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Biomedical subjects

H Lochmüller

Publications and source records attributed to H Lochmüller.

At least 55 records · Page 3Linked to original sources
PubMed2001

[New insights in pathogenesis and therapy of sporadic inclusion body myositis (s-IBM)].

Sporadic inclusion body myositis (s-IBM) is a chronic progressive inflammatory myopathy which occurs preferentially in older patients. Histologic hallmarks are rimmed vacuoles and eosinophilic cytoplasmatic inclusions. The etiology is still unknown, but different pathogenetic mechanisms such as slow virus infection, autoimmunopathogenesis, myonuclear alterations, and mitochondrial defects have been implicated. A relation to neurodegenerative disorders and prion diseases has also been suggested. There is a poor response if any to immunosuppressive therapy. Stabilization of disease progression was shown only by intravenous immunoglobulin (IVIG) therapy. Future findings in the field of s-IBM pathogenesis may result in better therapeutic options.

Aged↗
PubMed2001

Characterization of human muscle type cofilin (CFL2) in normal and regenerating muscle.

Cofilins are actin binding proteins and regulate actin assembly in vivo. Numerous cofilin homologues have been characterized in various organisms including mammals. In mice, a ubiquitously expressed cofilin (CFL1) and a skeletal muscle specific cofilin (CFL2) have been described. In the present study, we identified and characterized a human CFL2 gene localized on chromosome 14, with high homology to murine CFL2. Furthermore, we provide evidence for differentially spliced CFL2 transcripts (CFL2a and CFL2b). CFL2b is expressed predominantly in human skeletal muscle and heart, while CFL2a is expressed in various tissues. Genetic defects of CFL2 were excluded for one human muscle disorder, the chromosome 14 linked distal myopathy MPD1, and shown to be only possible to be a rare cause of another, nemaline myopathy. In a mouse model of mechanically induced muscle damage the changes of cofilin expression were monitored during the first 10 days of regeneration, with dephosphorylated CFL2 being the major isoform at later stages of muscle regeneration. A similar predominance of dephosphorylated CFL2 was observed in chronically regenerating dystrophin-deficient muscles of Duchenne muscular dystrophy patients. Therefore, the CFL2 isoform may play an important role in normal muscle function and muscle regeneration.

Amino Acid Sequence↗
PubMed2001

Novel approaches to treat muscular dystrophies.

Muscular dystrophies (MD) are a clinically and genetically heterogeneous group of skeletal muscle-wasting diseases. Mutations in the dystrophin gene result in dystrophin deficiency, which constitutes the pathogenic basis of Duchenne and Becker MD (DMD and BMD). Several MD are caused by mutations in other recently identified genes coding for proteins linked to the sarcolemma, the nuclear envelope or the contractile apparatus. In addition, several MD have been mapped to different chromosomal loci and for most of them, the identification of the molecular defect is underway. The immediate result is an ongoing reclassification of the MD into disorders defined not by clinical characteristics but specific genetic mutations. At present, therapy of MD is based on symptomatic treatment and supportive care. Convincing evidence for clinical efficacy is only available for corticosteroids that also suffer from frequent and severe side effects. Up to now, curative therapy is not available, although promising new molecular therapies are under investigation in animal models of MD. Current treatment strategies are discussed and a perspective for effective molecular therapy is given.

Adrenal Cortex Hormones↗
PubMed2000

Characterization of human SCO1 and COX17 genes in mitochondrial cytochrome-c-oxidase deficiency.

At least three proteins, COX17p, SCO1p, and its homologue SCO2p are thought to be involved in mitochondrial copper transport to cytochrome-c-oxidase (COX), the terminal enzyme of the respiratory chain. Recently, we and others have shown that mutations in SCO2 are associated with a lethal infantile hypertrophic cardiomyopathy (HCMP) with COX-deficiency. The majority of patients with a similar phenotype were, however, negative for SCO2 mutations, suggesting the other genes as candidates for this disorder. Here we report on the genomic organization of SCO1 and COX17 on human chromosomes 17 and 3 respectively, and the complete sequence analysis of COX17 and SCO1 in 30 patients with COX deficiency. Using a panel of human:mouse-monochromosomal hybrids, the expression of COX17 was specifically restricted to chromosome 3, indicating that the previously reported sequence on chromosome 13 represents a pseudogene. DNA sequence analysis of SCO1 and COX17 in nine patients with severe COX deficiency and fatal HCMP, and in 21 patients with other COX deficiency disorders, did not reveal any pathogenic mutations or polymorphisms. We conclude that neither SCO1 nor COX17 are common causes of COX deficiency disorders.

