人白细胞介素-24治疗人宫颈癌荷瘤裸鼠的实验研究

目的探讨人白细胞介素(hIL)-24基因重组质粒对人宫颈癌Siha细胞裸鼠移植瘤生长的抑制作用及其作用机制。方法建立荷宫颈癌Siha细胞裸鼠移植瘤模型,15只裸鼠随机分为3组:白细胞介素(IL)-24重组质粒组,空质粒组,磷酸盐缓冲液(PBS)组,根据肿瘤体积的生长情况绘制肿瘤生长曲线;处死裸鼠后切取瘤体并称质量,计算肿瘤抑制率;用流式细胞仪检测细胞周期。结果体内实验表明,IL-24重组质粒能够抑制肿瘤的生长,IL-24重组质粒组移植瘤的体积明显小于空质粒组和PBS组(P<0.05),空质粒组和PBS组移植瘤体积则差异无统计学意义(P>0.05)。IL-24重组质粒组抑瘤效果显著,其抑瘤率为56.5%,差异有统计学意义(P<0.05),空质粒组抑瘤率为1.3%,差异无统计学意义(P>0.05)。经流式细胞术检测,与空质粒组和PBS组比较,IL-24重组质粒组G0/G1期细胞增多(P<0.05),S期细胞减少,G2/M期细胞减少(P<0.05),细胞被阻滞在G0/G1期,空质粒组和PBS组则差异无统计学意义(P>0.05)。结论于荷瘤裸鼠的瘤内注射IL-24重组质粒可抑制肿瘤生长,提示IL-24具有明显的体内抗肿瘤作用。     

烧伤病房鲍氏不动杆菌质粒介导的16S rRNA甲基化酶基因及耐药性传递研究

目的 调查烧伤病房鲍氏不动杆菌临床分离株的耐药性,了解是否存在介导高水平氨基糖苷类抗菌药物耐药的16S rRNA甲基化酶基因,探讨传播机制.方法 收集2006年5月-2007年12月从甘肃省人民医院烧伤病房分离的40株鲍氏不动杆菌.采用纸片扩散法测定其对20种抗菌药物的敏感性;琼脂稀释法测定其对阿米卡星、庆大霉素、妥布霉素、奈替米星、异帕米星和卡那霉素6种氨基糖苷类抗菌药物MIC;PCR扩增5种甲基化酶基因armA、rmtA、rmtB、rmtC、rmtD;阳性PER产物纯化测序;碱裂解法提取质粒;接合实验及质粒转化实验确定耐药性传递方式.结果 40株鲍氏不动杆菌对6种氨基糖苷类抗菌药物的耐药率分别为72.5%、72.5%、70.0%、67.5%、70.0%、70.0%;对6种氨基糖苷类抗菌药物全部耐药的菌株有25株占62.5%,其中armA基因阳性10株占40.0%,未检出rmtA、rmtB、rmtC、rmtD阳性菌株.10株转化子、10株接合子对氨基糖苷类抗菌药物均高度耐药,MIC≥256 μg/mL者全部携带armA基因.结论 烧伤病房鲍氏不动杆菌临床分离株耐药率极高,从中检出16S rRNA甲基化酶基因armA且位于质粒染色体上.     

变异链球菌葡糖基转移酶植物表达质粒p2355-gtfB的构建

目的构建含变异链球菌葡糖基转移酶多个免疫显性抗原表位的植物表达质粒p2355-gtfB,为其转化植物研究奠定物质基础,为可食防龋疫苗研究提供条件。方法以真核表达质粒pcDNA3-gtfB为模板,通过聚合酶链反应(polymerase chain reaction,PCR)扩增含编码变异链球菌葡糖基转移酶抗原表位的目的基因gtfB。将回收纯化的PCR产物经T-A克隆技术克隆于中间载体pMD18-T,双酶切鉴定插入方向后,将目的基因从中间载体释放,再克隆至高效的植物表达载体p2355,用电转化法转化根癌农杆菌EHA105,对重组质粒阳性克隆株进行筛选与鉴定。结果通过对重组质粒T-gtfB进行酶切图谱分析,获得2.9 kb和3.7 kb的2个片断,将重组质粒p2355-gtfB进行酶切、PCR及测序分析,显示p2355-gtfB中插入基因长度为3 675 bp,基因序列与双脱氧链终止法的测定结果相同,证明植物表达质粒p2355-gtfB构建成功,开放阅读框架正确。结论本研究成功构建了含变异链球菌多个葡糖基转移酶免疫显性抗原表位编码基因的植物表达质粒p2355-gtfB,为可食性防龋疫苗的研究奠定了基础。     

