饲料锌过量对幼鼠脑发育及学习记忆的影响及其机理探讨

目的观察锌过量对幼鼠脑发育和学习记忆行为的影响。方法从哺乳期开始建立过量锌幼鼠模型,采用电镜观察、神经生化和神经行为观察等方法。结果随饲料锌含量的增加幼鼠大脑及海马重量减少,血清及海马锌增高。过量锌１、２组（ＺＥ１、ＺＥ２组）幼鼠主动回避反应（ＡＡＲ）习得率及活动明显低于自由喂养组（ＡＬ组）及ＺＥ２组的配对组（ＰＦ组）,ＺＥ２组的恢复组（ＺＥ２Ｒ组）ＡＡＲ习得率也明显低于ＡＬ和ＰＦ组,但明显高于ＺＥ２组。ＰＦ组与ＡＬ组ＡＡＲ习得率差异无显著性,但活动较ＡＬ组多。ＺＥ２组海马一氧化氮含量增加而生长抑素含量减少,脑组织兴奋性氨基酸和抑制性氨基酸总量增高,尤其是谷氨酸增高更为明显。ＺＥ２组海马ＣＡ１区神经元、胶质细胞及细胞器均有不同程度变性、坏死,突触小泡破裂。结论过量锌饲料明显影响幼鼠脑发育和功能,其机理是多方面的     

饲料锌对大鼠单胺类递质和锌,铜,铁含量的影响

为研究缺锌及高锌饲料影响大鼠脑发育和学习记忆的机理，选择断乳１～２天健康雄性Ｗｉｓｔａｒ大鼠，建立缺锌组（ＺＤ）、高锌组（ＺＨ）、对照组（ＡＬ）模型。采用原子分光光度计火焰法测定血清和脑锌、铜、铁含量，用ＨＰＬＣ电化学法测定脑组织单胺类递质的含量。结果表明：缺锌及高锌饲料影响大鼠生长发育、食欲和活动状况；ＺＤ组血清和脑锌、铁含量低于ＡＬ组，而脑铜含量高于ＡＬ组，ＺＨ组则血清锌明显高于ＡＬ组，而血清和脑铜、铁含量均明显低于ＡＬ组；ＺＤ组脑组织５ＴＨ及ＺＨ组脑ＮＥ和５ＴＨ明显低于ＡＬ组，而ＺＤ及ＺＨ组５ＨＩＡＡ则明显高于ＡＬ组。提示，缺锌与高锌时大鼠脑组织单胺类递质的紊乱及血清和脑组织锌、铜、铁水平的异常可能是大鼠脑发育和学习记忆障碍的生化基础之一。     

饲料缺锌对幼鼠脑发育和学习记忆的影响

从哺乳期开始建立缺锌幼鼠模型，采用电镜观察、神经生化和神经电生理等方法，观察饲料缺锌对幼鼠脑发育和学习记忆的影响并探讨其机理。结果如下：①缺锌组脑重、海马重及血清、海马锌含量均明显低于正常组。②缺锌组ＬＴＰ（ｌｏｎｇ－ｔｅｒｍｐｏｔｅｎｔｉａｔｉｏｎ）诱发率为０，其主动回避反应习得率明显低于ＬＴＰ诱发率为１００％的正常组。③大脑皮层及海马组织兴奋性和抑制性氨基酸以及谷氨酸、γ－氨基丁酸含量、海马一氧化氮含量缺锌组均明显高于正常组，而海马生长抑素含量及锥体细胞核ＤＮＡ含量则缺锌组明显低于正常组。④海马锥体细胞突触小泡较正常组减少。提示膳食缺锌明显影响幼鼠脑发育及功能。     

