Accumulation of organelles at the ends of interrupted axons

Summary Proximal and distal stumps of the sciatic nerve of rats were examined with the light and electron microscope in the course of 48 hours following nerve crush. On both sides of the lesion organelles accumulate in axons beyond regions disorganized by injury. A stretch of clear axoplasm filled with fine granules usually separates the cone of accumulating particles from the damaged part of the fibre. From two hours onwards closely packed vesicles, tubules, mitochondria and other organelles form dense pellets which fill up the whole lumen of the fibre. Further away from the fibre tip organelles are stranded at the circumference only, whereas the central core is occupied by neurofilaments. In a number of fibres no pellets are observed and only a moderately increased network of axoplasmic reticulum is seen at the fibre ends.Measurements on isolated fibres have shown that the length of the pellet increases with time on both sides of the lesion up to 18 hours after crush; thereafter the elongation is arrested in the distal stump, while in the proximal stump it continues further at a slower rate.The authors wish to acknowledge gratefully the technical assistance of Mrs. M. Sobotková, Mr. M. Doubek, Mrs. J. Waryszewska and Mrs. B. Lwowska.