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Biomedical subjects

H Michel

Publications and source records attributed to H Michel.

At least 127 records · Page 7Linked to original sources
PubMed1995

Endogenous sodium pump inhibitors in human urine. Further identification of inhibitors of Na-K-ATPase.

We investigated the presence of endogenous Na-K-ATPase inhibitor(s), ie, ouabain-like factors (OLFs), in the urine of salt-loaded healthy subjects. For this purpose 24-h urine was collected on days 3, 4, and 5 of high sodium intake (> 30 g NaCl/day). The samples then were lyophilized. Redissolved urine concentrates were acidified (pH 3.5) and subjected to gelchromatography on a Sephadex G-25 column where the OLFs eluted in the post-salt fraction IV. When lyophilized fraction IV was rechromatographed on Sephadex G-10, OLFs with molecular mass (M(r) of approximately 400 eluted in a late fraction IV/8 separate from added ouabain, ouabagenin (or digoxin), which eluted shortly after void volume. With the subsequent reverse-phase HPLC of fraction IV/8 a polar OLF-1 eluted in fraction IV/8a after the void volume in the water phase and a more apolar OLF-2 eluted at 20% acetonitrile in fraction IV/8d. Only the more apolar OLF-2 cross-reacted with a digoxin antibody. By preparative thin-layer chromatography OLF-1 and OLF-2 were purified as single compounds with potent dose-dependent Na-K-ATPase inhibition and Ki-values approximating 1.5 x 10(-5) mol/L and 1.5 x 10(-4) mol/L, respectively. Mass-spectroscopy (MS) showed M(r) of 391 and 1H-NMR characterized the endogenous urinary apolar OLF-2 as a compound that is structurally totally unrelated to ouabain; infrared (IR) spectroscopy of OLF-1 and OLF-2 also revealed no similarity with ouabain.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Engineered Fv fragments as a tool for the one-step purification of integral multisubunit membrane protein complexes.

The preparation of pure and homogeneous membrane proteins or membrane protein complexes is time consuming, and the yields are frequently insufficient for structural studies. To circumvent these problems we established an indirect immunoaffinity chromatography method based on engineered Fv fragments. cDNAs encoding the variable domains of hybridoma-derived antibodies raised against various membrane proteins were cloned and expressed in Escherichia coli. The Fv fragments were engineered to serve as bifunctional adaptor molecules. The Fv fragment binds to the epitope of the membrane protein, while the Strep tag affinity peptide, which was fused to the carboxy-terminus of the VH chain, immobilizes the antigen-Fv complex on a streptavidin sepharose column. The usefulness of this technique is illustrated with membrane protein complexes from Paracoccus denitrificans, namely, the cytochrome c oxidase (EC 1.9.3.1), the ubiquinol:cytochrome c oxidoreductase (EC 1.10.2.2), and subcomplexes or individual subunits thereof. These membrane proteins were purified simply by combining the crude P. denitrificans membrane preparation with the E. coli periplasmic cell fraction containing the corresponding Fv fragment, followed by solubilization and streptavidin affinity chromatography. Pure and highly active membrane protein complexes were eluted in the Fv-bound form using diaminobiotin for mild competitive displacement of the Strep tag. The affinity column could thus be reused under continuous operation for several months. Five to 10 mg of membrane protein complexes could be obtained without any detectable impurities within five hours.

Amino Acid Sequence↗
PubMed1995

Fv fragment-mediated crystallization of the membrane protein bacterial cytochrome c oxidase.

Crystallization of membrane proteins, a prerequisite for their X-ray crystallographic analysis, remains difficult. Here, we demonstrate that the crystallization of the cytochrome c oxidase from Paracoccus denitrificans can be mediated by co-crystallization with an antibody Fv fragment. The crystals obtained contain all four subunits of this membrane protein complex and the Fv fragment. The approach of co-crystallizing membrane proteins with antibody fragments should be useful in obtaining well-ordered crystals of membrane proteins in general.

Antibodies, Monoclonal↗
PubMed1995

Sham feeding disrupts phase III of the duodenal migrating motor complex in humans.

The role of the vagus nerve in the control of the intestinal migrating motor complex (MMC) is unclear. This study aimed to evaluate the effect of physiological vagal stimulation with sham feeding on phase III of the MMC. Antroduodenal motility was recorded in six healthy volunteers. The first phase III was used as a control, and sham feeding was performed during the second phase III. The MMC was disrupted within 1.5 +/- 0.4 min of sham feeding and its duration was shorter than the control phase III. Phase III propagation was inhibited in all subjects, most of them exhibiting no propagation beyond the third duodenal recording site. During sham feeding, the antrum exhibited transient phasic contractions in five out of six subjects. The duodenal motility index recorded for up to 30 min after the onset of the sham feeding was unchanged in five out of six subjects. We conclude that sham feeding consistently interrupted phase III of the duodenal MMC and induced antral contractions, but failed to provoke significant motor events in the duodenum.

