球毛壳菌H6次级代谢产物及其α-葡萄糖苷酶抑制活性

采用体外α-葡萄糖苷酶抑制模型对一株球毛壳菌H6的发酵液和菌丝体两种乙酸乙酯提取物进行活性评价,结果表明,发酵液乙酸乙酯提取物对α-葡萄糖苷酶具有较强的抑制活性,其IC₅₀值为(510.76±23.46)μg/mL。采用硅胶、Sephadex LH-20、半制备高效液相等色谱技术从其发酵液乙酸乙酯提取物中分离得到12个化合物。通过各种光谱分析,依次鉴定为chaetoviridins A-B(1-2),chaetoglobosins A-D(3-6),chaetoglobosin J(7),chaetoglobosin Q(8),prochaetogobosinsⅠ-Ⅲ(9-11),vibratilicin(12),其中化合物12为首次从毛壳属中分离得到。对化合物进行α-葡萄糖苷酶抑制活性测定发现,化合物12显示弱的抑制活性,其IC₅₀为(1 182.75±19.14)μg/mL。     

Measurement of cervical multifidus contraction pattern with ultrasound imaging

Deep muscle training has become the focus of research and exercise for patients with chronic neck pain. The objective of this in vivo study was to establish a non-invasive assessment tool for the activation of deep cervical muscles. The pattern of the change in the thickness of the cervical multifidus is described with a mathematical equation and used to compare the changes among different levels of resistance (0%, 25%, 50%, 75%, and 100%) and at different cervical levels (fourth, fifth, and sixth cervical (C4, C5, and C6) vertebrae). Twenty asymptomatic subjects (five women and 15 men; 24.3 ± 4.7 years old) were recruited for this experiment. Ultrasonography (US) with synchronized force recording was used to measure the thickness of the cervical multifidus during progressive isometric extension against resistance. Linear and quadratic models were used to estimate the patterns of change in the thickness of cervical multifidus in relation to force. Two-way analysis of variance with repeated measurement and post hoc analysis were used to investigate the differences in thickness. The change in thickness and force was better fitted by quadratic model (y = ax² + bx + c) than by the linear model. The thickness at 50% of maximum contraction was significantly increased compared with that at 25% of maximum contraction. This quantitative non-invasive measurement may provide an assessment tool for further investigation for the physiological function of the deep muscles. Further research is required to investigate whether the change of thickness was predominately determined by the recruitment of muscle fibers or the extensibility of non-contractile tissues.     

基于多时相SAR数据和SPOT数据的盘古林场林分类型识别

林分类型信息的提取是遥感影像分类中的热点和难点。而大兴安岭地区又是我国重点林区和天然林主要分布区之一,植被类型丰富,种类繁多,为林分类型精确识别带来了很大的难度。为了比较和提高林分类型的分类精度,研究以大兴安岭地区盘古林场为实验区,综合利用SPOT-5影像和不同时相的RADARSAT-2全极化SAR影像,采用3种分类方案及最大似然分类方法对研究区遥感影像进行分类,并比较不同分类方案对林分类型识别的精度。3种方案分别是:(1)单独采用SPOT影像对林分类型进行识别;(2)对全极化SAR数据进行极化分解提取参数并结合SPOT数据参与分类;(3)结合SPOT数据与多时相全极化SAR分解参数进行分类。结果表明:对比SPOT、加入单时相和加入多时相3种方案的分类结果,方案三加入多时相SAR影像与SPOT数据对白桦林、落叶松林、樟子松林和云杉林的分类中总分类精度最高,为84.64%,Kappa系数为0.79,对林分类型的识别最为有效,而单用SPOT数据对林分类型识别的精度最低,精度为76.66%,Kappa系数为0.70。     

Evidence of geographical structuring in the Malaysian Snakehead, Channa striata based on partial segment of the CO1 gene

Channa striata, locally known as "haruan", is economically important in fisheries and aquaculture industries in several Asian countries. DNA sequencing, based on a partial segment of the Cytochrome oxidase c subunit 1 (CO1) gene, was used to determine genetic variation in C. striata samples from four different populations on the west coast of Peninsular Malaysia. The highest nucleotide and haplotype diversities were observed in the Linggi population (π = 0.0067, h = 0.835), and the lowest in the Timah Tasoh population (π = 0.0008, h = 0.286). Apart from Kajang-Linggi, which was insignificant, F(ST) values were significant (p < 0.05) in all pairwise-population comparisons. Consequently, it is inferred that genetic structuring C. striata populations in this region was largely shaped by a common origin, with secondary influences from geographical factors and isolation.     

