Two antimicrobial peptides from skin secretions of Rana grahami

Two antimicrobial peptides manifested a broad spectrum of anti microbial activity against various microorganisms have been isolated from skin secretions of Rana grahami. These antimicrobial peptides were named grahamin 1 and grahamin 2. Their primary Stru

Input-output relationship and economics of pangas monoculture and carp-pangas polyculture in two districts of Bangladesh

An attempt was made to study the input-output relationships and economics of pangas monoculture and carp-pangas polyculture in Bangladesh. By analyzing the data collected from 50 pangas farms and 55 carp-pangas farms, the study has investigated the production systems of two technologies and the effects of fingerling stocking and applications of feed and fertilizer on fisheries income. The data were collected from the fishermen of Trishal and Bhaluka of Mymensingh district, and Kahaloo and Adamdighee of Bogra district during 2001-02. For pangas monoculture, the stocking density was 31,561 per ha while it was 55,017 per ha in carp-pangas polyculture. Most of the farmers used urea, TSP and lime before stocking. Rice and wheat bran happened to be the most common feed ingredients for both types of culture in general. Other important ingredients used were mustard oil-cakes, rice polish, wheat flour, fish meal, bone meal, soybean meal and poultry litter. In terms of quantities, rice bran and wheat bran dominated the farmers list. Rice and wheat bran together constituted about 60% of all studied feeds. Feed cost constituted 59.13% of total costs for pangas monoculture and 67.44% for carp-pangas polyculture. Per ha productions of pangas and carp-pangas in a single culture cycle were 15,508 kg and 19,745 kg, respectively. Per ha gross profits were estimated to be Tk 310,311 and Tk 464,418 for pangas monoculture and carp-pangas polyculture, respectively. Net profit appeared to be Tk 264,216 per ha for pangas monoculture and Tk 416,509 per ha for carp-pangas polyculture. The BCRs calculated were 1.46 and 1.68 for monoculture and polyculture, respectively. The break-even costs per kg of fish were estimated at Tk 36.93 for pangas and Tk 30.93 for mixed species which was much lower than the prices the producers received. Break-even productions were estimated at 10,702 kg per ha for pangas monoculture and 11,784 kg per ha for carp-pangas polyculture. Fingerling and feed cost, and pond size significantly explained the variation of income from pangas monoculture. These factors have significantly influenced the income from the crop. Functional analysis shows that 1% increase in the feed cost might increase 0.51% of pangas income and 0.41% in carp-pangas income. No other inputs had shown this much of responses to increasing income from a fish.

Genome-wide SNP and haplotype analyses reveal a rich history underlying dog domestication

Advances in genome technology have facilitated a new understanding of the historical and genetic processes crucial to rapid phenotypic evolution under domestication(1,2). To understand the process of dog diversification better, we conducted an extensive genome-wide survey of more than 48,000 single nucleotide polymorphisms in dogs and their wild progenitor, the grey wolf. Here we show that dog breeds share a higher proportion of multi-locus haplotypes unique to grey wolves from the Middle East, indicating that they are a dominant source of genetic diversity for dogs rather than wolves from east Asia, as suggested by mitochondrial DNA sequence data(3). Furthermore, we find a surprising correspondence between genetic and phenotypic/functional breed groupings but there are exceptions that suggest phenotypic diversification depended in part on the repeated crossing of individuals with novel phenotypes. Our results show that Middle Eastern wolves were a critical source of genome diversity, although interbreeding with local wolf populations clearly occurred elsewhere in the early history of specific lineages. More recently, the evolution of modern dog breeds seems to have been an iterative process that drew on a limited genetic toolkit to create remarkable phenotypic diversity.

代谢途径的进化

生物的新陈代谢是通过一系列的代谢途径来实现的.这些调节精妙、相瓦协作的代谢途径是如何进化形成的一直是一个引人入胜的重要问题.自1945年有关该问题的第一个假说--"逆向进化假说"提出以来,迄今已发展出七种假说,包括"逆向进化假说"、"半酶理论"、"向前发展模型"、"酶的招募假说"、"多功能酶特化假说"、"整个代谢途径的复制假说"和"从头创造假说".其中最受关注的是"逆向进化假说"和"酶的招募假说",而最近提出的"多功能酶特化假说"由于有较好的理论基础和实验证据支持,也逐渐引起人们的关注.本文对这些假说逐一作了概述,并结合作者的相关研究工作,对该领域的研究现状和发展趋势进行了分析讨论和展望.

