 RNA 干涉载体系统, pSL 和带有绿色荧光蛋白 (EGFP) 标签的 pESL ,并对 p53 基因进行了相应的 RNA 干涉研究. 干涉质粒瞬时转染 HepG2 细胞后,分别利用半定量 RT-PCR 和蛋白质印迹检测 p53 表达水平. 与商品化载体 pSilencer^TM 3.1-H1 hygro 相比, pSL 和 pESL 对 p53 基因表达具有更高的干涉效率. 结果显示：干涉载体 pSL 和 pESL 能高效特异地下调目的基因表达,可作为哺乳动物中基因功能分析的有效工具.     

Melatonin in Plants: More Studies are Necessary

Melatonin (N-acetyl-5-methoxytryptamine) is a biogenic indoleamine structurally related with other important substances such as tryptophan, serotonin, indole-3-acetic acid (IAA). In mammals, birds, reptiles and fish melatonin is a biological modulator of several timing (circadian) processes such as mood, sleep, sexual behavior, immunological status, etc. Since its discovery in plants in 1995 several physiological roles, including a possible role in flowering, circadian rhythms and photoperiodicity and as growth-regulator have been postulated. Recently, a possible role in rhizogenesis in lupin has also been proposed. Here, these actions of melatonin in plant development are commented on and some other interesting recent data concerning melatonin in plants are also discussed. The need for more investigation into melatonin and plants is presented as an obvious conclusion.Key Words: antioxidant, auxin, ethylene, flowering, growth, IAA, melatonin, rhizogenesisMelatonin (N-acetyl-5-methoxytryptamine) is well known in human and animal physiology, but is an unknown player in the physiology of plants. Many studies have clearly demonstrated its presence in different parts of plants such as the root, stem, leaf, flower, fruit and seed.^1–3 In addition to its phytochemical interest (natural melatonin is absorbed by the human digestive tract), this compound has aroused attention as a possible signal molecule in plant physiology.^4,5 From it discovery in plants in 1995, some authors have postulated many physiological roles for melatonin, although, in general, research into melatonin in plants is clearly insufficient. Only the possible role of melatonin in flowering and as growth promotor have been studied with some detail. As regards the former, the studies of Kolar''s group on the role of melatonin as plant rhythm regulator provided interesting data, pointing to melatonin''s action in the later stages of the flowering process.^6,7 Melatonin seems to have a more obvious effect in the growth process of some species, as has been demonstrated by our group. Our data showed that melatonin has a growth-promoting effect on aerial organs (epi- and hypocotyls, coleoptiles) and a growth-inhibitory effect on roots, in a similar way to auxins.^8,9 Other authors, too, have provided evidence on the possible growth-promoting activity of melatonin in Glycyrrhiza uralensis, which doubled its melatonin content in roots in the 3–6 month development period.¹⁰ A more recent paper, presented data concerning the effect that melatonin has on the rhizogenesis process. Melatonin produces and/or activates the generation of root primordia and their subsequent growth into lateral roots and adventitious roots in Lupinus albus.¹¹ Studies on melatonin in vegetative plant development pointed to a relationship between IAA and melatonin but more data are necessary to identify the particular interconnection. The most recent data in this respect, established the effect of melatonin on the enzymatic activity of ACC oxidase in hypocotyls and roots of Lupinus albus, pointing to the possible regulation of ethylene production in these vegetative organs.¹²One aspect that has slowed down research into melatonin in plants is the difficulty involves in its detection, identification and measurement of melatonin in plants. Because the high degree of interference caused by melatonin-immunodetection kits using plant samples, the habitual use of the liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been crucial.¹³ The use of this sophisticated technique for melatonin identification combined with measuring levels by means of liquid chromatography with electrochemical or fluorescence detection seem to be an efficient methodological option. In this respect, studies such as that recently published by Cao et al. (2006),¹⁴ where a robust method for determining melatonin, serotonin and auxin in plant samples using LC-MS/MS was presented, clearly contribute to improving accurate research into melatonin in plants.Future studies on melatonin in plant physiology should take metabolic and molecular aspects into consideration. Thus, the participation of different enzymatic activities in melatonin biosynthesis and catabolism in plants appears to be an interesting challenge.⁵ Also, the presence of melatonin receptor(s) in plant samples would strongly suggest a role for melatonin. Other interesting aspects to be investigated are: the possible tissular transport of melatonin, its action as plant cell protector due to its excellent antioxidative properties, and its involvement in particular physiological processes such as germination, cell growth, senescence, flowering, etc. Lastly, we must not forget the involvement of melatonin in stress processes in animal cells, which may be mirrored to some extent in plant cells. As can be seen, much remains to be done.