大鼠长期摄入贫铀对睾酮合成及StAR、P450scc基因表达的影响

目的 研究长期摄入贫铀(DU)对雄性大鼠生殖功能改变的机制。方法 大鼠长期摄入贫铀,剂量分别为4和40 mgDU·kg^－1·d^－1。在 F₀代20个月,F₁代15个月时,测定其血中性激素含量,并用反转录多聚酶链式反应(RT-PCR)研究在睾酮(T)合成中起限速作用的类固醇合成急性调节蛋白(StAR)和细胞色素P450胆固醇侧链裂解酶(P450scc)基因表达的影响,同时设健康对照组。结果 食入组血清T的含量均低于健康对照组,最低为51.73 U/L,但黄体生成素(LH)、卵泡刺激素(FSH)含量均高于健康对照组。StAR mRNA的表达,除F₁低剂量组(StAR/β-actin半定量值为1.35)上调外,其余组的表达均较健康对照组(1.035)下调;P450scc mRNA的表达在F₀代低、高剂量组较健康对照组(P450scc/β-actin比值为0.313)下调,P450scc/β-actin降至0.21;在F₁代低、高剂量组较健康对照组上调,P450scc/β-actin升至0.623。结论 长期摄入DU,可通过抑制StAR、P450scc mRNA的表达从而干扰T合成途径来抑制雄性的生殖作用。     

大鼠吸入贫铀气溶胶后体内铀的分布

目的 建立贫铀(depleted uranium, DU)气溶胶吸入动物模型,观察气溶胶吸入后DU在重要组织器官的蓄积情况。方法 采用大鼠吸入DU气溶胶的实验模型,分别在吸入后的30、90、180、270、360和540 d,采用激光时间分辨发光分析法测定肺脏、肾脏、股骨、肝脏、心脏、脑、脾脏和胸腺等的铀含量。结果 DU气溶胶吸入后高低剂量组大鼠肺铀含量分别为(499 833.3±14 214.8)ng/g及(25 424.0±6193.4)ng/g,明显高于未吸入组(28.8±13.9)ng/g (P<0.05)。吸入30 d后,肺、股骨及肾中的铀含量明显升高,随时间逐渐下降;吸入60d起,肝脏、大脑、心脏、胸腺、脾脏中铀含量高于对照组,铀含量呈先升高后降低的两相分布。铀含量以肺脏、股骨、大脑、胸腺中较高,肾次之,肝、心脏、脾较少。结论 DU气溶胶吸入后,铀可在肺、肾、股骨、肝脏、大脑、心脏、胸腺、脾脏等分布,其中肺、股骨、大脑、胸腺及肾脏中高浓度铀的存在提示上述器官是DU损伤的潜在靶器官。     

Laser Heating Study of the High-Temperature Interactions in Nanograined Uranium Carbides

Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect of grain size on the melting and solid–solid transitions of nanograined UC_2−y. We laser-heated 4 nm–10 nm grain size samples with UC_2−y as the main phase (but containing graphite and UO₂ as impurities) under inert gas to temperatures above 3000 K, and their behavior was studied by thermal radiance spectroscopy. The UC_2−y solidification point (2713(30) K) and α-UC₂ to β-UC₂ solid–solid transition temperature (2038(10) K) were observed to remain unchanged when compared to bulk crystalline materials with micrometer grain sizes. After melting, the composite grain size persisted at the nanoscale, from around 10 nm to 20 nm, pointing to an effective role of carbon in preventing the rapid diffusion of uranium and grain growth.     

尿铀监测在内照射个人剂量估算中的应用

目的 探讨尿铀监测估算内照射个人剂量的适用条件,为核工业职业卫生管理和核燃料单位开展尿铀监测提供参考。方法 使用模拟计算的方法,分别推导了急性和慢性摄入铀化合物,致个人有效剂量分别为1 mSv/次和1 mSv/年时的尿铀水平,并以某厂无职业接触史职工上岗前尿铀监测结果为例,分析尿铀监测用于个人剂量估算的适用条件。结果 对于急性摄入的特殊监测,使用液体荧光法尿铀监测可以满足F类铀化合物、M类低浓铀和S类天然铀的探测限要求;对于常规监测,在监测周期较短时,仅F类低浓铀和M类天然铀可以满足探测限的要求,S类铀化合物不适宜将尿铀作为常规监测。结论 尿铀监测用于内照射个人剂量监测的评价或结果解释时,需考虑尿中铀本底含量的影响及监测方法的探测限要求。     

