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Biomedical subjects

B Lemieux

Publications and source records attributed to B Lemieux.

At least 19 recordsLinked to original sources
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↗
PubMed1992

Map-based cloning of a gene controlling omega-3 fatty acid desaturation in Arabidopsis.

A gene from the flowering plant Arabidopsis thaliana that encodes an omega-3 desaturase was cloned on the basis of the genetic map position of a mutation affecting membrane and storage lipid fatty acid composition. Yeast artificial chromosomes covering the genetic locus were identified and used to probe a seed complementary DNA library. A complementary DNA clone for the desaturase was identified and introduced into roots of both wild-type and mutant plants by Ti plasmid-mediated transformation. Transgenic tissues of both mutant and wild-type plants had significantly increased amounts of the fatty acid produced by this desaturase.

Amino Acid Sequence↗
PubMed1992

Human myoblast transplantation: preliminary results of 4 cases.

Myoblasts from immunocompatible donors have been transplanted into the muscles (tibialis anterior, biceps brachii, and/or extensor carpi radialis longus) of 4 Duchenne patients in the advanced stages of the disease. Although no immunosuppressive treatment was used, none of the patients showed any clinical signs of rejection such as fever, redness, and inflammation. One patient transiently produced antibodies against the donor myoblasts as determined by cytofluorometric analysis. This patient and 2 others were shown to form antibodies against their donor's myotubes. Muscle biopsies of the injected tibialis anterior of 4 patients revealed that 80%, 75%, 25%, and 0% of the muscle fibers, respectively, showed some degree of dystrophin immunostaining. The contralateral noninjected muscles of the latter 3 patients did not contain any dystrophin positive fibers, while that of the first patient showed dystrophin expression in 16% of the fibers examined. Myoblasts were also injected into the extensor carpi radialis longus or the biceps brachii of these patients. A few months subsequent to injection, one patient was shown to have a 143% increase of strength during static wrist extension. This result must be interpreted with caution because a double-blind strength-measuring protocol was not used. Furthermore, we have noted that this change slowly decayed over time. The strength of 2 other patients was increased less remarkably (41% and 51%), while the strength of the fourth patient was unchanged.

Adolescent↗
PubMed1992

Nutritional vitamin B12 deficiency: two cases detected by routine newborn urinary screening.

We describe two asymptomatic newborns with nutritional vitamin B12 deficiency in whom increased urinary methylmalonic acid was detected by routine neonatal screening at 3 weeks of age. Both infants were exclusively breast-fed. One mother suffered from pernicious anaemia, and the other was a strict vegetarian. Both mothers had no clinical or haematological abnormality, aside from a borderline mean corpuscular volume for the vegetarian mother. This report illustrates the early appearance of functional vitamin B12 deficiency in breast-fed infants of vitamin B12-depleted mothers. It also demonstrates that urinary methylmalonic acid measurement is a sensitive indicator of tissue vitamin B12 deficiency.

Breast Feeding↗
PubMed1992

Screening urine of 3-week-old newborns: transient methylmalonic and hydroxyphenyllactic aciduria.

Urinary methylmalonic acid (MMA) and 4-hydroxyphenyllactic acid (HPL) have been determined in 3345 and 2498 3-week-old newborns, respectively. Urine was collected onto filter paper and assayed by a rapid gas chromatography-mass spectrometry method. Forty-six infants (1.7%) had elevated MMA levels (greater than 58.5 micrograms/mg creatinine, means + 5 SD) and 31 infants (1.2%) had elevated levels of HPL (greater than 87.7 micrograms/mg creatinine, means + 5 SD). Fifteen infants with elevated values of MMA were retested from one to several months after the first test. In 12 infants the MMA levels normalized, while in the remaining three, elevated methylmalonic acid persisted. Nine infants with elevated values of HPL were retested, and in all except one, HPL levels normalized. No access to clinical evaluation of the infants was available. Transient methylmalonic aciduria and transient tyrosyluria affect a substantial number of infants and the clinical significance of this phenomenon has yet to be determined.

Humans↗
PubMed1992

Linkage study of chronic childhood-onset spinal muscular atrophy (SMA): confirmation of close linkage to D5S39 in French Canadian families.

Chronic childhood-onset spinal muscular atrophy (SMA) is, after Duchenne muscular dystrophy, the most common neuromuscular disorder in childhood. Recent linkage analyses have mapped this disease to 5q12-5q14. We show that chronic SMA (Types II and III) is tightly linked to the marker locus D5S39 (Zmax = 5.47 at theta = 0.02) in eight French Canadian families. In contrast to previously published results, we do not observe close linkage between chronic SMA and D5S6 (Zmax = 0.34 at theta = 0.18) or D5S78 (Zmax = 0.25 at theta = 0.21). Last, we present a family that appears to be discordant for this localization but may represent the first example of an incompletely penetrant individual.

