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Germfree suckling rats were infected with an SA11 rotavirus strain. Infected pups developed diarrhea associated with histopathological changes. The virus was detected in feces and in the small intestine. Cellular vacuolation was observed in the villi of the jejunum. These results provide a new model for further investigations of group A rotavirus infection.

No information concerning the effect of weaning on intestinal cell proliferation is currently available in large species with early intestinal morphogenesis, a group including most domestic animals and humans. Changes in intestinal morphology and epithelial cell renewal were investigated in 1-, 5-, and 8-wk-old suckling and 8-wk-old weaned lambs after injection of [3H]thymidine. In suckling lambs a gradual increase in crypt depth occurred with age, especially in the proximal intestine, whereas villus height was significantly reduced in the distal regions. At 8 wk of age weaned and prolonged-suckling lambs exhibited no significant differences in crypt depth throughout the intestine and in villus height proximally. However, weaned lambs had shorter villi in the jejunum and ileum. The highest enterocyte migration rates (4.4-9.7 microns/h) were observed in 1-wk-old lambs. In suckling animals, migration rates decreased with age by 60, 51, and 11% in the duodenum, jejunum, and ileum, respectively. Weaned and prolonged-suckling 8-wk-old lambs had a similar rate of enterocyte migration in the ileum. Furthermore, ruminating animals exhibited only slightly higher migration rates in the duodenum and the jejunum (53 and 15%, respectively). In suckling lambs, epithelial cell renewal required 2.1-4.0, 4.5-6.3, and 4.0-5.3 days at 1, 5, and 8 wk of age, respectively, whereas labeled cells reached the tips of the villi within 3.0-3.1 days in weaned animals. These data suggest that the suckling period corresponds to a gradual and important phase of postnatal intestinal adaptation in the sheep, a species with early patterns of intestinal cell replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of the mode of sterilization of the diet (gamma-irradiation vs. autoclaving) on the histamine and mast cells distribution in the intestinal mucosa, was studied in germ free (GF) and conventional (CV) rats. Interactions between the diet and the digestive microflora were observed. Histamine concentration and mast cells counts are higher in CV rats small intestine than in GF's. The differences are increased with the irradiated diet. At the opposite in the hindgut, these values are higher in GF than in CV rats, especially in the rats fed the steam sterilized diet. The variations in the wall histamine contents and in the mucosal mast cells counts due to the diet and/or the microflora do not appear to be always correlated.

Renewal of the ileal epithelium has been studied in germ-free (GF) and conventional (CV) rats fed with a semi-synthetic diet in the following forms: a) pellets sterilized by autoclaving (Pel. Au. diet); b) powder sterilized by gamma irradiation; when given to the rats, its weight in water was added to make a paste (Pa. I. diet); c) powder treated as (b) but with 10 p. 100 lactose added (L. Pa. I. diet). Ileal epithelium renewal time was similar in the GF rats fed with the Pel. Au. and Pa. I. diets. It was shorter in the CV rats fed with these two diets than in the GF rats and also in the CV rats given the Pa. I. diet than in those given the Pel. Au. diet. In GF and CV rats fed with the lactose diet, L. Pa. I., ileal epithelium renewal time was similar. These different effects were mainly due to variations in the number of cells produced in Lieberkühn's crypts. They were not related to changes in the intestinal bile salts pool caused by the different diet treatments.

The most striking effect of Clostridium difficile infection is its degrading of the intestinal barrier. The aim of this study is to establish whether the cellular or paracellular constituent of the barrier is the initial target of the toxins produced by C difficile. Accordingly, the caecal epithelium of C3H/He mice was challenged under three experimental conditions with the C difficile strain VPI 10463: (1) by in vivo inoculation of axenic mice, (2) by adding the toxins to ligated caeca in vivo, and (3) by adding them to the mucosal side of isolated caeca in Ussing chambers. Under all three conditions, the epithelial barrier was tested in caeca mounted in these chambers. The transepithelial potential difference (PD), electrical conductance (G), and intact and degraded Horseradish peroxidase (HRP) fluxes were used as indexes of permeability. Results were as follows: (1) In axenic mice, C difficile caused severe infection, produced toxins A and B, reduced PD, and enhanced G and intact HRP fluxes without changing degraded HRP fluxes, (2) four hours after the toxins were added to ligated caeca in vivo, PD was relatively unaltered, but G, and intact and degraded HRP fluxes increased, and (3) when toxins were added to caeca during two hours in the Ussing chambers, the only modification observed was an increase in degraded-HRP fluxes. These results indicate that the C difficile toxins gradually cause intestinal lesions. After an apparent resistance, they stimulate the endocytotic process and then increase paracellular permeability and finally cause loss of cell viability.

The length and diameter of enterocyte microvilli at mid-villus position were measured on electron-micrographs. The duodenum, jejunum and ileum of axenic (germfree) and holoxenic (conventional) inbred rats fed the same diet have been studied. The microvilli were significantly shorter in all these intestinal regions when the microflora was present. The decrease in microvillus length (due to the presence of microflora), expressed as a percentage of the length in axenic rat, was 5% in the duodenum, 9% in the jejunum and 18% in the ileum. This was not true of microvillus diameter where only the values found for the ileum of axenic rat were significantly lower, the others not differing among themselves. In conclusion, the presence of a total microflora led to a decrease in the length of enterocyte microvilli. These results have been discussed in relation with studies on renewal and enzyme activity in the intestinal epithelium.

The most striking effect of Clostridium difficile infection is its degrading of the intestinal barrier. The aim of this study was to characterize the effect of C. difficile toxins on the epithelial layer including cellular and paracellular constituents. Accordingly, the caecum of C3H/He mice was challenged under 3 experimental conditions with C. difficile strain VP1 10463 : 1) by in vivo inoculation of axenic mice, 2) by adding the toxins to ligated caeca in vivo, and 3) by adding them to the mucosal side of isolated caeca in Ussing chambers. Under all 3 conditionals, the epithelial barrier was tested in caeca mounted in these chambers. The transeptithelial potential difference (PD), electrical conductance (C), and intact and degraded Horseradish peroxidase (HRP) fluxes were used as indexes of permeability. Results : 1) In axenic mice, C. difficile caused severe infection, produced toxins A and B, reduced PD, and enhanced C and intact HRP fluxes without changing degraded HRP fluxes; 2) 4 hours after the toxins were added to ligated caeca in vivo, PD was relatively unaltered, but C intact and degraded HRP fluxes increased, and 3) when toxins were added to caeca during 2 hours in the Ussing chambers, the only modification observed was an increase in degraded-HRP fluxes. These results indicate that the C. difficile toxins gradually cause intestinal lesions. After an apparent resistance, they stimulate the endocytotic process, increase paracellular permeability and finally cause loss of cell viability.

Intestinal permeability to macromolecules during viral enteritis in conventional and germ-free suckling mice