氯化甲基汞致脑发育损伤形态学研究

目的:探讨氯化甲基汞(MMC)致大鼠不同发育阶段脑组织形态结构改变。方法:雌性Wistar大鼠体重(120±20)g,随机分为3个实验组和对照组各30只。3个实验组母鼠从妊娠前90天至仔鼠出生后30天连续喂饲含有不同剂量(0.75、1.50和3.00 mg/kg)MMC的普通饲料,对照组给予普通饲料。脑切片经苏木精-伊红染色,在光镜下观察长期接触低剂量MMC仔鼠脑组织形态结构。采用荧光原位末端标记法,在激光共聚焦显微镜下计数两组生后不同时间点仔鼠大脑、小脑和海马发生凋亡的神经元,以PCD阳性率表示凋亡的多少。结果:在实验设计的接触剂量下,仔鼠大脑、小脑和海马神经元体积缩小、固缩,核染色质致密等凋亡形态特征。实验组和对照组生后不同时间点仔鼠脑神经元都存在凋亡。结论:大鼠长期低剂量接触不同浓度MMC可使其生后仔鼠大脑、小脑和海马部分神经元出现凋亡形态学改变,随仔鼠脑汞含量升高神经元凋亡率明显增加。     

宫内暴露甲基汞对幼鼠脑发育损伤机制研究

为研究孕期暴露甲基汞对婴幼儿脑发育损伤机制,我们建立了甲基汞孕期暴露实验动物模型,采用3.0mg/kg剂量对怀孕后母鼠染毒。仔鼠出生后不同天数对仔鼠大脑、海马和小脑脑汞含量进行测定和观察,研究不同发育阶段仔鼠的大脑、海马、小脑的脑汞含量,通过分析单位重量脑汞含量得出海马中分布显著高于大脑和小脑中的结论;采用TUNEL法检测脑神经细胞凋亡,观察脑神经细胞凋亡状况;采用流式细胞术对不同发育阶段仔鼠三个那脑区进行比较探讨细胞周期改变规律。     

母鼠低剂量接触甲基汞所致仔鼠学习能力及脑海马超微结构的变化

[目的]研究ICR母鼠饮水暴露低剂量氯化甲基汞(MeHgCl)后,仔鼠脑组织的病理组织学变化和脑海马超微结构变化,评价低剂量饮水暴露甲基汞的安全性。[方法]ICR孕鼠随机分为对照组、低剂量组和高剂量组,每组各8只,各组于怀孕第6天起,分别自由饮用蒸馏水和氯化甲基汞含量为0.01、0.1mg/L的蒸馏水,直至哺乳期结束。测试各组仔鼠学习能力,观察仔鼠脑组织病理组织学变化及脑海马超微结构变化。[结果]在对仔鼠进行学习能力测试的水迷宫实验中,对照组、低剂量组和高剂量组成功率分别为81.67%、59.09%和70.00%,低剂量组和高剂量组成功率显著低于对照组(P<0.05)。低剂量组和高剂量组仔鼠脑组织有明显的病理学改变,随着甲基汞染毒剂量的增加,海马区大锥体细胞、大脑神经元和小脑浦肯野细胞嗜酸性增强。电镜结果显示,低剂量和高剂量组脑海马神经细胞有变性,严重者呈暗细胞表现。[结论]实验剂量甲基汞可使仔鼠脑组织发生病理组织学改变,脑海马区超微结构改变,实验剂量甲基汞对于仔代是不安全的。     

