Improvement of glycine biosynthesis from one-carbon compounds and ammonia catalyzed by the glycine cleavage system in vitro

Glycine cleavage system (GCS) plays a central role in one-carbon (C1) metabolism and receives increasing interest as a core part of the recently proposed reductive glycine pathway (rGlyP) for assimilation of CO₂ and formate. Despite decades of research, GCS has not yet been well understood and kinetic data are barely available. This is to a large degree because of the complexity of GCS, which is composed of four proteins (H, T, P, and L) and catalyzes reactions involving different substrates and cofactors. In vitro kinetics of reconstructed microbial multi-enzyme glycine cleavage/synthase system is desired to better implement rGlyP in microorganisms like Escherichia coli for the use of C1 resources. Here, we examined in vitro several factors that may affect the rate of glycine synthesis via the reverse GCS reaction. We found that the ratio of GCS component proteins has a direct influence on the rate of glycine synthesis, namely higher ratios of P protein and especially H protein to T and L proteins are favorable, and the carboxylation reaction catalyzed by P protein is a key step determining the glycine synthesis rate, whereas increasing the ratio of L protein to other GCS proteins does not have significant effect and the ratio of T protein to other GCS proteins should be kept low. The effect of substrate concentrations on glycine synthesis is quite complex, showing interdependence with the ratios of GCS component proteins. Furthermore, adding the reducing agent dithiothreitol to the reaction mixture not only results in great tolerance to high concentration of formaldehyde, but also increases the rate of glycine synthesis, probably due to its functions in activating P protein and taking up the role of L protein in the non-enzymatic reduction of H_ox to H_red. Moreover, the presence of some monovalent and divalent metal ions can have either positive or negative effect on the rate of glycine synthesis, depending on their type and their concentration.     

青冈常绿阔叶林内的小气候特征

分析我国中亚热带东部青冈（Ｑｕｅｒｃｕｓｇｌａｕｃａ）常绿阔叶林内的小气候特征,１９９３～１９９５年的研究结果表明：①到达青冈林的总太阳辐射为３３４４７８０ｋＪ／（ｍ２·ａ）,四季中群落的反射率、透射率和吸收率分别为１６％～２２％、９％～１２％和６７％～７４％。②林冠外上方及群落上层气温在白天高于群落下层,夜间低于群落下层,可相差３～５℃,夏季差异最大。③林内外空气相对湿度的日动态呈“Ｕ”型变化,林内夜间湿度高达９０％左右,午间较低,在５０％左右。在四季的晴天中,林冠上方的空气相对湿度均低于林内,相差５％～２２％,夏季和冬季差异最大。④林中的ＣＯ２浓度在林冠层最低,近地面层最高,各季节始终低于林外,其中夏、秋两季最明显。⑤在春、夏、秋３季中,土壤温度为白天高于夜间,而冬季则为夜间高于白天;土壤湿度以冬、春季较高（３１．９％和２８．５％）,夏季最低（１４．２％）。由于青冈次生林的叶面积指数较小,群落结构较简单,因而整个群落的透光系数较大,群落内外空气温湿度的差异也较小,体现出幼年林向中年林过渡阶段的特点     

Effects of 2-Deoxy-d-Glucose on Methamphetamine-Induced Dopamine and Serotonin Neurotoxicity

Abstract: The mechanisms underlying the neurotoxic actions of methamphetamine (METH) and related substituted amphetamines are unknown. Previous studies with 2-deoxyglucose (2-DG) have suggested that METH-induced neurotoxicity may involve exhaustion of intracellular energy stores. However, because 2-DG also produces hypothermic effects, and because METH's neurotoxic actions are highly susceptible to thermoregulatory influence, previous findings with 2-DG are difficult to interpret. The present studies were undertaken to further examine the influence of 2-DG's glucoprivic and thermic effects in the context of METH-induced dopamine (DA) and serotonin (5-HT) neurotoxicity. 2-DG protected against METH-induced DA neurotoxicity in both rats and mice. In both species, 2-DG, alone or in combination with METH, produced hypothermic effects. METH's toxic effects on brain 5-HT neurons were either unaffected or exacerbated by 2-DG, depending on species, brain region, and dose of METH tested. These results indicate that different mechanisms may underlie METH-induced DA and 5-HT neurotoxicity, and suggest that, as compared with 5-HT neurons, DA neurons are more susceptible to temperature influence, whereas 5-HT neurons are more vulnerable than DA neurons to metabolic compromise. Additional studies are needed to further assess the role of energy stores in the neurotoxic effects of METH and related drugs.     

Role of mass spectrometry in the purification of peptides and proteins

Experiments were carried out to evaluate the fractionation of proteins and peptides according to mass. Model mixtures were separated by either reversed-phase or ion-exchange chromatography with mass spectrometry-compatible mobile phase additives. Fraction collection was triggered by the mass/charge ratio of each one of the components of the mixture. Chromatography was additionally monitored with a UV-Vis detector in order to compare the new technique with generally accepted in separations. The results indicated that adequate purification is achieved by this new technique. Fraction collection triggered by changes in the mass/charge ratio reduces sample handling and analysis time. This study demonstrates the utility of mass-directed fractionation of peptides and proteins when mass spectrometry-compatible mobile phase additives are used.     

