Herbicide Phosphinothricin Causes Direct Stimulation Hormesis

Herbicide phosphinothricin (PPT) inhibits glutamine synthetase (GS), a key enzyme in nitrogen assimilation, thus causing ammonia accumulation, glutamine depletion and eventually plant death. However, the growth response of Lotus corniculatus L. plants immersed in solutions with a broad range of PPT concentrations is biphasic, with pronounced stimulating effect on biomass production at concentrations ≤ 50 μM and growth inhibition at higher concentrations. The growth stimulation at low PPT concentrations is a result of activation of chloroplastic isoform GS2, while the growth suppression is caused by inhibition of both cytosolic GS1 and GS2 at higher PPT concentrations. Since the results are obtained in cell-free system (e.g. protein extracts), to which the principles of homeostasis are not applicable, this PPT effect is an unambiguous example of direct stimulation hormesis. A detailed molecular mechanism of concentration-dependent interaction of both PPT and a related GS inhibitor, methionine sulfoximine, with GS holoenzymes is proposed. The mechanism is in concurrence with all experimental and literature data.     

Assessment of pre- and post-methionine load homocysteine for prediction of recurrent stroke and coronary artery disease in the Vitamin Intervention for Stroke Prevention Trial

Methionine (Met) loading increases total plasma homocysteine (tHcy) and assesses homocysteine metabolism. We tested the hypothesis that pre- or post-Met tHcy will predict recurrent stroke or coronary artery disease (CAD) in a subgroup analysis of the Vitamin Intervention for Stroke Prevention (VISP) trial. VISP subjects with non-disabling stroke underwent measurement of tHcy at baseline (fasting pre- and post-Met load) and were randomized to high/low-dose B-vitamin therapy for prevention of recurrent stroke or CAD. In the sample cohort of 2124 subjects, mean ± S.D. tHcy levels in μmol/l were pre-Met 13.2 ± 4.3, post-Met 30.4 ± 9.76, and pre/post-Met Δ 17.1 ± 8.3. The hazard ratio (HR) for recurrent stroke was 1.16 (p = 0.026) for 1 S.D. higher pre-Met tHcy and 1.15 (p = 0.054) for 1 S.D. higher post-Met tHcy. For CAD, the HR for 1 S.D. higher pre-Met tHcy was 1.27 (p = 0.001) and was 1.00 (p = 0.99) for post-Met tHcy. In survival analyses using pre- or post-Met as covariates, the coefficient of pre/post-Met Δ was not significant for stroke and was only marginally significant for CAD (p < 0.08), but was negative. We conclude that fasting, pre-Met tHcy is as effective as post-Met tHcy or pre/post-Met Δ in predicting the risk for stroke and CAD.     

Comparison of the distribution of fluorine-18 fluoromisonidazole, deoxyglucose and methionine in tumour tissue

14 C-2-deoxyglucose (2DG) and ¹⁴C-methionine (Met). The study was performed using control rats with the AH109A tumour and rats with the same tumour under local hypoxia. Tumour uptake of FMISO was constant between 30 min and 2 h after injection, and the tumour to muscle ratio was 2 from 2 to 4 h. A tumour study with FMISO was scheduled at 2 h. Double-tracer autoradiography of the tumour demonstrated that in the areas of high FMISO uptake, there was low uptake of Met, while areas of low FMISO uptake showed high Met uptake. FMISO showed high grain density in the rim of the tumour surrounding the necrotic area. 2DG showed a more uniform distribution over the entire section of viable cells. The mean uptake of FMISO by hypoxic, radioresistant tumours was significantly higher than that by the control tumours (P<0.05), while both 2DG and Met uptake by the control tumours was higher than uptake by hypoxic tumours. When individual tumours were examined, the uptake of FMISO was inversely correlated with that of Met (r = –0.507, P<0.02), while 2DG showed almost uniform uptake with no significant correlation to FMISO. In conclusion, hypoxic and radioresistant tumours could be identified by increased FMISO uptake in our model, consistent with findings reported by others. We found a large overlap in the distribution of FMISO and 2DG within the tumour, but only a small overlap in the distribution of FMISO and Met. A combination of FMISO and other tracers in positron emission tomography or single-photon emission tomography studies might be more helpful than single-tracer studies in predicting the response of tumour tissues to radiotherapy. Received 27 November 1998 and in revised form 3 February 1999     

