The Experts below are selected from a list of 6438 Experts worldwide ranked by ideXlab platform
Lars Bolund - One of the best experts on this subject based on the ideXlab platform.
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expression of wild type and mutant medium chain acyl coa dehydrogenase mcad cdna in eucaryotic cells
Biochimica et Biophysica Acta, 1992Co-Authors: Thomas G Jensen, Peter Bross, Uffe Birk Jensen, Elisabeth Holme, Steen Kolvraa, Niels Gregersen, Brage S. Andresen, Lars BolundAbstract:Abstract An effective EBV-based expression system for eucaryotic cells has been developed and used for the study of the mitochondrial enzyme medium-chain acyl-CoA dehydrogenase (MCAD). 1325 bp of PCR-generated cDNA, containing the entire coding region, was placed between the SV40 early promotor and polyadenylation signals in the EBV-based vector. Both wild-type MCAD cDNA and cDNA containing the prevalent disease-causing mutation A to G at position 985 of the MCAD cDNA were tested. In transfected COS-7 cells, the steady state amount of mutant MCAD protein was consistently lower than the amount of wild-type human enzyme. The enzyme activity in extracts from cells harbouring the wild-type MCAD cDNA was dramatically higher than in the controls (harbouring the vector without the MCAD gene) while only a slightly higher activity was measured with the mutant MCAD. The mutant MCAD present behaves like wild-type MCAD with respect to solubility, subcellular location, mature protein size and tetrameric structure. In immunoblot comparisons, the MCAD protein was present in normal fibroblasts, but essentially undetectable in patient fibroblasts homozygous for the prevalent mutation. We suggest that the MCAD protein carrying this mutation has an impaired ability to form correct tetramers, leading to instability and subsequent degradation of the enzyme. This finding is discussed in relation to the results from expression of human MCAD in Escherichia coli, where preliminary results show that production of mutant MCAD leads to the formation of aggregates.
A. W. Strauss - One of the best experts on this subject based on the ideXlab platform.
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Molecular basis of inherited medium-chain acyl-CoA dehydrogenase deficiency causing sudden child death
Journal of Inherited Metabolic Disease, 1992Co-Authors: D P Kelly, D. E. Hale, S. L. Rutledge, M. L. Ogden, A. J. Whelan, Z. Zhang, A. W. StraussAbstract:Deficiency of medium-chain acyl-CoA dehydrogenase (MCAD) is an important cause of sudden death in children. The majority of surviving individuals with MCAD deficiency studied to date are homozygous for a single point mutation at bp 985 of the MCAD mRNA (A985G). We have now identified a four-base-pair deletion in exon 11 of one allele of the MCAD gene in an American child who died of MCAD deficiency. The deletion mutation results in a frameshift and premature termination codon in the mutant MCAD mRNA. The second mutant allele contained the common point mutation A985G, and thus the proband was a compound heterozygote. Protein immunoblot analysis of the child's liver proteins revealed that the mutant MCAD proteins were barely detectable. Allele-specific oligonucleotide hybridization analysis performed on amplified exon 11 of the child's MCAD gene clearly identified both mutations. MCAD RFLP analysis of the patient's DNA revealed heterozygosity at the Taq I MCAD RFLP site, thus, the two mutations are associated with different haplotypes. Therefore, we have identified a new mutation in the MCAD gene and have developed a nucleic-acid-based screening approach which allows the post mortem identification of MCAD deficiency.
Rama Chellappa - One of the best experts on this subject based on the ideXlab platform.
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Learning from Ambiguously Labeled Face Images
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2018Co-Authors: Ching-hui Chen, Vishal M. Patel, Rama ChellappaAbstract:Learning a classifier from ambiguously labeled face images is challenging since training images are not always explicitly-labeled. For instance, face images of two persons in a news photo are not explicitly labeled by their names in the caption. We propose a Matrix Completion for Ambiguity Resolution (MCAR) method for predicting the actual labels from ambiguously labeled images. This step is followed by learning a standard supervised classifier from the disambiguated labels to classify new images. To prevent the majority labels from dominating the result of MCAR, we generalize MCAR to a weighted MCAR (WMCAR) that handles label imbalance. Since WMCAR outputs a soft labeling vector of reduced ambiguity for each instance, we can iteratively refine it by feeding it as the input to WMCAR. Nevertheless, such an iterative implementation can be affected by the noisy soft labeling vectors, and thus the performance may degrade. Our proposed Iterative Candidate Elimination (ICE) procedure makes the iterative ambiguity resolution possible by gradually eliminating a portion of least likely candidates in ambiguously labeled faces. We further extend MCAR to incorporate the labeling constraints among instances when such prior knowledge is available. Compared to existing methods, our approach demonstrates improvements on several ambiguously labeled datasets.
