A REVIEW OF RAPID MICROWAVE FIXATION TECHNOLOGY - ITS EXPANDING NICHEIN MORPHOLOGIC STUDIES

Microwave (MW) fixation methods are important because excellent preser vation of both cell structure and antigenicity can be attained several orders of magnitude faster than by routine chemical fixation methods. However, because of the limitations of commercial MW ovens, fixation results are often irreproducible. We present a standardization protoco l for MW fixation in household MW ovens that emphasizes magnetron warm -up; the use of a water load during sample irradiation. of an agar/sal ine/Giemsa model to evaluate uniformity of irradiation within the MW c avity, and of specimen containers with one dimension less than 1.5 cm; and fast specimen handling to prevent conductive heating artifacts af ter irradiation. We describe a prototypic MW device that improves the precision of sample irradiation and fixes blocks of tissue and cells i n suspension in milliseconds. The solutions used to immerse the specim en during irradiation influence the specimen morphology. Aldehyde- or osmium-containing solutions used simultaneously with MW irradiation re sulted in the best morphologic preservation of specimens up to 1 cm3. Using MW fixation methods and a postembedding, ultrastructural immunog old-labeling approach, we have localized granule chymase and histamine in rat mast cells and amylase in rat parotid acinar cells.