【作者】 郭怀兰；

【导师】 孙秀发；

【作者基本信息】 华中科技大学 ， 营养与食品卫生学， 2006， 博士

【摘要】 随着全民食盐加碘政策的实施，碘缺乏病已得到了有效控制。但另一方面，由于摄入含碘高的食物、水以及药物，或由于补碘不当造成的过量碘对机体的危害日益受到关注。我国生活在水源性高碘地区的人口已达到6000万。深入研究过量碘对人体的危害以采取有效的干预措施成为急需解决的重要问题。以往的研究证实，过量碘可引起高碘性甲状腺肿大，过量碘摄入是否也会影响脑发育过程而影响智力，有关此方面的研究资料较少并且没有统一的结论。另一微量元素硒以硒半胱氨酸的形式存在于许多蛋白以及酶的活性中心，是抗氧化酶谷胱甘肽过氧化物酶（GSH-Px）和甲腺原氨酸脱碘酶的重要组成成分，在甲状腺激素的合成、代谢以及甲状腺组织损伤过程中具有重要作用。有研究认为硒可通过影响甲状腺素合成影响神经系统发育，但有关硒、碘与脑发育的研究多为硒与低碘导致的脑发育障碍方面的资料，有关硒对过量碘导致的脑发育障碍的干预作用的研究，国内外未见报道。本研究在成功复制Balb/c小鼠过量碘动物模型的基础上，首先观察了过量碘对亲代鼠甲状腺激素代谢的影响及不同剂量硒的干预作用；然后观察过量碘对孕鼠甲状腺激素代谢的影响及不同剂量的硒干预作用；随后观察了过量碘对仔鼠甲状腺激素代谢的影响及不同剂量硒的干预作用，进行了脑组织形态学及海马神经元超微结构的研究，最后应用荧光定量PCR、Western-blot和免疫组化方法检测了神经元特异性烯醇化酶（NSE）、突触素（SYP）、神经颗粒素（RC3）、微管蛋白（α-tubulin）、G蛋白α亚单位（G0α）、甲状腺激素受体（TRα1和TRβ1）基因的表达，从神经元和树突、突触的成熟、细胞骨架蛋白、甲状腺激素受体、信号传导几个方面深入探讨了过量碘对仔鼠脑神经元发育影响的分子机制及硒的干预作用，为进一步深入研究过量碘对智力的影响及硒的干预作用提供理论依据。现将结果报告如下：第一部分过量碘亲代小鼠模型的建立及不同剂量硒对过量碘危害的干预作用目的复制过量碘亲代小鼠动物模型，观察不同剂量硒对过量碘亲代鼠甲状腺激素代谢的影响，在过量碘动物模型的基础上，探讨硒对过量碘亲代小鼠所致损伤的干预作用及其机制及适宜剂量范围，为下一步实验提供依据。方法将刚断乳的清洁级Balb/c小鼠240只（雌雄2：1），随机分为8组，每组30只动物，分别给予自来水及含碘酸钾（KIO₃）的过量碘水，过量碘组碘剂量为3000μg/L碘，过量碘补硒组分为6组，饮水中除含3000μg/L碘，还分别含亚硒酸钠：0.1、0.2、0.3、0.4、0.5、0.75mg/L Se。四个月后，测定小鼠尿碘、尿硒、肝硒、血清甲状腺激素，肝、肾和甲状腺1型脱碘酶（D1）活性和mRNA水平，并取甲状腺观察病理变化。结果3000μg/LⅠ会导致亲代鼠尿碘水平显著升高，尿硒水平显著下降（P＜0.05），肝硒水平有下降趋势；血清总四碘甲状腺原氨酸（T₄）显著升高，总三碘甲状腺原氨酸（T₃）降低（P＜0.05）；甲状腺病理切片表现为胶质潴留性甲状腺肿；肝、肾和甲状腺D1的活性和mRNA水平下降（P＜0.05）。补硒可提高过量碘亲代鼠的硒营养状况，升高尿碘、尿硒、肝硒以及甲状腺激素水平（P＜0.05），减轻甲状腺滤泡腔胶质潴留，升高肝、肾和甲状腺D1的活性和mRNA表达水平，改善甲状腺激素代谢异常，以0.2～0.4mg/L硒剂量范围效果较好。结论Balb/c亲代小鼠过量碘动物模型的复制是成功的；3000μg/L碘导致亲代小鼠甲状腺激素代谢紊乱，补充亚硒酸钠可改善过量碘亲代小鼠甲状腺激素代谢，以0.2～0.4mg/L硒剂量范围效果较好。本部分的研究首次表明补硒可干预过量碘对亲代小鼠甲状腺激素的影响，为进一步研究硒干预过量碘对仔鼠脑神经元发育的影响打下了基础。第二部分过量碘对孕鼠甲状腺激素代谢的影响及不同剂量的硒干预作用目的观察过量碘对孕鼠甲状腺激素代谢的影响及不同剂量硒的干预作用，为进一步探讨硒拮抗过量碘所致神经元发育异常的机制提供依据。方法刚断乳的清洁级Balb/c小鼠240只（雌雄2：1），按体重随机分为8组，每组30只动物，A组，即正常对照组，给予自来水；B组，过量碘组，给予3000μg/L I的过量碘水；C～H组为过量碘补硒组，除了3000μg/L I外，分别给予0.1、0.2、0.3、0.4、0.5、0.75mg/L的硒。亲代鼠饲养四个月后，按雌雄2：1的比例合笼，次日晨检查阴栓，查到阴栓者计为孕0.5d，在孕12.5d和19.5d分别取6至10只母鼠的血、肝脏和肾脏测定其甲状腺激素水平、脱碘酶D1的活性和mRNA表达等指标。同时取孕12.5d和19.5d母鼠的胎盘和12.5d的子宫，液氮速冻后，-70℃保存，测胎盘和子宫2型脱碘酶（D2）和3型脱碘酶（D3）活性及mRNA水平、肝脏和胎盘硒含量。结果①过量碘显著降低孕鼠肝硒水平（P＜0.05），补硒可显著提高孕鼠的硒营养水平，肝硒水平在0.2mg/L补硒组开始显著高于过量碘组，胎盘硒水平在0.3mg/L补硒组开始显著高于过量碘组。②过量碘降低胎盘重量（P＜0.05），补硒在一定剂量范围内有升高平均胎盘重量的趋势，0.3mg/L补硒组与过量碘组间有显著性差异。③过量碘降低孕鼠血清T₃水平，升高T₄水平（P＜0.05）；补硒可升高过量碘孕鼠血清T₃水平，降低T₄水平，从0.2mg/L补硒组开始与过量碘对照组有显著性差异，但在0.75mg/L补硒组，血清T₃和T₄水平与过量碘组间无显著性差异。④过量碘可降低孕鼠肝、肾D1活性（P＜0.05），补硒可显著升高肝、肾D1活性和肝mRNA水平。肝脏、肾脏D1活性在0.2～0.5mg/L剂量组显著高于过量碘组（P＜0.05）。肝脏D1mRNA水平在0.2～0.5mg/L剂量组显著高于过量碘组，肾脏D1mRNA水平在0.3～0.75mg/L剂量组显著高于过量碘组。⑤过量碘可降低胎盘和子宫D2活性，升高19.5d子宫的D3活性（P＜0.05）；补硒可显著升高胎盘和子宫D2活性。12.5d胎盘D2活性在0.2～0.3mg/L硒剂量组显著高于过量碘组，19.5d胎盘D2活性在0.3～0.4mg/L剂量组显著高于过量碘组，而19.5d子宫D2活性从0.2mg/L硒剂量组开始显著高于过量碘组（P＜0.05）。补硒对胎盘D3活性无明显影响，而19.5d子宫的D3活性从0.2mg/L硒剂量组开始显著低于过量碘组。结论过量碘影响孕鼠肝、肾、胎盘和子宫脱碘酶活性以及孕鼠甲状腺激素代谢，从而可能影响胎儿甲状腺激素代谢；补硒可明显改善过量碘孕鼠的硒营养状况，在一定剂量范围内发挥对过量碘所致胚胎毒性的干预作用。