Cell Division of Escherichia coli: Control by Membrane Organization

Cells of certain strains of Escherichia coli, after transfer from 37 to 45 C and incubation for 16 min, were observed to swell and subsequently divide synchronously. This swelling and the resulting stretching of the membrane are proposed to be the basis for the synchronous division. Four lines of evidence support this hypothesis. First, osmotic protection by the addition of either sodium chloride or sucrose at the time of heat shock prevents both swelling and synchrony. Second, a mutant neither swelled nor divided synchronously after heat shock. Third, cells grown for several generations with 10% sucrose in the medium swelled and divided synchronously upon transfer to medium without sucrose. Fourth, the mutant not synchronized by heat shock also swelled and underwent synchronous division after the osmotic shift. A tentative model is suggested for the normal control of division, based on membrane configuration at the septation site.     

Identity of tendon stem cells – how much do we know?

Tendon stem cells are multi‐potent adult stem cells with broad differentiation plasticity that render them of great importance in cell‐based therapies for the repair of tendons. We called them tendon‐derived stem cells (TDSCs) to indicate the tissue origin from which the stem cells were isolated in vitro. Based on the work of other sources of MSCs and specific work on TDSCs, some properties of TDSCs have been characterized / implicated in vitro. Despite these findings, tendon stem cells remained controversial cells. This was because MSCs residing in different organs, although very similar, were not identical cells. There is evidence of differences in stem cell‐related properties and functions related to tissue origins. Similar to other stem cells, tendon stem cells were identified and characterized in vitro. Their in vivo identities, niche (both anatomical locations and regulators) and roles in tendons were less understood. This review aims to summarize the current evidence of the possible anatomical locations and niche signals regulating the functions of tendon stem cells in vivo. The possible roles of tendon stem cells in tendon healing and non‐healing are presented. Finally, the potential strategies for understanding the in vivo identity of tendon stem cells are discussed.     

SARS—CoV N蛋白与病毒mRNA相互作用的初步研究

SARS冠状病毒(SARS-CoV)是一种新型的冠状病毒,其基因组大小约为30,000 nt,为单股正链RNA。病毒基因中的1-72个核甘酸为前导序列。核衣壳(Nucleocapsid,N)蛋白是冠状病毒的主要结构蛋白,它在病毒基因转录,翻译以及病毒颗粒包装中起重要作用。在本研究中,我们通过PCR的方法从SARS-CoV cDNA中克隆N基因,将基因克隆到大肠杆菌表达载体中,经表达纯化获得大量重组蛋白,通过亲和层析和凝胶过滤层析获得高纯度的N蛋白。同时构建前导RNA的转录模板,经体外转录得到地高辛标记的RNA。使用Northwestern分析技术,我们证实纯化的N蛋白在体外可以与RNA发生特异性的结合。N蛋白与病毒RNA的结合特性及其在病毒生活周期中的所起作用的初步研究,为下一步设计出有效的阻断病毒周期从而达到抗病毒目的的药物或疫苗奠定了基础。     

Radiation modulating properties of derivates of 1,4-dihydropyridine and 1,2,3,4,5,6,7,8,9,10-decahydroacridine-1,8 dione

First attempt to analyse radiation modifying action of 52 compounds--derivatives of 1,4-dihydropyridine is presented. Many of these compounds have electrodonating and antioxidative activities. Local radioprotective effects of the substances has been studied using experimental model with partial beta- and X-rays exposure of sole skin in rats to doses of 40 and 30 Gy. Comparison of drug effectiveness and chemical structure revealed the changes of activity dependence due to modification of peripheral radicals of 1,4-dihydropyridine ring. Radioprotective and radiosensitizing compounds with general low toxicity have been found. It is suggested to use the most active compounds for the development of medicinal forms for prevention of local skin and mucosal radiation injuries. Positive results have been obtained with dieton a radioprotective compound of the same type, in radiotherapy.     

An engineered PrPsc-like molecule from the chimera of mammalian prion protein and yeast Ure2p prion-inducing domain

Production of the pathogenic prion isoform PrP^sc-like molecules is thought to be useful forunderstanding the mysterious mechanism of conformational conversion process of prion diseases andproving the “protein-only“ hypothesis. In this report, an engineered PrP^sc-like conformation was producedfrom a chimera of mammalian bovine prion protein (bPrP) and yeast Ure2p prion-inducing domain (UPrD).Compared with the normal form of bPrP, the engineered recombinant protein, termed bPrP-UPrD,spontaneously aggregated into ordered fibrils under physiological condition, displaying amyloid-likecharacteristics, such as fibrillar morphology, birefringence upon binding to Congo red and increasedfluorescence intensity with Thioflavine T. Limited resistance to protease K digestion and CD spectroscopyexperiments suggested that the structure of bPrP-UPrD had been changed, and adopted a new, high contentB-sheet conformation during the fibrils formation. Moreover, bPrP-UPrD amyloid fibrils could recruit moresoluble forms into the aggregates. Therefore, the engineered molecules could mimic significant behaviors of PrP^se and will be helpful for further understanding the mechanism of conformational conversion process.     

