ABSTRACT. No direct evidence that genetically modified (GM) food may represent a possible danger for health has been reported so far; however, the scientific literature in this field is still quite poor. Therefore, we carried out an ultrastructural morphometrical and immunocytochemical study on hepatocytes from mice fed on GM soybean, in order to investigate eventual modifications of nuclear components of these cells involved in multiple metabolic pathways related to food processing. Our observations demonstrate significant modifications of some nuclear features in GM-fed mice. In particular, GM fed-mice show irregularly shaped nuclei, which generally represents an index of high metabolic rate, and a higher number of nuclear pores, suggestive of intense molecular trafficking. Moreover, the roundish nucleoli of control animals change in more irregular nucleoli with numerous small fibrillar centres and abundant dense fibrillar component in GM-fed mice, modifications typical of increased metabolic rate. Accordingly, nucleoplasmic (snRNPs and SC-35) and nucleolar (fibrillarin) splicing factors are more abundant in hepatocyte nuclei of GM-fed than in control mice. In conclusion, our data suggest that GM soybean intake can influence hepatocyte nuclear features in young and adult mice; however, the mechanisms responsible for such alterations remain unknown.Key words: cell nucleus/liver/genetically modified soybean Humans have been altering the genome of animals and plants for centuries and selective breeding has been used to produce some desirable characteristics such as yield increase, quality modifications or resistance to diseases. Recently, genetic modification has become the domain of molecular biology and genetic engineering, and genetically modified (GM) organisms have been produced in which new genes have been inserted into the original genome. In particular, genetic engineering has been widely applied in agriculture, thus creating GM crops which are nowadays distributed all over the world.No direct evidence that GM food may represent a possible danger for health has been reported so far; however, the scientific literature in this field is still quite poor (Schubbert et al., 1994(Schubbert et al., , 1997(Schubbert et al., , 1998Ewen and Pustzai, 1999;Chiter et al., 2000;Edwards et al., 2000;Halford and Shewry, 2000), especially as to the possible effect of a diet involving a significant amount of GM plants.The liver is a primary site for biotransformation of the products of digestion and is strategically located between the intestinal tract and the general circulation. Moreover, it degrades and detoxifies toxic compounds received from the intestines or from the general circulation and excretes them in the bile. Finally, it synthesizes many protein components of blood plasma and exercises an important degree of control over the general metabolism. Therefore, hepatocytes