母鼠成年前至孕哺期硒与甲基汞联合暴露对子代大鼠小脑的损伤

目的初步探讨硒(selenium,Se)对甲基汞(methylmercury,MeHg)染毒仔鼠小脑损伤作用的影响。方法将24只清洁级雌性SD大鼠按体重随机分为4组,分别为对照组(生理盐水)、硒(0.2 mg/kg)染毒组、甲基汞(1.2 mg/kg)染毒组和甲基汞+硒染毒组,每组6只。采用经口灌胃方式染毒,从交配前8周、妊娠期和哺乳期(出生21 d)连续给母鼠染毒。断乳后,测定仔鼠脑汞、硒的水平,检测小脑组织丙二醛(malondialdehyde,MDA)含量和硫氧还蛋白氧化还原酶(thioredoxin reductase,TrxR)活力。结果甲基汞染毒组和甲基汞+硒染毒组仔鼠脑汞含量高于对照组和硒染毒组,差异均有统计学意义(P0.05);与甲基汞染毒组相比,甲基汞+硒染毒组仔鼠脑汞含量较高,差异有统计学意义(P0.05)。硒染毒组和甲基汞+硒染毒组仔鼠脑硒含量高于对照组和甲基汞染毒组,差异均有统计学意义(P0.05);与硒染毒组相比,甲基汞+硒染毒组仔鼠脑硒含量较高,差异有统计学意义(P0.05)。与对照组相比,甲基汞染毒组仔鼠小脑MDA含量较高,而TrxR活力较低,差异均有统计学意义(P0.05);硒染毒组和甲基汞+硒染毒组仔鼠小脑MDA含量和TrxR活力与对照组相比,差异无统计学意义(P0.05)。结论母鼠成年前至孕哺期甲基汞染毒对子代大鼠小脑造成明显的氧化应激损伤;而硒对甲基汞暴露所致子代大鼠的氧化损伤作用具有拮抗作用。     

氯化甲基汞染毒对亲仔两代ICR小鼠脑、肝、肾中汞分布的影响

[目的]通过ICR孕鼠饮水接触低剂量氯化甲基汞,研究汞在亲仔两代小鼠脑、肝、肾及血清中的分布及其相关性。[方法]ICR孕鼠随机分为对照组、低剂量组(0.01mg/L)和高剂量组(0.10mg/L),于怀孕第6天起分别自由饮用蒸馏水及氯化甲基汞含量分别为0.01、0.10mg/L的蒸馏水直至哺乳期结束,用原子荧光法测定汞在各脏器内的含量,并做血清汞和脏器汞含量的相关性分析。[结果]在低剂量甲基汞作用下,亲仔两代未出现明显的毒性反应。随着染毒剂量的增加,亲仔两代小鼠血清中的总汞含量增加,对照组、低剂量组和高剂量组母鼠血清中总汞含量分别为1.228、2.358和6.195μg/L,仔鼠为0.801、3.217和3.763μg/L,高剂量组和对照组间差别有显著性(P<0.05);随着染毒剂量的增加,各脏器中的总汞含量也增加,对照组、低剂量组和高剂量组母鼠肾脏总汞含量分别为13.890、25.780、253.980ng/g组织湿重,肝脏为3.710、11.520、100.820ng/g组织湿重,脑组织为2.820、3.070、23.810ng/g组织湿重;对照组、低剂量组和高剂量组仔鼠肾脏总汞含量分别为6.940、13.090、102.170ng/g组织湿重,肝脏为2.660、5.450、38.850ng/g组织湿重,脑组织为1.600、2.660、8.120ng/g组织湿重;母鼠和仔鼠脏器中总汞蓄积的模式一样:肾脏>肝脏>脑组织。在低剂量下,母鼠血清总汞含量与肝脏、肾脏、脑组织中的总汞含量的相关系数分别为0.830、0.967、0.802;在高剂量下,与肝脏、肾脏、脑组织的相关系数分别为0.997、0.833、0.850,均有较高的相关性(P<0.05)。而仔鼠在高剂量下血清总汞与肝脏、肾脏、脑组织的相关系数分别为0.737、0.672、0.702,其血清总汞和脏器总汞也有相关性(P<0.05);在低剂量时血清总汞与肝脏、肾脏、脑组织总汞的相关系数分别为0.040、0.300、0.080,没有相关性(P>0.05)。[结论]母鼠接触低剂量甲基汞即可在亲仔两代各脏器中蓄积,亲代血清总汞含量和脏器总汞含量具有明显的相关性;仔代在高剂量时血清总汞含量和脏器总汞含量有明显的相关性,而在低剂量下无相关性。     

