Deletion of the major peroxiredoxin Tsa1 alters telomere length homeostasis

Reactive oxygen species (ROS) are proposed to play a major role in telomere length alterations during aging. The mechanisms by which ROS disrupt telomeres remain unclear. In Saccharomyces cerevisiae, telomere DNA consists of TG_(1–3) repeats, which are maintained primarily by telomerase. Telomere length maintenance can be modulated by the expression level of telomerase subunits and telomerase activity. Additionally, telomerase‐mediated telomere repeat addition is negatively modulated by the levels of telomere‐bound Rap1‐Rif1‐Rif2 protein complex. Using a yeast strain defective in the major peroxiredoxin Tsa1 that is involved in ROS neutralization, we have investigated the effect of defective ROS detoxification on telomere DNA, telomerase, telomere‐binding proteins, and telomere length. Surprisingly, the tsa1 mutant does not show significant increase in steady‐state levels of oxidative DNA lesions at telomeres. The tsa1 mutant displays abnormal telomere lengthening, and reduction in oxidative exposure alleviates this phenotype. The telomere lengthening in the tsa1 cells was abolished by disruption of Est2, subtelomeric DNA, Rap1 C‐terminus, or Rif2, but not by Rif1 deletion. Although telomerase expression and activity are not altered, telomere‐bound Est2 is increased, while telomere‐bound Rap1 is reduced in the tsa1 mutant. We propose that defective ROS scavenging can interfere with pathways that are critical in controlling telomere length homeostasis.     

Defective Repair of Uracil Causes Telomere Defects in Mouse Hematopoietic Cells

Uracil in the genome can result from misincorporation of dUTP instead of dTTP during DNA synthesis, and is primarily removed by uracil DNA glycosylase (UNG) during base excision repair. Telomeres contain long arrays of TTAGGG repeats and may be susceptible to uracil misincorporation. Using model telomeric DNA substrates, we showed that the position and number of uracil substitutions of thymine in telomeric DNA decreased recognition by the telomere single-strand binding protein, POT1. In primary mouse hematopoietic cells, uracil was detectable at telomeres, and UNG deficiency further increased uracil loads and led to abnormal telomere lengthening. In UNG-deficient cells, the frequencies of sister chromatid exchange and fragility in telomeres also significantly increased in the absence of telomerase. Thus, accumulation of uracil and/or UNG deficiency interferes with telomere maintenance, thereby underscoring the necessity of UNG-initiated base excision repair for the preservation of telomere integrity.     

Deletion of Ogg1 DNA glycosylase results in telomere base damage and length alteration in yeast

Telomeres consist of short guanine‐rich repeats. Guanine can be oxidized to 8‐oxo‐7,8‐dihydroguanine (8‐oxoG) and 2,6‐diamino‐4‐hydroxy‐5‐formamidopyrimidine (FapyG). 8‐oxoguanine DNA glycosylase (Ogg1) repairs these oxidative guanine lesions through the base excision repair (BER) pathway. Here we show that in Saccharomyces cerevisiae ablation of Ogg1p leads to an increase in oxidized guanine level in telomeric DNA. The ogg1 deletion (ogg1Δ) strain shows telomere lengthening that is dependent on telomerase and/or Rad52p‐mediated homologous recombination. 8‐oxoG in telomeric repeats attenuates the binding of the telomere binding protein, Rap1p, to telomeric DNA in vitro. Moreover, the amount of telomere‐bound Rap1p and Rif2p is reduced in ogg1Δ strain. These results suggest that oxidized guanines may perturb telomere length equilibrium by attenuating telomere protein complex to function in telomeres, which in turn impedes their regulation of pathways engaged in telomere length maintenance. We propose that Ogg1p is critical in maintaining telomere length homoeostasis through telomere guanine damage repair, and that interfering with telomere length homoeostasis may be one of the mechanism(s) by which oxidative DNA damage inflicts the genome.     

