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Biomedical subjects

J R Mendell

Publications and source records attributed to J R Mendell.

At least 73 records · Page 4Linked to original sources
PubMed1995

Myoblast transfer in the treatment of Duchenne's muscular dystrophy.

BACKGROUND: Myoblast transfer has been proposed as a technique to replace dystrophin, the skeletal-muscle protein that is deficient in Duchenne's muscular dystrophy. Donor myoblasts injected into muscles of affected patients can fuse with host muscle fibers, thus contributing their nuclei, which are potentially capable of replacing deficient gene products. Previous controlled trials involving a single transfer of myoblasts have been unsuccessful. METHODS: We injected donor muscle cells once a month for six months to the biceps brachii muscles of one arm of each of 12 boys with Duchenne's muscular dystrophy. The opposite arms served as sham-injected controls. In each procedure 110 million cells donated by fathers or brothers were transferred. The patients were randomly assigned to receive either cyclosporine or placebo. Strength was measured by quantitative isometric muscle testing. Six months after the final myoblast transfer, the presence of dystrophin was assessed with the use of peptide antibodies specific to the deleted exons of the dystrophin gene. RESULTS: There was no significant difference in muscle strength between arms injected with myoblasts and sham-injected arms. In one patient, 10.3 percent of muscle fibers expressed donor-derived dystrophin after myoblast transfer. Three other patients also had a low level of donor dystrophin (< 1 percent); eight had none. CONCLUSIONS: Myoblasts transferred once a month for six months failed to improve strength in patients with Duchenne's muscular dystrophy. The value of exon-specific peptide antibodies in the interpretation of myoblast-transfer results was demonstrated in a patient with Duchenne's muscular dystrophy who had a high percentage of donor-derived dystrophin. Specific variables affecting the efficiency of myoblast transfer need to be identified in order to improve upon this technique.

Antibodies↗
PubMed1995

Amyloidosis causing a progressive myopathy.

A 62-year-old woman developed profound weakness secondary to a progressive myopathy associated with primary systemic amyloidosis. The characteristic apple-green birefringent amyloid deposits were demonstrated surrounding individual muscle fibers in Congo red stained sections. Electron microscopy demonstrated amyloid filaments in close apposition to muscle fibers exhibiting excessive corrugations of the sarcolemmal membrane. The pathological features of progressive amyloid myopathy associated with primary systemic amyloidosis are distinct from the intracellular amyloid deposits characteristic of sporadic inclusion body myositis and inherited inclusion body myopathy.

Amyloidosis↗
PubMed1995

A novel cDNA detects homozygous microdeletions in greater than 50% of type I spinal muscular atrophy patients.

Spinal muscular atrophy (SMA) is the second most common lethal, autosomal recessive disease in Caucasians (after cystic fibrosis). Childhood SMAs are divided into three groups (type I, II and III), which are allelic variants of the same locus in a region of approximately 850 kb in chromosome 5q12-q13, containing multiple copies of a novel, chromosome 5-specific repeat as well as many atypical pseudogenes. This has hampered the identification of candidate genes. We have identified several coding sequences unique to the SMA region. A genomic fragment detected by one cDNA is homozygously deleted in 17/29 (58%) of type I SMA patients. Of 235 unaffected individuals examined, only two showed the deletion and both are carriers of SMA. Our results suggest that deletion of at least part of this novel gene is directly related to the phenotype of SMA.

Base Sequence↗
PubMed1995

The childhood muscular dystrophies: diseases sharing a common pathogenesis of membrane instability.

New observations demonstrate that several childhood forms of muscular dystrophy share a common pathogenesis. In muscle, dystrophin occurs as part of a membrane complex (dystrophin-glycoprotein) linking the cytoskeleton to the basal lamina. In Duchenne muscular dystrophy, dystrophin deficiency disrupts the linkage of the integral glycoproteins of the sarcolemma and leads to muscle fiber necrosis. In severe childhood autosomal recessive muscular dystrophy, a selective deficiency of adhalin (50-kd glycoprotein) also causes dysfunction of the dystrophin-glycoprotein complex. Most recently, a form of congenital muscular dystrophy demonstrates deficiency of laminin M (merosin) further demonstrating that sarcolemmal instability results from defects in structural proteins of the basal lamina. Animal models have been identified also demonstrating defects in specific proteins linking the subsarcolemmal cytoskeleton to the extracellular matrix. The mdx mouse has a defect in the gene encoding dystrophin. The cardiomyopathic hamster shows a specific deficiency of adhalin in skeletal muscle. The dy/dy mouse has been found deficient in merosin. These animal models will help researchers to understand their human counterparts and provide a system for testing therapeutic strategies.

