Inexpensive, rapid procedure for bulk purification of cellulase-free beta-1,4-D-xylanase of high specific activity

A process has been developed for the bulk purification of cellulase-free beta-1,4-D-xylanase from the fungus Trichoderma harzianum E58. The process involved the primary step of ultrafiltering the culture filtrate via a 10,000-molecular-weight cut-off membrane to separate the cellulase (retentate) and xylanase (permeate) fractions. The cellulase component was concentrated by 40- to 60-fold, resulting in an enzyme complex that could effectively hydrolyze high concentrations of cellulose and xylan to glucose and xylose. The xylanase was concentrated and solvent exchanged by adsorption to a cationic exchanger, SP-ZetaPrep 250, followed by elution with a pH change in the buffer to give a purified and concentrated xylanase complex dissolved in a low-salt buffer. The resultant xylanase system was pure by the criteria of sodium dodecyl sulfate polyacrylamide electrophoresis, had a very high specific activity of 2400 IU/mg protein, was virtually free of filter paper activity, and had a ratio of contaminating filter paper activity of 2 x 10(-6) (0.009% endoglucanase activity). Approximately 3.3 g protein, which contained in excess of 7 x 10(6) IU xylanase activity, was obtained from 17 L original culture filtrate. The process scheme was designed to facilitate scale-up to an industrial level of production.     

血管紧张素原基因多态位点AGT174与原发性高血压相关性的研究

本文采用PCR、限制性酶切和电泳分型等方法,分别对90例原发性高血压患者和109例正常人血管紧张素原基因多态位点AGT174进行了检测,结果表明,高血压组中三种基因型的分布与对照组显著不同,提高该位点变异与原发性高血压的发生相关。 Abstract:The polymorphism of angiotensinogen gene at position 174 was studied in 90 cases of essential hypertension patients and 109 controls by PCR,restriction enzyme analysis and electrophoresis methods.The results showed the distribution of genetypes in hypertension group was significantly different from that of controls group.This suggested there is a correlation between the variant of AGT174 and hypertension.     

二棱大麦数量性状相关遗传力和选择指数的分析

以15个二棱大麦品种(系)材料,用相关遗传力研究大麦数量性状的相关遗传,并计算分析籽粒产量和产量构成性状所组合的各种选择指数。结果表明:各性状与单株粒重的相关遗传力均低于单株粒重的遗传力,故仅利用一个性状作间接选择的效率比对单株粒重作直接选择的效率低;在构成大麦产量的三要素中,着重提高单株穗数对产量的选择效率最大; 高产育种同时考虑与产量显著相关的性状比单纯对产量选择的效果好,其中以单株穗数、每穗粒数和籽粒产量结合起来选择的效果最佳。本文并对相关遗传力在相关遗传变异分析中的应用进行了讨论。     

花粉单倍体的遗传品质——花药培养是否降低了育种材料的农艺价值

自S.Guha和S.C.Maheshwari 1964年以曼陀罗(Datura)花药为材料,首次成功地诱导出离体幼胚以来,人们经过不断的发展和完善使之形成了一套完整的花药培养技术,即通过植物花药(或小孢子)的培养,大批创制单倍体并经染色体加倍进而获得双单倍体(Doubled haploid)植株。该技术被迅速而广泛地应用于作物育种程序之中。目前已有不少的栽培作物成功地获得了花粉植株,如:烟草、小麦、大麦、水稻、黑麦、小黑麦、玉米、甘     

The population genetic structure of clonal organisms generated by exponentially bounded and fat-tailed dispersal

Long-distance dispersal (LDD) plays an important role in many population processes like colonization, range expansion, and epidemics. LDD of small particles like fungal spores is often a result of turbulent wind dispersal and is best described by functions with power-law behavior in the tails ("fat tailed"). The influence of fat-tailed LDD on population genetic structure is reported in this article. In computer simulations, the population structure generated by power-law dispersal with exponents in the range of -2 to -1, in distinct contrast to that generated by exponential dispersal, has a fractal structure. As the power-law exponent becomes smaller, the distribution of individual genotypes becomes more self-similar at different scales. Common statistics like GST are not well suited to summarizing differences between the population genetic structures. Instead, fractal and self-similarity statistics demonstrated differences in structure arising from fat-tailed and exponential dispersal. When dispersal is fat tailed, a log-log plot of the Simpson index against distance between subpopulations has an approximately constant gradient over a large range of spatial scales. The fractal dimension D2 is linearly inversely related to the power-law exponent, with a slope of approximately -2. In a large simulation arena, fat-tailed LDD allows colonization of the entire space by all genotypes whereas exponentially bounded dispersal eventually confines all descendants of a single clonal lineage to a relatively small area.     

