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B Lemieux

Publications and source records attributed to B Lemieux.

At least 37 records · Page 2Linked to original sources
PubMed1997

Screening for neuroblastoma is ineffective in reducing the incidence of unfavourable advanced stage disease in older children.

Neuroblastoma exhibits many characteristics which would suggest that preclinical detection may improve outcome. The Quebec Neuroblastoma Screening Project was initiated to determine whether mass screening could reduce mortality in a large cohort of infants. All 476,603 children born in the province of Quebec during a 5-year period of time (1 May 1989 to 30 April 1994) were eligible for determinations of urinary catecholamine metabolites at 3 weeks and 6 months of age. Children with positive screening were referred to one of four paediatric cancer centres in Quebec for uniform evaluation and treatment. Standardised incidence ratios (SIRs) were calculated for neuroblastoma in Quebec and two comparable population-based controls during the same period of time using similar ascertainment procedures. Compliance with screening in Quebec was 91% at 3 weeks (n = 425,816) and 74% at 6 months (n = 349,706). Up to 31 July 1995 with a follow-up of the birth cohort of 15-75 months, 118 cases of neuroblastoma were diagnosed, 43 detected preclinically by screening, 20 detected clinically prior to screening at 3 weeks of age and 55 detected clinically after 3 weeks of age having normal screens (n = 52) or never screened (n = 3). Based on data from concurrent control populations, 54.5 cases of neuroblastoma would have been expected in Quebec during the study period for an SIR of 2.17 (95% CI 1.79-2.57, P < 0.0001). For the two control groups, the overall SIR was 1.00 (NS). SIRs for Quebec by age at diagnosis in yearly intervals show a marked increased incidence under 1 year of age (SIR = 2.85, 95% CI 2.26-3.50), with no reduction in incidence in subsequent years. We conclude that screening for neuroblastoma markedly increases the incidence in infants without decreasing the incidence of unfavourable advanced stage disease in older children. It is unlikely that screening for neuroblastoma in infants will reduce the mortality of this disease.

Canada↗
PubMed1997

Mapping expressed sequence tag sites on yeast artificial chromosome clones of Arabidopsis thaliana DNA.

We describe a method for efficient parallel mapping of expressed sequence tag (EST) sites onto yeast artificial chromosome (YAC) clones. The strategy involves an initial YAC clone pooling scheme that minimizes the number of required PCR amplifications. This is followed by parallel analysis of PCR amplicons of EST sequences. Using this method, we have screened 600 EST sites in combinatorial pools of 3449 YAC clones that contain Arabidopsis thaliana DNA inserts. The presence of these genes on YACs was detected by amplifying EST sequences with PCR and analyzing the reaction products by agarose gel electrophoresis. Of the 600 ESTs, 271 were found to map to individual YACs. Software tools are presented that allow for the automated analysis of this electrophoresis data. Suggestions for the scale-up of this method to map large genomes are discussed.

Arabidopsis↗
PubMed1996

Molecular cloning and characterization of the CER2 gene of Arabidopsis thaliana.

Plants with defects in the synthesis of their epicuticular wax layer, eceriferum mutants (cer), are readily detected by the naked eye as bright green glossy plants when compared with the more glaucous normal plants. In a previous report, evidence was presented for the isolation of three lines from the Arabidopsis thaliana transformant collection (BRL5, BRL7 and BRL9) which failed to complement the cer2 mutant isolated previously. The analysis of the chemical composition of the epicuticular wax of these mutants suggests that the cer2 mutant of Arabidopsis is defective in very long chain fatty acid elongation. This paper reports the molecular cloning of the CER2 gene of Arabidopsis through the isolation of plant DNA flanking the site of T-DNA insertion as well as the characterization of the two independent T-DNA insertion mutant alleles, BRL5 and BRL9, of this gene. In the mutant line BRL5, T-DNA was found to be inserted in the second exon of the CER2 gene whereas in BRL9, T-DNA is inserted in the only intron of this gene. Nucleotide sequence analysis suggests that the ORF encodes a 47.3 kDa polypeptide. High levels of CER2 transcripts were detected in stems and flowers. The predicted amino acid sequence of the CER2 gene product reveals little homology with known protein sequences. In accordance with structural characterization of the T-DNA insertion mutants, no evidence of transcripts derived from the CER2 gene was found in either BRL5 or BRL9.

Amino Acid Sequence↗
PubMed1996

The CER3 gene of Arabidopsis thaliana is expressed in leaves, stems, roots, flowers and apical meristems.