牛磺酸锌对贫铀染毒大鼠体重及学习记忆的影响

目的探讨牛磺酸锌对贫铀致神经系统损伤的保护作用。方法给Wistar大鼠气管灌注低、中、高剂量(1,3,5 mg)的贫铀颗粒,另组灌注高剂量(5 mg)贫铀颗粒的同时,喂饲含牛磺酸锌的饲料(含锌元素200 mg/kg)。观察单纯铀染毒大鼠、铀染毒同时食用含牛磺酸锌饲料大鼠及正常对照组大鼠之间体重增量和“Y”迷宫实验学会次数的差别。结果各实验组之间大鼠体重增量比较,差异无显著性(P>0.05)。低、中、高剂量组及高剂量铀染毒 牛磺酸锌组的“Y”迷宫实验学会次数较对照组明显增多,差异有显著性(P<0.05),高剂量铀 牛磺酸锌组与高剂量铀染毒组比较,“Y”迷宫实验学会次数则明显减少,差异有显著性(P<0.05)。结论贫铀染毒能使大鼠“Y”迷宫实验学会次数增加,但对大鼠体重的影响不明显。牛磺酸锌可降低染铀大鼠的“Y”迷宫实验学会次数,说明其对贫铀致神经系统损伤有保护作用。     

铀矿勘探开采危害指数分析

本文报道了我国铀矿勘探开采的危害指数调查分析。共调查了核工业２队３矿１７５５９人（地质占１５５％，矿山占８４５％），５１７５５２５人年。结果显示，五单位１９５５～１９９０年危害指数为４１６年／１０００人年，低于山西省煤炭系统（７１５年／１０００人年），高于冶金系统（１５１年／１０００人年）及核工业平均值（１５７年／１０００人年），主要与铀矿矽肺发生与死亡人数增多有关。本文还对危害指数计算中的不确定因素进行了分析。     

浓缩铀诱发细胞凋亡的形态及基因调控

目的　研究浓缩铀诱发人白血病HL 6 0细胞凋亡的电镜形态特征 ,以及对相关基因bcl 2和bax的调控作用。方法　探讨受浓缩铀内照射不同时间 ,诱发HL 6 0细胞凋亡的电镜形态 ;运用免疫组织化学技术探讨浓缩铀对HL 6 0细胞bcl 2和bax蛋白的表达 ,运用RNA分子杂交技术探讨浓缩铀对HL 6 0细胞bcl 2mRNA的转录水平表达的影响。结果　人白血病HL 6 0细胞在浓缩铀辐照作用下 ,可呈现核断裂和核染质边聚。对照的HL 6 0细胞中bcl 2蛋白呈高度表达 ,为 (88± 7) % ,而受浓缩铀辐照下 ,可下调至(6 1± 5 ) %。bax在对照细胞中表达很低 ,在浓缩铀作用下 ,未见明显改变。经浓缩铀辐照后 ,可使HL 6 0细胞中的bcl 2mRNA表达呈明显下调。结论　浓缩铀内照射可诱发人白血病HL 6 0细胞凋亡发生 ,且其诱发HL 6 0细胞的凋亡作用与其下调凋亡相关基因bcl 2的表达相关联     

小剂量8102对大鼠急性铀中毒的促排效果

研究８１０２不同剂量和连续给药对大鼠急性铀中毒的促排效果。大鼠中毒硝酸铀酰（５００μｇ／鼠）后给予不同剂量８１０２（０～１００ｍｇ／ｋｇ），测定尿铀排出量及肾铀蓄积量。结果：大鼠肌肉注射８１０２及灌胃给予８１０２促排轴的最小有效剂量分别为５ｍｇ／ｋｇ和２０ｍｇ／ｋｇ；８１０２连续给药与一次性给药相比未见尿铀排出量的显著增高和肾铀蓄积量的显著降低。８１０２是一个很有希望的铀促排螯合剂，值得进一步深入研究。     

Uranium mining in relation to toxicological impacts on inland waters

Protection of tropical rivers from metal pollution requires that mining wastewaters be biologically tested for aquatic toxicity before release from the site into natural ecosystems occurs, and that a safe dilution which incorporates a minimum 10-fold safety factor applied to the lowest NOEC threshold value be utilized. Application of these test methods to wastewaters from an operating uranium mine has shown that pre-release toxicity testing provides accurate information on the toxicity of metal-containing wastewaters with a high degree of confidence. Field validation of the laboratory results was obtained when wastewaters which were field diluted through a release into a billabong gave similar results to laboratory-diluted wastewaters. No one species is always the most sensitive to exposure to complex wastewaters. Changes with time in wastewater chemistry, toxicity, and in the physiological capacity of specific organisms to survive in a contaminated environment (tolerance), can result in different species having varying sensitivities over time to exposure to complex wastewaters collected from the same location. As a result of the remote likelihood of finding the most sensitive species, it is necessary to test the toxicity of complex wastewaters to a battery of organisms, representing different trophic levels of the ecosystem, under physical conditions representative of the specific environment needing protection. Use of a natural billabong as a biological filter for releasing mine wastewaters did not result in toxicity mitigation and prevented controlled dilution from occurring during periods of high creek flow.     

