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F Raul

Publications and source records attributed to F Raul.

At least 73 records · Page 4Linked to original sources
PubMed1990

[Different expression of the mRNA detected by the cDNA for fetal rat lactase in the jejunum and colon].

To study the genetical expression of lactase-phlorizin hydrolase in the jejunum and colon of developing rats we cloned the corresponding cDNA in a cDNA library constructed from the intestinal RNA of fetal rats. The structure of this 6.1 kb-long cDNA was similar to that of the cDNA of adult rabbits and humans, indicating that the enzyme was synthesized as a precursor organized into repeated homologous domains. The mRNA for lactase-phlorizin hydrolase accumulated at a constant level throughout the development in the jejunum despite the decline in lactase activity occurring at weaning. In the colon, the cDNA for lactase-phlorizin hydrolase hybridized to a transcript that was similar in size to the jejunal mRNA. This mRNA was transiently found during the first week after birth. Its rate of accumulation defined the level of lactase activity measured at this stage. We conclude that the expression of lactase-phlorizin hydrolase during the development is essentially regulated at the post-transcriptional level in the jejunum, in contrast to the colon where it is regulated at the pretranslational level.

Animals↗
PubMed1990

Comparative expression of the mRNA for three intestinal hydrolases during postnatal development in the rat.

The distribution of the mRNA for intestinal aminopeptidase-N, lactase-phlorizin hydrolase and sucrase-isomaltase was compared during rat postnatal development as well as along the longitudinal axis of the intestinal tract including small-intestine and colon. We found out that each mRNA exhibited a specific pattern of accumulation, suggesting proper regulation steps for the expression of the corresponding digestive enzymes.

Aminopeptidases↗
PubMed1989

Discrepancy between the intestinal lactase enzymatic activity and mRNA accumulation in sucklings and adults. Effect of starvation and thyroxine treatment.

The accumulation profile of intestinal lactase mRNA was investigated in suckling and adult rats and pigs. We found no correlation between the lactase enzymatic activity and the accumulation of the messenger at both developmental stages. Modulation of lactase activity by starvation or thyroxine treatment had no effect on lactase mRNA accumulation in the rat intestine. These results confirm that thyroxine modulates lactase expression essentially at the post-transcriptional level.

Age Factors↗
PubMed1989

Age influence on sucrose hydrolysis and on monosaccharide absorption along the small intestine of rat.

The consequences of aging on the hydrolysis and absorption of hexoses was assessed in vitro using everted intestinal segments. Glucose and fructose were given either as a mixture of free monosaccharides or as a disaccharide solution (sucrose). The jejuno-ileum of 3- and 24-month-old rats was everted and divided into four equal segments. For each segment, the mucosal medium contained either sucrose (140 mM) or an equimolar mixture of glucose and fructose (70 mM). Monosaccharide concentrations in the mucosal ans serosal media were measured after 1 h of incubation at 37 degrees C. In the young adult, glucose absorption was enhanced when given as sucrose. In contrast, in the aged rat, free glucose or glucose released from sucrose hydrolysis were similarly absorbed. Independently of age, fructose was better absorbed when provided in a mixture of free monosaccharides. The intestinal segments (and especially the ileum), of the aged animals exhibited higher abilities to hydrolyse sucrose and to absorb monosaccharides indicating a normal or increased intestinal hydrolytic activity and absorptive capacity for dietary sugars.

Aging↗
PubMed1989

Perinatal expression of brush-border hydrolases in rat colon: hormonal and tissue regulations.

The evolution pattern of brush-border digestive hydrolases and their hormonal regulation were studied in the proximal colon of newborn rats. The potentiality of the colon to express a small intestinal enzymatic pattern was also examined in associations made up of colonic endoderm and small intestinal mesenchyme, developed as either intracelomic grafts in 3-day-old chick embryos or as intrarenal grafts in adult rats. A transient increase of lactase- and aminopeptidase-specific activities occurred in the colon from the 19th day of gestation to 14 days after birth, but sucrase activity could never be detected. Immunocytochemical studies with antibodies specific for rat lactase, aminopeptidase, and sucrase confirmed these results. However, the levels of hydrolase activities were lower in the colon than in the jejunum at the same age. Thyroxine or hydrocortisone treatment during the first 4 days postpartum decreased lactase activity by 70 and 30%, respectively, but did not affect aminopeptidase activity. A slight but significant induction of sucrase activity was obtained with both hormones. In contrast, in the jejunum, only thyroxine decreased lactase activity with a lesser effect (30%), but both hormones increased aminopeptidase activity and induced the marked well-known appearance of sucrase activity. The fetal small intestinal mesenchyme was not able to induce the colonic endoderm to achieve a small intestinal-like differentiation. But the exposure of the developed hybrid intestines to glucocorticoids in organ culture allowed expression of sucrase in one-third of the cases. These results demonstrate the presence of brush-border hydrolases in the proximal colon of newborn rats, normally expressed in the small intestine, but never in the adult colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

The gene for intestinal sucrase-isomaltase as member of a gene family.

