Insecticide specific emulsifier production by hexachlorocyclohexane utilizingPseudomonas tralucida Ptm+ strain

The culture supernatant ofPseudomonas tralucida (Ptm⁺ strain) produces an agent which can emulsify the insecticide hexachlorocyclohexane (HCH), which was secreted by resting cells. Emulsifying agent is most active with -HCH, and has some activity towards other chlorinated and phosphatic insecticides. The emulsifier is a heat stable macromolecule and associated with growth of the organism on -HCH.     

Stabilization of immobilized glucose oxidase against thermal inactivation by silanization for biosensor applications

An important requirement of immobilized enzyme based biosensors is the thermal stability of the enzyme. Studies were carried out to increase thermal stability of glucose oxidase (GOD) for biosensor applications. Immobilization of the enzyme was carried out using glass beads as support and the effect of silane concentration (in the range 1-10%) during the silanization step on the thermal stability of GOD has been investigated. Upon incubation at 70 degrees C for 3h, the activity retention with 1% silane was only 23%, which increased with silane concentration to reach a maximum up to 250% of the initial activity with 4% silane. Above this concentration the activity decreased. The increased stability of the enzyme in the presence of high silane concentrations may be attributed to the increase in the surface hydrophobicity of the support. The decrease in the enzyme stability for silane concentrations above 4% was apparently due to the uneven deposition of the silane layer on the glass bead support. Further work on thermal stability above 70 degrees C was carried out by using 4% silane and it was found that the enzyme was stable up to 75 degrees C with an increased activity of 180% after 3-h incubation. Although silanization has been used for the modification of the supports for immobilization of enzymes, the use of higher concentrations to stabilize immobilized enzymes is being reported for the first time.     

The similarity of FSH-releasing factor to lamprey gonadotropin-releasing hormone III (l-GnRH-III)

To validate further the existence of a specific hypothalamic follicle stimulating hormone releasing factor (FSHRF), stalk-median eminence (SME) fragments from sheep and whole hypothalami from male rats were purified by gel filtration on Sephadex G-25, and the gonadotropin-releasing activity on hemipituitaries of rats incubated in vitro was determined by bioassay and compared with the radioimmunoassayable luteinizing hormone releasing hormone (LHRH) and lamprey gonadotropin releasing hormone (l-GnRH) activities in the fractions. The FSH-releasing fractions eluted in the same sequence of tubes from the Sephadex column found earlier by in vivo bioassay and were clearly separated from the immunoassayable and bioassayable LHRH. The radioimmunoassay (RIA) for l-GnRH recognized equally l-GnRH-I and -III but had negligible cross-reactivity with LHRH. Fractionation of rat hypothalamic extract by gel filtration on Sephadex G-25 revealed three peaks of l-GnRH determined by RIA, all of which eluted prior to the peak of LHRH. Only the second peak had FSH-releasing but not LH-releasing activity. To determine if this FSH-releasing activity was caused by the presence of l-GnRH in the fraction, the pituitaries were incubated with normal rabbit serum or the l-GnRH antiserum (1:1000), and the effect on the FSH- and LH-releasing activity of the FSH-releasing fraction and the LH-releasing activity of LHRH was determined. The antiserum had no effect on basal release of either FSH or LH but eliminated the FSH-releasing activity of the active fraction without altering the LH-releasing activity of LHRH. Since l-GnRH-I has little activity to release FSH or LH, and its activity is nonselective, whereas previous experiments have shown that l-GnRH-III highly selectively releases FSH with a potency equal to that of LHRH to release LH, the results support the hypothesis that the FSH-releasing activity observed in these experiments was caused by l-GnRH-III or a closely related peptide.     

被子植物成花诱导和性别决定机制的研究进展

开花植物具有多样性的生殖系统,其中单性花的形成是促进异交、避免自交衰退、保持遗传多样性的重要途径。单性花物种分布于被子植物不同进化分支上的事实表明,物种的雌雄异花性可能是通过不同的机制进化形成的。本文从花发育、性染色体、植物激素和环境因素四个方面,阐述了被子植物性别分化调控机制的研究进展。     

