甲基汞对神经递质的影响

甲基汞是环境中重要的污染物之一，其毒作用机制尚不十分清楚，本文仅就其对胆碱类，单胺类，氨基酸类，一氧化氮等神经递质的影响进行了综述。     

甲基汞急性暴露下大鼠脑c-fos mRNA表达

目的探讨即刻早期基因c fos在甲基汞神经毒性分子机制中的作用。方法应用RT PCR方法研究大鼠注射甲基汞急性暴露后,中枢神经系统c fosmRNA表达。结果甲基汞在剂量为0.05mg/(kg·d)暴露60min和剂量为0.5mg/(kg·d)暴露20min就能够显著诱导大鼠脑即刻早期基因c fos表达;c fosmRNA表达量与汞的浓度没有明显正比关系。结论甲基汞能够显著诱导大鼠脑c fosmRNA表达,c fosmRNA表达变化在甲基汞神经毒性分子机制中具有重要作用,即刻早期基因c fos参与了甲基汞对中枢神经系统损害的毒性过程。     

妊娠期甲基汞暴露对大鼠的母体毒性

目的　探讨妊娠期甲基汞暴露对大鼠的母体毒性效应。方法　用不同剂量甲基汞〔0 .0 0、0 .0 1、0 .0 5、2 .0 0mg/ (kg·d)〕于 Wistar大鼠孕 6～ 9天时连续 4天灌胃染毒 ,观察母鼠妊娠期、哺乳期的各种生理、生育过程 ,脑组织形态学和单胺类神经递质 (去甲肾上腺素、多巴胺、5 -羟色胺 )等指标。结果　与对照组相比 ,暴露组母鼠脑组织中单胺类神经递质的含量明显增高 (P<0 .0 1) ,呈现出剂量 -效应关系 (等级相关系数 rs分别为 0 .712 ,0 .90 3,0 .92 6 ) ,P均 <0 .0 1;其余指标未见明显异常。结论　本实验剂量下 ,妊娠期甲基汞暴露对大鼠的母体毒性尽管十分微弱 ,但母体脑组织的化学损伤已经发生。     

006 甲基汞和多氯联苯神经毒性交互作用的研究

甲基汞和多氯联苯是两种最普遍的环境化学污染物，两者有相似的环境代谢途径和生物蓄积方式，并且都具有较强的神经发育毒性，两者的复合暴露已日益受到关注。本文就两者在神经毒性方面的交互作用及其机制的研究作一综述。     

甲基汞和多氯联苯神经毒性交互作用的研究

甲基汞和多氯联苯是两种最普遍的环境化学污染物,两者有相似的环境代谢途径和生物蓄积方式,并且都具有较强的神经发育毒性,两者的复合暴露已日益受到关注。本文就两者在神经毒性方面的交互作用及其机制的研究作一综述。     

甲基汞对大鼠脑皮质谷氨酰胺合成酶的影响

取Wistar大鼠36只,按体重随机分成3组,每组12只。第1～3组分别为对照组、低甲基汞(MeHg)组和高MeHg组。每日染毒1次,连续4周。每周测量大鼠体重,用冷原子吸收法测量大鼠脑皮质内Hg含量,比色法测定GS活力、谷氨酸(Glu)和谷氨酰胺(Gln)含量,用Real-time PCR和Western blotting检测GS mRNA表达和蛋白水平。与对照组比较,在低MeHg组中Hg含量明显升高,GS活力、GS蛋白水平均显著下降;在高MeHg组中,大鼠体重、GS活力、Gln含量、GSmRNA表达和蛋白水平均明显下降,Hg和Glu含量均显著增高。提示甲基汞能导致大鼠脑谷氨酰胺合成酶表达和功能异常,谷氨酰胺合成酶在甲基汞诱导的神经毒性过程中起重要作用。 更多还原     

