Search PubMed⌕ Search

Biomedical subjects

Y Dupuis

Publications and source records attributed to Y Dupuis.

At least 37 records · Page 2Linked to original sources
PubMed1988

[Differential phosphorylation of the 3 forms of alkaline phosphatase of the small intestine of adult rats].

Semi-purified preparations were obtained from duodenal, jejunal or ileal mucosa containing one of the three alkaline phosphatase forms. The Mr of the isoenzymes were for F1 120, F2 150, F3 180 kDa. F1 was the only species found in the ileum; F2 was duodenal but mainly jejunal; F3 was found mainly in duodenum. These enzymes forms were the only phosphorylable proteins in these preparations. Following treatment with denaturing agents they were separated on gel electrophoresis into monomers F': F'1 65, F'2 65 and 90, F'3 90 kDa. Thus F2 could be an heterodimer. All were far more phosphorylated from ATP than from inorganic phosphate. As compared with F1, F3 was relatively more sensitive to ATP and less sensitive to inorganic phosphate.

Alkaline Phosphatase↗
PubMed1987

Phosphorylable proteins and alkaline phosphatase of brush border membranes from different parts of the rat small intestine.

1. The distribution along the small intestine of phosphorylable proteins from the brush border has been studied by gel electrophoresis. 2. Four proteins, with apparent Mr of 190, 160, 140 and 120 kDa were distributed unequally along the gut, which incorporated 32P from gamma 32P (ATP) to different degrees. 3. Alkaline phosphatase activity has been shown to follow the same distribution. 4. Under denaturing conditions 90, 85 and 65 kDa proteins were observed, whilst the proteins of 190, 160, 140 and 120 kDa had disappeared. 5. All these proteins, with the exception of the 190 kDa protein, had also been labelled with 32Pi. Furthermore, a difference in the phosphorylation of the 65 kDa and the 90-85 kDa proteins was observed. 6. The 65 kDa protein like commercial calf alkaline phosphatase had a ratio of phosphorylation from ATP to phosphorylation from Pi less than the 90 and 85 kDa proteins. 7. Mg2+ (2.5-10 mM) decreased phosphorylation of only the 65 kDa protein whilst beta-glycerophosphate inhibited phosphorylation of all forms of alkaline phosphatase. 8. Incorporation of gamma 32P (ATP) into the proteins was enhanced in the presence of 5 mM theophylline or EDTA. 9. The nature of the phosphorylation of these different proteins is discussed.

Adenosine Triphosphate↗
PubMed1987

Variations of intestinal calcium absorption in adult frogs (Rana esculenta). Effect of lysine.

Intestinal calcium absorption was investigated in an adult frog (Rana esculenta) by injecting a CaCl2 solution containing 45Ca into the lumen. The 45Ca absorption coefficient in the proximal loop was higher than in the distal loop, only when the CaCl2 solution was left for 4 h. This coefficient increased both in the proximal and distal loops when a 4-h treatment was substituted for a 1-h treatment. The coefficient increased in the whole intestine during the first 2 h of treatment (1 h: 21%; 2 h: 55%) and remained stable afterwards in our experimental conditions. The intestinal calcium absorption increase occurred early in the presence of L-lysine (100 mM), since the coefficient already reached its maximum value (52%) after a 1-h treatment.

Animals↗
PubMed1987

[Action of bivalent cations on the alkaline phosphatase activity of intestinal microvilli. Influence of pH and substrate].

At alkaline or neutral pH and with PNPP or ATP as substrates, the effect of cations on alkaline phosphatase of jejunal microvilli was shown to differ, i.e. Mg++ had an activating effect at high concentrations, Zn++ slightly inhibiting, Ca++ and Co++ were inactive at all concentrations. At neutral pH with PNPP as a substrate, Mg++ and Co++ were active, Ca++ inactive and Zn++ slightly inhibiting at high concentrations. Using ATP as a substrate, all four cations were activators at all concentrations studied (0.2 to 5 mM). In the latter physiological conditions (pH and substrate), similar effects of the cations were observed with microvilli from other segments of rat small intestine.