补硒可调节甲状腺激素代谢过程中关键酶-脱碘酶的活性，影响孕鼠和胚胎的甲状腺激素水平，本实验条件下，拮抗过量碘所致胚胎毒性的适宜硒剂量为0.2～0.4mg/L。首次说明补硒在妊娠期这个环节上拮抗过量碘对子代的影响，为进一步探讨硒拮抗过量碘所致神经元发育异常的机制提供依据。第三部分过量碘对仔鼠甲状腺激素代谢的影响及不同剂量硒的干预作用目的观察过量碘仔鼠甲状腺激素代谢的影响及不同剂量硒的干预作用，为进一步探讨硒干预过量碘仔鼠脑神经元发育的机制提供理论依据。方法刚断乳的清洁级Balb/c小鼠240只（雌雄2：1），按随机分为8组，每组30只动物，即正常对照组（NC），给予自来水；过量碘组（EI），给予3000μg/LI的过量碘水；C～H组为过量碘补硒组，除了3000μg/LI外，分别给予0.1、0.2、0.3、0.4、0.5、0.75mg/L的硒。各组亲代鼠饲养4个月后雌雄按2：1交配，取0、14和28日龄仔鼠血及脑组织，测定甲状腺激素和脑D2、D3活性及mRNA水平；取肝脏、肾脏，测D1活性和mRNA水平；取棕色脂肪组织（BAT）测D2活性；测0日龄仔鼠肝硒含量；取14日龄仔鼠甲状腺，检查病理改变。结果过量碘导致14日龄仔鼠甲状腺出现胶质储留性甲状腺肿，滤泡腔变大，腔内胶质较多，上皮细胞较少，细胞较扁，不同剂量补硒可减轻甲状腺肿，但0.75mg/L硒效果较差。与正常对照组相比，过量碘组0日龄仔鼠肝硒含量降低，但无显著性意义，14日龄仔鼠血清T₄水平显著降低（P＜0.05）；0和14日龄时，过量碘组仔鼠脑组织T₄、T₃水平显著降低，脑D3活性及mRNA表达降低，脑D2活性及mRNA表达升高，肝、肾D1活性降低，BAT D2活性升高（P＜0.05），不同剂量补硒组较过量碘组血清和脑组织T₄、T₃都有一定程度上的升高，上调脑D3和肝、肾D1活性和mRNA表达，下调脑和BAT D2活性和mRNA表达；28日龄时各组血清和脑T₄、T₃水平、脑和BAT D2、脑D3以及肝、肾D1活性和表达无显著性差异。结论母体过量碘和高血清甲状腺激素可通过胎盘到达胎儿，引起仔鼠胶质储溜性甲状腺肿大，影响甲状腺激素的合成和释放，导致仔鼠出现甲状腺功能减退症和甲状腺激素代谢紊乱。虽然，过量碘可造成亲代鼠硒的不足或相对缺乏，但仔鼠无明显硒缺乏。补硒可拮抗过量碘引起的仔鼠甲状腺形态和功能的异常，主要通过影响母体的甲状腺激素代谢而发挥作用。本实验条件下0.2～0.4mg/L的硒发挥了相对较好的干预作用。本实验首次表明补硒可拮抗过量碘引起的仔鼠甲状腺形态和功能的异常，为进一步研究硒干预过量碘仔鼠脑神经元发育提供了理论依据。第四部分过量碘对仔鼠脑组织及神经元超微结构的影响及硒的干预作用目的从大脑组织形态学及超微结构上，观察过量碘对仔鼠脑发育的影响及硒的干预作用，为研究硒干预过量碘仔鼠智力的影响提供理论依据。方法动物饲养、分组和交配与第三部分类似。将出生后0、14和28日龄仔鼠摘眼球取血并脱臼致死，断头，冰上快速分离大脑及海马。将分离的大脑放入4％多聚甲醛固定，经常规洗涤、脱水、透明、浸蜡和包埋，石蜡固定并制作切片，用于HE染色。参照鼠脑立体定位图，在冰上分离14日龄仔鼠海马CA1区，修成1mm×1mm×1mm小块，2.5％戊二醛预固定后，用于电镜标本制作及观察。结果与正常组相比，光镜下，0日龄过量碘组皮层细胞更密集，体积更小，14日龄过量碘组仔鼠大脑皮层、齿状回和CA1区神经细胞小而圆，核着色较深，异染色质较多，胞质少，细胞数较多，细胞分化程度较低，发育程度较低；大脑皮层细胞紧密相连，导致整个大脑减小，过量碘组14日龄仔鼠海马CA1区神经元超微结构表现为细胞突起较少，核周染色质较少，核较大，核/浆比增大，异染色质增多，胞质细胞器减少，粗面内质网及核糖核蛋白体数量较少，线粒体也减少，轴突和树突内微管和微丝减少，表明过量碘使仔鼠脑神经元发育落后，补硒可使仔鼠脑神经元发育落后有一定的改善。结论过量碘造成大脑组织及神经细胞超微结构异常，大脑发育落后，补硒对过量碘仔鼠脑形态和神经元超微结构异常具有一定的改善作用，本研究首次为硒干预过量碘仔鼠脑发育提供了组织形态和超微结构的依据，为进一步研究硒干预过量碘对智力的影响提供了理论依据。第五部分过量碘对仔鼠脑神经元发育影响的分子机制及硒的干预作用目的从分子水平上，观察过量碘对不同日龄仔鼠脑神经元发育的影响及硒的干预作用，应用荧光定量PCR、Western-blot和免疫组织化学的方法，从神经元的发育成熟、突触的发育、甲状腺激素靶基因神经颗粒素的表达、甲状腺激素受体、信号传导几个方面深入探讨硒对过量碘仔鼠脑神经元发育的影响及分子机制。方法动物饲养和交配与第三部分。刚断乳的清洁级Balb/c小鼠120只（雌雄2：1），按随机分为4组，每组30只动物，即正常对照组（NC）给予自来水；过量碘组（EI+）给予3000μg/L I的过量碘水；补硒组（Se+）饮水中给予0.2mg/L的硒；过量碘补硒组（EI+Se+）除了3000μg/L I外，给予0.2mg/L的硒。将出生0日龄（P0）、14日龄（P14）、28日龄（P28）仔鼠摘眼球放血并脱臼致死，断头，冰上快速分离大脑，液氮速冻，然后存放于-80℃。将一部分分离的大脑放入4％多聚甲醛固定，经常规洗涤、脱水、透明、浸蜡和包埋，石蜡固定并制作切片，用于免疫组化。结果过量碘可下调0和14日龄大脑神经元特异性烯醇化酶（NSE）、突触素（SYP）、神经颗粒素（RC3）的表达，下调0日龄微管蛋白α-tubulin的表达（P＜0.05），延缓出生后α-tubulin表达降低的速度，上调甲状腺激素受体（TRα1和TRβ1）和G蛋白α亚单位（G0α）的表达（P＜0.05）。28日龄各组仔鼠脑NSE、SYP、α-tubulin、RC3、TRα1和TRβ1以及G0α的表达水平无明显差异。补硒则可拮抗过量碘引起的0和14日龄仔鼠大脑NSE、SYP和RC3的表达下降，下调TRα1和TRβ₁ mRNA、GoαmRNA的表达，使出生后α-tubulin表达下调模式与正常对照组接近。结论过量碘可引起NSE、SYP、RC3、α-tubulin的表达下调以及TRα1和TRβ1以及G0α的表达上调，从而影响仔鼠脑神经元的发育成熟、树突发育以及突触发育，硒可拮抗过量碘对脑神经元发育的影响。硒可能主要是通过影响过量碘亲代、孕鼠以及仔鼠甲状腺激素代谢来发挥对过量碘仔鼠脑神经元发育的干预作用，本研究首次在分子水平研究了硒对过量碘不同日龄仔鼠脑神经元发育的干预作用，为进一步探讨硒干预过量碘对智力的影响奠定了理论基础。更多还原