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。     

甲基汞亚致畸量对小鼠脑影响的形态学观察

我们利用电镜及电子计算机数字化图像系统等方法，对在子宫内接触甲基汞亚致畸量的小鼠脑变化进行了短期及长期研究，并把两个时期的变化做了对比研究。结果表明，短期组和长期组小鼠脑细胞均有变性、脱失；长期组病变重于短期组。显示了甲基汞亚致畸量对小鼠脑的毒性作用具有长期性；由于染甲基汞仔鼠无明显外观及行为异常，因而具有隐匿性。     

胚胎期低剂量甲基汞暴露大鼠的操作行为测试

目的 建立起电脑控制的大鼠操作行为测试系统,探讨胚胎期低剂量甲基汞暴露对大鼠学习记忆能力的影响。方法 以氯化甲基汞0,0．01,0．05,2．00mg(kg.d)于Wistar孕鼠妊娠6－9d进行灌胃处理。仔鼠10周龄时,于4个实验组中各随机抽取8只,采用自动化操作行为测试系统于夜间进行15h（16：00－7：00）的行为测试,测试程序为高／低频度差别强化率,前者要求大鼠多次重复压杆,后者则需要在得到强化物（45mg小食丸）后等待一段时间再压杆。实验采用双盲法。结果 3个剂量组大鼠的学习成绩均比对照组降低（P＜0．05或P＜0．01）,高频度差别强化率存在剂量－反应关系（rs＝－0．7273,P＜0．01）。结论 胚胎期低剂量甲基汞暴露可影响大鼠神经系统的生长发育,使其学习记忆能力受到损伤。     

Organic and Inorganic Mercury in Neonatal Rat Brain after Prenatal Exposure to Methylmercury and Mercury Vapor

Background

Many populations are exposed to multiple species of mercury (Hg), predominantly organic Hg as methylmercury (MeHg) from fish, and inorganic Hg as Hg vapor from dental amalgams. Most of our knowledge of the neurotoxicity of Hg is based on research devoted to studying only one form at a time, mostly MeHg.

Objectives

In this study we investigated the effects of prenatal exposure to MeHg and Hg vapor on Hg concentrations in the brain of neonatal rats.

Methods

Female Long-Evans hooded rats were exposed to MeHg (0, 3, 6, or 9 ppm as drinking solution), Hg vapor (0, 300, or 1,000 μg/m³ for 2 hr/day), or the combination of both, from 30 days before breeding through gestational day 18. On postnatal day 4, whole brains were taken from one male and one female from each of four litters in each treatment group to assess organic and inorganic Hg in the brain by cold vapor atomic absorption spectrometry.

Results

Statistical analysis using linear mixed effects models showed that MeHg dose was the primary determinant of both organic and inorganic brain Hg levels. For both outcomes, we also found significant interactions between MeHg and Hg vapor exposure. These interactions were driven by the fact that among animals not exposed to MeHg, animals exposed to Hg vapor had significantly greater organic and inorganic brain Hg levels than did unexposed animals.

Conclusion

This interaction, heretofore not reported, suggests that coexposure to MeHg and Hg vapor at levels relevant to human exposure might elevate neurotoxic risks.     

不同水平饲料锌与热暴露对大鼠某些脑区锌、铜、铁含量的影响

选用４８只ＳＤ雄性大鼠随机等分３组，即Ａ组、Ｂ组和Ｃ组。再从每组中分出８只用于高温暴露，另８只用于室温对照，在ＡＩＮ－９３Ｍ饲料配方基础上，以碳酸锌为锌源，配制成Ａ、Ｂ、Ｃ组锌饲料。每千克饲料锌含量测定值：Ａ组为９２．２ｍｇ，Ｂ组４５．６１ｍｇ，Ｃ组２１．７０ｍｇ。根据动物分组，饲以各组大鼠相应水平锌饲料１４天后，将用于高温暴露的大鼠置于高温室（Ｔｄｂ４０℃，Ｔｗｂ３０．８℃）连续暴露３小时。用原子吸收分光光度计火焰法测定大鼠海马、大脑皮层和小脑Ｚｎ、Ｃｕ、Ｆｅ含量。实验结果发现：①高温暴露可使海马铜含量显著增加：②高温暴露后，海马铜含量比小脑和大脑皮层铜含量高，而在室温对照大鼠，小脑铜含量却比大脑皮层和海马铜含量高。③摄入不同水平饲料锌主要影响小脑铜的含量，对铁的影响较小。④中、高水平膳食锌摄入可使热应激大鼠小脑铜含量降低     

