【作者】 仝宗喜；

【导师】 康世良；

【作者基本信息】 东北农业大学 ， 临床兽医学， 2004， 博士

【摘要】 硒的研究是当前微量元素研究的热点和重点，这是因为硒缺乏症是侵害多种动物和人的世界性疾病，危害极为严重。目前，虽然用硒制剂防治硒缺乏病取得了明显的效果，但各种动物硒缺乏症依然时有发生；并且硒具有重要的生物学特性，开发潜力和应用价值很大。硒的研究现已成为动物营养研究中一个重要的分支内容，也是21世纪一个比较活跃的研究领域，同时推动了动物营养与动物医学相关学科的有机结合，因此全面系统地认识硒，研究硒缺乏症在各种动物体内的分子机理具有十分重要的理论价值和学术意义。为了深入探讨雏鸡硒缺乏症发病的分子机理，本课题采用分组对比的方法，通过建立雏鸡硒缺乏症实验模型，在进行临床观察、定期剖杀并检测体内硒含量和常规检验等基础上，重点研究了与两种硒蛋白即谷胱甘肽过氧化物酶（GSH-px）和Ⅰ型脱碘酶（ID-1）有关的以下几个方面的内容：系统地研究了硒缺乏时雏鸡体内自由基代谢和抗氧化系统功能的影响；系统地研究了硒缺乏对雏鸡肝脏、肌肉、胰腺和甲状腺的损伤机理；首次测定了硒缺乏雏鸡细胞因子水平的变化情况，以便探讨硒缺乏致使雏鸡免疫力降低的机理；首次检测了硒缺乏时，雏鸡甲状腺、肝脏、胸肌、胰腺、胸腺等组织细胞凋亡情况，以便揭示硒缺乏雏鸡体内的两种细胞死亡（即坏死和细胞凋亡）的机理；并对硒缺乏雏鸡红细胞免疫系统、胆红素代谢等进行了检测分析；系统地研究了硒缺乏对雏鸡红细胞的影响，以便查明硒缺乏雏鸡贫血的机理。研究结果表明：本实验成功地复制了雏鸡硒缺乏症模型，在临床症状、病理剖检和病理组织学方面取得了与自然病例一致的结果，并对肝脏、胰腺、胸腺、甲状腺和肌肉等进行了病理组织学超微结构的观察，为硒缺乏症的研究增添了新内容。通过收集硒缺乏症雏鸡的临床症状、病理学检查和实验室检查结果，筛选及评价了雏鸡硒缺乏症诊断指标，并增加了脱碘酶（ID-1）等多项诊断的新标识，为临床诊断雏鸡硒缺乏症提供了可靠的实验依据。雏鸡硒缺乏导致体内总抗氧化能力（T-AOC）下降，谷胱甘肽过氧化物酶（GSH-px）活性降低，丙二醛（MDA）含量增多，引发机体的抗氧化能力下降，不仅不能破坏过氧化物，防止过氧化物对机体细胞和亚细胞脂质膜的损害，而且还促进体内产生过多的氧自由基（OFR）和一氧化氮自由基（NO），致使细胞处于氧化应激状态，损伤细胞膜系统，造成物质代谢和能量代谢紊乱，产生一系列病理变化，出现贫血、生长迟缓、渗出性素质、运动障碍、组织出血、坏死、营养不良等临床病理学变化，构成硒缺乏症的病理学基础。首次证实硒缺乏可导致雏鸡细胞因子白细胞介素1（IL-1）、白细胞介素2（IL-2）、红细胞生成素（EPO）、肿瘤坏死因子（TNF）含量发生变化，其中血清IL-1和IL-2含量降低，淋巴细胞的增殖、分化受到影响，对机体产生广泛的免疫抑制作用。血清EPO含量下降和TNF含量升高，也使机体免疫力降低，并且是导致机体再生障碍性贫血、各组织细胞凋亡、渗出性素质等的机理之一。雏鸡硒缺乏时，甲状腺、肝脏、胸部肌肉、胰腺、胸腺等组织细胞凋亡增加，证明硒缺乏雏鸡体内发生两种细胞死亡，即坏死和细胞凋亡，由于细胞坏死和凋亡的加重与<WP=13>增多，致使硒缺乏雏鸡走向衰竭，最后死亡。硒缺乏致组织细胞膜系统的脂质过氧化损伤的作用是硒缺乏诱导组织细胞凋亡的主要机制。首次揭示雏鸡硒缺乏不但对甲状腺造成损伤，而且还特异性地降低肝脏、肾脏等组织中ID-1活性，使血清3-5-3/-5/-四碘甲状腺原氨酸（T4）、游离T4含量升高，3-5-3/-三碘甲状腺原氨酸（T3）、游离T3含量下降，促甲状腺激素（TSH）含量升高，严重影响整个机体的生长发育及营养物质代谢，并是导致造血物质缺乏所致的营养性贫血的机理之一。雏鸡硒缺乏降低了红细胞免疫力；同时降低了红细胞对特异性免疫的调节作用，主要表现为降低了吞噬细胞的吞噬能力、清除循环免疫复合物能力、机体识别和携带抗原能力以及对Τ、B淋巴细胞、NK细胞补体的活化过程的免疫调节作用，结果使机体免疫力下降。雏鸡硒缺乏使红细胞膜三磷酸腺苷酶（ATPase）活性、GSH-px活性降低，唾液酸（SA）含量减少，丙二醛（MDA）含量增加， 红细胞的变形性和流动性下降，红细胞破溶增加，致使雏鸡发生溶血性贫血。首次发现缺乏症雏鸡血清总胆红素含量升高，间接胆红素和直接胆红素含量增加，其机理归因于骨骼肌损伤使肌红蛋白析出增多，红细胞破溶增多（引发溶血性黄疸），肝脏变性、坏死加重（引发肝源性黄疸）。雏鸡血清间接胆红素含量增加，对脑组织等产生毒性作用，严重时影响脑组织的正常活动，出现雏鸡瘫痪等一系列的神经症状。本实验从器官、细胞、亚细胞和分子水平系统地研究了雏鸡硒缺乏症的发生机理，这有利于我们进一步认识雏鸡的硒缺乏症、乃至其它动物硒缺乏症，为动物硒缺乏症的更深入地研究奠定了理论基础。并为人类克山病和大骨节病等缺硒病和碘缺乏病的研究提供有益的启示和借鉴。因此对保障家畜和人类自身的健康有着十分深远的意义。更多还原

