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Biomedical subjects

W K Engel

Publications and source records attributed to W K Engel.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cultured inclusion-body myositis muscle fibers do not accumulate beta-amyloid precursor protein and can be innervated.

Cultured muscle fibers from patients with sporadic inclusion-body myositis (s-IBM), similar to normal control muscle fibers, 1) did not have beta-amyloid precursor protein (betaAPP) immunoreactivity; and 2) became normally innervated, as evidenced by the following features: full cross-striation, continuous contraction, and acetylcholinesterase and acetylcholine receptors accumulated only at neuromuscular junctions. Thus, factors responsible for betaAPP accumulation and denervation-like changes in s-IBM muscle biopsies are not operative in the relatively short-term, non-aged, cultured s-IBM muscle fibers.

Aged↗
PubMed1999

Localization of survival motor neuron protein in human apoptotic-like and regenerating muscle fibers, and neuromuscular junctions.

Mutations in the gene encoding survival motor neuron (SMN) protein are found in > 98% of patients with autosomal-recessive spinal muscular atrophy. We investigated the possible role of SMN in normal and abnormal human muscle by immunostaining biopsies of 20 patients with various neuromuscular diseases using monoclonal antibodies against SMN. SMN was strongly expressed cytoplasmically in chronic peripheral neuropathies, in about 80% of chronically denervated, very atrophic muscle fibers containing clumps of TUNEL-positive pyknotic nuclei: about 60% of those fibers also had cytoplasmic Bcl-2 and Bax immunoreactivity. In regenerating muscle fibers of various myopathies SMN co-localized with desmin, Bcl-2 and Bax; it was also present at the postsynaptic domain of normal human neuromuscular junctions. Thus, SMN may play a role in normal and pathological processes of adult human muscle fibers.

Apoptosis↗
PubMed1999

Diplopia secondary to aniseikonia associated with macular disease.

OBJECTIVE: To provide an explanation for diplopia and the inability to fuse in some patients with macular disease. METHODS: We identified 7 patients from our practices who had binocular diplopia concurrent with epiretinal membranes or vitreomacular traction. A review of the medical records of all patients was performed. In addition to complete ophthalmologic and orthoptic examinations, evaluation of aniseikonia using the Awaya New Aniseikonia Tests (Handaya Co Ltd, Tokyo, Japan) was performed on all patients. RESULTS: All patients were referred for troublesome diplopia. Six of the patients had epiretinal membranes and 1 had vitreomacular traction. All 7 patients had aniseikonia, ranging from 5% to 18%. In 5 of the patients the image in the involved eye was larger, and in the other 2 patients it was smaller than in the fellow eye. All patients had concomitant small-angle strabismus and at least initially did not fuse when the deviation was offset with a prism. Response to optical management and retinal surgery was variable. CONCLUSIONS: Aniseikonia caused by separation or compression of photoreceptors can be a contributing factor to the existence of diplopia and the inability to fuse in patients with macular disease. Concomitant small-angle strabismus and the inability to fuse with prisms may lead the clinician to the incorrect diagnosis of central disruption of fusion. Surgical intervention does not necessarily improve the aniseikonia.

Adult↗
PubMed1998

Impaired innervation of cultured human muscle overexpressing betaAPP experimentally and genetically: relevance to inclusion-body myopathies.

To investigate whether abnormally accumulated betaAPP may be responsible for denervation of muscle fibers that are present in hereditary inclusion-body myopathy (h-IBM) and sporadic inclusion-body myositis (s-IBM), we cultured five h-IBM and eight normal muscle biopsies. In eight other experiments, a 3 kb human 751-betaAPP-cDNA was transferred, using adenovirus vector, into cultured normal myotubes immediately after myoblast fusion. In all experiments, cultured muscle fibers were co-cultured with fetal rat spinal cord. Controls had no detectable betaAPP epitopes, whereas betaAPP epitopes were greatly increased in cultured h-IBM muscle and in cultured normal muscle after betaAPP-gene transfer. Innervated normal cultured muscle fibers were continuously contracting and fully cross-striated, and they had acetylcholine receptors (AChRs) and acetylcholinesterase (AChE) accumulated only at the neuromuscular junctions (NMJs). By contrast, both groups of betaAPP-overexpressing cultured muscle fibers were not contracting and not cross-striated; and did not have NJMs containing AChRs and AChE. Our results suggest that over-expression of betaAPP in cultured muscle fibers inhibits their innervation, and that the accumulation of betaAPP in muscle fibers of both h- and s-IBM patients may be responsible for their not becoming or remaining properly innervated or reinnervated, i.e. a 'myogenous-dysinnervation' mechanism.

