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类胡萝卜素类化合物是一类天然化合物,它们可在植物及微生物体内被合成.在高等植物中,类胡萝卜素在体内的合成类异戊二烯代谢途径进行.在类异戊二烯代谢途径中,一般认为:第一个类胡萝卜素合成的前体为3,5-二羟-3-甲基戊酸(MVA,C6),随后有牛儿牛儿焦磷酸(GGDP,C20),八氢蕃茄红素(phytoene,C40),蕃茄红素(lycopene,C40)及β-胡萝卜素(β-caroternes,C40)等代谢产物的合成,最后形成叶黄素(xanthophylls).在高等植物中,牻牛儿牻牛儿焦磷酸的合成,八氢蕃茄红素的合成及去饱和三个反应及相关的酶和基因已被比较透彻地研究.类胡萝卜素的生物合成由遗传和环境因子共同调控.许多高等植物光合组织的遗传突变对类胡萝卜素生物合成的影响已被详尽地探讨过.环境因子对体内类胡萝卜素生物合成基因的表达有明显的影响.在高等植物的光合组织中,类胡萝卜素生物合成于细胞的叶绿体中.环境因子,如:光和温度等,可在酶、叶绿体和细胞三个不同水平上调控类胡萝卜素的生物合成. 相似文献
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红茶香气形成机制及提高途径 总被引:1,自引:0,他引:1
香气是衡量茶叶品质优劣的重要因子。我国的红茶虽然在浓、强、鲜度方面略低于印度和斯里兰卡的一些优质红茶,但在香气方面却具有自己的特色。如“祁红”、“宁红”茶中的香叶醇(牻牛儿醇)、苯甲醇、苯乙醇等芳香物质含量很高,比印度、斯里兰卡的红茶约高1—2倍,故含有浓烈的“甜香”。为了使“祁红”、“宁红”的香气进一步提高和发挥,本文依据红茶香气的形成机制,就其提高途径进行研讨。 相似文献
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以多年生宿根型草本植物橡胶草为材料,根据已获得的橡胶草牻牛儿基牻牛儿基焦磷酸合酶(geranylgeranyl pyrophosphate synthase,GGPPS)基因序列设计引物,采用TAIL-PCR扩增到GGPPS基因5'上游大小为1131 bp的序列。采用PlantCare和PLACE软件分析,表明该序列不仅具有启动子的基本元件,同时还有与多个器官特异表达元件以及与胁迫相关的顺式作用元件,命名为pTkGGPPS(GenBank:KT901796)。将该序列代替pCAMBIA1304质粒上的CaMV 35S启动子序列,以GFP基因作为报告基因,构建pCAMBIA1304-pTkGGPPS-GFP植物表达载体,利用农杆菌介导法转化洋葱表皮细胞,结果表明,该启动子能够驱动GFP基因表达,具有一定的活性。TkGGPPS基因启动子克隆及瞬时表达为橡胶草中橡胶合成及组织特异性研究奠定了基础。 相似文献
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老鹳草中黄酮类成分的药理、生物学作用 总被引:2,自引:0,他引:2
老鹳草为临床常用药,具有多种药理作用,其中黄酮类化合物作为主要成分,是一大类从高等植物中提取的可食用的多酚类物质,具有抗氧化和自由基清除活性,对人体具有营养及医疗价值,如抗病毒、抗癌、保护神经系统和心血管系统等。本文介绍了老鹳草黄酮类成分的药理、生物学作用,为进一步开发和利用老鹳草的黄酮类物质提供一定的文献基础。 相似文献
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进入冬季后,犬的跛行在北方较为常见。跛行病例中常见骨折、椎间盘突出、肌炎、营养代谢中的维生素B缺乏以及风湿性关节炎为了确诊是否为风湿性疾病,我们特对犬进行抗链球菌溶血素“O”(ASO)以及类风湿因子(RF)的检验测试。1材料与方法1.1标本血清来自于就诊的检查风湿的史宾格犬、德国牧羊犬、拉布拉多犬共计30头。平均为10月龄,雌性犬9头,雄性犬21头。检验时间为2006年6~11月。犬采血后,离心获得新鲜血清标本,贮存于2~8℃。1.2试剂1.2.1抗链球菌溶血素“O”(ASO)测定试剂盒—上海捷门生物技术合作公司生产。1.2.2类风湿因子(RF)测定… 相似文献
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天蚕丝素和丝胶的分子量研究 总被引:3,自引:0,他引:3
天蚕丝素和丝胶的分子量研究周丛照,吴春晓,李振刚(中国科技大学生物系)天蚕(Antheraeayamamai)又名山蚕、日本柞蚕,属天蚕蛾科柞蚕属,主要分布于我国东北、日本、朝鲜等地,是一种珍贵的大型野生绢丝昆虫。其丝质优良,光泽好,素有“丝中皇后”... 相似文献
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老鹤草工蜂臭腺分泌的引导信息素 ,成分复杂 (牛儿醇是主要成分 ) ,国外已有人工合成的 ,做成诱芯出售。工蜂发臭时 ,凑近一闻 ,就能闻到一股像老鹤草的独特气味。牛儿苗 (牛儿苗科 ,牛儿苗属 ) ,别名 :长嘴老鹤草、太阳花、勾链链、车车路、绵绵牛。一年生草本 ,高10~40cm,密生白毛。叶对生 ,柄长 ,羽状深裂或全裂 ,3~9对。夏开淡紫色或粉红色花 ,伞形花序 ,腋生。5瓣花 ,倒卵形 ,蒴果 ,有喙 (长3~5cm) ,状如老鹤之嘴 ,故名。生于山坡、路旁 ,东北、西北、华北、中原都有分布。牛儿苗全草含挥发油 :牛儿醇 (… 相似文献
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魏静 《四川畜牧兽医学院学报》2009,(4):28-32
在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。 相似文献
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本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。 相似文献
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REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air. 相似文献
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Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF
Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo. 相似文献
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乳酸杆菌作为益生菌广泛用于人和动物.本文综述了乳酸杆菌改善宿主健康的机制.乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道.文章重点讨论了乳酸杆菌表面成分(表面蛋白、脂磷壁酸和肽聚糖)与肠道受体(C型凝集素受体、Toll样受体和Nod样受体),阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制. 相似文献