944 resultados para Synaptic Vesicle Endocytosis
Resumo:
A rhabdovirus was found to be associated with a lethal hemorrhagic disease in the cultured Chinese sucker Myxocyprinus asiaticus Bleeker. The rhabdovirus was amplified and isolated from the infected GCO, (grass carp ovary) cells. In ultrathin sections of liver cells from the diseased fish, the virus particles exhibited the characteristic bacilliform morphology, and budded through vesicle membranes of the infected cells. The isolated rhabdovirus particles were found to have a bacilliform morphology with 2 rounded ends rather than a typical flat base. The virus particles were measured and ranged in size from 150 to 200 nm in length and 50 to 60 nm in diameter. Most other characteristics, including their size, extensive virus infectivity to fish cell Lines, strong cytopathogenic effects, stability at high temperatures, vesicle formation in infected cells, structure protein electrophoretic patterns and the presence of an RNA genome, very closely resembled those of other fish rhabdoviruses. At present it is not known if this is a novel virus species or if it is an isolate of a known fish rhabdovirus. Until a confirmed identification can be made, we will temporarily refer to this virus as Chinese sucker rhabdovirus (CSRV).
Resumo:
目的:研究三七总皂苷(Panax notoginseng saponins,PNS)对海马脑片CA1区锥体神经元兴奋性突触活动的作用和机理。方法:采用"盲法"全细胞膜片钳技术,记录PNS(0.05~0.4 g/L)对3~4周雄性wistar大鼠海马脑片(400μm)CA1区兴奋性突触后电流(excitatory post synaptic currents,EPSCs)和自发的微小兴奋性突触后电流(miniature excitatory post synapticcurrents,mEPSCs)幅度及频率的影响。结果:0.1~0.4 g/L PNS显著抑制海马脑片CA1区EPSCs(P<0.05);0.05~0.4 g/LPNS可明显增加CA1区锥体神经元自发mEPSCs的产生频率,但并不影响mEPSCs的幅度。结论:PNS可作用于突触前位点对海马神经元兴奋性突触活动产生调节作用,PNS增加mEPSCs频率的作用可能与促进突触前膜nAChR的激动有关,这可能是其调节海马神经元的兴奋性进而发挥益智作用的机制之一;PNS对EPSCs和mEPSCs的不同作用说明PNS是选择性抑制膜去极化所诱发的递质释放过程,PN...
Resumo:
1、KMBZ-009 改善高台应激所致认知障碍和应激相关的抑郁样行为及其相关机理 研究。 虽然适当的应激会提高动物的学习记忆功能,但过量的应激特别是无法逃避 的应激,往往导致依赖海马或前额叶的学习记忆功能受损,这与应激改变脑内应 激激素(皮质酮,皮质醇等)和神经递质的释放,影响突触传递和可塑性(包括 长时程增强和长时程抑制,LTP 和LTD)有关。一些疾病的发生、发展和恶化, 比如抑郁症(Depression)、创伤后应激障碍(PTSD),往往也和应激相关联,其 神经化学基础被证实与内分泌系统和单胺类(如五羟色,去甲肾上腺素,多巴胺) 神经递质系统的功能密切相关。遗憾的是,到目前为止还没有发现能治疗应激的 药物。本实验室过去的研究证实:KMBZ-009(申报新药时的名称为芬克罗酮,英 文名Phenchlobenpyrrone)——一种新的取代吡咯烷酮类化合物,通过调节细胞 内钙,改变脑内神经递质的释放,从而影响脑高级功能。KMBZ-009 对神经递质 释放影响是否能减轻应激导致的认知障碍及应激相关疾病的发生还没有进行研 究。本研究采用Morris 水迷宫、行为操作箱、绝望游泳、膜片钳和活体电生理 技术研究了KMBZ-009 对高台应激所致认知障碍和应激相关的抑郁样行为的影响 及其相关机理。 研究结果发现,高台应激或皮质酮注射造成大鼠空间记忆提取障碍,这与其 导致的海马CA1 区突触可塑性改变有关,而KMBZ-009 能成剂量依赖性地逆转应 激对空间记忆提取的损伤作用,这与它阻断应激或皮质酮异化的LTD 和恢复应激 或皮质酮损伤的LTP 密切相关。KMBZ-009 能部分地降低因应激而升高的血清皮 质酮含量,此外,KMBZ-009 对大鼠海马CA1 区锥体神经元的兴奋和抑制电流的 影响可能也参与了其对应激的调节作用。KMBZ-009 能显著增加海马CA1 区锥体 神经元上AMPA 受体介导的兴奋性突触后电流(EPSC)的幅度,但不影响其动力 学特性。NMDA 受体介导的EPSC 不受KMBZ-009 的影响;GABA 受体介导的抑制突 触后电流(IPSC)的幅度几乎不受KMBZ-009 的影响,而其受体动力学特性明显 被KMBZ-009 改变,表现为IPSC 恢复的时间显著延长。