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Biomedical subjects

F Mercier

Publications and source records attributed to F Mercier.

At least 19 recordsLinked to original sources
PubMed1999

Smooth muscle differentiation in human vein wall at valvular level: comparison with nonvalvular wall and correlation with venous function.

The aim of this study was to evaluate local differences in smooth muscle differentiation in venous valves of patients suffering from chronic venous insufficiency, in relation to functional hemodynamic parameters measured by echo Doppler. These functional parameters did not correlate with smooth muscle differentiation at the valvular site. These results failed to support an initiating role of valvular structure in the development of chronic venous insufficiency. However, this work stresses differences in cellular differentiation of valve wall and nonvalvular smooth muscle cells in culture, and we found histologic differences in the structure of endovein and media (connective tissue relative content) between valvular and nonvalvular venous wall. The presence of smooth muscle cells in the valve cusp was demonstrated by smooth muscle alpha-actin-specific labeling and was observed to be restricted to one side of the valve cusp.

Actins↗
PubMed1998

Influence of the status of the contralateral carotid artery on the outcome of carotid surgery.

From 1985 to 1995, 747 carotid arteries were operated on in 694 patients, who were under general anesthesia and continuous electroencephalogram (EEG) monitoring. These patients were divided into three groups according to contralateral carotid status. Group 1 consisted of 58 patients who had contralateral occlusion; group 2, 53 patients who had contralateral stenosis and bilateral staged surgery; and group 3, 583 patients who had nonstenotic contralateral internal carotid artery. All groups were similar with regard to age and sex ratio. There were more asymptomatic patients in group 3 than in group 1 (39.9% vs. 25.8%) (p < 0.05), and less preoperative strokes in group 2 than in the other groups (3.7% vs. 17.2% and 13. 6%, respectively) (p < 0.05). Among risk factors, smoking was less frequent in group 3 (59.5%) than in group 1 (82.7%) and group 2 (77%) (p < 0.01), and coronary artery disease was more frequent in group 2 (60%) than in group 1 (32.7%) and Group 3 (26.4%) (p < 0.01). EEG changes occurred more frequently in group 1 (25.8%) than in group 2 [5.6% (first stage) and 3.8% (second stage)] and in group 3 (4.9%) (p < 0.01). A shunt was used only when EEG changes did not disappear after pharmacologic increasing of central blood pressure, which occurred more frequently in group 1 (10.3%) than in group 2 (0%) and group 3 (0.3%) (p < 0.05). The combined morbidity/mortality rate was similar for groups 1 and 3 (1.7% and 1.5%, respectively), however, transient morbidity was more frequent in group 1 (6.9%) than in group 3 (1.5%) (p < 0.05). The combined morbidity/mortality rate was higher in group 2 than in group 3 (7.5% vs. 1.5%) (p < 0. 05), and all strokes in group 2 were seen during the second-stage operation. In conclusion, contralateral carotid artery occlusion had minimal influence over carotid surgery results. Selective use of a shunt based on EEG monitoring prevented ischemic strokes, with minimal neurologic morbidity. Contralateral carotid stenosis did not affect operative strategy for first stage, but we noted a higher incidence of strokes during the second procedure.

Aged↗
PubMed1997

Video-assisted aortofemoral bypass: results in seven cases.

Between September 1995 and February 1996 we attempted to perform video-assisted aortofemoral bypass in nine patients. All patients were male with a mean age of 58.7 years, mean weight of 64.7 kg, and mean height of 1.69 m. In two patients it was necessary to switch to open laparotomy due to inadequate aortic exposure in one and extensive aortic calcification in the other. Aortobifemoral bypass was performed by the transperitoneal approach in three patients and unilateral aortofemoral bypass by the retroperitoneal approach in four patients. Exposure was more difficult by the transperitoneal approach. Postoperative graft patency was excellent in all patients. Video-assisted surgery did not shorten the delay to resumption of intestinal transit but it did reduce the duration of hospitalization and need for postoperative analgesia. Our experience suggests that video-assisted aortofemoral bypass without laparotomy can be performed and that it allows more rapid patient recovery.

