Electron microscopic radioautographic observations suggesting absorption of lipid by the nucleus.

Abstract

In the course of electron microscopic autoradiographic studies of the transport of ingested lipids from the blood to the cells of adipose tissue and liver, using 3H-palmitic acid as tracer, silver grains were found not only over the cytoplasm and fat droplets but also over the nuclei, suggesting absorption of lipids by the nuclei. Representative autoradiographs are described. The questions of localization and of the nature of the radioactive material in the nuclei are discussed. Special attention was given to the possibility that the grains represent degradation products of the palmitic acid. This possibility was ruled out, however, on chemical grounds. The present findings invite further investigation of isolated nuclei and their fractions, using, in addition to autoradiography, chromatographic and radiochemical methods.