KMBZ-009 对CA1 区兴奋 抑制电流的调节作用,使大鼠海马细胞具有更强的维持细胞稳态的能力,从而避免应激导致神经元功能的损害。KMBZ-009 对抗应激对认知得损伤作用提示其可 能会减少动物的抑郁样行为,本实验结果发现,KMBZ-009 确实能明显减少小鼠 在强迫游泳(FST)中的不动时间,增加大鼠在72 秒低频差式强化(DRL-72s) 模型中的强化率,并降低其反应率。其机制是KMBZ-009 增加正常动物中枢神经 系统胞外NE 水平,激活alpha 和beta 肾上腺素受体,从而使得实验动物的抑郁 样行为明显减少。 2、KMBZ-009 减轻氧化应激对细胞活力、线粒体电位及海马LTP 的损伤作用。 前人的研究表明,氧自由基过多是导致老年痴呆患者和老年人神经细胞凋亡 与认知障碍的因素之一。KMBZ-009 和阿尼西坦是吡咯烷酮类化合物,研究显示 均具有促智作用。有报道指出阿尼西坦能减少神经胶质细胞在缺血缺氧时氧自由 基的生成,从而避免细胞受到氧应激损伤。本研究采用神经元原代培养和离体电 生理学方法,观察了KMBZ-009 和阿尼西坦对氧应激神经元的保护作用。结果发 现,KMBZ-009 和阿尼西坦均能保护氧应激神经元的线粒体的功能,对抗氧自由 基对神经元细胞活力的损伤,从而有效逆转了氧化应激对海马脑片CA1 区LTP 的 损伤作用。KMBZ-009 的作用效果比阿尼西坦的效果强10 倍。 3、银杏叶提取物及复方制剂改善老年大鼠空间学习记忆的突触可塑性机理。 有研究表明,银杏叶和三七叶提取物能调节神经系统的功能。本研究采用 Morris 水迷宫和活体电生理技术研究了银杏三七复方制剂及银杏叶提取物(以 标准银杏叶提取物——金纳多作为阳性对照药)改善老年大鼠空间学习记忆障碍 的突触可塑性机理研究。结果发现:老年大鼠空间学习记忆能力较差,高频诱导 不能在其海马CA1 区引发LTP,当长期服用金纳多或复方制剂一个月后,老年动 物的空间学习记忆功能得到明显改善,这可能与药物增强海马LTP 有密切关系。 复方制剂的作用效果与金纳多的效果相当。 4、悬尾应激损伤避暗作业学习行为的多巴胺D1 受体机制。 近年来的研究表明,DA 系统对应激非常敏感,应激改变PFC 内DA 的含量, 从而导致依赖于PFC 的工作记忆受损。但目前尚不知道应激对DA 系统的影响是 否涉及依赖杏仁核和海马的情绪学习记忆功能。因此,我们采用被动回避作业和 行为药理学的方法,初步探讨了此问题。结果发现:和对照组动物相比,随着悬 尾应激持续时间的增加(5min、10min、20min),动物在避暗作业作业重测试中的步入潜伏期明显缩短,当动物被悬尾应激后回到鼠笼中休息20min,其步入潜 伏期无明显变化;腹腔注射DA D1 受体拮抗剂SCH23390 呈剂量依赖性地缩短动 物的步入潜伏期,但SCH23390 腹腔注射和悬尾应激共同处理实验动物时,此种 D1 受体拮抗剂能有效逆转应激对步入潜伏期的影响;进一步的研究发现,应激 或D1 受体拮抗剂对痛觉感受的影响不是其改变动物步入潜伏期的主要因素。本 研究结果表明悬尾应激导致脑内多巴胺释放过度增加,杏仁核(可能还有海马及 相关神经回路)内的D1 受体被过度激活,从而导致小鼠在操作被动回避任务时 的记忆获得障碍。
Resumo:
海马突触可塑性是从细胞和分子水平上来阐述学习记忆机制,是学习记忆比 较直观的物质基础的一个体现。成瘾,是一种病态的、不可控制的吸食成瘾性药 物的行为,从某种角度来看,它也是一种记忆,通过篡夺正常生理神经通路产生 比正常生理反应强烈的可塑性,进而形成更有害的记忆。成瘾和学习记忆有很多 通路上甚至机制上的交叉,所以一部分研究学习记忆的方法可以用来研究成瘾。 应激,会影响正常的生理状态,并引发进一步的生化反应,进而影响到海马突触 可塑性和学习记忆。应激既然可以影响到学习记忆,而且成瘾的部分特征和学习 记忆又很相似,同时成瘾过程中基本上也伴随着应激,那么,应激在成瘾过程中 到底起着什么样的作用呢?它又是如何起作用的呢? 本文的实验致力于回答其中的部分问题,我们通过对吗啡成瘾过程中海马的 突触可塑性和学习记忆的研究发现:单次急性吗啡处理会在非应激动物上诱导出 突触增强,但是应激可以逆转吗啡引起的突触增强,诱导出长时程的突触抑制, 但是皮质酮的拮抗剂RU38486 可以阻断这种效果。皮质酮和吗啡可以产生动物 延迟逃避的现象,说明应激在成瘾过程中的重要影响。本实验对于应激在成瘾方 面的影响进行了研究,进一步的揭开了应激在其中的部分作用机制,这对于以后 的成瘾的形成及复吸的治疗都有一定的贡献。
Resumo:
在哺乳动物复杂的神经网络中,突触是信息传递的枢纽,其突触传递效能的持续性变化被称为突触可塑性(synaptic plasticity)。长时程增强(long-term potentiation,LTP)和长时程抑制(long-term depression,LTD)现象是两种经典的突触可塑性形式,被视作学习和记忆可能的物质基础,得到了广泛地关注。其中,海马CA1区谷氨酸能突触处的LTP和LTD目前研究得最为广泛。 α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid(AMPA)受体作为介导兴奋性谷氨酸能突触基础传递的主要受体,是海马CA1区LTP和LTD正常表达的必要条件。近期的研究表明,AMPA受体通过胞吞、胞吐及侧向移动等方式在细胞膜和细胞内进行着持续地循环。因此,通过调节AMPA受体的上、下膜,进而影响突触后膜上AMPA受体的数量,便能对LTP和LTD产生影响。在本研究中,我们利用生物信息学的手段,以AMPA受体为靶点,设计出了旨在特异阻断LTP或LTD的多肽。运用离体脑片全细胞记录方式,在海马CA1区证明了干扰肽Pep-A2能够特异地阻断LTP而不影响LTD,Pep-A3能够特异地阻断LTD而不影响LTP。并初步探究了其关键的作用位点,为进一步理解LTP和LTD具体的分子机理打下了基础。成瘾作为异常的学习记忆过程,势必涉及到突触可塑性的变化。而特异性地阻断LTP和LTD,对药物成瘾效果的影响却鲜有报道(Wang YT,2007)。在另一部分工作中,我们采用穿膜肽Tat-A2和Tat-A3,在吗啡条件化位置偏爱(morphine conditioned place preference,morphine CPP)模型小鼠的测试前进行系统给药,结果发现两种干扰肽均能阻断或损伤其CPP的表达过程。这一现象,提示我们LTP和LTD在条件化位置偏爱的表达过程中都是不可或缺的,同时也为人们更好地理解成瘾过程的机理,及开发专一有效的治疗药物提供了新的思路。