燃煤型氟中毒对仔鼠学习记忆及海马区胶质纤维酸性蛋白表达的影响

目的观察母鼠青春期及孕哺期燃煤型氟中毒对仔鼠学习记忆及海马区胶质纤维酸性蛋白(GFAP)表达的影响。方法 48只断乳两周的健康清洁级SD大鼠(雌鼠32只、雄鼠16只),按体重将雌鼠随机分为对照组、低氟组、中氟组、高氟组,每组8只,其中低、中、高氟组饲料含氟量分别为24.4、47.8、106.0 mg/kg;染氟组以燃煤型氟中毒重病区原煤烘干的玉米为主要饲料喂养3个月,对照组及雄鼠食用正常饲料。染氟3个月后雌雄大鼠按2∶1合笼交配,雌鼠妊娠后继续染毒,直至仔鼠断乳,仔鼠断乳后食用正常饲料。计算仔鼠脑脏器系数,以氟离子选择电极法检测仔鼠脑氟含量,以Morris水迷宫检测30 d龄仔鼠学习记忆能力,以Western blot检测仔鼠海马区GFAP的表达水平。结果与对照组比较,各染氟组仔鼠脑脏器系数无明显差异(P0.05);中氟组和高氟组仔鼠脑氟含量升高,差异有统计学意义(P0.05)。与对照组比较,定位航行实验第3、4天的中氟组及高氟组仔鼠平均逃避潜伏期延长,高氟组仔鼠首次到达平台时间延长,且穿越平台次数减少,差异均有统计学意义(P0.05)。与对照组相比,高氟组仔鼠海马区GFAP表达水平增加,差异有统计学意义(P0.05)。结论母鼠燃煤型氟暴露可影响仔鼠学习记忆能力,其机制可能与仔鼠海马区GFAP表达水平增加有关。     

铅对仔鼠海马蛋白激酶C和钙调蛋白表达的影响

目的 研究慢性铅染毒对不同发育时期仔鼠海马蛋白激酶C(PKC)、钙调蛋白(CaM)表达的影响.方法 孕鼠随机分为蒸馏水对照组、0.2%醋酸铅和1.0%醋酸铅组,从怀孕第0灭起开始通过自由饮水染毒.幼鼠出生后,先通过哺乳接触铅,断乳后则自行饮用与其母鼠浓度相同的含铅水.分别于出生后8、50 d处死仔鼠,原子吸收光谱法测定脑铅含量,Western-blotting法观察各组仔鼠海马PKC、CaM的蛋白表达情况.结果 同一发育时期的染铅组仔鼠脑铅含量明显高于对照组,差异有统计学意义(P＜0.01).同一剂量染铅组出生后50 d仔鼠脑铅含最明显高于出生后8 d,差异有统计学意义(P＜0.01).不同发育时期的染铅组仔鼠海马的PKC、CaM的蛋白表达均相应地下降,与对照组相比,差异有统计学意义(P＜0.05).结论 仔鼠海马PKC、CaM的蛋白表达降低可能是铅致仔鼠学习记忆功能损害的分子机制之一.     

铅对仔鼠海马蛋白激酶C和钙调蛋白基因表达与学习记忆的影响

目的 观察慢性铅染毒对仔鼠海马蛋白激酶C(PKC)、钙调蛋白(CaM)mRNA表达的影响,探讨铅神经毒性的分子机制.方法 孕鼠随机分为对照组、0.2%醋酸铅染毒组和1.0%醋酸铅染毒组,从妊娠第0天开始通过自由饮水染毒.幼鼠出生后,先通过哺乳接触铅,断乳后则自行饮用与其母鼠相同的饮用水.出生后8 d内行悬崖回避试验,50 d行跳台试验,随后处死仔鼠,原子吸收光谱法测定脑铅含量,反转录-聚合酶链反应(RT-PCR)法观察各组仔鼠海马PKC、CaM的mRNA表达情况.结果 同一发育时期的染铅组仔鼠脑铅含量明显高于对照组,差异有统计学意义(P＜0.01);同一剂量染铅组出生后50 d仔鼠脑铅含量明显高于生后8 d,差异有统计学意义(P＜0.01).染铅组仔鼠悬崖回避试验完成率和跳台学习成绩明显低于对照组,差异有统计学意义(P＜0.05,P＜0.01).不同发育时期的1.0%醋酸铅染毒组仔鼠海马的PKC、CaM的mRNA表达下降(分别为0.53±0.04、0.59±0.02和0.65±0.01、0.62±0.01),与相应的对照组相比,差异有统计学意义(P＜0.05,P＜0.01).结论 慢性铅染毒可使仔鼠海马PKC、CaM的mRNA表达降低,这可能是铅致仔鼠学习记忆功能损害的分子机制之一.     

