螅状独缩虫自然种群同工酶的研究

利用聚丙烯酰氨凝胶电泳技术 ,对采自武汉沙湖螅状独缩虫自然种群的酯酶 (EST)、苹果酸脱氢酶 (MDH)、乳酸脱氢酶 (LDH)和酸性磷酸酶 (ACP)四种同工酶酶系进行了研究。实验表明 :EST同工酶酶系由六个基因座位(Est 1—Est 6 )控制 ,其中Est 1、Est 2、Est 3和Est 5为杂合基因座位 ,而Est 4和Est 6为纯合基因座位。螅状独缩虫物种中EST同工酶四级结构既有单体也有二聚体 ;MDH同工酶酶系由五个基因座位 (Mdh 1—Mdh 5 )控制 ,其中Mdh 2和M

感湖菱群落的数量特征

　研究了湖北省感湖菱群落的水生植物种类组成、物种多样性指数、群落的垂直结构以及各种类的相对频度、相对生物量、优势度.结果表明:2002年,感湖菱群落共分布有水生植物20种,相对频度、相对生物量与优势度最高的种类均为野菱,其次是双角菱;该群落Shannon-Wiener物种多样性指数为2.3025,单位面积生物量是2183.8g/m2(鲜重);群落明显分为两层,浮叶植物层与沉水植物层,浮叶植物层的主体为野菱与双角菱,其优势度分别为21.59%和18.22%,沉水植物层的主体是密齿苦草、金鱼藻和穗花狐尾藻,其

地统计学在水生植物群落格局研究中的应用

为了研究水生植物群落的镶嵌分布格局和随着尺度变化的空间特征,应用地统计学中半方差法、半方差理论模型和分形理论,研究了湖北省保安湖沿岸带水生植物群落分布格局.在沿岸带设置了一个160 m×160 m的方形样方,采用覆盖法将整个样方划分为32×32个格子,记录各格子内出现的物种数。格子内如果有某物种,则将该格子对应的区域化随机变量赋值为1,否则赋值为0.另将群落各格内区域化随机变量赋值为各物种在该采样点随机变量值的总和.运用地统计软件GS+for Windows分析苦草、狐尾藻、金鱼藻和群落的32×32格随机

Genetic variation of fish parasite populations in historically connected habitats: undetected habitat fragmentation effect on populations of the nematode Procamallanus fulvidraconis in the catfish Pelteobagrus fulvidraco

Habitat fragmentation may have some significant effects on population genetic structure because geographic distance and physical barriers may impede gene flow between populations. In this study, we investigated whether recent habitat fragmentation affected genetic structure and diversity of populations of the nematode Procamallanus fulvidraconis in the yellowhead catfish, Pelteobagrus fin't4draco. The nematode was collected from 12 localities in 7 floodplain lakes of the Yangtze River. Using I I intersirnple sequence repeat markers, analysis of molecular variance showed that genetic diversity occurred mainly within populations (70.26%). Expected heterozygosity (He) of P. fulvidraconis was barely different between connected (0.2105) and unconnected lakes (0.2083). Population subdivision (Fst) between connected lakes (0.2177) was higher than in unconnected lakes (0. 1676). However, the connected and unconnected lakes did not Cluster into 2 clades. A Mantel test revealed significant positive correlation between genetic and geographic distances (R = 0.5335, P < 0.01). These results suggest that habitat fragmentation did not cause genetic differentiation among populations or a reduction of diversity in isolated populations of P. fulvidraconis. At least 2 factors may increase the dispersal range of the nematode, i.e., flash flooding in summer and other species of fish that may serve as the definitive hosts. Moreover, lake fragmentation is probably a recent process; population size of the nematode in these lakes is large enough to maintain Population structure.

NK-lysin of channel catfish: Gene triplication, sequence variation, and expression analysis

Antimicrobial peptides (AMPs) are important components of the host innate immune response against microbial invasion. In addition to the previously known four classes of antimicrobial peptides, a fifth class of antimicrobial peptides has been recently identified to include NK-lysins that have a globular three-dimensional structure and are larger with 74-78 amino acid residues. NK-lysin has been shown to harbor antimicrobial activities against a wide spectrum of microorganisms including bacteria, fungi, protozoa, and parasites. To date, NK-lysin genes have been reported from only a limited number of organisms. We previously identified a NK-lysin cDNA in channel catfish. Here we report the identification of two noveltypes of NK-lysin transcripts in channel catfish. Altogether, three distinct NK-lysin transcripts exist in channel catfish. In this work, their encoding genes were identified, sequenced, and characterized. We provide strong evidence that the catfish NK-lysin gene is tripled in the same genomic neighborhood. All three catfish NK-lysin genes are present in the same genomic region and are tightly linked on the same chromosome, as the same BAC clones harbor all three copies of the NK-lysin genes. All three NK-lysin genes are expressed, but exhibit distinct expression profiles in various tissues. In spite of the existence of a single copy of NK-lysin gene in the human genome, and only a single hit from the pufferfish,genome, there are two tripled clusters of NK-lysin genes on chromosome 17 of zebrafish in addition to one more copy on its chromosome 5. The similarity in the genomic arrangement of the tripled NK-lysin genes in channel catfish and zebrafish suggest similar evolution of NK-lysin genes. (c) 2005 Elsevier Ltd. All rights reserved.

锌胁迫下两种鹿角珊瑚虫黄藻荧光值的变化

本文以SeaWinds散射计为例,针对圆锥扫描散射计星下点附近区域容易产生风向模

Thermal analysis of microstructural evolution of Al2O3 surface modified layers

Solidification behavior and microstructural evolution of surface modified layers in plasma cladding technique are studied via numerical simulations. Both the coupling effect of temperature and solid volume fraction are considered in the proposed thermal analytical model, by which the transient temperature distributions are calculated and the shape of melting pool is determined. Furthermore, we perform microscopic thermal analysis on the nucleation and growth behaviors of ceramic hardening phases and dendrites, as well as the kinetics of related two-phase flow systems. By comparing with experimental observations, the evolution mechanisms of the morphology of Al2O3 ceramic hardening layer are explained. Based on the above results, a relationship among the scanning velocity of plasma stream, dendritic growth rate and the advancing speed of solid/liquid interface is found, and an energy criterion is proposed for predicting the pushing/engulfing transition of ceramic particles by grain growth fronts. (C) 2009 Elsevier B.V. All rights reserved.