中药夏枯草对人甲状腺癌细胞系SW579增殖周期及凋亡的影响

目的:探讨夏枯草对人甲状腺癌细胞系SW579细胞生长的抑制作用及其对细胞增殖周期和凋亡的影响。方法:采用甲基噻唑(MTT)比色法和生长曲线测定不同浓度夏枯草在不同作用时间内对在体外培养SW579细胞增殖的影响,同时应用流式细胞术检测细胞增殖周期及凋亡率的变化。结果:夏枯草可在G0/G1期阻滞人甲状腺癌细胞系SW579的增殖,使S期细胞比率降低;在一定范围内,夏枯草的浓度越高、作用时间越长,对肿瘤细胞生长的抑制作用越强,凋亡率也越高。结论:夏枯草能抑制人甲状腺癌细胞系SW579细胞生长,并诱导细胞凋亡而阻止细胞周期。     

Phylogeny and evolution of Malagasy plated lizards

The endemic plated lizards (Gerrhosauridae) of Madagascar are one of the most diverse groups of lizards on the island (19 species) and are found in all ecoregions. On an island that presents so many interesting biological questions, plated lizards are an ideal group for examining patterns of diversification due to their high (but tractable) diversity and wide distribution. To resolve the taxonomy and evolutionary relationships of Malagasy plated lizards, and to explore their biogeographic history, we have generated a molecular phylogeny based on >2kb of both mitochondrial (cob, 1142 bp) and nuclear (NT-3, 419 bp; c-mos, 542 bp) DNA sequences. Phylogenetic relationships and divergence-time estimates indicate Zonosaurinae are monophyletic, arising from a single colonization event, likely from Africa to Madagascar in the Paleogene (Paleocene/early Eocene), with subsequent radiation. Furthermore, our results reveal widespread mischaracterization of species delimitation and assignment based on phenotypic characteristics. Paraphyly of a number of zonosaurine species was strongly supported by our dataset, revealing not only instances of likely cryptic species (phenotypic conservatism) but also phenotypic/genotypic discordance in the delimitation of species (phenotypic variability). These results clearly demonstrate the complex history of biotic diversification on Madagascar and provide novel insight into biogeographic patterns on the island.     

鸟苷发酵过程的多尺度问题研究

以鸟苷发酵为对象,在生物反应器中以多尺度问题的角度,对在线计算机数据进行相关分析,结合中间代谢物及有关酶活性的检测,建立了以代谢流为核心的多尺度调控方法;又通过与代谢流迁移有关的动态化学计量分析,实现了对批式发酵过程的时变系统估算,建立了主体代谢与产物形成的支路代谢间,包括能量与物质流的关系模型;最后,把具有不同生产能力菌株的关键基因与基因库数据进行了序列比较,发现了本文研究的菌株已具备高产能力,即编码sAMP合成酶的基因发生移码突变以及pur操纵子的多处突变,而中心代谢流迁移是过程优化的关键。对开展微生物功能基因组学的研究和工业过程优化的问题进行了探讨,作者提出有必要从生物反应器的系统生物学高度来认识和解决所面临的问题。     

Degradation of the herbicide diclofop-methyl in soil and influence of pesticide mixtures on its persistence

The degradation of the herbicide [¹⁴C]-diclofopmethyl was investigated in moist parabrown podzol soil at 22°C. Radiochemical procedures were used to monitor the herbicide breakdown. The mineralization of the uniformly labelled aromatic ring was pursued by trapping the¹⁴CO₂ generated for 96 days. Diclofop-methyl was rapidly degraded in the soil with a half-life of about 8 days. The major breakdown product was the corresponding acid-diclofop, formed by a very rapid hydrolysis of the esterbond. With time the acid appeared to undergo strong binding or complexing to the soil. An intermediate 4-(2,4-dichlorophenoxy) phenol was recovered from the treated soil. Concentration of the phenoxyphenol increased upto 6 days followed by quick decline. Insecticide combination of parathion + Demeton-Smethylsulphoxide partially inhibited diclofop degradation in the soil     

Etiology and control of durian foliar blight and dieback caused by Rhizoctonia solani

Foliar blight and dieback of durian seedlings and trees in Peninsular Malaysia was found to be caused by Rhizoctonia solani (teleomorph - Thanatephoms cucumeris) The fungus grew well and produced abundant sclerotia at temperatures higher than 24°C with an optimum at 28°C. It grew poorly at 35°C and did not grow at 10°C. The strains studied were found to belong to the anastomosis group AG-1. They were pathogenic on durian, papaya, cucumber, long bean, Mikania weed, padi, musk melon, mung bean, Zoysia grass, Bermuda grass, and St Augustine grass. They were mildly pathogenic on groundnut, and non-pathogenic on maize, guava and Brassica‘pak choy’. The disease was effectively controlled by foliar sprays of pencycuron and benomyl; triadimefon and an antagonistic bacterium suspension treatment were less effective and quintozene-etridiazole mixture gave poor disease control.