Sheep scrapieの光顕および電顕的観察

LIGHT AND ELECTRON MICROSCOPIC OBSERVATIONS OF SHEEP SCRAPIE

　抄録　Sheep scrapieを形態学的に検索しmouse scrapie^11）との間に空胞形成過程に差があるかどうか検討した。検索材料は，臨床および疫学的にscrapieと診断されたサフォーク種のヒツジの雌2例。光顕的に海綿状変化が，視神経，大脳灰白質および同白質，橋，小脳白質，中脳と延髄および脊髄の灰白質と白質に認められた。胞体内に空胞を有する神経細胞は主として橋と延髄で観察された。電顕的に，神経細胞の胞体における空胞は，小胞体やゴルジ装置が連続的に拡張することによる細胞質の変性と脱落によって形成されることが示唆された。これらの変化は，mouse scrapieにおける神経細胞の胞体の空胞が主として細胞質の腫脹に伴う細胞膜の損傷によって形成されるのとは異なっていた。しかし，neuropilにおける空胞はmousescrapie同様に細胞質の腫脹に伴う細胞膜の損傷によって形成されていた。sheep scrapieの白質病変はmouse scrapie同様に髄鞘の分離と空胞化および軸索周囲腔の拡大からなり，scrapie agentによる一次性の変化と考えられた。sheep scrapieとmouse scrapieにおいて，神経細胞の胞体の空胞形成機序に差が認められたことは，scrapieにおける病変形成に宿主の遺伝的要因が関与している可能性を示唆していた。

Two Suffolk sheep diagnosed as scrapie clini-cally and epidemiologically were investigated light and electron microscopically. They were female and four years four months of age.

Spongiform lesions were found in the gray and white matter of midbrain, pons, medulla oblon-gata, spinal cord and the cerebellar white matter as well as the cerebral gray and white matter, Ultrastructurally, the spongiform lesions were shown to be caused by vacuolation in neuronal perikarya, vacuolation and/or swelling of neuropil, dilatation of the periaxonal space, and splitting of the myelin sheath followed by the intramyeli-nic vacuolation. Vacuole in neuronal perikaryon was associated with the enlarged endoplasmic reticulum. Adjacent to the vacuole, enlargement of the rough endoplasmic reticulum and cisterns of Golgi apparatus was observed. The cytoplasmic processes found in the intraneuronal vacuoles were formed by the separation of the cytoplasm caused by the continuous dilatation of the endoplasmic reticulum and cisterns of Golgi apparatus. This indicated that the degeneration of the neuronal perikaryon due to such separation contributed to the formation of the intraneuronal vacuole. Vacuo-lation and swelling with disappearance of the organelles were also found in astro- and oligo-dendroglial perikarya. Splitting of myelin sheath and the intramyelinic vacuolation were regarded as primary changes. The latter was supported by the degeneration of oligodendroglias found in this study.