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Biomedical subjects

H Michel

Publications and source records attributed to H Michel.

At least 235 records · Page 13Linked to original sources
PubMed1991

[Heterotopic hepatic transplantation. Apropos of a case treated in the terminal stage of decompensated alcoholic cirrhosis].

Heterotopic liver transplantation is an exceptional indication for acute or chronic liver disease. The authors report a case of auxiliary liver transplantation performed for end-stage alcoholic cirrhosis. The patient was contra-indicated for orthotopic transplantation because of poor general and nutritional status. The HLT was indicated because of intractable ascites, liver insufficiency and chronic encephalopathy. The operation was performed according to the technique described by Fortner. Liver function tests returned to normal within 3 days and the only postoperative complication were gastro-intestinal bleeding due to CMV viral infection. Liver function was assessed by HIDA scintigram which showed blood intake by the graft and atrophy of the native liver. The patient was discharged after 3 months. The follow-up is 17 months. At the 15th month control, liver CT showed multiple hypodense nodules biopsied and corresponding to metastasis from a probable pancreatic carcinoma. ERCP and morphologic explorations did not show the primary tumor. The authors discuss the indications of HLT, the rules of successful performance of HLT and the problem of the graft involvement by metastases.

Hemodynamics↗
PubMed1991

[Corticoid therapy in the treatment of acute alcoholic hepatitis. Results of a meta-analysis].

A meta-analysis of 10 randomized trials comparing steroid therapy with placebo or abstention was performed. Trials were pooled for severity of acute alcoholic hepatitis and time of analysis. Papers with survival analyses at one and three months were included. The robustness of this meta-analysis was analysed after exclusion of trials analysing survival at three months only, trials including mild forms, or atypical trials. Comparisons were made use the Der Simonian-Laird and Mantel-Haenszel-Peto methods. All results were statistically significant. However, if only one medium size trial were to be added, the results would no longer be significant. Taking into account the complications of steroid therapy, we conclude that further clinical trials are necessary to confirm the effectiveness of steroid therapy, especially for the group of patients with severe alcoholic hepatitis.

Acute Disease↗
PubMed1990

[Endogenous natriuretic and ouabain-like factors. Their potential role in volume and blood pressure regulation].

The existence of an endogenous natriuretic hormone and ouabain-like factors (OLF) has been postulated for many years. This postulate was based on our original observation that a small M.W. fraction in the serum after acute expansion of the extracellular fluid volume (ECFV) not only exhibited natriuretic activity but also inhibited the Na-K-ATPase enzyme in vitro similar to ouabain. Since then, numerous studies confirmed the presence of OLFs in serum, urine, cerebrospinal fluid, and various organs including the heart and hypothalamus. Some of these OLFs are well-known endogenous compounds, such as free unsaturated fatty acids, which inhibit in vitro transmembranous sodium transport, Na-K-ATPase and 3H-ouabain binding to its membrane receptor or cross-react with digoxin antibodies. Chemically yet undefined OLFs of potentially hypothalamic origin were detected in various models of experimental and clinical hypertension and are suggested to play a pathophysiological role especially in salt- and volume-dependent forms of hypertension. Our results show that OLFs isolated from the urine of salt-loaded healthy subjects strongly enhance basal and vasopressin-stimulated release of calcium in vascular smooth muscle cells and platelets similar to the effects we had observed with endothelin. This urine fraction also exhibits natriuretic activity which increases in parallel with sodium intake. Further chromatographic separation and amino acid analysis confirmed the peptidic nature (M.W. less than 1000) of the natriuretic factor(s). However, the two biological activities, namely natriuretic and ouabain-like activities, reside in distinct and chemically different compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Hereditary protein S deficiency responsible for digestive vascular thrombosis].

Protein S is a physiological inhibitor of coagulation. It intervenes as co-factor of activated protein C and increases the inactivation of factors V and VIII induced by the latter. Patients with protein S deficiency are exposed to recurrent venous and arterial thrombosis. Most of these thromboses affect the lower limbs, but other regions, and notably the digestive tract, may be involved. Deficiencies in physiological inhibitors of coagulation, and in particular protein S, seem to be a new entity in the vascular pathology of the gastrointestinal system. All young patients with thromboembolic accidents affecting the digestive tract should be investigated for protein S deficiency. If such deficiency is found, then all members of the patients' family must also be investigated. Long-term treatment with antivitamin K drugs prevents recurrences of these thromboembolic accidents.

