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Biomedical subjects

M Vignon

Publications and source records attributed to M Vignon.

At least 19 recordsLinked to original sources
PubMed2001

Measurement of the radiological hip joint space width. An evaluation of various methods of measurement.

OBJECTIVE: To determine the most relevant method of measurement of the radiographic hip joint space width (JSW). DESIGN: Seventy hips were examined from 36 patients of the ECHODIAH study having had one to four X-rays of the pelvis during the 3-year course of the study. Minimum interbone distance (MIDc), mean width of both the whole joint space (MJSWL) and a region of interest of the joint space (MJSWroi) were measured using computerized analysis of digitized radiographs. MID was also measured using a graduated eyepiece (MIDge). Reproducibility of the measurement was assessed by the intraclass coefficient of correlation. Sensitivity to change was evaluated by the standardized response mean. RESULTS: The intraobserver intraclass coefficient of correlation of MIDc and MJSWroi was 0.98 and 0.94, respectively. The mean value degrees S.D. of MJSWL, MJSWroi, MIDc and MIDge was 3.3 degrees 0.9, 2.6 degrees 0.9, 2.4 degrees 0.9 and 2.6 degrees 1.2 mm, respectively. MIDge was significantly larger than MIDc (mean difference: 0.21 degrees 0.62 mm, P<0.001), in both normal and osteoarthritic hips. However, the difference between MIDge and MIDc varied largely when considering topography of femoral head migration. Whatever the method was, a significant (P<0.001) mean decrease of nearly 0.5 mm was found in osteoarthritic hips over the 3 year follow-up. The standardized response mean for MJSWL, MJSWroi, MIDge and MIDc was 0.73, 0.75, 0.79 and 0.85, respectively. Superiority of MIDc, in term of sensitivity to change, was mainly seen in osteoarthritic hips showing a superomedial or a concentric migration of the femoral head. CONCLUSION: Minimum interbone distance measured with a computer assisted method is suggested as the most suitable method for the evaluation of hip osteoarthritis (OA) progression.

Female↗
PubMed2000

Involvement of Gln937 of Streptococcus downei GTF-I glucansucrase in transition-state stabilization.

Multiple alignment of deduced amino-acid sequences of glucansucrases (glucosyltransferases and dextransucrases) from oral streptococci and Leuconostoc mesenteroides has shown them to share a well-conserved catalytic domain. A portion of this domain displays homology to members of the alpha-amylase family (glycoside hydrolase family 13), which all have a (beta/alpha)8 barrel structure. In the glucansucrases, however, the alpha-helix and beta-strand elements are circularly permuted with respect to the order in family 13. Previous work has shown that amino-acid residues contributing to the active site of glucansucrases are situated in structural elements that align with those of family 13. In alpha-amylase and cyclodextrin glucanotransferase, a histidine residue has been identified that acts to stabilize the transition state, and a histidine is conserved at the corresponding position in all other members of family 13. In all the glucansucrases, however, the aligned position is occupied by glutamine. Mutants of glucosyltransferase I were constructed in which this glutamine, Gln937, was changed to histidine, glutamic acid, aspartic acid, asparagine or alanine. The effects on specific activity, ability to form glucan and ability to transfer glucose to a maltose acceptor were examined. Only histidine could substitute for glutamine and maintain Michaelis-Menten kinetics, albeit at a greatly reduced kcat, showing that Gln937 plays a functionally equivalent role to the histidine in family 13. This provides additional evidence in support of the proposed alignment of the (beta/alpha)8 barrel structures. Mutation at position 937 altered the acceptor reaction with maltose, and resulted in the synthesis of novel gluco-oligosaccharides in which alpha1,3-linked glucosyl units are joined sequentially to maltose.

Enzyme Stability↗
PubMed2000

Mutagenesis of asp-569 of glucosyltransferase I glucansucrase modulates glucan and oligosaccharide synthesis.

Glucansucrases of oral streptococci and Leuconostoc mesenteroides are enzymes of medical and biotechnological interest that synthesize alpha-glucans. They can also synthesize oligosaccharides in the presence of a sugar acceptor. Previous reports have identified an amino acid residue that may affect the structure of the glucan product; therefore, random mutagenesis of the corresponding Asp-569 of Streptococcus downei glucosyltransferase I (GTF-I) was used to further understanding of its involvement in the catalytic mechanism and to evaluate how different amino acids can modulate glucan and oligosaccharide synthesis. GTF-I variants were obtained where Asp-569 was replaced by each of the different possible classes of amino acids. These were expressed in Escherichia coli and purified by means of a His(6) tag. The results showed that the amino acid in position 569 influences the structure of the glucan and the size of the oligosaccharides produced by GTF-I. The results suggest that the amino acid occupying this position is more likely to interact with the acceptor molecules (oligosaccharides or elongating glucan chain) than to be directly involved in glucosyl transfer from sucrose. Engineering of the equivalent position in glucansucrases thus appears to be a good target to expand the range of oligosaccharides synthesized.

Amino Acid Sequence↗
PubMed1999

Isolation of key amino acid residues at the N-terminal end of the core region Streptococcus downei glucansucrase, GTF-I.

Related streptococcal and Leuconostoc mesenteroides glucansucrases are enzymes of medical and biotechnological interest. Molecular modelling has suggested that the catalytic domain contains a circularly permuted version of the (beta/alpha)8 barrel structure found in the amylase superfamily, and site-directed mutagenesis has identified critical amino acids in this region. In this study, sequential N-terminal truncations of Streptococcus downei GTF-I showed that key amino acids are also present in the first one-third of the core domain. Mutations were introduced at Trp-344, Glu-349 and His-355, residues that are conserved in all glucansucrases and lie within a region which is a target for inhibitory antibodies. W344L, E349L and H355V substitutions were assayed for their effect on mutan synthesis and also on oligosaccharide synthesis with various acceptors. It appeared that Trp-344 and His-355 are involved in the action mechanism of GTF-I; His-355 may also play a role in a binding subsite necessary for oligosaccharide and glucan elongation.

