1243 ULTRASTRUCTURE OP FREEZE SUBSTITUTED LIVER IN REYE'S SYNDROME (RS)

Rapid-frozen liver biopsy tissue and freeze-substitution (FS) or eryo-thinsectioning offer new methods of morphology, biochemistry, and x-ray microanalysis. Three liver biopsies from patients with RS and three from children with other diseases were studied by a new technique: rapid freezing and freeze substitution with osmium tetroxide-acetone. As previously described in muscle, mitochondrial (Mt) intracristal spaces are nonexistent and cristae appear as tight seven-layered structures in both RS and non-RS liver. Pleomorphlsm of RS Mt is striking; Mt enlargement is not watery expansion, but a non-aqueous milieu with no disruption of cristae and no ice artefact. In severely injured liver cells in RS, two populations of Mt are present. In contrast to Mt, peroxisomes contain large ice crystals, and their contents may be mainly aqueous. Large pools of smooth endoplasmic reticulum are discretely outlined, without ice artefact, as are Golgi lamellae. All hepatocyte organelles are easily recognizable by standard EM criteria, but membranes and spacial relationships differ from traditional EM processing. Thus, pleomorphism of Mt in RS is not an artefact of chemical fixation. The Mt matrix is not watery swelling: the matrix must contain material which prevents ice formation, probably protein.