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Delayed Earth system recovery following the end-Permian mass extinction is often attributed to severe ocean anoxia. However, the extent and duration of Early Triassic anoxia remains poorly constrained. Here we use paired records of uranium concentrations ([U]) and ²³⁸U/²³⁵U isotopic compositions (δ²³⁸U) of Upper Permian−Upper Triassic marine limestones from China and Turkey to quantify variations in global seafloor redox conditions. We observe abrupt decreases in [U] and δ²³⁸U across the end-Permian extinction horizon, from ∼3 ppm and −0.15‰ to ∼0.3 ppm and −0.77‰, followed by a gradual return to preextinction values over the subsequent 5 million years. These trends imply a factor of 100 increase in the extent of seafloor anoxia and suggest the presence of a shallow oxygen minimum zone (OMZ) that inhibited the recovery of benthic animal diversity and marine ecosystem function. We hypothesize that in the Early Triassic oceans—characterized by prolonged shallow anoxia that may have impinged onto continental shelves—global biogeochemical cycles and marine ecosystem structure became more sensitive to variation in the position of the OMZ. Under this hypothesis, the Middle Triassic decline in bottom water anoxia, stabilization of biogeochemical cycles, and diversification of marine animals together reflect the development of a deeper and less extensive OMZ, which regulated Earth system recovery following the end-Permian catastrophe.The end-Permian mass extinction—the most severe biotic crisis in the history of animal life—was followed by 5 million years of reduced biodiversity (1, 2), limited ecosystem complexity (3), and large perturbations in global biogeochemical cycling (4, 5). Ocean anoxia has long been invoked both as a cause of the extinction (6–8) and as a barrier to rediversification (9). Numerous lines of evidence demonstrate widespread anoxic conditions around the time of the end-Permian mass extinction (e.g., refs. 6 and 10–12). In contrast, the prevalence of anoxia during the 5- to 10-million-year recovery interval remains poorly constrained (13, 14).Reconstructing paleoredox conditions is challenging because some indicators of anoxia characterize only the local conditions of the overlying water column, whereas other indicators may be influenced by confounding factors, such as weathering rates on land. Here, we use paired measurements of [U] and δ²³⁸U in marine carbonate rocks to differentiate changes in weathering of U from variations in global marine redox conditions. Microbially mediated reduction of U(VI) to U(IV) under anoxic conditions at the sediment−water interface results in a substantial decrease in uranium solubility and a measureable change in ²³⁸U/²³⁵U (15–18). Because ²³⁸U is preferentially reduced and immobilized relative to ²³⁵U, the δ²³⁸U value of seawater U(VI) decreases as the areal extent of bottom water anoxia increases (Fig. S1). Consequently, a global increase in the extent of anoxic bottom waters will cause simultaneous decreases in [U] and δ²³⁸U of carbonate sediments. A previous study of δ²³⁸U variations at one stratigraphic section through the immediate extinction interval (∼40,000 y) (11) suggested a rapid onset of anoxia coincident with the loss of marine diversity. However, with only a single site, it is unclear if the signal is globally representative; moreover, the lack of data for all but the lowest biostratigraphic zone of the Triassic leaves the pattern and timing of environmental amelioration during the recovery interval unconstrained.Open in a separate windowFig. S1.Study materials and methods. (A) Paleogeographic map showing locations of Turkey and South China, modified from ref. 19. (B) Schematic cross section and studied stratigraphic sections of the GBG, modified after ref. 20. (C) Inputs and outputs of the modern uranium cycle.To develop a quantitative, global reconstruction of seawater redox conditions for the entire 15-million-year interval of mass extinction and subsequent Earth system recovery, we measured 58 Upper Permian (Changhsingian) through Upper Triassic (Carnian) limestone samples from three stratigraphic sections (Dajiang, Dawen, and Guandao) arrayed along a depth transect on the Great Bank of Guizhou (GBG), an isolated carbonate platform in the Nanpanjiang Basin of south China (eastern Tethys). To test the extent to which variations in [U] and δ²³⁸U within the GBG reflect global uranium cycling, we also analyzed 28 limestone samples from the Taşkent section, Aladag Nappe, Turkey, located in the western Tethys (Fig. S1). We focused our measurements on samples deposited in shallow marine environments (<100 m water depth, i.e., Dajiang, Dawen, and Taşkent) likely to have remained oxygenated. Variations in [U] and δ²³⁸U in these samples should reflect changes in global, rather than local, redox conditions.