Repair of ochratoxin A-induced DNA damage and modulation of OTA-related genotoxicity by co-incubation with bile acids and methotrexatein vitro

The mycotoxin ochratoxin A (OTA) induced DNA strand breaks in porcine urinary bladder epithelial cells (PUBEC) and in Madin Darby canine kidney (MDCK) cells. A co-incubation with bile acids or methotrexate reduced or even prevented this adverse effect of OTAin vitro. The protective effect is possibly attributable to a decreased OTA uptake in cells, since bile acids and methotrexate are known to share common transport systems such as organic anion transporters (OAT) and/or organic anion transporting polypeptides (OATP) with the mycotoxin. OTA uptake in cells and its modulation can be one factor which determines the extent of adverse effects in different cell types. Another aspect of interest in this regard relates to repair of DNA damage: PUBEC cells are sensitive to OTA-induced damage which is more pronounced when DNA repair is blocked (by cytosine β-D-arabino-furanosid/hydroxyurea). On the other hand, when cells are kept in fresh (toxin-free) medium for 3 h, OTA-induced DNA damage decreased to control levels. Presented at the 26^th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004     

基于分子模拟的离子交换层析中静电相互作用研究

将分子模拟方法引入到蛋白质离子交换层析中的静电相互作用研究。选用蛋清溶菌酶和牛胰凝乳蛋白酶为模型蛋白质,阳离子交换吸附剂SP Sepharose FF等为模型层析介质。从蛋白质数据库(PDB)中获得蛋白质三维结构数据,分析了介质孔径和配基分布,以点电荷模拟离子交换层析介质的功能配基,构筑了蛋白质-介质配基模拟表面体系。采用MCCE、Delphi和GRASP等程序包进行了分子模拟计算,考察了作用方向、作用距离、盐浓度、pH等对蛋白质和模拟配基平面间静电相互作用的影响。结果表明,宏观的层析平衡常数与微观分子模拟计算的相互作用能量参数间存在良好的线性关系。     

蔓越橘的营养成分及其药理作用研究综述

蔓越橘中含有多种酚类物质,具有预防尿路感染复发、清除自由基、促进心血管健康等独特的保健功效,本文就其在抑制细菌黏附、抗氧化、抗肿瘤等方面的药理作用及部分作用机理进行综述。     

Identification of cDNAs encoding pterocarpan reductase involved in isoflavan phytoalexin biosynthesis in Lotus japonicus by EST mining

Isoflavans and pterocarpans are the major biosynthetically connected phytoalexins in legumes. A search of the expressed sequence tag library of a model legume Lotus japonicus, which produces an (-)-isoflavan, for homologs of phenylcoumaran benzylic ether reductase catalyzing the reductive cleavage of dihydrofurans, yielded seven full-length cDNAs, and the encoded proteins were analyzed in vitro. Four of them cleaved the dihydrofuran of a pterocarpan medicarpin to yield an isoflavan (-)-vestitol and were designated pterocarpan reductase (PTR). Two PTRs displayed enantiospecificity to (-)-medicarpin, representing genuine L. japonicus PTRs, while the other two lacked enantiospecificity and were presumed to be evolutionarily primitive types.     

Ab initio computational insight into the ion-pair SN2 reaction of lithium isothiocyanate and methyl fluoride in the gas phase and in acetone solution

The ion-pair S_N2 reaction LiNCS + CH₃F with two mechanisms, inversion and retention, was investigated at the MP2(full)/6-311+G**//HF/6-311+G** level in the gas phase and in acetone solution. All HF-optimized structures were confirmed by vibrational frequency analysis. Based on IRC analyses, eight possible reaction pathways in the title reaction are proposed. The inversion mechanism through a six-membered-ring transition-state structure is the most favorable. Methyl thiocyanate should form preferentially in the gas phase and the more stable methyl isothiocyanate will be the main product in CH₃COCH₃. The retardation of the reaction in CH₃COCH₃ solution was attributed to the differences in the solvation free energies in the separated reactants and transition structures. All of the theoretical results are consistent with the experiment.     

