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Biomedical subjects

J P Leblanc

Publications and source records attributed to J P Leblanc.

At least 19 recordsLinked to original sources
PubMed1999

Analysis of time management in stroke patients in three French emergency departments: from stroke onset to computed tomography scan.

The aim of this study was to determine and identify the factors associated with shortening or lengthening time interval from stroke onset to performance of computed tomography (CT) scan in stroke patients admitted to three French emergency departments. All suspected stroke patients were eligible (n = 317). The time intervals between stroke onset and presentation to the emergency department and between CT scan request and CT scan performance were determined. Twelve variables likely to influence time interval before presentation to the emergency department, and five variables likely to influence time interval before CT scan performance were evaluated using stepwise regression analysis. Of the 317 patients included in the study, the mean time interval from stroke onset to CT scan performance for 180 patients was 7 hours 46 minutes (466 minutes). The mean time interval between stroke onset and presentation to the emergency department was 4 hours 36 minutes (276 minutes), varying according to the study site, level of initial severity, medical contact before admission, witnesses at stroke onset, and mode of transportation. The mean time interval between request and CT scan performance was 2 hours 14 minutes (134 minutes), varying upon the site, hour of CT scan request, type of stroke and level of severity at admission. It is concluded that current delays in stroke management are often incompatible with early treatment. The public needs to be informed and admission procedures reorganized. Improved response to the urgency of ischaemic stroke is required as well as direct access to the scanner during periods of scheduled use.

Aged↗
PubMed1998

Genetic determinants of Pseudomonas aeruginosa colonization in cystic fibrosis patients in Canada.

The present study was aimed at analyzing whether the rate of colonization and the age at colonization with Pseudomonas aeruginosa was genetically determined in cystic fibrosis (CF) patients. These two variables were calculated among 127 CF patients whose genotypes were known and who were monitored at the Clinique de Fibrose Kystique in Saguenay Lac-Saint-Jean. No statistically significant differences were found in the rate or the age at colonization when the patients were grouped by genotype; however, this result could be due to the small number of patients in each genotype group. The rate of colonization was significantly lower among CF patients carrying the A455E mutation, a "mild" allele with respect to exocrine pancreatic function, than among those carrying either the deltaF508 or the 621 + IG- > T mutation, both of which are "severe" alleles. The results confirm previous reports that the rate of colonization with Pseudomonas aeruginosa is, at least in part, genetically determined.

Adolescent↗
PubMed1998

Correlation of sweat chloride concentration with genotypes in cystic fibrosis patients in Saguenay Lac-Saint-Jean, Quebec, Canada.

OBJECTIVES: Saguenay Lac-Saint-Jean, a geographically isolated region of northeastern Quebec has a high incidence of cystic fibrosis (CF) and three mutations only account for 94% of the CF chromosomes. The objective of the present study was to determine whether different mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene had different effects upon the sweat chloride concentration. DESIGN AND METHODS: The sweat chloride concentration of 114 patients was measured by quantitative pilocarpine iontophoresis. RESULTS: CF patients carrying the A455E mutation, usually associated with pancreatic sufficiency, had lower sweat chloride concentrations than those carrying mutations associated with pancreatic insufficiency (delta F508 and 621 + 1G-->T). CONCLUSIONS: Our results confirm that mutations resulting in a reduction of the chloride current at the apical membrane of epithelial cells induce lower sweat chloride values. However, there are differences in the chloride current between genotypes, even if they are composed of mutations apparently having the same functional effect.

Chlorides↗
PubMed1998

Complete identification of cystic fibrosis transmembrane conductance regulator mutations in the CF population of Saguenay Lac-Saint-Jean (Quebec, Canada).

Over the past few years, we have conducted a systematic study of 230 cystic fibrosis (CF) chromosomes in the Saguenay Lac-Saint-Jean (SLSJ) population which has a high CF incidence (1/936 live births). We identified 11 mutations accounting for 100% of the CF chromosomes found in patients born in SLSJ. Our results indicate that denaturing gradient gel electrophoresis (DGGE) is a powerful method of identifying CF mutations. They have also considerable implications for genetic counselling and molecular characterization of doubtful patients. They make carrier screening technically feasible in this population.

Cystic Fibrosis↗
PubMed1997

Genotype-phenotype correlation in cystic fibrosis patients compound heterozygous for the A455E mutation.

Cystic fibrosis (CF) has a high incidence in the French-Canadian population of Saguenay Lac-Saint-Jean (Quebec). The A455E mutation accounts for 8.3% of the CF chromosomes. This mutation was shown to be associated with a milder lung disease in the Dutch population. Twenty two CF patients distributed in 17 families and compound heterozygotes for the A455E mutation have been followed at the Clinique de Fibrose Kystique de Chicoutimi. Fourteen patients also carried the delta F508 mutation while the remaining eight patients had the 621 + 1G-->T mutation. Each patient was matched by sex and age to a patient homozygous for the delta F508 mutation. The pairs were analyzed for several clinical and laboratory variables. The A455E compound heterozygotes were diagnosed at a later age (P = 0.003) and had chloride concentrations at the sweat test lower than those homozygous for the delta F508 mutation (P = 0.007). More patients were pancreatic sufficient (P = 0.004). They had a higher Shwachman score (P = 0.001) and better pulmonary function tests (P < 0.02). CF patients compound heterozygous for the A455E mutation have a milder pancreatic and lung disease than the delta F508 homozygotes. Therefore, the A455E should be associated with a better prognosis.