锌对大鼠生长发育及组织核酸和蛋白质代谢的影响

通过大鼠缺锌（ＺＤ）、高锌（ＺＨ）模型，研究对生长发育及组织核酸和蛋白质代谢的影响。结果：（１）ＺＤ、ＺＨ组的体重、体重增长值、饲料效价均低于自由喂养（ＡＬ）组，Ｐ＜０．０１；（２）ＺＤ、ＺＨ组的胸脖、脾脏重量低于ＡＬ组，Ｐ＜０．０１。但其它内脏的重量，组间无显著差异；（３）ＺＤ、ＺＨ组的心、肝、脑、肺、肾、睾丸的内脏指教大于ＡＬ组，但胸脖、脾脏指数则小于ＡＬ组；（４）ＺＤ组的胸腺、脾脏、睾丸、脑细胞小于ＡＬ组，Ｐ＜０．０５或Ｐ＜０．０１；（５）ＺＤ，ＺＨ组的胸腺、脾脏、骨髓细胞增殖指数低于ＡＬ组，Ｐ＜０．０１；ＺＤ组的肝脏、睾丸、脑细胞的增殖指数低于ＡＬ组，Ｐ＜０．０５或Ｐ＜０．０１。（６）ＺＤ组的胸腺、脾脏、睾丸、脑细胞的ＤＮＡ和蛋白质含量低于ＡＬ组，Ｐ＜０．０５或Ｐ＜０．０１；胸腺、脾脏、脑细胞的蛋白质含量低于ＡＬ组，Ｐ＜０．０５或Ｐ＜０．０１；（７）ＺＤ组的血清总蛋白、白蛋白低于ＡＬ组，Ｐ＜０．０１。提示缺锌或高锌均可抑制生长发育及组织核酸和蛋白质代谢     

缺锌对大鼠脑发育的影响

本文通过建立大鼠缺锌（ｚｉｎｃｄｅｆｉｃｉｅｎｃｙ，ＺＤ）、常锌配对（ｐａｉｒｆｅｅｄｉｎｇ，ＰＦ）模型，从微观及宏观角度，较深入地研究缺锌对学习记忆的影响。结果表明：（１）ＺＤ组的摄食量、体重增长值、饲料效价均非常显著地低于ＰＦ组。（２）ＺＤ组脑的Ｇ０／Ｇ１．期细胞高于ＰＦ组，而Ｓ＋Ｇ２／Ｍ期细胞、细胞容积、脑细胞ＤＮＡ、ＲＮＡ含量均低于ＰＦ组（Ｐ＜０．０５或Ｐ＜０．０１）。（３）ＺＤ组脑细胞内的ｃＡＭＰ高于而ＮＯ含量低于ＰＦｊＨ（Ｐ＜０．０１）。（４）ＺＤ组血清锌和海马锌含量非常显著地低于ＰＦ组。（５）ＺＤ组全脑锌含量无显著下降，然脑铜含量较高，铁含量极低，与ＰＦ组比较有非常显著的差异。（６）ＺＤ组海马ＣＡ１区的ＬＴＰ诱出率为０。串刺激前后ＰＳ峰潜伏期和幅度无明显变化，而ＰＦ组ＬＴＰ诱出率为１００％，串刺激后ＰＳ峰潜伏期缩短，峰幅度明显增高。（７）ＺＤ组海马ＣＡ，区超微结构表现椎体细胞突触内突触小泡减少。（ｓ）ＺＤ组大鼠主动回避行为习得率为２４％，非常显著地低于ＰＦ组的６４％。     

锌对大鼠学习记忆影响的研究

通过行为观察、脑内电活动记录和海马组织结构观察，研究生物体内缺锌及过量锌对学习记忆影响。结果表明，低锌和锌过量组大鼠穿梭箱主动回避反应（ＡＡＲ）习得率、海马突触电位效应均差于常锌组。电镜提示，（１）低锌组表现为突触内突触小泡减少；（２）过量锌组表现为神经元、胶质细胞和突触呈不同程度变性。提示，生物体内缺锌及过量补锌均可导致学习记忆障碍。     

