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C Dupuy

Publications and source records attributed to C Dupuy.

70 records · Page 4Linked to original sources
PubMed1989

NADPH-dependent H2O2 generation catalyzed by thyroid plasma membranes. Studies with electron scavengers.

Hog thyroid plasma membrane preparations containing a Ca2+-regulated NADPH-dependent H2O2-generating system were studied. The Ca2+-dependent reductase activities of ferricytochrome c, 2,6-dichloroindophenol, nitroblue tetrazolium, and potassium ferricyanide were tested and the effect of these scavengers on H2O2 formation, NADPH oxidation and O2 consumption were measured, with the following results. 1. Thyroid plasma membrane Ca2+-independent cytochrome c reduction was not catalyzed by the NADPH-dependent H2O2-generating system. This activity was superoxide-dismutase-insensitive. 2. Of the three other electron scavengers tested, only K3Fe(CN)6 was clearly, but partially reduced in a Ca2+-dependent manner. 3. Though the NADPH-dependent reduction of nitroblue tetrazolium was very low and superoxide-dismutase-insensitive, nitroblue tetrazolium inhibited O2 consumption, H2O2 formation and NADPH oxidation, indicating that nitroblue tetrazolium inhibits the H2O2-generating system. We conclude that the thyroid plasma membrane H2O2-generating system does not or liberate O2- and that Ca2+ controls the first step (NADPH oxidation) of the H2O2-generating system.

2,6-Dichloroindophenol↗
PubMed1988

Ca2+ regulation of thyroid NADPH-dependent H2O2 generation.

A thyroid particulate fraction contains an NADPH-dependent H2O2-generating enzyme which requires Ca2+ for activity. A Chaps solubilized extract of the thyroid particulate fraction partially purified by DEAE chromatography did not show a dependence on Ca2+ for activity. Preincubation of the particulate fraction with Ca2+ yielded a preparation insensitive to Ca2+. The non-particulate fraction obtained after incubation of the particles in the presence of Ca2+ was able to inhibit, in the presence of EGTA, the Ca2+-desensitized particulate fraction and the enzyme isolated on DEAE. It is concluded that the reversible Ca2+ activation of the NADPH-dependent H2O2 generation was modulated in porcine thyroid tissue by (a) calcium-releasable inhibitor protein(s).

Animals↗
PubMed1986

Solubilization and characteristics of the thyroid NADPH-dependent H2O2 generating system.

Solubilization of the thyroid particulate-associated NADPH-dependent H2O2 generating system has been tested with different detergents; (3-(3-cholamidopropyl)-dimethylammonio)1-propane sulfonate (CHAPS) was found to be the best of the six detergents tested. The ratio of H2O2 generation to NADPH oxidation was similar for CHAPS extract and native particulate material. CHAPS was also the only detergent able to preserve the Ca++-sensitivity of the NADPH oxidase. Solubilization of this enzyme allowed the determination of some of its characteristics: specificity for divalent cations, apparent Km for NADPH, optimum pH and sensitivity to SH- reagents.

Animals↗
PubMed1985

Acute effects of filipin on the plasmic, hepatic, and biliary cholesterol of the rat.

Twenty-one male Wistar rats, 13 weeks old, were fed ad libitum hyperlipidic diets (28% fats) loaded with cholesterol (1.2%) for 5 weeks. One group of 11 rats was fed saturated fats (diet group "S") and another group of 10 rats was fed polyunsaturated fats (diet group "PU"). On the day they were sacrificed 10 of the rats were injected intravenously with 1 mg of filipin. Contrary to the rats in diet group "PU," the rats in diet group "S" treated with filipin presented certain characteristics that were not found in the nontreated group: They provided evidence of biliary cholestasis accompanied by a decline in the level of secretion of bile salts and phospholipids into bile. The concentrations of both free and esterified cholesterol in plasma fell and the amount of (esterified) hepatic cholesterol rose, although there was no change due to the filipin in the amounts of hepatic phospholipids. Explanatory hypotheses for these phenomena were considered, first, at the site of plasma membranes where filipin binds selectively to the cholesterol in the membrane, causing a disruption which probably disturbs the absorbance of circulating lipoproteins, especially that of hepatocyte cells, particularly in diet group "PU." Second, the effects of filipin on subcellular membranes seem to disturb the secretion of lipids and lipoproteins into bile and plasma, especially in diet group "S." Last, at the intracellular level, filipin appears to have a blocking effect on the organelles involved in biliary lipid secretion. The activity of certain enzymes such as cholesterol esterase may also be blocked, particularly in diet group "S," which would explain the accumulation of esterified cholesterol in liver.

