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J Bergeron

Publications and source records attributed to J Bergeron.

At least 109 records · Page 6Linked to original sources
PubMed1994

Identification and mapping of the gene translation products involved in the first steps of the Comamonas testosteroni B-356 biphenyl/chlorobiphenyl biodegradation pathway.

In this study, we have mapped Comamonas testosteroni B-356 genes encoding enzymes for the conversion of biphenyl and 4-chlorobiphenyl into the corresponding meta-cleavage compounds onto a 6.3-kb DNA fragment, and we have determined the subunit composition of the enzymes involved in this pathway. The various proteins encoded by this 6.3-kb DNA fragment and by subclones derived from it were overexpressed and selectively labelled using the T7 polymerase promoter system in Escherichia coli. They were then analyzed using SDS-PAGE, which allowed the encoding locus of each polypeptide to be mapped. Despite apparent dissimilarity in the congener selectivity patterns of the initial oxygenase of strain B-356 with those of Pseudomonas sp. strain LB400, the number and sizes of the polypeptides involved in the enzymatic conversion of biphenyl or 4-chlorobiphenyl into the meta-cleavage product appear to be similar in the two strains. In both strains, the bph operon encodes the following: the large (51-kDa polypeptide encoded by bphA) and the small (22-kDa polypeptide encoded by bphE) subunits of the iron sulphur protein, which is thought to interact directly with the substrate to introduce the oxygen molecule; the ferredoxin (12-kDa polypeptide encoded by bphF) involved in electron transfer from the reduced ferredoxin reductase to the oxidized iron sulphur protein; the 29-kDa polypeptide of the 2,3-dihydro-2,3-dihydroxybiphenyl dehydrogenase encoded by bphB; and the 32-kDa polypeptide of the 2,3-dihydroxybiphenyl-1,2-dioxygenase encoded by bphC, which catalyzes meta-1,2 fission of the aromatic ring. A major difference between strain B-356 and strain LB400 is that the bphG gene encoding biphenyl dioxygenase ferredoxin reductase is located outside the bph gene cluster in strain B-356. Several lines of evidence indicate that bphG is absent in clones carrying the bph operon from strain B-356.

Base Sequence↗
PubMed1994

Importance of primer selection in the application of PCR technology to the diagnosis of bovine leukemia virus.

The polymerase chain reaction (PCR) was used to detect bovine leukemia virus in bovine blood samples. When applied to leucocytes extracted from the blood samples, the standard method of DNA extraction gave good correlation with agar gel immunodiffusion, but a method in which 5 microliters of blood was the starting material was unreliable. Selection of the primers was important, and differences in results were observed when the PCR method was applied to blood samples from different geographic areas. The sensitivity varied from 50% to 90%, depending on the primer set applied to the gag gene of proviral nucleic acid. This variation was based on geographic origin of the cattle, suggesting an influence of viral strain. In some areas, more than 1 primer may needed to optimize results.

Animals↗
PubMed1993

Increased PCR sensitivity by using paraffin wax as a reaction mix overlay.

The use of mineral oil as a reaction mix overlay in conventional PCR may lead to problems. In addition to more difficult handling, traces of mineral oil in amplicon suspensions have been shown to decrease the efficiency of post-PCR manipulations. Commercial alternatives aimed at resolving the problem more than double the cost of an amplification. This is an important drawback when dealing with a large number of clinical samples. The use of inexpensive paraffin wax as a reaction mix overlay eliminated problems associated with the presence of mineral oil while being more practical and safer in handling potentially contaminated clinical samples. Moreover, when used in conjunction with a modified hot start technique, the use of paraffin wax increased the specificity and sensitivity of PCR amplifications over mineral oil in similar hot start conditions. Using the aforementioned method, the increase in specificity and sensitivity has enabled specific detection of viral DNA in clinical samples which the conventional PCR method failed to detect.

Base Sequence↗
PubMed1993

Genomic organization and mapping of transcription and translation products of the NADL-2 strain of porcine parvovirus.

The NADL-2 strain of PPV was cloned into pUC19 and independent infectious clones were sequenced. This permitted a correction of published sequences and to predict a cruciform structure as an alternative to the 5'-hairpin of the "-" strand. This 5'-end structural covariance is shared with other parvoviruses of the same group and two alternative sequences ("flip" and "flop") were present in the region of the cruciform. Transcript and translation product mapping allowed the prediction of the location of the different expression signals. The 5'-startpoints of the transcripts were located at nucleotides 225 and 2035, respectively, and the polyadenylation site at nucleotides 4829-4833. This indicated that the TATA boxes at 196-TATA and 2004-AATA and the 4813-AATAAA polyadenylation sequence would be functional. Alternative splicing of capsid gene (VP) transcripts (either 2280-AG/GT or 2313-AG/GT spliced with 2386-AG/GA), to maintain or remove the first AUG (at 2287) in the ORF, yielded two 2.9-kb mRNAs containing a nested set of protein-coding sequences (VP-1 and VP-2 with predicted molecular mass 80.9 and 64.3 kDa, respectively). Three nonstructural (NS) protein gene transcripts were identified. The 4.7-kb transcript was not spliced in the NS gene and was predicted to code for a 75.5-kDa protein (NS-1; published value of phosphorylated form 84 kDa). The splicing sites of two different 3.3-kb NS transcripts were analyzed. These transcripts were predicted to code for the NS-2 protein (18.1 kDa). Of the two NS-2 transcripts, one had also the VP-intron removed downstream of the NS-2 coding sequences. A 2.9-kb transcript would code for an NS-3 protein (12.4 kDa) although such a protein has not been described before. A flow chart of the information from the viral DNA to the viral proteins is presented and several differences, both for the NS and the VP genes, with closely related parvoviruses are noted.