Neither lipophilicity nor membrane-perturbing potency of phenothiazine maleates correlate with the ability to inhibit P-glycoprotein transport activity

Although phenothiazines are known as multidrug resistance modifiers, the molecular mechanism of their activity remains unclear. Since phenothiazine molecules are amphiphilic, the interactions with membrane lipids may be related, at least partially, to their biological effects. Using the set of phenothiazine maleates differing in the type of phenothiazine ring substitution at position 2 and/or in the length of the alkyl bridge-connecting ring system and side chain group, we investigated if their ability to modulate the multidrug resistance of cancer cells correlated with model membrane perturbing potency. The influence exerted on lipid bilayers was determined by liposome/buffer partition coefficient measurements (using the absorption spectra second-derivative method), fluorescence spectroscopy and calorimetry. Biological effects were assessed by a flow cytometric functional test based on differential accumulation of fluorescent probe DiOC(2)(3) by parental and drug-resistant cells. We found that all phenothiazine maleates were incorporated into lipid bilayers and altered their biophysical properties. With only few exceptions, the extent of membrane perturbation induced by phenothiazine maleates correlated with their lipophilicity. Within the group of studied derivatives, the compounds substituted with CF(3)- at position 2 of phenothiazine ring were the most active membrane perturbants. No clear relation was found between effects exerted by phenothiazine maleates on model membranes and their ability to modulate P-glycoprotein transport activity.     

Systematic review of comparative efficacy and tolerability of calcipotriol in treating chronic plaque psoriasis

ObjectivesTo evaluate the comparative efficacy and tolerability of topical calcipotriol in the treatment of mild to moderate chronic plaque psoriasis.DesignQuantitative systematic review of randomised controlled trials.Subjects6038 patients with plaque psoriasis reported in 37 trials.ResultsCalcipotriol was at least as effective as potent topical corticosteroids, calcitriol, short contact dithranol, tacalcitol, coal tar, and combined coal tar 5%, allantoin 2%, and hydrocortisone 0.5%. Calcipotriol caused significantly more skin irritation than potent topical corticosteroids (number needed to treat to harm for irritation 10, 95% confidence interval 6 to 34). Calcipotriol monotherapy also caused more irritation than calcipotriol combined with a potent topical corticosteroid (6, 4 to 8). However, the number needed to treat for dithranol to produce lesional or perilesional irritation was 4 (3 to 5). On average, treating 23 patients with short contact dithranol led to one more patient dropping out of treatment owing to adverse effects than if they were treated with calcipotriol.ConclusionsCalcipotriol is an effective treatment for mild to moderate chronic plaque psoriasis, more so than calcitriol, tacalcitol, coal tar, and short contact dithranol. Only potent topical corticosteroids seem to have comparable efficacy at eight weeks. Although calcipotriol caused more skin irritation than topical corticosteroids this has to be balanced against the potential long term effects of corticosteroids. Skin irritation rarely led to withdrawal of calcipotriol treatment. Longer term comparative trials of calcipotriol versus dithranol and topical corticosteroids are needed to see whether these short term benefits are mirrored by long term outcomes such as duration of remission and improvement in quality of life.     

附睾局部组织肾素血管紧张素系统(英文)

附睾内液体微环境对精子的成熟和贮藏是相当重要的。附睾液体的形成取决于附睾上皮的吸收与分泌功能,而先前的实验已经证明：这些吸收与分泌的活动是受到除神经激素以外旁分泌与自分泌的调控。虽然肾素血管紧张素系统（ＲＡＳ）在很多组织上旁分泌与自分泌的作用已多有报导,但其在附睾的存在及作用仍鲜为人知。本综述总结了本实验室在这方面的研究结果,通过使用不同的实验方法,例如,免疫组织化学,放射免疫分析,分子生物学及短路电流电生理学方法,我们得到的结果显示了ＲＡＳ主要成员在附睾的分布（Ｆｉｇ．１）和表达,并阐明了血管紧张素ＩＩ对附睾阴离子分泌的调控作用（Ｆｉｇｓ．２＆３）。本综述还就血管紧张素ＩＩ对附睾旁分泌与自分泌的作用及其机制（Ｆｉｇ．４）,以及对精子功能的作用进行了讨论。     

Purification and characterization of recombinant microsomal prostaglandin E synthase-1

Recombinant human microsomal prostaglandin E(2) synthase-1 (mPGES-1) was expressed in a baculovirus-Sf9 cell system. The mPGES-1 was solubilized from Sf9 cell membranes with diheptanoylphosphatidylcholine and purified in the presence of octylglucoside using hydroxyapatite column chromatography. The K(m) values of the substrates PGH(2) and GSH were 14 microM and 0.75 mM, respectively, with the purified enzyme. The specific activity (4 micromol/min/mg) was increased 3-5-fold by non-ionic and zwitterionic detergents. Kinetic analysis showed that dodecylmaltoside increases V(max) but does not affect the K(m) values of either substrate. Several other thiol-containing compounds were tested as glutathione replacements, none of which yielded detectable enzyme activity. During enzyme catalysis, glutathione was not oxidized and therefore can be considered an enzyme cofactor. No glutathione transferase or peroxidase activity could be determined with a range of potential substrates. The results show that purified mPGES-1 has a specific activity similar to Cox-2, consistent with its postulated role in Cox-2 mediated PGE(2) formation.