【Abstract】 The goal of eliminating iodine deficiency disease （IDD） has been achieved since Universal Salt Iodization (USD policy has been widely carried out in many nations including China. On the other hand, reports are increasingly appearing about the side effects caused by excess iodine intake. Iodine-induced goiter has been reported in many nations and areas resulted from ingestion of excess iodine in foods, in drinking water and in medications, or resulted from excess iodine supplementation in iodated foods. Previous studies reveal that excess iodine intake may result in diffused colloid goiter. However, it is not well documented if iodine excess also has an effect on brain development as iodine deficiency. Another microelement selenium is essential to thyroid hormone metabolism and thyroid function by the selenocysteine-containing glutathione peroxidase （GSH-Px） system and deiodinase system. Se influences nervous system development by thyroid hormone. Several studies have been carried out to establish the effects of combined selenium and iodine deficiency on brain development. However, few researches were carried out to study the intervention of selenium on dysfunction induced by excess iodine. It is necessary to study the possible intervention of Se on brain development defect induced by excess iodine. In this study, on the basis of excess iodine animal model successfully established in Balb/c mice, first, we observed the effects of excess iodine on thyroid hormone and deiodinase, and intervention by different doses of selenium in maternal mice. Second, we observed the effects of excess iodine on thyroid hormone metabolism in pregnant mice and intervention by different doses of Se. Third, we observed the effects of excess iodine on thyroid hormone metabolism of filial mice and intervention of Se. Fourth, we observed the pathological change by histomorphometry and ultrastructure of cerebrum and hippocampus. At last, we detected the expression level of NSE, SYP, RC3, α-tubulin, TRα1, TRβ1 and G0α in cerebrum of filial mice with excess iodine intake and intervention of selenium by real-time quantitative PCR, immunohistochemistry and western-blot, and try to study the molecular mechanism of the effect of excess iodine on neuron development and intervention of selenium from the three aspects of neuron development, thyroid hormone receptor and signal transmission. The results were summarized as follow:Part oneEstablishment of excess iodine model in maternal mice and intervention of selenium on effects of excess iodineObjective To establish excess iodine model of maternal mice and observed the effects of excess iodine on thyroid hormone metabolism and intervention by different doses of selenium in maternal mice and establish the optimal dose range of selenium.Methods 240 weanling Balb/c mice were divided into 8 groups randomly. Normal control group（NC） was