Adult↗
PubMed1998

Immunolocalization of transcription factor NF-kappaB in inclusion-body myositis muscle and at normal human neuromuscular junctions.

To investigate whether nuclear factor kappaB (NF-kappaB) is involved in the pathogenesis of inclusion-body myositis (IBM), we immunostained muscle biopsies of eight patients with IBM with specific antibodies against its p50 and p65 subunits. Approximately 70% of IBM vacuolated muscle fibers had strong focal accumulations of both NF-kappaB p50 and p65, which by immunoelectronmicroscopy, localized mainly to clusters of paired-helical filaments (PHFs). Virtually all necrotic fibers, in various muscle biopsies, had diffusely strong p50 immunoreactivity, whereas p65 immunoreactivity was present only in a small subset of necrotic fibers. At all neuromuscular junctions, postsynaptically there was strong p65 but no p50 immunoreactivity. Our data suggest that NF-kappaB plays a role in IBM pathogenesis. Different distributions of NF-kappaB subunits in necrotic fibers and at normal neuromuscular junctions (NMJs) suggests different roles of each subunit in human muscle pathology and physiology.

Humans↗
PubMed1998

Sporadic inclusion-body myositis and its similarities to Alzheimer disease brain. Recent approaches to diagnosis and pathogenesis, and relation to aging.

Sporadic inclusion-body myositis (s-IBM) is the most common, debilitating and progressive muscle disease beginning at the age 50 or later. The most characteristic pathologic feature is vacuolar degeneration of muscle fibers accompanied by intrafiber congophilia and clusters ("tangles") of paired-helical filaments, containing phosphorylated tau. An unusual feature of sporadic inclusion-body myositis is accumulation within its abnormal muscle fibers of several proteins that are characteristic of Alzheimer disease brain, including epitopes of beta-amyloid precursor protein (betaAPP), phosphorylated tau, alpha-1-antichymotrypsin, apolipoprotein E, and presenilin-1. Indicators of oxidative stress are also present within abnormal s-IBM muscle fibers. In this review, we describe new advances seeking the pathogenic mechanism of sporadic inclusion-body myositis. We hypothesize on the possible pathogenic role of abnormally accumulated proteins, and we propose that important contributory factors leading to inclusion-body myositis are the milieu of muscle-fiber aging and oxidative stress. In addition, we present evidence that overexpression of adenovirus-transferred betaAPP gene in cultured human muscle fibers induces aspects of the inclusion-body myositis phenotype, and suggest that betaAPP-overexpression is an early event in the pathogenic cascade causing inclusion-body myositis.

Alzheimer Disease↗
PubMed1998

Nitric oxide-induced oxidative stress in autosomal recessive and dominant inclusion-body myopathies.

Autosomal-recessive and autosomal-dominant hereditary inclusion-body myopathies are severe, progressive muscle diseases, characterized pathologically by vacuolated muscle fibres containing paired helical filaments. We immunostained muscle biopsy specimens from quadriceps-sparing autosomal-recessive and autosomal-dominant inclusion-body myopathy subjects, disease-control subjects and normal patients, utilizing isoform-specific antibodies against the neuronal and inducible forms of nitric oxide synthase, and antibodies against nitrotyrosine. Approximately 75% of the vacuolated muscle fibres in all recessive and dominant inclusion-body myopathy patients contained inclusions strongly immunoreactive with antibodies against neuronal and inducible nitric oxide synthase which, by immunoelectron microscopy, were colocalized to clusters of tubulofilaments (previously shown, by us, to be paired helical filaments). Strong nitrotyrosine immunoreactivity was in the form of multiple dots and large granular patches, which ultrastructurally did not immunolocalize to tubulofilaments. Excess intracellular nitric oxide can combine with superoxide to produce highly toxic peroxynitrite, which can nitrate tyrosines of proteins. The presence of nitrotyrosine is indicative of nitric oxide-induced oxidative stress. Our data suggest that oxidative stress plays a role in the pathogenic cascade of hereditary inclusion-body myopathies.

