[Demonstration of apolar lipids in paraffin-embedded tissues with special reference to pathological fatty degeneration in Tangier disease and other dyslipoproteinemias].
The oxidative cross-linking effect exerted by OsO4 on lipids and the blackening of osmiophilic structures resulting from reduction of OsO4 constitute long-known phenomena. Nevertheless, osmic acid has rarely been used for lipid staining as various even non-lipid-containing tissue structures are more or less intensively blackened by OsO4. If one treats osmicated tissue sections with certain oxidants (e.g. ammonium persulfate) in aqueous solution, then all the black OsO4 reduction products which are exposed to the aqueous phase are oxidized and thereby bleached. This applies e. g. to all proteins and polar (hydrophilic) lipids. Only apolar lipids retain their more or less black color and can be stained subsequently with Sudan dyes. Based on this principles, a new procedure has been developed which is effective on paraffin sections obtained after previous block osmication. This OBS procedure can also be used for very precise localization of appropriate lipid structures as can be demonstrated in cases of pathologic lipid deposits in an-alpha- and in a-beta-lipoproteinaemia, in type III hyperlipoproteinaemia, and in diverse other dyslipoproteinaemias as well.