Mechanism of How Salt-Gradient-Induced Charges Affect the Translocation of DNA Molecules through a Nanopore

Experiments using nanopores demonstrated that a salt gradient enhances the capture rate of DNA and reduces its translocation speed. These two effects can help to enable electrical DNA sequencing with nanopores. Here, we provide a quantitative theoretical evaluation that shows the positive net charges, which accumulate around the pore entrance due to the salt gradient, are responsible for the two observed effects: they reinforce the electric capture field, resulting in promoted molecule capture rate; and they induce cationic electroosmotic flow through the nanopore, thus significantly retarding the motion of the anionic DNA through the nanopore. Our multiphysical simulation results show that, during the polymer trapping stage, the former effect plays the major role, thus resulting in promoted DNA capture rate, while during the nanopore-penetrating stage the latter effect dominates and consequently reduces the DNA translocation speed significantly. Quantitative agreement with experimental results has been reached by further taking nanopore wall surface charges into account.     

中国大鲵视网膜的光镜和扫描电镜研究

用光镜和扫描电镜观察了大鲵视网膜各类细胞的形态及分布, 对视细胞和节细胞进行计数。视网腊中三个核层及两个网状层分布均匀,无中央凹。每张视网膜的视细胞总数约130000,节细胞约8000,视杆与视锥之比为8.5：1。扫描电镜下,视杆外节表面的小叶间沟清晰;视杆视锥外节均有从内节伸出的20-30条萼状突起;核周体表面亦有20-30条细胞质突起。文中还报道了幼体视细胞的形态及密度。讨论了上述结构的机能。     

母牛分枝杆菌制剂对T淋巴细胞增殖反应影响的研究

以氚标记胸腺嘧啶核苷(~3H-TdR)掺入法检测每分钟脉冲数(CPM),比较母牛分枝杆菌活菌悬液、辐射杀死菌悬液及高温杀死菌悬液对健康人外周血T淋巴细胞增殖反应的影响.以此作为评价治疗以细胞介导免疫为主的结核病免疫功能障碍免疫制剂效力的一个重要参数.在加入单一刺激因子实验中,对照组CPM为448±131;加入BCG、母牛分枝杆菌活菌悬液、辐射杀灭菌悬液以及高温杀死菌悬液的CPM分别为1037±194,2299±140,1819±528,994±186.这4种制剂的刺激指数均在2.0以上,尤其是母牛分枝杆菌活菌悬液、辐射杀死菌悬液分别为5.13,4.06.结果表明,母牛分枝杆菌3种制剂与BCG基本相似,在体外对T淋巴细胞增殖反应有明显的促进作用,其中以活菌悬液和辐射杀死菌悬液更为显著.另一试验中,以重组白细胞介素-2(rIL-2)作对照,BCG、母牛分枝杆菌悬液、辐射杀死菌悬液及高温杀死菌悬液分别加入rIL-2,目的在于观察菌体抗原加淋巴因子对T淋巴细胞增殖反应有无协同刺激作用.对照组的CPM为3721±1336,BCG加rIL-2组CPM为6904±1218;母牛分枝杆菌3种制剂的CPM分别为9544±172…     

大鼠实验性脾虚证胃粘膜内分泌细胞变化的免疫组织化学研究

用正常成年雄性Wistar大鼠53只,体重100～150g,分为正常对照组、实验性脾虚组、自然恢复组和四君子汤治疗组。取胃,固定于Bouin液。制成石蜡切片,进行(1)HE染色;(2)免疫组织化学染色,按Sternberger PAP法显示胃泌素细胞(G细胞)、生长抑素细胞(D细胞)和5-HT细胞。根据细胞的免疫反应程度,将细胞分为强阳性、中等阳性和弱阳性三级,每例动物计数三种细胞各1,000个,并计算各级细胞占的百分比;(3)从正常对照组,脾虚组随机选择各5例动物,对D细胞和G细胞进行显微分光光度计的定量测定;(4)由四组动物随机选择各5例,进行G细胞和D细胞密度及G/D细胞比值的测定。本文的观察表明:(1)脾虚组胃粘膜未见明显的组织学变化;(2)内分泌细胞:与对照组相比,脾虚组G细胞和5-HT细胞中,弱阳性细胞增多,表明分泌活动增强;D细胞弱阳性和中等阳性细胞减少,强阳性细胞增多,表明分泌释放减弱,合成增强。与自然恢复组比较,治疗组G细胞和D细胞的分泌活动接近于对照组;5-HT细胞无明显的恢复;(3)显微分光光度计的测定结果与光镜观察一致,脾虚组G细胞胃泌素反应物的含量低于对照组,D细胞内生长抑素反应物的含量高于对照组;(4)脾虚组G细胞密度低于对照组(P<0.01),D细胞密度略高于对照组,G/D细胞比值也低于对照组(P<0.01)。本文结果提示,脾虚证这些内分泌细胞的分泌活动出现异常,可能是导致消化功能紊乱的原因之一。经四君子汤治疗后,内分泌细胞的分泌活动接近于对照组,说明此药对脾虚证有一定的治疗作用。     

