Preparation of the mammalian organ of Corti for scanning electron microscopy

The effect of various standard tissue preparation procedures for scanning microscopy on the morphology of the mammalian organ of Corti has been examined. Comparison was made of (i) different fixatives: glutaraldehyde (GA) alone, osmium (Os) alone, GA and Os together and GA followed by Os; (ii) freeze-drying (FD) versus critical point-drying (CPD); (iii) ligand binding of osmium with thiocarbohydrazide (TOTO procedure) versus sputter coating to provide a conductive coat. Results were assessed in terms of known structural parameters in fresh tissue. It is shown: (i) that double fixation, either GA, Os together or GA followed by Os, consistently produced less tissue distortion than either fixative alone, (ii) that FD produced less shrinkage of the tissue than CPD, and (iii) that the TOTO procedure appeared to rigidify the tissue and enhanced preservation of the morphology.