Segmented filamentous bacteria in the rodent small intestine: Their colonization of growing animals and possible role in host resistance toSalmonella

The establishment and proliferation of a model population of autochthonous surface-associated microorganisms in the small bowel of growing rats (2–12 weeks of age) was studied. Segmented filamentous bacteria on the distal ileal villi were examined by scanning electron microscopy (SEM) and countedin situ by transect line analysis. In young animals, these bacteria first colonized the villous base, but occupied all areas on the villus by adult age. Their distribution on Peyer's patches was also noted.In growing animals, colonization of the ileal villi by filamentous bacteria was significantly correlated to the development of host resistance to fatal infection by orally-dosedSalmonella enteritidis. In animals givenSalmonella and examined by SEM and transmission EM (TEM), the pathogen was seen only on ileal tissue surfaces, predominantly the villous base, from which the autochthonous population was absent. Conversely, in animals with filamentous bacteria,Salmonella surface colonization was not observed. The results suggest a possible protective role for the surface flora in the small bowel.     

Carboxylesterase in the liver and small intestine of experimental animals and human

Native polyacrylamide gel electrophoresis showed carboxylesterase (CES) to be the most abundant hydrolase in the liver and small intestine of humans, monkeys, dogs, rabbits and rats. The liver contains both CES1 and CES2 enzymes in all these species. The small intestine contains only enzymes from the CES2 family in humans and rats, while in rabbits and monkeys, enzymes from both CES1 and CES2 families are present. Interestingly, no hydrolase activity at all was found in dog small intestine. Flurbiprofen derivatives were R-preferentially hydrolyzed in the liver microsomes of all species, but hardly hydrolyzed in the small intestine microsomes of any species except rabbit. Propranolol derivatives were hydrolyzed in the small intestine and liver microsomes of all species except dog small intestine. Monkeys and rabbits showed R-preferential and non-enantio-selective hydrolysis, respectively, for propranolol derivatives in both organs. Human and rat liver showed R- and S-preferential hydrolysis, respectively, in spite of non-enantio-selective hydrolysis in their small intestines. The proximal-to-distal gradient of CES activity in human small intestine (1.1-1.5) was less steep than that of CYP 3A4 and 2C9 activity (three-fold difference). These findings indicate that human small intestine and liver show extensive hydrolase activity attributed to CES, which is different from that in species commonly used as experimental animals.     

Effect of pH on protease activities in the large intestine

The influence of pH on proteolysis in different fractions of human faeces was studied with a variety of chromogenic substrates. The pH optima of proteases in the washed cell fraction and washed particulate fraction were neutral to alkaline, whereas extra-cellular proteolysis in the cell-free supernatant fraction was relatively insensitive to pH over the range 6·4–8·0. Measurements with p -nitroanilide substrates suggested the presence of more than one elastase-like, trypsin-like and chymotrypsin-like protease in the gut.     

Hydrolases in the large intestine in rats with various experimental pathologies

In the colon mucous membrane, activity of a wide range of membrane and mainly intracellular enzymes was studied in the organism at different conditions. The data obtained suggest participation of digestive hydrolases in the colon not only on postdigestive processes but, in certain states of the organism, in digestive processes too.     

Effect of radioprotective agents on the epithelium of small intestine mucosa in irradiated animals

In experiments on irradiated (10 Gy) mice a study was made of the morphological changes in the small intestine mucosa and in its functional status estimated by absorption of stain uranine. It was shown that the preventive administration of cystamine and S-(omega)-aminopropyl-beta-aminoethylthiophosphoric acid to the exposed mice increased the proliferation processes in the crypt and the cell movement per villus providing a favourable effect of the radioprotective agents on the absorption function.     

Protection against Candida albicans gastrointestinal colonization and dissemination by saccharides in experimental animals

Pre- or post-treatment of duodenal discs with mannose, N-acetylglucosamine or chitin soluble extracts (CSE) prevented the adherence of Candida albicans to gastrointestinal tract. CSE was the most effective in blocking the adherence of C. albicans. Treatment of infant mice with saccharides significantly reduced the systemic spread of C. albicans inoculated into the gut. The best protection was obtained when the saccharides were given 2 days prior to the infection and continued over the course of the infection. However, systemic spread was reduced with a single dose of saccharide 30 min before infection. The saccharides may bind to the gastrointestinal mucosa and block the attachment of C. albicans.     

Optimal method of isolation of supra-epithelial mucous layer of the small intestine in experimental animals

Experimental data on the activity of digestive endo- and exo-hydrolases in supra-epithelium mucus layer has been presented. Mucus layer has been obtained on special vibrating setting from the turned out intestinal preparation. Different conditions of work and medium of isolation have been used. The setting permits to obtain intestinal supra-epithelium mucus more completely and also prevents epithelium damages and hiting of damaged villi.     

Enterohemorrhagic Escherichia coli senses microbiota-derived nicotinamide to increase its virulence and colonization in the large intestine

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Effect of ribonucleases on humoral immunity of experimental animals

The stimulating effect of RNAases on the humoral immune response was observed in experiments with animals. It was shown that the stimulation was mainly mediated by the system of T-lymphocytes. In the T-lymphocyte system positive sensitivity to the enzymes was attributed to the T-helper cell subpopulation.     

Abnormal Paneth cell granule dissolution and compromised resistance to bacterial colonization in the intestine of CF mice

Paneth cells of intestinal crypts contribute to host defense by producing antimicrobial peptides that are packaged as granules for secretion into the crypt lumen. Here, we provide evidence using light and electron microscopy that postsecretory Paneth cell granules undergo limited dissolution and accumulate within the intestinal crypts of cystic fibrosis (CF) mice. On the basis of this finding, we evaluated bacterial colonization and expression of two major constituents of Paneth cells, i.e., alpha-defensins (cryptdins) and lysozyme, in CF murine intestine. Paneth cell granules accumulated in intestinal crypt lumens in both untreated CF mice with impending intestinal obstruction and in CF mice treated with an osmotic laxative that prevented overt clinical symptoms and mucus accretion. Ultrastructure studies indicated little change in granule morphology within mucus casts, whereas granules in laxative-treated mice appear to undergo limited dissolution. Protein extracts from CF intestine had increased levels of processed cryptdins compared with those from wild-type (WT) littermates. Nonetheless, colonization with aerobic bacteria species was not diminished in the CF intestine and oral challenge with a cryptdin-sensitive enteric pathogen, Salmonella typhimurium, resulted in greater colonization of CF compared with WT intestine. Modest downregulation of cryptdin and lysozyme mRNA in CF intestine was shown by microarray analysis, real-time quantitative PCR, and Northern blot analysis. Based on these findings, we conclude that antimicrobial peptide activity in CF mouse intestine is compromised by inadequate dissolution of Paneth cell granules within the crypt lumens.