Jean-Claude Meslin

Variation of mucin distribution in the rat intestine, caecum and colon: effect of the bacterial flora.

The influence of the intestinal microflora on mucin types was studied in the small intestine, caecum and colon of conventional (CV) rats as compared to germ-free (GF) rats. A colorimetric method was used on purified water-soluble mucin extracted from mucosal scrapings and contents. Variations occurred between the three anatomical sites both in the mucosas and intestinal contents of GF rats. In CV rats, the presence of the bacterial flora led to different effects depending on the intestinal site: in the small intestinal mucosa, neutral and sulphomucins values were higher whereas sialomucin was much lower. Conversely, sialomucin was higher in the caecal and colonic mucosas and contents whereas sulphated mucins were decreased significantly in caecal contents and caecal and colonic mucosas. These variations in the contents may reflect the bacterial mucolytic activity and the effect of bacterial metabolites on the mucosa.

Glucose, galactose, and glutamine metabolism in pig isolated enterocytes during development

ABSTRACT: In the pig, the gastrointestinal tract grows rapidly after birth and undergoes a short postnatal maturation. The objective of the present work was to assess the metabolic characteristics of the small intestinal mucosa during this period by investigating glucose, galactose, and glutamine metabolism in pig isolated enterocytes. Piglets were used immediately after birth or at various stages during suckling or postweaning. Fed animals were taken in a postabsorptive state. The jejunoileum was excised and perfused with an EDTA (5 mM)-containing buffer. The epithelial cell layer was further dissociated in the presence of hyaluronidase (0.01%). The resulting cell suspension (95% absorbing enterocytes; viability greater than 90%) was incubated with 14C-labeled substrates to measure 14CO2 production in parallel with substrate disappearance. The capacity to utilize glutamine was high and remained steady during the suckling period. Glucose utilization capacity was limited at birth and increased more than 3-fold during the first week of suckling. Such an increase was not observed in piglets kept unsuckled since birth. Galactose utilization capacity remained steady during the first week but afterward gradually disappeared. Lactate and pyruvate production through glycolysis was the major pathway accounting for glucose or galactose disappearance. A capacity for a net glucose production from galactose was evidenced during the first week of suckling. Thus, isolated newborn pig enterocytes exhibit specific and transient metabolic characteristics during the first postnatal week.

Colonic Mucin Discharge by a Cholinergic Agonist, Prostaglandins, and Peptide YY in the Isolated Vascularly Perfused Rat Colon

UNLABELLED The model of the isolated, vascularly perfused rat colon was assessed in the present study to investigate the nervous, hormonal, and local/paracrine pathways involved in colonic mucin secretion. A colonic loop was perfused via the superior mesenteric artery with a Krebs-Henseleit buffer containing 25% washed bovine erythrocytes at a rate of 2.5 ml/min. After a 10-min control period, each compound to be tested was infused intra-arterially for 30 min. Tissue samples from the proximal and midsegments of the perfused rat colon were then fixed and stained for mucus cell count. Intra-arterial administration of bethanechol evoked a concentration-dependent decrease in the number of stained mucus cells per crypt section over the range 2 x 10(-6) to 2 x 10(-4) M: 16.6 +/- 1.4 stained mucus cells per crypt in the midportion of the perfused rat colon (n = 5) with bethanechol 2 x 10(-4) M versus 28.8 +/- 1.5 for controls (n = 6). After infusion of 1.25 and 2.5 microM 16,16-dimethyl prostaglandin E2 (dmPGE2), the number of stained mucus cells per crypt section was significantly reduced: 21.6 +/- 0.6 (n = 6) and 20.6 +/- 1.4 (n = 7), respectively. An increase in the number of cavitated mucus cells was also observed (22.1 +/- 6.7 and 38.5 +/- 4.1% of cavitated mucus cells in the midsegment of the perfused rat colon with 1.25 and 2.5 microM dmPGE2, respectively, vs. 12.3 +/- 4.1% for controls). In contrast, prostaglandin F2alpha did not significantly affect mucus discharge from colonic cells. Peptide YY (10(-10), 10(-9) and 10(-8) M) induced a dose-dependent increase in the percentage of cavitated mucus cells (16.7 +/- 2.8, 23.1 +/- 4.2, and 31.2 +/- 3.4% of cavitated mucus cells in the midsegment, respectively). The proximal and midsegments of the perfused rat colon were equally sensitive to each secretagogue. CONCLUSION In the isolated, vascularly perfused rat colon, mucus cells strongly respond to the well-known mucin secretagogues, bethanechol and dmPGE2. This approach has already led to the identification of a novel stimulant of mucin secretion: peptide YY. Our ex vivo model, in which goblet cells are submitted to well-defined luminal and blood-borne stimuli is, therefore, reliable to investigate the nervous, hormonal, and local/paracrine pathways involved in the colonic mucin secretion.

