Changes associated with the basal lamina during metamorphosis of Xenopus laevis

We examined the changes in the morphology of the basal lamina of the colon, abdominal wall and tail muscles of tadpoles during metamorphosis and compared our results to those previously obtained for the small intestine. At the early stage of metamorphic climax (stages 60-62), we observed a curving of the basal lamina along the processes of the epithelial cells. At a later stage of metamorphic climax (stages 63-66), more extensive curving and folding of the basal lamina were observed. The basal lamina of the mesothelial cells in the abdominal wall did not change extensively as compared to the colon. Folded basal lamina was observed among degenerated muscle cells. Our results suggest that the folding of the basal lamina depends on the degree of deformation of the particular organ, which occurs mainly by physical factors such as the shortening or shrinking of the organ due to cellular degeneration. Cells that are newly differentiated produce an additional basal lamina, which results in transient doubling or layering. The combination of physical factors and cell differentiation results in a basal lamina that is more complex and contains folds and layers.