PubMed Health⌕ Search

Biomedical subjects

N Houdret

Publications and source records attributed to N Houdret.

At least 37 records · Page 2Linked to original sources
PubMed1989

Evidence for the in vivo degradation of human respiratory mucins during Pseudomonas aeruginosa infection.

The comparison of distribution of glycopeptides of sputa from patients suffering from various chronic hypersecretions has already shown an increased acidity with a decreased proportion of neutral glycopeptides in the respiratory secretions of patients suffering from cystic fibrosis, as compared to those of patients with chronic bronchitis. In order to find out whether this decrease is specific to cystic fibrosis mucins or whether it is due to a degradation of mucus by Pseudomonas aeruginosa, which infects most of the sputa from patients with this disease, mucus glycopeptides from patients with different chronic bronchial disorders, infected by Pseudomonas or not, were prepared and fractionated by ion-exchange chromatography. The neutral fraction, which has never been studied in detail, was gel-filtered, and provided two fractions, one containing true mucin glycopeptides and the other containing a mixture of peptides and glycopeptides with a lower molecular mass. In the Pseudomonas-infected samples, the true mucin glycopeptide fraction was greatly diminished as compared to this same fraction in non-Pseudomonas-infected samples; this was not specific to cystic fibrosis secretions. In contrast, the glycopeptide fraction with a lower molecular mass was greatly increased in all the Pseudomonas-infected samples. Polyacrylamide gel electrophoresis of this second fraction showed unique glycopeptide bands between 40-50 kDa in the Pseudomonas-infected samples, regardless of the origin of the samples. These bands were revealed by an antibody directed against whole cystic fibrosis mucin. Infected chronic bronchitis sputa and cystic fibrosis samples without P. aeruginosa did not show these bands. These studies therefore suggest that there are P. aeruginosa-associated changes in mucins which may result from degradation of mucins.

Amino Acids↗
PubMed1989

Differences in adhesion of Pseudomonas aeruginosa to mucin glycopeptides from sputa of patients with cystic fibrosis and chronic bronchitis.

Pseudomonas aeruginosa is the most prominent colonizer of the respiratory tract of patients with cystic fibrosis, but it is not known why this occurs. P. aeruginosa adheres to mucins from normal individuals, but mucins from cystic fibrosis patients have not been studied. To compare adhesion to mucins from cystic fibrosis with other mucins, we prepared highly glycosylated mucin glycopeptides from cystic fibrosis and chronic bronchitis patients by ion-exchange and gel-filtration chromatography and measured the adhesion of P. aeruginosa 1244 to these glycopeptides. We found (i) that the most mucinlike glycopeptides from P. aeruginosa-infected cystic fibrosis sputa showed less bacterial adhesion than did the corresponding bronchitis samples, (ii) that the most adhesive activity in cystic fibrosis samples came from a fraction that contains O and N glycopeptides and may be in part a degradation product of P. aeruginosa infection, and (iii) that highly glycosylated glycopeptides of the most acidic species (sialylated and sulfated) showed no adhesion at all. A single cystic fibrosis sample not infected by P. aeruginosa showed better binding in the adhesion-positive fractions than did the infected sputa. These studies suggest that cystic fibrosis mucins may be altered after infection is established, resulting in less binding to some fragments. However, since the clinical picture shows heavy mucus colonization, other receptors, such as cellular glycolipids which have been shed into mucus, may be contributing to this colonization.

Bacterial Adhesion↗
PubMed1988

The complexity of mucins.