Resumo:
海马在某些类型的学习和记忆中起着关键的作用,而突触可塑性(synaptic plasticity)为学习和记忆的模型提供了理论基础。在海马环路中,分布着各种类型的可塑性,包括突触特异的Hebbian形式的可塑性,如长时程增强(long-term potentiation,LTP)和长时程抑制(long-term depression,LTD);稳态可塑性(homeostatic plasticity),如突触缩放(synaptic scaling)。稳态可塑性是一种整体的调控过程,它可以调节神经元甚至神经网络的平衡;而Hebbian可塑性则是突触特异的,即每个突触进行单独调控的过程。 越来越多的研究提示稳态可塑性和Hebbian可塑性之间存在着空间间隙(spatial gap),那么,如何使得神经元可以通过Hebbian可塑性的过程来维持细胞整体的兴奋性就变得尤为重要。一些报道揭示了LTP和LTD可以在同一突触通路中同时被激活,因此,我们提出组合突触可塑性的概念,即LTP和LTD的组合,它在赋予系统灵活性的同时又可以降低噪音维持系统的稳定性。基于此,本文将围绕这个问题而开展实验工作。 通过对海马CA1区锥体神经元的微小兴奋性突触后电流(miniature excitatory synaptic current, mEPSC)进行测定分析,我们发现mEPSC的幅度分布符合双峰正态分布(double-peak normal distribution)。Theta节律刺激(theta burst stimuli, TBS)诱导后,mEPSC的幅度分布发生改变,呈现右移趋势。随后,采用干扰肽Pep-A2特异地阻断LTP而不影响LTD,我们发现Pep-A2不影响基础状态下mEPSC的幅度分布。在干扰肽Pep-A2存在下,TBS诱导对基础状态下mEPSC的幅度分布也没有影响。结果为揭示LTP和LTD的组合可塑性提供了初步的证据,对进一步理解记忆的编码过程提供了一定的基础。社交隔离可以引起实验大鼠产生焦虑样和抑郁样的行为,而性经历可以改变动物的情绪状态,降低焦虑样和抑郁样的反应。然而,性经历后进行社交隔离对大鼠情绪的影响并没有报道。在这部分工作中,雄性大鼠经历一周的社交活动(male-male paired housing)或者性活动(male-female paired housing),随后进行一段时间的隔离(1天,2天或者7天)。我们发现,经历过性活动的大鼠,无论隔离与否都表现出相似的情绪反应,包括焦虑样和抑郁样行为以及超声波(ultrasonic vocalizations,USVs)发放;而未经历过性活动的大鼠,其情绪反应随着隔离时间的不同而不同。这一现象提示我们,先前的性经历可以对抗实验动物对环境应激事件,如社交隔离的反应。
Resumo:
突触可塑性(syanptic plasticity)是指在某种条件下突触传递效能的持 续性变化,是从细胞和分子水平上来阐述学习记忆的机制,是学习记忆的基础, 存在多种形式,主要包括长时程增强(LTP)和长时程抑制(LTD)等。应激(stress) 就是指机体对各种内、外界刺激因素所作出的适应性反应的过程。应激会影响正 常的生理状态,并引发进一步的生化反应,进而影响到海马突触可塑性和学习记 忆。成瘾(addiction)是指对药物的使用失去控制,或者强迫性的寻求和使用 药物,而不顾由此带来的恶性后果,从某种角度来看,它也是一种记忆,通过篡 夺正常生理神经通路而产生比正常生理反应更强烈的可塑性,进而形成有害的异 常记忆,其最核心的特征就是对药物的强迫性渴求和复吸。成瘾一旦形成,可能 成为伴随一生的状态,即使经过长期的戒断,也会表现出强烈的渴求以及有复吸 的高度危险性。成瘾和学习记忆有很多神经通路甚至分子机制上的交叉,所以一 部分研究学习记忆的方法可以用来研究成瘾,反之,成瘾也是一种很好的研究学 习记忆的模型。 既然应激可以影响突触可塑性和学习记忆,而对于吸毒者来说,戒断本身就 是一种应激,那么探讨应激和戒断对突触可塑性和学习记忆的影响,对临床上的 戒毒工作将有着重要意义。基于此,本文将围绕这个问题而开展实验工作。 我们采用电生理、行为学及生化等研究方法对吗啡戒断过程中突触可塑性和 学习记忆,以及应激在其中的作用进行了一些研究。电生理的结果表明:在吗啡 戒断过程中,海马LTP 的大小呈现出倒-U 型曲线,其中戒断4 天时LTP 最大。 应激可以将最大的LTP 提前在戒断18 小时出现,而糖皮质激素受体拮抗剂米非司酮或者熄灭剂量的吗啡能够阻断最大的LTP 出现。同时,海马下托-伏隔核通 路的突触可塑性也出现类似的戒断时间依赖性的改变。行为学研究发现:戒断过 程中,大鼠的疼痛阈值降低,同时降低急性吗啡的镇痛效应,而这种变化能够被 应激或米非司酮所改变。另外,条件位置偏爱实验结果显示吗啡条件位置偏爱的 形成依赖于海马和伏隔核糖皮质激素受体。生化实验结果显示:戒断过程中,AMPA 受体亚型GluR1 和GluR2/3 及其调节分子CaMKⅡ会出现表达动态改变。 本实验对于应激和戒断对突触可塑性和学习记忆的影响进行了研究,进一步 揭开了应激在戒断中的部分作用机制,这将对于以后研究治疗毒品渴求和复吸有 一定的贡献
Resumo:
对隆肛蛙属的物种构成进行了订正,建立新属肛刺蛙属Yerana gen. nov.;订正后的隆肛蛙属现仅隶2种, 即隆肛蛙F. quadrana和太行隆肛蛙F. taihangnicus。运用形态学分析探讨了隆肛蛙属物种及种群的形态差异和分类关系,通过分子系统学研究探讨了隆肛蛙属物种及种群的分类和系统发育关系,运用动物地理学方法结合系统发育关系探讨了隆肛蛙属种群的地理分布格局成因与历史过程。主要结果和推论如下: 1.隆肛蛙属物种构成的订正及一新属建立 建立新属肛刺蛙属,将隆肛蛙属中的原叶氏隆肛蛙F. yei归隶新属肛刺蛙属并更名为叶氏肛刺蛙Y. yei,,新属建立的主要依据为:(1)雄性肛部隆起,肛孔下方有两个布满黑刺的大的白色球形隆起,具单咽下内声囊, 第一指具婚刺;(2)形态量度分析表明叶氏肛刺蛙与隆肛蛙和太行隆肛蛙的形态差异远大于后两者之间的差异;(3)叶氏肛刺蛙的分布区与隆肛蛙和太行隆肛蛙的分布区距离较远且呈隔离状态;(4)分子系统学研究资料(Jiang et al.,2005)证明叶氏肛刺蛙与隆肛蛙和太行隆肛蛙非单系发生;叶氏肛刺蛙在第二支中位于基部。因此,隆肛蛙属现仅隶2种,即隆肛蛙和太行隆肛蛙。 2.