Cardiomegaly↗
PubMed2000

Creatine monohydrate in muscular dystrophies: A double-blind, placebo-controlled clinical study.

The authors assessed the safety and efficacy of creatine monohydrate (Cr) in various types of muscular dystrophies in a double-blind, crossover trial. Thirty-six patients (12 patients with facioscapulohumeral dystrophy, 10 patients with Becker dystrophy, 8 patients with Duchenne dystrophy, and 6 patients with sarcoglycan-deficient limb girdle muscular dystrophy) were randomized to receive Cr or placebo for 8 weeks. There was mild but significant improvement in muscle strength and daily-life activities by Medical Research Council scales and the Neuromuscular Symptom Score. Cr was well tolerated throughout the study period.

Activities of Daily Living↗
PubMed2000

Decreased aminoacylation of mutant tRNAs in MELAS but not in MERRF patients.

Mutations in human mitochondrial tRNA genes are associated with a number of multisystemic disorders. Using an assay that combines tRNA oxidation and circularization we have determined the relative amounts and states of aminoacylation of mutant and wild-type tRNAs in tissue samples from patients with MELAS syndrome (mito- chondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes) and MERRF syndrome (myoclonus epilepsy with ragged red fibers), respectively. In most, but not all, biopsies from MELAS patients carrying the A3243G substitution in the mitochondrial tRNA(Leu(UUR))gene, the mutant tRNA is under-represented among processed and/or aminoacylated tRNAs. In contrast, in biopsies from MERRF patients harboring the A8344G substitution in the tRNA(Lys)gene neither the relative abundance nor the aminoacylation of the mutated tRNA is affected. Thus, whereas the A3243G mutation may contribute to the pathogenesis of MELAS by reducing the amount of aminoacylated tRNA(Leu), the A8344G mutation does not affect tRNA(Lys)function in the same way.

Acylation↗
PubMed2000

High-dose immunoglobulin therapy in sporadic inclusion body myositis: a double-blind, placebo-controlled study.

Sporadic inclusion body myositis (s-IBM) is an acquired inflammatory muscle disease of unknown cause. In general, s-IBM presents with slowly progressive, asymmetric weakness, and atrophy of skeletal muscle. There is a mild transitory or nil responsiveness to standard immunosuppressive treatment. A controlled cross-over study of 22 s-IBM patients over 3 months showed a partial improvement in those treated with high-dose intravenous immunoglobulin therapy (IVIG) versus placebo. The present study included 22 patients aged 32-75 years and with a mean duration of disease of 5.2+/-3.6 years. They were randomized by a double-blind, placebo-controlled, cross-over design to monthly infusions of 2 g/kg bodyweight IVIG or to placebo for 6 months each, followed by the alternative treatment. After 6 and 12 months the response to treatment was evaluated, using a modified Medical Research Council scale, Neuromuscular Symptom Score (NSS), the patient's own assessment of improvement, arm outstretched time, and electromyography. No serious side effects were seen, in particular no viral infection and no major cardiac or neurological complications. Overall there was no progression of the disease in 90% of patients, unlike that which might have been expected in untreated patients. A mild and significant improvement (11%) in clinical symptoms was found using NSS, but not with other test procedures. There was a trend to mild improvement in treated patients when using other tests. Individual responses to treatment was heterogeneous. The validity of this study may be reduced by mismatch of groups with regard to age at onset and variability in disease expression. The findings of this study largely confirm those of a previous IVIG trial. Treatment with IVIG may be mildly effective in s-IBM by preventing disease progression or inducing mild improvement. Long-term studies are needed to evaluate further the benefit of IVIG therapy in s-IBM.

Adult↗
PubMed2000

Technology evaluation: edrecolomab, Centocor Inc.

Specific targeting of tumor cells may be achieved by using monoclonal antibodies to tumor antigens. Edrecolomab is a mouse-derived monoclonal IGg2A antibody directed against the human tumor-associated CO17-1A (or Ep-CAM) antigen, and is the first monoclonal antibody approved for cancer therapy. Encouraging results of several clinical trials were recently reported using edrecolomab for adjuvant therapy after surgery of Duke's C colorectal cancer. Side effects and toxicity profiles compare favorably to conventional regimens of radio- or chemotherapy. Future challenges lie in further improvement of these novel therapeutics, hopefully generating benefit for a larger number of cancer patients.