The eceriferum3 (cer3) locus encodes one of 21 gene products known to be involved in wax biosynthesis in Arabidopsis thaliana. Mutations at these loci are readily identified by their bright, dark-green stems when compared with the more glaucous wild-type plant. Clones of a gene which encodes a 795 amino acid open reading frame have been isolated by using plant DNA flanking the site of a T-DNA insertion in line BRL1. Molecular complementation of the cer3 mutant phenotype by clones of this gene establish that it corresponds to the CER3 gene. Although the 90 kDa predicted amino acid sequence of this gene shows no homology to any other known protein, the second exon of CER3 encodes a RRX12KK nuclear localization sequence (NLS). Southern blot and DNA sequence analysis revealed that the T-DNA is inserted 89 bp downstream of the translation termination codon of this gene. Northern blot hybridization of RNA isolated from the BRL1 mutant with the CER3 cDNA probe indicated that the transcript is absent in this mutant line. Unlike other CER genes that have been cloned to date, high levels of the CER3 transcript were found in all tissues from wild-type plants, that is, leaves, stems, roots, flowers, and apical meristems.

Amino Acid Sequence↗
PubMed1996

Neuroblastoma: an enigmatic disease.

Neuroblastoma is the most common extra-cranial solid tumor of childhood. It originates in cells of the neural crest, and so can be found anywhere along the paravertebral sympathetic chain or in the adrenal gland. In the last 15 years, new developments in the genetics and biology of neuroblastoma, have led to a better understanding of the natural history and prognostic features of this cancer. The presence of identifying biochemical markers detectable in the urine of patients with neuroblastoma, as well as the remarkably inferior survival of children diagnosed at more than 12 months of age, have led some groups to screen infants for neuroblastoma, in the hope of decreasing both overall mortality, as well as the incidence of advanced stage disease. This article reviews some clinical aspects of neuroblastoma, but emphasizes the genetic and biologic features in relation to prognosis and treatment. Finally, we discuss the different screening experiences for this disease, in particular from the Quebec Neuroblastoma Screening Project.

Child↗
PubMed1996

Addition-deletion mutations in transgenic Arabidopsis thaliana generated by the seed co-cultivation method.

We have characterized three mutant alleles of the CER2 gene of Arabidopsis thaliana by sequencing polymerase chain reaction products of this gene generated with template DNA isolated from lines MK1, BRL7, and BRL17. Sequence analysis of the amplification product from line BRL17 revealed a 17-bp deletion in the CER2 gene. The CER2 gene of BRL7 differs from the wild-type sequence by a 2-base substitution and 2-base insertion. As both of these lines were isolated from the transformant populations generated by Dr. K. Feldmann and his collaborators, we suggest that these small rearrangements may be caused by unsuccessful T-DNA insertions. Comparative sequence analysis of the sequence of line MK1 and the wild type revealed a single nucleotide substitution located 360 bp downstream from the intron-exon junction that changes a tryptophan triplet TGG to TGA; i.e., an opal non-sense mutation. In accordance with these observations, the cer phenotype of line MK1 was complemented by transformation with a fusion construct of the CaMV 35S promoter and the CER2 structural gene. Comparative analysis of the deduced amino acid sequences encoded by the CER2 gene from Arabidopsis and by the glossy2 gene from Zea mays revealed a significant similarity between them. This suggests that these gene products may have a similar biochemical function.

Arabidopsis↗
PubMed1996

Methylmalonic acid quantification by stable isotope dilution gas chromatography-mass spectrometry from filter paper urine samples.

A specific method for quantification of methylmalonic acid (MMA) from urine samples dried onto filter paper is described. The method involves stable isotope dilution gas chromatography-mass spectrometry with [methyl-2H3]-MMA as the internal standard. MMA is stable in dry paper samples stored at room temperature for at least 2 weeks. The extraction efficiency of MMA from paper was 56-58%. The concentration of urinary MMA in dried filter paper specimens from 190 normal controls was 1.21 +/- 1.34 (mean +/- SD) mmol/mol of urinary creatinine. Age-related reference values are also reported. The concentrations, normalized to the urinary creatinine concentration, decrease with age. The applicability of this method to rapid screening for cobalamin (vitamin B12)-related disorders and methylmalonic aciduria is demonstrated.

Adolescent↗
PubMed1995

Screening for neuroblastoma in North America. Preliminary results of a pathology review from the Quebec Project.

