(15,16). RESULTSVitamin A supplementation resulted in prominence of lipocytes without significantly altering the light microscopic appearance of paraffin-embedded material. The total amount of collagen estimated by determination of hepatic hydroxyproline was the same in rats supplemented with vitamin A and rats not supplemented, the collagen concentration increasing in CC14-treated animals from 1.00 mg to 1.71 mg of hydroxyproline per g of dried, defatted tissue at the end of 6 weeks, and from 1.17 mg to 5.03 mg of hydroxyproline after 12 weeks. Light and electron microscopy After 1 or 2 weeks' duration of the experiments, the livers displayed centrolobular necrosis with steatosis in the surrounding parenchyma. The necrotic area contained, besides macrophages, conspicuous numbers of lipocytes, as shown by many Phosphin-3R-positive fat droplets imparting a fading vitamin A autofluorescence. Lipocytes were also recognized in 1 ,um thick sections and under the electron microscope. They were far more conspicuous, and indeed presented a striking appearance, after vitamin A supplementation (Fig. 1), when the cells appeared larger and contained a greater number of fat droplets, the latter imparting a strong vitamin A autofluorescence. They were intermixed with pigmented macrophages containing granules giving a yellow, nonfading autofluorescence, presumably of lipofuscin. Fibroblasts were not conspicuous in the necrotic area in the first 2 weeks.In animals treated for longer periods, connective tissue septa linking central zones with each other were observed after 6 weeks; after 12 and 24 weeks, the septa extended to the portal

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