The synthetic oligonucleotide MF59, derived from the rabbit sucrase-isomaltase cDNA sequence, hybridizes to two classes of mRNA in the rat and pig intestinal epithelium as well as to various restriction fragments within the human genome. These results strongly support the hypothesis that the sucrase-isomaltase gene belongs to a gene family. The cloning of a human cosmid containing such a sequence similar to MF59 has allowed us to identify a new member of this gene family which detects a single 6.5 Kb intestinal mRNA in the adult pig.

Amino Acid Sequence↗
PubMed1988

Adaptation of intestinal enzymes to seasonal and dietary changes in a hibernator: the European hamster (Cricetus cricetus).

Effects of diet, hibernation and seasonal variations on hydrolase activities were determined in mucosa and purified brush border membranes of the small intestine of European hamsters. Wild hamsters captured in April and fed for several weeks with an equilibrated laboratory chow (20% protein, 50% carbohydrates) exhibited a rise in disaccharidase activities (sucrase, isomaltase, lactase) but no changes in aminopeptidase N activity. During deep hibernation, in contrast to sucrase and isomaltase activities which showed only minor changes, lactase activity was significantly enhanced along the jejunoileum, and aminopeptidase N activity was maximum in the ileum. After a short period (48 h) of wakefulness and feeding following 10 days of starvation during the hibernation period, the activities of the disaccharidases and of aminopeptidase N returned to values measured in active animals. In contrast to the nutritional state, which has an important impact on the activities of intestinal enzymes, season has little effect on the intestine of the active animal under a controlled environment. The pattern of enzyme activities which occurs along the small intestine in the hibernating animal may be a prerequisite for optimum digestion during the short phases of waking during the hibernation period of the European hamster.

Adaptation, Physiological↗
PubMed1988

Age related increase of brush border enzyme activities along the small intestine.

Intestinal morphology and brush border hydrolase activities were determined along the small intestine of young adult (three months, n = 10), mature (12 months, n = 10), and senescent (29 months, n = 15) rats. The intestinal segments of the senescent rats contained higher mucosal mass and protein content (p less than 0.05) compared with the young and mature animals. A significant reduction of villus height and crypt depth (p less than 0.05) was found in the proximal intestine during aging. A 35% increase in villus height (p less than 0.05) without changes in crypt depth, was observed in the distal ileum in senescent rats. The activities of sucrase and isomaltase were significantly increased during aging in the duodenum and jejunum (p less than 0.05). Lactase and aminopeptidase activities which showed only minor changes between young and mature animals were significantly enhanced in senescent animals (p less than 0.05) with aminopeptidase exhibiting a three-fold increase in activity in the proximal ileum. The results when combined with those of previous studies suggest that in the aged animal, the increased level of intestinal hydrolase activities may be the consequence of prolonged cellular maturation along the villi in the proximal intestine, and of adaptation to increased concentrations of intraluminal substrates in the distal intestine.

Aging↗
PubMed1988

Effects of a high-protein, low-carbohydrate diet on degradation of sucrase-isomaltase in rat jejunoileum.

During the degradation of intestinal sucrase-isomaltase by pancreatic proteinases, degradation of sucrase-active site precedes that of the isomaltase-active site in rats. In the present paper, we demonstrate that the extent of degradation of sucrase-isomaltase is altered by dietary manipulation in vivo. Adult rats were starved for 24 h and received either a standard diet (20 cal% protein, 55% carbohydrate) or an isocaloric high-protein, low-carbohydrate diet (70 cal% protein, 5% carbohydrate). Animals were killed 15 h after the refeeding. In rats fed a high-protein, low-carbohydrate diet, luminal trypsin activity was three times higher than controls, and sucrase activity in proximal ileum was significantly lower (P less than 0.001) than controls, whereas isomaltase activity was similar in both groups. In proximal jejunum, luminal trypsin activity was remarkably lower (P less than 0.01) than in proximal ileum in both groups; sucrase and isomaltase activity was similar in both groups. Crossed immunoelectrophoresis demonstrated that a degradation product of sucrase-isomaltase, i.e., isomaltase monomer, was present in a larger amount in rats fed a high-protein, low-carbohydrate diet. In rats with bypassed pancreatic ducts, the amount of this degradation product was decreased and effect of a high-protein, low-carbohydrate diet was abolished. Experiments with a sequential isolation of epithelial cells of proximal ileum revealed that sucrase activity was decreased along the entire height of the villus in animals fed a high-protein, low-carbohydrate diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Short-term effect of a high-protein/low-carbohydrate diet on aminopeptidase in adult rat jejunoileum. Site of aminopeptidase response.

