Site-directed mutagenesis studies on the L-arginine-binding sites of feedback inhibition in N-acetyl-L-glutamate kinase (NAGK) from Corynebacterium glutamicum

Arginine biosynthesis in Corynebacterium glutamicum proceeds via a pathway that is controlled by arginine through feedback inhibition of NAGK, the enzyme that converts N-acetyl-l-glutamate (NAG) to N-acety-l-glutamy-l-phosphate. In this study, the gene argB encoding NAGK from C. glutamicum ATCC 13032 was site-directed, and the l-arginine-binding sites of feedback inhibition in Cglu_NAGK are described. The N-helix and C-terminal residues were first deleted, and the results indicated that they are both necessary for Cglu_NAGK, whereas, the complete N-helix deletion (the front 28 residues) abolished the l-arginine inhibition. Further, we study here the impact on these functions of 12 site-directed mutations affecting seven residues of Cglu_NAGK, chosen on the basis of homology structural alignment. The E19R, H26E, and H268N variants could increase the I_0.5 ^R 50–60 fold, and the G287D and R209A mutants could increase the I_0.5 ^R 30–40 fold. The E281A mutagenesis resulted in the substrate kinetics being greatly influenced. The W23A variant had a lower specific enzyme activity. These results explained that the five amino acid residues (E19, H26, R209, H268, and G287) located in or near N-helix are all essential for the formation of arginine inhibition.     

截头堆砂白蚁性比的研究

为了解截头堆砂白蚁Cryptotermes domesticus（Haviland）群体中不同品级、不同虫态的雌雄性比,本文研究了该种白蚁自行配对室温条件下饲养4年巢龄的实验群体与采集的自然群体的各个品级和不同虫态的雌雄性比。结果表明：自行配对室温饲养4年巢龄群体与自然环境群体中原始繁殖蚁、幼蚁、若蚁、兵蚁都有雌雄之分,其中自行配对室温饲养群体的原始繁殖蚁雌雄比例为1：1,兵蚁雌雄比例为1：1．24,幼蚁和若蚁雌雄比例为1：1．46;自然环境群体原始繁殖蚁雌雄比例为1：1,兵蚁雌雄比例为1：1．15,幼蚁和若蚁雌雄比例为1：1．43。     

Biological Characteristics and Effect of Human Umbilical Cord Mesenchymal Stem Cells (hUC-MSCs) Grafting with Blood Plasma on Bone Regeneration in Rats

We evaluated the biological characteristics/effect of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) grafting with blood plasma on bone regeneration in rat tibia nonunion. SD rats (142) were randomly divided into four groups: fracture group (positive control); nonunion group (negative control); hUC-MSCs grafting with blood plasma group; and hUC-MSCs grafting with saline group. Rats were administered tetracycline (30 mg/kg) and calcein blue (5 mg/kg) 8 days before killing. The animals were killed under deep anesthesia at 4 and 8 weeks post fracture for radiological evaluation and histological/immunohistological studies. The hUC-MSCs grafting with blood plasma group was similar to fracture group: the fracture line blurred in 4 weeks and disappeared in 8 weeks postoperatively. Histological/immunohistological studies showed that hUC-MSCs were of low immunogenicity which merged in rat bone tissue, differentiated into osteogenic lineages, and completed the healing of nonunion. After stem cell transplantation, regardless of whether plasma or saline was used, new multi-center bone formation was observed; fracture site density was better in stem cell grafting with blood plasma group. We, therefore, concluded that the biological characteristics of hUC-MSCs-treated nonunion were different from the standard fracture healing process, and the proliferative and localization capacity of hUC-MSCs might benefit from the use of blood plasma.     

HDACs的统计偶联分析

组蛋白去乙酰化酶HDACs是调控基因的关键蛋白酶。基于生物信息学中的统计偶联分析方法,构建了统计偶联分析平台。基于该平台对HDACs进行了统计偶联分析。预测了HDAC8中关键氨基酸位点以及和H143偶联的氨基酸位点,有利于人们更深入地认识HDACs的结构和功能,为HDACs抑制剂的研究提供新的思路。     

不同温度处理对虎耳草叶片气体交换及叶肉结构的影响

在人工气候箱中对盆栽虎耳草进行处理,测定不同温度条件下虎耳草叶片光合特征、叶绿素含量、抗氧化酶活性、叶肉结构等生理形态指标。结果表明：低温处理后,虎耳草叶片净光合速率、气孔导度下降迅速,叶绿素含量最少,SOD、CAT活性最低,MDA含量最高,栅栏组织排列更紧密,移置正常温度下,光合速率能在短时间内恢复;高温处理的净光合速率下降速度不及低温处理,但叶片海绵组织显著增加,光合速率恢复较慢。     