RHCG基因在非小细胞肺癌中的表达及对细胞增殖的影响

为了探讨Rh type C glycoprotein (RHCG)对非小细胞肺癌(non-small cell lung cancer,NSCLC)细胞增殖的影响及可能的作用机制,本研究使用荧光定量PCR法检测12对NSCLC及癌旁组织样本中RHCG mRNA的表达水平及pcDNA3.1-RHCG质粒对A549细胞RHCG m RNA的表达;采用CCK-8法检测细胞增殖能力;运用PI染色法检测细胞周期;使用免疫印迹法检p-PI3K、PI3K、p-AKT以及AKT蛋白表达水平。本研究发现,与癌旁组织比较,NSCLC中RHCG m RNA表达水平明显降低。RHCG过表达能抑制NSCLC细胞系A549细胞增殖能力。此外,RHCG过表达使A549细胞周期G1/S期转化发生阻滞。本研究还发现,RHCG过表达可下调A549细胞p-PI3K/PI3K和p-AKT/AKT水平。本研究表明,RHCG抑制NSCLC细胞增殖的作用与其抑制PI3K/AKT信号通路有关。     

放牧践踏对黄蒿功能性状的影响

植物功能性状是构成植物个体的基础,从性状角度揭示植物个体特征的变化机制尤为重要。该研究以半干旱沙质草地优势草本植物黄蒿为研究对象,探讨不同践踏强度在生长季早期对其功能性状的影响。结果表明：(1)在群落水平上,放牧践踏显著降低了生长季早期植物群落高度;而在个体水平上,黄蒿株高不是响应放牧践踏的敏感性状。(2)黄蒿的叶长、叶宽随践踏强度增加呈先增加后减少的趋势,在中度践踏强度下达到最高;茎直径随践踏强度的增加而增加;根系和全株性状随践踏强度增加无显著差异。(3)黄蒿的叶片长度、叶片宽度、单叶面积随叶片厚度的增加而减小,且叶片与一级根数目、根茎叶生物量之间均呈显著正相关关系;放牧践踏会影响黄蒿茎直径,但对其他表型性状没有显著影响;在生长发育过程中,黄蒿通过不同表型性状的非对称变化进行性状之间的权衡,践踏强度的增加对生长季早期黄蒿根茎叶生物量积累的影响很小。研究认为,黄蒿在生长季早期对放牧践踏具有较强的抵抗力,这对生长季早期半干旱沙地放牧压力的选择和物种保护具有重要的指导意义。     

Viral RNA-binding ability conferred by SUMOylation at PB1 K612 of influenza A virus is essential for viral pathogenesis and transmission

Posttranslational modifications, such as SUMOylation, play specific roles in the life cycle of invading pathogens. However, the effect of SUMOylation on the adaptation, pathogenesis, and transmission of influenza A virus (IAV) remains largely unknown. Here, we found that a conserved lysine residue at position 612 (K612) of the polymerase basic protein 1 (PB1) of IAV is a bona fide SUMOylation site. SUMOylation of PB1 at K612 had no effect on the stability or cellular localization of PB1, but was critical for viral ribonucleoprotein (vRNP) complex activity and virus replication in vitro. When tested in vivo, we found that the virulence of SUMOylation-defective PB1/K612R mutant IAVs was highly attenuated in mice. Moreover, the airborne transmission of a 2009 pandemic H1N1 PB1/K612R mutant virus was impaired in ferrets, resulting in reversion to wild-type PB1 K612. Mechanistically, SUMOylation at K612 was essential for PB1 to act as the enzymatic core of the viral polymerase by preserving its ability to bind viral RNA. Our study reveals an essential role for PB1 K612 SUMOylation in the pathogenesis and transmission of IAVs, which can be targeted for the design of anti-influenza therapies.     

Physiological control of an in-series connected pulsatile VAD: numerical simulation study

This paper investigates ventricular assist device (VAD)-assisted cardiovascular dynamics under proportion–integration–differentiation (PID) feedback control. Previously, we have studied the cardiovascular responses under the support of an in-series connected reciprocating-valve VAD through numerical simulation, and no feedback control was applied in the VAD. In this research, we explore the contribution of the VAD control on the circulatory dynamics assisted by the reciprocating-valve VAD, in response to the changing physiological conditions. The classical PID control algorithm is implemented to regulate the VAD stroke beat-to-beat, based on the error signal between the expected and the realistic mean aortic pressures. Simulation results show that under the PID VAD control, physiological variables such as left atrial, ventricular and systemic arterial pressures, cardiac output and ventricular volumes are satisfactorily maintained in the physiological ranges. With the online PID feedback control, operation of the reciprocating-valve VAD can be satisfactorily regulated to accommodate metabolic requirements under various physiological conditions including normal resting and exercise situations.