碘缺乏对脑发育期大鼠大、小脑~3H-亮氨酸掺入的影响

本文介绍~3H-亮氨酸掺入碘缺乏仔鼠脑组织的实验情况。实验组动物为饲以碘缺乏地区的粮食和水的母鼠所产的仔鼠;对照组动物为饲以补充碘的饲料的母鼠所产的仔鼠。 实验结果为,11日龄仔鼠在注入~H-亮氨酸1—14小时后,实验组每毫克大、小脑组织中的掺入量(dmp)均明显低于对照组(p<0.001);而生后不同日龄(1—30天)的仔鼠,注入~3H-亮氨酸4小时后的dmp,亦是实验组低于对照组(P<0.05),表明碘缺乏可影响仔鼠脑组织蛋白质的合成及脑组织的发育。     

甲基汞对亲仔两代大鼠的神经行为毒性效应

目的探讨大鼠妊娠期甲基汞暴露的母体毒性及对仔代的神经行为毒性效应。方法Wistar孕鼠52只于妊娠第6～9天用甲基汞0.00、0.01、0.05、2.00mg/(kg·d)连续灌胃。分别观察母体毒性 ;常规致畸实验 ;记录205只仔鼠早期生理发育和神经行为发育指标 ;10周龄仔鼠32只进行程序控制行为测试 ;分娩后5周母鼠和10周龄仔鼠各24只进行脑组织形态学观察和单胺类神经递质的测定。实验遵循随机、双盲原则。结果未观察到母体毒性和仔代形态畸形 ;3个暴露组胎仔的体重、尾长低于对照组 (P<0.01) ;各暴露组仔鼠体重增长、早期生理及神经行为发育滞后于对照组 (P<0.05) ;程序控制行为学习成绩比对照组降低 (P<0.05) ,有剂量_效应关系 (rs= -0.7273 ,P<0.01) ;各暴露组母鼠和仔鼠脑组织无形态学改变 ,但单胺类神经递质含量均比对照组显著增高 (P<0.05) ,有剂量_效应关系 (rs=0.7124～0.9257 ,P<0.01)。结论本研究剂量的妊娠期甲基汞暴露未观察到对孕鼠的毒性效应 ,但有轻度胚胎毒性 ,影响仔鼠的神经系统发育 ,导致仔鼠学习记忆能力降低 ,亲仔两代大鼠脑组织中单胺类神经递质的含量增高     

Effect of ethanol intake during lactation on male and female pups' liver and brain metabolism during the suckling-weaning transition period

In rats, a high degree of brain development and myelination occurs during the first 15 days after birth. Ethanol intake by lactating rats modified 12 day-old pups' brain development and metabolism. The aim of the present study was to evaluate the effect of maternal ethanol ingestion during lactation on prepubertal (24-day-old) pups' brain and liver metabolism. Lactating rats (4 male and 4 female litters) were divided into 2 groups: control--received control liquid diet, and ethanol--received liquid diet containing 4% of ethanol. On postnatal day 24, the pups were killed by decapitation. Liver and brain were utilized for measuring Adenosine Tri-phosphate-citrate lyase and malic enzymes activities. Brain slices were incubated in medium containing glucose to determine glucose consumption and oxidation, and lipid synthesis. The ethanol intake decreased male and female pups' body, brain and liver weight. Liver Adenosine Tri-phosphate-citrate lyase activity was decreased only in male pups of the ethanol group. The intake of ethanol solution by the dams increased glucose consumption and oxidation by the incubated female pups' brain slices and decreased glucose oxidation by the male pups' brain slices. It can be concluded that the effects of maternal ethanol intake on pups' development and metabolism are gender-related.     

Mercury, selenium, and cadmium in human autopsy samples from Idrija residents and mercury mine workers

Total Hg and Se concentrations were determined in autopsy samples of retired Idrija mercury mine workers, Idrija residents living in a Hg-contaminated environment, and a control group with no known Hg exposure from the environment. In selected samples we also checked the presence of MeHg. The highest Hg concentrations were found in endocrine glands and kidney cortex, regardless of the group. MeHg contributed only to a negligible degree to the total mercury concentrations in all analyzed samples. In the Hg-exposed groups the coaccumulation and retention of mercury and selenium was confirmed. Selenium coaccumulation with a Hg/Se molar ratio near 1 or higher was notable only in those tissue samples (thyroid, pituitary, kidney cortex, nucleus dentatus) where the mercury concentrations were >1 microg/g. After tissue separation of such samples the majority of these elements were found in the cell pellet. Because the general population is continuously exposed to Cd and possibly also to Pb from water, food, and/or air, in some samples the levels of these elements were also followed. In all examined control tissue samples the average values of Cd (kidney cortex, thyroid, hippocampus, cortex cerebellum, nucleus dentatus) and Pb (thyroid, hippocampus) exceeded the average values of Hg. Cd concentrations were the highest, particularly in kidney cortex and thyroids (microg/g), but no relationship between Cd and Se concentration was evident at the tissue level. Regarding the results in the control group, it is debatable which element is the more hazardous for the general population as concerns neurotoxicity.     