牙周炎动物模型的研究进展

牙周炎是常见的口腔慢性疾病,是造成中国成年人失牙的最重要原因。为进一步探讨牙周炎的发病机制、病理学特点,以便更好的制定治疗方案,动物模型被广泛应用。本文从牙周炎动物模型建立方法和实验动物的选择等方面,对牙周炎动物模型的研究进展做一综述。     

分枝PEI 修饰的PLGA 纳米粒转染DNA 的研究*

目的:建立基于聚(乳酸-羟基乙酸)纳米粒(PLGA)载DNA的基因转染体系,比较用空白聚(乳酸-羟基乙酸)纳米粒(PLG-A-E)吸附质粒DNA和用分枝PEI修饰后的PLGA纳米粒(PLGA-BPEI)吸附质粒DNA优缺点。方法:用乳化蒸发法制备纳米粒,对纳米粒进行表征研究,包括包封率、Zeta电位、粒径大小、稳定性,用荧光显微镜观察它们对NIH3T3和HEK293细胞的转染效率,用MTT检测对它们细胞的毒性。结果:制备了两种基于PLGA的纳米粒,PLGA-E和PLGA-BPEI粒径大小为200-270nm,zeta电位为0-30mV,在血清和不同的pH值时两者均较稳定,转染效率PLGA-BPEI较PLGA-E高,且释放时间早,但前者较后者对细胞毒性大。结论:这两种基于PLGA纳米粒均能有效转染质粒DNA,它们存在不同的优缺点,应根据不同需要进行选择。     

小潮气量通气对严重胸外伤所致急性呼吸窘迫综合征的疗效观察

目的:探讨小潮气量(LTV)加呼气末正压(PEEP)通气模式(MV)治疗严重胸外伤所致急性呼吸窘迫综合征(ARDS)的疗效,提高重症胸外伤救治的成功率;方法:以29例小潮气量(5～8 mL/kg)加用PEEP的MV为观察组,25例常规潮气量(8～12mL/Kg)MV为对照组,比较两组血气、血液动力学指标、脱机时间;结果:观察组SaO2高于对照组(P＜0.05);观察组出现4例VILI,对照组出现9例VILI,减少了VILI的发生(P＜0.05),观察组死亡2例,平均脱机时间7.25天;对照组死亡4例,平均脱机时间10.45天.结论:采用小潮气量加PEEP的MV治疗,配合规范的护理措施,可以有效提高严重胸外伤致ARDS的治疗效果.     

右侧输卵管同时合并左侧卵巢妊娠一例暨文献复习

目的:总结输卵管合并卵巢妊娠的诊治经验教训和治疗方法。方法:回顾性分析我院2010年11月9日入院右侧输卵管同时合并左侧卵巢妊娠患者临床资料,B超检查,急诊腹腔镜探查术并送病理组织检查。结果:行右侧输卵管切除术+左侧卵巢囊肿剥除术+粘连分解术后病检结果为:(右输卵管)腔内变性绒毛及滋养细胞,符合异位妊娠;(左卵巢囊肿)羊膜、绒毛及滋胚叶细胞,符合异位妊娠。术后3、6和8天患者血HCG浓度水平分别为19.61ng/ml、4.47ng/ml和1.84ng/ml,术后顺利恢复出院。结论:输卵管合并卵巢妊娠发生较为罕见,极易漏诊和误诊,及时行腹腔镜探查术是有效的诊治手段。     

C- 反应蛋白检测在胎膜早破孕妇中的临床意义

目的:探讨C反应蛋白(CRP)检测在足月胎膜早破(PROM)孕妇中的临床意义。方法:选取足月胎膜早破(PROM)孕妇50例为实验组,并根据破膜时间将足月破膜孕妇分为3个亚组;并选取同期住院的正常孕妇30例为对照,采用高敏CRP试剂盒,测定不同组别孕妇中CRP水平。结果:入院时,胎膜早破各亚组中CRP水平明显高于对照组,具有显著统计学意义(P<0.05);同时随着破膜时间的增加,各亚组中的CRP水平及WBC计数也逐渐升高,且3个亚组之间也分别存在统计学差异(P<0.05)。在应用抗生素3d后,CRP出现显著下降,与正常组相比未见明显差异(P>0.05);WBC计数在应用抗生素后的3d时间出现下降,但与入院前相比未见明显统计学差异。结论:CRP检测在判断孕妇胎膜早破、指导临床用药方面具有较高的临床价值,可作为常规检查项目。