Tenascin-R distinct domains modulate migration of neural stem/progenitor cells in vitro

Extracellular matrix (ECM) molecules constitute a "niche" that modulates the migration, proliferation, and differentiation of neural stem/progenitor cells (NSPCs). The glycoprotein Tenascin-R (TN-R) is an ECM molecule, comprising multiple domains. Either the whole TN-R molecule or its distinct domains has been demonstrated to play a very important role in the developing central nervous system. However, little is known about the effect of the TN-R domain on NSPCs, especially NSPC migration. In the present study, we first show that both TN-R domains epidermal growth factor-like repeat (EGFL) and fibronectin type III (FN)6-8 can inhibit the NSPCs migration from neurospheres in vitro. Furthermore, both the EGFL and FN6-8 domains affect the distribution of neurons generated from neurospheres, indicating that EGFL and FN6-8 domains inhibit the motility of neurons generated from neurospheres. These results suggest that TN-R has an inhibitory effect on NSPCs migration.     

Improvement of xylose utilization in Clostridium acetobutylicum via expression of the talA gene encoding transaldolase from Escherichia coli

Clostridium acetobutylicum ATCC 824 was metabolically engineered for improved xylose utilization. The gene talA, which encodes transaldolase from Escherichia coli K-12, was cloned and overexpressed in C. acetobutylicum ATCC 824. Compared with C. acetobutylicum ATCC 824 (824-WT), the transformant bearing the E. coli talA gene (824-TAL) showed improved ability on xylose utilization and solvents production using xylose as the sole carbon source. During the fermentation of xylose and glucose mixtures with three xylose/glucose ratios (approximately 1:2, 1:1 and 2:1), the rate of xylose consumption and final solvents titers of 824-TAL were all higher than those of 824-WT, despite glucose repression on xylose uptake still existing. These results suggest that the insufficiency of transaldolase in the pentose phosphate pathway (PPP) of C. acetobutylicum is one of the bottlenecks for xylose metabolism and therefore, overexpressing the gene encoding transaldolase is able to improve xylose utilization and solvent production.     

基于近红外漫反射光谱快速测定淫羊藿蛋白质含量

采用近红外漫反射光谱技术对淫羊藿(Epimedium)的蛋白质含量进行快速且无损检测。近红外漫反射光谱经二阶导数处理、标准多元离散校正及主成分分析聚类处理后, 采用改进最小二乘法回归得到的定标模型预测效果最佳, 定标决定系数、交互验证标准差及交互验证相关系数分别为0.923、0.554和0.717。近红外光谱分析法的测定结果与用凯氏定氮法所得结果无显著差异, 两种方法测定值的相关性较高(R²=0.933 9)。重复性实验表明, 近红外光谱分析法的相对标准偏差为0.937%。该研究首次采用近红外光谱分析法测定了8种淫羊藿的蛋白质含量。该方法简便、精确, 在淫羊藿资源开发利用和药材质量控制方面具有参考意义。     

Conditioned medium from hypoxia-treated adipocytes renders muscle cells insulin resistant

Adipose tissue hypoxia is an early phenotype in obesity, associated with macrophage infiltration and local inflammation. Here we test the hypothesis that adipocytes in culture respond to a hypoxic environment with the release of pro-inflammatory factors that stimulate macrophage migration and cause muscle insulin resistance. 3T3-L1 adipocytes cultured in a 1% O2 atmosphere responded with a classic hypoxia response by elevating protein expression of HIF-1α. This was associated with elevated mRNA expression and peptide release of cytokines TNFα, IL-6 and the chemokine monocyte chemoattractant protein-1 (MCP-1). The mRNA and protein expression of the anti-inflammatory adipokine adiponectin was reduced. Conditioned medium from hypoxia-treated adipocytes (CM-H), inhibited insulin-stimulated and raised basal cell surface levels of GLUT4myc stably expressed in C2C12 myotubes. Insulin stimulation of Akt and AS160 phosphorylation, key regulators of GLUT4myc exocytosis, was markedly impaired. CM-H also caused activation of JNK and S6K, and elevated serine phosphorylation of IRS1 in the C2C12 myotubes. These effects were implicated in reducing propagation of insulin signaling to Akt and AS160. Heat inactivation of CM-H reversed its dual effects on GLUT4myc traffic in muscle cells. Interestingly, antibody-mediated neutralization of IL-6 in CM-H lowered its effect on both the basal and insulin-stimulated cell surface GLUT4myc compared to unmodified CM-H. IL-6 may have regulated GLUT4myc traffic through its action on AMPK. Additionally, antibody-mediated neutralization of MCP-1 partly reversed the inhibition of insulin-stimulated GLUT4myc exocytosis caused by unmodified CM-H. In Transwell co-culture, hypoxia-challenged adipocytes attracted RAW 264.7 macrophages, consistent with elevated release of MCP-1 from adipocytes during hypoxia. Neutralization of MCP-1 in adipocyte CM-H prevented macrophage migration towards it and partly reversed the effect of CM-H on insulin response in muscle cells. We conclude that adipose tissue hypoxia may be an important trigger of its inflammatory response observed in obesity, and the elevated chemokine MCP-1 may contribute to increased macrophage migration towards adipose tissue and subsequent decreased insulin responsiveness of glucose uptake in muscle.     

