柿树新害虫──柿树真绵蚧的研究

柿树真绵蚧Eupulrinariacitricola（Kuwana）的报道在国内尚属首次。近年来该虫在河北省部分柿产区日趋严重,成为柿树的一种重要害虫。该虫在当地1年发生1次。以2龄若虫在当年生枝条上越冬,第二年3月上旬越冬虫体复苏,4月20～25日成虫交配,5月20～25日雌成虫产卵,6月10～20日若虫孵化后,固定在叶片上越夏,9月下旬越夏若虫蜕皮进入2龄,并转移到当年生枝条上越冬。农药防治结果表明：久效磷、氧乐果等有机内吸剂的防治效果很好,防治的最佳时间是6月中旬。该虫在当地的主要天敌有红点瓢虫ChilocoruskuwanaeSilvestri、黑缘红瓢虫C.rubidusHope和一种寄生蜂。     

Production of dihydrodaidzein and dihydrogenistein by a novel oxygen-tolerant bovine rumen bacterium in the presence of atmospheric oxygen

The original bovine rumen bacterial strain Niu-O16, capable of anaerobically bioconverting isoflavones daidzein and genistein to dihydrodaidzein (DHD) and dihydrogenistein (DHG), respectively, is a rod-shaped obligate anaerobic bacterium. After a long-term domestication, an oxygen-tolerant bacterium, which we named Aeroto-Niu-O16 was obtained. Strain Aeroto-Niu-O16, which can grow in the presence of atmospheric oxygen, differed from the original obligate anaerobic bacterium Niu-O16 by various characteristics, including a change in bacterial shape (from rod to filament), in biochemical traits (from indole negative to indole positive and from amylohydrolysis positive to negative), and point mutations in 16S rRNA gene (G398A and G438A). We found that strain Aeroto-Niu-O16 not only grew aerobically but also converted isoflavones daidzein and genistein to DHD and DHG in the presence of atmospheric oxygen. The bioconversion rate of daidzein and genistein by strain Aeroto-Niu-O16 was 60.3% and 74.1%, respectively. And the maximum bioconversion capacity for daidzein was 1.2 and 1.6 mM for genistein. Furthermore, when we added ascorbic acid (0.15%, m/v) in the cultural medium, the bioconversion rate of daidzein was increased from 60.3% to 71.7%, and that of genistein from 74.1% to 89.2%. This is the first reported oxygen-tolerant isoflavone biotransforming pure culture capable of both growing and executing the reductive activity under aerobic conditions.     

Chemical constituents from fruits of Harrisonia perforata

Eight limonoids (1-8) including three A, B and D-seco-16-nor-type ones, 5,6-dehydrodesepoxyharperforin C2 (1), harrpernoid B (2), and its C-9S epimer, harrpernoid C (3), along with six known compounds (9-14), were isolated from fruits of Harrisonia perforata. Extensive spectroscopic analysis was used to elucidate their structures and stereochemistries. Further confirmation of structures of 1 and 2 were obtained by single-crystal X-ray diffraction. Limonoids (1-8) were evaluated for their anti-tobacco mosaic virus activity and in vitro cytotoxicity against A549 and HL60 cell lines; only compound 2 showed weak activity.     

比色法快速测定乳酸菌谷氨酸脱羧酶活力及其应用

基于Berthelot显色测定ω-氨基酸的反应 ,探讨了比色法快速测定谷氨酸脱羧酶活力的测定条件。结果表明 ,该方法灵敏度较高 ,重现性好 ,成本低 ,快捷 ,可替代氨基酸分析仪分析法。对乳酸菌谷氨酸脱羧酶提取液的适宜反应底物体系为 0.2mol LMacIlvaine ,pH4.7,内含 0.1mmol LPLP (5 磷酸吡哆醛 ) ,10mmol L底物L MSG (L 谷氨酸钠 )。 2 0 0 μL底物溶液和 1～ 1 0 0 μL酶液在 3 0℃反应 ,然后冰浴中加入 2 0 0 μ/L 0.     