大鼠细胞因子信号转导抑制因子-1基因的原核克隆表达和免疫学分析

目的 克隆表达大鼠细胞因子信号转导抑制因子-1基因(SOCS-1).方法 将大鼠SOCS-1全长编码基因的PCR产物,克隆到原核表达质粒pET-28a(+)中,构建重组质粒pET-28a(+)-ratSOCS-1.转化大肠埃希菌BL-21/DE3,用异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达,应用镍离子金属螯合剂亲和层析柱从表达产物中纯化重组蛋白,通过十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)对表达产物和重组蛋白进行鉴定.应用纯化的重组蛋白免疫新西兰大白兔,抗体滴度达到1:10000以上后进行末次免疫,2周后心脏取血、测定滴度,分离制备免疫血清.用红细胞裂解法制备大鼠外周血白细胞裂解全蛋白.将阴性血清(未用重组蛋白免疫的新西兰大白兔的血清)、免疫血清及兔抗组氨酸标签抗体转入各蛋白条带,用Western免疫印迹检测重组蛋白的免疫学活性.结果 PCR、双酶切及DNA测序分析均表明重组质粒pET-28a(+)-ratSOCS-1构建成功.SDS-PAGE结果可见转化了重组质粒的大肠埃希菌全菌和经超声裂解后的菌体沉淀的样品均在相对分子质量约26 000处有一明显的蛋白条带,经亲和层析获得的纯化重组蛋白有特异的单一条带与上述条带一致,而在超声裂解后的菌体上清中相同位置却未见有蛋白表达条带.Western免疫印迹表明重组蛋白、大鼠外周血白细胞裂解蛋白中相对分子质量约24000的蛋白条带、兔抗组氨酸标签抗体均可被免疫血清识别,分别出现清晰的相对分子质量26000、24 000、26000的反应条带,表明其具有免疫活性.结论 SOCS-1基因可以在大肠埃希菌BL-21/DE3中获得表达,其纯化重组蛋白具有良好的抗原性和免疫活性.     

Characterization of plasmids encoding CMY-2 AmpC β-lactamases from Escherichia coli in Canadian intensive care units

The dissemination of CMY-2 AmpC β-lactamases among Escherichia coli in Canadian intensive care units occurs through a combination of clonal spread of virulent strains and the horizontal transfer of genetically similar IncI1, IncA/C, and IncK/B plasmids.     

福氏2a志贺菌菌痢爆发的质粒DNA多态性分析

目的对福氏2a志贺菌质粒DNA进行基因分型,提高福氏2a志贺菌菌痢爆发流行时同源克隆的鉴定水平。方法对8株福氏2a志贺菌进行质粒图谱及质粒限制性酶切图谱分析。结果此次菌痢爆发期间分离的8株福氏2a志贺菌具有两种不同的质粒图谱特征(PPⅠ、PPⅡ型),其中2株病例密切接触者分离株J98101(PPⅡ型)和J9826(PPⅠ型)分属不同克隆。除上述两种质粒图谱特征外,同属PPⅠ型质粒图谱特征的J9871具有独特的质粒限制性酶切图谱特征ReⅢ型。结论本次爆发偶合有部分散发病例。相对于传统表型分型方法(生化反应、血清型)而言,质粒DNA分析具有更高的分辨率,它提供的遗传学信息更为丰富、直接、精细。     