肿瘤细胞的甲硫氨酸依赖性对提高肿瘤化疗疗效的作用

目的探讨肿瘤细胞的甲硫氨酸依赖性在提高肿瘤化疗疗效方面的作用及意义。方法将甲硫氨酸（Ｍｅｔ）依赖性肿瘤细胞ＳＧＣ７９０１、ＭＣＦ７和非Ｍｅｔ依赖性肿瘤细胞Ａ５４９、Ａ３７５培养于Ｍｅｔ－Ｈｃｙ＋和Ｍｅｔ＋Ｈｃｙ－培养基中,加入不同浓度的周期特异性化疗药５Ｆｕ或非周期特异性化疗药ＭＭＣ;在细胞与药物接触不同时间段,用ＭＴＴ比色法检测化疗药物的抑瘤率。结果Ｍｅｔ－Ｈｃｙ＋中的５Ｆｕ对Ｍｅｔ依赖性肿瘤细胞的抑瘤率较Ｍｅｔ＋Ｈｃｙ－中的５Ｆｕ的抑瘤率有显著性提高;而５Ｆｕ对非Ｍｅｔ依赖性肿瘤细胞的抑瘤率,在两种培养基间差异无显著性。ＭＭＣ对Ｍｅｔ依赖性、非Ｍｅｔ依赖性肿瘤细胞的抑瘤率未因培养基的不同而差异有显著性。结论利用肿瘤细胞的Ｍｅｔ依赖性,Ｍｅｔ－Ｈｃｙ＋培养基可显著提高周期特异性化疗药（５Ｆｕ）对Ｍｅｔ依赖性肿瘤细胞的抑瘤率,但不能提高周期非特异性化疗药（ＭＭＣ）的抑瘤率。     

去左旋甲硫氨酸环境对小鼠免疫细胞功能的影响

目的:研究去左旋甲硫氨酸(L-Met)的培养液对小鼠免疫细胞功能影响.方法:从小鼠脾分离单个核细胞,在三组培养液中加入植物凝集素(PHA)体外诱导淋巴细胞,观察淋巴细胞增生功能,淋巴细胞亚群分布、T淋巴细胞活化分子表达及分泌IL-2数量.同时检测脂多糖(LPS)刺激单核/巨噬细胞分泌TNF-αt数量.结果:去L-Met培养液与含L-Met相比,PHA诱导的淋巴细胞增生,CD4 Th、CTL、NK细胞、B细胞亚群分布,CD4 Th细胞和CTL表面活化分子CD25、I-AK表达,淋巴细胞分泌IL-2数量差异均无显著性意义;LPS刺激单核/巨噬细胞分泌TNF-α数量无差异.结论:去L-Met的培养液不影响小鼠淋巴细胞免疫功能.     

腺苷蛋氨酸治疗乙型肝炎后肝硬化临床疗效观察

目的 观察腺苷甲硫氨酸(俗名蛋氨酸)治疗乙型肝炎(简称乙肝)后肝硬化的疗效.方法 选择乙肝后肝硬化患者60例,其中治疗组30例,对照组30例.血清总胆红素(TBIL)均大于55μmol/L,平均(102.12±22.31) μmol/L.治疗组TBIL为(98.23±17.50)μmol/L,对照组为(113.21±17.70) μmol/L,差异无统计学意义(P＞0.01).治疗组予以腺苷蛋氨酸(1000mg,静脉滴注,每天1次)及多烯磷脂酰胆碱(465 mg,静脉滴注,每天1次)联合治疗,疗程2周;对照组用多烯磷脂酰胆碱(465 mg,静脉滴注,每天1次)治疗,疗程2周.结果 治疗2周后,治疗组患者TBIL由(98.23±17.50)μmol/L降至(63.56±12.47)μmol/L,差异有统计学意义(P＜0.05);对照组TBIL由(113.21±17.70) μmol/L降至(108.60±24.38)μmol/L,与治疗组比较,差异有统计学意义(P＜0.05).且治疗组未见明显不良反应.结论 腺苷蛋氨酸治疗乙肝后肝硬化安全、有效,退黄效果显著.     

甲硫氨酸限制对胃癌细胞蛋白表达谱的影响

目的分析甲硫氨酸限制对胃癌SGC7901细胞蛋白表达谱的影响。方法Hoechst荧光染色法及流式细胞术验证胃癌SGC7901细胞的凋亡,用双向凝胶电泳分析蛋白表达差异。结果胃癌SGC7901细胞在限制甲硫氨酸培养液中培养5天后,部分细胞的细胞核内出现凋亡小体。限制甲硫氨酸培养液中SGC7901细胞的凋亡率显著高于正常培养液组（P<0.01）。双向电泳技术分析筛选出16 个表达差异的蛋白点。结论甲硫氨酸限制可以导致胃癌SGC7901细胞部分蛋白表达增加或降低,进而诱导胃癌细胞凋亡。     