BACKGROUND: The Quebec Neuroblastoma Screening Project was initiated to assess clinical and biologic aspects of neuroblastomas detected by screening infants born in the province of Quebec from May 1, 1989, to April 30, 1994. METHODS: Infants were screened for preclinical detection of neuroblastoma by determination of catecholamine metabolites, vanillylmandelic acid (VMA), and homovanillic acid (HVA). Patients with tumors discovered through this screening as well as patients in the same birth cohort with clinically detected tumors were referred to Quebec Oncology Centers for further investigation, diagnosis, and treatment. Pathology specimens were submitted to Childrens Hospital Los Angeles for central review. Tumors were histopathologically classified according to the Shimada system. RESULTS: As of August, 1993, 340,000 infants were screened at 3 weeks and 245,000 of them were retested at 6 months of age. Thirty-one tumors were detected through this screening and removed. Histologic material was available for 27 cases: 14 were detected at 3 weeks of age and 13 at 6 months of age. Twenty-six patients had tumors with favorable histology (FH), and one patient had a Stage I tumor with unfavorable histology (UH). At the time of this writing, all mass screening patients are alive, including one child with relapsed disease. During this period, 48 tumors were detected clinically in the same birth cohort, 40 of which were evaluated histologically. Of these 40 cases, 28 of 29 tumors diagnosed in patients up to age 12 months indicated an FH, whereas 9 of 11 tumors diagnosed in patients older than age 12 months indicated a UH. All patients with FH tumors are alive including a child with relapsed disease. The single patient with UH diagnosed before age 12 months died of disease. Of the nine patients with UH diagnosed after age 12 months, four died of disease, one relapsed, and four are alive (including one treated with bone marrow transplantation) after variable follow-up periods. CONCLUSIONS: The tumors detected by mass screening, similar to those tumors detected through clinical examination before age 12 months, were predominantly FH with good prognosis. However, those tumors that were missed by screening and were detected clinically after the patient was 12 months of age were predominantly UH, with serious clinical problems. This subgroup of patients not detectable by the current screening system presents an immediate and important clinical challenge that should be addressed in future studies.

Age Factors↗
PubMed1995

Adrenoleukodystrophy: magnetic resonance follow-up after Lorenzo's oil therapy.

PURPOSE: To determine the therapeutic value of Lorenzo's oil (a mixture of glyceryl trioleate and glyceryl trierucate oils) in treating the childhood form of adrenoleukodystrophy (ALD), as indicated by magnetic resonance imaging (MRI) follow-up. PATIENTS AND METHODS: Between January 1992 and March 1994 eight males with biochemically proven ALD, ranging in age from 1 to 28 years, were referred for cerebral MRI and initiation of Lorenzo's oil dietary therapy; treatment continued for a period of 6 to 24 months. Five of the patients underwent follow-up cerebral MRI, and the images were reviewed without knowledge of medical status or chronology of imaging relative to therapy; the other three patients were excluded from the study because follow-up examinations were lacking. Signal abnormalities were evaluated according to a modified Loes scale, which yielded a minimum rating of 0 (for normal findings) and a maximum rating of 35 (for the most severe abnormalities). Because an untreated control group was not available for comparison, the Wilcoxon signed-rank test was used to analyse the results. RESULTS: There was no statistically significant improvement in the ratings of abnormalities after treatment (p = 0.31, alpha = 0.10). However, the correlation between MRI findings and clinical symptoms was good. CONCLUSIONS: The Wilcoxon signed-rank test is a useful statistical tool for evaluating the results of studies in which the sample population is small and there is no control group. The authors suggest that although Lorenzo's oil may not be curative, it may have a role in preventing the progress of ALD in asymptomatic patients. A multicentre control trial of Lorenzo's oil treatment, with emphasis on asymptomatic patients, is now underway.

Adolescent↗
PubMed1994

Linkage disequilibrium analysis of childhood-onset spinal muscular atrophy (SMA) in the French-Canadian population.

Spinal muscular atrophy (SMA) is, after Duchenne muscular dystrophy, the most common neuromuscular disorder in childhood. The gene responsible for childhood SMA has been mapped to the q11.2-q13.3 region of chromosome 5. We have extended our linkage studies of SMA in the French-Canadian population to include microsatellite markers at the D5S125, D5S351, D5S435, JK53CA1/2 and MAP1B loci. These markers span about 4 cM of the SMA candidate region. We observed significant evidence for linkage between SMA and all the markers tested. The analysis of recombinant chromosomes provide evidence for the following genetic order: D5S125-D5S435-MAP1B-3'-JK53CA1/2 and places D5S351 proximal to JK53CA1/2. Furthermore, we confirm the current localization of the SMA gene distal to D5S435. Finally, we provide demonstration of significant linkage disequilibrium between childhood-onset SMA and four of the five marker loci, D5S125, D5S435, D5S351 and JK53CA1/2. Analysis of SMA-region haplotypes suggests that there may be a predominant SMA allele that is present on about 17% of SMA chromosomes in this sample of the French-Canadian population. We conclude that the observed linkage disequilibrium is likely due to genetic drift among regions of Quebec, consistent with this population's early history.