given taper water; excess iodine（EI） control group was given drinking water containing 3000μg/L iodine; C～H groups were selenium supplementation groups and given drinking water containing 0.1, 0.2, 0.3, 0.4, 0.5, 0.75mg/L selenium, respectively, besides 3000μg/L iodine. After four months, such indices were determined as urinary iodine and selenium, hepatic selenium, thyroid hormones in serum, type I iothyronine deiodinase （D1） activity and mRNA in liver, kidney and thyroid gland Thyroid was used for histological examination.Result 3000μg/L iodine could induced diffused colloid goiter. Median of urinary iodine, and serum T₄ level was significantly higher in excess iodine than in normal control, and median of urinary selenium, hepatic selenium level and T₃ level decreased significantly in excess iodine group than in normal control （P<0.05）. Activity and mRNA level of D1 in liver and kidney was decreased significantly in excess iodine group compared with normal group （P<0.05）. Supplementing Se alleviated goiter, enhanced hepatic selenium level and T₃ level and activity and mRNA level of D1, lowered serum T₄ level significantly （P<0.05）. Under the conditions of this study, the optimal dose range of selenium intervention was 0.2 0.4mg/L.Conclusion Excess iodine model of Balb/c was established successfully and 3000 μ g/L iodine intake can lead to goiter and abnormal thyroid hormone metabolism. Supplementing Se improved thyroid hormone metabolism. It is proposed that the optimal dose range of selenium was 0.2～0.4mg/L and supplementing selenium improves thyroid hormone metabolism in maternal mice with excess iodine. The results lay a foundation for exploring the intervention of selenium on neuron development of cerebrum in filial mice with excess iodine.Part twoEffects of excess iodine on thyroid hormone metabolism in pregnant mice and intervention by different doses of SeleniumObjective To observe the effects of excess iodine on thyroid hormone metabolism and intervention of selenium, and explore the optimal dose range of selenium.Methods 240 weanling Balb/c mice were divided into 8 groups randomly. Normal control group（A） was given taper water; excessive iodine（B） control group was given drinking water containing 3000μg/L iodine; C^H groups were selenium supplementation groups （SS） and given drinking water containing 0.1, 0.2, 0.3, 0.4, 0.5, 0.75mg/L selenium, respectively, besides 3000μg/L iodine. Four months later, urinary iodine concentration of female mice was determined. Then the mice were mated （female: male = 2:1） and the morning of appearance of a vaginal plug was taken as 0.5 day （0.5d） of pregnancy. On the 19.5d of pregnancy, pregnant mice were killed and the uteri were cut open to take out placenta immediately. Meanwhile, serum of pregnant mice was used for thyroid