低聚木糖分离纯化的研究进展

综述了低聚木糖分离纯化的研究进展。低聚木糖是一种非消化性寡糖 ,能选择性增殖肠道内双歧杆菌 ,可广泛应用于食品工业和饲料工业。低聚木糖的分离纯化技术主要包括层析分离技术 (包括凝胶过滤层析、离子交换层析和吸附层析 )和膜分离技术 (包括超滤、纳滤和反渗透 )。低聚木糖的提纯主要采用膜分离技术和层析分离技术 ,低聚木糖单一组分的分离主要采用凝胶过滤层析和吸附层析     

钾肥及与秸秆配施对紫色土作物产量和微生物群落结构的影响

基于紫色菜园土壤莴笋-白菜-甜玉米轮作4年12季连续定位施钾肥试验,研究不同种类钾肥及用量对重庆地区紫色菜园土上作物产量和土壤微生物群落结构的影响,为该地区作物生产确定合理的施钾技术提供科学依据。结果表明,在施用氮磷肥基础上,不同钾肥处理莴笋、白菜、甜玉米产量均显著提高;从3种作物4年平均产量和钾肥效益看,以单施适量化学钾(K_2)、单施适量秸秆钾(M_2)和秸秆还田配施少量化学钾(K_1+M_1)的施钾肥模式对白菜的增产效果好,增产28.05%—30.27%;M_2和K_1+M_1施钾肥模式对莴笋的增产效果较好,增产13.89%和13.81%;K_1+M_1施钾肥模式对甜玉米的增产效果最好,增产15.10%,表明秸秆还田配施少量化学钾(K_1+M_1)模式在供试3种作物生产中具有很好的应用前景。不同施钾处理对土壤微生物群落结构及丰度均会产生一定影响,以秸秆还田配施少量化学钾肥(K_1+M_1)对提高土壤细菌、真菌、革兰氏阳性菌的作用较好,并显著增加土壤微生物总PLFA含量,缓解对土壤微生物生存环境的胁迫,说明K_1+M_1能为土壤微生物的生长繁育创造有利环境。莴笋、白菜、甜玉米3种作物4年平均产量与土壤细菌、真菌、革兰氏阳性菌和革兰氏阴性菌数量间存在显著相关性(P0.05),而不同钾肥处理对土壤微生物特征具有一定影响,说明施钾肥可能会调节土壤微生物特征,从而促进作物增产。     

Effects of size,neighbors, and site condition on tree growth in a subtropical evergreen and deciduous broad‐leaved mixed forest,China

Successful growth of a tree is the result of combined effects of biotic and abiotic factors. It is important to understand how biotic and abiotic factors affect changes in forest structure and dynamics under environmental fluctuations. In this study, we explored the effects of initial size [diameter at breast height (DBH)], neighborhood competition, and site condition on tree growth, based on a 3‐year monitoring of tree growth rate in a permanent plot (120 × 80 m) of montane Fagus engleriana–Cyclobalanopsis multiervis mixed forest on Mt. Shennongjia, China. We measured DBH increments every 6 months from October 2011 to October 2014 by field‐made dendrometers and calculated the mean annual growth rate over the 3 years for each individual tree. We also measured and calculated twelve soil properties and five topographic variables for 384 grids of 5 × 5 m. We defined two distance‐dependent neighborhood competition indices with and without considerations of phylogenetic relatedness between trees and tested for significant differences in growth rates among functional groups. On average, trees in this mixed montane forest grew 0.07 cm year^?1 in DBH. Deciduous, canopy, and early‐successional species grew faster than evergreen, small‐statured, and late‐successional species, respectively. Growth rates increased with initial DBH, but were not significantly related to neighborhood competition and site condition for overall trees. Phylogenetic relatedness between trees did not influence the neighborhood competition. Different factors were found to influence tree growth rates of different functional groups: Initial DBH was the dominant factor for all tree groups; neighborhood competition within 5 m radius decreased growth rates of evergreen trees; and site condition tended to be more related to growth rates of fast‐growing trees (deciduous, canopy, pioneer, and early‐successional species) than the slow‐growing trees (evergreen, understory, and late‐successional species).     

