Effects of Revegetation on Soil Microbial Biomass,Enzyme Activities,and Nutrient Cycling on the Loess Plateau in China

Revegetation is a traditional practice widely used for soil and water conservation on the Loess Plateau in China. However, there has been a lack of reports on soil microbial–biochemical indices required for a comprehensive evaluation of the success of revegetation systems. In this study, we examined the effects of revegetation on major soil nutrients and microbial–biochemical properties in an artificial alfalfa grassland, an enclosed natural grassland, and an artificial shrubland (Caragana korshinskii), with an abandoned cropland as control. Results showed that at 0–5, 5–20, and 20–40 cm depths, soil organic carbon, alkaline extractable nitrogen and available potassium were higher in natural grassland and artificial shrubland compared with artificial grassland and abandoned cropland. Soil microbial biomass C (Cmic) and phosphorous (Pmic) substantially decreased with depth at all sites, and in abandoned cropland was significantly lower than those of natural grassland, artificial grassland, and artificial shrubland at the depth of 0–5 cm. Soil microbial biomass N (Nmic) was higher in artificial shrubland and abandoned cropland compared with that in natural and artificial grasslands. Both Cmic and Pmic were significantly different between the 23‐year‐old and the 13‐year‐old artificial shrublands at the 0–5 cm depth. The activities of soil invertase, urease, and alkaline phosphatase in natural grassland and artificial shrubland were higher than those in artificial grassland and abandoned cropland. This study demonstrated that the regeneration of both natural grassland and artificial shrubland effectively preserved and enhanced soil microbial biomass and major nutrient cycling, thus is an ecologically beneficial practice for recovery of degraded soils on the Loess Plateau.     

Rapid determination of gatifloxacin in biological samples and pharmaceutical products using europium‐sensitized fluorescence spectrophotometry

A europium‐sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of gatifloxacin (GFLX). The GFLX–Eu³⁺–SDBS system was studied and it was found that SDBS significantly enhanced the fluorescence intensity of the GFLX–Eu³⁺ complex (about 25‐fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 338 and 617 nm, pH 7.5, 3.0 × 10^–6 mol/L europium(III), and 5.0 × 10^–5 mol/L SDBS. The enhanced fluorescence intensity of the system (ΔI_f) showed a good linear relationship with the concentration of GFLX over the range 1.0 × 10^–8–8.0 × 10^–7 mol/L with a correlation coefficient of 0.9990. The detection limit (S:N = 3) was determined as 1.0 × 10^–9 mol/L. This method has been successfully applied for the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range and good stability. The luminescence mechanism of the system is also discussed in detail. Copyright © 2008 John Wiley & Sons, Ltd.     

马铃薯卷叶病毒基因间隔区的克隆及序列分析

根据已报道的马铃薯卷叶病毒基因组序列．设计合成一对特异性引物,以马铃薯卷叶病毒中国分离株（ＰＬＲＶ－Ｃｈ）的ＲＮＡ为模板,反转录合成ｃＤＮＡ第一条链,经ＰＣＲ扩增后克隆于ｐＵＣ１９质粒中,进一步用ＰＣＲ鉴定、限制酶切分析和序列分析,结果表明：ＰＬＲＶ－Ｃｈ基因间隔区由１９７个核苷酸组成,与国外报道的荷兰ＰＬＲＶ－Ｎ加拿大ＰＬＲＶ－Ｃ,澳大利亚ＰＬＲＶ－Ａ,苏格兰ＰＬＲＶ－Ｓ各株系核苷酸序列具有很高的同源性,同源率依次为９９％、９８％、９３％、９８％。     

Generation of <Emphasis Type="Italic">Vibrio anguillarum</Emphasis> Ghost by Coexpression of PhiX 174 Lysis <Emphasis Type="Italic">E</Emphasis> gene and Staphylococcal Nuclease <Emphasis Type="Italic">A</Emphasis> Gene