hormone level determination. Liver, kidney and placenta of 12.5d and 19.5d pregnant mice were used to determine the selenium level, and the activity and mRNA level of deiodinase.Results ①Excess iodine lowered significantly hepatic selenium level, and selenium nutritional status in pregnant mice was improved by supplementing selenium （P<0.05）. Compared with EI group, selenium level in liver and placenta increased in 0.2mg/L～0.75mg/L or 0.3mg/L～0.75mg/L SS groups, respectively. ②Excess iodine reduced placenta weight （P<0.05）. Placenta weight was significant higher in 0.3mg/L SS group than that in EI group （P<0.05）. ③Excess iodine enhanced significantly serum T₄ level and lowered serum T₃ level, and selenium supplementation decreased serum T₄ and increased T₃ from 0.1 to 0.5mg/L selenium dose （P<0.05）. No change was found in 0.75mg/L SS group. ④Excess iodine reduced significantly activity of D1 in liver and kidney, and mRNA level of hepatic D1. A dose-dependant increase of D1 activity in liver and kidney was observed in SS groups from 0.2 to 0.5mg/L selenium dose （P<0.05）. Compared with EI group, D1 mRNA expression in liver markedly increased in 0.2 ～ 0.5mg/L SS groups, and in kidney increased significantly in 0.3～0.75mg/L SS group （P<0.05）. ⑤Excess iodine reduced significantly D2 activity in placenta and uterus, and enhanced D3 activity in uterus on pregnant day 19.5 （P<0.05）. Selenium supplementation enhanced D2 activity in placenta and uterus at a certain range of doses （P<0.05）, but had no effect on the D3 activity in placenta. D3 activity in 19.5d uterus decreased obviously in 0.2～0.75mg/L SS groups.Conclusion Excess iodine influences on deiodinase in liver, kidney, placenta and uterus, and thyroid hormone metabolism in pregnant mice. Excess iodine finally may influence on thyroid hormone metabolism in fetus. Selenium supplementation resulted in an elevation of selenium level in mice with excess iodine intake and had a favorable intervention on the embryo toxicity induced by excessive iodine intake. Supplementing selenium influences on maternal-fetal thyroid hormone level by regulating activity of deiodinase. Under the conditions of this study, the optimal dose range of selenium was 0.2～0.4mg/L. It is initiated that supplementing seleniumalleviates the influences of excess iodine on filial mice during pregnancy.Part ThreeEffects of excess iodine on thyroid hormone metabolism in filial miceand intervention by different doses of seleniumObjective To observe the thyroid hormone metabolism in filial mice with excess iodine and intervention of selenium by different dosesMethods 240 weanling Balb/c mice were divided into 8 groups. Normal control group（NC） was given taper water; excessive iodine（EI） control group was given drinking water containing 3000μg/L iodine; C～H groups