Canada↗
PubMed1992

Neuroblastoma represents distinct clinical-biologic entities: a review and perspective from the Quebec Neuroblastoma Screening Project.

Data are presented suggesting that neuroblastoma represents at least two distinct clinical-biologic entities. One, favorable neuroblastoma, is associated with young age and early stage at diagnosis, triploid karyotypes, no 1p abnormalities or N-myc gene amplification, more mature catecholamine synthesis and excretion, and excellent clinical outcome despite no or minimal therapy. The other, unfavorable neuroblastoma, is associated with older age and advanced stage, pseudodiploid karyotypes and 1p deletions, N-myc oncogene amplification, less mature catecholamine synthesis and excretion, and poor outcome despite aggressive multimodality therapy including bone marrow transplantation. Favorable neuroblastomas rarely, if ever, evolve into unfavorable disease. Unresolved issues regarding this hypothesis and implications for the efficacy of preclinical detection through mass screening are discussed.

Age Factors↗
PubMed1991

Identification and map position of YAC clones comprising one-third of the Arabidopsis genome.

YAC clones corresponding to 125 Arabidopsis thaliana RFLP markers have been identified. At least one YAC clone has been isolated for each of the RFLP markers tested. Based on CHEF gel analysis of 196 clones, the mean insert size of the available Arabidopsis YAC libraries is approximately 160 kb. The YACs of known genetic map location encompass about 30% of the Arabidopsis genome. The results presented here represent a first step towards assembly of an overlapping YAC library of the A. thaliana genome.

Arabidopsis↗
PubMed1991

Screening newborns for multiple organic acidurias in dried filter paper urine samples: method development.

Screening urine for inherited and acquired organic acidurias in newborns has the potential of preventing severe disease, mental retardation, and death. A method for screening dried urine filter paper samples for acidic markers of at least 20 different metabolic conditions has been developed. These conditions include, among others, maple syrup urine disease; methylmalonic, propionic, isovaleric, glutaric, and hydroxymethylglutaric acidurias; methylcrotonylglycinuria; medium-chain acyl-CoA dehydrogenase deficiency; inherited vitamin responsive disorders B12, biotin, B2), and acquired deficiencies of these vitamins. The preparation of the urine extract is identical to the method we use to screen infants for neuroblastoma. Screening is based on a highly sensitive and specific determination of eight organic acid markers by an automated computerized gas chromatography mass spectrometry system using selected ion monitoring. The markers used for screening are methylmalonic acid, 2-hydroxyisocaproic acid, glutaric acid, propionylglycine, isovalerylglycine, 3-methylcrotonylglycine, hexanoylglycine, and 3-phenylpropionylglycine. The extraction efficiencies of these acids from dried filter paper were similar to extraction from water, ranging from about 40% to 80%, except for propionylglycine which showed a low extraction efficiency of 11-13%. The stability of these acids on filter paper exposed to room air and temperature over a period of 15 d was adequate for the use of this collection method for organic aciduria screening. Normal levels, adjusted to urinary creatinine, were established for these acids in 519 urine filter paper samples obtained from 3-wk-old newborns. This screening method was tested on samples obtained from 12 patients with known organic acidurias including stored urine filter paper collected at 3-wk of age from two infants later found to have organic acidurias.

Amino Acids↗
PubMed1990

Screening for neuroblastoma at 3 weeks of age: methods and preliminary results from the Quebec Neuroblastoma Screening Project.

A large neuroblastoma screening study was recently started in the province of Quebec, Canada. This project, a collaboration between the Quebec Network for Genetic Medicine and the University of Minnesota, is studying the impact of screening infants for the preclinical detection of neuroblastoma on the population-based mortality caused by this tumor. All infants born in Quebec during a 5-year period will be screened twice, at 3 weeks and at 6 months. Urinary homovanillic acid and vanillylmandelic acid determination from dried filter paper samples is used for screening. Initial qualitative screening is done by means of thin-layer chromatography with confirmatory quantitative screening by gas chromatography-mass spectrometry (GC-MS). During the initial 6 months of 3-week screening, 41,673 neonates (92% compliance rate) were screened and 10.6% of them were tested also by GC-MS. Nine of these neonates had positive results on two GC-MS tests and were referred for evaluation to rule out the presence of neuroblastoma. Four had the tumor, 1 had a calcified adrenal gland, and 4 had no tumor detected. Three additional neonates had clinical diagnosis of neuroblastoma before they reached the screening age of 3 weeks. A neuroblastoma that did not secrete homovanillic acid or vanillylmandelic acid was diagnosed clinically in 1 additional patient who tested negative by screening.

Chromatography, Gas↗