隆肛蛙属种群形态学研究 对隆肛蛙属中隆肛蛙和太行隆肛蛙的15个地理种群565只标本的28项形态性状进行了测量,运用典型判别分析法对其分析的结果表明:(1)太行隆肛蛙与隆肛蛙形态差异明显,支持其为不同的物种;(2)原隆肛蛙河南伏牛山种群和山西中条山种群应为太行隆肛蛙的地理种群;(3)隆肛蛙不同地理种群之间形态差异明显,其中四川安县种群、陕西周至种群和湖北利川种群与模式产地重庆巫山种群的差异可能达到了亚种或亚种以上分化水平。对隆肛蛙属量度分析的15个种群进行定性形态分析表明其分为三种形态型,对应隆肛蛙、过渡型和太行隆肛蛙,其变异特征主要为内跗褶、雄性肛部隆起及疣粒分布、第五趾外侧缘膜等,这与量度分析结果相似。 3.隆肛蛙属种群分子系统学研究 测定隆肛蛙属Feirana的2种19种群的线粒体12S rRNA和16S rRNA基因片段、ND2基因的DNA序列,比对后共计1953bps。(1)遗传多样性与距离分析:结果表明,隆肛蛙属种群具很高的遗传多样性,19个种群样品表现出19种单倍型(遗传多样性指数Hd=1.0); ND2基因的进化信息含量远高于12SrRNA和16SrRNA。隆肛蛙属2种群组内的种群间的遗传距离远小于两种群组间的距离,种群在不同基因上的遗传距离表现的关系与对应的系统树一致。(2)系统发育关系分析:结果表明,不同基因片断基于不同方法构建的隆肛蛙属种群系统发育树结构基本一致,基本表明隆肛蛙属种群为单系发生;它们在系统树中分为两大支,分别对应于隆肛蛙和太行隆肛蛙;支持中条山种群(沁水、历山和济源种群)和伏牛山种群(栾川和内乡种群)为太行隆肛蛙的地理种群,而原隆肛蛙秦岭中东段的部分种群(柞水、宁陕、长安大坝沟种群)也应为太行隆肛蛙的地理种群。(3)亚种分化分析:根据遗传距离分析和系统发育关系分析结果,并考虑形态上的差异情况以及地理分布信息,隆肛蛙所隶种群组可分为2亚种,即隆肛蛙指名亚种F. quadrana quadrana包括四川盆地东缘大巴山东段-巫山-武陵山北麓种群和秦岭中段(周至板房子和长安广货街)种群,他们在系统关系树上聚为一支;安县亚种F. quadrana anxianensis包括四川盆地西缘岷山东麓-龙门山-大巴山和秦岭西段的种群(安县、青川、文县、南江和凤县种群),他们在系统关系树上聚为一支。太行隆肛蛙所隶种群组也可分为2亚种,即太行隆肛蛙指名亚种F. taihangnicus taihangnicus包括中条山的种群(沁水、历山和济源种群)和中东秦岭的部分种群(柞水、长安大坝沟和宁陕种群),他们在系统关系树上聚为一支;太行隆肛蛙伏牛亚种F. taihangnicus funiuensis,为伏牛山地区的种群(栾川和内乡种群),他们在系统关系树上聚为一支。 4.隆肛蛙属种群动物地理学研究 隆肛蛙属19种群的分歧年代分析: 以长江巫山段和黄河三门峡段的形成历史时期为参考点,根据已测隆肛蛙属19种群及其外群包括N. pleski、P. yunnanesis、P. robertingeri、F. limnocharis的1953bps DNA序列构建分子钟,获得各支系的分歧年代。结果表明:①棘蛙族在70Ma左右开始其独立演化历程,这与Roelants et al.(2004)的分析结果~60±15Ma左右开始分化基本一致,后者印证了本文的分子钟。②隆肛蛙属的起始分化年代较早,隆肛蛙和太行隆肛蛙两种群组的最近祖先种群大概在46Ma~50Ma左右;隆肛蛙和太行隆肛蛙种群组内的种群分化年代相对两种群组间晚得多, 隆肛蛙种群组内两亚种分化起始年代约为10Ma左右,而太行隆肛蛙种群组内两亚种分化起始年代约为6Ma。 隆肛蛙属种群分布格局形成过程分析: ①隆肛蛙属的系统关系与地理分布格局密切相关,大部分系统分支分级与地理距离成正比;②隆肛蛙属最近祖先种群的分化中心可能位于秦岭中部地区, 隆肛蛙属的种群分布格局的形成表现为隔离分化与扩散相结合的机制,由隔离分化产生的隆肛蛙祖先种群主要从秦岭中部向西南方向扩散,后隔离分化为两亚种;太行隆肛蛙祖先种群向东北方向扩散也分化为两亚种。 隆肛蛙属种群分布区域地质历史的探讨:本文所建分子钟和种群分化方式印证了该区域的几次主要地质事件,包括岷山-龙门山-西秦岭等地区的快速差异隆起、第四纪冰期等。 The specific composition of the genus Feirana should be revised. A new genus Yerana gen. nov.(Ranidae:Dicroglossinae)was established based on morphological data-set and molecular phylogeny, as a result, only two species F. quadrana and F. taihangnicus are classified into Feirana now. Morphological differences and taxonomy of populations of Feirana were investigated based on morphological and morphometric data; phylogenetic relationships and taxonomy of populations of Feirana were elucidated using molecular data, and then the proceeding of the distribution pattern of populations of Feirana were discussed. The main results and conclusions and proposals were presented as following: 1. Revising of the specific composition of the genus Feirana and establishment of a new genus The new genus Yerana, only containing the type species Y. yei, was established based on the following evidences: (1) In adult male, distinct up-heaved circular vesicle presents around the anal, and under anal