Co-regulation of root hair tip growth by ROP GTPases and nitrogen source modulated pH fluctuations

Growth of plant cells involves tight regulation of the cytoskeleton and vesicle trafficking by processes including the action of the ROP small G proteins together with pH-modulated cell wall modifications. Yet, little is known on how these systems are coordinated. In a paper recently published in Plant Cell and Environment¹ we show that ROPs/RACs function synergistically with NH₄NO₃-modulated pH fluctuations to regulate root hair growth. Root hairs expand exclusively at their apical end in a strictly polarized manner by a process known as tip growth. The highly polarized secretion at the apex is maintained by a complex network of factors including the spatial organization of the actin cytoskeleton, tip-focused ion gradients and by small G proteins. Expression of constitutively active ROP mutants disrupts polar growth, inducing the formation of swollen root hairs. Root hairs are also known to elongate in an oscillating manner, which is correlated with oscillatory H⁺ fluxes at the tip. Our analysis shows that root hair elongation in wild type plants and swelling in transgenic plants expressing a constitutively active ROP11 (rop11^CA) is sensitive to the presence of NH₄⁺ at concentrations higher than 1 mM and on NO₃⁻. The NH₄⁺ and NO₃⁻ ions did not affect the localization of ROP in the membrane but modulated pH fluctuations at the root hair tip. Actin organization and reactive oxygen species distribution were abnormal in rop11^CA root hairs but were similar to wild-type root hairs when seedlings were grown on medium lacking NH₄⁺ and/or NO₃⁻. These observations suggest that the nitrogen source-modulated pH fluctuations may function synergistically with ROP regulated signaling during root hair tip growth. Interestingly, under certain growth conditions, expression of rop11^CA suppressed ammonium toxicity, similar to auxin resistant mutants. In this short review we discuss these findings and their implications.Key words: ROP, RAC, nitrogen, root hair, cell polarity, ammoniumIn Arabidopsis, root hairs grow out at the basal, rootward region (closer to root tip) of specialized root epidermal cells and expand exclusively at their apical end in a strictly polarized manner by a process known as tip growth. Tip growth is facilitated by Rho of Plants (ROP)-regulated processes such as maintenance of longitudinally-oriented actin cables in the shank of the root hair that are required for myosin-mediated organelle transport through the cytoplasm. ROPs also play a role in sustaining fine F-actin structures at the root hair tip, which promote the transport of secretory vesicles to sites of their fusion with the plasma membrane.^2,3 In addition, the polar growth of root hairs involves an oscillatory tip-focused Ca²⁺ gradient⁴ and tip-localized reactive oxygen species (ROS).⁵ Tip growth is also associated with oscillatory fluxes of H⁺ at the apex that correlate with the periodicity of growth.^6,7 These oscillations in extracellular pH and ROS have been shown to modulate tip growth and are predicted to act in a coordinated and complementary mode to regulate root hair elongation. Growth accelerates following reduction of apoplastic pH and slows upon apoplastic ROS increase and a coincident pH increase.⁷ROPs are small G proteins that localize to the plasma membrane at the apex of growing root hairs, where they activate a range of downstream pathways required for tip growth.^8,9 ROP activity is regulated by its cycling between a GTP-bound, active and GDP-bound, inactive state. Ectopic expression of constitutively active mutants of ROPs (dominant mutations in conserved residues that abolish the GTPase activity) depolarizes the growth of root hairs.^8–10 Downstream pathways activated by such ROP GTPases include the regulation of cytoskeletal dynamics and vesicular trafficking, production of ROS, maintenance of intracellular Ca²⁺ gradients and accumulation of signaling lipids, features all related to the regulation of apical growth.^11,12 For example, ectopic expression of constitutively active ROP11 (Atrop11^CA) depolarizes root hair growth, leading to the formation of swollen root hairs. This bulging root hair phenotype was associated with altered actin organization and inhibition of endocytosis.¹⁰It is well known that root hair development is highly plastic and regulated by environmental signals.