Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

The inhibitory effects of nobiletin and hesperidin from citrus peel crude extracts on tyrosinase diphenolase activity are evaluated. IC50 of nobiletin and hesperidin is 1.49 mM and 16.08mM, respectively and their inhibition mechanism is competitive type with Ki = 2.82 mM and noncompetitive with Ki = 9.16 mM, respectively. Crude extracts from citrus peel (C. unshiu Marc.) were extracted with 95% ethanol and fractionated by petroleum ether (PCPE). The ethanol phase (ECPE) was further desorbed from macroporous adsorption resin (FGRE). Their IC50 values were 8.09 mg/mL, 7.53 mg/mL and 4.80 mg/mL, respectively. Their inhibition on melanogenesis in B16 mouse melanoma cells was also evaluated. FGRE showed a significant inhibition (42.5% at 31.25 microg/mL, p < 0.01) while hesperidin showed almost no inhibition. Nobiletin and PCPE give efficacious antiproliferation effects on B16 mouse melanoma cell with IC50 values 88.6 microM and 62.96 microg/mL, respectively, by the MTT test. Hesperidin and other crude extracts showed very low cytotoxity to the B16 cell.     

Resistance to experimental autoimmune encephalomyelitis and impaired IL-17 production in protein kinase C theta-deficient mice

The protein kinase C theta (PKC theta) serine/threonine kinase has been implicated in signaling of T cell activation, proliferation, and cytokine production. However, the in vivo consequences of ablation of PKC theta on T cell function in inflammatory autoimmune disease have not been thoroughly examined. In this study we used PKC theta-deficient mice to investigate the potential involvement of PKC theta in the development of experimental autoimmune encephalomyelitis, a prototypic T cell-mediated autoimmune disease model of the CNS. We found that PKC theta-/- mice immunized with the myelin oligodendrocyte glycoprotein (MOG) peptide MOG(35-55) were completely resistant to the development of clinical experimental autoimmune encephalomyelitis compared with wild-type control mice. Flow cytometric and histopathological analysis of the CNS revealed profound reduction of both T cell and macrophage infiltration and demyelination. Ex vivo MOG(35-55) stimulation of splenic T lymphocytes from immunized PKC theta-/- mice revealed significantly reduced production of the Th1 cytokine IFN-gamma as well as the T cell effector cytokine IL-17 despite comparable levels of IL-2 and IL-4 and similar cell proliferative responses. Furthermore, IL-17 expression was dramatically reduced in the CNS of PKC theta-/- mice compared with wild-type mice during the disease course. In addition, PKC theta-/- T cells failed to up-regulate LFA-1 expression in response to TCR activation, and LFA-1 expression was also significantly reduced in the spleens of MOG(35-55)-immunized PKC theta-/- mice as well as in in vitro-stimulated CD4+ T cells compared with wild-type mice. These results underscore the importance of PKC theta in the regulation of multiple T cell functions necessary for the development of autoimmune disease.     

Analysis of functions in plasmid pHZ1358 influencing its genetic and structural stability in <Emphasis Type="Italic">Streptomyces lividans</Emphasis> 1326

The complete DNA sequence of plasmid pHZ1358, a widely used vector for targeted gene disruption and replacement experiments in many Streptomyces hosts, has been determined. This has allowed a detailed analysis of the basis of its structural and segregational instability, compared to the high copy number plasmid pIJ101 of Streptomyces lividans 1326 from which it was derived. A 574-bp DNA region containing sti (strong incompatibility locus) was found to be a determinant for segregational instability in its original S. lividans 1326 host, while the structural instability was found to be related to the facile deletion of the entire Escherichia coli-derived part of pHZ1358, mediated by recombination between 36-bp direct repeats. A point mutation removing the BamHI site inside the rep gene encoding a replication protein (rep*) and/or a spontaneous deletion of the 694-bp region located between rep and sti including the uncharacterized ORF85 (orf85 ⁻) produced little or no effect on stability. A pHZ1358 derivative (pJTU412, sti ⁻ , rep*, orf85 ⁻) was then constructed which additionally lacked one of the 36-bp direct repeats. pJTU412 was demonstrated to be structurally stable but segregationally unstable and, in contrast to sti ⁺ pHZ1358, allowed efficient targeted gene replacement in S. lividans 1326.     

A HPLC-UV method for the determination of puerarin in rat plasma after intravenous administration of PEGylated puerarin conjugate

A sensitive and reproducible HPLC method for quantitative determination of puerarin (PUE) in rat plasma was developed and validated using 4-hydroxybenzaldehyde as an internal standard. The separation of PUE was performed on a CAPCELL PAK C18 column by gradient elution with 0.2% aqueous phosphoric acid and acetonitrile as the mobile phase. The method was validated and found to be linear in the range of 80-12,000ng/mL. The limit of quantification was 80ng/mL based on 100μL of plasma. The variations for intra- and inter-day precision were less than 8.3%, and the accuracy values were between 98% and 105.2%. The extraction recoveries were more than 85%. The method was successfully applied in the comparative study of pharmacokinetics of PEGylated puerarin (PEG-PUE) versus PUE in rats. Compared with PUE, PEG-PUE showed a 5.2-fold increase in half-life of PUE and a 4.7-fold increase in mean residence time. In addition, this method was also successfully applied to determine the low plasma concentration of PUE regenerated from PEG-PUE in vitro.     