there are two white balls on which black spines exist, black horny spines scatter on the upper side of first finger, and internal single subgular vocal sac presents; (2) there is obvious morphometric differences between Yerana and Feirana; (3) Yerana is distributed far from Feirana; (4) evidences of molecular phylogeny(Jiang et al.,2005)suggested that Yerana take a special phylogenetic clade which is different from other genus included in the tribe Paini. As a result, there are only two species in Feirana, i.e., F. quadrana and F. taihangnicus. 2. Morphological research of populations of Feirana Twenty-eight characters of 565 individuals of 15 populations of the genus Feirana were measured, the results of Canonical Discriminant analysis of the morphometric data-set indicated that: (1) there are very prominent differences between the two species F. quadrana and F. taihangnicus. The validity of species F. taihangnicus was approved here; (2) Mt. Funiu population and Mt. Zhongtiao population should belong to the species F. taihangnicus; (3) Obvious differences exist among 12 populations of F. quadrana, the differentiation among Zhouzhi population, Anxian population, Lichuan population, and Wushan population together with the others probably reach sub-specific or specific level. Result of morphological comparison between 15 different populations show that 3 morphological types are recogenized in according with F. quadrana, F. taihangnicus and intergradation, this result conform to the result of morphometric analysis. 3. Molecular phylogenetic study on populaions of Feirana Fragment of 12SrRNA and 16SrRNA genes, and ND2 gene of 19 populations of two species of Feirana were sequenced and aligned, from which 1953 bps were received. (1) analyses of genetic distance and hereditary diversity indicated that: genetic distance between populations in each group were less than distance between two groups of Feirana, 19 haplotypes were recognized from 19 samples of 19 populations, so the hereditary diversity of populations of Feirana was very high (Hd=1.0), phylogenetic information in ND2 gene is more than fragment sequence of 12SrRNA and 16SrRNA genes. (2) Result of molecular phylogeny indicate that the phylogenetic trees constructed using different methods based on different sequence data sets showed the revised genus Feirana is monophyletic since the 19 populations of Feirana were firstly clustered together as one large clade, which was further clustered into two major clades, corresponding to F. quadrana(GroupⅠ) and F. taihangnicus(GroupⅡ), respectively. So populations of Qinshui and Lishan in Mt. Zhongtiao, populations of Luanchuan and Neixiang in Mt. Funiu, and populations of Zhashui, Dabagou of Chang’an and Ningshan in eastern Mt. Qinling should