論《長生殿》

《長生殿》[1] 是劇作家洪昇 (1645 - 1703) 的作品。洪昇字昉思，出身於士大夫家庭，出生在明朝滅亡後的第二年，此乃兵荒馬亂的時期。而洪昇的成長階段，都是充滿漢族反抗清朝的鬥爭，長大後，他面對外族統治的政權，這個漢、滿民族矛盾尖銳的清代， 就深深影響著洪昇對《長生殿》的創作。正如雅斯培 (Karl Jaspers) 所說： 希臘和現代的偉大悲劇卻在年代的轉換之際孕生。 [2] 根據徐靈昭《長生殿.序》說： 歲戊辰 (1688) 先生 (洪昇) 皇取而更定之 。而第三年就發生了佟皇后喪期期間內演唱《長生殿》之禍，所以，《長生殿》大約完成於康熙二十七年。就創作過程，洪昇自言： 蓋經十餘年，三易稿而始成 (《長生殿﹒例言))。其中，第一稿是洪昇偶感李白之遇，而作《沉香亭》；第二稿《舞霓裳》則省去李白部分，而加入李泌輔肅宗中興；直至第三稿，洪昇 念情之所種，在帝主家罕有 (《長生殿.例言》) ，而創作了《長生殿》。 除此之外，在洪昇的《長生殿》之前，已經有不少以李、楊的愛情故事為內容的作品。尤為重要的有唐代白居易《長恨歌》、元代白樸《梧桐雨》、明代吳世美《驚鴻記》及屠隆《綵毫記》。 而《長生殿》面世後，隨即受到廣大觀眾所愛戴。有 一時朱門綺席，酒社歌樓，非此曲不奏，纏頭為之增價 (徐麟《長生殿.序》)。其後更與《桃花扇》的劇作家孔尚任，並稱 南洪北孔 。一般更有“論文者崇孔，言律者尊洪 的說法。然而，《長生殿》 除了音律堪稱外，其他部分也是不容忽視的。以下我會對《長生殿》 的悲劇結構、悲劇元素和人物性格作出探討

Phenotypic comparison and DNA sequencing analysis of a wild-type and a pediocin-resistant mutant of Listeria ivanovii

Listeria ivanovii is one of the two pathogenic species within the genus Listeria, the other being L. monocytogenes. In this study, we generated a stable pediocin resistant mutant Liv-r1 of a L. ivanovii strain, compared phenotypic differences between the wild-type and the mutant, localised the pediocin-induced mutations in the chromosome, and analysed the mechanisms behind the bacteriocin resistance. In addition to pediocin resistance, Liv-r1 was also less sensitive to nisin. The growth of Liv-r1 was significantly reduced with glucose and mannose, but less with cellobiose. The cells of Liv-r1 adsorbed less pediocin than the wild-type cells. Consequently, with less pediocin on the cell surface, the mutant was also less leaky, as shown as the release of intracellular lactate dehydrogenase to the supernatant. The surface of the mutant cells was more hydrophobic than that of the wild-type. Whole genome sequencing revealed numerous changes in the Liv-r1 chromosome. The mutations were found e.g., in genes encoding sigma-54-dependent transcription regulator and internalin B, as well as in genes involved in metabolism of carbohydrates such as glucose and cellobiose. Genetic differences observed in the mutant may be responsible for resistance to pediocin but no direct evidence is provided.Peer reviewe

Astragalus Polysaccharides Lowers Plasma Cholesterol through Mechanisms Distinct from Statins

To determine the efficacy and underlying mechanism of Astragalus polysaccharides (APS) on plasma lipids in hypercholesterolemia hamsters. The effect of APS (0.25g/kg/d) on plasma and liver lipids, fecal bile acids and neutral sterol, cholesterol absorption and synthesis, HMG-CoA reductase activity, and gene and protein expressions in the liver and small intestine was investigated in twenty-four hypercholesterolemia hamsters. Treatment periods lasted for three months. APS significantly lowered plasma total cholesterol by 45.8%, triglycerides by 30%, and low-density lipoprotein-cholesterol by 47.4%, comparable to simvastatin. Further examinations revealed that APS reduced total cholesterol and triglycerides in the liver, increased fecal bile acid and neutral sterol excretion, inhibited cholesterol absorption, and by contrast, increased hepatic cholesterol synthesis and HMG-CoA reductase activity. Plasma total cholesterol or low-density lipoprotein-cholesterol levels were significantly correlated with cholesterol absorption rates. APS up-regulated cholesterol-7α-hydroxylase and LDL-receptor gene expressions. These new findings identify APS as a potential natural cholesterol lowering agent, working through mechanisms distinct from statins

In vitro study on human cytomegalovirus affecting early pregnancy villous EVT's invasion function

<p>Abstract</p> <p>Background</p> <p>Human cytomegalovirus (HCMV) is the most common pathogen in uterus during pregnancy, which may lead to some serious results such as miscarriage, stillbirth, cerebellar malformation, fetus developmental retardation, but its pathogenesis has not been fully explained. The hypofunction of extravillous cytotrophoblast (EVT) invasion is the essential pathologic base of some complications of pregnancy. c-erbB-2 is a kind of oncogene protein and closely linked with embryogenesis, tissue repair and regeneration. Matrix metalloproteinase (MMP) is one of the key enzymes which affect EVT migration and invasion function. The expression level changes of c-erbB-2, MMP-2 and MMP-9 can reflect the changes of EVT invasion function.</p> <p>Results</p> <p>To explore the influence of HCMV on the invasion function of EVT, we tested the protein expression level changes of c-erbB-2, MMP-2 and MMP-9 in villous explant cultured in vitro infected by HCMV, with the use of immunohistochemistry SP method and western blot. We confirmed that HCMV can reproduce and spread in early pregnancy villus; c-erbB-2 protein mainly expressed in normal early pregnancy villous syncytiotrophoblast (ST) remote plasma membrane and EVT, especially remote EVT cell membrane in villous stem cell column, little expressed in ST proximal end cell membrane and interstitial cells; MMP-2 protein primarily expressed in early pregnancy villous EVT endochylema and rarely in villous trophoblast (VT), ST and interstitial cells; MMP-9 protein largely expressed in early pregnancy villous mesenchyme, EVT and VT endochylema. Compared with control group, the three kinds of protein expression level in early pregnancy villus of virus group significantly decreased (P < 0.05).</p> <p>Conclusion</p> <p>HCMV can infect villus in vitro and cause the decrease of early pregnancy villous EVT's invasion function.</p

Co-targeting RNA Polymerases IV and V Promotes Efficient De Novo DNA Methylation in Arabidopsis.

The RNA-directed DNA methylation (RdDM) pathway in plants controls gene expression via cytosine DNA methylation. The ability to manipulate RdDM would shed light on the mechanisms and applications of DNA methylation to control gene expression. Here, we identified diverse RdDM proteins that are capable of targeting methylation and silencing in Arabidopsis when tethered to an artificial zinc finger (ZF-RdDM). We studied their order of action within the RdDM pathway by testing their ability to target methylation in different mutants. We also evaluated ectopic siRNA biogenesis, RNA polymerase V (Pol V) recruitment, targeted DNA methylation, and gene-expression changes at thousands of ZF-RdDM targets. We found that co-targeting both arms of the RdDM pathway, siRNA biogenesis and Pol V recruitment, dramatically enhanced targeted methylation. This work defines how RdDM components establish DNA methylation and enables new strategies for epigenetic gene regulation via targeted DNA methylation