Animals↗
PubMed1995

Inclusion body myositis: explanation for poor response to immunosuppressive therapy.

We treated eight patients who had inclusion body myositis (IBM) with oral prednisone therapy, and we performed muscle biopsies before and after treatment. We documented the patients' clinical response to therapy and changes in serum CK. Although the serum CK level fell, muscle strength worsened after prednisone treatment. In addition, while inflammation decreased in the muscle biopsy specimens, the number of vacuolated and amyloid-positive fibers increased after oral prednisone therapy. These observations indicate that the inflammatory response in IBM may play a secondary role in the pathogenesis of IBM. The unique findings of intracellular amyloid deposits and rimmed vacuoles distinguishing IBM from other inflammatory myopathies, and recognition that suppression of inflammation has no effect on the clinical course, suggest that IBM may represent a degenerative muscle disorder.

Aged↗
PubMed1995

Spectrum of small mutations in the dystrophin coding region.

Duchenne and Becker muscular dystrophies (DMD and BMD) are caused by defects in the dystrophin gene. About two-thirds of the affected patients have large deletions or duplications, which occur in the 5' and central portion of the gene. The nondeletion/duplication cases are most likely the result of smaller mutations that cannot be identified by current diagnostic screening strategies. We screened approximately 80% of the dystrophin coding sequence for small mutations in 158 patients without deletions or duplications and identified 29 mutations. The study indicates that many of the DMD and the majority of the BMD small mutations lie in noncoding regions of the gene. All of the mutations identified were unique to single patients, and most of the mutations resulted in protein truncation. We did not find a clustering of small mutations similar to the deletion distribution but found > 40% of the small mutations 3' of exon 55. The extent of protein truncation caused by the 3' mutations did not determine the phenotype, since even the exon 76 nonsense mutation resulted in the severe DMD phenotype. Our study confirms that the dystrophin gene is subject to a high rate of mutation in CpG sequences. As a consequence of not finding any hotspots or prevalent small mutations, we conclude that it is presently not possible to perform direct carrier and prenatal diagnostics for many families without deletions or duplications.

Base Sequence↗
PubMed1995

A molecular protocol for diagnosing myotonic dystrophy.

Myotonic dystrophy (DM) is an autosomal dominant genetic disease caused by an unstable CTG repeat sequence in the 3' untranslated region of the myotonin protein kinase gene. The CTG repeat is present 5-30 times in the normal population, whereas DM patients have CTG expansions of 50 to several thousand repeats. The age of onset of the disorder and the severity of the phenotype is roughly correlated with the size of the CTG expansion. We developed a molecular protocol for the diagnosis of DM based on an initial polymerase chain reaction screen to detect normal-sized alleles and small expansions, followed by an improved Southern protocol to detect larger expansions.

Adult↗
PubMed1995

Frameshift deletions of exons 3-7 and revertant fibers in Duchenne muscular dystrophy: mechanisms of dystrophin production.

Duchenne muscular dystrophy (DMD) patients with mutations that disrupt the translational reading frame produce little or no dystrophin. Two exceptions are the deletion of exons 3-7 and the occurrence of rare dystrophin-positive fibers (revertant fibers) in muscle of DMD patients. Antibodies directed against the amino-terminus and the 5' end of exon 8 did not detect dystrophin in muscle from patients who have a deletion of exons 3-7. However, in all cases, dystrophin was detected with an antibody directed against the 3' end of exon 8. The most likely method of dystrophin production in these cases is initiation at a new start codon in exon 8. We also studied two patients who have revertant fibers: one had an inherited duplication of exons 5-7, which, on immunostaining, showed two types of revertant fibers; and the second patient had a 2-bp nonsense mutation in exon 51, which creates a cryptic splice site. An in-frame mRNA that uses this splice site in exon 51 was detected. Immunostaining demonstrated the presence of the 3' end of exon 51, which is in agreement with the use of this mRNA in revertant fibers. The most likely method of dystrophin production in these fibers is a second mutation that restores the reading frame.

Amino Acid Sequence↗
PubMed1994

CNTF potentiates peripheral nerve regeneration.

The effect of ciliary neurotrophic factor (CNTF) on peripheral nerve regeneration was studied in 6-week-old rats following sciatic nerve transection and juxtaposition of proximal and distal stumps. Rats received intraperitoneal recombinant human CNTF, 1 mg/kg every other day for 12 days. In all CNTF-treated animals, the distribution of the anterograde transport of [3H]leucine-labeled material within the distal stump showed a distinct peak activity 21-24 mm distal to the nerve transection site. In contrast, the radioactivity in control nerves declined rapidly, distributed as proximodistal gradient without a distinct peak. In addition, the amount of radioactivity returning from the growing axon tips in CNTF was significantly greater than controls. The correlative morphologic studies showed a well-advanced stage of myelination in regenerating axons in CNTF compared to controls. These combined in vivo correlative kinetic and morphological studies indicate that CNTF dramatically potentiates axonal regeneration by promoting a greater number of elongating axon tips into the distal stump.

