Staining tissue with methacrylate casts for light microscopy

Scanning electron microscopy (SEM) of methyl methacrylate casts and light m icroscopy (LM) of tissue are well-established methods for studying the micr ocirculation. The two are complimentary, but methacrylate is transparent an d thus its presence is often not appreciated by LM. Applying histologic sta ins to sections of tissue embedded in methyl methacrylate would allow the r elationships of light microscopic and scanning electron microscopic views o f cast vasculature to be better appreciated. We sought to test different st ains on cast tissue to find one that would accent the cast. Surgically remo ved and autopsied human lungs were cast with methacrylate and processed by routine light microscopic methods. They were stained with the hematoxylin a nd eosin, Masson trichome, elastic-van Gieson, Grocott methenamine silver, Brown-Brennan, and Ziehl-Neelsen methods. The Ziehl-Neelsen procedure stain ed the methacrylate best, giving it a red color. This procedure also worked well without heating. We conclude that (1) cast methacrylate lung can be p rocessed for routine LM with excellent results; (2) methacrylate stains wel l with the Ziehl-Neelsen technique; (3) the acid-fast stained cast lung sho ws capillaries and cells in both normal and diseased lung better than the r outine hematoxylin and eosin stain; (4) this technique can be used to asses s filling and correlate findings on the same tissue with the two different microscopic methods.