Adenosine Triphosphate↗
PubMed1986

Phosphorylated proteins from anuran intestinal microvilli membranes--I. Relations with alkaline phosphatase.

The degree of phosphorylation of intestinal microvilli membrane proteins in an adult amphibian, Rana esculenta, was investigated under various experimental conditions. The microvilli protein phosphorylation rate rapidly increases during the first 4 min of incubation in a medium containing [gamma-32P]ATP. This increase is slower afterwards. Cyclic nucleotides (cyclic AMP, cyclic GMP) and sorbitol do not modify the microvilli protein phosphorylation rate. On the contrary, this phosphorylation rate significantly decreases in the presence of L-lysine, when its concentration in the incubation medium is greater than 25 mM. The time course of phosphorylation confirms the inhibitory effects of L-lysine (100 mM). The microvilli membrane proteins were distinguished by polyacrylamide gel electrophoresis. In heated samples, electrophoresis followed by an radioautograph systematically reveals the existence of a very phosphorylated protein with a mol. wt of 86 kDa. The phosphorylation of this protein is partially inhibited by L-lysine (100 mM). The very phosphorylated protein could be the monomer of alkaline phosphatase. The dimer (170 kDa) is visualized on electrophoretograms by its catalytic activity. In mammals, several authors have established a correlation between phosphorylation of the microvilli membrane proteins and the intensity of intestinal calcium absorption. Such a control is presently being investigated in adult Rana esculenta.

Alkaline Phosphatase↗
PubMed1985

Degenerative processes in skeletal muscle of Cd2+-treated rats and Cd2+ inhibition of mitochondrial Ca2+ transport.

In rat skeletal muscle, chronic exposure to 50 ppm Cd2+ in drinking water produced both ultrastructural and functional damage, which took place successively and increased gradually with duration of treatment. Ultrastructurally, the first effect was a regression of the sarcoplasmic reticulum, mitochondrial cristae, and glycogen granules. Then, the number of mitochondria diminished and a degeneration of myofilaments appeared. During the 9-month course of treatment, however, the terminal cisternae and the lateral saccules of sarcoplasmic reticulum remained, and the Z lines maintained their tight and rigorously parallel appearance. Functionally, the activities of two cytosolic Ca2+-sensitive enzymes (lactate dehydrogenase and malate dehydrogenase) decreased. Their partial restoration by EGTA and EDTA suggested the presence of inhibitory divalent cations in the cytosol of treated rats. Cd2+ also inhibited Ca2+ transport in mitochondria through the uncoupling of oxidative phosphorylation. Hence, an increase of Ca2+ concentration of the cytosol of Cd2+-treated rats, activating degradative enzymes such as phospholipases, proteases and phosphorylase b kinase, can be incriminated. A direct inhibitory action of Cd2+ on the activities of lactate dehydrogenase and malate dehydrogenase also occurred. Direct action of Cd2+ on certain other Ca2+-sensitive enzymes, thereby aggravating the indirect damage induced through increasing the Ca2+ concentration in cytosol, is hypothesized. In mitochondria, a Cd2+ activation of phospholipase A2 and/or a Ca2+-sensitive protease is a unique possibility, since Ca2+ accumulation was prevented by cytosolic Cd2+.

Administration, Oral↗
PubMed1985

Mitochondria alterations in Cd2+-treated rats: general regression of inner membrane cristae and electron transport impairment.

