Dividing a supercoiled DNA molecule into two independent topological domains

Both prokaryotic and eukaryotic chromosomes are organized into many independent topological domains. These topological domains may be formed through constraining each DNA end from rotating by interacting with nuclear proteins; i.e., DNA-binding proteins. However, so far, evidence to support this hypothesis is still elusive. Here we developed two biochemical methods; i.e., DNA-nicking and DNA-gyrase methods to examine whether certain sequence-specific DNA-binding proteins are capable of separating a supercoiled DNA molecule into distinct topological domains. Our approach is based on the successful construction of a series of plasmid DNA templates that contain many tandem copies of one or two DNA-binding sites in two different locations. With these approaches and atomic force microscopy, we discovered that several sequence-specific DNA-binding proteins; i.e., lac repressor, gal repressor, and λ O protein, are able to divide a supercoiled DNA molecule into two independent topological domains. These topological domains are stable under our experimental conditions. Our results can be explained by a topological barrier model in which nucleoprotein complexes confine DNA supercoils to localized regions. We propose that DNA topological barriers are certain nucleoprotein complexes that contain stable toroidal supercoils assembled from DNA-looping or tightly wrapping DNA around DNA-binding proteins. The DNA topological barrier model may be a general mechanism for certain DNA-binding proteins, such as histone or histone-like proteins, to modulate topology of chromosome DNA in vivo.     

Lower optimal dose of amrubicin for relapsed small-cell lung cancer: a retrospective study

International Journal of Clinical Oncology - Amrubicin (AMR) is one of the most active agents for small-cell lung cancer (SCLC). However, hematologic toxicity and infection at a commonly used dose...     

高效液相-质谱法研究犬体内香贝注射液的药代动力学

目的 以苦木碱丁为检定物,测定杂种犬血浆中苦木碱丁的含量,研究香贝注射液的药代动力学过程.方法 两组杂种犬分别经股静脉注射香贝注射液0.8,1.6 mL·kg-1,然后采集血样,用高效液相-质谱联用(HPLC-MS)方法 测定各时间点血浆中的药物浓度,应用实用药代动力学软件3p97拟合计算药代动力学参数.结果 犬股静脉给药后的血药浓度-时间曲线符合二室开放模型,0.8,1.6 mL·kg-1两个剂量对应的主要药代动力学参数分别为:分布半衰期(t1/2α)为1.15 min和1.24 min,消除半衰期(t1/2β)分别为8.69 min和9.85 min,曲线下面积(AUC)为124.27 ng·mL-1·min-1和234.78 ng·mL-1·min-1;血浆清除率(CL)为450.64 mL·min-1和477.04 mL·min-1.结论 香贝注射液静脉给药后,在犬体内具有分布快,消除迅速的特点.     

脑肠肽Ghrelin对血管紧张素Ⅱ诱导的大鼠脑主动脉血管平滑肌细胞胞内钙浓度上升的影响

目的研究脑肠肽Ghrelin对血管紧张素Ⅱ（AngⅡ）诱导的大鼠胸主动脉血管平滑肌细胞（VSMCs）胞内钙离子浓度上升的作用,并初步探讨其机制。方法采用细胞培养的方法获得大鼠胸主动脉VSMCs,经Fluo-4-AM染色后,采用激光共聚焦显微镜技术分别检测加入AngⅡ后,1×10^-7mol·L^-1和1×10^-5mol·L^-1的Ghrelin对胞内钙荧光强度（FI）的影响,以及腺苷酸环化酶抑制剂Sq22536对Ghrelin作用的影响。结果①2×10^-8mol·L^-1的AngⅡ可以使得VSMCs胞内钙FI上升到静息状态的（165±76）％;②随后加入1×10^-7mol·L^-1的Ghrelin可以使FI下降到（117±34）％（P〈0．01vs①）;③加入1×10^-5mol·L^-1的Ghrelin可以使FI下降到（87±22）％（P〈0．01vs①,P〈0．05vs②）;④预先以1×10^-5mol·L^-1的Sq22536孵育,再加入2×10^-8mol·L^-1AngⅡ和1×10^-7mol·L^-1的Ghrelin,胞内FI为原来的（143±24）％（P〈0．01vs②）。结论Ghrelin能够降低AngⅡ引起的大鼠胸主动脉VSMCs胞内钙离子升高作用,其机制可能与激活胞内cAMP／PKA信号通路有关。     

胃癌组织中G9a 表达的预后意义及其对胃癌细胞增殖和凋亡的影响

目的：探究组蛋白甲基转移酶G9a 在胃癌组织中的表达及其与预后的相关性,并观察G9a 抑制剂对胃癌细胞增殖和凋亡的影响。方法：通过Kaplan-Meier Plotter 和Oncomine 数据库分析G9a 在胃癌组织中的表达水平及其与预后的相关性。选用人胃癌细胞株SGC-7901 和MKN-45 为研究对象,Western blotting 方法检测细胞中G9a 蛋白表达水平,以G9a 抑制剂BIX01294处理胃癌细胞,观察细胞形态变化,CCK-8 法和集落形成实验检测胃癌细胞增殖能力和集落形成率的变化,流式细胞术检测细胞凋亡的变化。结果：G9a 在胃癌组织中高表达（P<0.01）,其高表达与预后不良呈正相关（P<0.01）。BIX01294 能使胃癌细胞体积缩小、细胞间连接消失,甚至细胞皱缩、变圆、脱落等。BIX01294 能显著抑制胃癌细胞集落形成和胃癌细胞的增殖（均P<0.05）,同时促进胃癌细胞凋亡（P<0.05）。结论: G9a 在胃癌组织中高表达,其高水平表达与预后不良呈正相关;抑制G9a 的表达可显著抑制胃癌细胞的增殖和促进细胞凋亡。     

