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Biomedical subjects

H Michel

Publications and source records attributed to H Michel.

At least 289 records · Page 16Linked to original sources
PubMed1986

The 'light' and 'medium' subunits of the photosynthetic reaction centre from Rhodopseudomonas viridis: isolation of the genes, nucleotide and amino acid sequence.

The 'light' (L) and the 'medium' (M) subunits of the photosynthetic reaction centre from Rhodopseudomonas viridis were isolated and their amino-terminal sequences, as well as the sequences of several chymotryptic peptides, determined. Rps. viridis DNA was cloned in the Escherichia coli plasmid pBR322. Mixed oligonucleotide probes derived from the amino acid sequences were synthesized and utilised to isolate one clone which contained the genes for the L and M subunits of the reaction centre as well as the alpha and beta subunits of the light-harvesting complex and part of the gene for the reaction centre cytochrome. The nucleotide sequences of the L and M subunit genes and teh derived amino acid sequences are presented. The L subunit consists of 273 amino acids and has a mol. wt of 30 571. The M subunit consists of 323 amino acids and has a mol. wt of 35 902. The primary structure is discussed in the light of the recently published secondary and tertiary structure which has shown that both subunits contain five membrane-spanning helices.

Amino Acid Sequence↗
PubMed1986

Pigment-protein interactions in the photosynthetic reaction centre from Rhodopseudomonas viridis.

An X-ray structure analysis of the photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis provides structural details of the pigment-binding sites. The photosynthetic pigments are found in rather hydrophobic environments provided by the subunits L and M. In addition to apolar interactions, the bacteriochlorophylls of the primary electron donor (;special pair') and the bacteriopheophytins, but not the accessory bacteriochlorophylls, form hydrogen bonds with amino acid side chains of these protein subunits. The two branches of pigments which originate at the primary electron donor, and which mark possible electron pathways across the photosynthetic membrane, are in different environments and show different hydrogen bonding with the protein: this may help to understand why only one branch of pigments is active in the light-driven electron transfer. The primary electron acceptor, a menaquinone (Q(A)), is in a pocket formed by the M subunit and interacts with it by hydrophobic contacts and hydrogen bonds. Competitive inhibitors of the secondary quinone Q(B) (o-phenanthroline, the herbicide terbutryn) are bound into a pocket provided by the L subunit. Apart from numerous van der Waals interactions they also form hydrogen bonds to the protein.

Journal Article↗
PubMed1986

The treatment of refractory ascites by the LeVeen shunt. A multi-centre controlled trial (57 patients).

A multi-centre random trial of 57 cases of alcoholic cirrhosis with refractory ascites was carried out; 29 patients received a LeVeen shunt and 28 were treated by conventional medical therapy. The effectiveness of the LeVeen shunt in reducing ascites was good in the first month, but was not different from conventional medical therapy by the end of one year. Complications were significantly more frequent in the surgical group. Of the 29 patients fitted with a LeVeen shunt, 25 developed one or more complications. Of the 28 patients in the medical control group, only 8 developed complications. The mortality rate of the two groups also differed significantly. Twelve patients in the surgical group (41%) died in the course of the first month against only 5 (18%) in the medical control group. By the end of one year, the mortality rate of the two groups was almost identical: 23 (79%) and 21 (75%) respectively. These observations confirm the poor prognosis for refractory ascites in cases of alcoholic cirrhosis and the inadvisability of attempting to treat it by implanting a LeVeen shunt.

Ascites↗
PubMed1986

Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Crystals of the reaction center (RC) from Rhodopseudomonas sphaeroides with the space group P2(1)2(1)2(1), have been studied by x-ray diffraction. The Patterson search (molecular replacement) technique was used to analyze the data, with the structure of the reaction center from Rhodopseudomonas viridis as a model system. A preliminary electron density map of the reaction center from R. sphaeroides has been obtained. Comparison of the structure of the RC from R. sphaeroides with that from R. viridis showed the following conserved features: five membrane-spanning helices in each of the L and M subunits, a single membrane-spanning helix in the H subunit, a 2-fold symmetry axis, and similar positions and orientations of the cofactors. Unlike the RCs from R. viridis, both quinones are retained in the RCs from R. sphaeroides. The secondary quinone is located near the position related by the 2-fold symmetry axis to the primary quinone.