Adult↗
PubMed1990

Expression in Escherichia coli of the psbO gene encoding the 33 kd protein of the oxygen-evolving complex from spinach.

The cDNA for the 33 kd protein from the oxygen-evolving complex of spinach together with the coding region for the hydrophobic C-terminal part of the transit sequence was cloned into the expression plasmid pDS12/33Ex. The 33 kd protein precursor was expressed in Escherichia coli, secreted into the periplasm and correctly processed to the mature 33 kd protein. Thus the hydrophobic domain of the transit sequence, preceded by a methionine and two lysine residues, can function as a bacterial signal peptide. The periplasmic proteins were released from the cells by osmotic shock and the expressed protein was purified by anion exchange chromatography. The protein was identified by SDS-PAGE and Western blotting. N-terminal sequence analysis showed that the cleavage of the signal peptide occurred at the correct position. The expressed protein could be rebound to CaCl2-washed PSII particles and oxygen evolution was restored in equal amounts by the 33 kd protein from both E. coli and spinach.

Amino Acid Sequence↗
PubMed1990

3-(Trifluoromethyl)-3-(m-isothiocyanophenyl)diazirine: synthesis and chemical characterization of a heterobifunctional carbene-generating crosslinking reagent.

A new hydrophobic heterobifunctional photocrosslinking reagent 3-(trifluoromethyl)-3-(m-isothiocyanophenyl)diazirine (TRIMID), a carbene precursor, and its radioiodinated analogue [125I]TRIMID, have been synthesized and chemically characterized. The reagents were applied for membrane protein modification in human erythrocyte membranes and purple membranes from Halobacterium halobium. Covalent labeling of the anion transport protein (band 3) via the isothiocyanate function was confirmed. Radiolabeled TRIMID was detected in at least two thermolysin-generated transmembrane fragments of the anion transport protein, and half-maximal inhibition of the erythrocyte anion transport activity was attained with 2.2 mM reagent. In bacteriorhodopsin (BR), a common binding site for the monofunctional phenylisothiocyanate and the bifunctional crosslinking reagent was identified: preincubation of purple membranes with TRIMID suppressed phenylisothio-[14C]-cyanate binding to BR. [125I]TRIMID was recovered in V-1, the N-terminal segment of BR, which includes the phenylisothiocyanate binding site Lys-41. Light-induced intramolecular crosslinking of band 3-derived thermolytic fragments was not observed, although the carbene was generated in situ and photocrosslinking of the protease V8 fragments of BR was not detected. Chemical and physicochemical characteristics of the new reagent are discussed with regard to limitations imposed for photoinduced site-directed crosslink formation.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1990

Omeprazole is an aryl hydrocarbon-like inducer of human hepatic cytochrome P450.

Omeprazole is a new drug used for its high efficiency as an inhibitor of gastric acid secretion. This substituted benzimidazole molecule had been shown to decrease several liver cytochrome P450-mediated monooxygenase activities both in vitro and in vivo. The present work was undertaken to determine whether this drug was an inducer of cytochrome P450 in humans. Primary cultures of human hepatocytes were maintained in a serum-free, chemically defined medium for 0-96 hours in the absence or in the presence of omeprazole (1-100 mumol/L) or of other cytochrome P450 inducers such as 3-methylcholanthrene, beta-naphthoflavone, or rifampicin for comparison. Omeprazole produced a time- and concentration-dependent increase in (a) cytochrome P450IA2 accumulation determined by western blot in microsomes from omeprazole-treated cells, while the level of other cytochrome P450 forms including P450IID6, IIE1, and IIIA was not increased in the same culture; (b) several monoxygenase activities, including phenacetin deethylase and acetanilide hydroxylase (cytochrome P450IA2) and ethoxyresorufin deethylase and benzpyrene hydroxylase (cytochrome P450IA1); (c) cytochrome P450IA2 de novo synthesis, determined by immunoprecipitation of cell lysate from [3H]Leu-labeled cells; (d) cytochromes P450IA1 and IA2 mRNAs, determined by northern blot analysis. An in vivo study was carried out on liver microsomes from five patients for whom hepatic biopsy specimens were available before and after repeated administration of omeprazole (20 mg/day for 4 days). In all cases, several-fold increases in cytochrome P450IA2 and specific cytochrome P450IA subfamily-dependent monooxygenase activities were observed in agreement with the results from cell culture. It was concluded that omeprazole is an aryl hydrocarbon-like inducer of cytochrome P450 secretion in human liver both in vitro and in vivo. This drug is therefore likely to increase the metabolism of any xenobiotic specifically oxidized by a cytochrome P450IA subfamily. This could potentiate the hepatotoxicity of phenacetin or paracetamol and activation of procarcinogens.