Young adult rats absorbed 50 p.p.m. Cd2+ added to drinking water. After 6 weeks, 3, 6 and 9 months of treatment, the ultrastructural condition of liver, kidney and muscle was observed by electron microscopy. The choice of these tissues was determined by their differences in the capacity to accumulate Cd2+: the liver is able to concentrate a considerable amount of metal, but redistributes it throughout the entire organism, while the kidney collects it in view of its elimination. Muscle contains the least Cd2+. A general regression in mitochondria cristae accompanied by a vesiculation and a fragmentation of endoplasmic reticulum appeared simultaneously in the three tissues, at as early as 6 weeks of treatment, and extended progressively with its continuation supporting evidence of a general attack of the intracellular membrane systems. Cd2+ stimulation of membrane-degrading enzymes such as phospholipases and proteases was suggested. A concomitant diminution in glycogen stores was noted. Active synthesis of neutral lipids, especially cholesterol esters, took place in liver mitochondria of treated rats in collaboration with rough endoplasmic reticulum, and progressively generated a multiplication of electron-transparent inclusions in cytoplasm. Isolated mitochondria from liver, kidney and muscle of Cd2+-treated rats maintained partial energy coupling, but displayed a rapid early fall in cytochrome oxidase followed by a partial restoration after 6 months of treatment, and a progressively slackening of succinate dehydrogenase. Isolated vesicles of liver mitochondria inner membrane of treated rats behaved as intact mitochondria, indicating changes inside the membrane itself. Addition in vitro of the metal ion to mitochondria and also to inner membrane vesicles isolated from control rats revealed that Cd2+ was able to stop completely succinate dehydrogenase, but was totally ineffective on cytochrome oxidase. Membrane fixation of Cd2+ on the flavoprotein or SH associated with succinate dehydrogenase is proposed. Considering the close parallelism of the extensive depression of microsomal NADPH cytochrome c reductase and the rapid fall in mitochondrial cytochrome oxidase, it is suggested that an indirect inhibition process occurs, through Cd2+-induced diminution of a constituent common to all cytochromes in the cell.

Animals↗
PubMed1984

Enterocyte microvillus can phosphorylate molecules which inhibit endogenous phosphorylation of its proteins.

D- and L-amino acids (arginine, lysine) and hydroxylated molecules (sorbitol, ethyl-ethanolamine), all of which increase the intestinal transfer of calcium, are phosphorylated by jejunal and ileal microvilli. All these molecules inhibit the endogenous phosphorylation of microvilli proteins. D- and L-valine, which are not phosphorylated in the same conditions, have no effect on the phosphorylation of microvilli proteins. These observations are in good agreement with the scheme previously proposed for the increase of calcium intestinal transfer by L-lysine: phosphorylation of L-lysine by mucous membrane may interfere with that of membrane proteins, the phosphorylation of which would lower the permeability to that cation. Autoradiographies of the electrophoretogram show that the principal phosphorylable microvilli proteins have the same electrophoretic properties as those of the dimer and the monomer of alkaline phosphatase from the same intestinal loci. The ability of the enzyme to be phosphorylated and its well-known transphosphorylating activity upon hydroxylated molecules suggest that it could, in different ways, affect intestinal transfer of calcium.

Amino Acids↗
PubMed1981

Effect of vitamin D deficiency on urinary excretion of connective tissue derivatives (hydroxyproline and glycosaminoglycans) in rats.

The urinary excretion of two connective tissue metabolites was studied in both control and vitamin D deficient rats. Hydroxyproline (HyPRO) excretion was determined after 2, 13 and 22 months (experiment I). It decreased with aging in animals receiving the control diet. On the contrary, this excretion increased as a function of age in vitamin D deficient animals. At the age of 22 months, HyPRO excretion was respectively 31 and 1708 micrograms a day in control and deficient animals. HyPRO and glycosaminoglycans (GAG) excretion was measured on a group of both control and vitamin D deficient rats at the age of 21 months (experiment II). These results confirm the high excretion of HyPRO in deficient animals. On the contrary, the GAG excretion was higher in control animals than in deficient ones, the mean excretion being respectively 412 and 234 micrograms a day.

Animals↗
PubMed1980

Calcium and monoamine regulation: role of vitamin D nutrition.

The mechanism of vitamin D participation in the processes of monoamine regulation was studied. Central and peripheral endogenous norepinephrine levels were compared in vitamin D deficient rats, in preventative vitamin D3 (1 IU/day) administered rats, and in lactose (20% of the diet) administered rats, lactose being known to increase intestinal absorption of calcium. Vitamin D deficiency resulted in a significant decrease in endogenous norepinephrine. The decrease was of variable magnitude according to the considered organs. The adrenal dopamine level was also less in vitamin D deficient rats than in rats given vitamin D in preventive treatment. However, it remained in the brain. In the absence of vitamin D dietary lactose restored blood calcium and endogenous norepinephrine levels in all the tissues, except in the liver. It appears that the decrease in norepinephrine storage in vitamin D deficient rats resulted from a lack of calcium rather than from the absence of vitamin D.

