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A Giraud

Publications and source records attributed to A Giraud.

At least 37 records · Page 2Linked to original sources
PubMed1996

The pregnant ovine endometrium constitutively expresses and secretes a highly stable bombesin-like peptide, which shares C-terminal sequence but differs structurally from gastrin-releasing peptide.

Previous studies have shown that a peptide closely related to gastrin releasing peptide (GRP) is expressed by the pregnant ovine endometrium throughout gestation, however its molecular form and the mode of its secretion have not been defined. We have partially purified the endometrial GRP-like peptide and characterised it chromatographically. In contrast to other tissues, the main molecular form of endometrial GRP is larger (6-8 kDa versus 1-3 kDa), and based on the increased hydrophobicity of its circulating form after reduction, contains at least one disulfide bond. Reduction and treatment with chaotropic agents showed that the protein is not a cleavage product of pro-GRP bound to a binding protein. Tryptic cleavage demonstrated that the C-terminus of the peptide is closely related to GRP18-27 suggesting that bioactivity is likely. The partially purified peptide remained intact after incubation in ovine plasma for 16 h indicating that it is extremely stable and consistent with an hormonal role during pregnancy. Quantification of peptide from monolayer cultures of ovine endometrial cells showed that the GRP-like peptide was secreted constitutively. These data show that a stable, GRP-like peptide, distinct from the known processing products of pre-pro-GRP is constitutively expressed by the gravid ovine endometrium. Since endometrial GRP has an intact bioactive C-terminus and is mitogenic for numerous tissues including the uterus, then it is likely to play an important regulatory role in ovine pregnancy.

Amino Acid Sequence↗
PubMed1996

Effectiveness and prognostic factors of success in 12 smoking cessation clinics in the hospitals of Assistance publique-Hôpitaux de Paris.

We evaluated whether the location of a smoking cessation clinic in a hospital enhances the success rate compared to that found in the literature, regardless of the type of treatment. We assessed the results and identified prognostic factors of success in 12 smoking cessation clinics situated in 12 hospitals of the Assistance publique-Hôpitaux de Paris (AP-HP). The clinics were included in the study after a call for participation. The response rate was 60%. The study design was prospective, multicentric and descriptive. The study lasted 9 months. Follow-up took place 3 and 6 months after the first visit. The definition of success was self-reported total abstinence from cigarette smoking during the month preceding the 6-month follow-up. Success rate was 27%, failures were 66%, and 7% were lost to follow-up. Prognostic factors of success were not related to the hospital setting. We conclude that for a number of structural reasons that we explain, according to this study, the location of smoking cessation clinics in hospitals does not enhance their success rate compared to that found in the literature.

Adult↗
PubMed1996

Conserved expression of intestinal trefoil factor in the human colonic adenoma-carcinoma sequence.

Human intestinal trefoil factor (ITF), a mucosa-associated trefoil peptide, has been implicated in maintenance of mucosal integrity and may denote commitment to goblet cell differentiation. We have quantitated and localized ITF expression in normal and neoplastic colons, determined the molecular forms present, and examined the relationships among ITF expression and mucin production and increasing dysplasia. Normal and neoplastic human colonic mucosa (n = 30) were extracted for quantitation by ITF radioimmunoassay and size determination by gel filtration and immunoblotting. Paraffin sections of normal bowel, hyperplastic polyps, adenomatous polyps, and adenocarcinoma were examined for ITF immunohistochemistry and mucin histochemistry. The predominant molecular species in both normal and neoplastic colon was a 7-kd monomer. Staining was localized to goblet and Paneth cells and the luminal surface in normal colon and in most adenomatous polyps but not hyperplastic polyps; this colocalized with periodic acid-Schiff histochemistry. ITF staining of undifferentiated cells was seen with increasing dysplasia, and Golgi region immunoreactivity was highly conserved in adenocarcinoma, independent of the presence of periodic acid-Schiff-positive mucin. ITF concentration in colonic extracts was 10 to 200 pmol/g. Levels in normal (88.1 +/- 15.1 pmol/g) and malignant (90.1 +/- 12.7 pmol/g) tissue were comparable. In carcinomas, there were significant associations among ITF expression and degree of differentiation and mucin presence. Loss of expression was associated with tumor necrosis and advanced Duke's stage. ITF is uniformly processed in normal and neoplastic colons. Goblet cell-derived ITF is associated with stainable mucin production. ITF synthesis by non-goblet colonocytes, however, is highly conserved in neoplastic differentiation.

