从基因组分析贾第虫的核糖体合成系统

为探讨贾第虫细胞核内核糖体合成系统, 及与典型的真核生物有何差异, 首先, 确定在典型真核生 物中参与核糖体合成的条共有的保守蛋白, 然后用这些蛋白搜索贾第虫基因组以调查它们在贾第虫中的直 系同源蛋白的情况, 以对贾第虫的核糖体合成系统作一了解。结果表明贾第虫具有条这些蛋白的直系同 源蛋白, 包括参与甲基化和假尿嚓咙化的蛋白复合体成员, 以及存在于、和复合体中的蛋 白。贾第虫的核糖体合成系统与典型的真核生物相似, 但还有条蛋白在贾第虫基因组中找不到同源蛋白。 这意味着贾第虫的核糖体合成系统较典型的真核生物简单。贾第虫虽然没有核仁结构, 但其核糖体亚基合成的 途径和机制可能与真核细胞相似, 参与的成分不同于无核仁结构的原核生物, 可能相对简单。

几类“无线粒体”原生动物进化地位的探讨* ——来自DNA 拓扑异构酶Ⅱ的系统分析证据

以贾第虫、毛滴虫、内变形虫和微孢子虫等为代表的几类寄生原生动物曾因为“无线粒 体”, 再加上其他一些似乎介于原核和真核细胞之间的原始特点和分子系统树中它们往往处在真 核生物的最基部等证据, 而被有些人认为是目前已知的一类最原始的真核生物类群——Archezoa, 其进化地位应该是处在真核细胞通过“内共生”产生线粒体之前的极早阶段. 这一观点一度被部 分学者认为对探讨真核细胞(生物)的起源、进化极为重要, 是进化生物学上的重要突破. 然而, 近 年来不断有研究对此提出质疑. 我们首先扩增、测序并鉴定了蓝氏贾第虫、阴道毛滴虫和痢疾内 变形虫的DNA 拓扑异构酶Ⅱ序列, 再结合GenBank 数据库中已有的脑炎微孢子虫和其他一系列 处在不同进化地位的真核生物的相应序列数据, 用多种方法构建出分子系统树, 对这些“无线粒 体”原生动物的进化地位进行了探讨. 结果表明, 由于DNA 拓扑异构酶Ⅱ的特点和可以克服“长 枝吸引”等以往分子系统分析中的不足, 所构建的系统树不仅能有效地反映出已普遍接受的真核 生物各主要类群的系统关系, 而且显示出这些“无线粒体”原生动物不同于以前系统树所推测的 进化地位: 它们并非是最早分支出来的真核生物, 而是在具有线粒体的生物如动基体类或菌虫类 等之后才分化的、分别属于不同进化地位的类群. 结合近来在它们中发现了类似线粒体细胞器的 证据, 我们认为这些“无线粒体”的原生动物虽然其中有些种类(如以贾第虫为代表的双滴虫类)进 化地位很低等, 但总体上并非过去所认为的那么极端原始, 它们应该是线粒体产生之后因适应长 期的无氧条件下的内寄生生活方式才分别分化出来的多源发生的不同生物类群.

内变形虫类(Entamoeba)的进化地位

内变形虫类不仅因其寄生致病性而长期备受关注, 它们的进化地位也是一个十分令人注目的问 题. 由于曾认为其不具线粒体等细胞器, 有人将其与其他的“不具线粒体”的原生动物统称为archezoa, 认为它们是在线粒体产生之前即已分化的极原始真核生物, 处在原核生物向真核生物的过渡阶段. 然 而, 近年来的研究表明, 内变形虫类是具有线粒体等细胞器的, 其线粒体可能特化成了后来才发现的 crypton 或mitosome. 近来的分子系统研究也表明, 它们应该是具有(或曾经具有)线粒体的. 我们的 DNA 拓扑异构酶Ⅱ分子系统分析明显显示它们的分化应该是在很多具线粒体的生物分化之后. 本文就 这些研究情况进行了较全面的概述,并对其进化地位进行了进一步分析探讨.

蓝氏贾第虫核纤层蛋白基因的初步研究

贾第虫一度被认为是迄今已知的最原始的真核细胞, 但近来争议日盛。利用PCR 和测序等技术, 对 蓝氏贾第虫( Giardia lamblia) 的核纤层蛋白(lamin) 基因进行了研究。结果表明: 蓝氏贾第虫基因组中存在 一个编码具有明显lamin 特征的基因序列。如该基因序列的3′- 端具有编码与核内膜亲和的特征性模体(motif ) CaaX 的序列; 具有B 型lamin 基因所特有的高度保守的27 bp 片段, 该片段编码高度保守的位于α螺旋杆状区 的9 氨基酸片段等。同时, 这些序列特征又与多细胞的后生动物存在一定差异。这些事实说明在贾第虫中已经 进化产生了典型真核细胞的B 型lamin (基因) 或至少是类似B 型的lamin (基因) , 该生物的进化地位可能并 非过去所认为的那么原始。