Adrenal Glands↗
PubMed1980

Notion of time factor in calcium absorption. Influence of sex, intestinal site and L-xylose in the mature rat.

The unidirectional influx of Ca (measured by in vitro methods) was similar along the intestine of the adult rat, from Treitz ligament to ileo-daecal valve. In in vivo ligated loop experiments, the rate of Ca absorption was similar during 30 min irrespective of site, sex and the presence of L-xylose in the Ca solution. On the contrary, these factors modified the quantity of Ca absorbed. After 30 min, absorption stopped in the male ileum whereas it continued (1) in the male jejunum; (2) in the ileum of the female, and (3) in the male ileum in the presence of xylose (absorption being proportional to xylose concentration). Thus, in the adult rat, the duration rather than the rate is the decisive factor in Ca uptake.

Animals↗
PubMed1979

[Effect of creatine and other phosphorylable amino compounds on the ileal absorption of Ca-45 in the rat].

Some carbohydrates which increase calcium absorption were phosphate acceptors. When administrated to adult Rat in ileal ligated loop, phosphorylable amino compounds such as creatine, L-aspartic and L-glutamic acids also increased calcium absorption; other effective compounds such as D- and L-lysine and D-alanine might be involved in reactions of phorphorylation. L-alanine, L- and D-valine and asparagine were ineffective in enhancing calcium absorption and were not phosphorylable. Injection of creatine into ileal loop induced the formation of its phosphorylated derivative. Absorption of the amino compound was not correlated with the fact that they were effective on calcium absorption.

Amino Acids↗
PubMed1978

The relations between intestinal alkaline phosphatase and carbohydrates with regard to calcium absorption.

The effect of carbohydrates on calcium absorption were studied in situ following the injection of a solution containing CaCl2 (+45Ca) into the ileal loop. The increase in Ca absorption was proportional to the concentration of carbohydrates injected and could be attributed to a progressive increase in the duration of absorption. In the ileal loop, sorbitol was much more effective than L-arabinose at equal concentrations in activating absorption. Such differences in the action of these carbohydrates were also observed in vitro with alkaline phosphatase extracted from the ileum. The transphosphorylating effect of the enzyme was much more pronounced in the case of sorbitol. Since the carbohydrate is a phosphate acceptor, it might influence the duration of absorption by reducing the inhibition exerted by phosphate upon a transfer mechanism which involves phosphatase, another possibility is that carbohydrate could postpone calcium insolubility through the formation of a phosphocarbohydrate complex.

Alkaline Phosphatase↗
PubMed1978

[Inhibition of calcium absorption and conditions of its prolongation in the presence of carbohydrate].

Experiments were performed on adult rats. In situ ligatured ileal loops were injected with a solution 10 mM CaCl2 containing 45Ca either with or without L-xylose in concentrations of 25, 50 or 100 mM L-xylose. The rats were sacrified at either 0.5, 1.0, 1.5 or 2.0 hours after injection; the entire loop including the wall and content was removed. After ashing, the radioactivity of the loop was measured and the absorption coefficient of 45Ca was calculated. After half an hour, the absorption coefficient of the four solutions had about the same value. At this time, the 45Ca absorption was completed with the solution containing only calcium. With the solution containing pentose, the 45Ca absorption continued for a longer period of time. The maximal values of absorption coefficient were obtained after one hour with 25 and 50 mM L-xylose and after one and a half hour with 100 mM L-xylose; similarly, the maximal values increased in proportion to the concentration of pentose in the solution. The contents of the loops were fractionated successively by centrifugation, ultracentrifugation and two membrane ultrafiltration. No differences were observed between the repartition of 40Ca or 45Ca, either with or without 50 mM L-xylose. The stop or the lengthening of the absorption could be attributed to a possible influence of carbohydrate upon the mechanism of calcium transfer. This question is discussed from the point of relationship between the carbohydrate and the intestinal alkaline phosphatase.

Absorption↗