Adenoma↗
PubMed1994

The number of oligosaccharides borne by porcine thyroglobulin is variable.

Purified porcine thyroglobulin (Tg) was fractionated on a concanavalin A-Sepharose 4B column by a step-wise elution with increasing concentrations of methyl alpha-mannoside (fraction A, 50 mM; B, 100 mM; C, 200 mM; D, 500 mM, and E, 1 M), and its fractional ratio was 12.8:28.6:26.4:19.7:12.4. These five fractions showed the same profile in polyacrylamide gel electrophoresis. The subfractions were analyzed for their relative contents in oligosaccharides of each structure type and for their monosaccharide contents. In fractions B, C, D, and E the former varied between 15-22% for triantennary complex-type, 47-60% for biantennary complex-type, and 22-30% for high mannose-type oligosaccharide. Fraction A showed a higher percentage of triantennary complex-type structures (36%) and a lower percentage of biantennary complex-type structures (17%). The monosaccharide numbers increased from fraction A to E: 85 to 135 mannose residues, 60 to 82 galactose residues, 84 to 115 N-acetyl glucosamine residues, and 22 to 28 sialic acid residues. After analysis of the number of mannose residues contained in the high mannose-type structures, it was possible to calculate the number of oligosaccharides borne by each Tg subfraction. This number was approximately the same for fractions A and B (22.4 and 21.7), then it increased from B to E (21.8 to 32.9). These results account for the separation obtained on the concanavalin A-Sepharose 4B column. Separation of the two first subfractions bearing the same number of oligosaccharides is certainly due to the higher number of high mannose-type structures in B. In conclusion, the studies reported here show that porcine Tg is heterogeneous, and mainly so in terms of total number of N-glycan structures.

Animals↗
PubMed1994

A peptide related to gastrin releasing peptide is synthesised and secreted by the ovine endometrium in early pregnancy.

We have previously shown that the peptide immunoreactivity related closely to the mitogen GRP is expressed by the pregnant ovine endometrium during the final third of pregnancy. In this study we have established that GRP is also expressed early in ovine pregnancy and have quantified the temporal changes in synthesis, storage and secretion of GRP in the peri- and post-attachment period. Secreted GRP peptide levels rise 10 fold just prior to implantation, while endometrial peptide and mRNA concentrations increase 4 and 13 fold respectively between day 17 and 20, immediately following attachment and corresponding to the onset of placentome development. The main molecular form of endometrial GRP has similar binding characteristics on RP-HPLC to GRP 18-27, but is larger. We conclude that a GRP-like peptide is expressed by the pregnant ovine endometrium from early in pregnancy until term, and that it is likely to play an important role in fetal or uterine maturation.

Animals↗
PubMed1993

Mammalian bombesin as a hormone in ovine pregnancy: ontogeny, origin, and molecular forms.

Mammalian gastrin-releasing peptides (GRP) are present in female reproductive tissues and stimulate uterine contraction and DNA synthesis in the endometrium. We set out to establish whether the GRP were likely to play a role in fetal development by measuring the fetal and maternal plasma concentrations in chronically cannulated fetal sheep from 115 days gestation to term (145 days) and for 18 days after parturition. Placental fluids and fetal urine were also obtained. In a separate series of animals, uterine, placental, and fetal gut and lung tissues were collected. Samples were extracted in acid and assayed by radioimmunoassay, and molecular forms were characterized by high-performance liquid chromatography. GRP were present in the decidua (> 10 pmol/g), as well as placental, uterine, lung, and gastrointestinal tissues (all < 6 pmol/g). Fetal and maternal plasma GRP were elevated compared with nonpregnant ewes, falling sharply after parturition. Placental fluids and urine also contained GRP (80-410 fmol/ml). The main molecular form in all tissues and fluids examined coeluted with porcine GRP-(18-27). GRP immunoreactivity was primarily localized to epithelial cells of the decidua. These data suggest that plasma GRP is probably derived from the decidua and may play a role as a circulating hormone in ovine fetal and uterine development.