Mucins represent the main components of gel-like secretions, or mucus, secreted by mucosae or some exocrine glands. These high-molecular-weight glycoproteins are characterized by the large number of carbohydrate chains O-glycosidically linked to the peptide. The determination of mucin molecular weight and conformation has been controversial for several reasons: 1) the methods used to solubilize mucus and to purify mucins are different and 2) the molecules have a strong tendency to aggregate or to bind to other molecules (peptides or lipids). Recently, electron microscopy has shown the filamentous shape of most mucins and their polydisperse character which, in some secretions, might correspond to a polymorphism of the peptide part of these molecules. The recent development of high pressure liquid chromatography and high-resolution proton NMR spectroscopy has allowed major progress in the structural study of mucin carbohydrate chains. These chains may have from 1 to about 20 sugars and bear different antigenic determinants, such as A, B, H, I, i, X, Y or Cad antigens. In some mucins, such as human respiratory mucins, the carbohydrate chain diversity is remarkable, which raises many questions. Mucins are molecules located at the interface between mucosae and the external environment. The carbohydrate chain diversity might allow many interactions between mucins and microorganisms and play a major role in the colonization or the defense of mucosae.

Animals↗
PubMed1987

Peptides of human bronchial mucus glycoproteins. Size determination by electron microscopy and by biosynthetic experiments.

Secreted human bronchial mucins, directly collected from macroscopically healthy bronchial mucosa, were prepared in the presence of six proteinase inhibitors, and analysed by electron microscopy. These mucins were similar in length distribution to molecules prepared from sputum [Slayter, Lamblin, Le Treut, Galabert, Houdret, Degand & Roussel (1984) Eur. J. Biochem. 142, 209-218], although they were a little longer, their lengths ranging up to about 1,650 nm. This length corresponds to an extended mucin peptide of about 450 kDa. In order to compare these peptide lengths with the molecular size of biosynthetic precursors, an antiserum raised against trifluoromethanesulphonic acid-treated highly glycosylated regions of human bronchial mucins was used to isolate mucin precursors synthesized in explants of human bronchial mucosa during pulse-labelling with [3H]threonine or [3H]glucosamine. A main precursor labelled with [3H]threonine and with an apparent molecular mass of about 400 kDa was detected by fluorography following SDS/polyacrylamide-gel electrophoresis. This band was observed as early as 20 min; it was more intense after a 40 min chase and had disappeared after a chase period of 280 min in unlabelled medium, presumably owing to glycosylation. Much fainter bands at about 200 kDa and between 200 and 400 kDa, also labelled with [3H]threonine, were observed mainly after a 40 min chase and had disappeared after a 280 min chase. None of these bands was labelled with [3H]glucosamine, nor did they disappear after multiple treatments with immobilized lectins. After a 280 min chase, [3H]threonine-labelled material appeared in the stacking gel, which also contained [3H]glucosamine label. The results indicate that the 200-400 kDa species are mucin precursors, whose size is comparable with that obtained by electron microscopy for respiratory mucins collected directly from the macroscopically healthy bronchial mucosa.

Bronchi↗
PubMed1986

The high lipid content of respiratory mucins in cystic fibrosis is related to infection.

Seven human bronchial mucins secreted by patients suffering from chronic bronchitis or from cystic fibrosis were prepared by exclusion from a Sepharose CL-2B column in 6 M guanidinium chloride. Their behaviour in CsBr density gradient centrifugation was compared. The mucin fractions were associated with peptides and lipids, the abundance of which decreases with the buoyant density. The lipid content of the mucin fractions appears to be related to the infectious character of the bronchial secretion and seems to be independent of cystic fibrosis. The content of fatty acids remaining after delipidation of mucin fractions from patients with chronic bronchitis or with cystic fibrosis also appears to be related more to the purulent character of the sputum than to cystic fibrosis or chronic bronchitis.

Bronchi↗
PubMed1986

High performance liquid chromatographic determination of paracetamol in human serum.

A method has been developed for the determination of acetaminophen in human serum. Samples are extracted with ethyl acetate. Beta-hydroxyethyl theophylline is used as internal standard. The solvent is evaporated under nitrogen and the residue is analyzed by high-performance liquid chromatography on Lichrosorb RP 18. Extraction efficiency, linearity and assay precision have been determined. The method is rapid and can be easily applied to determine the plasma level of patient having taken overdose of paracetamol.

Acetaminophen↗
PubMed1984

Complex structure of human bronchial mucus glycoprotein.

