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为探究水杉凋落物的化感作用是否是影响其天然更新的障碍因素,该文设置了8种水杉新鲜凋落物和自然凋落物水浸提液浓度200、100、50、20、10、5、2、1 g·L-1和CK,分析不同类型不同浓度凋落物水浸提液对水杉种子萌发和生长的化感作用的影响。结果表明:(1)水杉新鲜凋落物水浸提液对水杉种子发芽率和发芽势影响不显著(P>0.05),对发芽指数有显著影响(P<0.05),1、100、200 g·L-1显著抑制种子发芽;水杉自然凋落物水浸提液对水杉种子萌发3个指标影响均不显著(P>0.05),而浓度为5、10、50、200 g·L-1时则有抑制效应。(2)水杉种子芽长、胚轴和主根长度均在不同浓度的新鲜和自然水杉凋落物水浸提液间差异显著(P<0.05),并随着水浸提液浓度的增加(≥10 g·L-1)而逐渐降低,尤其是50~200 g·L-1范围内抑制作用显著增强。(3)新鲜和自然水杉凋落物水浸提液对自身种子萌发后生长的抑制作用相较于对种子萌发强,并且新鲜凋落... 相似文献
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Karayianni V Mioglou E Iakovidou Z Mourelatos D Fousteris M Koutsourea A Arsenou E Nikolaropoulos S 《Mutation research》2003,535(1):79-86
Three newly synthesised steroidal esteric derivatives of nitrogen mustard (compounds 1-3) were comparatively studied on a molar basis regarding their ability to induce sister chromatid exchanges (SCEs) in normal human lymphocytes in vitro and therapeutic effects on leukemia P388 bearing mice. Compounds 1 and 3 are modified steroidal esters of p-methyl-m-N,N-bis(2-chloroethyl)amino benzoic acid, and compound 2 is a modified steroidal ester of chlorambucil. All compounds induced statistically significant increases in SCEs and decreases in proliferation rate indices (PRIs) of cultured human lymphocytes and significantly increased the life span of P388 bearing mice. In this study, the doses applied for therapeutic purposes upon leukemia P388 bearing mice in vivo were derived from cytogenetic observations in normal human lymphocytes in vitro. A substantially better therapeutic effect was obtained compared to the effect achieved after the use of quite higher doses related with LD(10) values. We have demonstrated that the order of anti-tumour effectiveness of the treatment schedules of the three newly synthesised compounds tested (at doses derived from cytogenetic observations) coincides with the order of the cytogenetic effects they induce. The SCE assay appears to have an application in the clinical prediction of tumour sensitivity to potential chemotherapeutics. 相似文献
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A new synthetic procedure and a modification of the original method described in the literature for the synthesis of the steroidal B-D bilactam, 3 beta-hydroxy-7 alpha,17 alpha-diaza-B,D-dihomo-5-androsten-7,17-dione are reported. The key step in the modified method involved protection of the D-lactamic nitrogen atom of 3 beta-acetoxy-17 alpha-aza-D-homo-5-androsten-17-one using a reagent of specific electrophilicity (due to the stereoelectronic properties of the cyclic amide), as Beckmann rearrangement of the B-steroidal ring was hindered, possibly via long range effects, by the presence of the unprotected D-lactamic moiety. Using the 3 beta-acetoxy-5-androsten-17-one as starting material, a new synthetic procedure was developed through ketalization of the 17-ketone and allylic oxidation to the 7-ketone, which was subsequently followed by Beckmann rearrangement of the B- and D-steroid rings. Both approaches resulted in 45 and 67% yields of the desired B,D-bilactam, respectively, in contrast to the 15% yield, which has been reported in the literature. 相似文献