Animals↗
PubMed1992

Effects of deglycosylation of human thyroperoxidase on its enzymatic activity and immunoreactivity.

Thyroid peroxidase (TPO) is a glycoprotein enzyme which catalyses the iodination of thyroglobulin and the coupling of iodinated tyrosines. Human TPO (hTPO) is the microsomal antigen recognized by the autoantibodies in the serum of patients with autoimmune thyroid disease. An active detergent-solubilized immunoaffinity-purified hTPO was deglycosylated, either by peptide N-glycosidase F (PNGase F) or by endo-beta-N-acetylglucosaminidase H (endo H), and the enzymatic activity and immunoreactivity of the native and deglycosylated forms were compared. Electrophoretic controls and affinoblotting with concanavalin A showed that deglycosylation was not total and that it was more pronounced with endo H than with PNGase F. The enzymatic activity of hTPO was inhibited by endo H deglycosylation, but not by PNGase F deglycosylation; this inhibition was not due to aggregation and/or insolubilization of the molecule subsequent to deglycosylation. Immunoreactivity was monitored by enzyme-linked immunosorbent assay (ELISA) with 13 mouse monoclonal antibodies, rabbit polyclonal antibodies and antibodies from serum of patients with Hashimoto's thyroiditis. In contrast with enzymatic activity, immunoreactivity was not modified or was slightly enhanced (with four monoclonal antibodies) by deglycosylation. The results indicate that strong, if not total, deglycosylation induces a modification of the tertiary structure of hTPO, which affects the enzymatic site but does not modify markedly the epitopes implicated in the recognition of the molecule by the antibodies tested.

Amidohydrolases↗
PubMed1992

How to induce physicians to engage in quality assurance activities in a university hospital: a policy.

This article reports on a 3-year quality assurance (QA) support activity in the Assistance Publique-Hôpitaux de Paris, a large university hospital system covering the Greater Paris area. This activity stressed the interprofessional and voluntary character of QA. As well as showing the traditional reservations that usually prevent physicians from embracing QA. French physicians have specific problems with the word "evaluation" that has for them greater monetary than scientific connotations. In addition, the above-mentioned reservations are aggravated by the background culture and career structure of university physicians in France. In spite of these initial difficulties the support programme succeeded in getting QA off the ground in 60 departments in 25 hospitals. The need for a well developed medical information system as an incentive for QA activities in AP is discussed.

France↗
PubMed1991

Effect of N-glycan removal on the enzymatic activity of porcine thyroid peroxidase.

Active porcine thyroid peroxidase (pTPO) has been purified either by deoxycholate extraction followed by immunoaffinity purification (pTPO A) or by trypsin/digitonin extraction followed by ion-exchange and gelfiltration chromatography (pTPO B); pTPO A appeared as a full-length molecule, while pTPO B appeared as peptide fragments. Purified pTPO were deglycosylated either by peptide N-glycosidase F (PNGase F) or by endo-beta-N-acetylglucosaminidase H (endo H) treatment. Electrophoretic controls and affinity blotting with concanavalin A indicated that deglycosylation was not total and that pTPO was more efficiently deglycosylated by endo H than by PNGase F. The enzymatic activity of pTPO A, checked by guaiacol and iodide oxidation, was inhibited by PNGase F and endo H deglycosylation, while that of pTPO B was not. After deglycosylation, the apparent Km of pTPO A for guaiacol and iodide increased, while the Vmax for both substrates decreased. The state of aggregation of pTPO A before and after deglycosylation was checked by sucrose density-gradient centrifugation. Results indicated that this inhibition was not due to a loss of pTPO A solubility. These observations suggest that deglycosylation induced a modification of the tertiary structure of pTPO A which affected the active-site domain of the enzyme.

