佛手挥发油特征化学成分群GC-MS研究

目的:分析6个不同产地佛手挥发油的化学成分,确定其特征化学指标成分群.方法:采用水蒸气蒸馏法提取佛手挥发油.运用气相色谱质谱联用技术(GC-MS),结合计算机检索对其化学成分进行分离和鉴定,得到其共有的特征性化学成分群,用色谱峰面积归一化法计算各组分的相对含量.结果:从广东、四川、金华、广西、安徽佛手的挥发油中鉴定16种共有特征成分,按保留时间的先后顺序分别为:α-水芹烯、α-蒎烯、β-蒎烯、β-月桂烯、α-萜品油烯、邻伞花烃、柠檬烯、顺式-β-罗勒烯、反式-β-罗勒烯、γ-萜品烯、γ-萜品油烯、乙酸芳樟酯、顺式-水合桧烯、α-萜品醇、β-柠檬醛、α-柠檬醛,其占总峰面积的的比例大于82.9%;其中柠檬烯和γ-萜品烯是主要成分,两者峰面积占总峰面积的比例大于65%.结论:所建立的特征成分群能充分地袁征佛手挥发油化学组成,可以为佛手挥发油的质量评价提供参考.     

Equipment management risk rating system based on engineering endpoints

The equipment management risk ratings system outlined here offers two significant departures from current practice: risk classifications are based on intrinsic device risks, and the risk rating system is based on engineering endpoints. Intrinsic device risks are categorized as physical, clinical and technical, and these flow from the incoming equipment assessment process. Engineering risk management is based on verification of engineering endpoints such as clinical measurements or energy delivery. This practice eliminates the ambiguity associated with ranking risk in terms of physiologic and higher-level outcome endpoints such as no significant hazards, low significance, injury, or mortality.     

The vesicular integral protein-like gene is essential for development of a mechanosensory system in zebrafish

The zebrafish hi472 mutation is caused by a retroviral insertion into the vesicular integral protein-like gene, or zVIPL, a poorly studied lectin implicated in endoplasmic reticulum (ER)-Golgi trafficking. A mutation in the shorter isoform of zVIPL (zVIPL-s) results in a reduction of mechanosensitivity and consequent loss of escape behavior. Here we show that motoneurons and hindbrain reticulospinal neurons, which normally integrate mechanosensory inputs, failed to fire in response to tactile stimuli in hi472 larvae, suggesting a perturbation in sensory function. The hi472 mutant larvae in fact suffered from a severe loss of functional neuromasts of the lateral line mechanosensory system, a reduction of zVIPL labeling in support cells, and a reduction or even a complete loss of hair cells in neuromasts. The Delta-Notch signaling pathway is implicated in cellular differentiation of neuromasts, and we observed an increase in Notch expression in neuromasts of hi472 mutant larvae. Treatment of hi472 mutant larvae with DAPT, an inhibitor of Notch signaling, or overexpression of the Notch ligand deltaB in hi472 mutant blastocysts produced partial rescue of the morphological defects and of the startle response behavior. We conclude that zVIPL-s is a necessary component of Delta-Notch signaling during neuromast development in the lateral line mechanosensory system.     

Plastids contain a second sec translocase system with essential functions

Proteins that are synthesized on cytoplasmic ribosomes but function within plastids must be imported and then targeted to one of six plastid locations. Although multiple systems that target proteins to the thylakoid membranes or thylakoid lumen have been identified, a system that can direct the integration of inner envelope membrane proteins from the stroma has not been previously described. Genetics and localization studies were used to show that plastids contain two different Sec systems with distinct functions. Loss-of-function mutations in components of the previously described thylakoid-localized Sec system, designated as SCY1 (At2g18710), SECA1 (At4g01800), and SECE1 (At4g14870) in Arabidopsis (Arabidopsis thaliana), result in albino seedlings and sucrose-dependent heterotrophic growth. Loss-of-function mutations in components of the second Sec system, designated as SCY2 (At2g31530) and SECA2 (At1g21650) in Arabidopsis, result in arrest at the globular stage and embryo lethality. Promoter-swap experiments provided evidence that SCY1 and SCY2 are functionally nonredundant and perform different roles in the cell. Finally, chloroplast import and fractionation assays and immunogold localization of SCY2-green fluorescent protein fusion proteins in root tissues indicated that SCY2 is part of an envelope-localized Sec system. Our data suggest that SCY2 and SECA2 function in Sec-mediated integration and translocation processes at the inner envelope membrane.     