Subcellular fractionation methods and strategies for proteomics

Developments in subcellular fractionation strategies have provided the means to profile and analyze the protein composition of organelles and cellular structures by proteomics. Here, we review the application of classical (e.g. density gradient centrifugation) and emerging sophisticated techniques (fluorescent-assisted organelle sorting) in the fractionation, and statistical/bioinformatics tools for the prediction of protein localization in subcellular proteomics. We also review the validation methods currently used (such as microscopy, RNA interference and multiple reaction monitoring) and discuss the importance of verification of the results obtained in subcellular proteomics. Finally, the numerous challenges facing subcellular proteomics including the dynamics of organelles are being examined. However, complementary approaches such as modern statistics, bioinformatics and large-scale integrative analysis are beginning to emerge as powerful tools to proteomics for analyzing subcellular organelles and structures.     

Microcarrier culture of fish cells and viruses in cell culture bioreactor.

This article deals with the culture of grass carp (Ctenopharyngodon idellus) lip and embryo cells on Cytodex 3 and GT-2 microcarriers in a 1.5-L cell culture bioreactor to propagate grass carp hemorrhage virus. The cells and viruses were successfully cultivated at 26 degrees C, pH 7.0, and dissolved oxygen 40% of air saturation. The cell density achieved was as high as 7.4 x 10(6) cells/mL, and the virus titre reached 6.75 log LD50/0.5 mL from an initial 3.00 log LD50/0.5 mL. The results present broad prospects for fish virus vaccine production.     

被子植物翅果的多样性及演化

翅果能够依靠风力进行传播, 可能是被子植物快速散布和物种分化的一个重要因素。狭义的翅果是指果皮延伸成翅且不开裂的干果; 广义的翅果则包括果皮、花被片或苞片形成果翅的所有果实。根据果翅形态及其生长方式的不同, 广义的翅果可分为单侧翅果、周位翅果(圆翅果与蝶翅果)、棱翅果、披针翅果、翼状萼翅果、叶状苞翅果6种类型, 其空中运动方式有自旋式(单侧翅果、翼状萼翅果)、波浪式(周位翅果、叶状苞翅果)、翻滚自旋式(周位翅果)、直升机式(披针翅果、翼状萼翅果)和滚筒式(棱翅果)。棱翅果与圆翅果在被子植物基部类群樟目就有发生, 并同时出现在单子叶植物和双子叶植物中, 可能是最早出现的翅果类型。翅果的演化过程呈现出果翅数量增加、果翅偏向单侧和果翅负荷(果实质量与果翅面积之比)降低的趋势, 以利于适应较小的风并增加传播距离。果翅除了促进果实与种子的风力传播外, 还具有物理防御、调节种子萌发和促进二次传播等作用。泛热带分布的金虎尾科有着极其丰富的翅果类型, 与其多次跨洋长距离扩散密切相关, 可以作为研究翅果适应与演化的一个模式类群。结合生态和演化-发育生物学方法, 研究不同类型翅果在适应风力传播方面的差异、萼片或苞片发育成翅的分子与遗传机制、翅果不同类型的演化历史及其对被子植物物种多样性的影响等是今后值得探讨的重要问题。     

The efficacy and feasibility of total reconstruction versus nontotal reconstruction of the pelvic floor on short-term and long-term urinary continence rates after radical prostatectomy: a meta-analysis

Background

Recently, total pelvic floor reconstruction (TR) has been the treatment of choice for improving urinary incontinence (UI) after radical prostatectomy (RP). However, the superiority of TR with respect to urinary continence recovery following RP remains controversial. This study identified the effect of TR versus nonTR of the pelvic floor on short-term and long-term continence rates after RP.

Methods

A literature search was performed in November 2017 using the PubMed, Embase, and Web of Science databases. Only comparative research or clinical studies reporting urinary continence outcomes was included in the meta-analysis, and the quality of evidence was evaluated using the 2011 Level of Evidence for therapy research.