Codon usage is imposed by the gene location in the transcription unit

Summary In CYH2/cyh2 heterozygous diploids of the yeast Saccharomyces cerevisiae resistance is dominant over sensitivity at low (0.5–5 g/ml) cycloheximide (cyh) concentrations. The cyh-resistant haploid strain MMY1 confers relatively high (10 g/ml) cyh-resistance to heterozygous diploids constructed by mating this strain with cyh-sensitive haploid strains. We present here a genetic and biochemical study of strain MMY1. Analysis of tetrads obtained from a MMY1 heterozygous diploid showed that two unlinked nuclear mutations, determining high-and low-cycloheximide resistance, were present in MMY1. From a genomic library of this strain, constructed in vector YCp50, two plasmids (pRC1 and pRC13) have been isolated which, respectively, confer high-and low-resistance phenotypes to cyh-sensitive S. cerevisiae strains. The restriction maps of pRC1 and pRC13 are totally unrelated. This finding suggests that the genes harboring the two mutations encoding cyh-resistance from MMY1 were cloned in plasmids pRC1 and pRC13, respectively. Pulse field gel electrophoresis showed that the DNA insert of pRC1 maps at either chromosome VII or XV, whereas that from pRC13 maps at chromosome XI. This latter gene appears to define a previously unreported locus and has been named cyh5. By restriction and nucleotide sequencing analysis, the cyh gene present in pRC1 has been shown to correspond to cyh2, which maps at chromosome VII. These results suggest that the dominant cyh-resistance phenotype conferred by MMY1 in heterozygous diploids is promoted by the presence of both cyh2 and cyh5. A 2.3 kb NcoI fragment, containing cyh2 from pRC1, has been inserted in vectors YCp50, YEp13 and YIp5. By selecting at discriminating cyh concentrations, the resulting constructs efficiently transform a variety of haploid and diploid yeasts of both laboratory and industrial origin.     

问号赖型钩端螺旋体重组质粒pDL121及其表达产物的初步研究

目的:探讨问号赖型钩端螺旋体重组质粒pDL121外源基因及其表达产物23 kDa蛋白的特点。方法:用6种内切酶对pDL121行酶谱分析,用Digoxin标记的pDL121外源基因片段作探针对不同种属的钩体进行杂交,用SDS-PAGE制备23 kDa蛋白,Western blot鉴定其免疫原性。结果:pDL121外源基因没有6种内切酶的酶切位点,重组探针与致病性钩体(serovar lai strain 017,serovar hebdomadis strain56610,serovar pomona strain 56608)有杂交信号,与非致病性钩体(serovar patoc strain Patoc I,serovar illini strain 3055)无杂交信号,亦不识别大肠杆菌。23 kDa兔抗血清可识别pDL121体外表达的23 kDa蛋白带和赖型钩体017株超声抗原成份;其抗体滴度为1/12800;用pDL121细菌裂解液主动免疫豚鼠,可使豚鼠抵抗强毒力株钩体攻击。结论:pDL121外源基因可能是赖型钩体的一个新基因;该重组探针能鉴别致病性钩体和非致病性钩体;23 kDa抗原有良好的免疫原性,可能是赖型钩体017株的保护性抗原。     

Yersinia pestis antibiotic resistance: a systematic review

Yersinia pestis, the cause of plague and a potential biological weapon, has always been a threatening pathogen. Some strains of Y. pestis have varying degrees of antibiotic resistance. Thus, this systematic review was conducted to alert clinicians to this pathogen’s potential antimicrobial resistance. A review of the literature was conducted for experimental reports and systematic reviews on the topics of plague, Y. pestis, and antibiotic resistance. From 1995 to 2021, 7 Y. pestis isolates with 4 antibiotic resistance mechanisms were reported. In Y. pestis 17/95, 16/95, and 2180H, resistance was mediated by transferable plasmids. Each plasmid contained resistance genes encoded within specific transposons. Strain 17/95 presented multiple drug resistance, since plasmid 1202 contained 10 resistance determinants. Strains 16/95 and 2180H showed single antibiotic resistance because both additional plasmids in these strains carried only 1 antimicrobial determinant. Strains 12/87, S19960127, 56/13, and 59/13 exhibited streptomycin resistance due to an rpsl gene mutation, a novel mechanism that was discovered recently. Y. pestis can acquire antibiotic resistance in nature not only via conjugative transfer of antimicrobial-resistant plasmids from other bacteria, but also by gene point mutations. Global surveillance should be strengthened to identify antibiotic-resistant Y. pestis strains by whole-genome sequencing and drug susceptibility testing.