were selenium supplementation groups （SS） and given drinking water containing 0.1, 0.2, 0.3, 0.4, 0.5, 0.75mg/L selenium, respectively, besides 3000μg/L iodine. Four months later, urinary iodine concentration of female mice was determined. Then the mice were mated （female: male=2:1） and the morning of appearance of a vaginal plug was taken as 0.5 day （0.5d） of pregnancy. Thyroid hormones, and activity and mRNA of deiodinase in serum, cerebrum, liver, kidney and BAT of filial mice were measured on postnatal day 0, 14 and 28. Thyroid gland of filial mice was used for histological examination on postnatal day 14.Results Excess iodine induced diffused colloid goiter of filial mice on postnatal day 14 and supplementing selenium by different doses alleviated the goiter, but 0.75mg/L selenium has little effects. Hepatic selenium level fell in filial mice in EI group, but no significant difference compared with normal control. Excess iodine lowered significantly T₄ level in serum, T₄ and T₃ level in cerebrum, activity and mRNA level of D3, activity of D1 in liver and kidney, meanwhile, enhanced significantly activity and mRNA level of D2 in cerebrum and BAT on postnatal day 0 and 14 （P<0.05）. Supplementing Selenium antagonized the influences induced by excess iodine. No significant difference was found in all indices between all groups on postnatal day 28.Conclusion Excess iodine and high T₄ in serum may pass through placenta to fetus and results in diffused colloid goiter and abnormal synthesis and release of thyroid hormone and hypothyroidism in filial mice. Although excess iodine brought about relative selenium deficiency in maternal mice, not significant selenium deficiency in filial mice. It is proposed that supplementing selenium can antagonize abnormal histo-morphalogy and function induced by excess iodine in filial mice through influencing on thyroid hormone metabolism in maternal mice. The optimaldose range of selenium was 0.2～0.4mg/L.Part FourThe effects of excess iodine on histo-morphalogy and ultrastructure of neuron in cerebrum of filial mice and intervention of seleniumObjective To observe the pathological change of cerebrum and ultrastructure of neuron in filial mice with excess iodine intake and selenium intervention.Method Animal treatment and mating was the same as the part three. The pathological change of cerebrum and ultrastructure of neuron in hippocampus were observed by HE and electron microscope.Results In EI group, the cells in the cerebrum are packed closer together and smaller, thus leading to a decrease in the overall size of the brain, staining thicker in nuclear, heterochromatin obviously increased and the degree of cell differentiation is lower in filial mice on postnatal day 14 compared with NC. Under electron microscope, nucleus and the ratio