Early Silurian(Telychian)rugose coral fauna of Daguan area, northeast Yunnan Province,China

Study on rugose coral fauna of the Sifengya Formation(early Telyehian)and Daluzhai Formation (mid-late Telychian)in Daguan area,northeast Yunnan Province,China was carded out.Rugose coral fauna of the Sifengya Formation included 18 genera and 34 species,while Daluzhai Formation with nine genera,ten species.We described rugose coral fauna(12 genera,19 species)including one new genus and five new species,i.e.Protoketophyllum daguanense gen.et sp.nov..Crassilasma huanggexiense sp.nov.,Pseudophaulactis heae sp.nov.,P.convolutus sp.nov.,and Shensiphyllum minor sp.nov..The characteristics and geological significance of rugose coral fauna of Sifengya Formation and Daluzhai Formation were analyzed.Particularly,mgose coral fauna of the Sifengya Formation represent early Telychian rugosan fauna in the Upper Yangtze region and improve the sequences of early Silurian(Llandovery)mgose coral assemblages in Yangtze region.It is therefore very meaningful to further analyze radiation period of rugose coral fauna in such epoch.     

Streptomyces coelicolor A3(2) Lacks a Genomic Island Present in the Chromosome of Streptomyces lividans 66

Streptomyces lividans ZX1 has become a preferred host for DNA cloning in Streptomyces species over its progenitor, the wild-type strain 66 (stock number 1326 from the John Innes Center collection), especially when stable DNA is crucial for in vitro electrophoresis, because DNA from strain 66 contains a novel modification that makes it sensitive to oxidative double-strand cleavage during electrophoresis. Detailed analysis of this modification-deficient mutant (ZX1) revealed that it has several additional phenotypic traits associated with a chromosomal deletion of ca. 90 kb, which was cloned and mapped by using a cosmid library. Comparative sequence analysis of two clones containing the left and right deletion ends originating from strain 66 and one clone with the deletion and fused sequence cloned from strain ZX1 revealed a perfect 15-bp direct repeat, which may have mediated deletion and fusion to yield strain ZX1 by site-specific recombination. Analysis of AseI linking clones in the deleted region in relation to the published AseI map of strain ZX1 yielded a complete AseI map for the S. lividans 66 genome, on which the relative positions of a cloned phage HAU3 resistance (HAU3^r) gene and the dnd gene cluster were precisely localized. Comparison of S. lividans ZX1 and its progenitor 66, as well as the sequenced genome of its close relative, Streptomyces coelicolor M145, reveals that the ca. 90-kb deletion in strain ZX1 may have originated from an insertion from an unknown source.     

2020—2050年CO2施肥效应促进全球陆地生态系统碳吸收

CO₂施肥效应是全球变绿的主要原因,随着大气中CO₂浓度的持续增加,预估未来气候变化条件下,CO₂施肥效应对陆地生态系统的影响对减缓全球气候变化具有重大意义。基于未来气候情景数据和Farquhar模型,并结合生态过程模型BEPS(Boreal Ecosystem Productivity Simulator),定量化研究2020—2050年CO₂施肥效应对全球叶面积指数(LAI)和总初级生产力(GPP)的影响。研究结果显示2020—2050年,在RCP2.6、RCP4.5和RCP8.5气候情景下,CO₂施肥效应导致的LAI年际变化趋势分别为0.002、0.003和0.005 m^-2m^-2a^-1;三个气候情景下CO₂施肥效应对LAI的影响为CO₂每增加0.1%,LAI平均增加约8.1%—9.2%,由此导致GPP对应增加7.9%—14.6%;由CO₂施...     

优于单一最大熵生态位模型的混合烟粉虱生境风险评估模型

预测入侵生物的潜在地理分布、快速评估其高脆弱性区域是实现入侵生物前瞻性风险预警的重要手段。MaxEnt生态位模型是目前应用最广泛的生境风险评估方法,操作简单,预测精度较高,但模型对数据的质量和数量过分依赖。以烟粉虱Bemisia tabaci为对象,引入地理探测器显式描述评价因子的空间关联规律和贡献度,结合MaxEnt生态位模型,提出一种混合生境风险评估模型(Geo-MaxEnt),并与单一MaxEnt生态位模型进行对比。结果表明：(1)地理探测器模型显示,海拔(0.56)、土地利用(0.43)、最热月最高温度(0.36)和年平均温度(0.30),对烟粉虱的空间分布具有显著影响,各因子对烟粉虱生境的影响存在显著的差异。海拔和土地利用PD值最高,是影响烟粉虱生境的主要驱动因子。环境因子的交互作用强化了各个因子的影响力。(2)单一MaxEnt生态位和所构建的模型总体精度分别是94.86%(AUC 0.91)和98.13%(AUC 0.94),相较之下,所构建的模型精度略高,表明所构建的模型是合理的,具有高度的可靠性;(3)对于高风险区,混合模型优于MaxEnt模型,但两者在空间分布方面高度...     

药用植物裂环烯醚萜苷类化合物生物合成途径关键酶基因研究进展

裂环烯醚萜苷类化合物是植物体内产生的具有保肝、消炎、降血糖血脂等多重生物活性的次级代谢产物,在临床上应用广泛。该文依据近年来国内外有关裂环烯醚萜苷类化合物生物合成途径及关键酶基因的挖掘与调控机理研究进展,主要对药用植物裂环烯醚萜苷类化合物生物合成途径、关键酶(GPPS、GES、G10H、8HGO、IS、IO、7DLGT、DL7H、LAMT、SLS)与编码基因的研究进展进行综述,为进一步阐明其生物合成途径机制与关键酶调控作用、提高有效活性成分积累、减缓药用植物野生资源紧张等问题提供参考。