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B Darcy-Vrillon

Publications and source records attributed to B Darcy-Vrillon.

27 records · Page 2Linked to original sources
PubMed1991

Arginine metabolism in rat enterocytes.

Rat enterocytes exposed to L-arginine in the absence of any other exogenous substrate were found to actively metabolize this cationic amino acid. L-Arginine was converted to L-citrulline either directly in a NADPH-sensitive manner thought to be coupled with the generation of NO, or indirectly through the sequence of reactions catalyzed by arginase and ornithine transcarbamylase. A large fraction of L-citrulline and L-ornithine generated from exogenous L-arginine was released in the incubation medium. The production of CO2 and (poly)amines from L-arginine occurred at rates 2 to 3 orders of magnitude lower than that characterizing the net uptake of the cationic amino acid, and this despite the fact that enterocytes were equipped to allow the interconversion of L-ornithine and L-glutamate. It is concluded that the oxidative catabolism of L-arginine in enterocytes is quantitatively negligible relative to its conversion to L-citrulline and L-ornithine.

Animals↗
PubMed1991

Exogenous and endogenous contributions to nitrogen fluxes in the digestive tract of pigs fed a casein diet. II. Ileal and faecal digestibilities and absorption of amino acids.

The present work aimed at quantifying nitrogen (N) and amino acid (AA) fluxes in the digestive tract of growing pigs fed a casein diet. In this paper we report on digesta passage at the terminal ileum, on apparent balances at the ileal and faecal levels, and on nutrients appearance in the portal vein. Digesta flow-rate at the terminal ileum was maximum between 6 and 12 h after the meal. About 10% of N and 5% of total AA ingested were recovered within 24 h. AA absorption started 30 min after the meal, and was measurable until 13 to 14 h. The total AA absorbed in 24 h accounted for 128% of the AA ingested. The AA composition of ileal digesta was very different from that of casein, closely resembling that of endogenous proteins. The AA composition of faeces was very close to that of bacterial proteins. The ileal digestibilities of AA, though lower than their faecal values, were very high. This was confirmed by AA absorption balances greater than 100%. These data suggest that casein was almost totally digested by the terminal ileum, and that endogenous AA were substantially reabsorbed. These findings are supported by data on endogenous N recycling (15N), reported in a following paper.

Amino Acids↗
PubMed1990

Exogenous and endogenous contribution to nitrogen fluxes in the digestive tract of pigs fed a casein diet. I. Contributions of nitrogen from the exocrine pancreatic secretion and the bile.

The aim of the present work was to study the endogenous contribution of the exocrine pancreatic and biliary secretions to the total endogenous nitrogen production in the pig. Three growing Large White pigs weighing 45 +/- 2.5 kg were fitted with permanent fistulae in the pancreatic duct, the bile duct and the duodenum. They were adapted to a semi-synthetic casein diet for 14 d before surgery. In a 7-d post-operative period and an 8-d experimental period, they were fed the same diet. Secretion rates were recorded, total nitrogen and TCA (trichloroacetic acid) insoluble nitrogen were determined in representative pancreatic juice and bile samples. Daily pancreatic juice and bile flow rates were very similar: 1,850 and 1,820 ml, respectively. The amount of endogenous total nitrogen secreted in the intestinal lumen was 3.6 g per day: 1.9 g N through pancreatic secretion and 1.7 g N through bile secretion. Pancreatic nitrogen increased after meal intake, whilst the kinetics of nitrogen production in the bile were not affected. Throughout the experiment, the mean percentage of TCA insoluble nitrogen was 78.1% in pancreatic juice and 72.3% in bile.

Animals↗
PubMed1989

Associative effects between two fibre sources on ileal and overall digestibilities of amino acids, energy and cell-wall components in growing pigs.

1. The associative effects of two fibre sources on ileal and overall digestibility of amino acids, energy and cell-wall components were studied by comparing wheat bran and soya-bean hulls in semi-purified diets given to growing pigs. 2. Castrated male pigs were prepared with ileo-rectal anastomosis to measure ileal digestibility, and overall digestibility was measured in pigs without anastomosis. 3. The three diets contained 190 g total fibre/kg dry matter (DM), derived from each fibre source or from a mixture of both fibre sources, so that each source provided half the amount of total fibre, and 170 g crude protein (nitrogen x 6.25)/kg DM by additions of casein. 4. The effects of fibre sources on the ileal digestibility of amino acids were additive for most amino acids; the only significant interactions were found for threonine, methionine and aspartic acid. In contrast with ileal digestibility, systematic negative interactions between fibre sources on overall digestibility of amino acids were noted. 5. There was no interaction between fibre sources in their effects on the digestibility of energy or of cell-wall components, irrespective of the site of digestion. The digestibility values were higher with soya-bean hulls than with wheat bran, especially at the faecal level. 6. It is concluded that ileal digestibility of amino acids provides a better estimate of amino acid availability, as ileal measurements allow a better discrimination between diets than faecal measurements when distinct fibre sources are used alone or in combination at the same total fibre content. In contrast, for energy, the measurement of digestibility at both faecal and ileal levels permits the estimation of the partition of available nutrients between the small and large intestines.

