The relationship between intestinal colonization and the small bowel mucosal cellular proliferation rate during conventionalization of the germfree mouse was examined. 16 mice were maintained under standard germfree conditions, and 54 others were conventionalized. Migration of the small bowel epithelial cells was followed by radioautography with administration of tritiated thymidine. Colonization was followed by qualitative and quantitative bacteriological fecal analyses. The percentages of the villi labeled (as determined by cell count) 24, 48, and 72 hr following thymidine administration showed immediate progression in the conventionalized animals from the germfree villus migration time (4 days) toward the conventional villus migration time (2 days). The epithelial migration rate of animals conventionalized for 8 days was comparable to that of conventional animals. After conventionalization, aerobic and anaerobic organisms undergo a period of extensive multiplication; however, 72 hr later the number of these microorganisms cultured in the stool decrease and are similar to those recovered from normal animals. Coliforms and streptococci are recovered in large numbers only in the first days after conventionalization, while the Bacteroides are first recovered in significant numbers on the fifth day of conventionalization. Except for smaller numbers of Bacteroides, the bacterial populations in the stools of the conventionalized animals are qualitatively and quantitatively similar by the eighth day of conventionalization to those of true conventional mice. Adaptive balance between cell proliferation and sloughing, and thus migration rate, begins immediately after conventionalization of germfree animals as bacterial populations establish themselves throughout the gastrointestinal tract, and results in a doubling of the mucosal cell turnover after 8 days. At this time both the small intestinal epithelial cell migration rate and the intestinal microflora are similar to those of conventional animals.

Animals↗

PubMed1969

Lactulose in the treatment of chronic portal-systemic encephalopathy. A double-blind clinical trial.

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Adult↗

PubMed1969

Effects of neomycin and penicillin administration on mucosal proliferation of the mouse small intestine. With morphological and functional correlations.

The effects of an oral neomycin and penicillin regimen on intestinal bacteriology and on morphology and function of the small intestine of mice were investigated. Quantitative and qualitative stool cultures on selective media of the treated animals revealed only growth of yeast organisms. The treated animals developed enlargement of the ceca with fluid contents and watery stools, resembling characteristics of germfree animals. Radioautography with tritiated thymidine revealed an increased epithelial cell migration rate in the mice treated with the antibiotics for 3 to 5 wk. A slight increase in villus height was also noted. The treated male mice showed greater variance than the treated females in epithelial cell migration rates. Histochemical staining reactions showed a decrease in nonspecific esterase and in NADH dehydrogenase activity in the proximal gut of the antibiotic animals. Stains of distal gut and those for acid and alkaline phosphatase, NADPH dehydrogenase, lactic dehydrogenase, and succinic dehydrogenase were similar to the controls. A slight increase in sucrase activity and a slight decrease in lactase activity in the antibiotic animals was observed in contrast to control animals. Germfree mice, however, had greater sucrase and lactase activity. Transport of L-methionine was slightly reduced in the distal segment of the treated animals. Since the direction of these changes is away from the intestinal state observed in germfree animals, they are probably the result of the direct action of the antibiotics on the gut.

Animals↗

PubMed1969