Structural investigation of a fucoidan containing a fucose-free core from the brown seaweed, Hizikia fusiforme

A fucoidan, obtained from the hot-water extract of the brown seaweed, Hizikia fusiforme, was separated into five fractions by DEAE Sepharose CL-6B and Sepharose CL-6B column chromatography. All five fractions contained predominantly fucose, mannose and galactose and also contained sulfate groups and uronic acid. The fucoidans had MWs from 25 to 950 kDa. The structure of fraction F32 was investigated by desulfation, carboxyl-group reduction, partial hydrolysis, methylation analysis and NMR spectroscopy. The results showed that the sugar composition of F32 was mainly fucose, galactose, mannose, xylose and glucuronic acid; sulfate was 21.8%, and the MW was 92.7 kDa. The core of F32 was mainly composed of alternating units of -->2)-alpha-D-Man(1--> and -->4)-beta-D-GlcA(1-->, with a minor portion of -->4)-beta-D-Gal(1--> units. The branch points were at C-3 of -->2)-Man-(1-->, C-2 of -->4)-Gal-(1--> and C-2 of -->6)-Gal-(1-->. About two-thirds of the fucose units were at the nonreducing ends, and the remainder were (1-->4)-, (1-->3)- and (1-->2)-linked. About two-thirds of xylose units were at the nonreducing ends, and the remainder were (1-->4)-linked. Most of the mannose units were (1-->2)-linked, and two-thirds of them had a branch at C-3. Galactose was mainly (1-->6)-linked. The absolute configurations of the sugar residues were alpha-D-Manp, alpha-L-Fucp, alpha-D-Xylp, beta-D-Galp and beta-D-GlcpA. Sulfate groups in F32 were at C-6 of -->2,3)-Man-(1-->, C-4 and C-6 of -->2)-Man-(1-->, C-3 of -->6)-Gal-(1-->, C-2, C-3 or C-4 of fucose, while some fucose had two sulfate groups. There were no sulfate groups in either the GlcA or xylose residues.     

Retinoic acid represses CYP7A1 expression in human hepatocytes and HepG2 cells by FXR/RXR-dependent and independent mechanisms

Cholesterol 7α-hydroxylase (CYP7A1) plays a key role in maintaining lipid and bile salt homeostasis as it is the rate-limiting enzyme converting cholesterol to bile acids. Deficiency of CYP7A1 leads to hyperlipidemia in man and mouse. Hyperlipidemia is often seen in patients when treated with high-dose retinoic acid (RA), but the molecular mechanisms remain elusive. Our present study revealed that CYP7A1 mRNA expression is greatly repressed by RA in both human hepatocytes and HepG2 cells where increased fibroblast growth factor 19 (FGF19) and small heterodimer partner (SHP) expressions were also observed, suggesting farnesoid X receptor (FXR) and retinoid X receptor (RXR) were activated. Promoter reporter assays demonstrate that all-trans RA (atRA) specifically activated FXR/RXR. However, detailed molecular analyses indicate that this activation is through RXR, whose ligand is 9-cis RA. Knocking down of FXR or RXRα by small interference RNA (siRNA) in human hepatocytes increased CYP7A1 basal expression, but the repressive effect of atRA persisted, suggesting there are also FXR/RXR-independent mechanisms mediating atRA repression of CYP7A1 expression. Chromatin immunoprecipitation (ChIP) assay and cell transfection results indicate that PGC-1α plays a role in the FXR/RXR-independent mechanism. Our findings may provide a potential explanation for hyperlipidemic side effects observed in some patients treated with high-dose RA.     

Novel 2, 8-bit derivatives of quinolines attenuate Pseudomonas aeruginosa virulence and biofilm formation

Signal molecules are stimulators of multiple quroum-sensing virulence and biofilm formation. Small molecule analogues have been suspected as a potent inhibitor in therapeutic strategy. Herein, we synthesized a series of small molecule compounds from the 2, 8-bit derivatives of quinoline by Suzuki coupling reaction. We found that these compounds have the biofilm inhibitory effect in normal condition instead of phosphate limitation state. Furthermore, lacZ reporter strain assay and rhamnolipids as well as pyocyanin experiments showed that these compounds did not affect las and pqs system but reduced the expression of rhl. All these results suggest that quinoline derivatives can be treated as potent inhibitors against biofilm and reduce virulence through the rhl system. This research will be useful in designing new quorum sensing inhibitors to attenuate the infection of bacteria.