锌对免疫器官的影响

通过建立大鼠缺锌（ＺＤ）、高锌（ＺＥ）模型，研究锌对免疫器官——骨髓、胸腺、脾脏的影响。结果表明：（１）ＺＤ、ＺＥ组体重、体重增长值、饲料效价均非常显著地低于配对（ＰＦ）组和自由喂养（ＡＬ）组，缺锌补锌（ＺＤ＋ＡＬ）组达正常水平。（２）ＺＤ组血清、毛发、股骨、肝脏锌均非常显著地低于ＰＦ、ＡＬ组，而ＺＥ组则相反，ＺＤ＋ＡＬ组达正常水平。（３）ＺＤ、ＺＥ组的胸腺重量、胸腺指数、胸腺肽量和胸腺活性均非常显著地低于ＰＦ、ＡＬ组，ＺＤ＋ＡＬ组达正常水平。（４）ＺＤ、ＺＥ组脾脏重量、脾脏指数均非常显著地低于ＰＦ、ＡＬ组，ＺＤ＋ＡＬ组达正常水平。（５）ＺＤ、ＺＥ组骨髓细胞３Ｈ一ＴｄＲ掺入率和外周血白细胞总数显著下降，其中尤以淋巴细胞减少为着。（６）骨髓细胞、脾脏淋巴细胞周期显示ＺＤ、ＺＥ组静止期细胞明显增高，而增殖期细胞下降，与ＰＦ、ＡＬ组间差别非常显著。以上结果提示，适量锌有促进免疫器官——骨髓、胸腺、脾脏发育和功能活动的作用。而缺锌和高锌则抑制免疫器官的发育和免疫细胞的功能。     

饲料锌对大鼠血清、海马、皮层一氧化氮含量的影响

通过饲料锌不同含量的摄入，建立了低锌（ＺＤ），过量锌（ＺＥ），及正常锌（ＺＮ）大鼠模型，并检测了大鼠血清、皮层、海马一氧化氮（ＮＯ）含量，以探讨锌与ＮＯ的联系。结果表明ＺＤ、ＺＥ组体ｔ增长值、饲料效价明显低于ＺＮ组（Ｐ＜０．０１）。ＺＤ组血清、海马锌明显低于ＺＮ组，而ＺＥ组则明显高于ＺＮ组。ＮＯ检测显示ＺＤ组血清、海马ＮＯ明显高于ＺＮ组，皮层ＮＯ与ＺＮ组无显著性差异。ＺＥ组血清、皮层ＮＯ非常显著地低于ＺＮ组，海马ＮＯ比ＺＮ组明显增高，但低于ＺＤ组。     

锌缺乏对脑内皮素影响的实验观察

从分娩当日建立幼鼠缺锌动物模型，并设对照组，于５６日龄进行实验。原子吸收分光光度计检测锌含量，放免法测定内皮素含量，罗向东法测定一氧化氮（ＮＯ）。结果：（１）缺锌组幼鼠体重、脑重、血清和脑组织锌均明显低于对照组，（２）缺锌幼鼠血浆、皮层和小脑内皮素含量均明显低于对照组，而血浆和海马ＮＯ含量均明显高于对照组。可见缺锌使幼鼠血浆和脑组织内皮素含量明显减少，ＮＯ含量显著增加，这也可能是缺锌使脑发育和功能障碍的机制之一。     