Animals↗
PubMed2000

Successful management of polyneuropathy associated with IgM gammopathy of undetermined significance with antibody-based immunoadsorption.

Peripheral polyneuropathies associated with monoclonal IgM gammopathy of undetermined significance often have a progressive course and optimal treatment has not been established. We report on a patient diagnosed with polyneuropathy associated with benign IgM gammopathy, who was successfully treated with antibody-based immunoadsorption only. The neurological symptoms of the patient improved continuously over six months of treatment. Controlled trials should be performed to define this indication for antibody-based immunoadsorption therapy.

Humans↗
PubMed1999

A common mutation (epsilon1267delG) in congenital myasthenic patients of Gypsy ethnic origin.

OBJECTIVE: Mutation analysis of the acetylcholine receptor (AChR) epsilon subunit gene in patients with sporadic or autosomal recessive congenital myasthenic syndromes (CMS). BACKGROUND: The nicotinic AChR of skeletal muscle is a neurotransmitter-gated ion channel that mediates synaptic transmission at the vertebrate neuromuscular junction. Mutations in its gene may cause congenital myasthenic syndromes. A recently described mutation in exon 12 of the AChR epsilon subunit (epsilon1267delG) disrupts the cytoplasmic loop and the fourth transmembrane region (M4) of the AChR epsilon subunit. METHODS: Forty-three CMS patients from 35 nonrelated families were clinically classified as sporadic cases of CMS (group III according to European Neuromuscular Centre consensus) and were analyzed for epsilon1267delG by PCR amplification and sequence analysis. RESULTS: The authors report the complete genomic sequence and organization of the gene coding for the epsilon subunit of the human AChR (accession number AF105999). Homozygous epsilon1267delG was identified in 13 CMS patients from 11 independent families. All epsilon1267delG families were of Gypsy or southeastern European origin. Genotype analysis indicated that they derive from a common ancestor (founder) causing CMS in the southeastern European Gypsy population. Phenotype analysis revealed a uniform pattern of clinical features including bilateral ptosis and mild to moderate fatigable weakness of ocular, facial, bulbar, and limb muscles. CONCLUSIONS: The mutation epsilon1267delG might be frequent in European congenital myasthenic syndrome patients of Gypsy ethnic origin. In general, patients (epsilon1267delG) were characterized by the onset of symptoms in early infancy, the presence of ophthalmoparesis, positive response to anticholinesterase treatment, and the benign natural course of the disease.

Adolescent↗
PubMed1999

Cloning of novel injury-regulated genes. Implications for an important role of the muscle-specific protein skNAC in muscle repair.

To gain insight into the molecular mechanisms underlying the wound repair process, we searched for genes that are regulated by skin injury. Using the differential display reverse transcription-polymerase chain reaction technique, we identified a gene that was strongly induced as early as 12 h after wounding. Sequence analysis revealed the identity of the corresponding protein with skeletal muscle nascent polypeptide-associated complex (skNAC), a recently identified muscle-specific transcription factor. By in situ hybridization and immunohistochemistry, we demonstrated the specific expression of skNAC in skeletal muscle cells of the panniculus carnosus at the wound edge. Furthermore, in vitro studies with cultured myoblasts revealed expression of skNAC in differentiating and differentiated, but not in proliferating, nondifferentiated cells. Differentiation of cultured myoblasts was accompanied by simultaneous expression of skNAC and the muscle-specific transcription factor myogenin. Our results provide the first evidence for a role of skNAC in muscle repair processes. Furthermore, they demonstrate the usefulness of our approach in identifying new players in wound repair.

Animals↗
PubMed1999

Expression of the E6 and E7 genes of human papillomavirus (HPV16) extends the life span of human myoblasts.