Adult↗
PubMed1994

Treatment of vascular graft infection by in situ replacement with a rifampin-bonded gelatin-sealed Dacron graft.

PURPOSE: The purpose of this study was to treat an established prosthetic vascular graft infection by in situ replacement with a rifampin-bonded gelatin-sealed Dacron graft in an animal model. METHODS: The infrarenal aorta of 18 dogs was replaced with a gelatin-sealed graft contaminated in vitro by soaking it in a solution with Staphylococcus epidermidis. One week later, animals were randomized into three groups. In group I (control, (n = 6), the dogs did not undergo repeat operations. The dogs in groups II and III underwent repeat operation. In these animals the infected grafts were removed for bacteriologic analysis and replaced in situ with one of two types of grafts: group II (n = 6) received an untreated, gelatin-sealed graft; group III (n = 6) received a rifampin-bonded, gelatin-sealed graft. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 60 mg/ml saline solution of rifampin at 37 degrees C. All 18 dogs received no systemic adjunct antibiotic therapy. Control grafts and replacement grafts were removed 4 weeks after the initial implantation for bacteriologic analysis. When harvested, all the grafts were cut into two fragments, and quantitative bacterial cultures were obtained from all the fragments. Results were expressed as colony-forming units (CFU)/cm2 of graft material. RESULTS: All 18 initially implanted grafts and all the untreated replacement grafts were grossly infected at the time of removal, whereas all the rifampin-bonded replacement grafts had normal incorporation. None of the rifampin-bonded grafts grew bacteria, whereas all the initially implanted and all the untreated replacement grafts were infected (p < 0.01). Bacterial counts from the infected fragments were similar in control grafts (2.6 +/- 1.9 x 10(6) CFU/cm2), in initially implanted grafts of groups II (9 +/- 1.1 x 10(5) CFU/cm2) and III (1.3 +/- 1.5 x 10(6) CFU/cm2), and in untreated replacement grafts of group II (1.7 +/- 2.5 x 10(6) CFU/cm2). Blood culture results and culture results of liver, spleen, kidney, and lung specimens at the time of sacrifice were negative. CONCLUSION: This study demonstrates that rifampin-bonded gelatin-sealed Dacron grafts are resistant to infection when used for in situ replacement of an infected graft in the dog.

Animals↗
PubMed1994

[Surgical treatment of deep venous reflux. Techniques, indications and results].

INTRODUCTION: complications of deep venous insufficiency can lead to surgery if one fails with medical treatment. The etiology can be primitive or secondary, the symptoms are identical. They go from heaviness of the legs to chronic leg ulcers. Indication and technic of surgery depend on the etiology and the preoperative evaluation. PREOPERATIVE EVALUATION: it has to be anatomical and functional. Invasive investigations as venous blood pressure, ascending and descending venography, and non invasive investigations as duplex or triplex Doppler and plethysmography are used. TECHNICS: one can use three techniques. Valvuloplasty with or without venotomy, and with or without Dacron cuff. Transplantation of an axillary valvulated venous segment to femoral or popliteal vein. Transposition to a valvulated and competent great saphenous vein or deep femoral vein. INDICATIONS: one can propose transplantation or transposition for secondary deep venous insufficiency, and valvuloplasty for primary deep venous insufficiency. Stage 2 or 3 can be a clinical indication for surgery. RESULTS: valvuloplasty has good results with 60 to 80% free of clinical recurrence at 2 years. The results of the other technics seem to be less good. CONCLUSION: the fair results of surgery allow the use of it for some patients with a good evaluation. The improvement of the surgical results lie on the development of paraclinical evaluation and research on venous valvular hemodynamic.

Catheterization↗
PubMed1994

[Ruptured hypogastric aneurysm presenting as a sciatic paralysis. Case report and review of the literature].

A rupture of a hypogastric aneurysm presenting as a sciatic nerve compression is reported. The diagnosis was delayed as the lumbar spine CT Scan was normal. The aneurysm was visualized with a CT Scan of the pelvis, it was located in the front of the sacrum and continued through the greater sciatic foramen. After aneurysmorrhaphy the pain disappeared but the paralysis wasn't improved. 28 cases of ruptured hypogastric aneurysm have been collected by reviewing the literature, eight of them have simulated nerve compression.