The thrombomodulin-protein C system is essential for the maintenance of pregnancy

Disruption of the mouse gene encoding the blood coagulation inhibitor thrombomodulin (Thbd) leads to embryonic lethality caused by an unknown defect in the placenta. We show that the abortion of thrombomodulin-deficient embryos is caused by tissue factor-initiated activation of the blood coagulation cascade at the feto-maternal interface. Activated coagulation factors induce cell death and growth inhibition of placental trophoblast cells by two distinct mechanisms. The death of giant trophoblast cells is caused by conversion of the thrombin substrate fibrinogen to fibrin and subsequent formation of fibrin degradation products. In contrast, the growth arrest of trophoblast cells is not mediated by fibrin, but is a likely result of engagement of protease-activated receptors (PAR)-2 and PAR-4 by coagulation factors. These findings show a new function for the thrombomodulin-protein C system in controlling the growth and survival of trophoblast cells in the placenta. This function is essential for the maintenance of pregnancy.     

The formation and characteristics of China's existing system

Conclusion To sum up, the character of China's existing system is basically all-embracing totalitarianism formed by the combination of the old tradition of feudal-despotism and the new tradition of Stalinism. This system is the basic source of all the social evils in China.The ultimate aim of the democratic movement is to transform the old, allembracing totalitarian system and to establish a democratic, free, humane, and rational new system. The present ruling group is the beneficiary and defender of the existing system. The contradictions and conflicts between reformers who want to transform the old system and the hardliners who want to protect the old system formed the crux of the struggle of the 1989 democratic movement. Because the democratic movement lacked preparation in theory, organization, tactics and strategy, and because the ruling group controls the means of dictatorship — especially the army —military force was used to suppress the democratic movement with brutal bloodshed. In order to promote the democratic movement, we should sum up some lessons and experiences. First, we should study in depth the existing system and oppose feudaldespotism and Stalinism through effective propaganda and education. Second, we should arouse the democratic consciousness of the broad masses of the people, uniting with them and the healthy elements inside the Party, government, and army to struggle for the smashing of the old system and the establishment of a new system.Su Shaozhi is former Director of the Institute for the Study of Marxism-Leninism and Mao Zedong Thought, Chinese Academy of Social Sciences, Beijing, and currently Visiting Professor at the Bradley Institute for Democracy and Public Values, Marquette University, Milwaukee, Wisconsin     

The Rcs phosphorelay system is essential for pathogenicity in Erwinia amylovora

The Rcs phosphorelay system is a modified two-component signal transduction system found exclusively in Enterobacteriaceae . In this study, we characterized the roles of the Rcs system in Erwinia amylovora , a highly virulent and necrogenic enterobacterium causing fire blight disease on rosaceous plants. Our results showed that rcsB , rcsC , rcsD and rcsBD mutants were non-pathogenic on immature pear fruit. The bacterial growth of these mutants was also greatly reduced compared with that of the wild-type strain in immature pear fruit. In an in vitro amylovoran assay, rcsB and rcsD mutants were deficient in amylovoran production, whereas the rcsC mutant exhibited higher amylovoran production than that of the wild-type. Consistent with amylovoran production, expression of the amylovoran biosynthetic gene amsG , using green fluorescent protein as a reporter, was not detectable in rcsB , rcsD and rcsBD mutants both in vitro and in vivo . The expression of amsG in vitro was higher in the rcsC mutant than in the wild-type, whereas its expression in vivo was higher in the wild-type than in the rcsC mutant. In addition, rcs mutants were more susceptible to polymyxin B treatment than the wild-type, suggesting that the Rcs system conferred some level of resistance to polymyxin B. Furthermore, rcs mutants showed irregular and slightly reduced motility on swarming plates. Together, these results indicate that the Rcs system plays a major role in virulence and survival of E. amylovora in immature pear fruit.     

