Variations in ultrastructural nuclear changes in hepatocarcinogenesis

Abstract

The ultrastructural changes observed in the nuclei and nucleoli of liver cells following the acute and chronic administration of several hepato-carcinogens are discussed. Three major types of nucleolar change have been observed following acute administration: 1. 1. Macrosegregation—following aflatoxin, lasiocarpine and tannic acid. 2. 2. Microsegregation—following DMN and 3′Me DAB. 3. 3. Enlargement—following thioacetamide and ethionine. In chronic toxicity nucleolar macrosegregation was not observed in precancerous liver or in tumours but some degree of microsegregation and nucleolar enlargement persisted. The significance of these changes in the light of reported biochemical data on the action of these carcinogens is discussed, with special reference to DNA binding. It is concluded that neither the nucleolar nor the nuclear changes observed in both acute and chronic intoxication can be regarded as specific manifestations related to the carcinogenic process, in view of their apparent ability to regress and lack of consistency in chronic carcinogenesis.