Co-transfer of two plasmids determining bacteriocin production and sucrose utilization in Streptococcus faecium

Abstract Streptococcus faecium strain 25 produced a bacteriocin (enterococcin Sf25), metabolized sucrose and contained three plasmids of 2.4, 4.7 and 13.0 MDa. Plasmids Sfp2.4 and Sfp4.7 were cotransferred in a filter mating procedure to sucrose negative and bacteriocin negative S. faecium strain M16. Strain M16 harboured a nonselftransferable plasmid Sfp 19.1 MDa, which was responsible for erythromycin resistance. Transcipient cells of S. faecium M16 contained the 19.1-MDa plasmid and plasmids Sfp2.4 and Sfp4.7, produced the enterococcin Sf25 and gained the ability to degrade sucrose.     

The feeding ecology of Stephen's lory and nectar availability in its food plants

Stephen's lory, Vini stepheni , is one of four landbirds which are endemic to Henderson Island and until recently, its habits and ecology were unknown. I studied the diet and feeding ecology of Stephen's lory with particular reference to nectar variation in dominant food plants. Stephen's lory feeds on nectar, pollen and fruits from a variety of plants with lepidopteran larvae also forming a large component of the diet. The two plants which were dominant nectar sources for Stephen's lory produced flowers with very different nectar yields. Scaevola sericea flowers contained larger maximum volumes of more concentrated nectar than Timonius polygamus flowers. However, Scaevola flowers were a less predictable nectar resource, and grew at much lower densities, than Timonius flowers. Lories fed on the two flower types at different frequencies and it was hypothesized that the net rate of energy gained from feeding from a similar sized patch of the two plant species was comparable. Although nectar volumes of Timonius polygamus flowers decreased from the early mornings up until late afternoons, the lories did not show a corresponding daily pattern of foraging behaviour. Nectar yields also increased with the age of Timonius flowers. Stephen's lory has probably been the least affected of its genus by adverse changes to its habitat, and any information gained on the species may be useful when conservation measures of other Vini species are addressed.     

The Circadian Clock Gene Circuit Controls Protein and Phosphoprotein Rhythms in Arabidopsis thaliana

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Enzymatic Transesterification of Sugars in Anhydrous Pyridine

Enzymatic transesterification of sucrose, α-methyl glucopyranoside and octyl-D-glucopyranoside with tributyrin, vinyl octanoate and vinyl laurate was carried out in nearly anhydrous pyridine using the bacterial protease, alcalase. The enzyme monoacylated both the α and β anomers of octyl-D-glucopyranoside. In addition to the preferential acylation of the primary hydroxyl groups of the sugars, the enzyme also acylated the secondary hydroxyl groups in lower quantities. The generated sugar mono-, di- and triesters were purified by flash column chromatography and the positions of acylation were assigned by ¹³C NMR.     

Large-Scale Purification of Porcine or Bovine Photoreceptor Outer Segments for Phagocytosis Assays on Retinal Pigment Epithelial Cells

Analysis of one of the vital functions of retinal pigment epithelial (RPE) cells, the phagocytosis of spent aged distal fragments of photoreceptor outer segments (POS) can be performed in vitro. Photoreceptor outer segments with stacks of membranous discs containing the phototransduction machinery are continuously renewed in the retina. Spent POS are eliminated daily by RPE cells. Rodent, porcine/bovine and human RPE cells recognize POS from various species in a similar manner. To facilitate performing large series of experiments with little variability, a large stock of POS can be isolated from porcine eyes and stored frozen in aliquots. This protocol takes advantage of the characteristic of photopigments that display an orange color when kept in the dark. Under dim red light, retinae are collected in a buffer from opened eyecups cut in halves. The retinal cell suspension is homogenized, filtered and loaded onto a continuous sucrose gradient. After centrifugation, POS are located in a discrete band in the upper part of the gradient that has a characteristic orange color. POS are then collected, spun, resuspended sequentially in wash buffers, counted and aliquoted. POS obtained this way can be used for phagocytosis assays and analysis of protein activation, localization or interaction at various times after POS challenge. Alternatively, POS can be labeled with fluorophores, e.g., FITC, before aliquoting for subsequent fluorescence quantification of POS binding or engulfment. Other possible applications include the use of modified POS or POS challenge combined with stress conditions to study the effect of oxidative stress or aging on RPE cells.     

左卡尼汀联合蔗糖铁对血液透析患者肾性贫血及氧化应激的影响

目的:探讨左卡尼汀联合蔗糖铁对血透患者肾性贫血及氧化应激的影响。方法:抽选我院2010年3月-2013年5月行维持血透治疗的肾性贫血患者79例,采用数字表法分为对照组(39例)和观察组(40例),对照组采用促红细胞生成素(EPO)、单用蔗糖铁及常规对症治疗,观察组在对照组基础上联用左卡尼汀治疗。比较两组患者治疗前、治疗6个月后血红蛋白(Hb)、血细胞比容(Hct)、血浆铁蛋白(SF)、转铁蛋白饱和度(TSAT)、晚期蛋白质氧化产物(AOPP)及血丙二醛(MDA)水平,并对两组治疗开始时、治疗3、6个月时EPO使用剂量进行比较。结果:治疗6个月后,观察组患者Hb、Hct、SF、TSAT明显高于对照组(P0.05),AOPP、MDA明显低于对照组(P0.05);对照组从治疗开始到治疗6个月时一直维持较高的EPO使用剂量,而观察组EPO用量依次递减,至治疗6个月时EPO用量显著低于对照组(P0.05)。结论:左卡尼汀能联合蔗糖铁治疗肾性贫血的疗效显著,能有效缓解氧化应激反应,降低EPO用量,值得临床推广。     

两种耐热磷酸化酶的构建及高效催化合成红景天苷

目的:使用表达耐热蔗糖磷酸化酶的大肠杆菌重组工程菌E. coli BL21/pET-Spase和耐热纤维二糖磷酸化酶的大肠杆菌重组工程菌E. coli BL21/pET-Cpase,发酵培养后粗酶液作为催化剂,以价格低廉的蔗糖为原料合成红景天苷。方法:分别构建耐热蔗糖磷酸化酶和耐热纤维二糖磷酸化酶大肠杆菌重组菌,然后将重组菌、蔗糖、酪醇和磷酸混合,得到反应混合物,使反应混合物在45℃下转化,而产生红景天苷。结果:在耐热蔗糖磷酸化酶酶液1200 U/L、耐热纤维二糖磷酸化酶酶液500 U/L、蔗糖110 g/L、酪醇30 g/L和磷酸50 m M的浓度下,反应条件为pH 7.0、温度45℃、转速50转/分、反应时间32小时后,红景天苷浓度达到23.7 g/L。结论:本研究使用蔗糖磷酸化酶和纤维二糖磷酸化酶联合催化的工艺,成功地高收率合成了红景天苷。同时,本研究构建的耐热磷酸化酶酶活高,处理简单,为拓展糖苷类似物的合成提供了一种新的方法。