of nuclear/cytoplasm is bigger, cytoplasm surrounding nucleus reduces, nuclear membrane is thinner, microtubule and microfilament of axon and dendrites reduces, the number of cellular organelle reduces in EI group. The results demonstrate that excess iodine results in a delay of brain development. Supplementing selenium alleviates the effects of excess iodine. Conclusion The new ideas are brought forth that excess iodine leads to abnormality in histo-morphalogy and ultrastructure of cerebrum and delay in brain development, and supplementing selenium improves the brain development. The study on morphyology and ultrastructure of cerebrum lays a foundation of selenium intervening intelligence under the condition of excess iodine intake. Part Five Molecular mechanism of effects of excess iodine on neurondevelopment in filial mice and intervention of seleniumObjective To study the molecular mechanism of the effects of excess iodine on neuron development in filial mice and intervention of selenium by real-time quantitative PCR, immunohistochemistry and western-blot from the three aspects of neuron development, thyroid hormone receptor and signal transmission.Methods 120 weanling Balb/c mice were divided into 4 groups. Normal control group（NC） was given taper water; excess iodine（EI） control group was given drinking water containing 3000μg/L iodine; selenium（Se+） was given drinking water containing 0.2mg/L selenium; selenium supplementation group （EI+Se+） was given drinking water containing 0.2 mg/L selenium, respectively, besides 3000μg/L iodine. Four months later, urinary iodine concentration of female mice was determined. Then the mice were mated （female: male=2:1） and the morning of appearance of a vaginal plug was taken as 0.5 day （0.5d） of pregnancy. Cerebrum of filial mice on postnatal day 0,14 and 28 was taken out for measurement.Results Excess iodine down-regulated the expression of NSE, SYP, RC3 in cerebrum of filial mice on postnatal day 0 and 14, and α—tubulin on postnatal day 0 （P<0.05）, delayed the developmental downregulation of α—tubulin, and up-regulated the expression of TRα1,TRβ1 and Goα on postnatal day 0 and 14 （P<0.05）. No significant difference was found in the expression level of NSE, SYP, α—tubulin, RC3, TRα1, TRβ1and G0α between four groups on postnatal day 28. Supplementing selenium antagonized the effects induced by excess iodine.Conclusion Excess iodine influences development and mature of neuron, dendrites and synapse in cerebrum of filial mice and supplementing selenium antagonized the effects induced by excess iodine from molecular mechanism. The new ideas are brought forth that selenium intervened on development of neuron of cerebrum in filial mice by intervening on thyroid hormone metabolism in maternal and filial mice with excess iodine.更多还原