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Biomedical subjects

H Michel

Publications and source records attributed to H Michel.

At least 271 records · Page 15Linked to original sources
PubMed1988

Tandem mass spectrometry reveals that three photosystem II proteins of spinach chloroplasts contain N-acetyl-O-phosphothreonine at their NH2 termini.

Photosystem II cores of spinach contain four phosphoproteins (8.3, 32, 34, and 44 kDa). Tryptic digestion of core particles released four phosphopeptides which were purified by affinity chromatography on Fe3+-chelating Sepharose and reverse-phase high pressure liquid chromatography. One peptide, derived from the 8.3-kDa protein, has been found to be the NH2 terminus of the psbH gene product (Michel, H. P., and Bennett, J. (1987) FEBS Lett. 212, 103-108). The other three peptides were found to be blocked at the NH2 terminus. We now report the use of tandem mass spectrometry to obtain the sequence of the three other peptides, to locate the phosphorylated residue, and to identify the blocking group. The three peptides correspond to the NH2 termini of D1, D2, and CPa-2; and each begins with N-acetyl-O-phosphothreonine. Comparison with sequences deduced from cloned genes indicates that D1 and D2 have lost their initiating N-formylmethionyl residues. The result for D1 contradicts the view that translation of D1 begins at the second AUG of the mRNA (Bloom, M., Brot, N., Cohen, B. N., and Weissbach, H. (1986) Methods Enzymol. 118, 309-315) and supports the view that processing of pre-D1 to its mature form involves loss of amino acids from the COOH terminus (Marder, J. B., Goloubinoff, P., and Edelman, M. (1984) J. Biol. Chem. 259, 3900-3908). In contrast, CPa-2 is processed at the NH2 terminus by cleaving off the first 14 amino acids. These results also establish that the NH2 termini of D1, D2, and CPa-2 are exposed to the stromal side of the thylakoids.

Amino Acid Sequence↗
PubMed1988

Cytochrome b6f complex is required for phosphorylation of light-harvesting chlorophyll a/b complex II in chloroplast photosynthetic membranes.

The light-harvesting chlorophyll a/b complex (LHC II) and four photosystem II (PS II) core proteins (8.3, 32, 34 and 44 kDa) become phosphorylated in response to reduction of the intersystem electron transport chain of green plant chloroplasts. Previous studies indicated that reduction of the plastoquinone (PQ) pool is the key event in kinase activation. However, we show here that, unlike PS II proteins, LHC II is phosphorylated only when the cytochrome b6f complex is active. Two lines of evidence support this conclusion. (1) 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and the 2,4-dinitrophenyl ether of iodonitrothymol (DNP-INT), which are known to block electron flow into the cytochrome complex, selectively inhibit LHC II phosphorylation in spinach thylakoids. (2) The hcf6 mutant of maize, which contains PQ but lacks the cytochrome b6f complex, phosphorylates the four PS II proteins but fails to phosphorylate LHC II in vivo or in vitro.

Benzoquinones↗
PubMed1988

[A cause of terminal constipation: hypertonia of the striated pelvic muscle. Value of complementary studies].

The aim of this study was to define an other cause of idiopathic constipation with a mathematic automatic classification Fifty patients were studied by colonic transit time, anorectal manometry and defecography. Three classical causes were found: 12 patients had hypertonic upper anal pressure; 8 patients had abnormal rectonanal inhibitory reflex and 12 patients had anatomic conditions reducing stool frequencies Automatic mathematic classification coming from optimised bowls technic has led to the characterization of a new cause. Eight young women (mean age 33 years) with hypertonic striated pelvic muscles on straining were identified. Three items were significantly different: defect of sphincteric relaxation without high sphincteric pressure; closure or non opening anorectal angle, hypertonic levator ani on straining. There was a significant high frequency (p less than 0.05) of urinary disorders in this new group. All abnormalities occurred during defecation. This group can be studied with other methods: balloon expulsion, anal electromyography. Clinical identity with urinary pathology may be explained by common neurologic disorders of pelvic striated muscle innervation.

Adult↗
PubMed1988

[Artificial nutrition and alcoholic cirrhosis].

Malnutrition is observed in 60 p. cent of patients with alcoholic cirrhosis. It is characterized by weight loss, hypoproteinemia, and a negative nitrogen balance. It is due to multiple causes. This malnutrition increases the risk of disturbances in the immune system, susceptibility to infection, and postoperative complications. Re-nutrition by standard methods of feeding often is inadequate or impractical. Use of artificial nutrition is often made necessary either by enteral or parenteral route. A controlled study of parenteral nutrition did not make it possible to correct weight loss and protein deficiency in these patients. Laboratory tolerability, except for increased BUN was always excellent. Enteral nutrition, easier to administer, which appears less dangerous and more natural, has not demonstrated its efficacy either.

