CLUSTER FORMATION OF BASAL-GRANULATED CELLS IN THE INTESTINAL VILLI OF THE FETAL JAPANESE MONKEY (MACACA-FUSCATA-FUSCATA)

Segi's cap, an aggregation of the basal-granulated cells in the intestinal villi of the fetal Japanese monkey was investigated by means of light microscopy and immunocytochemical techniques. Characteristic Segi's caps were observed at the tips of the villi in the duodenum and upper jejunum in fetal Japanese monkeys, aged 120 and 140 days. The Segi's cap of Japanese monkeys is characterized by the following morphological features: 1) There are relatively fewer caps per section in comparison with humans. 2) The number of basal-granulated cells of the cap is also less than in humans. 3) The characteristic indentation at the center of the Segi's cap, reported in humans, cattle and pigs is only rarely present. 4) Argentaffin cells, which are now known as serotonin-containing cells, are present in the monkey Segi's cap. 5) Somatostatin-, motilin- and CCK-immunoreactive cells are found in the monkey Segi's cap.