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71.
粉纹夜蛾(Trichoplusia ni)核型多角体病毒(TnNPV)感染草地贪夜蛾(Spodop-tera frugiperda)细胞后能诱导提高胸苷激酶的活性。不论是正常或感染细胞中的胸苷激酶都可将脱氧胞苷磷酸化,酶活最适pH及Mg~( )离子浓度值基本相同,DEAE-纤维素和Cibacron blue-sepharose柱层析所得酶活性图谱亦相似。TnNPV在胸苷激酶缺陷型的草地贪夜蛾细胞中能正常复制,但被感染细胞不具有胸苷激酶活性。由此可以确定,经TnNPV感染诱导后,活性有所提高的胸苷激酶不是病毒基因编码的。 相似文献
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冬虫夏草多糖的分子结构与免疫活性 总被引:2,自引:0,他引:2
冬虫夏草多糖(在本文中名为CS-81002)是由冬虫夏草菌Cordyceps sinensis(Berk)Sacc在人工发酵条件下产生的胞外多糖。用凝胶过滤法测出CS-81002的分子量Mr=43kD。CS-81002的单糖组成为Man:Gal:Glc=10.3:3.6:1。甲基化分析和部份酸水解结果表明,CS-81002是多分支的杂多糖,由→6)-Manp-(1→形成主链,大约每10个主链Man残基中,有6个在C3位上被取代(即形成→3,6)-Manp-(1→分支),有4个在位C2上被取代(即形成→2,6-Manp-(1→分支),从而形成侧链。主链中还有少许未被取代的Man残基。侧链则由→3-)-Galf-(1→,→4)-Glcf-(1→,→4)-Manp-(1→和→2)-Manp-(1→组成。位于非还原末端的,则三种单糖残基都有。CS-81002在5mg/kg体重×12剂量条件下,对正常的昆明小鼠腹腔巨噬细胞吞噬功能有显著促进作用。在同样剂量条件下,对正常LACA小鼠脾脏溶血斑形成细胞(PFC)对绵羊红细胞的溶血作用无显著影响。不同程度的部份酸水解可使CS-81002的分子量下降,分支减少,并且对巨噬细胞吞噬功能的促进作用亦有下降趋势。在所得到的各个部份酸水解级分(分子量分别为41000,40000,32000,16000和12000)中,分子量为12000的级分对巨噬细胞吞噬功能无促进作用。 相似文献
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<正> 单葡萄糖甘油二酯(MGDG)和双葡萄糖甘油二酯(DGDG)是莱氏衣原体膜上主要的极性脂。糖脂的生理功能过去很少研究,至今仍不清楚。近年来实验结果表明,MGDG在膜上容易形成六角形Ⅱ结构,而DGDG则形成脂双层结构。六角形Ⅱ结构的出现与生物膜的生理功能的关系是当前瞩目的研究内容。本文首次研究了外源脂肪酸和胆固酵对莱氏衣原体AIH089菌株膜上糖脂含量的影响。 相似文献
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Shinsuke Hara H. Dorota Halicka Silvia Bruno Jianping Gong Frank Traganos Zbigniew Darzynkiewicz 《Experimental cell research》1996,223(2):372
Proteolysis is an early event of apoptosis which appears to be associated with activation of the endonuclease which is responsible for internucleosomal DNA cleavage. The present study was designed to reveal the possible role of proteolysis in other early events, such as chromatin condensation, nuclear breakdown, and destabilization ofin situDNA double-stranded structure. Apoptosis of human leukemic HL-60 cells and rat thymocytes was induced by different agents, including DNA topoisomerase inhibitors, an RNA antimetabolite, and the glucocorticosteroid, prednisolone. DNA degradation was evaluated by pulsed field and conventional gel electrophoresis and by the presence ofin situDNA strand breaks. DNA stability was estimated by the measure of its sensitivityin situto denaturation. Chromatin condensation, nuclear breakdown, and other morphological changes were monitored by interference contrast and UV microscopy following cell staining with the DNA-specific fluorochrome 4′,6-diamidino-2-phenylindole. Several irreversible or reversible serine protease inhibitors prevented internucleosomal DNA degradation, nuclear breakdown, and destabilization of DNA double-stranded structure. The effective inhibitors, however, did not prevent the onset of chromatin condensation, nor the loss of the fine structural framework, nor the initial step of DNA cleavage generating DNA fragments of ≥50 kb in size. The data indicate that in both cell systems the activity of proteases sensitive to the inhibitors tested is needed for internucleosomal DNA cleavage to occur. The data also suggest that these proteases may be involved in dissolution of the nuclear envelope. Because nuclear matrix proteins and histones stabilize DNAin situ,and the decrease in DNA stability which occurs during apoptosis is precluded by the inhibitors, it is likely that serine proteases may degrade DNA stabilizing proteins. The activity of these proteases, however, appears needed neither for DNA cleavage to ≥50-kb fragments nor for the onset of chromatin condensation which is associated with dissolution of the structural framework of the nucleus. 相似文献
79.
Mangroves, woody halophytes restricted to protected tropical coasts, form some of the most productive ecosystems in the world, but their capacity to act as a carbon source or sink under climate change is unknown. Their ability to adjust growth or to function as potential carbon sinks under conditions of rising atmospheric CO2 during global change may affect global carbon cycling, but as yet has not been investigated experimentally. Halophyte responses to CO2 doubling may be constrained by the need to use carbon conservatively under water-limited conditions, but data are lacking to issue general predictions. We describe the growth, architecture, biomass allocation, anatomy, and photosynthetic physiology of the predominant neotropical mangrove tree, Rhizophora mangle L., grown solitarily in ambient (350 ll–1) and double-ambient (700 ll–1) CO2 concentrations for over 1 year. Mangrove seedlings exhibited significantly increased biomass, total stem length, branching activity, and total leaf area in elevated CO2. Enhanced total plant biomass under high CO2 was associated with higher root:shoot ratios, relative growth rates, and net assimilation rates, but few allometric shifts were attributable to CO2 treatment independent of plant size. Maximal photosynthetic rates were enhanced among high-CO2 plants while stomatal conductances were lower, but the magnitude of the treatment difference declined over time, and high-CO2 seedlings showed a lower Pmax at 700 ll–1 CO2 than low-CO2 plants transferred to 700 ll–1 CO2: possible evidence of downregulation. The relative thicknesses of leaf cell layers were not affected by treatment. Stomatal density decreased as epidermal cells enlarged in elevated CO2. Foliar chlorophyll, nitrogen, and sodium concentrations were lower in high CO2. Mangroves grown in high CO2 were reproductive after only 1 year of growth (fully 2 years before they typically reproduce in the field), produced aerial roots, and showed extensive lignification of the main stem; hence, elevated CO2 appeared to accelerate maturation as well as growth. Data from this long-term study suggest that certain mangrove growth characters will change flexibly as atmospheric CO2 increases, and accord with responses previously shown in Rhizophora apiculata. Such results must be integrated with data from sea-level rise studies to yield predictions of mangrove performance under changing climate. 相似文献
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