Aged↗
PubMed1993

Antibody epitope mapping of the gastric H+/K(+)-ATPase.

Several antibodies against the gastric H+/K(+)-ATPase were analysed for the topological and sequence location of their epitopes. Topological mapping was done by comparing indirect immunofluorescent staining in intact and permeabilised rat parietal cells. Epitope definition was by Western analysis of intact and of trypsin or V8-proteinase-fragmented hog gastric ATPase combined with N-terminal sequencing of the fragments; by Western analysis of fragments of rabbit alpha subunit expressed in Escherichia coli; by analysis of rabbit alpha and beta subunits expressed in baculovirus-transfected SF 9 cells and by ELISA assay of synthetic octamers of one region of the hog alpha subunit. It was confirmed that the monoclonal antibody, mAb 95-111, recognised a cytoplasmic region between M4 and M5, close to the ATP-binding domain. The major epitope for monoclonal antibody mAb 12-18 was also in this region, but a second epitope was confirmed to be present in the M7/M8 region. The monoclonal antibody, mAb 146-14, was shown to recognise an extracytoplasmic epitope dependent on intact disulfide bonds, present in the rat and the rabbit, but absent in the hog beta subunit, due to non-conservative amino-acid substitutions. This antibody also recognised an epitope present in the alpha subunit of the H+/K(+)-ATPase at the M7 extracytoplasmic interface, perhaps indicating structural association of these two regions. The polyclonal antibody, pAb39, raised against the C-terminal portion of the enzyme, reacted only with the cytoplasmic surface of the H+/K(+)-ATPase, showing that the alpha subunit of the enzyme has an even number of membrane spanning segments.

Amino Acid Sequence↗
PubMed1993

Membrane topology and omeprazole labeling of the gastric H+,K(+)-adenosinetriphosphatase.

The gastric H+,K(+)-ATPase is an alpha beta heterodimer with close homology to the Na+,K(+)-ATPase. Digestion of intact cytoplasmic-side-out vesicles at a trypsin to protein ratio of 1/4 removed most of the cytoplasmic protein, leaving membrane-spanning pairs in high yield. These were visualized on gels and poly(vinylidene difluoride) (PVDF) membranes by sodium dodecyl sulfate solubilization of the membrane-embedded segments and labeling of the cysteine residues with fluorescein maleimide prior to electrophoresis. The membrane-spanning residues of the alpha subunit were found between positions 104 and 162 (M1/M2), 291 and 358(M3/M4), 776 and 835 (M5/M6), and 853 and 946 (M7/M8). Although this method did not detect membrane retention of the hydrophobic sequences subsequent to position 946, it provided biochemical evidence for at least eight membrane segments in the catalytic subunit. Intact vesicles containing this enzyme transport acid in the presence of KCl, valinomycin, and MgATP. Omeprazole accumulates in these acidified vesicles and converts to a cationic sulfenamide. This forms disulfides with accessible cysteines. The reaction with this extracytoplasmic thiol reagent inhibits ATPase activity. Full inhibition was obtained with a stoichiometry of 2.2 mol of omeprazole bound/mg of protein. Only the alpha subunit was labeled. The cysteines reacting with omeprazole were defined by proteolytic cleavage of 3H- or 14C-omeprazole-labeled enzyme followed by peptide sequencing of fragments separated on tricine gradient gels and transferred to PVDF membranes. Tryptic digestion at a 1/40 trypsin to protein ratio in the presence of ligands that stabilize the E2P form of the enzyme produced two large fragments, one of 68 kDa stretching from Glu47 to probably Arg666 that contained minor labeling and the other of 333 kDa beginning at Ala671 and extending to probably Arg946 that contained greater than 85% of the label. Digestion of labeled vesicles at 1/75 or 1/4 trypsin to protein ratios gave radioactive patterns consistent with labeling at Cys813 and/or Cys822 and at Cys892 and/or Cys927 and/or Cys938. V8 protease digestion of the solubilized alpha subunit produced a fragment extending from Ser838 to possible Asp900 that was omeprazole-labeled, showing that Cys892 was labeled and Cys927 and Cys938 were not. Hence, omeprazole labels the H+,K(+)-ATPase at cysteines within the M5/M6 and M7/M8 regions of the alpha subunit, accounting for its inhibitory action in vivo and in vitro.

