Transition between two forms of heterochromatin at plant subtelomeres

The manner of packing of the terminal DNA loci into nucleosomes and higher order structures may strongly influence their functional interactions. Besides the structural flexibility of telomeric DNA sequences, conserved features of their chromatin including short nucleosome phasing (157 bp) and nucleosome sliding have been described previously. To gain a complementary knowledge of subtelomeres, we have analysed the chromatin structure of two subtelomeric tandem repeats from the plant Silene latifolia: X43.1 and 15Ssp. X43.1 shows two distinct nucleosome periodicities – 157 and 188 bp. Preferred positions of its two nucleosomes have been mapped at both low and high resolution and the experimental results correspond to computer-predicted positions. 15Ssp is a newly-discovered sequence showing a telomere-associated position by PCR and a subtelomeric location by pulsed-field gel electrophoresis and fluorescence in situ hybridisation. Its 159 bp sequence unit shows a tandem arrangement and the presence of micrococcal nuclease-hypersensitive sites when either naked DNA or chromatin is digested. Use of a chemical nuclease results in a regular nucleosome ladder of 157 bp periodicity. Moreover, 15Ssp mononucleosomes show instability and absence of specific positioning, features typical for telomeric chromatin. This revised version was published online in July 2006 with corrections to the Cover Date.     

HIV－1Protease在大肠杆菌中的高表达

艾滋病的致病因子为人免疫缺陷病毒。该病毒的蛋白酶在病毒复制和成熟中具有决定性的意义。由于目前国内外尚未获得艾滋病病毒蛋白酶高效表达的重组子及简便的活性检测系统，限制了它的研究与应用。本文将用ＰＣＲ技术修饰的ＨＩＶＰｒ基因克隆入原核高效表达载体ｐＴＴＱ１８的ＥｃｏＲⅠ和ＨｉｎｄⅢ酶切位点之间，并用豆芽核酸酶将ＥｃｏＲⅠ的粘端削平，构建了读框正确的表达载体，ＩＰＴＧ诱导表明，该重组子在大肠杆菌中获得了高表达，激光扫描结果表明：重组的ＨＩＶＰｒ占细菌总蛋白８．９％以上。     

丙型肝炎病毒NS3蛋白单克隆杂交瘤细胞株的建立及初步鉴定

应用国产基因工程表达的丙型肝炎病毒（ＨＣＶ）ＮＳ３区抗原免疫小鼠，然后取其脾细胞与小鼠骨髓瘤细胞系ＳＰ２／０融合，筛选出４株稳定分泌抗ＨＣＶＮＳ３区蛋白单克隆抗体（ＭｃＡｂ）的杂交瘤细胞株，分别命名为２Ｂ６，２Ｆ３，３Ｄ８，３Ｄ９，经初步研究表明这４株单抗与ＮＳ３抗原具有良好的反应性，与ＨＣＶ核心区多肽及乙型肝炎病毒表面抗原和ｅ抗原均无反应。抑制实验表明这４株抗体分别针对ＮＳ３抗原分子上的２个不同的抗原决定簇。     

Thermogenesis due to noradrenaline in muscles under different rates of perfusion

Vascularly isolated hind legs of cold acclimated rats were perfused with arterial blood either without noradrenaline (NA) or with a constant concentration of NA (10 ng·ml^–1) at different perfusion rates ranging from 2 to 14l·g^–1·min^–1. The oxygen consumption of the leg during perfusion both with or without NA was linearly related to the perfusion rate. The linear increase of leg oxygen consumption with respect to the perfusion was steeper after NA, which indicates that the same arterial concentration of NA may produce a greater thermogenic effect at higher blood flow rates (the difference between resting metabolic rate and the thermogenesis stimulated by NA, was 8.20 l O₂·g^–1·h^–1 at a blood flow of 3l·g^–1·min^–1, compared with 45.02 l O₂·g^–1·h^–1 at a blood flow of 14 l·g^–1·min^–1). These data confirm the important role of the extravascular influx rate of NA in the control of thermogenesis due to NA in muscles.     

