Developing elastic tissue. An electron microscopic study.

Electron microscopic identification of elastic tissue in normal and disease states has been uncertain due to the lack of a specific electron-dense stain. Recently we introduced a silver porphyrin electron microscopic stain (silver tetraphenylporphine sulfonate) for the identification of adult elastic tissue. This stain has now been employed to study the development of elastic tissue with the aim that new and old elastica can be differentiated at the electron microscopic level. Present observations showed that developing elastica consisted of two distinct morphologic components. Each portion exhibited different staining properties with the silver porphyrin and lead citrate. One component was fibrous and the other amorphous. The fibrous component stained with lead citrate while the amorphous stained with the silver porphyrin. The fibrous component was the first to appear; the amorphous portion appeared later in development and was formed within the fibrous matrix. Mature elastic tissue was devoid of the fibrous component. Based upon the morphologic appearance and staining properties, one can now differentiate between newly formed elastic tissue and the existing one in various disease states.