Plasticity in animal personality traits: does prior experience alter the degree of boldness?

Theoreticians predict that animal 'personality' traits may be maladaptive if fixed throughout different contexts, so the present study aimed to test whether these traits are fixed or plastic. Rainbow trout (Onchorhyncus mykiss) were given emboldening or negative experiences in the forms of watching bold or shy individuals responding to novelty or winning or losing fights to examine whether prior experience affected boldness. Bold individuals that lost fights or watched shy demonstrators became more shy by increasing their latency to approach a novel object, whereas shy observers that watched bold demonstrators remained cautious and did not modify their responses to novelty. Shy winners became bolder and decreased their latency to approach a novel object, but shy losers also displayed this shift. In comparison, control groups showed no change in behaviour. Bold fishes given negative experiences reduced their boldness which may be an adaptive response; however, shy fishes may base their strategic decisions upon self-assessment of their relative competitive ability and increase their boldness in situations where getting to resources more quickly ensures they outcompete better competitors.     

Efficient Gene Transfer Mediated by HIV-1-based Defective Lentivector and Inhibition of HIV-1 Repfication

Lentiviral vectors have drawn considerable attention recently and show great promise to become important delivery vehicles for future gene transfer manipulation. In the present study we have optimized a protocol for preparation of human immunodeficiency virus type-1 （HIV-1）-based defective lentiviral vectors （DLV） and characterized these vectors in terms of their transduction of different cells. Transient co-transfection of 293T packaging cells with DNA plasmids encoding lentiviral vector constituents resulted in production of high-titer DLV （0.5-1.2 × 107IU/mL）, which can be further concentrated over 100-fold through a single step ultracentrifugation. These vectors were capable of transducing a variety of cells from both primate and non-primate sources and high transduction efficiency was achieved using concentrated vectors. Assessment of potential generation of RCV revealed no detection of infection by infectious particles in DLV-transduced CEM, SupT-1 and MT-2 cells. Long-term culture of transduced cells showed a stable expression of transgenes without apparent alteration in cellular morphology and growth kinetics. Vector mobilization to untransduced cells mediated by wild-type HIV-1 infection was confirmed in this test. Challenge of transduced human T-lymphocytes with wild-type HIV-1 showed these cells are totally resistant to the viral infection. Considering the effective gene transfer and stable gene expression, safety and anti-HIV activity, these DLV vectors warrant further exploration for their potential use as a gene transfer vehicle in the development of gene therapy protocols.     

Development of Lateral-flow Immunoassay for WSSV with Polyclonal Antibodies Raised against Recombinant VP （19＋28） Fusion Protein

We have developed a sensitive and rapid lateral-flow immunoassay (LFIA) for WSSV, using colloidal gold as an indicator. The fusion protein, VP (19 28), was expressed in E. coli, purified and used to prepare polyclonal antibodies. The purified anti-VP (19 28) IgG were conjugated with colloidal gold. Unconjugated anti-VP (19 28) IgG and goat anti-rabbit IgG were immobilized on nitrocellulose membranes. After assembly, three groups (5 individual animals in each group) of shrimp samples were tested which included healthy, moribund and dead shrimps. For each group, three different tissues (body juices, gills and hepatopancreas) were tested at the same time. In parallel, all the samples were also analyzed using PCR for comparison. Out of 45 samples tested, 30 were detected as positive while 15 were classified as negative. The results of LFIA correlate with those obtained by the PCR analysis, indicating that these two detection methods have the same efficacy in the limited number of samples tested in this preliminary study.