Thermal response in murine L929 cells lacking αB-crystallin expression and αB-crystallin expressing L929 transfectants

We investigated the role of B-crystallin expression in the development of thermotolerance in murine L929 cells. An initial heat-shock of 10 min at 45°C induced thermotolerance in these cells to a heat challenge at 45°C administered 24 h later. The thermotolerance ratio at 10^–1 isosurvival was 1.7. Expression of B-crystallin gene was not detected during the 24 h incubation at 37°C following heat shock by either northern or western blots. In contrast, inducible HSP70 synthesis was observed during this time period. Thus, this cell line provided an unique system in which to examine the effects of transfected B-crystallin on thermoresistance and thermotolerance. Cells stably transfected with B-crystallin under the control of an inducible promoter did not show a significant increase in the ability to develop thermotolerance. However, a stably transfected L929 clone expressing high levels of constitutive B-crystallin exhibited an approximately 50% increase in thermal resistance over parental and control cells. Though expression of B-crystallin is not requisite for the development of thermotolerance in L929 cells, overexpression of transfected B-crystallin can contribute to increased thermoresistance.     

上海市首例输入性甲型H1N1流行性感冒报道

甲型H1N1流行性感冒(简称流感)是由一种新型流感病毒引起的急性呼吸道传染性疾病。临床主要表现为流感样症状,包括发热、流涕、咽痛、咳嗽、头痛、腹泻等。奥司他韦和扎那米韦治疗甲型H1N1流感有效。本文报道上海市首例输入性甲型H1N1流感病例,以提高临床医生对这种新发流感的认识。     

太湖湖滨生态修复区大型底栖动物群落结构及梯度分布

2010—2011年对太湖贡湖湾湖滨带生态修复区滨岸挺水植物带(Ⅰ)、湾相沉水植物带(Ⅱ)和堰外开敞水体(Ⅲ)3个滨岸生境梯度带的水质状况和底栖动物群落特征进行了研究。结果表明:调查共发现底栖动物13科18种,其中仅出现于1个生境梯度带的物种7个;在其余的11个物种中,有5个种群的密度在生境梯度带间存在显著差异;比较发现,按底栖动物摄食功能类群的相对比例,刮食者相对丰度在带Ⅰ最高,收集者在带Ⅱ最高,滤食者在带Ⅲ最高,不同生境梯度带间底栖动物的摄食功能类群构成存在显著差异。对底栖动物相对丰度和水环境参数的冗余分析显示,环节动物和昆虫与DO、NO3--N和PO43--P浓度正相关,软体动物则与NO3--N和PO43--P负相关,一些腹足类对低DO耐受能力较强,与NH4+-N和COD正相关。修复区3个梯度带水动力条件、水质状况和底质类型的差异性对底栖动物的分布有重要影响,形成了生活习性、摄食特征等显著不同的3个底栖动物群落。     

FoxO转录因子

FoxO家族是转录调节因子 ,也是INS IGF 1信号通路中的关键分子。FoxO基因在进化上高度保守 ,其氨基酸序列中含有 3个高度保守PKB磷酸化基序。FoxO受PI3K PKB磷酸化级联通路的调节 ,其活性与磷酸化状态直接相关。FoxO对细胞增殖、细胞凋亡等生理过程有重要调节作用 ,并可能在免疫系统发育中对免疫细胞的凋亡及亚群间的平衡起一定调节作用。     

A novel carbonyl reductase from Pichia stipitis for the production of ethyl (S)-4-chloro-3-hydroxybutanoate

An NADPH-dependent carbonyl reductase (PsCR) gene from Pichia stipitis was cloned. It contains an open reading frame of 849 bp encoding 283 amino acids whose sequence had less than 60% identity to known reductases that produce ethyl (S)-4-chloro-3-hydroxybutanoates (S-CHBE). When expressed in Escherichia coli, the recombinant PsCR exhibited an activity of 27 U/mg using ethyl 4-chloro-3-oxobutanoate (COBE) as a substrate. Reduction of COBE to (S)-CHBE by transformants in an aqueous mono-phase system for 18 h, gave a molar yield of 94% and an optical purity of the (S)-isomer of more than 99% enantiomeric excess.     

三氟氯氰菊酯对棉铃虫神经细胞延迟整流钾电流的抑制作用

用膜片钳技术首次研究了三氟氯氰菊酯对离体培养的棉铃虫中枢神经细胞延迟整流钾通道电流的影响。结果表明,药物作用前有81%和39%的细胞的通道分别在-30 mV 和 -40 mV 激活（n=21）。三氟氯氰菊酯（10^-5 mmol/L）作用15 min后,有63%和38%细胞的通道分别在-40 mV 和 -50 mV 激活（n=8）;作用1 min后电流幅值明显降低,抑制率达到了37.7%（n=19）;加药后激活曲线明显左移且Vh 值变化显著,但k值没有明显变化。实验结果说明,三氟氯氰菊酯作用后,通道更容易激活,但显著抑制电流峰值,导致神经敏感性降低,棉铃虫中枢神经细胞钾通道也是拟除虫菊酯类药物的作用靶标之一。