Histochemical Study of Different Types of Brain Edema

It has been shown previously (Wolman & Wiener, 1965) that one-half of the lipid constituents of myelin can be extracted by water after treatment with Na ions or other agents which increase the hydrophilia of polar lipids, and that such an extraction is prevented by Ca ions or other agents which decrease the hydrophilia. The other half of the lipid constituents are not sensitive to ions or other hydrophilia- increasing agents. These findings indicate that the layer of the plasma membrane which faces the extracellular space might be different from the layer which faces the intracellular space. Evidence favoring this view has been adduced by electron-microscopy (Sjostrand, 1963) and X-ray diffraction (Finean, 1963). The well-known fact that the inside of cells is electrically negative in respect of the outer surface also favors the notion that the two layers of the plasma membrane differ in structure and composition. It seems reasonable to assume that the two layers also differ in their enzyme content.