Glycosylation of the two <Emphasis Type="Italic">O</Emphasis>-glycosylated domains of human MUC2 mucin in patients transposed with artificial urinary bladders constructed from proximal colonic tissue

Transposition of intestinal segments is frequently used for bladder reconstruction. Following transposition, bowel segments continue to produce mucus and a correlation between excessive mucus production and complications such as urinary tract infection or catheter blockage has been observed for a long time. However, no information is currently available on the change of mucin expression and glycosylation under these abnormal conditions. In this study, the variable number tandem repeat region and the irregular repeat domain of human MUC2 were isolated as two glycopeptide populations after reduction and trypsin digestion followed by gel chromatography from urine of patients transposed with urinary bladders. After alkaline borohydride treatment, the oligosaccharides released from the whole MUC2 mucin and the two glycosylated domains were investigated by nanoESI Q-TOF MS/MS (electrospray ionization quadrupole time-of-flight tandem mass spectrometry). More than 60 different glycans were identified, mainly based on sialylated core 3 structures. Some core 1, 2 and 4 oligosaccharides were also found. Most of the structures were acidic with NeuAc residues mainly α2–6 linked to the N-acetylgalactosaminitol and sulphate residues exclusively 3-linked to galactose. No expression of blood group A and B or Sda/Cad determinants was observed. Similar patterns of glycosylation were found in the tandem repeat region and the irregular repeat domain and the level of expression of the major oligosaccharides were in the same order of magnitude. The most interesting feature of this study was that sialyl-Tn antigen, which is considered as a tumour antigen, was the oligosaccharide most highly expressed. This result suggests that mucins from intestinal transposed segments are abnormally glycosylated.     

探讨UF-100在泌尿系统感染诊断中的应用价值

为探讨UF-100尿液分析在泌尿系统感染诊断中的临床应用价值,对UF-100作重复性试验,用UF- 100检测760份尿中细菌和白细胞,同时作定量细菌培养并将结果作比较。用Yerushalmy模式评价2种方法的一致性及UF-100筛检的灵敏度、特异性等。重复试验中,UF-100细菌计数CV值低于细胞计数CV,与定量细菌培养结果比较,细菌计数的筛检灵敏度为80.0%,特异性为50.4%,阳性预计值为28.7%,阴性预计值为91.0%,假阳性率为39.7%,假阴性率为4.0%,准确率为56.3%。UF-100具有良好的分析尿液的性能,在临床尿路感染筛检时可用细菌一项指标,90%结果阴性的标本可在短时间内筛去,大大减少实验人员繁复劳动,降低检验成本,但应注意假阴性,更不可替代尿定量细菌培养。     

化湿液对湿阻证大鼠下丘脑AchE、NOS活性及NO含量的影响

目的研究化湿液对湿阻证模型大鼠下丘脑AchE、NOS活性及NO含量的影响。方法将50只SD大鼠随机分为正常组、模型组及模型组 化湿液低、中、高剂量组,每组10只。除正常组外,其余4组用改进后的环境加疲劳法制造湿阻证模型,连续造模6d。造模成功后,正常组和模型组大鼠按2ml/100g的剂量灌胃给予生理盐水;化湿液低、中、高剂量组分别按含生药0.4g/100g、0.8g/100g、1.6g/100g的剂量灌胃给予化湿液。每天1次,连续8d。取大鼠下丘脑,检测下丘脑AchE、NOS活性及NO含量。结果与正常组比较,模型组大鼠下丘脑AchE活性明显升高,NOS活性及NO含量明显降低(P<0.05);与模型组比较,化湿液可降低湿阻证模型大鼠下丘脑AchE的活性,提高下丘脑NOS活性及NO含量(P<0.05)。结论化湿液具有改善湿阻证大鼠下丘脑AchE、NOS活性及NO含量的作用,对研究化湿液治疗湿阻证的机制有一定价值。     

Functional role of DNRA and nitrite reduction in a pristine south Chilean <Emphasis Type="Italic">Nothofagus</Emphasis> forest

Nitrite (NO₂ ⁻) is an intermediate in a variety of soil N cycling processes. However, NO₂ ⁻ dynamics are often not included in studies that explore the N cycle in soil. Within the presented study, nitrite dynamics were investigated in a Nothofagus betuloides forest on an Andisol in southern Chile. We carried out a ¹⁵N tracing study with six ¹⁵N labeling treatments, including combinations of NO₃ ⁻, NH₄ ⁺ and NO₂ ⁻. Gross N transformation rates were quantified with a ¹⁵N tracing model in combination with a Markov chain Monte Carlo optimization routine. Our results indicate the occurrence of functional links between (1) NH₄ ⁺ oxidation, the main process for NO₂ ⁻ production (nitritation), and NO₂ ⁻ reduction, and (2) oxidation of soil organic N, the dominant NO₃ ⁻ production process in this soil, and dissimilatory NO₃ ⁻ reduction to NH₄ ⁺ (DNRA). The production of NH₄ ⁺ via DNRA was approximately ten times higher than direct mineralization from recalcitrant soil organic matter. Moreover, the rate of DNRA was several magnitudes higher than the rate of other NO₃ ⁻ reducing processes, indicating that DNRA is able to outcompete denitrification, which is most likely not an important process in this ecosystem. These functional links are most likely adaptations of the microbial community to the prevailing pedo-climatic conditions of this Nothofagus ecosystem.