右美沙芬和利鲁唑对甲基汞染毒大鼠神经毒性的影响

目的研究右美沙芬(dextromethorphan,DM)和利鲁唑(riluzole)对甲基汞染毒大鼠神经毒性的影响。方法将健康清洁级Wistar大鼠28只按体重随机分为对照组、氯化甲基汞组、右美沙芬+氯化甲基汞组、利鲁唑+氯化甲基汞组,每组7只。对照组和氯化甲基汞组皮下注射生理盐水溶液,右美沙芬+氯化甲基汞组和利鲁唑+氯化甲基汞组分别皮下注射13.5μmol/kg右美沙芬、21.35μmol/kg利鲁唑。注射2h后,对照组腹腔注射生理盐水,氯化甲基汞组、右美沙芬+氯化甲基汞组、利鲁唑+氯化甲基汞组腹腔注射氯化甲基汞溶液12.0μmol/kg,注射容量均为5ml/kg。连续进行4周,每周5天,每天染毒氯化甲基汞1次,每周一、三、五染毒右美沙芬、利鲁唑。测定大脑皮质中汞(Hg)、谷氨酰胺(Gln)、谷氨酸(Glu)含量以及小脑中琥珀酸脱氢酶(SDH)、Na+-K+-ATP酶、Ca2+-ATP酶活力。结果与对照组相比,氯化甲基汞组大脑皮质中Hg、Glu含量上升,Gln含量降低,小脑中SDH和Na+-K+-ATP酶、Ca2+-ATP酶活力降低,差异均有统计学意义(P0.05或P0.01)。与氯化甲基汞组相比,右美沙芬+氯化甲基汞组和利鲁唑+氯化甲基汞组大脑皮质Hg、Glu含量降低,Gln含量升高,SDH、Na+-K+-ATP酶和Ca2+-ATP酶活力升高,差异均有统计学意义(P0.05或P0.01)。结论甲基汞可扰乱谷氨酸-谷氨酰胺循环,右美沙芬和利鲁唑对甲基汞神经毒性具有一定的拮抗作用。     

Ethanol intake during lactation. II. Effects On pups' liver and brain metabolism.

Lactating rats, with litters adjusted to 8 pups on day 1, were divided into 4 groups: control animals (C), which received water and Nuvilab chow ad libitum, and ethanol animals (E), which received 20% (E20), 10% (E10), or 5% (E5) ethanol diluted in the drinking water and Nuvilab chow ad libitum. On day 12 of life, the pups were weighed and decapitated. The intake of 10% and 20% ethanol solutions by the lactating rats decreased the pups' body weight and liver weight. The pups' liver ATP-citrate lyase activity was decreased in all ethanol groups. The pups' brain weight decreased in E20 only. Glucose metabolism and lactate production were studied in the pups' brain slices, which were incubated at 37 degrees C in Krebs-Henseleit buffer under carbogen in the presence of glucose (5 mM) plus 14C-glucose (0.04 microCi) with or without beta-hydroxybutyrate or insulin. Study of the incubated pups' brain slices showed that the intake of the 20% ethanol solution by the dams increased glucose consumption, oxidation, lactate production, and lipogenesis rate from glucose in all media studied, as compared with findings in the C group. In the pups' brain slices, the lactate production and lipogenesis rate from glucose were higher in E10 than in the C group. The addition of beta-hydroxybutyrate to the incubation medium caused a decrease in glucose oxidation in C, E5, and E20 and an increase in glucose consumption in E10. Ingestion of the 5% ethanol solution by dams decreased the pups' brain lipogenesis rate from glucose in all media studied. We concluded that the effects of maternal alcohol intake on the pups' development and metabolism are dose-dependent. High amounts of ethanol intake (10% or 20%) caused a great impairment in the pups' growth, as well as their liver and brain metabolism. The low dose (5%) did not affect the pups' body weight gain or their brain and liver weight, but it did alter brain glucose metabolism.     