Adult↗
PubMed1995

Small hepatocellular carcinoma in patients undergoing liver transplantation: detection with CT after injection of iodized oil.

PURPOSE: To assess computed tomography (CT) with iodized oil for depiction of small hepatocellular carcinoma (HCC) before liver transplantation. MATERIALS AND METHODS: Thirty-five consecutive cirrhotic patients underwent CT with iodized oil to determine the presence, number, size, and location of possible nodules. All patients underwent liver transplantation within 4 months after CT. Explanted livers were cut in 8-mm slices that corresponded to axial CT scan planes. Comparison between CT staging and pathologic findings was made. RESULTS: Pathologic studies showed 17 HCC nodules (diameter, 0.9-4.0 cm) in nine of the 35 livers. CT depicted nine of these 17 nodules. Lesion-by-lesion analysis revealed a sensitivity of 53%; CT falsely depicted three additional nodules not confirmed with pathologic findings. Patient-by-patient analysis revealed an 89% sensitivity and an 88% specificity. CONCLUSION: CT with iodized oil, when assessed lesion by lesion, has a low sensitivity. These results must be considered when liver resection is proposed for HCC.

Carcinoma, Hepatocellular↗
PubMed1995

Use of antibody fragments (Fv) in immunocytochemistry.

We developed a novel antibody fragment (Fv) technique for localization and determination of the surface topology of membrane protein complexes by immunogold electron microscopy. Several hybridoma cell lines producing murine monoclonal antibodies (MAbs) raised against bacterial membrane proteins were established. The cDNAs coding for the variable domains of the MAbs were cloned and expressed in Escherichia coli. The engineered Fv fragments served as trifunctional adapter molecules. The Fv fragment binds to the epitope of the membrane protein. The Strep tag fused to the VH chain was used for one-step affinity purification of the Fv fragments. Immunological detection of the membrane protein-bound Fv fragments in electron microscopy was accomplished either via the Strep tag with colloidal gold-labeled streptavidin or via the c-myc tag, which was fused to the VL chain, in combination with the c-myc tag-specific antibody 9E10 and a colloidal gold-labeled secondary antibody. We examined four Fv fragments directed against the cytochrome c oxidase or the ubiquinol-cytochrome c oxidoreductase of Paracoccus denitrificans and bacteriorhodopsin of Halobacterium halobium to show that this method is generally applicable. In all cases the Fv fragments showed the same results as their corresponding parent antibodies in electron microscopic immunostaining and other applications.

Antibodies, Monoclonal↗
PubMed1995

Cross hepatotoxicity between tricyclic antidepressants and phenothiazines.

OBJECTIVE: To describe a case of cross hepatotoxicity between tricyclic antidepressants and phenothiazines. PATIENT: A woman who developed three episodes of drug-induced hepatitis within 3 years as a result of successive treatment with two tricyclic antidepressants, trimipramine and desipramine, and one neuroleptic derivative, cyamemazine. INTERVENTIONS: The drugs were withdrawn after the patient experienced liver dysfunction, although bromazepam was later administered with no side effects. RESULTS: After three episodes of drug-induced hepatitis the patient's serum aspartate aminotransferase and alanine aminotransferase levels returned to normal when the tricyclic antidepressants and cyamemazine were withdrawn. CONCLUSIONS: Trimipramine, desipramine and cyamemazine are related by their chemical structures which include a tricyclic ring. This suggests that this chemical moiety might be involved in the hepatotoxicity of tricyclic antidepressants and phenothiazine derivatives.

Aged↗
PubMed1995

Effect of anti-ulcer drugs on DNA synthesis in adult normal human hepatocytes in culture.

The aim of this work was to investigate the effect of four H2 receptor antagonist, cimetidine, ranitidine, famotidine, nizatidine, and of two proton pump inhibitors, omeprazole and lansoprazole, on the mitotic response of human hepatocytes in primary culture. After plating at subconfluent density, cells were exposed to 0.2 to 20 mumol/L of these drugs for 48 hours, either in the absence or in the presence of epidermal growth factor (EGF). The rate of DNA synthesis was evaluated by [3H]-thymidine incorporation into genomic DNA. Both the basal rate of DNA synthesis and the extent of stimulation by EGF exhibited a wide interindividual variability, and were not correlated with the viability of freshly prepared cells. In contrast, the effects of anti-ulcer drugs on the rate of DNA synthesis were clearly reproducible from one culture to another. H2 receptor antagonists had no significant effect (P > .2) over the entire range of concentration tested, whereas omeprazole and lansoprazole significantly inhibited the rate of DNA synthesis by 60% to 90% at 30 mumol/L (P = .016). This effect was concentration dependent between 2 and 20 mumol/L. Neither of the drugs tested was cytotoxic under the conditions used in this work, as assessed by measurements of the do nov protein synthesis. We conclude that, in contrast to H2 receptor antagonists, omeprazole and lansoprazole are able to interfere with the replicative synthesis of DNA in human hepatocytes in culture, at suprapharmacological concentrations. Whether or not this effect is clinically significant remains to be established.

