Gastrointestinal responses to graded levels of cellulose feeding in conventional and germ-free mice.

Conventional (CV) and germ-free (GF) mice were fed on a semi-synthetic diet containing graded levels of cellulose (0, 5, 15 and 30%), and thereafter the length and wet weight of intestine, the morphology of mid-jejunum epithelium and the turnover of mid-jejunum epithelial cells were determined. The following results were obtained. enlarged stomachs were observed in CV mice fed on a non-cellulose or 30% cellulose diet, but there were no differences found among the four dietary groups in GF mice. On the other hand, no effect of intestinal bacteria was observed, at least with regard to caecum weight, since the responses of caecum wet weight to the graded cellulose intake in CV mice were similar to those in GF mice. The responses of intestine length to graded cellulose intake differed between CV and GF mice, indicating that intestinal bacteria may modify the length of intestine in some way. Marked differences were observed in the responses of villus length to graded levels of cellulose between CV and GF mice. That is, in CV mice there was a gradual increase in villus length as cellulose content increased, whereas in GF mice there was a marked decrease in villus length. In the CV mice, graded levels of dietary cellulose had no effect on the epithelial cell turnover. On the other hand, in the GF mice it was observed that the greater the amount of dietary cellulose, the faster the turnover rate becomes. As a result, dietary cellulose would enhance the turnover rates of jejunal epithelial cells only in the absence of intestinal bacteria.