^13,14 Yet, despite the known function of ROP GTPases and their regulatory proteins in root hair growth there is no data in the literature describing the relationship between ROP signaling and environmental factors in this process. Our results¹ show that induction of root hair swelling by rop11^CA occurs only under specific growth conditions, indicating that there is an interplay between ROP activity and the external environment, particularly nitrogen supply. We demonstrated that high external concentrations of ammonium are essential for the induction of depolarized root hair growth and activation of downstream pathways by rop11^CA. Depletion of ammonium did not affect the membrane localization and expression of GFP-rop11^CA, implying that NH₄⁺ was required in addition to ROP activity to cause root hair swelling. In agreement with this idea, normal actin organization and ROS localization were detected in rop11^CA root hairs when NH₄⁺ was depleted, suggesting that ammonium functions downstream of, or in parallel to ROP signaling (Fig. 1).Open in a separate windowFigure 1A model for regulation of root hair tip growth by ROP GTPases and pH oscillations dependent on nitrogen supply. GTP bound ROPs activate downstream effectors which directly affect actin organization, vesicular trafficking and localized ROS production as well as indirectly affecting the localization of membrane proteins involved in ion/proton fluxes. High concentrations of nitrogen ions in the growth medium increase pH oscillations at the apex of growing root hairs. In turn downstream ROP effectors sense the changes in pH and adjust their function accordingly. pH oscillations affect tip growth independent of ROPs via changes of wall pH and possibly through additional unknown factors. Dashed lines indicate that these effects were not confirmed experimentally.Plants can absorb and use various forms of nitrogen from soils, primarily the inorganic ions ammonium and nitrate. The concentrations of these ions are highly heterogeneous around the plant and can vary across several orders of magnitude among different soils and as a result of seasonal changes.¹⁵ Thus, plants would be expected to display highly plastic, N-regulated developmental responses and to employ a range of nitrogen uptake transport systems to optimize exploitation of local N resources. Transport systems that mediate NH₄ fluxes across the plasma membrane of root cells are divided into two categories: high affinity transport systems (HATS) that mediate uptake from relatively dilute solutions at relatively low rates and low affinity transport systems (LATS) that operate at high rates and higher external concentrations.¹⁶ The HATS are plasma membrane localized NH₄⁺-specific transporters (AMTs) that are most likely proton-coupled and their expression and function are repressed at external ammonium concentrations of 1 mM or higher.^17–19 In contrast, ammonium uptake by LATS is believed to take place through non-specific cation channels.^17,20 The NH₄⁺ concentration in the 0.5× Murashige Skoog (MS) medium is 10.3 mM, exceeding by an order of magnitude the concentration at which the high affinity NH₄⁺ uptake system is repressed. The root hair swelling in Atrop11_CA plants and inhibition of root hair elongation in wild type plants occurred primarily at external ammonium concentrations greater than 1 mM, and thus is most likely associated with uptake by the LATS.As noted above, root hair elongation is associated with oscillations of cytoplasmic and apoplastic pH that have been linked to growth control. Simultaneous fluorescence ratio imaging of internal and external pH revealed that application of 10 mM NH₄NO₃ enhanced the amplitude of these pH oscillations at the extreme apex of wild type root hairs1 and Figure 2. These oscillations are thought to modulate tip growth through altering the extensibility of the wall.⁴ Additional measurements (Fig. 2) show that similar to the effects of NH₄NO₃, addition of NH₄Cl induced increase in the apoplastic pH fluctuations and reduced the pH. However, the effects of NH₄Cl on cytoplasmic pH fluctuations seem subtler compared to the effects of NH₄NO₃. Thus, one possible explanation for the observed swelling of the root hair apex in rop11_CA expressing plants in media containing NH₄NO₃ is that rop11_CA root hairs are affected in their ability to re-establish the normal proton gradient across the plasma membrane in response to ammonium transport. The altered proton gradient would then prevent the normal localized oscillatory changes in pH-dependent wall properties required to restrict expansion to the very tip of the elongating root hair.Open in a separate windowFigure 2Changes in apoplastic and cytoplasmic pH fluctuations, following application of NH₄NO₃, NH₄Cl or KNO₃. (A) Apolplastic pH (pH_ex) following treatments with either NH₄NO₃, NH₄Cl or KNO₃. Note the increase pH fluctuations induced by either NH₄NO₃ and NH₄Cl but not by KNO₃. (B) Cytoplasmic pH (pH_cyt) following treatments as above. Note the changes in pH fluctuations induced by NH₄NO₃ and the subtler effects of NH₄Cl.Concurrent absorption of NH₄⁺ and NO₃⁻- maintains the cation-anion balance within both the rooting medium and the root, and thus potentially has an important function in maintaining intracellular and extracellular pH.