Amino Acid Sequence↗
PubMed1992

Geographic distribution and genealogy of mutation 207 of the lipoprotein lipase gene in the French Canadian population of Québec.

Mutations in the lipoprotein lipase (LPL) gene, leading to partial or total inactivation of the enzyme, result in a hereditary clinical syndrome called familial LPL deficiency. The French Canadian population, which is primarily and historically located in the province of Québec, has the highest worldwide frequency of LPL-deficient patients. We have analyzed the prevalence, spatial distribution, and genealogy in the Québec population of a LPL gene mutation, M-207 (P207L in conventional notation), which changes the amino acid proline to leucine in position 207 of the LPL protein and inactivates the enzyme. Our results show that M-207 is the most prevalent LPL gene mutation among French Canadians and accounts for the largest proportion of LPL-deficient patients in this population. Genealogical reconstruction of French Canadian LPL-deficient patients point to 16 founders of M-207, all of whom migrated to Québec in the early seventeenth century from the north-western part of France, especially from the region of Perche. Most of the carriers of M-207 are, at present, found in Charlevoix, Saguenay-Lac-St-Jean regions of eastern Québec. On the basis of the number of homozygote M-207 LPL-deficient patients so far identified, we estimate that there are at least 31,000 carriers of this mutation in the province of Québec. This constitutes a large pool of individuals at risk for atherosclerosis and other lipid-related diseases, since LPL deficiency is considered to be a significant contributing factor in the etiology and development of these diseases.

Alleles↗
PubMed1992

Prevalence, geographical distribution and genealogical investigations of mutation 188 of lipoprotein lipase gene in the French Canadian population of Québec.

Familial lipoprotein lipase deficiency (FLD) is of particular interest to the French Canadian population of Québec since the largest concentration of homozygotes and carriers of this genetic disease in the world resides in this area. We have previously described a missense mutation (M-188) in the lipoprotein lipase (LPL) gene which was present in FLD patients belonging to different ancestries, including a number of French Canadians (Monsalve MV et al. J Clin Invest 1990: 86: 728-734). In the present report, we show that this mutation, although found in largest absolute numbers among French Canadians as compared to other groups in the world, accounts for only a small proportion (24%) of all the LPL mutant alleles in this population. The M-188 occurs either in the homozygote state or as a compound heterozygote with another LPL mutation. Analysis of geographic distribution indicates that the M-188 is more prevalent in western Québec, with the highest carrier rate in the Mauricie region. Genealogical reconstruction leads to the recognition of four founders for M-188, all emigrants from France to Québec in the 17th century.

Base Sequence↗
PubMed1991

[Exposure to the risk of traffic accidents, a fundamental epidemiological parameter, and one difficult to measure].

This is a review of the literature dealing with exposure to the risk of traffic accidents. We present the principal definitions of this concept, the different measures of risk exposure, indicators of the risk of traffic accidents, and the advantages and disadvantages of the methods used for the collection of data. The validity of the measure of exposure to risk is analyzed as well. We conclude that while distance travelled is the principal measure of exposure to risk accepted by the research community, it is necessary to use a composite measure which also takes into account the risk associated with the driver.

Accidents, Traffic↗
PubMed1990

Specificity of octopine uptake by Rhizobium and pseudomonas strains.

The octopine-utilizing strain Agrobacterium tumefaciens B6S3 and three nonagrobacteria which had the capacity to utilize this opine were compared for octopine uptake. The characteristics of uptake by Rhizobium meliloti A3 and strain B6S3 were similar. In both bacteria, uptake activity was inducible by octopine and by the related opine octopinic acid, and competition assays showed that these two opine substrates were accepted by the same uptake system with an equivalent affinity. Cells of Pseudomonas putida 203 accumulated octopine against a concentration gradient, and this activity was induced specifically by octopine. While strain 203 did not utilize octopinic acid, a spontaneous mutant with a combined capacity for octopine and octopinic acid utilization was obtained. Both opines induced octopine uptake by this mutant, but octopinic acid was not a substrate for the induced system. Thus, the Pseudomonas uptake system exhibited a different specificity for octopine than the corresponding Agrobacterium system. The nonfluorescent pseudomonad GU187j, which utilized the three related opines octopine, octopinic acid, and nopaline, was constitutive for octopine uptake. Strain GU187j possessed a system which accepted these three opines, but not arginine or ornithine, with a similar affinity.

