四川宝兴雉类生态和垂直分布的调查研究

宝兴位于四川盆地西缘山地,境内纵贯世界闻名的大雪山——即夹金山。 自19世纪30年代至20世纪30年代,先后有Verreaux(1838—1871),Geoffroy(1866),David(1871),Seinhoe(1871),Sharpe(1875),David et Oustalet(1877),Oustaler (1891—92),Styan(1899),Laubmann(1920),La Touch(1925—30),Smith(1931—34),Bangs(1932),Seys(1934)等对宝兴进行过调查和采集,而我     

红腹锦鸡和白腹锦鸡卵壳的超微结构

本文报道了锦鸡属——白腹锦鸡和红腹锦鸡卵壳的气孔、外壳膜、锥体层、木栅层的超微结构。并对两者的卵壳进行了比较。     

绿尾虹雉的冬季生态研究

绿尾虹雉（Lophophorus lhuysii）属雉科（Phasianidae）虹雉属（Lophophorus）,是我国特有珍稀雉类,列为国家一类保护动物。我们于1983年起对绿尾虹雉的生态进行专题研究,现根据对绿尾虹雉的野外考察所得,整理成本文。 野外考察的时间、地点、及路线 我们于1983年4月至1984年7月在四川省宝兴县跷碛公社对绿尾虹雉的生态做了四次考察,前后为期近十个月,其中冬季考察时间为1983年12月至1984年1月。     

Minimal role of base excision repair in TET-induced global DNA demethylation in HEK293T cells

Oxidation of 5-methylcytosine by TET family proteins can induce DNA replication-dependent (passive) DNA demethylation and base excision repair (BER)-based (active) DNA demethylation. The balance of active vs. passive TET-induced demethylation remains incompletely determined. In the context of large scale DNA demethylation, active demethylation may require massive induction of the DNA repair machinery and thus compromise genome stability. To study this issue, we constructed a tetracycline-controlled TET-induced global DNA demethylation system in HEK293T cells. Upon TET overexpression, we observed induction of DNA damage and activation of a DNA damage response; however, BER genes are not upregulated to promote DNA repair. Depletion of TDG (thymine DNA glycosylase) or APEX1 (apurinic/apyrimidinic endonuclease 1), two key BER enzymes, enhances rather than impairs global DNA demethylation, which can be explained by stimulated proliferation. By contrast, growth arrest dramatically blocks TET-induced global DNA demethylation. Thus, in the context of TET-induction in HEK293T cells, the DNA replication-dependent passive mechanism functions as the predominant pathway for global DNA demethylation. In the same context, BER-based active demethylation is markedly restricted by limited BER upregulation, thus potentially preventing a disastrous DNA damage response to extensive active DNA demethylation.     

委内瑞拉链霉菌秦岭变种属间接合转移系统的构建及透明颤菌血红蛋白的表达

【目的】构建委内瑞拉链霉菌秦岭变种属间接合转移系统及透明颤菌血红蛋白的表达。【方法】以链霉菌广泛使用的整合型质粒pSET152和复制型pHZ1358为出发质粒,通过供体大肠杆菌(Escherichia coli)ET12567(pUZ8002)进行属间接合转移委内瑞拉链霉菌秦岭变种。【结果】确定了该变种的最佳接合转移条件;通过SOE-PCR(Splicing by overlap extension PCR)技术构建含PermE和vhb结构基因融合片段的整合型表达载体pJD100,转化ET12567(pUZ8002)后属间接合转移委内瑞拉链霉菌秦岭变种。通过PCR和CO结合差光谱验证了vhb基因在委内瑞拉链霉菌秦岭变种中的整合表达。【结论】本文首次探索了委内瑞拉链霉菌秦岭变种接合转移系统,确定了委内瑞拉链霉菌秦岭变种的最佳接合转移条件,并采用基因工程手段使vhb基因在委内瑞拉链霉菌秦岭变种中获得表达。     

一株源于醇化烟叶表面高效降解TSNA 菌株AS97 的分离筛选、鉴定及应用

摘要:【目的】烟草特有亚硝胺(Tobacco-specific nitrosamines,简称TSNA)是烟叶中的主要致癌物质。本研究从筛选建立的特有菌库中发现了1 株可有效降解TSNA 的菌株AS97,并对其进行了鉴定及初步应用研究。【方法】采用富集驯化及选择培养基筛选得到硝酸盐与亚硝酸盐转化能力最强的菌株AS97;根据菌株的形态特征、生理生化特性及16S rRNA 基因序列分析对其进行鉴定;并将AS97 自制发酵液喷施于烟丝表面,确定适宜接种量和发酵条件,采用LC-MS /MS(液相色谱串联质谱)方法检测TSNA 中四种主要成分的含量。【结果】菌株AS97 源于云南玉溪烤烟样品表面,经分析确定其为荧光假单胞菌(Pseudomonas fluorescens,GenBank 登录号:JF449445)。将AS97 自制发酵液以5% 的接种量喷施于烟丝,30℃(相对湿度是60%)条件下发酵10 d 检测烟叶中硝酸盐、亚硝酸盐、TSNA、4-(N-甲基-亚硝基) -1-(3-吡啶基)-1-丁酮(NNK)、N-亚硝基去甲基烟碱(NNN)、N-亚硝基新烟草碱(NAT) 及N-亚硝基假木贼碱(NAB) 的转化率分别达到68. 77%、45. 57%、45. 47%、59. 08%、38. 79%、21. 41% 及11. 76%。相关性分析结果表明烤烟中硝酸盐、亚硝酸盐与TSNA 的含量均呈极显著相关(P＞0.01),进一步证实硝酸盐与亚硝酸盐是TSNA 的主要前体物质。【结论】醇化烟叶表面的荧光假单胞菌AS97 能够显著降低TSNA 的含量。本文首次报道了源于醇化烤烟表面对TSNA 有良好转化能力的Pseudomonas fluorescens。可将其开发成新型微生物制剂,应用于低害卷烟制品的生 产实践中。     

Mechanisms of resistance to decitabine in the myelodysplastic syndrome

Purpose

The DNA methylation inhibitor 5-aza-2′-deoxycytidine (DAC) is approved for the treatment of myelodysplastic syndromes (MDS), but resistance to DAC develops during treatment and mechanisms of resistance remain unknown. Therefore, we investigated mechanisms of primary and secondary resistance to DAC in MDS.

Patients and Methods

We performed Quantitative Real-Time PCR to examine expression of genes related to DAC metabolism prior to therapy in 32 responders and non-responders with MDS as well as 14 patients who achieved a complete remission and subsequently relapsed while on therapy (secondary resistance). We then performed quantitative methylation analyses by bisulfite pyrosequencing of 10 genes as well as Methylated CpG Island Amplification Microarray (MCAM) analysis of global methylation in secondary resistance.

Results

Most genes showed no differences by response, but the CDA/DCK ratio was 3 fold higher in non-responders than responders (P<.05), suggesting that this could be a mechanism of primary resistance. There were no significant differences at relapse in DAC metabolism genes, and no DCK mutations were detected. Global methylation measured by the LINE1 assay was lower at relapse than at diagnosis (P<.05). On average, the methylation of 10 genes was lower at relapse (16.1%) compared to diagnosis (18.1%) (P<.05).MCAM analysis showed decreased methylation of an average of 4.5% (range 0.6%–9.7%) of the genes at relapse. By contrast, new cytogenetic changes were found in 20% of patients.

Conclusion

Pharmacological mechanisms are involved in primary resistance to DAC, whereas hypomethylation does not prevent a relapse for patients with DAC treatment.