Producing frozen sections of calcified bone.

We describe a procedure for the rapid production and maintenance of fresh frozen bone biopsies which can be used for a variety of immunohistochemical techniques. Within 5 min of excision, tissue is placed in cold 5% polyvinyl alcohol, surrounded with 3% carboxymethylcellulose in a hand made aluminum foil embedding mold and frozen by immersion in an absolute ethanol/dry ice slurry at -70 C. The tissue block is attached to the specimen stub with cryocompound and installed in a -32 C cryostat whose tungsten carbide D profile knife is maintained at -70 C. Automatic controls are set at a slow cutting speed and the "sectioning window" is adjusted to fit the biopsy size. Knife angle, thickness gauge and antiroll bar are changed to produce a complete section. The block face is smoothly "papered" with a polyvinylpyrrolidone (PVP) impregnated Ross lens paper strip. A single section is cut and positioned on a sequentially numbered, acid cleaned, double dipped chrome-alum gelatin coated slide; adhesion is aided by "press-blotting" with bibulous paper. Sections are stored at -20 C or in a desiccator at room temperature. A brief fixation followed by removal of the water soluble PVP and lens paper generates fresh frozen bone sections suitable for further analysis.