缺锌对大鼠胸腺发育影响及机理探讨

目的：研究缺锌对胸腺发育及Ｔ淋巴细胞活化与增殖功能的影响。方法：建立大鼠缺锌（ＺＤ）模型，测定胸腺肽、胸腺激素活性、胸腺Ｔ淋巴细胞转化、活化Ｔ淋巴细胞钙离子和活性钙调蛋白等。结果：１．ＺＤ组的血清、毛、胸腺细胞锌含量低于对照（ＡＬ）组（Ｐ＜０．０１）。２．ＺＤ组的胸腺重量、指数和细胞大小低于ＡＬ组（Ｐ＜０．０１或Ｐ＜０．０５）。３．ＺＤ组胸腺的胸腺肽含量、胸腺素活性低于ＡＬ组（Ｐ＜０．０１）。４．ＺＤ组胸腺细胞的ＤＮＡ、ＲＮＡ和蛋白质含量低于ＡＬ组（Ｐ＜０．０１）。５．ＺＤ组胸腺细胞中增殖期细胞（Ｓ＋Ｇ２／Ｍ）、增殖指数（ＰＩ）低于ＡＬ组（Ｐ＜０．０１）。６．ＺＤ组胸腺细胞内ｃＡＭＰ含量与ｃＡＭＰ／ｃＧＭＰ比值高于ＡＬ组（Ｐ＜０．０１）。７．ＺＤ组胸腺细胞内的Ｃａ２＋、ＣａＭ、ＩＬ－２、ＩＬ－２Ｒα及Ｔ细胞增殖率低于ＡＬ组（Ｐ＜０．０１）。８．ＺＤ组胸腺Ｔ淋巴细胞内的锌离子与Ｃａ２＋、ＣａＭ、ＩＬ－２、ＩＬ－２Ｒα、Ｔ淋巴细胞增殖率呈正相关（Ｐ＜０．０１）；Ｃａ２＋与ＩＬ－２、ＩＬ－２Ｒα呈正相关（Ｐ＜０．０１）；ＣａＭ与ＩＬ－２、ＩＬ－２Ｒα呈正相关（Ｐ＜０．０１）。结论：适量锌有促进胸腺发育、胸腺激素活?     

锌对仔鼠中枢神经系统胶质酸性纤维蛋白表达的影响

目的　探讨微量元素锌缺乏与胶质酸性纤维蛋白 ( GFAP)表达的关系及锌调节胶质细胞分化的机制。方法　给处于孕期及哺乳期的 ICR母鼠喂饲含不同锌水平饲料 ,采用 West-ern blot技术检测其仔代胚胎、大脑、小脑及肝组织中 GFAP的表达情况 ;同时在穿梭箱内检测成年仔鼠 ( 70日龄 )的学习能力 ;行为实验结束后 ,在仔鼠的海马脑片上进行诱导长时程增强 ( LTP)实验。结果　实验仔鼠小脑在新生期 (出生第 1天 ,P1 )开始表达 GFAP,而大脑在出生后第 5天( P5)才开始有 GFAP印迹出现 :之后至成年小脑及大脑持续表达 GFAP;实验鼠肝组织在发育全过程中均未见有 GFAP印迹。比较各实验组 GFAP表达量为 :P1至 P5期非缺锌组 ( 30 mg/kg及1 0 0 mg/kg) GFAP杂交条带明显强于缺锌组 ( 1 mg/kg及 5mg/kg) ;P1 0至成年期 ,缺锌组 ( 1 mg/kg及 5mg/kg)大脑及小脑 GFAP的杂交条带反而强于非缺锌组 ( 30 mg/kg及 1 0 0 mg/kg) ,其强度与膳食锌呈负依赖关系。行为学检测表明 ,轻度缺锌组 ( 5mg/kg)达到学会标准所需次数明显多于高锌组 ( 1 0 0 mg/kg) ;电生理检测表明 ,轻度缺锌组仔鼠海马脑片上诱导的 LTP明显低于高锌组上所诱导的。结论　补充锌在发育早期可促进神经前体细胞向神经胶质细胞分化及 GFAP表达 ;神经胶质细胞分化     

缺锌对生长大鼠学习记忆功能及生长状况的影响

目的 :　研究缺锌对大鼠生长、学习和记忆功能的影响。方法 :　进行了三系列实验 ,第 1、2系列分组均为缺锌组 (ZD)、对喂组 (PF)和缺锌补锌组 (ZS) ,但第 1系列饲养期为 35d,缺锌补锌组缺锌 2 1 d后补锌 ;第 2系列饲养期 2 8d;第 3系列分组为缺锌组、对喂组和自由采食组(AL) ,饲养期 2 8d,全程观察生长过程 ,定期称重 ,并于实验结束前 1 w内用避暗法测定各组大鼠的学习和记忆功能。结果 :　三次实验均表明 ,ZD组大鼠生长、学习和记忆功能降低 ,而补锌后 ,则能逆转上述状况。结论 :　锌不仅影响生长 ,且与学习和记忆等脑的高级功能有关     

