[Ultrastructure of the gastrointestinal epithelium in the marmoset (Callithrix jacchus)]

The epithelium of the stomach and intestine of one and three days old as well as adult marmosets was investigated using transmission electron microscopy and was compared with already existing data of man and the laboratory rodents, rat, mouse and guinea-pig. On postnatal day (PD) 1, the enterocytes possessed an inframicrovillous membrane system and giant lysosomes which were absent in adult marmosets whereas the surface and glandular epithelial cells of the stomach showed all structures which were also typical for adult animals. Enterocytes rich in fat and glycogen were only present on PD 1. In the large intestine the vacuolated cells were more frequently seen on PD 1 and 3 than in adult marmosets. The endocrine cells of newborn animals corresponded to those in the gastric and intestinal epithelium of mature animals, occurred everywhere in the lower digestive tract and could be subdivided at least into EC, ECL, D and L and EG cells respectively; a further subdivision was not possible by conventional transmission electron microscopy. Compared with rats, mice and guinea-pigs mostly used for developmental studies of the digestive tract, marmoset monkeys differed especially from the gastrointestinal epithelium of rats and mice but also from guinea-pigs. By contrast comparisons with the human situation are difficult due to the lack of representative electron microscopic findings on the gastrointestinal epithelium. If one considers the close phylogenic relationship between marmosets and man, the marmoset data should be transferable to the human situation rather than the findings obtained for rats, mice and guinea-pigs. In the epithelium of the adult gastrointestinal tract clear-out ultrastructural differences could not be found between these species.