大肠杆菌基因无痕敲除技术及策略

基因敲除技术是大肠杆菌基因组减小和代谢途径改造的有效手段,其中基于同源重组原理的基因无痕敲除技术显现出其他技术所不具备的应用优势和发展潜力。该技术可以快速敲除大肠杆菌基因组中的目标基因,并且在基因组中不残留任何外源片段,所以不会干扰后续的基因操作。我们分类介绍了无痕敲除技术中所涉及载体的结构、功能及其相应的敲除策略,着重介绍了无痕敲除技术的原理及载体构建方法。     

外源甜菜碱对黄瓜幼苗抗冷性的影响

以5 mmol·L-1甜菜碱(GB)根施黄瓜幼苗24h,可缓解低温胁迫[(6±1)℃]5 d后的叶中叶绿素含量的下降,保持相对较高的净光合速率和抗氧化酶活性,削弱丙二醛(MDA)积累,保持细胞膜的相对完整性,提高幼苗存活率.     

延髓腹外侧B(x)tzinger复合体呼吸时相转换效应的研究

实验在40只氨基甲酸乙酯麻醉的成年家兔上进行,观察电刺激Btzinger复合体(Bt.C)对呼吸节律的影响.结果表明: (1)吸气相早期短串电刺激Bt.C导致膈神经放电被短暂抑制,被抑制的程度与刺激强度呈正相关.当刺激落位在吸气相中、晚期时,可导致吸气提前终止("吸气切断"),之后跟随一缩短的呼气相.导致"吸气切断"的阈强度与刺激落位呈负相关.(2)呼气相短串电刺激Bt.C,可诱导膈神经短暂放电,呼气相晚期诱导出现放电之后往往跟随一正常的吸气放电,结果导致该呼气相缩短.该效应亦具有刺激强度、刺激落位依赖性.结果提示: Bt.C参与吸气向呼气以及呼气向吸气的时相转换.     

雷帕霉素的新靶点:溶酶体钙离子通道TRPML1

雷帕霉素(Rapamycin,Rap)是一种免疫抑制剂,在临床上主要应用于器官移植过程中的抗排异反应,同时,Rap在抗癌、神经保护和抗衰老等领域也展现出巨大潜力.通过抑制哺乳动物Rap靶蛋白(mammalian target of Rapamycin,mTOR)活性,Rap能够活化调节溶酶体功能的转录因子EB(tran...     

‘砀山酥梨’褐皮芽变中两个ERF基因的克隆与表达分析

为了解梨(Pyrus bretschneideri)中ERF基因的功能, 采用3'' RACE 和PCR 技术从‘砀山酥梨’中克隆了两个ERF基因, 并对其表达进行了分析。克隆的两个ERF基因都具有典型的AP2/ERF 结构域, 属于ERF基因家族, 分别命名为PbERF2 和PbERF4, GenBank 登录号分别为KJ623716 和KJ623718。系统进化分析表明, PbERF2 与枇杷ERF1, PbERF4 与黄瓜ERF1的亲缘关系较近。表达分析表明, PbERF2 和PbERF4 在叶片中几乎不表达, 果皮中的表达量高于果肉;‘锈酥’果皮3 个发育时期的PbERF2 和 PbERF4 表达量均显著高于‘砀山酥梨’, 且均呈现先上升后下降的趋势。这为深入研究梨ERF基因家族的作用机理提供了理论依据。     

心脏副交感节前神经元的研究进展

近年来,应用逆行荧光标记技术和膜片钳技术,对心脏副交感节前神经元(PCPNs)的研究取得很大进展。PCPNs不具有自主发放特性,其活动完全依赖于其突触前支配。PCPNs主要受胆碱能、兴奋性氨基酸能、GABA能及甘氨酸能支配;这些递质传递之间除相互作用外,还受多种神经肽及药物的影响。胆碱能递质对GABA能及甘氨酸能突触前支配的易化作用,参与生理性呼吸性窦性心律不齐的产生,其异常可能与多种心血管疾病发生有关。     

Monoclonal side population progenitors isolated from human fetal pancreas

The side population (SP) phenotype might represent a common molecular feature for a wide variety of stem cells. The aim of this study was to investigate whether monoclonal SP progenitor cells were established from human fetal pancreas. Islet-like cell clusters (ICCs) were isolated from human fetal pancreas. Monolayer epithelium-like cells were obtained from the ICCs and passaged thereafter. Single SP or non-SP cells were sorted from these cells at the sixth passage. The rate of clone formation was about 2.7% for the SP cells, whereas there was no clone formation for the non-SP cells. The SP cell clones were further expanded for more than 15 passages and induced for differentiation into cells with characteristics of pancreatic beta-cells. We show for the first time that the monoclonal SP progenitors are established from human fetal pancreas. Therefore, this study may offer a novel method to purify pancreatic progenitor cells from human tissues.     

Cytological identification of an isotetrasomic in rice and its application to centromere mapping

The aneuploid with isochromosome or telochromosome is ideal material for exploring the position of centromere in lingkage map.For obtaining these aneuploids in rice,the primary trisomics from triplo-1 to triplo-12 and the aneuploids derived from a triploid of indica rice variety Zhongxiao 3037 were carefully investigated.From the offsprings of triplo-10,a primary trisomic of chromosome 10 of the variety,an isotetrasomic “triplo-10-1” was obtained.Cytological investigation revealed that a pair of extra isochromosomes of triplo-10-1 were come from the short arm of chromosome 10.In the offsprings of the isotetrasomic,a secondary trisomic “triplo-10-2”,in which the extra-chromosome was an isochromosome derived from the short arm of chromosome 10,was identified.With the isotetrasomic,secondary trisomic,primary trisomic and diploid of variety Zhongxiao 3037,different molecular markers were used for exploring the position of the centromere of chromosome 10.Based on the DNA dosage effect,it was verified that the molecular markers G1125,G333 and L169 were Located on the short arm,G1084 and other 16 available molecular markers were on the long arm of chromosome 10.So the centromere of chromosome 10 was located somewhere between G1125 and G1084 according to the RFLP linkage map given by Kurata et al[1].The distance from G1125 to G1084 was about 3.2cM.     

The apoptosis of HEL cells induced by hydroxyurea

INTRODUCTIONApoptosis(programmedcelldeath)playsafundamentalroleduringinvertebrateandvertebratedevelopment.Theoriginofhumancancermaybeassociatedwiththefailureofendangeredcellstoundergoapoptosis.Apoptosishasbeenobservedinmanydifferentcellsandinresponsetomanyphysiologicalsignalsortypesofstress[1,2].Itcanbeinducedbyglucocorticoidtreatment,exposuretoCa2 ionophoresorac--irradiationofmousethymocytesandgrowthfactordeprivationofbothhematopoieticandlymphoidcellsinvitro[3,4].Hydroxyureacanstimulate…