Metabolic flux estimation--a self-adaptive evolutionary algorithm with singular value decomposition

Metabolic flux analysis is important for metabolic system regulation and intracellular pathway identification. A popular approach for intracellular flux estimation involves using ¹³C tracer experiments to label states that can be measured by nuclear magnetic resonance spectrometry or gas chromatography mass spectrometry. However, the bilinear balance equations derived from ¹³C tracer experiments and the noisy measurements require a nonlinear optimization approach to obtain the optimal solution. In this paper, the flux quantification problem is formulated as an error-minimization problem with equality and inequality constraints through the ¹³C balance and stoichiometric equations. The stoichiometric constraints are transformed to a null space by singular value decomposition. Self-adaptive evolutionary algorithms are then introduced for flux quantification. The performance of the evolutionary algorithm is compared with ordinary least squares estimation by the simulation of the central pentose phosphate pathway. The proposed algorithm is also applied to the central metabolism of Corynebacterium glutamicum under lysine-producing conditions. A comparison between the results from the proposed algorithm and data from the literature is given. The complexity of a metabolic system with bidirectional reactions is also investigated by analyzing the fluctuations in the flux estimates when available measurements are varied.     

SIRT2 regulates adipocyte differentiation through FoxO1 acetylation/deacetylation

The family of mammalian Sirtuin proteins comprises seven members homologous to yeast Sir2. Here we show that SIRT2, a cytoplasmic sirtuin, is the most abundant sirtuin in adipocytes. Sirt2 expression is downregulated during preadipocyte differentiation in 3T3-L1 cells. Overexpression of SIRT2 inhibits differentiation, whereas reducing SIRT2 expression promotes adipogenesis. Both effects are accompanied by corresponding changes in the expression of PPARgamma, C/EBPalpha, and genes marking terminal adipocyte differentiation, including Glut4, aP2, and fatty acid synthase. The mechanism underlying the effects of reduced SIRT2 in 3T3-L1 adipocytes includes increased acetylation of FOXO1, with direct interaction between SIRT2 and FOXO1. This interaction enhances insulin-stimulated phosphorylation of FOXO1, which in turn regulates FOXO1 nuclear and cytosolic localization. Thus, Sirt2 acts as an important regulator of adipocyte differentiation through modulation of FOXO1 acetylation/phosphorylation and activity and may play a role in controlling adipose tissue mass and function.     

PCR survey of hox genes in the goldfish Carassius auratus auratus

A tetraploidization event took place in the cyprinid lineage leading to goldfishes about 15 million years ago. A PCR survey for Hox genes in the goldfish Carassius auratus auratus (Actinopterygii: Cyprinidae) was performed to assess the consequences of this genome duplication. Not surprisingly, the genomic organization of the Hox gene clusters of goldfish is similar to that of the closely related zebrafish (Danio rerio). However, the goldfish exhibits a much larger number of recent pseudogenes, which are characterized by indels. These findings are consistent with the hypothesis that dosage effects cause selection pressure to rapidly silence crucial developmental regulators after a tetraploidization event.     

慢病毒介导的RNA干涉对乳腺癌SKBR3细胞HER2受体的下调及生长抑制

大约30％的乳腺癌中有表皮生长因子受体家族蛋白HER2的过表达,此类癌症的预后差,恶性程度高。RNA干涉（RNAi）是最近发展起来能特异性抑制哺乳动物细胞中基因表达的新技术。本文在以往获得的能够产生良好基因沉默效应的小干涉RNA（siRNA）的基础上,构建了U6和H1双启动子siRNA表达载体,并转染HER2高表达乳腺癌SKBR3细胞定量测定了其HER2下调效应。随后,siRNA表达盒经LR重组反应被克隆入慢病毒载体中,在成功包装成病毒后,感染SKBR3并经荧光定量PCR、蛋白印迹杂交和流式细胞仪一系列实验证明慢病毒介导的RNAi确实能有效地下调肿瘤抗原HER2的表达。细胞长期增殖实验表明经慢病毒处理后细胞生长得到抑制。我们的研究为进一步阐明HER2与癌症恶化的关系以及发展新的基因治疗药物提供了工具和可能。     

五爪金龙茎的解剖结构

运用常规石蜡切片、显微观察及显微照相的方法, 对五爪金龙( Ipomoea cairica) 茎的结构进行了观察研究, 结果表明: 五爪金龙茎的解剖结构以初生结构为主, 维管形成层已经形成, 但次生结构尚不发达。通常具3～6 个空腔, 初步推断其为裂生式分泌道; 表皮外弦向壁增厚, 具角质层, 具气孔及气室;紧贴表皮内方的1～3 层和皮层最内1～3 层的细胞可能为分泌细胞; 具双韧维管束, 木质部极为发达, 导管细胞紧密排列, 围绕内韧皮部和中央的髓而成一圆周; 形成层位于外韧皮部与木质部之间; 茎中央是大型薄壁细胞构成的髓, 具簇晶。     

Associations between daytime and nighttime plasma orexin A levels and cognitive function in patients with obstructive sleep apnea

Sleep and Biological Rhythms - The relationship between plasma orexin A (OXA) levels and cognitive function in patients with obstructive sleep apnea (OSA) remains unclear. This study aimed to...     

microRNA-140-5p from human umbilical cord mesenchymal stem cells–released exosomes suppresses preeclampsia development

Functional & Integrative Genomics - This work unraveled the action of human umbilical cord mesenchymal stem cells–released exosomes (huc-MSCs-EXO) transfer of miR-140-5p in preeclampsia...