Bacterial Proteins↗
PubMed1986

Salt or no salt in the treatment of cirrhotic ascites: a randomised study.

To compare the effect of diet, cirrhotic patients with ascites were randomised into two treatment groups: (1) a low sodium diet (21 mmol) per day or (2) an unrestricted sodium intake. Both groups received effective doses of diuretics (spironolactone or, if necessary, spironolactone and furosemide. One hundred and forty patients from 12 liver units were included according to well defined criteria (group 1: 76; group 2: 64). After an initial four to seven day period of bed rest and salt restriction (21 mmol sodium pd), randomisation was done in each centre. We saw no significant difference between the two groups with respect to clinical and biochemical data; mortality or withdrawal (definitive or temporary) because of biochemical disturbances (group 1: 34%, group 2: 22%); the time for complete disappearance of ascites was significantly shorter (p = 0.014) for the salt restricted patients actuarial survival (curves plotted up to the 120th day) was not statistically different (p = 0.18), but division into subgroups using various prognostic factors showed that survival was significantly better for salt restricted patients without previous gastrointestinal bleeding (p = 0.02); hospitalisation time and costs were identical in both groups. We conclude that the advantage of a normal salt diet was not shown in this study.

Adult↗
PubMed1986

Long term results after portal disconnection of the esophagus using an anastomotic button for bleeding esophageal varices in cirrhosis.

From 1968 to 1984, 250 patients with cirrhosis and bleeding esophageal varices underwent portal disconnection of the esophagus using either Murphy's button (before 1974) or an esophageal device developed by one of the authors (after 1974). One hundred and thirty-four patients underwent operation on an elective basis and 116 underwent emergency procedures. With the use of Child's classification, 62 patients were class A, 125 were class B and 63, class C. The over-all operative mortality rate was 24.4 per cent but this varied with the hepatic functional status and whether or not the operation was done on an elective or emergency basis. The long term survival rates were 53 per cent at one year, 36 per cent at three years, 24 per cent at five years and 8 per cent at ten years. Ninety-six per cent of the patients were without proved recurrent esophageal bleeding at one year, 88 per cent at three years, 79 per cent at five years and 66 per cent at ten years. Portal disconnection of the esophagus using an anastomotic button is a simple and effective procedure which can benefit many patients with cirrhosis who undergo an operation for bleeding varices on an elective or emergency basis. It constitutes an efficacious prophylactic means for preventing recurrent bleeding from esophageal varices.

Actuarial Analysis↗
PubMed1986

[Esophageal scintigraphy and pH measurement in asthmatic adults suspected of having gastroesophageal reflux].

Fifty-five adults with asthma were explored by gastroesophageal scintigraphy (GES) and pH monitoring (3 postprandial hours, 12 nocturnal hours). For their asthma, all patients received theophylline twice a day. Associated digestive symptomatology led to investigations for gastroesophageal reflux (GER). Twelve hours pH monitoring, the reference method, was validated in 13 normal volunteers. During 12 hr pH monitoring, 4 criteria were studied: number of GER, percentage of time at pH 4, number of GER longer than 5 min and longest GER. Acid reflux occurred in 69 p. 100 of cases. Three hours postprandial pH monitoring and GES showed a GER in 40 and 47.5 p. 100 of cases (p greater than 0.05). GES revealed pulmonary aspiration in almost a quarter of asthmatic adults. Detection of a 30 p. cent increment of nocturnal GER by long pH monitoring could explain that results may differ with various techniques. Pulmonary aspiration was more frequent after longer and deeper GER. The mean duration of GER was more than 9 min but it was not significantly different from GER without pulmonary aspiration. GES may be helpful after 12 h pH monitoring because it can prove pulmonary aspiration. Its association with long and intense GER at 12 h pH monitoring suggests definitive surgical treatment of GER in asthmatic patients.

Adolescent↗
PubMed1985

[Value of the transjugular venous approach to the liver in the diagnosis of cirrhosis. 333 cases].