Genes, Dominant↗
PubMed1998

Sporadic inclusion-body myositis and hereditary inclusion-body myopathies: current concepts of diagnosis and pathogenesis.

We discuss the pathologic diagnostic criteria and review the major new advances related to seeking the pathogenic mechanism of sporadic inclusion-body myositis (s-IBM) and hereditary inclusion-body myopathy (h-IBM). A classification of the various h-IBM syndromes is also presented. The several forms of the h-IBMs have different genetic transmissions and probably different genetic defects. In neither s-IBM nor the h-IBMs are the sequential steps of the pathogenic cascade understood. Because s-IBM and the h-IBMs have a number of characteristic pathologic features in common, we postulate that their different causes trigger the same upstream aberration leading to a similar downstream cascade of pathologic events, which are ultimately responsible for the characteristic muscle-fiber degeneration. Muscle-biopsy and experimental evidence is given supporting our hypothesis that overexpression of beta-amyloid precursor protein within abnormal muscle fibers is an early upstream event causing the pathogenic cascade. We also present evidence supporting our concept that muscle aging and oxidative stress are important factors contributing to the s-IBM-specific muscle fiber destruction. Additionally, the intriguing parallels between the pathologic phenotype of IBM muscle fibers and Alzheimer's disease brain are summarized.

Aging↗
PubMed1998

Light and electron microscopic immunolocalization of presenilin 1 in abnormal muscle fibers of patients with sporadic inclusion-body myositis and autosomal-recessive inclusion-body myopathy.

Sporadic inclusion-body myositis (s-IBM) is the most common progressive muscle disease of older persons. The muscle biopsy demonstrates mononuclear cell inflammation and vacuolated muscle fibers containing paired helical filaments and 6- to 10-nm fibrils, both resembling those of Alzheimer disease brain and Congo red positivity. The term hereditary inclusion-body myopathies (h-IBMs) designates autosomal-recessive or autosomal-dominant disorders with muscle biopsies cytopathologically similar to s-IBM but without inflammation. Vacuolated muscle fibers of both s-IBM and the h-IBMs contain accumulations of several "Alzheimer-characteristic proteins" including beta-amyloid protein and beta-amyloid precursor protein, and their paired helical filaments are composed of phosphorylated tau. We used six well characterized antibodies against several residues of presenilin 1 (PS1) to immunostain muscle biopsies of 12 patients with s-IBM, 5 patients with autosomal-recessive inclusion-body myopathy, and 16 normal and disease controls. Seventy to eighty percent of the vacuolated muscle fibers of both s-IBM and autosomal-recessive inclusion-body myopathy had inclusions that were strongly PS1-immunoreactive, which by immunoelectron microscopy localized mainly to paired helical filaments and 6- to 10-nm filaments. None of the control biopsies had PS1-positive inclusions characteristic of the s- and h-IBM abnormal muscle fibers. Mutations of the newly discovered PS1 gene are responsible for early-onset familial Alzheimer disease (AD), and PS1 is abnormally accumulated in sporadic and familial AD brain. Our study provides the first demonstration of PS1 abnormality in non-neural tissue and in diseases other than AD and suggests that the cytopathogenesis in AD brain and IBM muscle may share similarities.

Adult↗
PubMed1997

Beta APP gene transfer into cultured human muscle induces inclusion-body myositis aspects.