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Learning from Ambiguously Labeled Face Images
arXiv: Computer Vision and Pattern Recognition, 2017Co-Authors: Ching-hui Chen, Vishal M. Patel, Rama ChellappaAbstract:Learning a classifier from ambiguously labeled face images is challenging since training images are not always explicitly-labeled. For instance, face images of two persons in a news photo are not explicitly labeled by their names in the caption. We propose a Matrix Completion for Ambiguity Resolution (MCAR) method for predicting the actual labels from ambiguously labeled images. This step is followed by learning a standard supervised classifier from the disambiguated labels to classify new images. To prevent the majority labels from dominating the result of MCAR, we generalize MCAR to a weighted MCAR (WMCAR) that handles label imbalance. Since WMCAR outputs a soft labeling vector of reduced ambiguity for each instance, we can iteratively refine it by feeding it as the input to WMCAR. Nevertheless, such an iterative implementation can be affected by the noisy soft labeling vectors, and thus the performance may degrade. Our proposed Iterative Candidate Elimination (ICE) procedure makes the iterative ambiguity resolution possible by gradually eliminating a portion of least likely candidates in ambiguously labeled face. We further extend MCAR to incorporate the labeling constraints between instances when such prior knowledge is available. Compared to existing methods, our approach demonstrates improvement on several ambiguously labeled datasets.
J G Loeber - One of the best experts on this subject based on the ideXlab platform.
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neonatal screening for medium chain acyl coa dehydrogenase mcad deficiency in the netherlands the importance of enzyme analysis to ascertain true mcad deficiency
Journal of Inherited Metabolic Disease, 2008Co-Authors: Terry G J Derks, Jos P N Ruiter, Theo Boer, A Van Assen, T Bos, Klaziena Niezenkoning, J M M Rondeel, Hans R Waterham, Ronald J.a. Wanders, J G LoeberAbstract:The outcome was determined of population-wide neonatal screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency using tandem mass spectrometry (MS/MS) in The Netherlands, between October 2003 and September 2005. Prospective population-wide neonatal screening for MCAD deficiency was performed in the northern part of The Netherlands. In newborns with blood octanoylcarnitine (C8:0) concentrations ≥0.3 μmol/L, clinical and laboratory follow-up was initiated, including MCAD enzymatic measurements which played a decisive role. In a 2-year period, 66 216 newborns were investigated for MCAD deficiency and follow-up was initiated in 28 newborns. True-positives (n = 14) were identified based upon MCAD enzyme activity 5.0 turned out to differentiate between false-positives and true-positives. Measurement of MCAD activity using phenylpropionyl-CoA as a substrate further discriminated between newborns with MCAD deficiency and so-called mild MCAD deficiency. To summarize, neonatal screening for MCAD deficiency in the northern part of The Netherlands resulted in the predicted number of affected newborns. Measurement of MCAD activity in leukocytes or lymphocytes using phenylpropionyl-CoA as a substrate can be regarded as the gold standard to diagnose MCAD deficiency upon initial positive screening test results.
Thomas G Jensen - One of the best experts on this subject based on the ideXlab platform.
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expression of wild type and mutant medium chain acyl coa dehydrogenase mcad cdna in eucaryotic cells
Biochimica et Biophysica Acta, 1992Co-Authors: Thomas G Jensen, Peter Bross, Uffe Birk Jensen, Elisabeth Holme, Steen Kolvraa, Niels Gregersen, Brage S. Andresen, Lars BolundAbstract:Abstract An effective EBV-based expression system for eucaryotic cells has been developed and used for the study of the mitochondrial enzyme medium-chain acyl-CoA dehydrogenase (MCAD). 1325 bp of PCR-generated cDNA, containing the entire coding region, was placed between the SV40 early promotor and polyadenylation signals in the EBV-based vector. Both wild-type MCAD cDNA and cDNA containing the prevalent disease-causing mutation A to G at position 985 of the MCAD cDNA were tested. In transfected COS-7 cells, the steady state amount of mutant MCAD protein was consistently lower than the amount of wild-type human enzyme. The enzyme activity in extracts from cells harbouring the wild-type MCAD cDNA was dramatically higher than in the controls (harbouring the vector without the MCAD gene) while only a slightly higher activity was measured with the mutant MCAD. The mutant MCAD present behaves like wild-type MCAD with respect to solubility, subcellular location, mature protein size and tetrameric structure. In immunoblot comparisons, the MCAD protein was present in normal fibroblasts, but essentially undetectable in patient fibroblasts homozygous for the prevalent mutation. We suggest that the MCAD protein carrying this mutation has an impaired ability to form correct tetramers, leading to instability and subsequent degradation of the enzyme. This finding is discussed in relation to the results from expression of human MCAD in Escherichia coli, where preliminary results show that production of mutant MCAD leads to the formation of aggregates.