Biomedical subjects

D Darmoul

Publications and source records attributed to D Darmoul.

21 records · Page 2Linked to original sources

PubMed1989

Reversible forskolin-induced impairment of sucrase-isomaltase mRNA levels, biosynthesis, and transport to the brush border membrane in Caco-2 cells.

Hybridization analysis of mRNA with a cDNA probe for human sucrase-isomaltase, pulse-chase experiments with L-[35S]-methionine followed by SDS-PAGE, and immunofluorescence detection of sucrase-isomaltase were used to analyze the level(s) at which forskolin interferes with the expression of the enzyme in Caco-2 cells in culture. Three effects are observed in Caco-2 cells treated with forskolin: 1) a marked decrease in the level of sucrase-isomaltase mRNA, 2) a marked decrease in the biosynthesis of the enzyme without any alteration of its stability, and 3) an almost total inhibition of its transport to the brush border membrane. All three effects are reversible when the drug is removed from the culture medium, though this reversibility is asynchronous: transport to the brush border membrane resumes after 24 h, sucrase-isomaltase mRNA levels are back to the normal after 5 days, whereas the biosynthesis of the enzyme, although increasing progressively, remains lower than in control cells, even 10 days after removal of the drug. The possibility that some effects are directly dependent on cAMP and others a consequence of changes in glucose metabolism is discussed.

Biological Transport↗

PubMed1988

Activity of 3 beta-hydroxysteroid dehydrogenase/isomerase in the fetal rat ovary.

3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) was examined in rat fetal ovaries. The enzymatic activity was determined by measuring the conversion of radiolabeled pregnenolone to progesterone. 3 beta-HSD, present in 14-day old fetal ovaries showed a regular increase in the course of development. Pretreatment with dcAMP for 48 h enhanced the apparent maximal velocity of the enzyme by about 5-fold without increase in the apparent Km. The increase in 3 beta-HSD activity was not due to the synthesis of pregnenolone observed after dcAMP pretreatment, but it was dependent on protein synthesis. The present results indicate that (1) 3 beta-HSD activity is present in fetal female gonads and the absence of steroid biosynthesis cannot be related to a defect in this enzyme (2) 3 beta-HSD activity is enhanced in the presence of dcAMP. The absence of gonadotropic receptors in the rat ovary before birth could explain the low level of the enzymatic activity measured in fetal ovaries.

3-Hydroxysteroid Dehydrogenases↗

PubMed1988

Effects of busulfan on ovarian folliculogenesis, steroidogenesis and anti-müllerian activity of rat neonates.

Pregnant rats were injected with busulfan on day 12 or 18 of gestation and the ovaries of 5- and 10-day-old neonates were compared with control ones in terms of 1) folliculogenesis, 2) production of estradiol-17 beta and estrone in vitro, 3) aromatase and 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) activities, and 4) anti-müllerian hormone. Injection of busulfan on day 12 led to a reduction in the number of germ cells and follicles, delayed the maturation of antral follicles and lowered estrogen production and aromatase and 3 beta-HSD activities. Anti-müllerian activity, present in ovaries from 10-day-old controls, was also depressed in busulfan-treated rats. No obvious effects were observed when busulfan was injected on day 18. Estrogen biosynthesis could be stimulated by gonadotropins at day 10 post-partum, indicating the presence of functional receptors to LH and/or FSH. These relationships are interpreted as indicating that ovarian cells retain their capacity to respond to hormonal challenge despite the morphological impairment induced by busulfan. Other factors which possibly interfere with ovarian activity in busulfan-treated rats are discussed.

3-Hydroxysteroid Dehydrogenases↗