Spatial and temporal changes in cell proliferation in the chick jejunum during the folding of the ridges into zigzags.

Vilification in the chick gut involves the formation of longitudinal ridges, establishment of their zigzag pattern and emergence of individual villi. Although the morphological changes during vilification are well known in the chick gut, the pattern of cell proliferation during this process is poorly understood. The aim of the present study was to correlate spatial and temporal changes in cell proliferation to folding of the longitudinal ridges into zigzags. Embryos on the 13th pos-incubation day were injected with BrdU and sacrificed at 8 h intervals up to 64 h after injection. Spatial and temporal changes in cell proliferation were observed during the folding the longitudinal ridges into zigzags. Cell proliferation occurred throughout the epithelium of the folded ridges, was predominant in the epithelial cells at the sides of the zigzagging ridges, and finally appeared in the epithelial cells at the tips of the zigzag ridges. In conclusion, cell proliferation might be a requirement for the folding of the longitudinal ridges into zigzags.