G. Weddell

A study of degeneration and regeneration in the divided rat sciatic nerve based on electron microscopy

SummaryExamination of the processes of traumatic degeneration of myelin in the proximal stump of divided rat sciatic nerves with the electron microscope reveals a complete and coherent series of Schwann cells which are progressively more advanced in the degradation of the myelin. The earlier stages appear to be a wrinkling and distortion of the myelin lamellae, followed by erosion of the circumferential lamellae with subsequent loss of cohesion and fragmentation of the myelin systems. Retraction of the myelin from the region of the node of Ranvier is observed. Myelin debris in the cytoplasm of Schwann cells occurs as vacuoles containing membranous material and pale staining globular inclusions which may develop from the membrane containing vacuoles. Cells containing similar inclusions are present ‘free’ in the endoneurium. The presence of similar cells associated with axons and only partly covered by basement membrane suggests that the cells ‘free’ in the endoneurium are ‘transformed’ Schwann cells digesting their myelin. These cells are most frequent between 3 and 6 days after nerve section and gradually disappear thereafter. We did not see any indications that cells other than Schwann cells were extensively involved in the traumatic degeneration of myelin.

Changes in the dermis of human hairy skin resulting from stripping the keratinized layer off the epidermis

SummaryBiopsies were taken at intervals up to 72 hours from two volunteers after the keratinized layer had been stripped from skin over the sacrum with adhesive tape. Within 16 hours there had been a proliferation of non-myelinated axons and accessory neural cells leading to axon sprouts growing into the epidermis, and by 40 hours a few accessory neural cells had also penetrated the epidermis. This proliferative stage reached a peak in 64 hours and by 72 hours degenerative changes were preponderant.Forty eight hours after stripping the mitotic index among the cells of the stratum germinativum had risen significantly and, 64 hours after stripping the histological picture presented by the skin as a whole resembled that in biopsies from clinically normal skin of patients with psoriasis.The relationship of these observations to a) the influence of nerve fibres on the mitotic activity of epidermal cells, b) the anatomy of cutaneous sensibility and c) the pathogenesis of leprosy, have been discussed.

A Note On The Presence Of Mycobacterium Leprae In The Central Nervous System Of A Mouse With Lepromatous Leprosy

Summary Results of a histopathological study of the tissues of a mouse experimentally infected with Mycobacterium leprae indicate that leprosy bacilli can cross the blood-brain barrier and multiply in the brain and that they gain access to ganglion cells by a haematogenous route. The findings are discussed with reference to lepromatous leprosy in man and the use of the thymectomised irradiated mouse as a model for the study of the disease.