The short-term effects of high-protein/low-carbohydrate diet on aminopeptidase N activity were studied in the brush-border membranes of proximal jejunum and proximal ileum of adult rats. The animals were starved overnight and re-fed for 15 h either with a standard diet (20% protein, 55% carbohydrate, in terms of energy content) or with a high-protein/low-carbohydrate diet of equal energy content (70% protein, 5% carbohydrate). All rats consumed similar amounts of diet, and measurements were made 15 h after initiation of re-feeding. In the proximal jejunum a slight increase in aminopeptidase activity was observed after the high-protein intake. In contrast, considerable stimulation (52%) of the enzyme specific activity was obtained in the proximal ileum. This increase in ileal aminopeptidase activity was more prominent in the mature cells of the upper villus. To determine if the increase of aminopeptidase activity was due to an increased amount of enzyme protein, rocket immunoelectrophoresis was performed with detergent-solubilized brush-border protein from ileum on agarose gels containing anti-(rat brush-border) antiserum. When the same amount of enzyme activity was loaded on the gels, the peaks of immunoprecipitate for aminopeptidase were similar for animals fed on a standard or a high-protein diet. When the same amount of protein was loaded, the peak of immunoprecipitate for aminopeptidase was higher (81%) after a high-protein diet. These results showed that the high protein intake evoked an increase in aminopeptidase activity, with a concomitant increase in the amount of immunoreactive protein.

Aminopeptidases↗
PubMed1986

Longitudinal distribution of brush border hydrolases and morphological maturation in the intestine of the preterm infant.

The morphological maturation and the distribution of brush border hydrolase activities were studied in the small intestine and the colon in newborn babies of 28-38 weeks gestational age. Lactase and sucrase activities were higher at term with maximal activity in the proximal intestine. In contrast, aminopeptidase and glucoamylase exhibited maximum activity in the distal part of the small bowel. Glucoamylase activity was already significant in the small intestine and in the colon of the preterm newborn. Sucrase activity present in the proximal colon of the preterm dropped to a negligible amount at term, whereas aminopeptidase activity increased, reaching values found in the small intestine. The enzymic changes occurring in the intestinal tract were related to the morphological maturation of the mucosa from fetal to adult type during late gestation. Accelerated morphological and functional maturation was observed in one preterm infant nourished intravenously for 12 days, these processes being independent of the presence of nutrients in the intestine. At term, the distal part of the intestine seems to have increased digestive capacities for peptides and polysaccharides. We present evidence that full-term, and to a lesser extent preterm infants are able to hydrolyse glucose polymers.

Aminopeptidases↗
PubMed1986

Effect of intravenous and intragastric fat infusion on intestinal brush border enzyme activities in rats.

Intralipid was given to adult rats for 4 days either by intragastric or intravenous infusion. The villus height, protein content and the levels of sucrase, lactase and aminopeptidase activities were determined in the jejunum. The results were compared to values found in control rats fed orally with an equilibrated isocaloric diet. Intragastric or intravenous infusion of Intralipid caused a 50% reduction in the protein content of the brush border membrane, a significant drop of the specific (expressed per milligram protein) and segmental (expressed per centimeter intestinal length) activities of the disaccharidases, the maintenance of aminopeptidase activity and the lengthening of the villi in the jejunum. The major loss in disaccharidase activities was obtained when fat was given intravenously. Arguments favoring a hormone-mediated effect of the infused lipids on the intestinal function are presented and discussed.

Aminopeptidases↗
PubMed1986

Modulation by thyroxine of the amount of lactase protein in the jejunum of adult rats.

Adult rats starved for 48 h received a daily injection of thyroxine over a 3-day period before they were killed. When compared to nourished animals, starvation provoked a 4- to 5-fold increase in immunoreactive lactase protein, which paralleled a similar stimulation of lactase activity in the brush border membranes of the proximal jejunum. Exogenous thyroxine completely inhibited the starvation-induced increase in immunoreactive lactase protein in both the intracellular and the brush border membranes.

Animals↗
PubMed1986

Small-intestinal and colonic changes after biliopancreatic bypass for morbid obesity.

Morphologic and functional adaptations of the functioning intestine were evaluated in 41 patients before and after biliopancreatic bypass for morbid obesity. This surgical procedure diverts pancreatobiliary secretions via the duodenum and the jejunum into the colon, the remaining small intestine being anastomosed to the stomach after antrectomy. In the proximal ileum there was an 80% increase of the height of villi; the specific activities of maltase, sucrase, and aminopeptidase in brush border membranes remained unaffected, and that of lactase tended to decrease. In the distal ileum villi heights increased only by 58%, and disaccharidase activities (except for maltase) were slightly enhanced. In the colon the mucosa displayed, in some patients, focal appearance of true villi, and brush border enzyme activities increased concomitantly. We conclude that biliopancreatic bypass induces an adaptation of all intestinal segments of the functioning intestine; this adaptation tends to compensate for the shortening of the gut continuity.

Adult↗
PubMed1986

Improved purification of rat intestinal lactase.

A rapid and improved method to obtain purified lactase from rat intestine is described. The purification procedure involved only two chromatographic steps. The degree of purification was far above (500 fold) the values reached with classical methods. Rabbit antisera raised to the purified lactase were characterized using conventional immunological techniques. The specificity of the lactase antibodies was confirmed by the lack of interference on maltase, aminopeptidase and alkaline phosphatase activities measured after papain extraction of the membrane proteins.

Animals↗