^21,22 In agreement, application of these ions affected the amplitude of pH oscillations¹ and Figure 2. Interestingly, treatments of WT seedlings with 10 mM NH₄NO₃ causes increase in root hair pH oscillations and often tip bursting. Yet, prolonged exposure of WT root hairs to NH₄NO₃ is accompanied by adaptation (our unpublished data). This adaptation does not occur in rop11_CA mutants, suggesting that cycling of ROPs between active and inactive states maybe important in adaptation to changing environment. These data strongly suggest that NH₄⁺-dependent root hair swelling in the plants expressing activated ROP resulted from physiological changes in ion balance rather than a direct effect of ammonium on enzymatic activities required for root hair growth (Fig. 1). Application of NH₄⁺ and NO₃⁻, in the absence of other ions, induced formation of additional growth tips, in which the membrane localized GFP-rop11^CA was concentrated. This observation suggests that interplay between the regulation of ROP localization and activity and the regulation of nitrogen fluxes may have an important function in the maintenance of unidirectional growth. As root hair elongation is coupled to spatially distinct regulation of extracellular pH oscillations and ROS production,⁷ it seems likely that there is a mechanism that can adjust the fluxes of nitrogen ions relative to these pH fluxes. This system would then maintain the oscillations in pH such that polarized growth is continued. One possible mechanism for this coordination is through the highly localized ROP cycling between active and inactive states that has an important role in the spatial activation of cell polarization machinery.^23–27 Due to the function of ROP GTPases in vesicle trafficking, actin organization and maintenance of ROS and Ca²⁺ gradients,^{2,8,9,23,24,28–33} expression of activated ROP11 may indirectly influence cell wall properties by altering the localization and/or recycling of cation and anion transporters/channels or plasma membrane H⁺-ATPases delivered to the growing tip of the hair and in this way affect the maintenance of the proton gradients. In agreement with a possible effect of activated ROPs on localization and/or recycling of membrane transporters we discovered that rop11^CA plants were resistant to ammonium toxicity when grown in the presence of NH₄NO₃ and several micronutrients.¹We propose a model (Fig. 1) in which spatial regulation of ROP activity creates a positive feedback loop with pH oscillations around the growing apex of root hairs. According to this model ROP cycling between active and inactive states spatially and temporally activates the downstream signaling cascades essential for the tip-growth of root hairs. At the same time, localization of membrane proteins involved in maintenance of normal nitrogen fluxes across the plasma membrane is indirectly affected by ROP signaling. Alternatively, ROP signaling is modulated to adapt to altered nitrogen fluxes. NH₄⁺ fluxes increase the amplitude of pH oscillations at the root hair apex and in turn affect cell-wall properties. Thus, when the ROP activity is upregulated by dominant mutations, the synergistic effects of pH changes and constant activation of ROP downstream effectors result in the uncontrolled cell expansion seen as root hair bulging. Previous studies have suggested that feedback between oscillatory pH change and ROS distribution is required to support tip growth.⁷ However, the factors that may integrate these processes are unknown. Our results suggest that spatial regulation of ROP activity in response to changing environments is one of the key elements that may coordinate the pH and ROS oscillations during the root hair tip growth.It will be interesting to examine whether ROP function is coordinated with apoplastic pH fluctuation in other cell types. Recently, it has been suggested that the effects of auxin on pavement cell structure in leaf epidermis require Auxin Binding Protein 1 (ABP1) dependent ROP activation.³⁴ It is well known that auxin induces changes in apoplastic pH. Possibly, like nitrogen source in root hairs, auxin dependent apolplastic pH fluctuations in the leaf epidermis may function coordinately with ROP in the regulation of cell growth. Consistent with this idea, it has been shown that auxin inhibits clathrin-dependent endocytosis through ABP1 reinforcing a possible role in modulating membrane flux/membrane properties.³⁵ Some auxin resistant mutants also display resistance to ammonium toxicity³⁶ further suggesting a link between auxin and membrane transport. Hence, auxin and ROPs may indeed function synergistically to modulate plasma membrane properties, in turn affecting ion balance in the apoplast and so modulating cell wall properties and growth.     