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The last two decades have witnessed a break-through in identifying and understanding the functions of both the proteins and lipids of bacterial membranes. This development was parallelled by increasing insights into the biogenesis, topology, transport and sorting of membrane proteins. However, progress in research on the membrane distribution and transport of lipids in bacteria has been slow in that period. The development of novel biochemical in vitro approaches and recent genetic studies have increased our understanding of these subjects. The aim of this review is to present an overview of the current knowledge of the distribution and transport of lipids in both Gram-positive and Gram-negative bacteria. Special attention is paid to recently obtained results, which are expected to inspire further research to finally unravel these poorly understood phenomena. 相似文献
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本文简要综述了80年代以来国际上对根黄酮在调节植物根生长、完善根功能、影响氮素循环及在施加他感作用方面的研究进展,并对有关方面作了一些展望,以期引起植物营养工作者对植物次生物质的注意。 相似文献
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为探明鄂西南地区野生荚蒾属(Viburnum)植物的种群数量特征及区域分布状况,并揭示宜昌荚蒾(V.erosum)、桦叶荚蒾(V.betulifolium)、合轴荚蒾(V.sympodiale)、茶荚蒾(V.setigerum)、荚蒾(V.dilatatum)5种荚蒾属植物种群的生存现状及发展趋势,在鄂西南金子山国有林场、木林子国家级自然保护区及七姊妹山国家级自然保护区,共布设27 hm2固定动态监测样地对荚蒾属植物进行调查,通过对5种荚蒾属植物种群进行年龄结构、动态量化分析和静态生命表以及相关曲线等研究,探讨荚蒾属植物种群结构与动态特征及未来发展潜力。结果表明:(1)鄂西南荚蒾属植物在分布区域及种群数量大小上均存在明显差异。(2)种群结构与动态分析显示,5种荚蒾属植物种群年龄结构呈现为金字塔型,幼龄阶段种群个体数量较多,具有较强的增长潜力,但对外界干扰均具有较强的敏感性。(3)静态生命表显示,5种荚蒾属植物存活量均随着龄级的增加而单调递减;消失率与死亡率曲线变化趋势相似,但不同植物消失率与死亡率曲线波动具有差异性;种群存活曲线均趋近于Deevey-Ⅱ型。(4)4... 相似文献
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目的:在杆状病毒表达系统中表达融合蛋白乙型肝炎病毒前C蛋白-小鼠IgG Fc蛋白(HBV precore protein-mouse IgG Fc,HBV pre-c-Fc),并鉴定其免疫原性。方法:目的基因HBV prec-Fc连接到pFastBac1载体,获得的pFastBac1-HBV pre-c-Fc质粒转化DH10Bac感受态,通过Tn7转座子将目的基因转座到Bacmid中,得到Bacmid-HBV pre-c-Fc穿梭载体,脂质体包被后转染Sf9昆虫细胞获得P1代病毒,重复转染Sf9获得高滴度病毒。收集细胞上清超滤后通过Protein G亲和层析柱纯化得到目的蛋白HBV pre-c-Fc。纯化的蛋白大腿内侧肌肉注射免疫BALB/c小鼠并检测血清中乙型肝炎病毒核心蛋白抗体产生量。结果:HBV pre-c-Fc在昆虫细胞中成功表达,纯化后蛋白纯度达90%以上,蛋白产量约为3.03mg/L,纯化蛋白能有效刺激BALB/c小鼠产生特异抗体。结论:成功地在杆状病毒表达系统中表达了具有免疫原性的HBV pre-c-Fc蛋白,为生产乙肝治疗性疫苗奠定了基础。 相似文献
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酪氨酸激酶抑制剂类抗肿瘤药物研究方法进展 总被引:1,自引:0,他引:1
酪氨酸激酶(protein tyrosine kinases,PTKs)在肿瘤细胞的增殖、分化、迁移、侵袭等相关信号通路中起到了关键的调控作用,已经成为肿瘤靶向性治疗的重要靶点.本文对靶向酪氨酸激酶的小分子抑制剂的筛选和评价方法进行综述,以期促进酪氨酸激酶抑制剂类抗肿瘤药物的研究. 相似文献