牛磺酸对低水平铅暴露大鼠神经行为与功能的影响

目的　探讨牛磺酸对低水平铅暴露大鼠神经行为与功能的影响。方法　将成年Wistar大鼠随机分为对照 (Cont)组、铅 (Lead)对照组、Lead+0 .5 %牛磺酸 (Tau)组、Lead+1 .0 %Tau组和 Lead+1 .5 % Tau组 ,自孕 9d起 ,各 Tau补充组母鼠饲料中添加不同水平牛磺酸 ,于孕1 6 d至产后 2 5 d,染铅各组饮 0 .1 4%的醋酸铅蒸馏水。仔鼠于生后 2 5 d与母鼠分笼喂养 ,饮食同母鼠。自生后开始观察生长发育及行为发育情况 ,3 0 d开始做辨别学习能力试验。试验结束后 ,处死动物 ,测血铅 ,脑铅 ,单胺类神经递质 ,乙酰胆碱。结果　 1 .各 Tau补充组脑铅含量 (ng/g)低于Lead组 ,高于 Cont组 (P<0 .0 0 1 )。 2 .负向趋地、听觉惊愕、触须定位达标时间 (d)各 Tau补充组短于 Lead组 (P<0 .0 1 ) ,3 .辨别学习能力试验 ,达到学会标准所用时间 (d) ,各 Tau补充组短于 Lead组 (P<0 .0 0 1 )。4.各脑区去甲肾上腺素含量 Lead+1 .0 % Tau组高于 Lead组而与 Cont组无差别 ,各脑区多巴胺含量 Lead组低于 cont组 ,其中小脑、皮层含量低于 Lead+1 .0 % Tau组 (P<0 .0 5或0 .0 1 )。结论　补充适量牛磺酸对低剂量铅暴露大鼠神经系统发育具有保护作用。     

Mercury distribution in the neonatal and adult cerebellum after mercury vapor exposure of pregnant squirrel monkeys

The objectives of the study were (1) to map the detailed localization of mercury in the monkey cerebellum after mercury vapour exposure; (2) to investigate whether there is any difference in mercury distribution between neonatal and adult cerebellum after mercury vapor exposure; (3) to investigate the ability of mercury to accumulate in the cerebellum years after the end of exposure. Pregnant squirrel monkeys were exposed 5 days/week to mercury vapor at a concentration of 0.5 mg Hg/m(3) air 4 or 7 h/day or 1 mg Hg/m(3) air for 4 or 7 h/day. Mercury concentration in the offspring and maternal brains was examined by cold vapor, flameless atomic absorption spectrophotometry. Mercury distribution was examined by processing cerebellar sections for autometallographic (AMG) silver enhancement. Mercury concentration in the offspring cerebral occipital pole ranged between 0.20 and 0.70 microg Hg/g tissue, and in the maternal between 0.80 and 2.58 microg/Hg tissue in animals killed immediately after the end of exposure. AMG revealed that the external granule cell layer of offspring cerebellar tissue contained small amounts of mercury. The molecular layer contained mercury in some of the mercury-exposed monkeys. In the Purkinje cell layer, the Bergmann glial cells together with the Purkinje cells contained mercury. The granule cells and the Golgi cells contained small amounts of mercury. The astrocytes of the medullary layer, identified by immunohistochemistry, contained considerable amounts of mercury, but the cerebellar nuclei accumulated the highest amounts of mercury. No correlation was found between cellular accumulation and maturity of the brain; that is, the cellular localization of mercury did not differ between adult and neonatal brain, except for the amount of visualized mercury. This pattern corresponded well to the mercury concentrations found in the cerebral occipital pole. The differences found in mercury accumulation were instead considered to be dose-related. The results demonstrate that the distribution of mercury in the cerebellum after mercury vapor exposure is similar to the distribution pattern obtained after methyl mercury exposure and that mercury is trapped in the cerebellum over a long period of time.     

Apparent diffusion coefficient on rat brain and nerves intoxicated with methylmercury.