Partial purification and characterization of anhydrotetracycline oxygenase of Streptomyces aureofaciens

Anhydrotetracycline oxygenase was purified both by affinity chromatography and by hydrophobic interaction chromatography. Molecular weight of anhydrotetracycline oxygenase was determined to be 115,000 by Sephadex G-200 gel filtration. Using preparative isoelectric focusing the isoelectric point of the enzyme was estimated to be 5.3. The enzyme showed a sensitivity to thiol-specific inhibitors. During the hydrophobic interaction purification step, the activity dropped considerably. Reactivation occurred when a heat treated crude extract was added to the reaction mixture.     

Structure-intestinal transport and structure-metabolism correlations of some potential cancerostatic pyrimidine nucleosides in isolated rat jejunum

Summary Both transport and biotransformation processes for a series of pyrimidine nucleobases, ribonucleosides, 2-deoxyribonucleosides, and acetyl and 5-substituted derivatives of the cancerostatic agent araC were studied in the isolated everted rat jejunum with a continuous perfusion technique. Metabolic alterations during penetration were assessed by HPLC. 5-Halogeno and 5-deoxy derivatives of cytosine nucleosides exhibited higher transport rates and higher stability towards the deamination reaction than did unsubstituted derivatives. Octanol-buffer partition coefficients were estimated for the study compounds, and fragmental constants for the sugar moieties of nucleosides were assessed. With the present study compounds there was no correlation between lipophilicity and transport rate, as previously reported, but there was a correlation between lipophilicity and metabolic alteration of araC derivatives (r=0.99, n=5).     

2005-2019年理塘县法定传染病疫情分析

目的了解理塘县近15年法定传染病疫情形势及流行特征,为政府制定防控措施提供科学依据。方法对2005—2019年理塘县法定传染病疫情进行描述性流行病学分析。采用ArcGIS 10.3软件绘制各乡镇发病情况分布图,SPSS 21.0软件进行χ²检验、趋势性χ²检验。结果2005—2019年理塘县共计报告甲乙丙类传染病21种6154例,年均发病率为644.33/10万,发病呈上升趋势。死亡37例,年均死亡率3.87/10万,病死率0.60%。呼吸道传染病发病最高(341.12/10万);发病前3位的病种为肺结核(271.91/10万)、乙肝(103.24/10万)及包虫病(67.22/10万);肺结核、其他感染性腹泻病、艾滋病/HIV、梅毒发病呈上升趋势。3月、9月分别出现1次发病高峰;20~29岁、30~39岁和10~19岁组发病居前3位;男女性别比为1.24∶1;发病以农民、牧民及学生为主。结论2005-2019年理塘县法定传染病发病率较高且呈上升趋势,应针对高发传染病、上升趋势明显的传染病、重点人群进行分析研究,采取针对性措施控制疫情。     

生物医学科技论文存在的利益冲突问题及其应对措施

【目的】 探讨生物医学科技论文存在的主要利益冲突(Conflict of Interest, COI)问题及其应对措施。【方法】 通过检索Retraction Watch 数据库,收集2016—2021年生物医学期刊中因COI相关问题被撤销、更正或关注的95篇论文为研究对象。回顾性调查论文及其处理(撤稿、更正或关注)声明的主要特征、存在的COI问题及处理措施。【结果】 本研究纳入的95篇论文中,72篇被撤销,23篇被更正或关注。论文存在的主要COI问题包括COI披露不完整(46.3%)、确实存在COI(18.9%)、对已披露COI的完整性存在质疑(12.6%)、潜在的COI披露不完整(12.6%)、COI披露错误(5.3%)等;具体COI表现为作者与企业(42.1%)、其他研究者(9.7%)、其他作者(7.0%)、研究机构(6.1%),以及期刊编辑或审稿人(5.3%)等之间存在的潜在COI或COI。【结论】 生物医学期刊论文发表过程中存在多种COI问题,并且表现形式多样。建立并完善COI相关编辑政策,可预防COI相关问题的发生,从而减少发表偏倚。