Adenosine Triphosphate↗
PubMed1993

Histamine secretion from rat enterochromaffinlike cells.

BACKGROUND: In vivo studies have suggested an important role for gastric enterochromaffinlike (ECL) cells in mediating acid secretion. Direct evidence for this function is lacking and requires a preparation of highly purified ECL cells. This work investigates the possible role and mechanism of histamine release from the ECL cell in the peripheral regulation of acid secretion, using purified ECL cells from rat fundic mucosa. METHODS: A combination of elutriation and density-gradient centrifugation was used to purify rat fundic ECL cells. Enrichment was determined by the presence of acidic vacuoles containing a V type adenosine triphosphatase, electron microscopy, immunostaining, and histamine content and release. RESULTS: ECL cells were enriched at least 65-fold with respect to the fundic epithelium. Gastrin (EC50 0.2 nmol/L) and cholecystokinin octapeptide (nonsulfated, EC50 0.04 nmol/L) stimulated histamine release in a time- and dose-dependent manner, suggesting a CCK-B receptor subtype, confirmed by the inhibition of gastrin/CCK stimulation with the CCK-B antagonist L365,260. Somatostatin also inhibited gastrin-mediated histamine release. Single cell imaging showed that gastrin elevated intracellular cytosolic calcium concentration biphasically. Carbachol and the C kinase activator 120-tetradecanoylphorbol-13-acetate also stimulated histamine release. Epinephrine (blocked by propranolol), forskolin, and dibutyryl-5'-cyclic adenosine monophosphate were also effective, implicating a beta-adrenergic pathway. The H3 agonist R-alpha-methyl-histamine inhibited, whereas the H3-antagonist thioperamide potentiated gastrin/CCK stimulated histamine release. CONCLUSIONS: These in vitro results support a central role for the ECL cell in the peripheral regulation of gastric acid secretion.

Animals↗
PubMed1993

GEP31, a new gastric epithelial protein, early expressed during ontogenesis.

A set of monoclonal antibodies directed against various gastric markers was produced in order to study the developmental expression of the gastric mucosa. A previously described monoclonal antibody, mab 146.14, labeled the proton pump (H+, K+) ATPase specifically located in gastric parietal cells. Mabs 15.1 and 121.17 revealed the mucus of mucous neck cells and mucous surface cells, respectively. By addition, mab 81.1 was directed against a cell surface membrane protein antigen composed of a major 31 kDa component (called GEP31). Our study mainly focused on the characterization of GEP31. This protein was typically located in the gastrointestinal epithelial tract (stomach, small intestine, colon). Moreover, interesting features were observed during the study of the early ontogenesis of the gastric mucosa. The 31 kDa protein was detected at the onset of gland formation (day 18), and a gradual increase in expression of the protein could be observed between day 18 and day 19. Furthermore, a comparative study of the expression of different terminal differentiation markers of gastric epithelial cells ((H+, K+) ATPase, mucins) during the early period of ontogenesis revealed that GEP31 could be detected well before the appearance of these markers. To our knowledge, GEP31 thus appears as the earliest expressed specific cell surface epithelial gastric antigen described to date. Furthermore, the partial N-terminal amino acid sequence of GEP31 was determined and revealed that it is not a known protein.

Amino Acid Sequence↗
PubMed1992

cDNA cloning and membrane topology of the rabbit gastric H+/K(+)-ATPase alpha-subunit.