Characterization of the Kepler-101 planetary system with HARPS-N. A hot super-Neptune with an Earth-sized low-mass companion

We characterize the planetary system Kepler-101 by performing a combined differential evolution Markov chain Monte Carlo analysisof Kepler data and forty radial velocities obtained with the HARPS-N spectrograph. This system was previously validated and iscomposed of a hot super-Neptune, Kepler-101b, and an Earth-sized planet, Kepler-101c. These two planets orbit the slightly evolvedand metal-rich G-type star in 3.49 and 6.03 days, respectively. With mass Mp = 51.1+5.1−4.7 M⊕, radius Rp = 5.77+0.85−0.79 R⊕, and density ρp = 1.45+0.83 −0.48 g cm−3, Kepler-101b is the first fully characterized super-Neptune, and its density suggests that heavy elements makeup a significant fraction of its interior; more than 60% of its total mass. Kepler-101c has a radius of 1.25+0.19−0.17 R⊕, which implies theabsence of any H/He envelope, but its mass could not be determined because of the relative faintness of the parent star for highly precise radial-velocity measurements (Kp = 13.8) and the limited number of radial velocities. The 1σ upper limit, Mp < 3.8 M⊕, excludes a pure iron composition with a probability of 68.3%. The architecture of the planetary system Kepler-101 − containing aclose-in giant planet and an outer Earth-sized planet with a period ratio slightly larger than the 3:2 resonance − is certainly of interest for scenarios of planet formation and evolution. This system does not follow the previously reported trend that the larger planet has the longer period in the majority of Kepler systems of planet pairs with at least one Neptune-sized or larger planet.

Molecular classification of non-invasive breast lesions for personalised therapy and chemoprevention

Breast cancer screening has led to a dramatic increase in the detection of pre-invasive breast lesions. While mastectomy is almost guaranteed to treat the disease, more conservative approaches could be as effective if patients can be stratified based on risk of co-existing or recurrent invasive disease.Here we use a range of biomarkers to interrogate and classify purely non-invasive lesions (PNL) and those with co-existing invasive breast cancer (CEIN). Apart from Ductal Carcinoma In Situ (DCIS), relative homogeneity is observed. DCIS contained a greater spread of molecular subtypes. Interestingly, high expression of p-mTOR was observed in all PNL with lower expression in DCIS and invasive carcinoma while the opposite expression pattern was observed for TOP2A.Comparing PNL with CEIN, we have identified p53 and Ki67 as predictors of CEIN with a combined PPV and NPV of 90.48% and 43.3% respectively. Furthermore, HER2 expression showed the best concordance between DCIS and its invasive counterpart.We propose that these biomarkers can be used to improve the management of patients with pre-invasive breast lesions following further validation and clinical trials. p53 and Ki67 could be used to stratify patients into low and high-risk groups for co-existing disease. Knowledge of expression of more actionable targets such as HER2 or TOP2A can be used to design chemoprevention or neo-adjuvant strategies. Increased knowledge of the molecular profile of pre-invasive lesions can only serve to enhance our understanding of the disease and, in the era of personalised medicine, bring us closer to improving breast cancer care.

Serum cortisol, lactate and creatinine concentrations in Thoroughbred fillies of different ages and states of training

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Storage of sugarcane stalks (Saccharum officinarum cv. SP 79-1011) in low oxygen atmospheres and the effects on enzymatic browning

Although sugarcane consumption is very popular worldwide there are few studies regarding the postharvest storage of stalks that focus on controlling enzymatic browning. The objective of this study was to evaluate the quality of sugarcane stalks stored at 10±1°C in controlled atmosphere with various oxygen (O2) levels (1kPa, 5kPa, 10kPa, 15kPa, and 21kPa) and to verify the effect of this storage on the activities of polyphenoloxidase (PPO) and peroxidase (POD). At 1kPa and 5kPa O2, the stalks' respiratory rate, POD activity, and reducing sugar content were significantly less (P<0.05) than at higher O2 concentrations. In contrast, low O2 levels did not affect PPO activity or influence cane coloration. These results can be used to guide the choice of plastic films, making it possible to store sugarcane stalks in a controlled atmosphere. © 2013 Elsevier B.V.

Conservação refrigerada de abacate ‘Hass’ e ‘Fuerte’ submetidos à atmosferas modificadas ativas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Qualidade do abacate 'HASS' frigoarmazenado submetido a atmosferas modificadas ativas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conservação refrigerada de abacate 'hass' e 'fuerte' submetidos à atmosferas modificadas ativas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)