边缘性维生素A缺乏及干预对幼鼠海马神经元形态与功能的影响

目的了解胚胎期开始的边缘缺乏(MVAD)对幼鼠海马神经元的形态及功能造成的损害,以及从新生儿期开始维生素A干预,能否使这种损害得以恢复。方法 11只健康母鼠于交配前3 w开始喂饲含VA 400 IU/kg的MVAD饲料,随机抽取其子鼠19只于断乳后继续喂饲同样的MVAD饲料为VAD组。另外随机抽取13只子鼠于出生0 d开始喂饲其母鼠含VA 6500 IU/kg的正常饲料,断乳后继续饲正常饲料为干预(VAI)组。随机抽取7只健康母鼠的10只子鼠作为正常对照(control,C)组,其饲料为含VA 6500 IU/kg的正常饲料。各组幼鼠均于7 w龄处死。用高效液相色谱法(HPLC)检测血清VA浓度。对海马切片进行HE染色,了解其神经元形态及细胞核大小的改变。运用电生理技术检测幼鼠离体海马脑片CA1区长时程增强(LTP),并在VAD组人工脑脊液(ACSF)中直接加入视黄酸(RA)后检测LTP。用透射电镜观察强直刺激前后,海马CA1区突触超微结构的变化。结果 MVAD孕鼠交配时血清VA浓度明显低于对照组。VAD组血清VA浓度明显低于C组,VAI组的血清VA浓度低于C组水平,但明显高于VAD组。海马CA1区锥体细胞层神经元细胞核的面积,VAD组明显小于C组,VAI组大于VAD组,与C组比较无明显差别。C组海马CA1区群峰电位增长幅度明显大于VAD组,VAI组小于C组,大于VAD组(P<0.05);VAD组脑片的ASCF中加入RA,其群峰电位增长幅度由(22.86±3.26)%上升到(59.08±7.22)%(P<0.01),与C组无显著差异。强直刺激后的C组与空白对照组(BC)比较,其海马CA1区突触的活性区长度和突触后致密物(PSD)厚度均明显增加,突触界面模拟圆半径明显减小,突触间隙宽度没有明显差异;强直刺激后,C组突触活性区长度明显大于VAD组,与VAD+RA组比较无显著差异,C组和VAD+RA组的突触界面模拟圆半径小于VAD组。结论 MVAD可导致少量CA1区神经元缺失和坏死,并减小了海马神经元细胞核的面积。同时直接影响海马神经元LTP的诱发,以及减小了LTP诱发后突触超微结构变化的程度。新生儿期开始的VAI可使MVAD对海马神经元的影响得到部分恢复。     

缺锌对生长期大鼠行为及海马细胞钙状态的影响

为探讨缺镜对生长期大鼠行为以及海马细胞内游离钙([Ca^2 ])和活性钙调素（CaM)水平的影响。选用21只雄性Wi star大鼠，随机分为缺锌组，对喂组，对照组，缺锌组组饲以缺锌饲料，对喂和对照组饲以普通饲料，喂饲3周后，用旷场试验进行为行为测定，之后处死大鼠，分别用Fura-2双波长荧光法和流式细胞术测定动物海马细胞[(Ca^2 ])i和活性CaM水平。结果表明，缺锌组组大鼠在旷场内的行为与对照组出现明显差异，其海马细胞[Ca^2 ]i明显高于对照和对喂组，缺锌组和对喂组大鼠海马细胞活性CaM水平均明显低于对照组，缺锌组组大鼠细胞活性CaM水平也明显低于对喂组，缺锌对生长期大鼠行为的影响可能与其影响海马神经元的钙状态有关。     