Amino Acids↗
PubMed1988

Affinity chromatography of naturally occurring folate derivatives.

In a previous report (1980, in Methods in Enzymology, Vol. 66, p. 686, Academic Press, New York) we described the preparation and use of purified milk folate-binding protein covalently linked to a Sepharose matrix. The present study was undertaken to test the capacity of this preparation to purify quantitatively folates from tissue extracts. In experiments that employed tissue extracts containing biologically synthesized [3H]folates, recovery of radioactivity from columns of the immobilized folate-binding protein (affinity columns) was consistently 90-95%. Folates eluted from the affinity column were practically pure. Anion-exchange chromatography of the purified fraction from rat liver extract yielded a number of uv-absorbing peaks which corresponded to the elution profile based on 3H counts, with respect to both the position and the area of the peaks. Treatment of the original extracts with folylpolyglutamate hydrolases resulted in the shift of these peaks to lower retention times, which corresponded to mono- or diglutamyl folate derivatives. Similar results were obtained with extracts from Lactobacillus casei. The purification of tissue folates by affinity chromatography allows determination of folate activity by direct physiochemical methods, which is particularly useful for analysis of folate composition in tissues.

Animals↗
PubMed1988

Analysis of sequential events in intestinal absorption of folylpolyglutamate.

Although it is clear that the intestinal absorption of folylpolyglutamates is associated with hydrolysis to monoglutamyl folate, the precise sequence and relative velocity of the events involved in this absorption are not fully elucidated. In the present study, we used biosynthetic, radiolabeled folylpolyglutamates purified by affinity chromatography to analyze the relationship of hydrolysis and transport in rat jejunal loops in vivo. Absorption was best described by a series of first-order processes: luminal hydrolysis to monoglutamyl folate followed by tissue uptake of the product. The rate of hydrolysis in vivo was twice as high as the rate of transport. The latter value was identical to that measured for folic acid administered separately. The relevance of this sequential model was confirmed by data obtained using inhibitors of the individual steps in absorption of "natural" folate. Heparin and sulfasalazine were both effective in decreasing absorption. The former affected hydrolysis solely, whereas the latter acted as a competitive inhibitor of transport of monoglutamyl folate. These studies confirm that hydrolysis is obligatory and that the product is subsequently taken up by a transport process, common to monoglutamyl folates, that is the rate-determining step in transepithelial absorption.

Animals↗
PubMed1985

Proteins in the digesta of the pig: amino acid composition of endogenous, bacterial and fecal fractions.

When studying digestibility, the respective parts of the exogenous, endogenous and bacterial fractions in the digesta or feces must be measured. The proportions of proteins from different sources may be estimated by comparing their amino acid composition with those of reference sources. This study describes the composition of endogenous and microbial proteins, i.e. meconium of piglet small intestine and colon, axenic piglet feces, bacteria isolated in the feces of pigs receiving a standard (cereal-based) or a purified diet, and pure culture of Escherichia coli. The composition of monoxenic piglet feces and of feces of conventional pigs fed the two types of diets have also been studied. The data on 17 amino acids were used to make overall comparisons of compositions, using the method of X2 distances and factorial correspondance analysis. The composition of exclusively endogenous products differed somewhat from that of samples (mucus, mucosa) usually considered as representative of that fraction. In conventional pigs, the major part of fecal proteins was composed of bacterial protein. Accurate estimation of these was difficult: diaminopimelic acid assay gave an estimate of 65% bacterial protein, while in the same experimental conditions X2 distance gave an estimate of 90%.

Amino Acids↗
PubMedDate not supplied

Non-starch polysaccharides extracted from seaweed can modulate intestinal absorption of glucose and insulin response in the pig.

We have investigated the possible effects of algal polysaccharides on postprandial blood glucose and insulin responses in an animal model, the pig. Three seaweed fibres of different viscosities, extracted from Palmaria palmata (PP), Eucheuma cottonii (EC), or Laminaria digitata (LD), were compared to purified cellulose (CEL). Blood glucose and plasma insulin levels were monitored and intestinal absorption quantified for 8 h following a high carbohydrate test-meal supplemented with 5% fibre. Digestive contents were also sampled, 5 h postprandial. As compared to CEL, PP had no effect on glucose and insulin responses. The latter decreased with EC, but glucose absorption balance was not modified. LD addition resulted in a dramatically reduced glucose absorption balance, accompanied by a higher amount of starch left in the small intestine. Among polysaccharides tested, only the highly viscous alginates could affect intestinal absorption of glucose and insulin response.

Animals↗