The effects of methylmercury chloride (MMC) on the degenerative changes in rat brain and cranial nerves were studied. Twelve Wistar rats were divided into two equal groups. The rat model of methylmercury intoxication (MMC group) was made by subcutaneously administering 10 mg mercury/g body weight daily for 7 days. Control group rats were infused with the same amount of normal saline during this period. Magnetic resonance imaging (MRI) measurements were performed before and 14 days after the first MMC administration, using a 4.7-T MR system. No significant focal changes were observed on T1- and T2-weighted MR images regarding the internal structures of the brains of the MMC-intoxicated rats, atrophy of the cerebellum, and dilatation of the arachnoid space around the brain stem of MMC-treated rats, but were demonstrated without edematous change. The apparent diffusion coefficients (ADC) of the cortex, caudate-putamen, and trigeminal nerve were not significantly different between the MMC-treated and control rats. However, the ADC parallel to the optic nerves were significantly increased in the MMC group, in contrast to the unchanged ADC perpendicular to the optic nerves. An electron microscopy study revealed a marked decrease of microtubules and moderate decrease of neurofilaments in the axons of myelinated fibers of optic nerves of the MMC-treated rats. We have thus demonstrated a disturbance in the integrity of microtubules and neurofilaments as a toxic action of MMC in the rat nervous system in vivo, particularly in the optic nerves. The use of ADC values calculated by diffusion-weighted MRI is a promising approach for the evaluation of changes in brains and nerves in methylmercury intoxication research.     

氯化甲基汞对大鼠脑神经细胞c-fos表达的影响

目的通过体内与体外实验相结合的方法研究氯化甲基汞(MMC)对脑神经细胞c-fos表达的影响,探讨甲基汞所致脑发育损伤的机制.方法体外实验中,应用免疫细胞化学方法观察MMC对培养神经元c-fos表达的影响.体内实验中,Wistar妊娠大鼠于妊娠7～10d连续灌胃,每日给予MMC4mg/kg.取出生后第1、3、5、7、10和15d仔鼠大脑组织制备常规组织切片.采用免疫组织化学方法检测c-fos表达.结果体外培养的神经元中加入0.3μmol/LMMC持续作用后,神经元中c-Fos阳性细胞率在0.5h开始增多,并随时间的延长而增加.培养神经元接触MMC10min和2、6h组,细胞阳性率分别为(6.97±2.86)%、(66.86±5.32)%、(64.49±3.09)%.体内实验中,对照组和实验组中仔鼠大脑皮层中c-Fos蛋白阳性细胞率随发育时间延长逐渐减少,但实验组均高于相应对照组,实验组第1、3天组c-Fos阳性率分别为(47.01±3.79)%和(46.71±1.96)%,与对照组的(35.86±3.04)%和(33.35±1.06)%相比,差异有非常显著性.结论MMC可诱导脑神经细胞c-fos的过表达,这可能是MMC所致脑发育损伤的机制之一.     

基于MRI的铅暴露老年大鼠脑铁研究

目的探讨长期铅暴露对老年大鼠脑组织中铁含量的影响。方法 SPF级SD雌性和雄性大鼠分别随机分为3组:空白组(0g/L醋酸铅溶液)、低剂量组(0.8g/L醋酸铅溶液)、高剂量组(1.5g/L醋酸铅溶液),按3∶2合笼,空白组所生雄性仔鼠自由饮用去离子水,低剂量组所生雄性仔鼠给予0.3g/L的醋酸铅溶液即0.3g/L染铅组,高剂量组所生雄性仔鼠给予0.9g/L的醋酸铅溶液即0.9g/L染铅组,继续染毒饲养至老年(18月)后,GE MR 3.0T磁共振扫描仪对活体大鼠脑铁行定量分析,ICP-AES测量血液及离体大脑组织中铅和铁元素的含量和经灌注后观察海马神经元超微结构。结果与空白组相比,铅暴露组血铅及脑铅含量增加(P<0.05),0.9g/L染铅组脑铁及皮层、海马、丘脑铁含量均显著增加(P<0.05),且大鼠血、大脑及皮层、海马、丘脑中铁含量与血铅呈高度正相关。电镜结果提示,随着染铅剂量增加,胞质、胞核、线粒体结构和突触结构均遭到不同程度的破坏,出现早期神经元细胞凋亡现象。结论铅暴露引发老年大鼠铁过载,铅诱发的神经退行性病变可能与其引发铁过载有关。