Electron microscopy of glial reactions observed in CNS cultures

Long term myelinated cultures of new-born rat cerebellum were used in tests for myelinotoxic (presumptively antibody) factors in the sera of patients with multiple sclerosis. Positive reactions, with the optical microscope, take the form of early and gross swelling of the oligodendrocytes and intralamellar vesicular swellings in the myelin sheaths. With the electron microscope, a rapid and vigorous astroglial response was also seen, comprising glycogen accumulation in the astrocytic processes, profuse gliofibrillogenesis and a widespread investment of demyelinated axons and damaged oligodendrocytes by the reacting astrocytes. This astrocytic response was, however, not restricted to cultures demyelinated with multiple sclerosis serum but also occurred in ‘natural’ degeneration, in conditions implying a non-specific, protective or reactive response to injuries of the myelinated axons and its rapidity and vigour were its notable features relevant to neuropathology. Possible biochemical implications of the phenomenon are discussed.