中枢二次変性の電子顕微鏡的研究—軸索および髄鞘の変化

Electron Microscopy of Secondary Degeneration in the Central Nervous System: Structural Changes of Axon and Myelin Sheath

　成熟ラッテ視神経を眼球接合部にて3秒間挫滅し，挫滅部位より7〜10cm距つた頭蓋内視神経を，挫滅後経時的に観察し，反対側の視神経を対称とした。また，視神経を挫滅するには，外眼筋の眼球附着部を切離されなければならないが，挫滅直前までの操作を挫滅時とまつたく同様に行ない外眼筋切離の操作によつて視神経の形態学的変化をきたさないことを電子顕微鏡学的に確認した。

　中枢神経二次変性の観察には，実験条件を可及的に一定にすることがもつとも理想的であるが，成熟ラッテの視神経は次の4点でもつとも適した材料と考えられる。

Examination was made of the rat optic nerve 7to 10 millimeter distant from the crush injury point.Generally the axons were first involved, but someof them were spared even 7 days after the injury.The earliest change in axon was evident already24 hours after the injury, and consisted of a localand transient accumulation of mitochondria, vesicles, dense particles, dense bodies, and membranous axoplasmic bodies, with individual neurofilamentsmaintaining normal structure with a cylindricaldensity. Potential genesis and significance werediscussed on the accomulation of these axoplasmicorganelles.

The early alternation of myelin sheath, whichappeared 5 days after the crush, was shown in asplitting of myelin lamellae. The myelin lamellaewere split at the intraperiod dense line, showingtwo morphological features. One was a simplesplitting of myelin lamellae, which was usuallyoccurred after the complete disintegration of axon. Another was possibly instructive of the demyelinationprocess from the biological standpoint; a closestructural association with ectopically appearingmyelin-forming glial cell. In other words the splitmajor dense line bordered the cytoplasmic surfaceof the myelin-forming glial cell. The myelinlamellae maintained the normal structure withregular layering except for the splitting untilengulfed by phagocytes. One or two layers ofelongated myelin lamellae were occasionally presentin a close contiguity to round-shaped glial cell,even in gliosis. In the phagocytes, on the contrary,the periodicity and thickness of the constituentmembranous layers of myelin lamellae were changedin an apparently complicated manner. However,there were certain regularities in the changes ofperiodicity and thickness from normal to alteredmyelin lamellae, and reasonable discussion wasmade in details on the morphological transition oftheir ultrastructures.