Journal Article↗
PubMed1989

Determination of free testosterone fraction of human serum by gel bead dialysis.

The gel bead dialysis technique is an application of the steady-state gel filtration method. Preswollen gel beads are used as microdialysers. The gel is incubated for 3.5 h at 22 degrees C with 2.5 mL of serum and 3H-testosterone. During incubation, the equilibrium between free and protein-bound fractions is reached and the concentration of testosterone in the bead dialysate is equal to the free testosterone concentration in the incubation medium surrounding the beads. After incubation, the gel is separated from the medium by using a rigid filter and the radioactivity within the gel is counted. The effect on the assay of serum dilution and incubation time were studied. Within-batch imprecision (CV) was 3% (N = 30) and between-batch imprecision computed from lyophilized quality controls run over a one year-period, was 7%, 13% and 17% for free testosterone fractions (free over total) of 0.043, 0.032 and 0.021 respectively. An excellent correlation between this technique and the equilibrium dialysis method was found (r = 0.944, N = 59). Reference intervals were determined for men, women and pregnant women; mean +/- SD were 0.0216 +/- 0.0067 (N = 20), 0.0106 +/- 0.0020 (N = 20) and 0.0077 +/- 0.0017 (N = 19) respectively. Patients suffering from polycystic ovary syndrome had significantly higher free testosterone ratio (mean of 0.0285 +/- 0.0074, N = 20) than normal females.

Adolescent↗
PubMed1988

Escape from the down-regulation of the pituitary-ovarian axis following decreased infusion of luteinizing hormone-releasing hormone agonist.

In order to suppress the pituitary-ovarian axis for treatment of endometriosis, the luteinizing hormone-releasing hormone (LH-RH) agonist buserelin (Hoechst Canada Inc., Montreal, Quebec, Canada) was administered by continuous subcutaneous (SC) infusion using an osmotic minipump system. The down-regulation of gonadotropin release was confirmed by the absence of LH and follicle-stimulating hormone (FSH) stimulation at pump change every 2 weeks. Between week 3 and week 8 of treatment, a marked decrease in the urinary excretion of buserelin coincided with an increase in serum gonadotropins and estradiol (E2) in four patients. Following pump change, gonadotropins were stimulated and follicular cysts were observed at ultrasound examination. Serum progesterone (P) was in the luteal phase range in two cases. The suppression was re-established when the buserelin/creatinine ratio in the urine had re-increased. Otherwise, the pumping rate was doubled. Menopausal symptoms temporarily disappeared during the ovarian stimulation. A moderate uterine bleeding occurred when E2 suppression was reestablished. These observations show a rapid recovery of the pituitary-ovarian response to LH-RH agonist following a short period of a reduced infusion rate. In a slow release system, the constant delivery of an effective dose is required for the maintenance of suppression and for the avoidance of a possible hyperstimulation.

Buserelin↗
PubMed1985

Synthesis and release of plasminogen activator by lymphoid cell lines of malignant origin and its effect on lymphocyte cytotoxicity.

Lymphoid B, T. Null and plasma cell lines of malignant origin were evaluated for their ability to produce plasminogen activator (PA) in the 125I-fibrinolysis assay. These cell lines produced PA at varying extent. PA was detected in cell-free conditioned medium as well as in cell lysates. The fibrinolysis due to PA was dependent on the presence of plasminogen in the medium. PA purified by affinity chromatography not only abrogated cytotoxicity of peripheral blood lymphocytes significantly, but also the lysis of autologous EBV-transformed cells by in vitro generated cytotoxic lymphocytes. These results indicate that PA produced by malignant cells could inhibit host cellular immunity, thus providing the tumor cells with an escape mechanism from host defences.

Burkitt Lymphoma↗
PubMed1984

Purified plasminogen activating factor produced by malignant lymphoid cells abrogates lymphocyte cytotoxicity.

Immunosuppression is a generally observed phenomenon in patients with malignancies. Here we report that plasminogen activating factor (PAF) produced by human (P3HR-1) and simian (B95-8) lymphoid cells of malignant origin abrogates lymphocyte cytotoxicity. PAF has been purified from Epstein-Barr (EB) virus genome carrying lymphocyte cytotoxicity. PAF has been purified from Epstein-Barr (EB) virus genome carrying lymphoid lines by affinity chromatography using lysine-Sepharose columns. Purified PAF consistently inhibited Killer cell activity against the following targets: K-562, EB virus superinfected Raji cells and in vitro EB virus transformed autologous B lymphocytes. Furthermore PAF also inhibited the antibody-dependent cellular cytotoxicity. The results presented also indicate that PAF affects the effector lymphocytes and not the target cells. Taken together, these observations emphasize the importance of factors such as PAF, released by malignant cells, as inhibitors/modulators of immune mechanisms effective against tumour cells.

Animals↗