The effect of anisotonic media upon cellular ultra-structure in fresh and fixed rat brain

Summary When tissue slices or small blocks of unfixed rat cerebrum are incubated in various anisotonic physiological media, distinctive morphological changes are induced in glial cells, neurons, and endothelial cells. The variation in observed cellular swelling and shrinkage may be related to differences in ionic content of the cytoplasm of these cells. When HAA, glutal, and osmium tetroxide fixed tissue is incubated in this manner, only the cerebrum fixed in HAA responds to osmotic inequilibrium in a manner similar to unfixed tissue. Although HAA does not fix tissues very well, the permeability of plasma membranes in the brain appears to be less altered by HAA than by glutal or osmium tetroxide. The relationship of these findings to a demonstration of the extracellular space in HAA fixed tissues is discussed.This work was supported by grants (U-1293) from the Health Research Council of the City of New York and (NB 04161-02) from the National Institute of Neurological Disease and Blindness of the National Institutes of Health.