Studies of marginal zinc deprivation in rhesus monkeys: II. Pregnancy outcome

A marginal state of zinc deficiency was induced in the pregnant nonhuman primate, Macaca mulatta, by feeding a diet containing 4 ppm zinc beginning at conception. Pregnancy outcome of marginally zinc-deficient monkeys (ZD) was compared to both pair-fed (PF) and ad libitum fed (AL) control animals (100 ppm zinc). Stillbirths, abortions, and delivery complications were more frequent in both ZD and PF dams than in AL controls; no malformations were detected (maternal plasma zinc was normal during organogenesis). Male ZD neonates weighed significantly less than same sex controls; also, in relation to colony norms, 7/8 ZD males, 2/8 ZD females, and 1/10 PF controls were of low birth weight. Further, plasma zinc and iron levels were lower in ZD neonates than in AL and PF controls. ZD neonates also had reduced muscle tonus. Birth weight and maternal plasma zinc concentration were negatively correlated in ZD group but positively correlated in AL and PF groups. Indeed, maternal plasma zinc concentration alone did not identify a state of zinc deficiency which impaired fetal growth in monkeys.     

Effects of isolated zinc deficiency on the composition of skeletal muscle, liver and bone during growth in rats

We investigated the effects of zinc deficiency on body composition by using intragastric force-feeding to obviate decreased food intake and altered eating patterns. Weanling male Sprague-Dawley rats were fed a purified zinc-deficient diet: the ad libitum-fed control group (AL; eight rats) was given powdered diet and water containing 25 ppm zinc; the zinc-replete group (ZN; nine rats) was force-fed a diet blended with water containing zinc in an amount of equal caloric intake to the AL group and allowed access to water containing zinc. The zinc intake of ZN rats was approximately twice that of AL rats based on water intake. The zinc-deficient group (ZD; 13 rats) was fed similarly to the ZN group except deionized water was used for diet preparation and drinking water. After 8 d, body and muscle weight were lower in the ZD group than in the ZN group. Femur weights were similar in the two groups. Serum, liver and femur zinc concentrations were 85, 22 and 42% lower, respectively, in the ZD group than in the ZN group. Serum glucose, relative liver weight, liver glycogen and liver lipids were higher, but muscle and liver DNA were lower in the ZD group than in control groups.     

Zinc deficiency is associated with increased brain zinc import and LIV-1 expression and decreased ZnT-1 expression in neonatal rats

Zinc (Zn) deficiency has been associated with adverse behavioral outcomes in infants and children. However, Zn deficiency does not affect brain Zn concentration, suggesting that brain Zn homeostasis is tightly regulated. The recent identification of Zn-specific transport proteins allowed us to examine effects of low Zn intake on tissue Zn level, brain Zn uptake, and zinc transporter expression and localization in neonatal rat brain. Female rats were fed diets differing only in Zn content [7, moderately zinc deficient (ZD); 10, marginally zinc deficient (MZD); or 25 mg Zn/kg, control] and pups were killed on postnatal d 11. Plasma and brain Zn concentrations were measured, brain Zn uptake was assessed using (65)Zn, brain metallothionein-I and -III; LIV-1, zinc transporter ZnT-1, and ZnT-3 expression was measured by semiquantitative RT-PCR. LIV-1 localization in the brain was determined by immunohistochemistry; brain and hippocampi LIV-1 and ZnT-1 protein expressions were measured by Western blotting. Plasma Zn concentration was lower in MZD and ZD pups, whereas brain Zn concentration was not affected. Brain Zn uptake was higher in MZD and ZD rats compared with controls. Metallothionein-I and ZnT-1 expressions were lower and LIV-1 expression was higher in the whole brain of MZD and ZD pups. Metallothionein-III and ZnT-3 mRNA expressions were not affected. LIV-1 was localized to the plasma membrane of many brain cell types, including hippocampal pyramidal neurons and the apical membrane of the choroid plexus. Our results indicate that Zn deficiency results in alterations in Zn transporter expression, which facilitates increased brain Zn uptake and results in the conservation of brain Zn during Zn deficiency.