belong to the species F. taihangnicus; (3) Subspecific differentiation. on the basis of genetic distance, phylogenetic trees and geographical distribution, F. quadrana should have two subspecies, i.e., F. quadrana qudadrana, consisting of the populations Guanghuojie of Chang’an and Zhouzhi in Mid-Mt. Qinling, populations in Wushan area and northern Mt. Wuling (Lichuan), and F. qudadrana anxianensis, consisting of the populations in eastern Mt. Ming shan-Mt. Longmen-western Mt. Daba-western Mt. Qinling (Anxian, Qingchuan, Wenxian, Nanjiang and Fengxian); F. taihangnicus should also has two subspecies, i.e., F. taihangnicus taihangnicus, consisting of the populations in Mt. Zhongtiao and eastern Mt. Qinling, and F. taihangnicus funiuensis, consisting of the populations in Mt. Funiu. 4. Zoogeography of populaions of Feirana Analysis for divergent time of 19 populations of Feirana: Using the dates of run-through of Wushan segment of Changjiang River as the time when the population of Lichuan started differentiated from the populations of Wushan and Shennongjia, and the dates of Sanmenxia segment of Yellow River as the time when the populations in Mt. Zhongtiao started differentiated from the population of Dabagou in Chang’an, molecular clock was established using sequences with 1953 bps of 19 populations of Feirana and outgroup including N. pleski, P. yunnanesis, P. robertingeri, F. limnocharis in order to estimate divergent time of all clades. Result of that indicated that: ① the tribe Paini started to evolve independently at about 70Ma when is in consistent with that estimated by Roelants et al.(2004)with result of about ~60±15Ma, they were corroborated by each other, this confirms the validity of this molecular clock; ② divergent time for speciation of Feriana is early, ancestral populations of F. quadrana and F. taihangnicus were found about 46Ma~50Ma; differentiation of populations within species is greatly late to the divergence of the two species, divergent time for F. quadrana is 10Ma and divergent time for F. taihangnicus is 6Ma. Proceeding of distribution pattern of Feirana. Phylogenetic relationships of populations of Feirana matched quite with distribution pattern of them, the relationships among clades showed in phylogenetic trees is direct ratio to geographical distance of them; the estimated date of speciation between two species of Feirana was as early as speciation of Paa yunnanesis and Nanara pleski; middle part of Mt. Qinling is the center of speciation of Feirana, combination of mult-events of dispersal and vicariance are probably the mechanism of speciation of Feirana, F. quadrana colonized the mid-Mt. Qinling and then differentiated into two subspecies in southwest direction, ancestral population of F. taihangnicus colonized the mid-Mt. Qinling and then differentiated into two subspecies in northeast direction. On geological history of the distribution of Feirana. According to molecular clock and speciation model of populations of Feirana, some geological events are confirmed, including special rise of Mt. Minshan- Mt. Longmen-western Mt. Qinling, glacial age.