Oxidative stress-resistance assay for screening yeast strains overproducing heterologous proteins

Many natural proteins have been developed into drugs and produced for direct application. Identifying improved hosts to achieve high-level heterologous protein production is a challenge in the study of heterologous protein expression in recombinant yeast. In this study, a novel high-throughput assay to screen such overproducing Saccharomyces cerevisiae strains was systematically developed. The protocol designed was based on screening host strain derivatives with increased superoxide dismutase dependent resistance to oxidative stress. Yeast cells transformed with recombinant plasmid carrying SOD1 gene as a reporter responded exquisitely to oxidative stress induced by elevated concentrations of paraquat. Improved yeast strains resulting from screening clones subjected to genome shuffling through selective pressure argue for a more effective screening system compared with traditonal selection. Moreover, this approach can be employed in general biochemical analysis without utilization of flow cytometry or well plate reader. Therefore, it is expected that the high-throughput assay would make superior strains producing heterologous proteins.     

Development and application of photoautotrophic micropropagation plant system

Research has revealed that most chlorophyllous explants/plants in vitro have the ability to grow photoautotrophically (without sugar in the culture medium), and that the low or negative net photosynthetic rate of plants in vitro is not due to poor photosynthetic ability, but to the low CO₂ concentration in the air-tight culture vessel during the photoperiod. Moreover, numerous studies have been conducted on improving the in vitro environment and investigating its effects on growth and development of cultures/plantlets on nearly 50 species since the concept of photoautotrophic micropropagation was developed more than two decades ago. These studies indicate that the photoautotrophic growth in vitro of many plant species can be significantly promoted by increasing the CO₂ concentration and light intensity in the vessel, by decreasing the relative humidity in the vessel, and by using a fibrous or porous supporting material with high air porosity instead of gelling agents such as agar. This paper reviews the development and characteristics of photoautotrophic micropropagation systems and the effects of environmental conditions on the growth and development of the plantlets. The commercial applications and the perspective of photoautotrophic micropropagation systems are discussed.     

Elastin-like polypeptide and γ-zein fusions significantly increase recombinant protein accumulation in soybean seeds

Transgenic Research - Soybean seeds are an ideal host for the production of recombinant proteins because of their high content of proteins, long-term stability of seed proteins under ambient...     

A chloride efflux transporter,BIG RICE GRAIN 1, is involved in mediating grain size and salt tolerance in rice

Grain size is determined by the size and number of cells in the grain. The regulation of grain size is crucial for improving crop yield; however, the genes and molecular mechanisms that control grain size remain elusive. Here, we report that a member of the detoxification efflux carrier /Multidrug and Toxic Compound Extrusion (DTX/MATE) family transporters, BIG RICE GRAIN 1 (BIRG1), negatively influences grain size in rice (Oryza sativa L.). BIRG1 is highly expressed in reproductive organs and roots. In birg1 grain, the outer parenchyma layer cells of spikelet hulls are larger than in wild-type (WT) grains, but the cell number is unaltered. When expressed in Xenopus laevis oocytes, BIRG1 exhibits chloride efflux activity. Consistent with this role of BIRG1, the birg1 mutant shows reduced tolerance to salt stress at a toxic chloride level. Moreover, grains from birg1 plants contain a higher level of chloride than those of WT plants when grown under normal paddy field conditions, and the roots of birg1 accumulate more chloride than those of WT under saline conditions. Collectively, the data suggest that BIRG1 in rice functions as a chloride efflux transporter that is involved in mediating grain size and salt tolerance by controlling chloride homeostasis.