Enteral Nutrition↗
PubMed1987

[Treatment of acute alcoholic hepatitis with prednisolone. 45 patients].

Whether or not prednisolone (or prednisone) should be used to treat alcoholic hepatitis remains controversial. This new controlled study performed on 45 patients with steatosis, fibrosis or cirrhosis of the liver suggests that prednisolone is not effective: after a 3-month follow-up clinical course, biochemical alterations, anatomical lesions and portal hypertension were the same in patients treated with prednisolone and in those who did not receive that drug.

Acute Disease↗
PubMed1987

Amino acid sequence of the cytochrome subunit of the photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis.

The complete nucleotide sequence of the gene encoding the cytochrome subunit of the photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis, and the derived amino acid sequence are presented. The nucleotide sequence of the gene reveals the existence of a typical bacterial signal peptide of 20 amino acid residues which is not found in the mature cytochrome subunit. The gene encoding the cytochrome subunit is preceded by the gene encoding the M subunit. Both genes overlap by 1 bp. The mature cytochrome subunit consists of 336 amino acid residues; 73% of its amino acid sequence was confirmed by protein sequencing work. The mol. wt of the cytochrome subunit including the covalently bound fatty acids and the bound heme groups is 40 500. The internal sequence homology is low, despite the symmetric structure of the cytochrome subunit previously shown by X-ray crystallographic analysis of the intact photosynthetic reaction centre. Sequence homologies to other cytochromes were not found.

Journal Article↗
PubMed1987

[Idiopathic constipation in children. Value of treatment by biofeedback].

Anorectal manometry was used in the training by biofeedback of children with idiopathic constipation. Fourteen children 7 to 12 years old with outlet obstruction due to sphincteric disorders were submitted to a biofeedback session. There was a good improvement in 10 of the 12 children who accepted this treatment. This result is in agreement with the data published in literature. This complementary treatment appears useful when it is well accepted by the parents and the child and when the manometric signal is well understood by the child who must be also able to apply the technique at home.

Anal Canal↗
PubMed1987

[Gastro-esophageal reflux, personality study by the Minnesota Multiphasic Personality Inventory (MMPI)].

Gastro-esophageal reflux (GER) is often associated with other functional digestive manifestations. The subjectivity of these manifestations permits an in-depth study of the personality of these patients as compared to a regional reference population with the use of the Minnesota multiphasic personality inventory. In these patients suspected to have a gastro-esophageal reflux, the means to the scales are modified except for that of the psychopathy scale, which is reassuring considering its severity. However, no personality profile may be exteriorized. The difference between patients with GER certified or not by pH measurement rests on the predominance of neurotic scales in the group presenting a gastro-esophageal reflux certified by pH measurement. This results appears to be due to the disease itself rather than to the conditions of performance of the MMPI during pH measurement. Only a pre- and post-therapeutic study will enable to confirm these data.

Adult↗
PubMed1986

[Pancreatic pseudo-tumor caused by bilio-pancreatic tuberculous lymphadenitis. 2 cases].

Peripancreatic tuberculous lymphadenitis is rare and of difficult diagnosis. The two cases described illustrate two clinical aspects according to the proximity of the biliary tract: either anterior lymph nodes responsible for obstructive jaundice, or posterior lymph nodes responsible for chronic epigastric pain. Endoscopic retrograde cholangiopancreatography is essential to exclude a pancreatic lesion and facilitate the interpretation of the CT images. Tuberculosis must then be suspected. In the absence of another tuberculous localisation, laparotomy is necessary to assert the diagnosis. Antituberculous chemotherapy alone, administered for 9 to 12 months, cures this form of tuberculous lymphadenitis.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1986

[Systemic scleroderma. Contribution of esophageal manometry].

Oesophageal motor function was studied by oesophageal manometry in 48 patients with progressive systemic sclerosis: 25 with proximal scleroderma and 23 with diffuse scleroderma. Oesophageal lesions were noted in 70% (74% in diffuse scleroderma; 64% in proximal scleroderma). Classical manometric signs of scleroderma were found in only 31% of patients. Peristaltic modifications might begin at the junction of the two muscular coats, since a four centimeter long aperistaltic suspended area was noted in that region in 20% of patients, especially in the proximal scleroderma group. Oesophageal motility and low lower oesophageal sphincter pressure account for the gastro-oesophageal reflux and may compromise respiratory function, as suggested by the high frequency of concurrent oesophageal and respiratory dysfunction in diffuse scleroderma. Systematic prevention of gastro-oesophageal reflux should perhaps be advocated as soon as abnormalities in oesophageal motility are diagnosed.

Adolescent↗