Amino Acid Sequence↗
PubMed1995

[Occupational asthma: retrospective study of a series of 144 cases].

The occupational origin of asthma is only found only late, from a diagnosis delay due to development. The aim of this work was to study the chronological characteristics of occupational asthma of different etiologies and to understand the occupational after-effects. A series of 144 cases were analysed (115 men and 29 women) who were seen in a consultation that specialised in occupational pathology, with the inclusion criteria those of the National Institute for Occupational Safety and Health (NIOSH). The analysis was based on: the causative allergen or work protocol; the role of atopy; length of the latency phase; length of symptom exposure; diagnosis delay; occupational consequences. Asthma from isocyanates and flour between them accounted for 62% in this series. These were followed by asthma from wood (8.3%) and persulphates (7.6%). The mean length of the latency period was 7.5 years and the mean diagnosis delay was 2.5 years. Clinical history of atopy and the existence of rhinitis were much more common for the "biological" than the "chemical" asthmas (respectively 69% and 95%, against 36% and 15%). Amongst the 64% of patients who benefited from complete removal of the allergen, 78.5% who were cured or improved, though for those who kept the same conditions of work there was a persistence or even aggravation of symptoms. In 74 cases a certificate of occupational illness was given to the patient.

Adult↗
PubMed1993

New surgical obturator prosthesis for hemimaxillectomy patients.

Many materials have been used to make immediate and intermediate obturator prostheses for the hemimaxillectomy patient. The weight of the obturator prosthesis is a major hindrance. A new thermoplastic material, Polysar, is described to create a hollow obturator extension for immediate and intermediate lightweight obturator prostheses.

Elastomers↗
PubMed1992

Streptococcus suis meningitis. A severe noncompensated occupational disease.

Meningitis caused by Streptococcus suis type 2, a rare disease first recognized in 1968 (108 cases worldwide in 1989), is contracted by occupational exposure to pigs and often results in very severe disabilities (definitive deafness and ataxia in 50% of cases). We report the case of an employee in a rendering plant whose initial symptom was deafness. A detailed analysis of medical and veterinary literature is provided concerning the epidemiology of the disease, the clinical forms in man, bacteriological diagnosis and the role of the pig as healthy carrier. It is recommended that this occupational disease be officially recognized for compensation in France.

Animals↗
PubMed1990

Purification and properties of an endo-1,4-xylanase excreted by a hydrolytic thermophilic anaerobe, Clostridium thermolacticum. A proposal for its action mechanism on larchwood 4-O-methylglucuronoxylan.

An extracellular xylanase from a thermophilic anaerobe, Clostridium thermolacticum, was purified 400-fold by ion-exchange chromatography and gel filtration. The purified enzyme had a specific activity of 31,670 nkat/mg of protein at 60 degrees C, a molecular mass of 39 kDa and a pI of 4.9. The enzyme exhibited maximal activity at 80 degrees C (1 h assay) and at pH 6.0-6.5. There was little loss of activity after 4 days at 60 degrees C and the enzyme was stable in the wide pH range 3-11. Examination of the hydrolysis products of larchwood xylan indicated that it was an endoxylanase; at the early stage of the reaction, xylose (Xyl)-containing oligosaccharides of 3-12 residues were released and after a prolonged incubation time, the neutral end-products were Xyl2 and Xyl3. Kinetic studies of the hydrolysis of xylose-containing oligosaccharides of 4-7 residues showed that the tetrasaccharide was hydrolysed more slowly than the pentasaccharide, while the calculated Km and V values for pentasaccharide and hexasaccharide were similar. The primary structures of the XylnGlcA produced by long-term hydrolysis of larchwood glucuronoxylan were determined on the basis of their carbohydrate composition, by methylation analysis and by 1H-NMR and 13C-NMR spectroscopies. These data allowed us to propose a model for the mode of action of this endoxylanase on larchwood 4-O-methylglucuronoxylan.

Carbohydrate Sequence↗
PubMed1989

Proof of the occurrence of 5,6-O-(1-carboxyethylidene)-D-galactofuranose units in the capsular polysaccharide of Klebsiella K12.

The 13C-n.m.r. spectra of the capsular polysaccharide of Klebsiella K41 and phage-derived oligosaccharides K41-P1 and K41-P2 were compared with spectra from the structurally similar polysaccharide of Klebsiella K12 and oligosaccharides K12-P1 and K12-P2. This led to the conclusion that K41 and K12 contain one and two galactofuranose residues per repeating unit, respectively, and that the terminal, lateral residue in K12 has the 5,6-O-(1-carboxyethylidene)-D-galactofuranose structure rather than that of a 4,6-acetal of D-galactopyranose as originally stated. This is the first reported occurrence in Nature of such a structural unit.

Carbohydrate Sequence↗
PubMed1986

Structural investigation of the capsular polysaccharide from Klebsiella K19 by chemical and N.M.R. analyses.

Sugar analysis of the capsular antigen K19 from Klebsiella and of the carboxyl-reduced derivative confirmed its classification into the chemotype containing rhamnose, galactose, glucose, and glucuronic acid residues. Partial acid hydrolysis and phage depolymerization of K19 provided respectively a modified, linear form of the polysaccharide and oligosaccharides of the repeating unit, these were used for the structural elucidation of the original polymer. Methylation analysis, Smith degradation, and 1H- and 13C-n.m.r. spectroscopy of the polysaccharide and derivatives permitted formulation of the following structure for K19: (formula; see text)

Carbohydrate Conformation↗