Aged↗
PubMed1990

Regulation of atrial natriuretic peptide receptors in glomeruli during chronic salt loading.

The effects of chronic salt loading on atrial natriuretic peptide (ANP) receptor density and affinity were studied in isolated renal glomeruli of male Sprague-Dawley rats, which received 0.9% saline as drinking fluid (NaCl-rats) and a normal rat chow diet for 35 days (N = 12). Animals on a low sodium intake received the same diet, but deionized water and served as controls (C) (N = 12). After 35 days blood pressure was only slightly increased to 136 +/- 9 in NaCl-rats versus 120 +/- 2 mm Hg in C (NS). Glomerular filtration rate, plasma cGMP and plasma ANP remained unaltered. Determination of total ANP receptor characteristics in these rats indicated a significant down-regulation of ANP receptors in salt loaded rats. Since ANP-stimulated cGMP formation was not affected by salt loading, the roles of clearance (C) and of biologically active (B) receptors were further evaluated at 21 degrees C on freshly isolated and acid washed (pH 5) glomeruli in seven animals after 35 days of salt loading and in seven animals on a low sodium intake. B-receptors were assessed by blocking C-receptors with 4-23 cANP. C-receptor numbers were lower in NaCl-rats (97 +/- 8 vs. 184 +/- 14 fmol/mg protein in C; N = 7; P less than 0.02), while C-receptor affinity was increased (Kd: 12 +/- 3 pM in NaCl-rats vs. 22 +/- 5 pM in C; P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Structure and transcription of the genes encoding the B1015 light-harvesting complex beta and alpha subunits and the photosynthetic reaction center L, M, and cytochrome c subunits from Rhodopseudomonas viridis.

The genes encoding the beta and alpha subunits of the B1015 light-harvesting complex (LHC) and the L, M, and cytochrome c subunits of the photosynthetic reaction center from Rhodopseudomonas viridis are organized in an operon, in analogy to other nonsulfur purple bacteria, named the puf operon. In photoheterotrophically grown cells, two abundant puf operon mRNA species of 3,581 and 621 bases were present. The large transcript encoded the LHC beta, LHC alpha, and reaction center L, M, and cytochrome c polypeptides, whereas the small transcript only coded for the LHC beta and alpha polypeptides. Both transcripts share a common 5' end which is located 115 bases upstream from the initiation codon of the LHC beta gene. Two additional low-level transcripts of 3,718 and 758 bases with 5' ends 254 +/- 3 bases upstream from the LHC beta gene were detected. Analysis of the DNA sequence preceding the different 5' ends revealed DNA elements of striking homology. The 3' ends of the small transcripts were mapped within the alpha-L intercistronic DNA region downstream from a sequence capable of forming a very stable stem-loop when transcribed into RNA. The 3' termini of the large transcripts are located immediately downstream from the region coding the cytochrome c subunit in two areas resembling rho-independent transcription terminators. No open reading frames corresponding to pufQ and pufX from Rhodobacter capsulatus and Rhodobacter sphaeroides were present in the flanking DNA regions of the puf operon. In contrast, an open reading frame ending 191 base pairs upstream from the LHC beta gene showed 50% homology at the amino acid level to the available sequence of the bchA gene from R. capsulatus. The genes coding for the B1015 LHC subunits had C-terminal extensions of 13 (beta) and 10 (alpha) amino acids which were not present in the proteins isolated from intracytoplasmic membranes.

Amino Acid Sequence↗
PubMed1990

Sequence analysis and transcriptional organization of the Rhodopseudomonas viridis cytochrome c2 gene.

The cytochrome c2 gene (cycA) of the purple nonsulfur bacterium Rhodopseudomonas viridis was isolated from a genomic library by using two degenerate oligonucleotides containing all possible DNA sequences predicted from the published amino acid sequence of this protein (Ambler et al., Proc. Natl. Acad. Sci. USA 73:472-475, 1976). Cloning and sequence analysis of the cytochrome c2 gene indicated the presence of a typical procaryotic 20-residue signal peptide, suggesting that this periplasmic protein in synthesized in vivo as a precursor. In addition, four amino acids were found to be different by comparing the published sequence of the mature protein with that deduced from the isolated cycA gene (Lys-14----Leu, Ser-46----Ala, Ile-84----Val, Leu-97----Ile). Northern (RNA) blot analysis and fine mapping of the 5' and 3' ends of the cycA gene transcript from photoheterotrophically grown R. viridis cells revealed one abundant transcript of 523 to 530 nucleotides in length, with the transcription start site at position -39 relative to the coding region of cytochrome c2. A low-abundance transcript with an extended 3' end (about 600 bases in length) is thought to be processed by exonucleases, resulting in the slightly shorter main transcript.