Resumo:
This paper describes the formation of fibril like aggregates from the self-assembly of block copolymer mixture (polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and polystyrene-b-poly(acrylic acid) (PS-b-PAA)) via interpolymer hydrogen bonding in nonselective solvent. The hydrogen bonding between P4VP and PAA in chloroform leads to the formation of complex. When all the pyridine units in P4VP were all hydrogen bonded to acrylic acid in PAA, the formed complex is insoluble, resulting in the formation of spherical micellar aggregates and nanorods.
Resumo:
We have investigated the effect of Shear flow on the formation of rill.-shaped ABA triblock copolymer (P4VP(43)-b-PS260-b-P4VP(43)) micelles. The results reveal that Shear flow Plays an important role in the formation of the rings Both ring size and its, distribution are found to be dependent sensitively on the stirring rate. Sizable rings are more likely to be formed at moderate stirring rate, Interestingly, the ring formation mechanism is also dependent oil the Shear flow. Copolymers are likely to form rings via end-to-end cylinder connection at low stirring rates, whereas they tend to form rings via the pathway of the rod-sphere-vesicle-ring it high stirring rates.
Resumo:
Nonviral vectors are safer than viral systems for gene therapy applications. However, the limited efficacy always prevents their being widely used in clinical practice. Aside from searching new gene nonviral vectors, many researchers focus on finding out new substances to improve the transfection efficiency of existent vectors. In this work, we found a transfection enhancer, nocodazole (NCZ), for dimethyldioctadecylammonium (DODAB, a cationic lipid) bilayer coated gold nanoparticles (AuNPs) mediated gene delivery. It was found that NCZ produces 3-fold transfection enhancement to HEK 293T cells assessed by flow cytometry (FCM). The result was further confirmed by luciferase assay, in which NCZ induced more than 5 times improvement in transfection efficiency after 48 h of transfection. The results from the inductively coupled plasma mass spectrometry (ICP-MS) and FCM showed that NCZ did not affect the internalization of DODAB-AuNPs/DNA complexes. The trafficking of the complexes by transmission electron microscopy (TEM) indicated that the interrupted transportation of the complexes to the lysosomes contributed greatly to the transfection enhancement.