We have cloned and sequenced a cDNA for the rabbit gastric proton-potassium pump (H+/K(+)-ATPase) alpha-subunit. The deduced peptide contains 1035 amino acids (Mr 114,201) and shows 97% sequence identity with the respective rat and hog proteins. A monoclonal antibody 146-14 has been shown previously to react with the extracytoplasmic side of the catalytic H+/K(+)-ATPase subunit and here we show that the epitope is in the region between amino acids 855 and 902 (the numbering of the H+/K(+)-ATPase catalytic subunit throughout the paper refers to the rabbit sequence). The localization of this epitope in conjunction with previously observed trypsin cleavage sites in the C-terminal one third of the enzyme and the hydrophobicity plot of the deduced peptide sequence are evidence for a structural model for the alpha-subunit of the H+/K(+)-ATPase which contains at least ten membrane spanning segments, similar to that deduced for the Ca(2+)-ATPase of sarcoplasmic reticulum.

Adenosine Triphosphatases↗
PubMed1992

Structural aspects of the gastric H,K-ATPase.

The gastric H,K-ATPase is an alpha, beta heterodimer. The large catalytic subunit is composed, in the case of the hog enzyme, of 1033 amino acids, whereas the beta subunit is composed of about 291 amino acids and is heavily glycosylated. The membrane topology of the alpha subunit is difficult to predict using hydropathy analysis. Tryptic hydrolysis of intact, inside out vesicles followed by cysteine labelling with fluorescein-5-maleimide provided experimental evidence for an 8 membrane spanning model for the alpha subunit, between residues 104 and 162 (M1/M2), 291 and 358 (M3/M4), 776 and 835 (M5/M6), and 853 and 946 (M7/M8). No evidence was found for a pair of segments (M9/M10) towards the C terminal end of the molecule, contrary to predictions for the Na,K- and Ca-ATPases. Iodination of intact vesicles followed by carboxypeptidase Y cleavage of the C terminal tyrosines showed that the C terminal end of the alpha subunit was cytoplasmic. The epitope for antibody 146 was extracytoplasmic and located between residues 871 to 874 between M7/M8. The binding site of the K competitive imidazo-pyridine, SCH28080, was to the extracytoplasmic loop between M1 and M2, whereas the binding of the covalent SH reagent generated from acid activation of omeprazole in acid transporting vesicles was to 2 cysteines at positions 813 (or 822) and 892 predicted to be in the extracytoplasmic loops connecting M5/M6 and M7/M8, respectively. The beta subunit was only hydrolysed in broken vesicles. A fragment beginning at position 236 was liberated under these conditions only in the presence of reducing agents, showing that cysteine 210 and 263 were disulfide linked.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Chemomechanical coupling in the gastric H,K ATPase.

The gastric H,K ATPase is investigated in terms of its secondary structure by analysis of the binding sites of the extracytoplasmic inhibitors and by tryptic cleavage of intact, inside-out gastric vesicles. The inhibitors affect phosphorylation and other partial reactions of the ATPase that depend on cytoplasmic conformational changes. The K competitive imidazopyridine, SCH28080 binds to the first pair of transmembrane segments, M1/M2, probably at phe124 and asp136. Omeprazole which generates a cationic sulfenamide in acid spaces binds to either cys813 or cys822 at one site and cys892 at the other. These cysteines are located at the membrane spanning pairs, M5/M6 and at M7/M8. Tryptic cleavage of intact inside out vesicles followed by labelling with fluorescein-5-maleimide provides direct evidence for 8 membrane spanning segments between positions 104/162 (M1/M2), 291/358(M3/M4), 776/835 (M5/M6),853/946 (M7/M8). Evidence is lacking so far for M9/M10, postulated on the basis of hydrophobicity for the Ca ATPase. Conformational studies suggest that there is interaction between the cytoplasmic loop between M4 and M5 (ATP domain) and the extracytoplasmic domain of the enzyme at the inhibitor binding sites.

Adenosine Triphosphate↗
PubMed1989

[Peroperative anaphylactic shock caused by latex].

A case is reported of severe anaphylactic shock occurring in a 32 yr old woman after foetal extraction during caesarean section. The agent responsible was the latex from the surgical gloves used. This was proved by the different allergological tests carried out: positive prick-tests to the latex, positive human basophil degranulation test and the finding of specific anti-latex IgE. All the tests carried out using the anaesthetic drugs were negative.

Adult↗
PubMed1989

Membrane-cytoskeleton dynamics in rat parietal cells: mobilization of actin and spectrin upon stimulation of gastric acid secretion.

