ULTRARAPID TISSUE FREEZING IN LIQUID NITROGEN

Abstract

Tissue, powder-coated prior to immersion in liquid nitrogen, cools to a center temperature of –50°C four to five times faster than comparable tissue immersed in ethylene glycol monomethyl ether (Cellosolve®, Union Carbide Corp.) at –79°C and twice as fast as tissue immersed uncoated in isopentane-liquid nitrogen (–155°C) or liquid mitorgen. The morpohlogical preservation of tissue structure when this method is used on blocks of kidney, pancreas, and liver, for either enzymic reactions or oversight staining technieques, is comparable to that obtained with hydrocarbon baths cooled in liquid nitrogen. The coating method is recommended as a substitute, rather than as a replacement, for hydrocarbon baths cooled in liquid nitrogen, when circumstances demand the advantages of safety, simplicity and speed.