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Biomedical subjects

G Guillaume

Publications and source records attributed to G Guillaume.

At least 19 recordsLinked to original sources
PubMed2000

PCR typing of tetracycline resistance determinants (Tet A-E) in Salmonella enterica serotype Hadar and in the microbial community of activated sludges from hospital and urban wastewater treatment facilities in Belgium.

The distribution of tetracycline resistance determinants Tet A-E was studied by PCR in 40 tetracycline-resistant Salmonella enterica serotype Hadar (S. hadar) isolates collected from human patients in 1996 and 1997, as well as in the microbial community originating from activated sludges of hospital and urban wastewater treatment facilities. A fast DNA extraction and purification method from activated sludges was used to provide amplifiable DNA. The method is based on the direct lysis of bacteria improved by bead-beating followed by DNA purification on polyvinylpolypyrrolidone spin columns to remove PCR inhibitors. The purified DNAs from salmonellae and activated sludges were characterized for the presence of tetracycline determinants with specific primer pairs designed on the basis of published sequences. The Tet A determinant was present in all clinical isolates and DNAs extracted from the bacterial community of the selected activated sludges. The Tet C determinant was identified in only one of the 40 clinical isolates and in six of the seven environmental samples. No signal was detected for Tet B, D and E determinants. This study revealed a high and stable prevalence of the Tet A determinant in both salmonellae clinical isolates and the microbial community of activated sludges from hospital and urban wastewater treatment facilities over a 2-year period.

Journal Article↗
PubMed1999

Increase in circulating endothelial cells in patients with primary chronic venous insufficiency: protective effect of Ginkor Fort in a randomized double-blind, placebo-controlled clinical trial.

One possible mechanism that accounts for the alterations observed in varicose veins is the activation of endothelial cells by ischemia occurring in the leg veins during blood stasis and the cascade of reactions that follows. Because in vitro data suggest that endothelium alteration is a key event in the development of the pathology, it was important to confirm this hypothesis in patients. We used the number of circulating endothelial cells detached from the vascular wall as a criterion of the endothelium injury. We first compared the number of circulating endothelial cells (CECs) in patients with chronic venous insufficiency (CVI) with those of a control population. A twofold increase in the CEC count (1,001+/-127 CEC/ml of plasma compared with 514+/-82 CECs/ml) was observed in CVI patients, which indeed suggests an alteration of the endothelium in this disease. Second, the protective effect of a venotropic drug, Ginkgo biloba extract, troxerutine, and heptaminol (Ginkor Fort), was tested by a randomized double-blind, placebo-controlled clinical trial. In the active-treatment group, the mean values of the CEC count decreased by 14.5% after a 4-week treatment, whereas in the placebo group, the decrease was less (8.4%). The decrease from week 0 to the end of treatment was significantly higher in the active-treatment group than in the placebo group. These results confirm the important role of the endothelium alterations in the development of varicose veins and suggest a potential beneficial action of a venotropic drug on the venous wall.

Adult↗
PubMed1998

A collapsed intermediate with nonnative packing of hydrophobic residues in the folding of TEM-1 beta-lactamase.

The kinetics of refolding of TEM-1 beta-lactamase from solution in guanidine hydrochloride have been investigated on the manual and stopped-flow mixing time scales. The kinetics of change of far-UV circular dichroism and of intrinsic and ANS fluorescence have been compared with changes in the quenching of fluorescence by acrylamide as a probe of the accessibility of solvent to tryptophan. The binding of ANS points to hydrophobic collapse in the very early stages of folding which take place in the burst phase. This is accompanied by regain of 60-65% of native ellipticity, indicating formation of a significant proportion of secondary structure. Also in the burst phase, the tryptophan residues, which are largely exposed to solvent in the native protein, become less accessible to acrylamide, and the intrinsic fluorescence increases markedly. An early intermediate is thus formed in which tryptophan is more buried than in the native protein. Further intermediates are formed over the next 20 s. Quenching by acrylamide increases during this period, as the transient nonnative state is disrupted and the tryptophan residue(s) become(s) reexposed to solvent. The two slowest phases are determined by the isomerization of incorrect prolyl isomers, but double jump tryptophan fluorescence and acrylamide quenching experiments show little, if any, effect of proline isomerization on the earlier phases. Hydrophobic collapse thus occurs to a folding intermediate in which there is a nonnative element of structure which has to rearrange in the later steps of folding, resulting in a nonhierarchical folding pathway. The C-terminal W290 is suggested as being involved in the nonnative intermediate. beta-Lactamase provides further evidence for the occurrence of nonnative intermediates in protein folding.

Acrylamide↗
PubMed1997

Unexpected influence of a C-terminal-fused His-tag on the processing of an enzyme and on the kinetic and folding parameters.

