EGF对大鼠卵巢颗粒细胞增殖与分化影响的研究

许多研究发现,表皮生长因子(EGF)对生殖功能有重要的调节作用。本文用体外细胞培养的方法,研究了EGF对大鼠卵巢颗粒细胞增殖与分化的影响及其作用方式。结果如下:EGF可以明显抑制颗粒细胞DNA的合成,但促进孕酮的生成,后者是因为EGF能显著提高细胞内3β-羟甾脱氨酶(3β-HSD)的活性。放射受体分析表明,颗粒细胞上存在EGF的特异性受体,其K_d为1.83±0.3×10~(-8)mol/L,B_(max)为1.75±0.29×10~4个位点/细胞。卵巢免疫组化结果未发现颗粒细胞有EGF样免疫染色,而卵泡膜、黄体及间质内等均有阳性染色。以上结果提示,EGF可能通过旁分泌机制作用于颗粒细胞的EGF受体,从而调节细胞的生长和性激素的分泌,这对于颗粒细胞的成熟及卵泡的发育有着重要意义。     

红细胞抗高血压因子降压作用的进一步研究

我们曾报道原发性高血压患者(EHS)红细胞抗高血压因子(AHF)具有缓慢而持久的降压作用。本工作表明,AHF对卒中易感型自发性高血压大鼠(SHRsp)还具有快速短暂的降压作用,注射AHF后10—30s,SHRsp收缩压从原水平的26.8±1.7kPa降至20.1±1.5kPa(P<0.001)。正常人和大鼠红细胞AHF的降压作用明显强于EHS和高血压大鼠AHF。此外我们还发现EHS血浆中存在升压物质。以上结果提示,AHF缺乏和升压物质含量相对较高可能是原发性高血压发病的一个重要原因。     

微生物互营产甲烷过程中的种间电子传递

甲烷作为全球第二大温室气体,是典型的可再生清洁能源,也是碳循环中的重要物质组成。大气中约74%的甲烷由产甲烷古菌和其他微生物的互营产生,种间电子传递(interspecies electron transfer, IET)是微生物菌群降低热力学能垒、实现互营产甲烷的核心过程。IET可分为间接种间电子传递(mediated interspecies electron transfer,MIET)和直接种间电子传递(direct interspecies electron transfer, DIET)两种类型,其中MIET依赖氢气、甲酸等载体完成电子的远距离传输,而DIET则依赖导电菌毛、细胞色素c等膜蛋白,通过微生物的直接接触实现电子传递。本文将从IET的研究历程出发,从电子传递机制、微生物种类、生态多样性等方面对微生物互营产甲烷过程中的两种IET类型进行比较,最后对未来待探索的方向进行展望。本综述有助于加深对微生物互营产甲烷过程中IET的理解,为解决由甲烷引发的全球气候变暖等生态问题提供理论支撑。     

核酸去甲基酶AlkB在毕赤酵母中的表达纯化及在tRNA相关研究中的应用

[目的]核酸的甲基化修饰是一种常见的化学修饰形式,具有重要的生物学功能,却也在一定程度上给一些核酸研究过程带来了技术难度。tRNA上具有的大量甲基化修饰会阻碍逆转录进程,从而降低荧光定量PCR (real-time fluorescence quantitative polymerase chain reaction,RT-qPCR)和高通量测序对其的检测效率。来自大肠杆菌(Escherichia coli)的AlkB蛋白是一种多功能的脱烷基化酶,可以去除DNA和RNA上多种甲基化为代表的修饰,有望解决以上问题。[方法]针对大肠杆菌来源的AlkB,分别尝试在大肠杆菌和毕赤酵母(Pichia pastoris)表达系统中进行诱导表达和纯化,对纯化获得的AlkB进行酶学性质测定。最后以tRNA_UAU^Ile等两种tRNA为代表,研究AlkB的处理对于荧光定量PCR法检测tRNA表达水平的影响。[结果]AlkB在大肠杆菌中表达时多以包涵体形式存在,但是在毕赤酵母中可以成功分泌表达。使用镍柱分离纯化后获得了纯度高于95%的AlkB蛋白,其酶学性质参数如...     

枯草芽孢杆菌聚谷氨酸合成途径相关基因功能研究

聚谷氨酸(polyglutamic acid, PGA)作为一种天然多功能的聚合物,近年来成为研究的热点。由于很难通过化学方法合成,微生物发酵是目前生产聚谷氨酸的有效途径。【目的】从基因水平探究枯草芽孢杆菌聚谷氨酸合成途径中degS、degQ、degU、swrA、rocA、putM基因的功能,通过分子改造实现对代谢途径的调控。【方法】以枯草芽孢杆菌为出发菌株,通过对代谢途径中相关基因进行敲除或过表达,分别构建degS、degQ和degU基因缺失的重组菌,swrA、rocA和putM基因过表达的重组菌,借助菌株胞外聚谷氨酸积累的变化分析影响途径的关键节点。【结果】在摇瓶发酵条件下,重组菌Bacillus subtilis 168-swrA、Bacillus subtilis 168-rocA、Bacillus subtilis 168-putM的胞外聚谷氨酸含量分别是原始菌株的1.28倍、1.47倍和1.37倍。重组菌Bacillus subtilis 168-ΔdegS、Bacillus subtilis 168-ΔdegQ、Bacillus subtilis 168-ΔdegU的胞外...     