Understanding the effect of HF-based wet shallow etching on optical performance of reactive-ion-etched fused silica optics

The optical performance of fused silica optics used in high-power lasers is known to depend not only on their surface damage resistance, but also on their surface quality. Previous studies have shown that good fused silica damage performance and surface quality can be achieved by the use of reactive ion etching (RIE), followed by HF-based wet shallow etching (3 μm). In this study, two kinds of HF-based etchants (aqueous HF and HF/NH₄F solutions) were employed to investigate the effect of HF-based etching on the optical performance of reactive-ion-etched fused silica surfaces at various HF-based shallow etching depths. The results showed that the addition of NH₄F to HF solution makes it possible to produce a high-quality optical surface with a high laser-induced damage threshold, which is strongly associated with the surface roughness and fluorescence defect density. Additionally, changing the HF-based etching depth over the range from 1 μm to 3 μm can affect the surface damage resistance and absorption performance of RIE-treated fused silica. The light-scattering results indicate that the point defect density plays an important role in the determination of the HF-based etching depth. Understanding these trends can enable the advantages of the combined technique of RIE and HF-based etching during the fabrication of high-quality fused silica optics.

The addition of NH₄F to HF solution is important for producing a smooth fused silica surface with good laser damage resistance.     

医疗事故鉴定37例回顾分析

目的通过对37例医疗事故争议的审核和鉴定,探讨争议产生的原因,总结经验教训,真正做到依法行医、依法管理,保证医疗安全。方法共选取2010年本市医疗事故争议37例,其中法院委托13例,卫生行政部门移交10例,医患双方共同委托14例,由本市医学会医疗事故鉴定办公室进行技术鉴定。结果鉴定属于事故的16例,事故率为43.24%。其中一级医疗事故3例,占事故总数的18.75%;二级医疗事故1例,占事故总数的6.25%;三级医疗事故8例,占事故总数的50%;四级医疗事故4例,占事故总数的25%。无证行医未下结论 1例,占争议总数的2.7%。37医疗事故争议议案中,年龄最小的6个月,最大的72岁。其中年龄在20～50岁之间的案例有28例。占75.7%。结论提高医务人员的综合素质以及依法行医、依法管理的能力和水平,是减少和避免医疗事故发生的关键环节。     

药理学教学方法的多元化应用

药理学是医学和药学教育的主干学科,它既是医学与药学的交叉学科,也是基础医学与临床医学的桥梁课程。学生通过学习和掌握药理学的基本理论、基本知识和基本技能,指导临床正确合理用药,从而达到防治疾病的目的。自汕头大学医学院教学改革以来,药理学教研室结合自身经验与条件,在授课过程中应用多元化的教学方法,取得了良好的教学效果。现总结如下。     

韩延华治疗慢性盆腔痛临床经验

介绍韩延华治疗慢性盆腔痛临床经验。认为其病变脏腑责之于肝,主要病机在于气滞血瘀、湿热蕴结、寒湿凝滞、脏腑虚弱,关键在于"血瘀"。治以活血化瘀、行气止痛,强调疏肝理气药与活血药配伍,多用经验方韩氏妇炎汤。并举验案1则。     

N-n-butyl haloperidol iodide protects cardiomyocytes against hypoxia/reoxygenation injury by inhibiting autophagy

N-n-butyl haloperidol iodide (F₂), a novel compound derived from haloperidol, protects against the damaging effects of ischemia/reperfusion (I/R) injury in vitro and in vivo. In this study, we hypothesized the myocardial protection of F₂ on cardiomyocyte hypoxia/reoxygenation (H/R) injury is mediated by inhibiting autophagy in H9c2 cells. The degree of autophagy by treatment with F₂ exposed to H/R in H9c2 cell was characterized by monodansylcadaverine, transmission electron microscopy, and expression of autophagy marker protein LC3. Our results indicated that treatment with F₂ inhibited autophagy in H9c2 cells exposed to H/R. 3-methyladenine, an inhibitor of autophagy, suppressed H/R-induced autophagy, and decreased apoptosis, whereas rapamycin, a classical autophagy sensitizer, increased autophagy and apoptosis. Mechanistically, macrophage migration inhibitory factor (MIF) was inhibited by F₂ treatment after H/R. Accordingly, small interfering RNA (siRNA)-mediated MIF knockdown decreased H/R-induced autophagy. In summary, F2 protects cardiomyocytes during H/R injury through suppressing autophagy activation. Our results provide a new mechanistic insight into a functional role of F₂ against H/R-induced cardiomyocyte injury and death.