The transjugular technique is very useful for the diagnosis of cirrhosis since it makes it possible, in one single exploratory procedure, to perform a needle aspiration biopsy (despite coagulation disorders and ascites) and to measure the porto-caval pressure gradient. In our series cirrhosis was diagnosed by liver biopsy alone in 249 out of 333 patients (77%), and the porto-caval gradient was found to be elevated in 313 patients (97%).

Adult↗
PubMed1985

The ;heavy' subunit of the photosynthetic reaction centre from Rhodopseudomonas viridis: isolation of the gene, nucleotide and amino acid sequence.

The gene coding for the ;heavy' subunit of the photosynthetic reaction centre from Rhodopseudomonas viridis was isolated in an expression vector. Expression of the heavy subunit in Escherichia coli was detected with antibodies raised against crystalline reaction centres. The entire subunit, and not a fusion protein, was expressed in E. coli. The protein coding region of the gene was sequenced and the amino acid sequence derived. Part of the amino acid sequence was confirmed by chemical sequence analysis of the protein. The heavy subunit consists of 258 amino acids and its mol. wt. is 28 345. It possesses one membrane-spanning alpha-helical segment, as was revealed by the concomitant X-ray structure analysis.

Journal Article↗
PubMed1985

Percutaneous measurement of portal blood flow in the piglet by continuous thermodilution.

The continuous thermodilution method was applied to the percutaneous measurement of portal blood flow in the piglet by inserting a thermodilution probe into the portal vein via the transhepatic transvenous route. The method was compared to electromagnetic flowmetry in three piglets; the two methods yielded statistically identical results. The coefficient of variation of the continuous thermodilution measurements was 4%. The method allows portal blood flow measurements that are instantaneous, reliable, reproducible, and repetitive. It was applied to a study of rapid flow variations in piglets receiving an infusion of posterior pituitary extract.

Animals↗
PubMed1985

Treatment of acute hepatic encephalopathy in cirrhotics with a branched-chain amino acids enriched versus a conventional amino acids mixture. A controlled study of 70 patients.

Acute hepatic encephalopathy in 70 cirrhotic patients was monitored during parenteral administration of amino acids between January 1979 and January 1984. The diagnosis of cirrhosis was confirmed by needle biopsy, and HE by conventional clinical and EEG parameters. The infusion of AA solutions was initiated 48 h after admission and during a 5-day period: 34 patients received a control aminoacid solution, a commercially available AA mixture (Azonutril), and 36 patients a modified solution enriched in BAA prepared from crystallized AA dissolved in distilled water. The calorie intake for both groups was 1600 calories per day from glucose and lipid emulsion. No significant difference was noted based on clinical evolution, even though the plasma AAA/BAA ratio was corrected using the modified AA solution. Of the 34 patients in Group 1: 10 improved, 14 were unchanged, 10 deteriorated and 7 died. Of the 36 patients in Group 2: 12 improved, 14 were unchanged, 10 deteriorated and 7 died. EEG tracing evolved in parallel fashion. The authors conclude that modified AA solutions are ineffective in the treatment of acute hepatic encephalopathy in cirrhotic patients.

Acute Disease↗
PubMed1985

[Sclerosing cholangitis following surgical treatment of hydatid cysts of the liver. Probable role of the formol injection of bile ducts].

Three cases of secondary sclerosing cholangitis which developed during the early postoperative phase of surgical treatment of hydatid liver cysts are reported. The cysts had ruptured into the biliary tree and the treatment consisted of infection of formol into the cysts. Evolution was pejorative since one patient died within 3 months and the remaining two underwent liver transplantation following biliary sclerosis. An experimental protocol using dogs has shown that the injection of 5, 10 and 20 p. 100 formalin into normal bile ducts rapidly causes sclerosing cholangitis which often leads to death. In man, it is very likely that the contact of 2 p. 100 formalin with mucosal tissue damaged by episodes of cholangitis could result in sclerosing cholangitis. These observations should be sufficient to discourage the use of formalin to sterilize hydatid cysts of the liver.

Adolescent↗