Variations in digestive physiology of rats after short duration flights aboard the US space shuttle.

The purpose of this work was to assess the influence of microgravity on several endogenous and microbial parameters of digestive physiology. On the occasion of two Spacelab Life Sciences missions, SLS-1 (a 9-day space flight) and SLS-2 (a 14-day space flight), Sprague-Dawley rats flown aboard the US space shuttle were compared to age-matched ground-based controls. In both flights, exposure to microgravity modified cecal fermentation: concentration and profile of short-chain fatty acids were altered, whereas urea and ammonia remained unchanged. Only in SLS-1 was there an induction of intestinal glutathione-S-transferase. Additional analyses in SLS-2 showed a decrease of hepatic CYP450 and of colonic goblet cells containing neutral mucin. After a postflight recovery period equal to the mission length, only modifications of the hepatic and intestinal xenobiotic metabolizing enzymes still persisted. These findings should help to predict the alterations of digestive physiology and detoxification potential likely to occur in astronauts. Their possible influence on health is discussed.

Differential influence of butyrate concentration on proximal and distal colonic mucosa in rats born germ-free and associated with a strain of Clostridium paraputrificum.

In vivo influence of butyrate in colonic mucosa was studied using a model of gnotobiotic rats monoassociated with a Clostridium paraputrificum. Rats were fed a diet containing increasing amounts of non-digestible carbohydrates, the fermentation of which led to modulated amounts of butyrate in the large intestine. In the proximal colon, the increase in the butyrate concentration alters crypt depth and the number of mucus-containing cells; the increase in butyrate was highly correlated with the number of neutral-mucin-containing cells. Conversely, in the distal colon, no relation was found between the increase in butyrate concentration and crypt depth or number of mucin-containing cells. In both the proximal and distal colon, the mitotic index remained unchanged. In conclusion, in vivo production of physiological quantities of butyrate had a trophic effect on proximal colonic mucosa, but did not influence the distal epithelium.

Effects of ingestion of a green seaweed, Ulva lactuca, upon caecal and colonic mucosas in the germ-free rat and in the heteroxenic rat harbouring a human bacterial flora

Effect of ingestion of green seaweed, Ulva lactuca, (70 g kg−1) during a 6-week period on caecal and colonic mucosas was studied in germ-free (GF) rats and in heteroxenic (HE) rats harbouring a human bacterial flora (GF rats associated with a human flora). The pH and sulphide concentration of the caecal contents, crypt morphometry, mitotic index and mucin types in the caecal and distal colonic mucosas were determined. In the GF caecum, Ulva strongly increased crypt depth and mucin-containing cells irrespective of the mucin type studied (neutral, acidic or sulphated) compared to the control diet but had no significant effect on mitotic index. The crypt depth and mucin-containing cells in the caecum were higher in HE than in GF control rats. They were slightly but significantly increased by Ulva. In the distal colon mucosa of GF rats, Ulva decreased crypt depth and cell number as well as sulphomucin-containing cells. Conversely, in the HE rats, it increased crypt depth and reduced the number of neutral mucin-containing cells. These results show that Ulva lactuca exerts an intrinsic effect on mucosal morphometry and on mucin biosynthesis in GF rats. No pathological alteration was observed in the mucosas and no significant modification of the mitotic index or sulphide production was observed in HE rats. © 1999 Society of Chemical Industry

Epithelial cell migration on small intestinal villi in the neonatal rat. Comparison between [3H] thymidine and cytoplasmic labelling after Pu-citrate ingestion

This study compares, in 2‐d‐old rats, the migration rates of epithelial cells on villi of the small intestine, using two labelling methods: a single [3H] thymidine injection; and cytoplasmic labelling by a single ingestion of Pu‐citrate. Histoautoradiography shoed negligible diffusion of Pu after the initial retention, which was mostly confined to the epithelial cells of the villi. However, after sloughing of labelled cells in the intestinal lumen, Pu was reabsorbed by the distal epithelial cells. In segments in which Pu reabsorption was negligible, the migration rates of Pu‐ and 3H‐labelled cells were very close. These rates, expressed in micrometers, were almost constant along the length of the villus, and the Pu and 3H labelling edges reached the top of the villi in about 5 and 7 d, respectively.