Scanning electron microscopy of aberrant crypt foci in rat colon

The surface of the colon mucosa of 1,2-dimethylhydrazinetreatedF344 rats was examined with the scanning electron microscope.A detailed examination of the mucosal topography revealed fociwith one to several aberrant crypts. These were seen as structureselevated from the background mucosa. The shape of the luminalopenings of the aberrant crypts varied from elongated or tortuousto circular. However, we found no ultrastructural variationsbetween the different aberrant crypt foci (ACF) or between theACF and the background mucosa. There was no direct relationshipbetween the size of ACF and the number of aberrant crypts perfocus, which may be explained by the mechanism of crypt fission;in two aberrant crypts we discovered the formation of a transverseepithelial septum, dividing the large crypt into two smallercrypts. The gross morphology of the ACF observed by scanningelectron microscopy and light microscopy was in principle thesame.