Tissue fixation and staining by osmium tetraoxide: a possible role for alkaloids.

In vitro studies on the reactions of osmium tetraoxide, OsO4, with isoquinoline, pyridine, quinuclidine, and a series of structurally related alkaloids suggest that these species, under the conditions of normal tissue staining and fixation, are potentially osmiophilic. The structure of the products and their reactions with unsaturated substrates are described. The relevance of these results to the process of tissue staining and fixation of plant tissues containing alkaloids by OsO4 is discussed.