Dynamic analysis of the brushless doubly-fed induction generator during symmetrical three-phase voltage dips

The Brushless Doubly-Fed Induction Generator (BDFIG) shows commercial promise as replacement for doublyfed slip-ring generators for wind power applications by offering reduced capital and operational costs due to its brushless operation. In order to facilitate its commercial deployment, the capabilities of the BDFIG system to comply with grid code requirements have to be assessed. This paper, for the first time, studies the performance of the BDFIG under grid fault ride-through and presents the dynamic behaviour of the machine during three-phase symmetrical voltage dips. Both full and partial voltage dips are studied using a vector model. Simulation and experimental results are provided for a 180 frame BDFIG.

中等实验规模下不同营养环境对苦草(Vallisneria natans)生长的影响

本实验分别选用武汉东湖中营养和富营养湖区的湖水和底泥,并在水柱中添加氮或磷以设置高营养、中营养、中营养添加磷、中营养添加氮等四种营养环境.测定这四种营养条件下栽培苦草(Vallisneria natans)的生长和生化指标变化,探讨不同营养环境对苦草生长的影响机制.实验结果表明,苦草的生物量、叶数和新芽数等生长指标在中营养环境最高,中营养环境添加磷次之,中营养环境添加氮较低,在高营养环境最低;苦草可溶性糖和游离氨基酸含量在高营养环境中最高,在中营养环境、中营养环境添加磷和中营养环境添加氮等处理间没有明显差

独立思考 敢于创新

刘建康院士是著名的鱼类学家、生态学家。他致力于淡水鱼的生态学研究,取得显著的社会效益和经济效益。他以极大的热情投身到湖北省梁子湖和长江干流的鱼类的生态调查研究,以及东湖渔业生产、生态学的研究,从理论和实践上为我国淡水渔业与淡水生态学的发展作出了贡献。他总结的“重视科学实验,着眼社会实践;不唯上,不唯书,不唯权威;独立思考,敢于创新”的治学格言,令人深受启发。现将他在《科学的道路》发表的“独立思考,敢于创新”一文; 经作者同意,转载于后。

抗胸腺细胞抗体对中华鳖免疫系统的影响

国家自然科学基金(No.30070588;No.30371091)

湖北省五大湖泊水生植物多样性的比较研究

对湖北省五大湖泊斧头湖、洪湖、梁子湖、长湖和西凉湖水生植物多样性进行了监测、为保护与可持续利用提供依据 ,本文将断面法与GIS及GPS技术相结合 ,通过野外调查和分析前人的工作 ,揭示了五大湖泊水生植物多样性的现状和 5 0余年来的变化 ,探讨了人为干扰强度与多样性丰富程度及丧失程度的关系 ,主要结论是 :(1) 2 0 0 1年斧头湖、洪湖、梁子湖、长湖和西凉湖各分布有水生植物 6 1种、94种、87种、92种和 77种 ,种数 /面积比值以重度干扰的斧头湖和洪湖最小 (分别为 0 .5 3与 0 .2

两株水生呼肠孤病毒部分特性的比较

水生呼肠孤病毒为感染水生动物的一类病原体,隶属于呼肠孤病毒科新建水生呼肠孤病毒属。草鱼呼肠孤病毒(Grass carp reovirus,GCRV)是引起中国南方淡水养殖草鱼暴发性出血病病原,鲅鱼呼肠孤病毒(Threadfin reovirus,TFV)是引起海水养殖鲅鱼病毒病病原。本研究将GCRV与新加坡TFV分离株进行了部分特性比较研究。结果表明,GCRV与TFV均能感染CIK细胞,但对其它鱼类细胞系的敏感性有所差异。此外,凝胶电泳与逆转录聚合酶链式扩增显示,GCRV与TFV核酸属不同的基因型。在多肽

截污工程完成后武汉东湖自然净化速率探讨

根据几十年来武汉东湖水质监测资料和数据 ,在东湖截污工程完成后 ,没有新的污染物进入水体的前提下 ,对东湖水体通过自然净化恢复到健康状态所需要的时间进行了详细的数学推导和科学论证。结果表明 ,在不考虑地泥营养物质的情况下 ,东湖水体通过工业、农业、生活用水以及收获鱼类和高等植物造成的营养物的输出 ,只需要 3a左右的时间就能恢复。然而如果考虑地泥的影响 ,几十年沉积在地泥的营养物质持续向水体中释放 ,然后再通过用水及生物输出 ,东湖水质需要35a以上才能得到恢复。可见 ,截污后东湖在相当长的时间内还将处于