Cryostat Techniques: Methods for Improving Conservation and Sectioning of Tissue

Tissues have been conserved for satisfactory enzymatic histochemical assay for up to 12 mo by low temperature storage (in a dry ice chest or at -40° C) and by measures designed to offset the deleterious effects of sublimation of H₂O by using the following modifications of standard procedures (which include steps to give a mechanical support to otherwise fragmenting sections): 1. tissue blocks are coated with a polystyrene solution between each storage period; 2. modified bolts are used as tissue holders and types of bolt holders have been designed to fit on standard microtomes which permit manipulation of each tissue block independently of its mates on the same bolt holder, or the simultaneous cutting of all blocks on any one holder with each advance of the microtome feed; 3. tissues are coated with 20% polystyrene in methylene chloride prior to cutting and rubber cement painted on the slide as an adhesive. Lillie's 20% polystyrene diethylbenzene is used as a mounting medium. Other details of practical importance include the technique of freezing, control of moisture within a cryostat and on the microtome, and tests on histochemical procedures.