Fine-scale mapping of physicochemical and microbial landscapes of the coral skeleton

The coral skeleton harbours a diverse community of bacteria and microeukaryotes exposed to light, O₂ and pH gradients, but how such physicochemical gradients affect the coral skeleton microbiome remains unclear. In this study, we employed chemical imaging of O₂ and pH, hyperspectral reflectance imaging and spatially resolved taxonomic and inferred functional microbiome characterization to explore links between the skeleton microenvironment and microbiome in the reef-building corals Porites lutea and Paragoniastrea benhami. The physicochemical environment was more stable in the deep skeleton, and the diversity and evenness of the bacterial community increased with skeletal depth, suggesting that the microbiome was stratified along the physicochemical gradients. The bulk of the coral skeleton was in a low O₂ habitat, whereas pH varied from pH 6–9 with depth. Physicochemical gradients of O₂ and pH of the coral skeleton explained the β-diversity of the bacterial communities, and skeletal layers that showed O₂ peaks had a higher relative abundance of endolithic algae, reflecting a link between the abiotic environment and the microbiome composition. Our study links the physicochemical, microbial and functional landscapes of the coral skeleton and provides new insights into the involvement of skeletal microbes in the coral holobiont metabolism.     

Self-assembly of molecular beacons through metal ion coordination for fluorescence imaging of miRNA in living cells

Fluorescence nanosensors based on functional nucleic acids have been explored as a powerful sensing platform for disease-relevant miRNAs. This work developed a new hybrid nanosensor (Zr-B) through coordination-driven self-assembly of Zr ions and beacons. The prepared nanosensor exhibited high loading efficiency of beacons and could achieve sensitive and specific detection for miRNAs. The hybrid nanosensor could transfer beacons into living cells efficiently and maintain high stability and biocompatibility in the biological environment, achieving effective miRNA fluorescence imaging in living cells. Therefore, the resultant nanosensor holds potential for applications in disease diagnostics.     

Multistimuli-responsive fluorescence behaviours of aggregation-induced emission small-molecule and electrospun nanofibre films for acid–base vapour sensing

Multistimuli-responsive fluorescent materials have garnered great research interest benefited from their practical applications. Two twisted-structure compounds containing tetraphenylethylene (TPE) as the aggregation-induced emission (AIE) group and a pyridine unit as the acid reaction site to obtain new multistimuli-responsive fluorescent compounds (namely, TPECNPy: TPECNPy-2 and TPECNPy-3) were successfully synthesized through a one-step Knoevenagel condensation reaction. The multiple-stimuli response process of TPECNPy was investigated by means of photoluminescence (PL) spectra and emission colour. The results showed that both TPECNPy compounds with excellent AIE abilities displayed reversible emission wavelength and colour changes in response to multiple external stimuli, including grinding–fuming by CH₂Cl₂ or annealing and HCl-NH₃ vapour fuming. More importantly, fluorescent nanofibre films were prepared by electrospinning a solution of TPECNPy mixed with cellulose acetate (CA), and these exhibited reversible acid-induced discolouration, even with only 1 wt% TPECNPy. The results of this study may inspire strategies for designing multistimuli-responsive materials and preparing fluorescent sensing nanofibre films.     

花生种子萌发早期胚轴细胞DNA合成的特点

花生种子吸胀6h后胚轴DNA中有~3H-胸苷掺入。咖啡因和羟基脲均对6～12h的~3H—胸苷掺入具强烈的抑制作用;当12～24h时,咖啡因的抑制作用较大;但30h以后,羟基脲的抑制作用超过咖啡因。双链DNA放射性从种子吸胀9h后迅速上升,单链DNA放射性在吸胀12h后出现一个明显的峰。但在吸胀12h后,单链DNA形成和存在的时间是短暂的。     

烟草耐盐愈伤组织变异体对盐渍的适应性

用组织培养及逐步增加,NaCl浓度的方法,筛选出烟草耐盐愈伤组织变异体。能耐盐(2％ NaCl)的愈伤组织在2％ NaCl中继代29次,再移入无盐培养基中培养11和20代后不能保持提高的耐盐性,分别退化到只耐1.5％与1.0％ NaCl的水平。耐2％ NaCl愈伤组织产生的再生植株自交后代,其萌发种子、幼苗及成长植株均未能表现出耐盐性,说明用选择胁迫方法所筛选出的耐盐细胞系,其耐盐性的提高属于生理适应性。