LASER MICROPROBE ANALYSIS OF NEURONAL MERCURY

肌萎缩侧索硬化症（ALS）的病因， 以选择性运动功能丧失为特征的退行性疾病 神经元未知 PI的既往研究表明， 与对照组相比，ALS组织中的汞大量增加， 支持有毒金属可能是致病的假设 在ALS中。 然而，这一假设仍然是相当投机的。 因为有毒金属的细胞分布还没有被 调查以确定汞是否实际上是有选择地 富含运动神经元 在拟议的研究中，激光激活微探针质量分析 （LAMMA）将用于测量汞的丰度， 运动神经元中的其他元素。 LAMMA是一项新技术， 能够探测单个细胞的特定区域， 确定完整的元素组成与空间 分辨率为1 - 2微米。 ALS患者的大脑和脊髓， 将获得年龄匹配的对照;已知的区域 病理上参与ALS（运动皮质，腹侧脊髓） 将使用LAMMA进行分析。 在对照组中， 将在运动神经元的细胞核和细胞质中进行测定， 与其他细胞进行比较，以验证汞是 运动神经元选择性地积累。 在ALS中，特别是 注意力将被引导到运动神经元的各个阶段， 包括近端轴突球体的分析， 确定神经元汞积累是否提前，或者是 神经元死亡的后果。 汞含量将在 Onufrowicz核（支配膀胱的运动神经元; 在ALS中幸免），以确定这些细胞是否与易感细胞不同， 脊髓中的运动神经元在它们的毒性负荷方面 金属. 将在ALS和对照组之间进行比较， 区域和细胞类型的基础上建立，如果 ALS中汞的相对丰度增加。 散装 来自相同患者的组织样本将使用 中子活化直接与LAMMA数据先前 PI和其他研究。 虽然工作的主要重点 是汞，LAMMA和中子活化都提供了 同时分析其他人假设的多种元素， 参与ALS的发病机制（例如：铅，铝， 硒）。 这项研究的结果将提供第一个测量， 散发性ALS病例运动神经元中的汞含量。 这些分析将提供对假设的直接检验， 脊髓运动神经元中汞的积累标志着细胞 易发生ALS型变性。

The etiology of amyotrophic lateral sclerosis (ALS), a degenerative disorder characterized by selective death of motor neurons, is unknown. Prior studies by the PI have demonstrated large increases in mercury in ALS tissues compared to controls, supporting the hypothesis that toxic metals may be pathogenetic in ALS. However the hypothesis remains quite speculative because the cellular distribution of toxic metals has not been investigated to determine if mercury is, in fact, selectively enriched in motor neurons. In the proposed study, Laser Activated Microprobe Mass Analysis (LAMMA) will be used to measure the abundances of mercury and other elements in motor neurons. LAMMA is a new technique, capable of probing specific regions of individual cells and determining the complete elemental composition with a spatial resolution of 1-2 microns. The brain and spinal cord of ALS and age-matched controls will be obtained; regions known to be pathologically involved in ALS (motor cortex, ventral spinal cord) will be analyzed using LAMMA. In controls, mercury abundance will be assayed in the nucleus and cytoplasm of motor neurons and compared to other cells to test the hypothesis that mercury is selectively accumulated by motor neurons. In ALS, particular attention will be directed to motor neurons in various stages of degeneration including analysis of proximal axonal spheroids to determine if neuronal mercury accumulation preceeds, or is a consequence of, neuronal death. Mercury will be assayed in the Onufrowicz nucleus (motor neurons innervating the bladder; spared in ALS) to determine if these cells differ from susceptible motor neurons in the cord with regard to their burden of toxic metals. Comparisons will be made between ALS and controls on a region-by-region and cell type-by-cell type basis to establish if the relative abundance of mercury is increased in ALS. Bulk tissue samples from the same patients will be analyzed using neutron activation to relate the LAMMA data directly to previous studies by the PI and others. Although the primary focus of work is mercury, both LAMMA and neutron activation provide simultaneous analysis of multiple elements postulated by others to be involved in the pathogenesis of ALS (eg: lead, aluminum, selenium). The results of this study will provide the first measurement of mercury abundances in motor neurons of sporadic cases of ALS. These analyses will provide a direct test of the hypothesis that mercury accumulation in spinal motor neurons marks the cell as susceptible for ALS-type degeneration to occur.