Animals↗
PubMed1990

Inhibition of N-glycan processing affects iodide organification in porcine thyroid cells.

The N-glycan-processing inhibitors swainsonine (Sw) and deoxymannojirimycin (dMM) were used to study the influence of N-glycans on iodide organification in cultured porcine thyroid cells. Incubations with [125I]NaI were followed by determination of labeled trichloroacetic acid-insoluble material in culture media, follicular contents and cells. In controls, most of this material was in the follicular contents. With Sw and dMM, total acid-insoluble material was less than 10% of control. Iodide uptake was slightly inhibited and hydrogen peroxide release was not affected by inhibitors. Cell-surface thyroid peroxidase (TPO) activity, assayed by its ability to iodinate bovine serum albumin, was strongly inhibited. Pronase glycopeptide analysis indicated that with drugs the content in complex-type N-glycans was strongly decreased while that in hybrid or oligomannosidic type was increased. In conclusion, inhibition of N-glycan processing prevents iodide organification in cultured porcine thyroid cells by decreasing the recovery of cell-surface TPO activity.

1-Deoxynojirimycin↗
PubMed1990

Effects of inhibition of gastric secretion on antral gastrin and somatostatin gene expression in rats.

Antral gastrin and somatostatin mRNA concentrations were measured in rats during gastric neutralization produced either by resection of the acid-secreting portion of the stomach (fundectomy) or by omeprazole treatment. Fundectomy caused increases in gastrin mRNA concentrations to 570% of sham control after 4 days and to 650% after 28 days. Daily administration of omeprazole resulted in significant dose- and time-dependent increases in antral gastrin mRNA concentrations. Four-day treatment with omeprazole caused threefold increased gastrin mRNA. Antral somatostatin mRNA concentrations decreased significantly after fundectomy to 66% of sham control after 4 days and to 23% after 28 days. Omeprazole produced a more profound decrease in somatostatin mRNA to 22% of the vehicle control after 4 days. Antral beta-actin mRNA concentrations did not differ significantly between control and experimental animals. Transcription of gastrin mRNA in isolated antral mucosal nuclei, measured by a nuclear run on technique, was significantly increased after omeprazole treatment in vivo. Increases in plasma and antral gastrin concentrations in response to gastric neutralization were closely associated with increases in gastrin mRNA and were accompanied by reductions in somatostatin mRNA in the antrum. However, fundectomy produced relatively greater increases in gastrin mRNA and lesser reductions in somatostatin mRNA than observed after omeprazole pretreatment.

Amanitins↗
PubMed1990

Effects of deoxymannojirimycin and castanospermine on the polarized secretion of thyroglobulin.

In order to better explore a possible role of oligosaccharide structures in the polarized secretion of thyroglobulin (Tg), we labeled cultured porcine thyroid cells with L-[3,4,5-3H]leucine or D-[2-3H]mannose in the presence or absence of the following inhibitors of N-linked oligosaccharide processing: deoxymannojirimycin (dMM), an inhibitor of mannosidase I expected to give rise to high mannose units exclusively, thus abolishing the formation of lactosaminyl branches, and castanospermine (Cs), an inhibitor of glucosidases which is expected to produce glucosylated high mannose oligosaccharides. [3H]Leucine pulse-chase experiments were performed to study the rate of Tg secretion in the presence and absence of dMM (1 mM) or Cs (1.6 mM). After a 15-h chase period, dMM and Cs did not modify the relative proportions of released Tg (65% in the follicular content, 16% in the medium) and cellular Tg (19%). In contrast, Cs led to a lower rate of secretion in both secretory pathways (t1/2 increased from 42 min to 105 min in the apical pathway and from 108 min to 138 min in the basal pathway). After a long-term labeling (16 h) with [3H]leucine or [3H]mannose, drugs did not notably affect the relative proportions of labeled Tg in the different compartments (follicular content, medium, and cell). The structures of N-glycans borne by Tg, with and without drugs, were checked. After Tg immunoprecipitation, pronase-glycopeptides were fractionated on concanavalin A-Sepharose 4B. The glycopeptides tightly bound to the lectin were treated by endo-beta-N-acetylglucosaminidase H and oligosaccharides separated by HPLC. With dMM, complex-type glycans of Tg were totally replaced by high mannose-type glycans, Man8-9GlcNAc; Cs induced the accumulation of glucosylated high mannose-type structures, Glc3Man7-9GlcNAc and Glc2Man8-9GlcNAc, but the action of this inhibitor was not total. In conclusion the correct secretion of Tg does not require the presence of the sialyllactosaminyl structure; the presence of glucose residues on high mannose-type structures lowers the rate of exocytosis.