【Abstract】 Studies on selenium are the hotspot and focus of microelement study at present. This is because selenium-penia is a global disease, which infringes upon all kinds of animals and human beings and causes serious damages. At present, we have made great achievements in preventing and curing of selenium-penia, but selenium-penia still frequently happens in all kinds of animals. In addition, selenium has important biological characters, great developmental potentials and applied value. Studies on selenium have become an important offshoot content in animal nutrition research and a more active research field in 21 century, which likewise have enhanced the combination of related subjects between animal nutrition and animal medicine. Therefore, investiagating molecular mechanisms of selenium-penia in diverse animals have important theoretical value and academic meaning.In order to deeply investigate the molecular mechanism of selenium-penia in chicken , this experiment adopted a contrast means in different groups and established experimental model of chicken with selenium-penia. By observing clinical symptoms, killing periodically and anatomizing chicken, we determined selenium content and routine test of GSH-px and ID-Ⅰ(two selenoproteins ). The main aspects of this research were follows: The effect of selenium deficiency on the metabolism of free radicals and the function of anti-oxidative system in chicken in detail were studied; The damadging mechanism of liver, muscle, pancreas, thyroid in chicken with selenium-penia in detail was also investigated; the change of cytokines level in chicken with selenium-penia was firstly examined in order to discuss the decline of immune mechanism caused by selenium deficiency; apoptosis of histocyte of thyroid, liver, chest muscle, pancreas and thymus etc in chicken with selenium-penia was firstly observed in order to reveal two kinds of death mechanisms（necrosis and apoptosis） of cells in chicken with selenium-penia; the immune system of erythrocyte and bilirubin metabolism in chicken with selenium-penia was analyzed; the effect of selenium deficiency on erythrocyte in chicken in detail was studied in order to ascertain the mechanism of anemia in chicken with selenium-penia. The main conclutions are as follows: This research successfully copied the model of chicken with selenium-penia and acquired consistent results with the natural case in clinical symptoms, pathological dissection and pathological histology and observed ultrastruction of liver, pancreas, thymus and muscle in pathological histology, which added to new contents for the reserch of selenium-penia, at the same time provided credible experimental evidences for the clinical diagnosis of chicken with selenium-penia by collecting clinical symptoms and results of pathology and laboratory, filtrating and appraising indexes of diagnosis of chicken with selenium-penia, increasing new indexes of diagnosis that include ID etc. <WP=15>Selenium deficiency in chicken causes the decrease of T-AOC and GSP-px activity，the increase of MDA content. These make anti-oxidative capacitity decrease in orgnism, which not only can’t destroy the peroxide and prevent the cellular and subcellular membrane from damage of the preoxide, but also promote the production of excess OFR and NO in vivo. Finally these changes make cell stay in oxidative stress condition and damage the cellular membrane system and cause metabolic disorder of matter and energy, which induces a range of lesion including anemia, lag growth, exudative diathesis, motor disturbance, haemorrhage and necrosis of tissues, nutrition deficiency. All above form pathological foundation of selenium-penia.This research first confirms that deficiency of selenium in chicken induces changes of IL-1, IL-2, EPO and TNF content including the decrease of IL-1 and IL-2 content in the serum which brings to some effects on multiplication and differentiation of lymphocyte and extensive effects on immune depression in organism. The decrease of EPO content and the increase of TNF content in th更多还原