Decolorization of a dye industry effluent by <Emphasis Type="Italic">Aspergillus fumigatus</Emphasis> XC6

The strain Aspergillus fumigatus XC6 isolated from mildewing rice straw was evaluated for its ability to decolorize a dye industry effluent. The strain was capable of decolorizing dyes effluent over a pH range 3.0–8.0 with the dyes as sole carbon and nitrogen sources. The optimum pH was 3.0; however, supplemented with either appropriate nitrogen sources (0.2% NH₄Cl or (NH₄)₂SO₄ ) or carbon sources (1.0% sucrose or potato starch), the strain decolorized the effluent completely at the original pH of the dyes effluent. Therefore, A. fumigatus XC6 is an efficient strain for the decolorization of reactive textile dyes effluents, and it might be a practical alternative in dyeing wastewater treatment.     

胰岛素保护缺血/再灌注心脏:PI3-K/Akt和JNKs信号通路间的交互作用

我们前期研究表明胰岛素可激活细胞内信号转导机制如磷脂酰肌醇3．激酶．蛋白激酶B．内皮型一氧化氮合酶．一氧化氮（P13-K-Akt-eNOS-NO）信号通路,减轻心肌缺血／再灌注（ischemia／reperfusion,I／R）损伤,改善缺血后心肌功能恢复。然而c-Jun氨基末端激酶（c-JunNH2-terminal kinase,JNK）信号通路在胰岛素保护I／R心肌中的作用尚不清楚,本研究旨在探讨JNK信号通路在胰岛素保护I／R心肌中的作用及其与P13．K／Akt信号通路间的相互关系。离体Sprague-Dawley大鼠心脏缺血30min后施行2h或4h的再灌注,缺血前用LY294002（15mmol／L）和SP600125（10mmol／L）灌注15min,分别阻断P13．K／Akt和磷酸化JNK（phosphorylated．JNK,p-JNK）活化,观测心脏功能、心肌梗死、细胞凋亡和蛋白磷酸化水平。与对照组相比,胰岛素再灌注2h后,心率、左心室发展压和左心室收缩／舒张最大速率均明显增加,梗死面积减少约16．1％[（28．9±2．0）％vs（45．0±4．0）％,n=6,P〈O．01],细胞凋亡指数从（27．6±113）％减少到（16．0±0．7）％（n=6,P〈O．01）,Akt的活性增加1．7倍（n=6,P〈0．05）,同时JNK活性增加1．5倍铆=6,P〈O．05）。用LY294002处理后,胰岛素对I／R心肌的保护作用消失;而用SP600125处理可增强胰岛素的保护作用,且可部分逆转LY294002的抑制作用。进一步观察发现SP600125减弱了Akt的磷酸化m=6,P〈0．05）。上述结果表明,在I／R心肌中,胰岛素可同时激活P13．K／Akt及JNK信号通路,且通过后者进一步增加Akt活化,从而减轻I／R损伤,改善心肌功能。这种P13．K／Akt与JNK信号通路交互机制对胰岛素保护I／R心肌有重要意义。     

Phoxalone,a novel macrolide from <Emphasis Type="Italic">Sorangium cellulosum</Emphasis>: structure identification and its anti-tumor bioactivity in vitro

A novel macrolide, isolated from the myxobacteria Sorangium cellulosum WXNXJ-C, was identified as 1,7,12,13-tetrahydroxy-14-methoxy-8,10-dimethyl-6-phenyl-5,15-dioxa-bicyclo[9.3.1]pentadecan-4-one, “Phoxalone”. It had minimum IC₅₀ values of 0.24, 6.9, 10.3, 0.98 and 4 μg/ml, respectively, against tumour cell lines: B16, Bel7402, H446, MCF-7, and SGC7901. In addition, it had less cytotoxicity to normal human liver L02 cell lines (286 μg/ml, 24 h). A cytotoxic bioactivity study on H446 cell line in vitro suggested that Phoxalone arrested the mitosis in the G2/M phase.     

A criterion for proper cosolvents used for ionic liquids: The Lewis acidic and basic dual nature of propylene carbonate

Probe of the Lewis acidic property of propylene carbonate (PC) has been initiated by temperature-dependent ¹⁹F chemical shifts recorded for 1-butyl-3-methylimidazolium hexafluorophosphate/PC (BMIPF₆/PC) mixtures. Investigation of hyperconjugative interactions by natural bond orbital method reveals the trend of electron-accepting capabilities from anion, PC > dimethyl sulfoxide (DMSO) > N,N-dimethyl formamide (DMF) > acetonitrile (AN). Comparison of solvent-induced ionic association of BMIPF₆ in the four basic aprotic organic solvents, made by monitoring concentration- and temperature-dependent-ratios of solvent diffusion coefficients to BMI⁺-containing components, D_sol/D_BMI, shows that the extent of original ionic association can be reduced by solvent dilution in the same decreasing order, PC ∼ DMSO > DMF > AN. In DMF and AN, two basic solvents having similar dielectric constants, the greater Lewis acid of DMF accounts for its better ability to dissociate aggregates of BMIPF₆. By replacing ethanol with 2,2,2-trifluoroethanol (TFE), the poor miscibility of BMIPF₆ with ethanol can be greatly enhanced due to the CF₃ group, capable of adapting electron density from anions via hyperconjugative interactions. In BMIPF₆/TFE mixtures, values of measured on ¹⁹F resonances show larger aggregates than measured on ¹H resonances, indicating charged clusters prefer anionic to cationic states. This observation can be explained by varying ionic states concerning with unbalanced charged aggregates between positive and negative ones.