The gastric parietal (oxyntic) cell is presented as a model for studying the dynamic assembly of the skeletal infrastructure of cell membranes. A monoclonal antibody directed to a 95-kD antigen of acid-secreting membranes of rat parietal cells was characterized as a tracer of the membrane movement occurring under physiological stimuli. The membrane rearrangement was followed by immunocytochemistry both at the light and electron microscopic level on semithin and thin frozen sections from resting and stimulated rat gastric mucosa. Double labeling experiments demonstrated that a specific and massive mobilization of actin, and to a lesser extent of spectrin (fodrin), was involved in this process. In the resting state, actin and spectrin were mostly localized beneath the membranes of all cells of the gastric gland, whereas the bulk of acid-secreting membranes appeared diffusely distributed in the cytoplasmic space of parietal cells without any apparent connection with cytoskeletal proteins. In stimulated cells, both acid-secreting material and actin (or spectrin) extensively colocalized at the secretory apical surface of parietal cells, reflecting that acid-secreting membranes were now exposed at the lumen of the secretory canaliculus and that this insertion was stabilized by cortical proteins. The data are compatible with a model depicting the membrane movement occurring in parietal cells as an apically oriented insertion of activated secretory membranes from an intracellular storage pool. The observed redistribution of actin and spectrin argues for a direct control by gastric acid secretagogues of the dynamic equilibrium existing between nonassembled (or preassembled) and assembled forms of cytoskeletal proteins.

Actins↗
PubMed1989

A marker of acid-secreting membrane movement in rat gastric parietal cells.

A monoclonal antibody (mab 146.14) marker of the movement of acid-secreting membranes in rat gastric parital cells has been produced and characterized. Mab 146.14 recognized a 95-kD major component of a purified membrane fraction of rat gastric mucosa, the protein composition of which was similar to that of well characterized porcine H+ -K+ ATPase-enriched membranes, and that presented the characteristic shift of density depending on whether it was purified from resting or stimulated tissues. Further biochemical analysis characterized the antigen as a membranous protein that might be in its native form, part of a higher multimolecular complex. Immunocytochemical localization of the antigen demonstrated that only membranes related to acid secretion in parietal cells expressed the 95-kD antigen. In resting conditions, the 95-kD antigen was diffusely distributed in the cell cytoplasm associated with inactive tubulovesicles. In stimulated cells, by contrast, all the antigen was recovered associated with secretory active microvilli formed by the apical insertion of the previously resting internal tubulovesicles. In conclusion, the 95-kD antigen, presumably a part of the rat gastric proton pump, is a marker of acid-secreting membranes in rat parietal cells. The translocation of antigen and membranes, observed by both light and electron microscopy supports the fusion model of membrane insertion from a cytoplasmic storage pool to the apical surface upon stimulation of acid secretion.

Adenosine Triphosphatases↗
PubMed1988

PTH mRNA transcription analysis in infantile tumors associated with hypercalcemia.

The ability of infantile hypercalcemic tumors (three rhabdoid renal tumors, one cellular mesoblastic nephroma, and one hepatoblastoma) to produce parathyroid hormone (PTH) was tested using RNA-DNA hybridization. Results were compared with those obtained in one lung epidermoid carcinoma and one parathyroid adenoma from adult patients. Elevated plasma immunoreactive PTH (iPTH) concentrations were observed in three of five children. The only tumor in which PTH-RNA hybridization could be detected was the parathyroid adenoma. The integrity of the RNA preparations was further confirmed by positive hybridization obtained with a glucagon DNA probe in both normal pancreas and the rhabdoid tumors. Quantitative bone histomorphometry of tumor-bearing nude mice showed a reduction in bone formation and increased bone resorption, the opposite of what occurs in hyperparathyroidism. The PTH-like protein, which was detected by radioimmunoassays (RIA) in the sera of three patients, could not be correlated with tumor PTH mRNA transcription within the limits of our assays. In order to explain this discrepancy, we suggest that the tumors produce a factor (not PTH) which, in turn, elicits the excess iPTH which we detected by RIA.

Aged↗