Vibrio anguillarum ghosts (VAG) were generated, for the first time, using a conjugation vector containing a ghost bacteria inducing cassette, pRK-λP_R-cI-Elysis, in which the expression of PhiX174 lysis gene E was controlled by the P _R /cI regulatory system of lambda phage. By scanning electron microscopy, holes ranging 80–200 nm in diameter were observed in the VAG. To avoid the presence of bacterial genomic DNA and an antibiotic resistance gene in the final VAG product, we constructed a new dual vector, pRK-λP_R-cI-E-SNA, containing the E-mediated lysis cassette and the staphylococcal nuclease A (SNA)-mediated DNA degradation cassette, and generated safety-enhanced VAG for use as a fish vaccine.     

Plasticity in R/S ratio, morphology and fitness-related traits in response to reciprocal patchiness of light and nutrients in the stoloniferous herb, Glechoma longituba L

Clonal fragments of the stoloniferous herb Glechoma longituba were subjected to a complementary patchiness of light and soil nutrients including two spatially homogeneous treatments (SR–SR and IP–IP) and two spatially heterogeneous treatments (IP–SR and SR–IP). SR and IP indicate patches (shaded, rich) with low light intensity (shaded, S), high nutrient availability (rich, R) and patches (illuminated, poor) with high light intensity (illuminated, I) and low nutrient availability (poor, P), respectively. Plasticity of the species in root–shoot ratio, fitness-related traits (biomass, number of ramets and dry weight per ramet) and clonal morphological traits (length and specific length of stolon internodes, area and specific area of laminae, length and specific length of petioles) were experimentally examined. The aim is to understand adaptation of G. longituba to the environment with reciprocal patches of light and soil nutrients by plasticities both in root–shoot ratio and in (clonal) morphology. Our experiment revealed performance of the clonal fragments growing from patches with high light intensity and low soil nutrient availability into the adjacent opposite patches was increased in terms of the fitness-related characters. R/S ratio and clonal morphology were plastic. Meanwhile, the capture of light resource from the light-rich patches was enhanced while the capture of soil nutrients from either the nutrient-rich or the nutrient-poor patches was not. Analysis of cost and benefit disclosed positive effects of clonal integration on biomass production of ramets in the patches with low light intensity and high soil nutrient availability. These results suggest an existence of reciprocal translocation of assimilates and nutrients between the interconnected ramets. The reinforced performance of the clonal fragments seems to be related with specialization of clonal morphology in the species.     

检测低拷贝数HBVDNA含量的临床研究

目的:了解不同试剂在应用实时荧光定量聚合酶链反应(FQ-PCR)以及巢式PCR方法在检测低拷贝数的HBV DNA量的差异与灵敏度.方法:用上海复星医学科技发展有限公司(A方法)检测出了68例HBV DNA结果为5.1× 101-1.0× 103拷贝数/毫升的低拷贝数标本.然后,三家不同公司的试剂(方法B、方法C、方法D)对这些样本进行复核.另外,巢式聚合酶链反应PCR法检测此68例标本.随访巢式PCR结果为阳性的10例低拷贝数HBV DNA的病人.结果:用四种方法(A、B、C、D)检测的68个样本的HBV DNA拷贝数结果如下:无拷贝(0,9,12,4);101-102 (21,17,18,22);102-103(47,36,28,35),大于103(0,6,10,7).同时,用巢式聚合酶链反应检测此68例标本,有55例检测为阳性,有13为阴性结果.巢式PCR结果为阳性的10例低拷贝数HBV DNA含量的病人,随访发现此10病人有8例均在1～3月后出现HBV DNA的反跳,并伴肝功能的不正常,其HBV DNA的含量均在104拷贝数/毫升以上.结论:目前所用的实时荧光定量聚合酶链反应(FQ-PCR)的方法和试剂对低拷贝数HBV DNA存在不稳定性和不确定性.巢式PCR法对低拷贝数HBV DNA的检测灵敏度要远高于实时荧光定量PCR法.该研究提示测对抗病毒治疗过程中患者进行低拷贝数HBV DNA的检将提供有效的药物评价和预后信息.