Animals↗
PubMed1994

Heteroduplex analysis of the dystrophin gene: application to point mutation and carrier detection.

Approximately one-third of the Duchenne muscular dystrophy patients have undefined mutations in the dystrophin gene. For carrier and prenatal studies in families without detectable mutations, the indirect restriction fragment length polymorphism linkage approach is used. Using a multiplex amplification and heteroduplex analysis of dystrophin exons, we identified nonsense mutations in two DMD patients. Although the nonsense mutations are predicted to severely truncate the dystrophin protein, both patients presented with mild clinical courses of the disease. As a result of identifying the mutation in the affected boys, direct carrier studies by heteroduplex analysis were extended to other relatives. We conclude that the technique is not only ideal for mutation detection but is also useful for diagnostic testing.

Base Sequence↗
PubMed1994

Immunosuppressive treatment of motor neuron syndromes. Attempts to distinguish a treatable disorder.

OBJECTIVE: To determine if response to immunosuppressive treatment in motor neuron syndromes could be predicted on the basis of clinical features, anti-GM1 antibodies, or conduction block. DESIGN: Prospective, uncontrolled, treatment trial using prednisone for 4 months followed by intravenous cyclophosphamide (3 g/m2) continued orally for 6 months. SETTING: All patients were referred to university hospital medical centers. PATIENTS: Sixty-five patients with motor neuron syndromes were treated with prednisone; 11 patients had elevated GM1 antibody titers, and 11 patients had conduction block. Forty-five patients received cyclophosphamide, eight of whom had elevated GM1 antibodies and 10 had conduction block. RESULTS: One patient responded to prednisone, and five patients responded to cyclophosphamide treatment. Only patients with a lower motor neuron syndrome and conduction block improved with either treatment. Response to treatment did not correlate with GM1 antibodies. CONCLUSIONS: GM1 antibodies did not serve as a marker for improvement in patients with motor neuron syndrome treated with immunosuppressive drugs. Patients with amyotrophic lateral sclerosis failed to improve irrespective of laboratory findings.

Adult↗
PubMed1994

Taxol neuropathy. Electrodiagnostic and sural nerve biopsy findings.

Taxol has recently been approved for the treatment of ovarian cancer that has failed to respond to other chemotherapeutic agents. A predominantly sensory neuropathy has been reported in patients receiving taxol, but corresponding nerve changes have not been described. The patient described herein received taxol at a dose of 275 mg/m2 every 21 days. The sural nerve biopsy performed after 17 courses of taxol (cumulative dose, 6603 mg) showed severe nerve fiber loss, axonal atrophy, and secondary demyelination. Axonal regeneration was absent. The findings are compatible with a cell body disease or a length-dependent, distal neuropathy with failure of axonal regeneration. The findings observed in taxol-induced neuropathy are important to document for comparison with other neoplastic and paraneoplastic neuropathies affecting patients with cancer.

Electrodiagnosis↗
PubMed1994

Hyaline body myopathy.

Muscle biopsy from two unrelated patients, a male aged 40 and a female aged 3, with relatively non-progressive limb weakness since infancy, revealed numerous subsarcolemmal glassy, hyaline appearing bodies present in 20-30% of the fibres. Type 1 fibre predominance was present, and the hyaline bodies were exclusive to type 1 fibres. The hyaline bodies were negative with oxidative enzyme and periodic acid-Schiff stains. Electron microscopy showed the hyaline bodies to contain amorphous granular material of unknown composition. No membrane separated the hyaline bodies from the surrounding sarcoplasm. Hyaline body myopathy most likely represents a distinct congenital myopathy because of its childhoot-onset, non-progressive course, and distinct morphological features.

Adult↗
PubMed1994

The impact of molecular genetics on the care of patients with muscle disease.

Clinical medicine is currently undergoing an enormous upheaval as a result of molecular genetics. Identifying the gene causing a specific disease almost immediately provides knowledge of the gene product and insight into pathogenesis. Mutations of the gene and measurable abnormalities of the gene product provide specific methods for diagnosis, prenatal counseling, and carrier detection. Perhaps, most importantly, new treatment strategies can be devised. In the review that follows, an update is provided on molecular findings in muscle diseases and how they can be applied in clinical practice.

Adolescent↗