Fate and Transport of Mercury in Environmental Media and Human Exposure

Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species, mainly elemental (Hg⁰) and divalent (Hg²⁺) mercury depending on its oxidation states in air and water. Mercury emitted to the atmosphere can be deposited into aqueous environments by wet and dry depositions, and some can be re-emitted into the atmosphere. The deposited mercury species, mainly Hg²⁺, can react with various organic compounds in water and sediment by biotic reactions mediated by sulfur-reducing bacteria, and abiotic reactions mediated by sunlight photolysis, resulting in conversion into organic mercury such as methylmercury (MeHg). MeHg can be bioaccumulated through the food web in the ecosystem, finally exposing humans who consume fish. For a better understanding of how humans are exposed to mercury in the environment, this review paper summarizes the mechanisms of emission, fate and transport, speciation chemistry, bioaccumulation, levels of contamination in environmental media, and finally exposure assessment of humans.     

急性冷暴露对大鼠体内锌铜铁代谢的影响

观察了急性冷暴过程中大鼠体内Ｚｎ、Ｃｕ、Ｆｅ水平及有关酶的变化情况。结果表明，大鼠冷暴后血清Ｚｎ明显升高（Ｐ＜０．０５），而肝及骨骼肌中的Ｚｎ则明显降低（Ｐ＜０．０５）。血清和肝Ｃｕ、Ｆｅ，肌Ｆｅ有下降趋势，肌Ｃｕ下降更明显（Ｐ＜０．０５）。大鼠冷暴后，肝线粒体Ｈ＋转运ＡＴＰ酶活性及血清铜蓝蛋白均明显低于室温对照组。结果提示，急性冷暴可以导致机体Ｚｎ等微量元素的重新分布，同时对某些微量元素的需求增加。     

铅对大鼠海马及其突触体膜脂质流动性的影响

目的　通过检测染铅大鼠海马铅含量及其突触体膜脂质流动性变化 ,探讨铅对学习记忆功能影响的机制。方法　Wistar大鼠饮用含 2 g/L 的醋酸铅 (PbAc)的水溶液 ,染铅 3个月后 ,分别采用原子吸收法和荧光偏振分光光度法测定血清、海马中铅含量和海马突触体膜脂质流动性。结果　与对照组比较 ,染铅组大鼠血清和海马中铅含量明显升高 (P <0 0 5 ) ,其海马突触体膜脂质流动性降低 (P <0 0 5 )。结论　铅对大鼠海马突触体膜脂质流动性的影响可能与铅干扰脑的学习记忆功能有关     

Work-Time Exposure and Acute Injuries in Inshore Lobstermen of the Northeast United States

The objective of this study was to inform efforts to reduce risk for musculoskeletal disorders among commercial lobstermen by characterizing and quantifying injuries that occur to people while harvesting lobsters commercially in the Northeast United States. This study aimed to estimate a denominator of exposure to lobstering in full-time equivalents (FTE), to estimate a fatality rate, and to calculate incidence rates for acute injuries within the sample population. Captains were randomly selected from those licensed to fish in Maine and Massachusetts. Data on work exposure and injuries with rapid onset that occurred on the boat (“acute injuries”) were collected using a survey, which was administered quarterly via phone or face-to-face interview with the captain. The quarterly survey assessed the number of weeks worked during the quarter, average crew size, number of trips per week, and average trip length in hours. In addition, this survey captured relevant information (body segment affected, type of injury, and whether treatment was received) on all acute injuries occurring during the quarter. FTE were estimated using fishermen days and fishermen hours. The annual FTE estimated using days was 2,557 and using hours was 2,855. As expected, the summer months (3rd quarter) had the highest FTE and the winter (1st quarter) the lowest FTE. Fall (4th quarter) and spring (2nd quarter) ranked second and third, respectively. The incidence rates for all injuries (49.7/100 FTE) and injuries requiring treatment (15.0/100 FTE) were much higher than those reported in other studies of fishing that used Coast Guard data.     