The HrpB-HrpA two-partner secretion system is essential for intracellular survival of Neisseria meningitidis

In this study we used HeLa cells to investigate the role of the HrpB-HrpA two-partner secretion (TPS) system in the meningococcal infection cycle. Although there is evidence that several pathogenic microorganisms may use TPS systems to colonize epithelial surfaces, the meningococcal HrpB-HrpA TPS system was not primarily involved in adhesion to or invasion of HeLa cells. Instead, this system was essential for intracellular survival and escape from infected cells. Gentamicin protection assays, immunofluorescence and transmission electron microscopy analyses demonstrated that, in contrast to the wild-type strain, HrpB-HrpA-deficient mutants were primarily confined to late endocytic vacuoles and trapped in HeLa cells. Haemolytic tests using human erythrocytes suggested that the secreted HrpA proteins could act as manganese-dependent lysins directly involved in mediating vacuole escape. In addition, we demonstrated that escape of wild-type meningococci from infected cells required the use of an intact tubulin cytoskeleton and that the hrpB-hrpA genes, which are absent in other Neisseria spp., were upregulated during infection.     

The twin-arginine translocation (Tat) system is essential for Rhizobium-legume symbiosis

The Tat (twin-arginine translocation) system mediates export of periplasmic proteins in folded conformation. Proteins transported via Tat contain a characteristic twin-arginine motif in their signal peptide. Genetic determinants (tatABC genes) of the Tat system from Rhizobium leguminosarum bv. viciae were cloned and characterized, and a tatBC deletion mutant was constructed. The mutant lacked the ability for membrane targeting of hydrogenase, a known Tat substrate, and was impaired in hydrogenase activity. Interestingly, in the absence of a functional Tat system, only small, white nodules unable to fix nitrogen were induced in symbiosis with pea plants. Analysis of nodule structure and location of green fluorescent protein (GFP)-tagged bacteria within nodules indicated that the symbiotic process was blocked in the tat mutant at a stage previous to bacteria release into cortical cells. The R. leguminosarum Tat-deficient mutant lacked a functional cytochrome bc1 complex. This was consistent with the fact that R. leguminosarum Rieske protein, a key component of the symbiosis-essential cytochrome bc1 complex, contained a typical twin-arginine signal peptide. However, comparative analyses of nodule structure indicated that nodule development in the tat mutant was arrested at an earlier step than in a cytochrome bc1 mutant. These data indicate that the Tat pathway is also critical for proteins relevant to the initial stages of the symbiotic process.     

The essential YycFG two-component system controls cell wall metabolism in Bacillus subtilis

Adaptation of bacteria to the prevailing environmental and nutritional conditions is often mediated by two-component signal transduction systems (TCS). The Bacillus subtilis YycFG TCS has attracted special attention as it is essential for viability and its regulon is poorly defined. Here we show that YycFG is a regulator of cell wall metabolism. We have identified five new members of the YycFG regulon: YycF activates expression of yvcE, lytE and ydjM and represses expression of yoeB and yjeA. YvcE(CwlO) and LytE encode endopeptidase-type autolysins that participate in peptidoglycan synthesis and turnover respectively. We show that a yvcE lytE double mutant strain is not viable and that cells lacking LytE and depleted for YvcE exhibit defects in lateral cell wall synthesis and cell elongation. YjeA encodes a peptidoglycan deacetylase that modifies peptidoglycan thereby altering its susceptibility to lysozyme digestion and YdjM is also predicted to have a role in cell wall metabolism. A genetic analysis shows that YycFG essentiality is polygenic in nature, being a manifestation of disrupted cell wall metabolism caused by aberrant expression of a number of YycFG regulon genes.     

Antimicrobial activity of Pelargonium essential oils added to a quiche filling as a model food system

Eight essential oils obtained by steam distillation from the scented leaves of Pelargonium species and cultivars were added at 250, 500 and 1000 ppm to a quiche filling, inoculated with either Saccharomyces ludwigii or Zygosaccharomyces bailii (at 10⁸ cfu g⁻¹), Salmonella enteriditis or Listeria innocua (at 10⁹ cfu g⁻¹). The quiche fillings were then kept at 25 °C for 24 h and the residual number of micro-organisms determined using the pour plate technique. There was an effective antimicrobial activity by the Pelargonium essential oils at 250 ppm, comparable with that of commercial thyme oil, an excellent antimicrobial agent, against Saccharomyces ludwigii and Zygosaccharomyces bailii , and a lesser inhibition compared with commercial thyme against Salm. enteriditis. There was a greater diversity of activity against L. innocua, which was in some cases more effective than commercial thyme oil. At 500 ppm, there was a greatly increased inhibition of microbial growth using the Pelargonium essential oils, which was comparable with that of commercial thyme, clove, geranium and coriander oils. As there is no evidence for the toxicity of any of these novel Pelargonium oils, and their odour does not make the delicately flavoured quiche filling unpalatable, there is a strong potential for their use in food processing.     