Resumo:
An oxygen carrier was prepared by encapsulating carbonylated hemoglobin (CO-Hb) molecules into polypeptide vesicles made from poly(L-lysine)-block-poly(L-phenylalanine) (PLL-b-PPA) diblock copolymers in aqueous medium at pH 5.8. The encapsulation was confirmed by confocal laser scanning microscopy (CLSM). The morphology and size of the Vesicles were studied by field-emission scanning electron microscopy (ESEM). They had a spherical shape with it mean diameter of about 4 to 5 mu m. The encapsulation efficiency of hemoglobin was 40 wt %, and the hemoglobin content in the vesicles was 32 wt %. The CO-Hb encapsulated in the PLL-b-PPA vesicles was more stable than free CO-Hb under ambient conditions, In the presence of a O-2 atmosphere, the CO-Hb in the vesicle could be converted into oxygen-binding hemoglobin (O-2-Hb) under irradiation of visible light for 2 h. Therefore, the CO-Hb/PLL-b-PPA vesicles are expected to be used its red blood cell substitutes.
Resumo:
We have studied, both experimentally and theoretically, the aggregation morphology of the ABA amphiphilic triblock copolymer in dilute solution by changing the solvent property. Experimental results showed that the micellar morphology changed from spheres to rods and then to vesicles by changing the common solvent from N-N-dimethylformamide (DMF) to dioxane and then to tetrahydrofuran (THF). These controllable aggregates were also obtained by Monte Carlo simulation. The simulative results showed that the solvent property is a key factor that determines the copolymer aggregation morphology. The morphology changed from spheres to rods and then to vesicles by increasing the solvent solubility, corresponding to the change of stretched of the copolymer chains in the micellar cores. This result is in good agreement with the experimental one. Moreover, the simulative results revealed that the end-to-end distant of the ABA triblock copolymer in the vesicle was larger than that in the spheres and rods, indicating that the copolymer chains were more stretched in vesicles than in the spheres and rods. Furthermore, we gave the distribution of the fraction of the chain number with the end-to-end distance. The results indicated that the amount of folded chains is almost the same as that of stretched chains in the vesicle. Although most chains were folded, stretched chains could be found in the rod and sphere micelles.
Resumo:
This report describes direct formation of giant vesicles from a series of poly(L-lysine)-block-poly(L-phenylalanine) (PLL-b-PPA) block copolymers from their water solution. These polymers are prepared by successive ring-opening polymerization (ROP) of the two alpha-amino acid N-carboxyanhydrides and then removing the side chain protecting groups by acidolysis. The structures of the copolymers are confirmed by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and size exclusion chromatography ( SEC). The vesicles are studied by atomic force microscopy (AFM), field emission scanning electron microscopy (ESEM), and confocal laser scanning microscopy (CLSM). Rhodamine B is used as a fluorescent probe to confirm the existence of the vesicle with an aqueous interior. The vesicle size is in the range 0.55-6 mu m, depending on the absolute and relative lengths of the two blocks, on initial polymer concentration, and on solution pH. The vesicles are still stable in water for 2 months after preparation. Addition of the copolymer to DNA solution results in complex formation with it. The complex assumes the morphology of irregular particles of less than 2 mu m. It is expected to be used in drug and gene delivery.
Resumo:
Substantial progress has been made recently in extending the supramolecular assembly of biomimetic structures to vesicle-based sophisticated nanocomposites and mesostructures. We report herein the successful preparation of unilamellar surfactant vesicles coated with a monolayer of ring-shaped {Mo-154} polyoxometalate (POM) nanoclusters, (NH4)(28)[Mo-154 (NO)(14)O(448)Hi(4)(H2O)(70)].approximate to 350H(2)O, by coulomb attractions using preformed didodecyldimethylammonium bromide (DDAB) surfactant vesicles as templates. The resultant vesicle-templated supramolecular assemblies are robust (they do not disintegrate upon dehydration) both at room-temperature ambient and vacuum conditions, as characterized by conventional transmission electron microscopy (TEM) and atomic force microscopy (AFM). The flexibility of the complex soft assemblies was also revealed by AFM measurements. The effect of POM-vesicle coulomb attractions on the dimensions of the templating vesicles was also investigated by using dynamic light scattering (DLS).Although origins of the structure stability of the as-prepared supramolecular assemblies are not clear yet, the nanometer scale cavities and the related properties of macroions of the POM clusters may play an important role in it.