Estrogen signals via an extra-nuclear pathway involving IGF-1R and EGFR in tamoxifen-sensitive and -resistant breast cancer cells

Activation of IGF-1R can activate metalloproteinases which release heparin-binding EGF (Hb-EGF) and lead to EGFR-dependent MAPK activation in certain tissues. We postulated that this pathway is operative in E₂-induced MAPK activation in breast cancer tissues. As evidence, we showed that E₂ rapidly induced the phosphorylation of both IGF-1R and EGFR and that siRNA knockdown or selective inhibitors against either growth factor receptor inhibited E₂-induced MAPK activation. The selective inhibitors or knockdown of either IGF-1R or EGFR significantly inhibited cell growth and reversed cell death protection induced by E₂ in MCF-7 cells. Our data support the conclusion that the IGF-1R acts upstream of EGFR in a linear pathway which mediates E₂ action on MAPK activation, cell growth stimulation and anti-apoptosis in breast cancer cells. During the process of development of tamoxifen resistance this pathway is up-regulated with increased sensitivity to activate EGFR for cell growth and protection against apoptosis. Surprisingly, translocation of ERα out of the nucleus into the cytoplasm, mediated by c-Src, occurs during development of resistance. This effect can be abrogated by administration of the c-Src inhibitor, PP2 which also restores sensitivity to tamoxifen.     

植原体的最新分类研究动态

简要介绍了植原体分类研究历史与现状, 综述了最新的植原体分类方法和植原体候选种的描述规则, 指出了我国在植原体分类鉴定方面与当今世界先进水平的差距及今后发展方向。     

中国实蝇检疫研究概况

实蝇（fruit fly）是为害水果和蔬菜的有害生物,这类害虫尤其是在果蔬的国际贸易中受到关注,多将其列为检疫性有害生物而置于有关的法规中。本文从应用于植物检疫的角度,着重就实蝇的监测和有关生物学的研究、实蝇鉴定技术研究、实蝇除害处理研究、建立实蝇非疫区、果园实蝇防治研究以及我国在水果国际双边贸易中的实蝇问题等多个方面的内容收集和介绍有关研究概况,对我国就以实蝇为内容的研究提供相关信息。     

Combined Strategy of Endothelial Cells Coating,Sertoli Cells Coculture and Infusion Improves Vascularization and Rejection Protection of Islet Graft

Improving islet graft revascularization and inhibiting rejection become crucial tasks for prolonging islet graft survival. Endothelial cells (ECs) are the basis of islet vascularization and Sertoli cells (SCs) have the talent to provide nutritional support and exert immunosuppressive effects. We construct a combined strategy of ECs coating in the presence of nutritious and immune factors supplied by SCs in a co-culture system to investigate the effect of vascularization and rejection inhibition for islet graft. In vivo, the combined strategy improved the survival and vascularization as well as inhibited lymphocytes and inflammatory cytokines. In vitro, we found the combinatorial strategy improved the function of islets and the effect of ECs-coating on islets. Combined strategy treated islets revealed higher levels of anti-apoptotic signal molecules (Bcl-2 and HSP-32), survival and function related molecules (PDX-1, Ki-67, ERK1/2 and Akt ) and demonstrated increased vascular endothelial growth factor receptor 2 (KDR) and angiogenesis signal molecules (FAk and PLC-γ). SCs effectively inhibited the activation of lymphocyte stimulated by islets and ECs. Predominantly immunosuppressive cytokines could be detected in culture supernatants of the SCs coculture group. These results suggest that ECs-coating and Sertoli cells co-culture or infusion synergistically enhance islet survival and function after transplantation.     

Ultra‐sensitive fluorescent sensor for intracellular miRNA based on enzyme‐free signal amplification with carbon nitride nanosheet as a carrier

A novel ultra‐sensitive fluorescent sensor for monitoring microRNA (miRNA) in living cells was constructed by utilizing a hybridization chain reaction (HCR) as the signal amplification with a carbon nitride nanosheet (CNNS) as a carrier. The Cy5‐labeled hairpin DNA could be adsorbed onto the surface of CNNS, resulting in fluorescence quenching of Cy5. When treated with complementary miRNA, the fluorescence was recovered because miRNA could efficiently trigger an HCR, which led to the release of the HCR products from the CNNS. This intracellular HCR strategy can be used for ultra‐sensitive monitoring of intracellular miRNA. The main advantages of the proposed method are its simplicity, high sensitivity, high specificity and low toxicity for monitoring low‐level biomarkers.     

高效降解甲醛菌株的分离鉴定及其特性

首先对新分离的、能高效降解甲醛的两菌株A1和A2在形态学特征、生理生化特性及16S rDNA序列分析等方面进行了系统研究; 随后通过测定在液体培养过程中甲醛浓度的变化, 确定新分离菌株A1、A2降解溶液中甲醛的性能; 最后利用菌株A1、A2分别进行生物填料塔的挂膜实验, 确定其对甲醛气体的净化性能。结果表明: 菌株A1属于假单胞菌属(Pseudomonas), 菌株A2为鞘氨醇单胞菌属(Sphingomonas); 当甲醛初始浓度<1 200 mg/L时,菌株A1、A2都能完全降解溶液中的甲醛, 当甲醛浓度增高至1 600 mg/L时, 菌株A1在48 h后的甲醛降解率为50%, 菌株A2在104 h后的甲醛降解率为74.3%; 菌株A1、A2对甲醛气体的净化效率均能达到99%以上, 菌株A1的甲醛生化去除量能达到26.4 mg/(L?h), 菌株A2的甲醛生化去除量可达20.6 mg/(L?h)。