Alanine Transaminase↗
PubMed1984

Influence of acute injection of chloroquine on the biliary secretion of lipids and lysosomal enzyme on rats.

Phospholipids and cholesterol combine with a protein fraction (IgA and an acid polypeptide) in bile to form the bile lipoprotein complex. We wished to determine whether lysosomes participated only on IgA secretion or if their secretory role also involved the lipid components of the bile complex. This aspect was studied with a single acute injection of chloroquine, a lysosomotropic drug. The results show that a nonnegligible quantity of IgA travels through the lysosomes. In addition, phospholipid and cholesterol levels undergo a significant (P less than 0.05) decrease 1 hr after injection before increasing to normal levels. In contrast to the total inhibition of protein secretion (beta-glucuronidase, acid phosphatase), a transitory decrease of the secretion of bile lipids takes place that suggest secretory mechanisms involving organelles other than lysosomes.

Acid Phosphatase↗
PubMed1984

Genetically determined resistance to mouse hepatitis virus 3 is expressed in hematopoietic donor cells in radiation chimeras.

Differences in mouse hepatitis virus 3 (MHV3) sensitivity among mouse strains are mainly determined by H-2-related and -nonrelated genetic factors. Reciprocal chimerism was therefore established between two H-2a compatible pairs of strains that differ widely in their susceptibility to MHV3: a) A/J and B10.A, respectively resistant and highly susceptible; b) A/J and A/Sn, respectively resistant and semisusceptible. Chimeric mice were challenged with 100 LD50 of MHV3, 30 or 90 days after X-irradiation (900 R) and bone marrow reconstitution. Results showed that sensitivity of recipients was similar either to that of the recipient strain or to that of the donor strain when chimeric mice were tested 30 or 90 days, respectively, after reconstitution. In addition, no paralysis occurred in surviving animals. These data indicate, therefore, that resistance or susceptibility to MHV3 is expressed intrinsically in some population(s) of hematopoietic-derived cells, which is radioresistant and has a life span of more than 30 days and less than 90 days. Additional experiments showed that X-irradiated A/J recipients reconstituted with A/J bone-marrow cells were protected against MHV3 challenge with spleen cells, with a mixture of spleen cell populations or of adherent spleen cells and thymocytes originating from A/J donors. Transfer of protection to recipients by using similar cell populations provided by semisusceptible A/Sn donors required the administration of five times more cells. Results suggest that two complementary mechanisms are required to confer resistance to MHV3: a) a gene(s) for resistance that may operate at the level of macrophages, and b) cells capable of mounting an efficient immune response. The reduced efficiency of A/Sn spleen cells suggests that semisusceptibility to MHV3 may be related to partial quantitative or functional immune defect.

Animals↗
PubMed1978

Hepatitis B in children. II. Study of children born to chronic HBsAg carrier mothers.

A survey of 4,452 pregnant women taken to find hepatitis B surface antigen revealed 28 asymptomatic chronic carriers. At birth, 16 of 17 infants studied were negative for HBsAg, whereas anti-HBc was present in all patients at a titer similar to that of the mother. Twelve children were followed for 6 to 18 months. In four of them, HBsAg remained negative and anti-HBc titers progressively decreased and were undetectable when tested after the age of 6 months. In eight infants, HBsAg became positive after an average time of 48 days. Elimination of HBsAg occurred in seven infants; five of them had clinical and biological manifestations of mild hepatitis. Sequential determinations of total complement and C components in three patients of the latter group showed dperession of complement at the time of appearance of clinical manifestations. In the patient who became an HBsAg carrier as well as in three infants who remained HBsAg negative, no decrease in complement titers was observed. These results indicate that vertical transmission from carrier mothers can occur in a low prevalence area and that neonatally infected children are capable of active elimination of HBV.

Antibodies, Viral↗
PubMed1977

Complement studies in severe viral hepatitis of childhood.

Complement (C) and C components were studied in 18 children with severe viral hepatitis. Results were compared to similar determinations performed in 8 patients with toxic hepatitis related to the ingestion of Amanita Phalloïdes. Hemolytic activities and serum concentrations of C and C components were markedly decreased (less than 2 SD) in both groups of patients. Sequential determinations of C components showed different patterns according to the outcome: either a rapid return to normal in patients who healed or persistence of low levels in patients who died. Such a pattern was similar to that of the prothrombin time. In patients with viral hepatitis a rapid disappearance of C4 and C3 was observed following fresh plasma or fresh blood transfusion. In addition, C4 cleavage was shown in plasma of 8/8 patients. These data suggest that the complement depression observed in fulminant viral hepatitis is related to both consumption and deficient synthesis.

Child↗