Optimal conditions for methacrylate embedding of certain tissues and cells sensitive to polymerization damage

Some factors affecting polymerization damage in inethacrylate-embedded mouse testis and R. spheroides bacteria have been examined. Polymerization by an intense source of UV light at room temperature has been shown to be a superior method of curing. Long soaking of the tissue in prepolymerized methacrylate is beneficial and, in some cases, a brief additional staining in a 2 per cent solution of chromic nitrate in alcohol improves preservation. With these modifications permanganate-fixed mouse tissues and osmic-fixed bacteria may be satisfactorily preserved in methacrylate, and considerably shorter osmic acid and permanganate fixation times of tissue blocks are possible. In some fields of electron microscope cytology, e.g., the examination of cellular damage produced by ionizing radiations, the described modifications of the methacrylate-embedding technique have been found essential for the elimination of polymerization artifacts which otherwise obscure pathological changes under observation.