ABSTRACT
Myosin storage myopathy is a congenital myopathy characterized by subsarcolemmal hyaline bodies in type 1 muscle fibers, which are ATPase positive and thus contain myosin. Mutations recently were identified in the type 1 muscle fiber myosin gene (MYH7) in Swedish and Saudi families with myosin storage myopathy. The authors have identified the arginine 1845 tryptophan mutation found in the Swedish families in two isolated Belgian cases, indicating a critical role for myosin residue arginine 1845.
Subject(s)
Amino Acid Substitution , Muscular Diseases/genetics , Mutation, Missense , Myosin Heavy Chains/genetics , Myosins/metabolism , Point Mutation , Adult , Belgium , Cardiac Myosins , Female , Humans , Hyalin/chemistry , Inclusion Bodies/chemistry , Male , Middle Aged , Muscle Fibers, Slow-Twitch/chemistry , Muscle Fibers, Slow-Twitch/pathology , Muscle Weakness/genetics , Muscle Weakness/metabolism , Muscular Diseases/metabolism , Myosin Heavy Chains/chemistry , Myosin Heavy Chains/physiology , Protein ConformationABSTRACT
Golden retriever muscular dystrophy arises from a mutation in the acceptor splice site of intron 6 of the dystrophin gene. Skipping of exon 7 disrupts the mRNA reading frame and results in premature termination of translation. We are using this animal model to evaluate treatments for Duchenne muscular dystrophy, including gene repair induced by chimeric oligonucleotides. After injection of golden retriever muscular dystrophy (GRMD) muscle with a chimeric oligonucleotide to repair the lesion, immunostaining revealed a modest increase in the number of dystrophin-positive fibres at the injection sites. Dystrophin gene transcripts containing exon 7 were detected by reverse transcription-polymerase chain reaction, suggesting that low levels of splice site correction may have occurred. However, DNA sequencing of these apparently normal dystrophin gene transcripts revealed that the first five bases of exon 7 were missing. It will be important to be aware of this phenomenon with respect to further gene correction studies in the canine model.
Subject(s)
Alternative Splicing/genetics , Muscular Dystrophy, Duchenne/genetics , Mutagenesis, Site-Directed/genetics , RNA Splice Sites/genetics , Animals , Chimera/genetics , Disease Models, Animal , Dogs , Dystrophin/genetics , Exons/genetics , Female , Frameshift Mutation/genetics , Immunohistochemistry , Male , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , Muscle, Skeletal/physiopathology , Muscular Dystrophy, Duchenne/metabolism , Muscular Dystrophy, Duchenne/physiopathology , Oligonucleotides/pharmacology , RNA, Messenger/genetics , Reading Frames/genetics , Reverse Transcriptase Polymerase Chain Reaction , Transcription, Genetic/geneticsABSTRACT
The effect of soil loading on the dermal uptake of soil-borne contaminants was examined using an in vitro evaporation/penetration apparatus and abdominal skin from human cadavers. Dermal uptake of two 14C-labeled pesticides, lindane and 2,4-dichlorophenoxyacetic acid (2,4-D), was assessed at nominal soil loadings of 1, 5, and 10 mg/cm2. Sub-150-microns fractions of two soils with differing organic carbon contents were employed. Mean 24-h dermal absorption values ranged from 0.45 to 2.35% for lindane and from 0.18 to 1.64% for 2,4-D, depending upon soil load and type. Mean mass fluxes ranged from 8.8 to 32 pg/cm2/h for lindane and from 1.9 to 6.4 pg/cm2/h for 2,4-D. Results were aggregated as ratios of flux or percent absorption at 1 and 10 mg/cm2 to corresponding values obtained at 5 mg/cm2. Fluxes at 5 and 10 mg/cm2 did not differ significantly, but flux at 1 mg/cm2 was about one-half the value observed at the higher loadings. The most plausible explanation for this decrease in mass flux is incomplete (submonolayer) coverage of the skin. Evidence in the form of electron micrographs is presented in support of this conclusion. Relative percent absorption increased significantly with decreases in soil load from 10 to 5 and from 5 to 1 mg/cm2. This effect was inversely proportional to loading reduction in the former case, but was less than proportional due to the impact of contact area reduction (and, in the case of lindane, volatilization losses) in the latter. Percent dermal absorption data obtained in the laboratory require adjustment for differences in loading and coverage before application to assessment of exposure to contaminants in soils. Description of dermal absorption from soil in a manner comparable to that used to describe absorption from a liquid or vapor (i.e., using a driving force and a mass transfer coefficient) would reduce confusion on this point and is recommended.