1-Deoxynojirimycin↗
PubMed1989

Projections of neurons with neuromedin U-like immunoreactivity in the small intestine of the guinea-pig.

Neuromedin U immunoreactivity was located histochemically in the guinea-pig small intestine. Projections of immunoreactive neurons were determined by analysing patterns of degeneration following nerve lesions. The co-localization of neuromedin U immunoreactivity with immunoreactivity for substance P, neuropeptide Y, vasoactive intestinal peptide and calbindin was also investigated. Neuromedin U immunoreactivity was found in nerve cells in the myenteric and submucous plexuses and in nerve fibres in these ganglionated plexuses, around submucous arterioles and in the mucosa. Reactive fibres did not supply the muscle layers. Most reactive nerve cells in the myenteric ganglia had Dogiel type-II morphology and in many there was co-localization of calbindin, although some Dogiel type-II neuromedin U neurons were calbindin negative. Lesion studies suggest that these myenteric neurons project circumferentially to local myenteric ganglia. Projections from myenteric neurons also run anally in the myenteric plexus, while other projections extend to submucous ganglia, and still further projections run from the intestine to provide terminals in the coeliac ganglia. In the submucous ganglia neuromedin U was co-localized in three populations of nerve cells: (i) those with vasoactive intestinal peptide immunoreactivity, (ii) neurons containing neuropeptide Y, and (iii) neurons containing substance P. Each of these populations sends nerve fibres to the mucosa. Neuromedin U immunoreactivity is thus located in a variety of neurons serving different functions in the intestine and therefore probably does not have a single role in intestinal physiology.

Animals↗
PubMed1989

Effects of tunicamycin and N-linked oligosaccharide-processing inhibitors on the morphology of cultured porcine thyroid cells.

The effects of tunicamycin and of N-linked oligosaccharide-processing inhibitors on the ability of cultured porcine thyroid cells to adhere to a plastic support and to form organized structures were examined. The culture conditions used allowed the epithelial cells to adhere to the support and to form either a monolayer (no thyrotropin) or follicles (thyrotropin 4 mU/ml). The follicles thus obtained tend to disappear after 8 to 9 days, giving rise to a monolayer. Tunicamycin prevented both cell adhesion to the support and formation of organized structures. Swainsonine, an inhibitor of mannosidase II, had no obvious effect. Deoxymannojirimycin, an inhibitor of mannosidase I, did not prevent cell adhesion to the support and formation of monolayers or follicles, but it favored the maintenance of follicles at a time when they were no longer present in controls. It also led to the appearance of some follicles in cultures without thyrotropin. Castanospermine, an inhibitor of glucosidase I, did not prevent cell adhesion but slowed cell spreading, thus delaying monolayer formation. Pronase glycopeptides prepared from cell-surface glycoproteins were examined with respect to their behavior on concanavalin A-Sepharose. The glycopeptides from control cells displayed complex and high-mannose glycans. The content in complex glycans was decreased in inhibitor-treated cells, while that in hybrid or high-mannose glycans was increased, indicating that the inhibitors modify the N-glycan structures. In conclusion, N-glycosylation of glycoproteins is necessary for cellular adhesion to the support. Complex structures do not seem necessary for cell adhesion monolayer or follicle formation. High-mannose structures favor follicular organization, while glucoses on the high mannose structures hinder cell spreading.

1-Deoxynojirimycin↗