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臭化メチルはヒトに中枢および末梢神経障害を惹起する。現在までの臭化メチル中毒動物の神経病理学的な研究にもかかわらず,臭化メチル中毒による多彩なヒトの神経障害は実験動物で十分に再現されていない。本研究では,1日6時間,週3日,3-8週間にわたり,500または290ppmの臭化メチルの繰り返し曝露を受けたラットの神経系病変を組織形態学的に系統的に検索し,未だ実験動物で再現されていない病変を明らかにする...ことを目的とした。その結果,10 -18日間の500ppmの臭化メチル曝露によってのみ,ヒトの脊髄後索病変に対応すると判断される頚髄薄束有髄線維の軸索変性およびヒトの大脳病変に対応すると判断される,1)尾状核-被殻の壊死病変,2)尾状核-被殻,視床および帯状皮質の神経細胞の萎縮およびニューロピルの染色性の低下が認められた。この実験により初めて明らかになった脊髄後索病変の作成は,繰り返し曝露が可能でかつ500ppm以上の濃度の臭化メチルの曝露によって達成されると推定される。
Methyl bromide exposure produces disorders of the central and peripheral nervous system. In the literature, there are many neuropathologic studies on the nervous system, especially on the central nervous system, of experimental animals intoxicated with methyl bromide presented. However, in our opinion, a variety of lesions of the nervous system described in the human methyl bromide intoxication have not been well reproduced in the experimental animals. In this study, male Wistar rats were subjected to a 6-hour exposure a day to methyl bromide at a concentration of 500 or 290 ppm 3 days a week for 3 to 8 weeks. The systematic neuropathologic studies of their central and peripheral nervous systems were carried out to reproduce the nervous system lesions in the human methyl bromide intoxication hitherto not produced in the experimental animals. Among the rats exposed to methyl bromide at a concentration of 500 ppm for 10 to 18 days, the axonal degeneration of myelinated fibers at the cervical level of the fasciculus gracilis, which probably corresponds to the degeneration of the spinal posterior column in humans, and the necrosis of the caudate-putamen and atrophy of neurons and pallor of the neuropile in caudate-putamen, thalamus and cingulate cortex, which probably correspond to the degenerative findings of the cerebrum in humans, were found. The rats exposed to methyl bromide at a concentration of 290 ppm for 8 weeks (24 days) did not show any noticeable abnormalities histologically. The results above suggest that the spinal cord lesion described for the first time is produced by the repeated exposure of rats to methyl bromide at a higher concentration than 500 ppm.続きを見る
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