中国山西人群中叶酸代谢基因MTRR 和MTHFR 与复杂先天畸形关联研究

目的 探讨叶酸代谢基因蛋氨酸合成酶还原酶（MTRR）和5,10 甲基四氢叶酸还原酶（MTHFR）基因多态性是否与复杂先天畸形相关,进一步研究其是否与三胚层发育来源的复杂先天畸形相关。方法 选取中国山西省250 例出生缺陷病例（包括先心病、神经管畸形和颅面畸形等复杂先天畸形）为研究对象,选择MTRR 单核苷酸多态性位点 rs1801394 和MTHFR 单核苷酸多态性位点rs1801133,利用SNaPshot 方法进行基因分型,并与420 例正常对照人群进行比较。结果 rs1801394 和 rs1801133 分别与多个先天出生缺陷有关。在隐性模型下,rs1801394 GG 基因型和rs1801133 CC 基因型的个体发生先天缺陷的概率低, 为出生缺陷的保护性因素。rs1801133 隐性纯合作为保护性因素与外胚层和内胚层器官来源复杂先天畸形相关,rs1801394 隐性纯合作为保护性因素与外胚层、中胚层和内胚层器官来源的复杂先天畸形相关。结论 中国山西人群中叶酸代谢基因MTRR 和MTHFR 与复杂先天畸形相关,并与胚层发育相关。     

Rapid chromatographic method to decipher distinct alterations in lipid classes in NAFLD/NASH

AIM: To establish a simple method to quantify lipid classes in liver diseases and to decipher the lipid profile in p62/IMP2-2/IGF2BP2-2 transgenic mice.METHODS: Liver-specific overexpression of the insulin-like growth factor 2 mRNA binding protein p62/IMP2-2/IGF2BP2-2 was used as a model for steatosis. Steatohepatitis was induced by feeding a methionine-choline deficient diet. Steatosis was assessed histologically. For thin layer chromatographic analysis, lipids were extracted from freeze-dried tissues by hexane/2-propanol, dried, redissolved, and chromatographically separated by a two-solvent system. Dilution series of lipid standards were chromatographed, detected, and quantified. The detection was performed by either 2’,7’-dichlorofluoresceine or a sulfuric acid/ethanol mixture.RESULTS: Histological analyses confirmed steatosis and steatohepatitis development. The extraction, chromatographic, and detection method showed high inter-assay reproducibility and allowed quantification of the different lipid classes. The analyses confirmed an increase of triglycerides and phosphatidylethanolamine and a decrease in phosphatidylcholine in the methionine-choline deficient diet. The method was used for the first time to asses the lipid classes induced in the p62-overexpressing mouse model and showed a significant increase in all detected lipid species with a prominent increase of triglycerides by 2-fold. Interestingly, the ratio of phosphatidylcholine to phosphatidylethanolamine was decreased, as previously suggested as a marker in the progression from steatosis to steatohepatitis.CONCLUSION: The thin layer chromatography analysis allows a reliable quantification of lipid classes and provides detailed insight into the lipogenic effect of p62.     

母亲甲硫氨酸合成酶A2756G及其还原酶A66G基因多态性与子代神经管缺陷易感性关系的Meta分析

目的 应用Meta分析方法定量评价母亲甲硫氨酸合成酶（MTR）基因A2756G和甲硫氨酸合成酶还原酶（MTRR）基因A66G多态性与子代神经管畸形（NTDs）易感性的相关性。方法 制定检索策略和文献纳入排除标准,系统检索中国生物医学文献数据库、中文科技期刊数据库、中国期刊全文数据库、万方数据库和PubMed、Web of Science外文数据库中自1990年1月到2011年10月的有关MTR A2756G和MTRR A66G位点多态性与子代NTDs易感性的病例对照研究、学位论文及其引文。采用RevMan5.0软件对各文献进行异质性检验和Meta分析,得到合并后的OR值及其95%CI。结果 共有18篇文献纳入Meta分析,MTR A2756G（907例病例和1978例对照）和MTRR A66G（1123例病例和1700例对照）基因多态性的文献各11篇。Meta分析结果显示,母亲MTR基因A2756G位点各遗传模型与子代NTDs易感性之间关联性无统计学意义,而MTRR基因 A66G位点GG/AG vs AA、GG vs AA、AG vs AA、GG vs AG/AA和G vs A各遗传模型与子代NTDs易感性之间关联性均有统计学意义,OR值及95%CI分别为1.89（1.28~2.78）、1.68（1.31~2.16）、1.77（1.18~2.66）、1.28（1.06~1.55）和1.35（1.12~1.63）。结论 母亲MTRR基因A66G位点多态性是子代NTDs发病的重要危险因素之一。