The addition of a poly-His C-terminal extension, designed to facilitate the purification of the protein, to the beta-lactamase of a thermophilic Bacillus licheniformis strain modified the site of action of the signal peptidase. This resulted in the secretion of a protein with a different N-terminus, showing that this type of protein engineering might not always be as 'neutral' as generally assumed.

Bacillus↗
PubMed1997

Site-directed mutagenesis of glutamate 166 in two beta-lactamases. Kinetic and molecular modeling studies.

The catalytic pathway of class A beta-lactamases involves an acyl-enzyme intermediate where the substrate is ester-linked to the Ser-70 residue. Glu-166 and Lys-73 have been proposed as candidates for the role of general base in the activation of the serine OH group. The replacement of Glu-166 by an asparagine in the TEM-1 and by a histidine in the Streptomyces albus G beta-lactamases yielded enzymes forming stable acyl-enzymes with beta-lactam antibiotics. Although acylation of the modified proteins by benzylpenicillin remained relatively fast, it was significantly impaired when compared to that observed with the wild-type enzyme. Moreover, the E166N substitution resulted in a spectacular modification of the substrate profile much larger than that described for other mutations of Omega-loop residues. Molecular modeling studies indicate that the displacement of the catalytic water molecule can be related to this observation. These results confirm the crucial roles of Glu-166 and of the "catalytic" water molecule in both the acylation and the deacylation processes.

Acylation↗
PubMed1997

Kinetic and thermodynamic consequences of the removal of the Cys-77-Cys-123 disulphide bond for the folding of TEM-1 beta-lactamase.

Class A beta-lactamases of the TEM family contain a single disulphide bond which connects cysteine residues 77 and 123. To clarify the possible role of the disulphide bond in the stability and folding kinetics of the TEM-1 beta-lactamase, this bond was removed by introducing a Cys-77-->Ser mutation, and the enzymically active mutant protein was studied by reversible guanidine hydrochloride-induced denaturation. The unfolding and refolding rates were monitored using tryptophan fluorescence. At low guanidine hydrochloride concentrations, the refolding of the wild-type and mutant enzymes followed biphasic time courses. The characteristics of the two phases were not significantly affected by the mutation. Double-jump experiments, in which the protein was unfolded in a high concentration of guanidine hydrochloride for a short time period and then refolded by diluting out the denaturant, indicated that, for both the wild-type and mutant enzymes, the two refolding phases could be ascribed to proline isomerization reactions. Equilibrium unfolding experiments monitored by fluorescence spectroscopy and far-UV CD indicated a three-state mechanism (N<-->H<--U). Both the folded mutant protein (N) and, to a lesser extent the thermodynamically stable intermediate, H. were destabilized relative to the fully unfolded state, U. Removal of the disulphide bond resulted in a decrease of 14.2 kJ/mol (3.4 kcal/mol) in the global free energy of stabilization. Similarly, the mutation also induced a drastic increase in the rate of thermal inactivation.

Disulfides↗
PubMed1997

[Evaluation of dependence in the aged].

On account of the ageing of the population, the general practitioner will be more and more solicited to care for old people. The determinations of the degree of dependence of the elderly person is more a global bio-psycho-social concept than the classic view of the curative medicine. Two scales of evaluation of the state of dependence--the Katz scale and the Old People Aid scale--are commonly used in Belgium. Are they valid and do they reflect the actual recourse for aid and care? To answer the questions, this article refers to a study realized in the french community of Belgium about people older than 65 years. The analysis of the dependence degree will allow a better definition--in respect of the patient's will and choice--of the objectives and needed resources.

Activities of Daily Living↗
PubMed1991

[Chronic asymptomatic hypereosinophilia. Apropos of a case of occupational toxocariasis].

The authors observed a case of asymptomatic toxocariasis in a lady aged 60, engaged in dog-breeding since twenty years. The various causes of hypereosinophilia are discussed. The epidemiology of Toxocariasis and the essential role of serologic tests--in particular ELISA detection of a larval antigen--are recalled. In this particular case, therapeutic abstention is justified.

Animals↗
PubMed1989

[Pseudogout in a perspiring farmer].

A diagnostic argument in favour of brucellosis can be depicted in the various appearances of osteo-articular complications providing that one has at one's disposal the correct case history (exposure to contagion), some hemocultures (positive in nearly 60% of acute and subacute cases) and a battery of serological tests. Arthritis of the big toe is exceptional in this context, be it in the severe and destructive form or in the mild and transient form. The authors describe a case of this latter type in a farmer and present a review of the literature concerning the osteo-articular complications of Brucellosis.

Agricultural Workers' Diseases↗