Primary human myoblasts (satellite cells), like other human cells, have a limited life span in vitro. Here we show that expression of the E6E7 early region from human papillomavirus type 16 can greatly extend the life span of both fetal and satellite cell-derived myoblasts and release them from dependence on the growth factors normally necessary for their proliferation. Expression of either the E6 or the E7 gene alone was not sufficient to confer this phenotype, although expression of E7 did delay cellular senescence. The steady-state level of E6E7 transcripts in clonal cultures correlated with proliferative capacity and inversely with the capacity to differentiate into multinuclear myotubes. The expression of E7 alone markedly inhibited cell fusion in both adult and fetal cultures. These effects on myoblast differentiation could be related in part to the level of retinoblastoma protein (pRb), the major cellular target of E7. Terminal differentiation of skeletal myoblasts is associated with permanent withdrawal from the cell cycle; however, continued expression of E6E7 in differentiated myotubes permits reentry of myotube nuclei into S phase in response to growth factor stimulation. These results support a key role for pRb in the acquisition and maintenance of the differentiated state in human skeletal muscle and, in cooperation with p53, in the control of proliferative capacity and response to external growth factors.

3T3 Cells↗
PubMed1999

Neuromyotonia, myocloni, sensory neuropathy and cerebellar symptoms in a patient with antibodies to neuronal nucleoproteins (anti-Hu-antibodies).

A middle-aged patient presented with subacute muscular stiffness, myocloni of both extremity and facial muscles, gait ataxia and symmetrical distal painful paraesthesias. Electrophysiologically, neuromyotonia was confirmed. High titer anti-Hu antibodies were detected, but no other paraneoplastic antibodies were found. Small-cell lung cancer was diagnosed. Under chemotherapy tumor remission was achieved and, except for minor sensory deficits, neurological symptoms disappeared. This report shows that paraneoplastic syndromes associated with antibodies to neuronal nucleoproteins (anti-Hu antibodies) may be associated with a syndrome including neuromyotonia, sensory neuropathy, cerebellar symptoms and myocloni.

Antibodies, Neoplasm↗
PubMed1999

Myopathy with trabecular muscle fibers.

A systematic review of muscle biopsies over a 15 year period in a large neurological hospital revealed 21 cases (7% of the total of non-inflammatory myopathies) with a distinctive pattern of myopathology and a limb-girdle clinical phenotype. The muscle pathology was dominated by a large prevalence (20-90%) of trabecular or lobulated fibers in which maldistribution of intermyofibrillar mitochondria produced a lobulated pattern of oxidative enzyme activity on transverse sections. The clinical picture was characterized by adult onset, slowly progressive muscle weakness affecting mainly proximal limb musculature, although mild distal weakness was also present in 60% of the cases. The trabecular pattern of oxidative enzyme reaction reflects maldistribution of the intermyofibrillar mitochondria; this may be caused by malfunction of a putative anchoring mechanism. While trabecular fibers can occur as a nonspecific alteration of muscle fibers in many diverse myopathies, the high prevalence of trabecular fibers as the dominant pathology in trabecular fiber myopathy makes it a distinctive (though not necessarily etiologically homogeneous) clinico-pathological entity.

Adolescent↗
PubMed1999

Localization of transforming growth factor beta in association with neuromuscular junctions in adult human muscle.

Transforming growth factors-beta 1, 2, and 3 are known for their regulatory function in embryogenesis, fibrogenesis, and tissue repair of different cell types. A trophic function of TGF-beta subclasses for motoneurons has been shown in vitro. TGF-beta 1 is a potent survival factor for cultured embryonic rat motoneurons. In addition, TGF-beta 1 stimulates proliferation of rat Schwann cells. Recently, TGF-beta 2 has been reported to be associated with the subsynaptic nuclei of mature rat neuromuscular junctions. In this study, we investigated the expression of TGF-beta 1, 2, and 3 at neuromuscular junctions in skeletal muscle of 11 adults without neuromuscular disease. On muscle biopsies, neuromuscular junctions were depicted by acetylcholine esterase reaction and acetylcholine receptor antibodies. TGF-beta 1; 2, and 3 were stained immunohistochemically with monoclonal antibodies. Some muscle fibers showed low levels of inhomogeneous immunoreactivity for both TGF-beta 1 and TGF-beta 3. Intense immunoreactivity of TGF-beta 1 and 3 was shown at the postsynaptic area of neuromuscular junctions. TGF-beta 2 was expressed in the same subcellular distribution, but less strongly. In conclusion, the colocalization of TGF-beta with neuromuscular junctions may suggest a significant function in neuromuscular communication.

Acetylcholinesterase↗