Anti-Ulcer Agents↗
PubMed1995

Lethal acute graft-versus-host disease in a liver transplant recipient: relations with cell migration and chimerism.

We report herein the case of a patient who developed fatal acute graft-versus host disease (GvHD) after liver transplantation (LT). GvHD occurred 18 days after LT and was characterized by skin epidermolysis, diarrhea and leucopenia. Skin biopsy showed epidermal dyskeratosis with epithelial necrosis, a lesion consistent with GvHD. Despite immunosuppressive therapy, the patient died within 24 days. In our observation, GvHD occurred although five HLA compatibilities were identified between the donor and the recipient, an apparently favorable and uncommon situation. This case further supports the qualification that LT may be complicated by GvHD and strongly suggests that minor rather than major histocompatibility antigens are the main target of allogenic interactions of GvHD. The involvement of chimerism in GvHD is controversial and requires further investigation.

Cell Movement↗
PubMed1995

[Familial transmission of hepatitis C virus].

OBJECTIVES: The intrafamilial transmission of hepatitis C virus infection was assessed in the family members of patients with chronic hepatitis C. METHODS: The presence of serum anti-hepatitis C virus (HCV) antibodies and epidemiological features were studied in 193 relatives (104 heterosexual partners, 89 children) of 113 patients with chronic hepatitis C. The presence of serum anti-HCV antibodies was detected by an ELISA 2 test and confirmed by a RIBA 2 test. In all patients, liver injury was ascertained by biopsy (31 cirrhosis, 82 chronic active hepatitis). RESULTS: Eleven of 104 (10.6%) regular heterosexual partners were positive for anti-HCV antibodies. In 8 of these, risk factors were detected (drug addiction: n = 6, blood transfusion: n = 1, occupational exposure: n = 1). Only 3 of 96 (3.2%) regular heterosexual partners without percutaneous risk factors were positive for HCV. Among couples with heterosexual partners negative for anti-HCV antibodies, the mean duration of the sexual relationship was 12 years. Serum anti-HCV antibodies were present in 1 of 89 (1.1%) children without history of blood transfusion or drug addiction. None of the 35 children born after supposed maternal contamination were positive for serum anti-HCV antibodies. CONCLUSIONS: We conclude that the prevalence of serum anti-HCV antibodies, assessed with second generation tests, in sexual partners of patients with chronic hepatitis C, is lower than previously reported with first generation anti-HCV tests but higher than in the general population (3.2% vs approximately equal to 1%). Serum anti-HCV antibodies were very rarely detected in children from patients with chronic hepatitis C.

Adult↗
PubMed1995

[Prognostic factors of hepatocellular carcinoma: a multivariate analysis in 113 patients].

UNLABELLED: The aim of this study was to identify clinical, biological or morphological prognostic factors in 113 patients with HCC in terms of survival. All patients (100 men, aged 65 [28-85], 95% cirrhosis) were diagnosed between 1982-1990. Mean survival time was 21 +/- 3 weeks. Eleven (over 25) variables were isolated by univariate analysis. A multivariate survival analysis (Cox regression model) disclosed that serum creatinine (p = 0.0002), alkaline phosphatase (p = 0.02) and Okuda's stage (p = 0.025) were independent predictors of survival. Comparison of survival curves for different values of these prognostic variables allows division of patients in three groups of prognostic significance in terms of survival (p < 0.05). CONCLUSION: these results facilitate stratification of patients with HCC to design and evaluate future controlled trials.

Aged↗
PubMed1995

[Lichen planus and hepatitis C virus. Apropos of 5 new cases].

Lichen planus is an immunologically mediated skin or mucous disease, which has recently been described in some patients with hepatitis C virus-related liver disease. We report 5 new cases of the association of hepatitis C with lichen planus, to be added to the 15 cases published in the literature. The sex ratio (female/male) was of 1.2. Lichen planus occurred more frequently in chronic active hepatitis (2/3 of cases) than in cirrhosis (1/3 of cases). Lichen planus manifestations were only mucous (30%), only cutaneous (40%) or both (30%). Mucous lesions were mainly observed in patients with cirrhosis (3/4 of cases). The onset of skin and hepatic manifestations was variable, with liver disease as the most frequent revealing symptom (60%). The influence of interferon remains unclear. However, it seemed to trigger more than to relieve lichen planus.

Adrenal Cortex Hormones↗
PubMed1995

[Liver cirrhosis and granulomatous hepatitis after prolonged ingestion of lysine acetylsalicylate].

We report the case of a 75-year-old woman who was hospitalized for serum aminotransferase elevation. She had taken 1 g/d of salicylate therapy (Aspegic 1000) for 5 years, clorazepate for 10 years, naftidrofuryl for 8 months and quinapril for 3 months. Liver histology showed cirrhosis and granulomatous hepatitis. Discontinuation of salicylate therapy resulted in normalization of liver tests, although other drug administration was pursued. This observation suggests that salicylate therapy can induce cirrhosis.

Aged↗