Adolescent↗
PubMed1997

Clinical features of cystic fibrosis patients with rare genotypes in Saguenay Lac-Saint-Jean (Quebec, Canada).

We describe the clinical features of six cystic fibrosis (CF) patients from Saguenay Lac-Saint-Jean who bear rare genotypes. Two patients with a delta F508/I148T genotype had pancreatic insufficiency, as did two patients compound heterozygous for the 621 + 1G-->T mutation who also had a major growth retardation. One CF adult who carried a delta F508/Q890X genotype had meconium ileus and bronchiectasis. The sixth patient (A455E/R117C) had borderline sweat chloride concentrations; the diagnosis of cystic fibrosis had remained doubtful until the molecular analysis showed the presence of two CF mutations. The seventh patient with a delta F508/R1158X genotype experienced several complications and is now 43 years old.

Adult↗
PubMed1986

Quality criteria for chromatographic analytical systems of polyunsaturated fatty acids metabolites.

The most powerful technique for eicosanoids identification is gas chromatography prior to mass spectrometry. Results are highly dependent upon the choice of appropriate gas chromatographic systems; the critical point of the system being the quality of the column. Our work is intended to provide a general overview of open tubular capillary columns which can be used for separation, identification and quantification of eicosanoids.

Arachidonic Acid↗
PubMed1985

Excision of uracil residues in DNA: mechanism of action of Escherichia coli and Micrococcus luteus uracil-DNA glycosylases.

Various octadeoxynucleotides containing uracil at different positions were synthesized and submitted to the action of Escherichia coli and Micrococcus luteus uracil-DNA glycosylases. A uracil residue situated at the 5'-end was excised by the M.luteus enzyme but not by the E.coli one. Uracil residues located at the ultimate and penultimate positions at the 3'-end were not cleaved by either enzymes. At the other central positions, uracil was eliminated with different initial velocities. Single stranded phi X 174 DNA fragments were used to study the influence of the sequence. Cytosine bases were deaminated to give uracil by bisulfite treatment. It was shown that the initial excision velocity of two vicinal uracil residues was decreased. The same observation was made for two uracils separated by one base. A hypothetical scheme is suggested to explain the mechanism of action of uracil-DNA glycosylases.

Base Sequence↗
PubMed1982

Uracil-DNA glycosylase. Purification and properties of uracil-DNA glycosylase from Micrococcus luteus.

A uracil-DNA-glycosylase from Micrococcus luteus has been purified more than 3,000-fold. The enzyme preparation appears homogeneous, according to the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It is devoid of nonspecific endonucleases, specific endonucleases for apurinic and apyrimidinic sites, 3-methyladenine or 7-methylguanine-DNA-glycosylases. It behaves as a monomer protein of 19,400 daltons. It has an isoelectric point of 7.0 +/- 0.1. It has an optimal activity between pH 5.0 and 7.0. It has no cofactor requirement and is not inhibited by EDTA. Uracil-DNA-glycosylase is highly specific for DNA containing dUMP residues, releasing uracil as product of the reaction. It is 2-fold more active on single-stranded DNA than on double-stranded DNA. If it releases uracil dimers from ultraviolet-irradiated PBS1 DNA, it is at the threshold of the detection. The apparent Km is 7 X 10(-8) M, and uracil acts as a noncompetitive inhibitor with a Ki of 3.2 X 10(-4) M. Cis-syn cyclogbutadiuracil also is a potent inhibitor, while some analogs, produced by x-irradiation of uracil and thymine, are weak inhibitors. Spermine, between 10 and 400 microM, increases the enzymatic activity by 50% and is not inhibitory at other concentrations. Spermidine activates the enzyme at concentrations of 40 to 120 microM, but becomes inhibitory at 200 and 400 microM. A new finding is that drugs which intercalate in DNA, such as ethidium bromide and ellipticine, cause a 2- to 2.5-fold activation of this enzyme activity. The concentrations giving maximal activation depend on the drug. The enzyme does not behave as a processive enzyme during uracil excision.

DNA↗
PubMedDate not supplied

Comparison at the molecular level of uracil-DNA glycosylases from different origins.

A nuclear and a cytoplasmic uracil-DNA glycosylase have been purified from epithelial cells derived from a rat hepatoma (H4 cells) cultured in vitro. They have different optimum pH, molecular weight, isoelectric points, activation energy, Km. Uracil acts as a non competitive inhibitor towards the nuclear enzyme while it is a competitive one for the cytoplasmic enzyme. Comparison of the properties of the two mammalian enzymes with those of the enzymes isolated from Escherichia coli and Micrococcus luteus shows that they all behave differently. The following criteria were studied: molecular weight, optimum pH, isoelectric point, inhibition by uracil analogs, modulation of their activity by polyamines or by intercalating drugs. The only common properties shared by these four enzymes are: an activity twice as high on single stranded DNA than on double stranded DNA and no requirement for divalent cation for maximal activity.

Animals↗
PubMedDate not supplied

Phenotypic variability in five cystic fibrosis patients compound heterozygous for the Y1092X mutation.

Five cystic fibrosis (CF) patients distributed in three families and compound heterozygotes for the Y1092X mutation have been followed for a period ranging from 5 to 20 years. The genealogical reconstruction identified a common ancestor couple to all 3 families at the 5th generation. All 5 patients were pancreatic insufficient. A high variability in the clinical aspects and pulmonary function was seen between the families, but not within. Based on our observations, it will be very difficult to predict the course of disease for CF patients with the Y1092X mutation, even if they are closely related (first-degree cousins).

Adolescent↗