Age of Onset↗
PubMed1994

Identification of a gene that complements an Arabidopsis mutant deficient in chloroplast omega 6 desaturase activity.

Membrane lipids of the fad6 (formerly fadC) mutant of Arabidopsis, which is deficient in chloroplast omega 6 desaturase activity, have increased levels of monounsaturated fatty acids and are deficient in trienoic fatty acids. A putative fad6 cDNA clone was isolated by probing a cDNA library with a degenerate oligonucleotide based on a conserved region within known omega 3 desaturase genes. Expression of the cDNA in transgenic plants of a fad6 mutant restored normal levels of all fatty acids. When used as a hybridization probe, the cDNA identified a restriction fragment-length polymorphism that co-segregated with the fad6 mutation. Thus, on the basis of a genetic complementation test and genetic map position, the fad6 gene is encoded by the cDNA. The cDNA encoded a 418-amino acid polypeptide of 47,727 D that displayed a high degree of sequence similarity to a delta 12 desaturase from the cyanobacterium Synechocystis. The fad6 gene exhibited less sequence homology to any known higher plant desaturase, including an endoplasmic reticulum-localized omega 6 desaturase corresponding to the Arabidopsis fad2 gene.

Amino Acid Sequence↗
PubMed1994

Persistence and possible progression of a pelvic neuroblastoma detected by mass screening during 19 months.

PURPOSE: The preclinical detection of neuroblastoma by screening for elevated levels of urinary catecholamines often leads to the discovery of children with early-stage, biologically favorable disease. It is uncertain how vigorously therapy must be pursued in such cases. We report an infant whose pelvic mass was initially thought to be a fecaloma, and consequently was not treated for 19 months. CASE REPORT: A 2-month-old girl was referred for evaluation for the presence of a neuroblastoma because of elevated urinary catecholamines detected in a mass screening program. Although no mass was initially found, urinary catecholamines became increasingly elevated, and a pelvic mass was finally radiologically identified. It was resected. Histology showed it to be a neuroblastoma, POG stage C, International stage 3, with unfavorable Shimada features, although near triploid with an unamplified N-myc oncogene. Chemotherapy was given for five cycles, and the child remains well, with no evidence of disease. CONCLUSION: Although mass screening programs often detect early- stage, biologically favorable neuroblastomas that may spontaneously regress, our case had rising levels of urinary catecholamines and unfavorable histologic features at the time of resection. The unusual location of the tumor, and radiologic features of a fecaloma, contributed to the delay in definitive diagnosis, although persistence of elevated urinary catecholamines in the absence of a tumor is infrequent.

Catecholamines↗
PubMed1993

A conditional sterile mutation eliminates surface components from Arabidopsis pollen and disrupts cell signaling during fertilization.

Plants distinguish among the pollen grains that land on the stigma, permitting only compatible pollen to fertilize egg cells. To investigate these cell-cell interactions, Arabidopsis mutations that affect pollen-pistil communication were isolated. A male-sterile mutation that disrupts pollen-pistil interactions by eliminating the extracellular pollen coat (tryphine) is described here. Stigma cells that contact the mutant pollen produce callose, a carbohydrate synthesized in response to foreign pollen. The mutant pollen fails to germinate because it does not absorb water from the stigma, yet germinates in vitro, indicating it is viable. The defect is also conditional; high humidity results in pollen hydration and successful fertilization. Analysis of mature, mutant pollen indicated that it is deficient in long-chain lipids and has none of the lipoidic tryphine normally present on its surface. Immature mutant pollen grains have aberrant tryphine that disappears during pollen development. The sterile plants also lack stem waxes, and pollen from other wax-defective (eceriferum) mutants with reduced fertility has few of the lipid droplets normally present in tryphine. These results demonstrate that tryphine is critical for pollen-stigma interactions and suggest that tryphine lipids are required for fertilization, either by directly signaling the stigma or by stabilizing other tryphine components.

Arabidopsis↗