Amino Acid Sequence↗
PubMed1990

First glance on the three-dimensional structure of the photosynthetic reaction center from a herbicide-resistant Rhodopseudomonas viridis mutant.

A first model of the three-dimensional structure of the photosynthetic reaction center of the mutant T1 (SerL223----Ala, ArgL217----His) from Rhodopseudomonas viridis, resistant toward the triazine herbicide terbutryn (2-methylthio-4-ethylamino-6-t-butylamino-s-triazine), has been developed from X-ray data measured to a resolution of 2.5 A. The secondary quinone, QB, which in T1 binds better than in the wild type, is present in the crystals. Both substituted residues are clearly visible in the difference fourier map. The replacement of these two residues in the QB site causes only minor changes in the overall structure of the protein.

Amino Acid Sequence↗
PubMed1990

Sequence analysis of four atrazine-resistant mutants from Rhodopseudomonas viridis.

Four atrazine-resistant mutants from the purple bacterium Rhodopseudomonas viridis were isolated. Sequence analysis revealed three different mutant strains carrying mutations in the herbicide-binding pocket: i) MAV 2: L212-Glu----Lys, ii) MAV 3: L216-Phe----Ser and iii) MAV 4 = MAV 5: L217-Arg----His, L220-Val----Leu. Except MAV 3 all Rps. viridis mutants are different from those selected by their resistance towards the closely related triazine terbutryn.

Amino Acid Sequence↗
PubMed1990

[Extracorporeal lithotripsy in gallbladder calculi. Results of a single-center experience of 31 patients].

The authors studied thirty one cases (18 women, 13 men) of extracorporeal shock-waves lithotripsy on symptomatic gallbladder stones realized with piezoelectric generators. There were one to six stones per patient with individual stone size from 8 to 40 mm; among them 16% were calcified. Any anesthesia was necessary. Shock-wave frequency was 1.25 and 2.5 Hz. The average number of shock waves administered was 4,600 per treatment. Fragmentation occurred in 67% after first treatment and in 74% after second treatment. Gallstones disappeared in 9.5% and 19.5% of patients after 6 weeks and 4 months respectively. There was no modification after four treatments in 22.5% of patients. Minor side effects were noted: back pain (29%) probably because of uncomfortable position during treatment; increased thickness of gallbladder wall (26%); biliary pain (22%). Two episodes of biliary tract obstruction by stone fragments (one mild pancreatitis, one jaundice with liver enzymes elevation) disappeared spontaneously. These results were comparable with those of other groups using the same shock waves lithotripter.

Adult↗
PubMed1990

pH monitoring for 24 hours of gastroesophageal reflux and gastric function after intrathoracic gastroplasty after esophagectomy.

Gastroesophageal reflux is the main complaint after intrathoracic gastroplasty for carcinoma of the esophagus. Eighteen patients who underwent intrathoracic gastroplasty were studied by 24 hour pH monitoring. Two groups of patients were separately evaluated according to the surgical procedure performed--group 1, nine patients with tubulized stomach and gastroesophageal anastomosis at the apex of the thorax, and group 2, nine patients without tubulized stomach and with low gastroesophageal anastomosis. Gastroesophageal reflux and gastric function were analyzed. Gastroesophageal reflux was clinically present in 36 per cent of patients. During the 24 hour pH monitoring period, the percentage of time that the esophageal electrode showed a pH value of less than 4 was shorter for group 1 than for group 2 (13.3 +/- 11.3 versus 32.7 +/- 21.7), indicating less gastroesophageal reflux. Gastric secretion was also studied with 24 hour pH monitoring. Gastric secretion was reduced after gastroplasty, compared with a control group. Gastric secretion was identical between groups 1 and 2. Tubulization did not impair gastric secretion. Findings from this study show that good functional results can be achieved after intrathoracic gastroplasty if the anastomosis is performed on the neck or at the apex of the thorax. This technique can reduce gastroesophageal reflux without an antireflux procedure.

Adult↗