Results

We analyzed ten studies reporting urinary continence rates after RP at one or more postoperative time points (1, 2, 4, 12, 24, and 52 weeks). TR was associated with significantly better urinary continence outcomes at 1 week (OR 2.76, 95% CI 1.58–4.84, P?<?0.001), 2 weeks (OR 2.57, 95% CI 1.74–3.80, P?<?0.001), 4 weeks (OR 2.61, 95% CI 1.56–4.38, P?<?0.001), 12 weeks (OR 4.33, 95% CI 2.01–9.33, P?<?0.001), 24 weeks (OR 3.83, 95% CI 1.54–9.55, P?=?0.004), 52 weeks (OR 4.10, 95% CI 1.80–9.38, P?<?0.001) after RP. There was no difference in the rate of complications between the two arms (OR 0.54, 95% CI 0.19–1.54, P?=?0.25).

Conclusions

Compared with nonTR, TR is significantly and positively associated with a return to continence but not with complication rate in men following RP, suggesting that TR may be useful for decreasing the urinary incontinence rate after surgery.

     

中国小球藻病毒及其分子生物学性质

以小球藻NC64A株系为寄主,从17个省市采集的上百个水样中分离到了11个病毒分离物（BJ－1、BJ－2、BJ－3、BJ－4、FJ－1、FJ－2、NJ－1、HCJ－1、CDT－1、SCB—1、SCC－1）。这些病毒具有许多相同的性质,如均为球形多面体,基因组为300kb的dsDNA。但它们的DNA限制性酶切图谱,碱基组成和蛋白组分等均有差异。FJ－1的主要外壳蛋白的分子量小于54000,其它10个分离物则与PBCV-1一样,主要外壳蛋白的分子量为54000。Westernblot分析的结果显示,除FJ－1外其它病毒分离物与PBCV—1的抗血清有较强的免疫交叉反应。说明这些病毒与PBCV－1的同源性较高。在11个病毒分离物中,FJ－1在蛋白组分、碱基组成等方面与其它分离物和PBCV—1差别较大。     

东江七种鱼类的生活史类型研究

本文通过渐近体长(L∞)、渐近体重(W∞)、生长系数(K)、初次生殖年龄(Tm)、最大年龄(Tmax)、瞬时自然死亡率(M)和性腺指数(Gl)等7个生态学参数来分析鱼类种群生活史类型。根据r-选择和K-选择的典型特征以及各参数间相互关系的显著性,性腺指数、瞬时死亡率和生长系数是判断东江7种鱼类种群偏向rF)和改变渔业补充年龄(tc)时的产量变化,分析产量变化曲线可知,作为偏向r型的种群,提高捕捞强度不能增加渔业产量,适当的捕捞强度可以取得较高的产量;在低龄阶段提高起捕年龄能增加一定产量,但到达一定年龄后再提高起捕年龄,反而引起产量大幅度下降。只有合理控制捕捞强度和起捕年龄,才能获取最大持续产量。       

HLA-G在生殖系统癌中的检测:免疫组织化学研究

为检测生殖系统癌有无HLA-G表达,采用免疫组化LDP法对223例生殖系统癌手术切除标本进行了鼠抗HLA-G单克隆抗体染色,观察了HLA-G在乳腺癌（n=100),卵巢癌（n=30),子宫颈癌（n=30),子宫内膜癌（n=40),前列腺癌（n=20)和睾丸胚胎癌（n=3)中的表达与分布。结果发现,除睾丸胚胎癌外,生殖系统其余部位癌标本可见到40-57.5%的HLA-G阳性表达,HLA-G阳性反应物在癌细胞内呈颗粒状及均质状,主要分布于细胞浆,结果提示,HLA-G表达可能是肿瘤生物学中的普遍现象,生殖系统癌细胞在发生和发展过程中其基因表达有可能出现反分化现象,开始表达HLA-G,从而使癌细胞产生免疫耐受,逃逸宿主的免疫监视。