The essential cell division protein FtsN contains a critical disulfide bond in a non‐essential domain

Disulfide bonds are found in many proteins associated with the cell wall of Escherichia coli, and for some of these proteins the disulfide bond is critical to their stability and function. One protein found to contain a disulfide bond is the essential cell division protein FtsN, but the importance of this bond to the protein's structural integrity is unclear. While it evidently plays a role in the proper folding of the SPOR domain of FtsN, this domain is non‐essential, suggesting that the disulfide bond might also be dispensable. However, we find that FtsN mutants lacking cysteines give rise to filamentous growth. Furthermore, FtsN protein levels in strains expressing these mutants were significantly lower than in a strain expressing the wild‐type allele, as were FtsN levels in strains incapable of making disulfide bonds (dsb^‐) exposed to anaerobic conditions. These results strongly suggest that FtsN lacking a disulfide bond is unstable, thereby making this disulfide critical for function. We have previously found that dsb^‐ strains fail to grow anaerobically, and the results presented here suggest that this growth defect may be due in part to misfolded FtsN. Thus, proper cell division in E. coli is dependent upon disulfide bond formation.     

PG27 is a novel membrane protein essential for a Porphyromonas gingivalis protease secretion system

Porphyromonas gingivalis secretes endopeptidase gingipains, which are important virulence factors of this bacterium. Gingipains are transported across the inner membrane via the Sec system, followed by transport across the outer membrane via an unidentified pathway. The latter transport step is suggested to be mediated via a novel protein secretion pathway. In the present study, we report a novel candidate as an essential factor for the latter transport step. The PG0027 gene of P. gingivalis W83 encodes novel protein PG27. In a PG0027 deletion mutant (83K10), the activities of Arg-gingipain and Lys-gingipain were severely reduced, while the activities of secreted exopeptidases DPPIV, DPP-7, and PTP-A were unaffected. Protein localization was investigated by cell-surface biotinylation, subcellular fractionation, and immunoblot analysis. In the wild-type W83, Arg-gingipains in membrane fraction were detected as cell surface proteins. In contrast, in 83K10, Arg-gingipains were trapped in the periplasm and hardly secreted into an extracellular milieu. PG27 was suggested to be exposed to the cell surface by a cell surface biotinylation experiment; however, PG27 was detected in both inner and outer membrane fractions by subcellular fractionation experiments. Taken together, we suggest that PG27 is a unique membrane protein essential for a novel secretion pathway.     

Factors essential for desensitization of pigeon erythrocyte adenylate cyclase responsiveness in a cell-free system

Cell-free desensitization of the pigeon erythrocyte adenylate cyclase-coupled beta-adrenoreceptor system requires soluble cellular factors. Desensitization is observed when a mixture of cell membranes and the cytosol fraction are incubated with isoproterenol or cAMP and IBMX for 20 min at 37 degrees C. Mg2+ and ATP are also required for cell-free desensitization. When adenylate cyclase is maximally stimulated by isoproterenol or GTP-gamma-S, the decrement of activity is 45-50% and 20-25%, respectively. Adenylate cyclase desensitization may be also produced by preincubation of plasma membranes with the catalytic component of cAMP-dependent protein kinase. Cell-free desensitization is associated with functional uncoupling of the beta-receptor. This is evidenced by an impaired ability of receptors to form a high affinity, guanine nucleotide-sensitive complex with the agonist and by the increase of the lag-phase of adenylate cyclase activation by isoproterenol and GTP-gamma-S. These findings suggest that one possible mechanism for the development of desensitization in adenylate cyclase systems may be the phosphorylation of a component(s) of the beta-receptor-adenylate cyclase complex which results in impaired receptor-cyclase coupling.