Direct transfer of the beta-amyloid precursor protein (beta APP) gene into cultured normal human muscle, using recombinant adenovirus vector, was sufficient to induce several of the typical light microscopic, electron microscopic (EM), and EM-immunochemical aspects of the inclusion-body myositis (IBM) phenotype, including congophilia, clusters of amyloid-beta-positive 6-10 nm filaments, and 15-21 nm tubulofilamentous inclusions in the nuclei. Our results suggest that excessive production of intracellular beta APP may play an important role in the pathogenic cascade leading to the IBM phenotype.

Amyloid beta-Protein Precursor↗
PubMed1997

Immunolocalization of nitric oxide synthases at the postsynaptic domain of human and rat neuromuscular junctions--light and electron microscopic studies.

Neuronal (n) and inducible (i) nitric oxide synthase (NOS) were immunolocalized at the postsynaptic domain of human and rat neuromuscular junctions (NMJs) by light and electron microscopy. We applied polyclonal and monoclonal antibodies for colocalization with three other synaptic proteins, utilizing double and triple fluorescence labeling, and gold and peroxidase for immunoelectron microscopy. By light microscopy, nNOS and iNOS colocalized with desmin and dystrophin, known postsynaptic components, but not with neurofilament protein, a presynaptic component. By electronmicroscopy, nNOS, but not iNOS, colocalized postsynaptically on the same structures as desmin; iNOS was also postsynaptic, but did not colocalize with desmin immunoreactivity. At the NMJs of Duchenne muscular dystrophy patients, both nNOS and iNOS were strongly immunoreactive. At the NMJs of a patient with myasthenia gravis, nNOS was weaker than in controls. Total denervation of rat sciatic nerve did not cause any decrease of nNOS or iNOS immunoreactivity 7 days thereafter. At 15 days after denervation, there was a gradual decrease of immunoreactivity, and immunoreactivity disappeared 30 days after denervation, corresponding to the ultrastructurally detectable disorganization of the postsynaptic region. This seems to be the first combined light and electron microscopic description of the postsynaptic localization of nNOS and iNOS at human and rat NMJs.

Adolescent↗
PubMed1996

Increase of nitric oxide synthases and nitrotyrosine in inclusion-body myositis.

To investigate the possible role of nitric oxide (NO)-induced 'oxidative stress' in the pathogenesis of inclusion-body myositis (IBM), we immunostained muscle biopsies of 12 patients with IBM with isoform-specific antibodies against the neuronal and inducible forms of nitric oxide synthase and with antibodies against nitrotyrosine. Between 70 and 80% of IBM vacuolated muscle fibers contained inclusions strongly immunoreactive with all three antibodies, which by immuno-electronmicroscopy co-localized mainly to cytoplasmic paired-helical filaments, and also to amorphous structures and floccular material. Excess intracellular NO can combine with superoxide to produce highly reactive peroxynitrite which can nitrate tyrosines of proteins. The presence of nitrotyrosine is indicative of NO-induced "oxidative stress'. Our data suggest that this mechanism may play a pathogenic role in IBM.

Enzyme Induction↗
PubMed1996

Transfer of beta-amyloid precursor protein gene using adenovirus vector causes mitochondrial abnormalities in cultured normal human muscle.

As in Alzheimer-disease (AD) brain, vacuolated muscle fibers of inclusion-body myositis (IBM) contain abnormally accumulated beta-amyloid precursor protein (beta APP), including its beta-amyloid protein epitope, and increased beta APP-751 mRNA. Other similarities between IBM muscle and AD brain phenotypes include paired helical filaments, hyperphosphorylated tau protein, apolipoprotein E, and mitochondrial abnormalities, including decreased cytochrome-c oxidase (COX) activity. The pathogenesis of these abnormalities in IBM muscle and AD brain is not known. We now report that direct transfer of the beta APP gene, using adenovirus vector, into cultured normal human muscle fibers causes structural abnormalities of mitochondria and decreased COX activity. In this adenovirus-mediated beta APP gene transfer, we demonstrated that beta APP overproduction can induce mitochondrial abnormalities. The data suggest that excessive beta APP may be responsible for mitochondrial and COX abnormalities in IBM muscle and perhaps AD brain.

Adenoviridae↗