急性心肌梗死患者血清中铁铜锰硒钴含量研究

目的对135例急性心肌梗死患者血清中的铁、铜、锰、硒、钴的含量测定,并与对照组比较.方法采用等离子体发射光谱仪检测.结果血清铁、铜、锰和钴的含量显著升高,二者差异有高度显著性P＜0.01;而血清硒的含量明显降低,二者差异有高度显著性P＜0.01.结论临床医生在治疗中注意微元素的变化.     

Environmental Exposure and Fingernail Analysis of Arsenic and Mercury in Children and Adults in a Nicaraguan Gold Mining Community

Gold mining can release contaminants, including mercury, into the environment, and may increase exposure to naturally occurring elements such as arsenic. The authors investigated environmental and human tissue concentrations of arsenic and mercury in the gold mining town of Siuna, Nicaragua. The study involved 49 randomly selected households in Siuna, from whom a questionnaire along with environmental and fingernail samples were collected. Environmental samples indicated that mercury concentrations in drinking water, although generally low, were higher near the mine site. Arsenic concentrations were elevated in water and soil samples, but their distribution was unrelated to the mining site. Mercury concentrations in fingernail samples were correlated with residential proximity to the mine, drinking water concentrations, occupation, and, among children, with soil concentrations. Fingernail arsenic concentrations correlated with drinking water concentrations among adults who consumed higher levels, and with soil concentrations among children. Fingernail analysis helped to identify differential exposure pathways in children and adults. Mercury and arsenic uptake via soil exposure in children warrants further consideration.     

Prenatal exposure to mercury and neurobehavioral development of neonates in Zhoushan City, China

Exposure to hazardous Hg can adversely affect children's neurodevelopment. However, few data are available on either Hg levels in neonates and their mothers or the impact of prenatal exposure to Hg on neonates' neurobehavioral development in the Chinese population. Therefore, this study examined Hg levels in neonates and their mothers and the relationship between prenatal exposure to Hg and neonates' neurobehavioral development in Zhoushan City, Zhejiang Province, China. Between August and October 2004, 417 women who delivered their babies at Zhoushan Women's and Children's Health Hospital, an island city in east China were invited to take part in this study. A total of 408 complete questionnaires, 405 maternal hair samples, and 406 umbilical cord samples were collected. Neonatal behavioral neurological assessments (NBNA) were conducted for 384 neonates. The geometric mean (GM) of Hg level in cord blood was 5.58 microg/L (interquartile range: 3.96-7.82 microg/L), and the GM of maternal hair Hg level was 1246.56 microg/kg (interquartile range: 927.34-1684.67 microg/kg), a level much lower than other reported fish-eating populations, indicating Hg exposure in Zhoushan city is generally below those considered hazardous. However, according to the reference dose of Hg levels (RfD 5.8 microg/L) derived by EPA, 69.9% of newborns had levels at or above the RfD, an estimated level assumed to be without appreciable harm. There was a strong correlation between maternal hair and cord blood Hg levels (r = 0.82, P < 0.01). Frequency of fish consumption was associated with hair Hg (r = 0.48, P < 0.01) and cord blood Hg levels (r = 0.54, P < 0.01). Increased prenatal Hg exposure was associated with decreased behavioral ability for males (OR = 1.235, 95%CI of OR = 1.078-1.414, P < 0.001), but not for females. Our results provide some support for the hypothesis that there is neurodevelopmental risk for males from prenatal MeHg exposure resulting from fish consumption. But the findings of this study may be due to chance, and long-term follow-up research is needed to evaluate cumulative effects of exposure to mercury.     

急性心肌梗死患者血清中铬钴镍钒钼含量研究

目的对135例急性心肌梗死患者血清中的铬、钴、镍、钒、钼的含量检测并与对照组比较.方法采用等离子体发光谱仪检测.结果血清钴的含量明显增加,二者有非常显著性差异(P＜0.01);血清铬、镍、钒、钼含量明显降低,二者有非常显著性差异(P＜0.01).