Human bronchial mucus glycoproteins or mucins were isolated from the sputum of two patients by a method avoiding reducing agents and involving water extraction and gel filtration on Sepharose CL-2B in 6 M guanidinium chloride. The chemical analysis indicated approximately 25-40% lipid. The amino acid and carbohydrate analysis differ quantitatively from that of mucins purified after prior reduction of mucus. These fractions also have a higher proportion of aspartic and glutamic acids than that of the mucins from reduced sputum. These mucins are still contaminated by small amounts of peptides but do not seem to contain disulfide-attached cross-linking protein. Human bronchial mucins have a strong tendency to form aggregates except in 6 M guanidinium chloride. Electron microscopy performed with various procedures indicates the presence of both micelles and flexible threads measuring 200-1000 nm. Delipidation removes most of the micellar forms. Thereafter mucins appear mainly as polydisperse flexible extended threads and also as aggregates. These features of bronchial mucins do not fit with the generally accepted idea of mucin subunits linked by disulfide bridges (unless they are linked end to end) and alternatively favour a model where mucin molecules behave like filaments that could easily aggregate according to the solvent system (mucin concentration, absence of dissociating conditions).

Amino Acids↗
PubMed1984

Amikacin assay: correlation between rapid bioassay, enzyme immuno-assay (EMIT) and fluoro-immuno-assay (FIA).

Three methods (rapid bioassay, enzyme immunoassay and fluoroimmunoassay) for the determination of amikacin level in serum are compared. The statistical analysis of the results show correlation coefficients equal to 0.967 (EMIT versus FIA), 0.970 (bioassay versus FIA) and 0.983 (bioassay versus EMIT). The three methods are acceptable for routine clinical use. The enzyme immunoassay adapted on a centrifugal analyzer appears to be a method of choice for laboratories with a large workload. However, the rapid bioassay described in this paper remains adequate for laboratories testing 5 to 10 sera per day.

Amikacin↗
PubMed1983

Activation of bronchial mucin proteolysis by 4-aminophenylmercuric acetate and disulphide bond reducing agents.

High molecular weight bronchial glycoproteins, as nearly native as possible, were treated with either 2-mercaptoethanol or 4-aminophenylmercuric acetate (APMA): analytical electrophoresis revealed that a decrease in molecular weight of glycoproteins coincided with the disappearance of some proteins associated with high molecular weight bronchial glycoproteins. These modifications were not observed if high molecular weight bronchial glycoproteins were incubated with paramethylsulphonyl fluoride and EDTA, two synthetic protease-inhibitors, prior to 2-mercaptoethanol or APMA action. These data suggest that protease-antiprotease complexes are associated with bronchial mucins and that reducing agents or APMA activate proteases.

Bronchi↗
PubMed1981

Comparative action of reducing agents on fibrillar human bronchial mucus under dissociating and non-dissociating conditions.

Gel=like or fibrillar human bronchial mucus was reduced with mercaptoethanol under dissociating and non-dissociating conditions. Bronchial mucus was solubilized in both conditions; but reduction in phosphate buffer induced more extensive depolymerization of mucus glycoproteins than obtained under reduction in guanidine. Moreover, mucins prepared by reduction in non-dissociating conditions contained less amino acid and more carbohydrate. These data strongly suggest that reduction under non-dissociating conditions does not act only on disulfide bridges but also induces the activation of a mucolytic enzymatic system. They also would explain some of the discrepancies observed in the molecular weight determination and chemical composition of human bronchial mucus glycoproteins purified after reduction of gel-like mucus under different conditions.

Bronchi↗
PubMed1979

[Adaptation to Gemsaec centrigugal analyser of a method of turbidimetric estimation of amylase (author's transl)].

Hydrolysis of a solution of amylopectin by serum or urinary amylase leads to a reduction of the turbidity of this solution, observed at 340 nm. Adapted to centrifugal analysis, this method permits 15 estimations in 3 minutes with a serial reproducibility of 2.7 per cent, and a daily reproducibility of 6 per cent. The correlation with a nephelemetric method of estimation gives r = 0,969, with an enzyme method r = 0,957 and with an amyloclastic method, r = 0,919.

Amylases↗