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Biomedical subjects

W K Engel

Publications and source records attributed to W K Engel.

At least 55 records · Page 3Linked to original sources
PubMed1996

Use of anti-neurofilament antibody to identify paired-helical filaments in inclusion-body myositis.

Paired-helical filaments (PHFs) are an important diagnostic criterion of the inclusion-body myositis (IBM) muscle biopsy; but, until now, their presence could be identified only by electronmicroscopy. In this report, we describe an easy immunocytochemical procedure, utilizing commercially available antibody, that enables reliable identification of muscle PHFs by light microscopy. This procedure greatly facilitates diagnosis of IBM.

Antibodies, Monoclonal↗
PubMed1996

Apolipoprotein E and apolipoprotein E messenger RNA in muscle of inclusion body myositis and myopathies.

Sporadic inclusion body myositis and the hereditary inclusion body myopathies are severe, progressive muscle diseases, characterized pathologically by vacuolated muscle fibers containing paired helical filaments. We immunostained muscle biopsy specimens from sporadic inclusion body myositis, hereditary inclusion body myopathy, disease control, and normal patients with several antibodies against apolipoprotein E (ApoE). Approximately 80 to 90% of the vacuolated muscle fibers of sporadic inclusion body myositis contained well-defined, strongly immunoreactive ApoE inclusions. In hereditary inclusion body myopathy, only rare vacuolated fibers had immunoreactive inclusions, whereas most had diffuse cytoplasmic ApoE immunoreactivity. Ultrastructurally, ApoE immunoreactivity in sporadic myositis was localized mainly to the paired helical filaments. By contrast, in the hereditary form, ApoE immunoreactivity occurred on material in close proximity to the paired helical filaments, but never was on the paired helical filaments. In both muscle diseases, ApoE was also on the 6- to 10-nm filaments and amorphous material. In the sporadic form, ApoE-immunoreactive deposits colocalized with Congo red-positive deposits; however, in muscle fibers from patients with hereditary disease there was no congophilia. ApoE messenger RNA was not detectable in muscle fibers from patients with hereditary or sporadic disease but was expressed abundantly in muscle macrophages. In all control and inclusion body myositis or myopathy biopsy specimens, ApoE immunoreactivity was strong at the postsynaptic domain of neuromuscular junctions; nonjunctional regions of normal fibers were negative for ApoE. ApoE immunoreactivity occurred diffusely in regenerating muscle fibers, a subset of which had detectable ApoE messenger RNA.

Amyotrophic Lateral Sclerosis↗
PubMed1996

Difference in expression of phosphorylated tau epitopes between sporadic inclusion-body myositis and hereditary inclusion-body myopathies.

Sporadic inclusion-body myositis (s-IBM) and the hereditary inclusion-body myopathies (h-IBMs) are severe and progressive muscle diseases, characterized pathologically by vacuolated muscle fibers containing paired-helical filaments (PHFs). An interesting feature of the s- and h-IBM muscle phenotype is its striking similarity to Alzheimer-disease (AD) brain. We immunostained muscle biopsies of 9 s-IBM patients, 9 autosomal-recessive h-IBM patients, 1 autosomal-dominant h-IBM patients, and 18 normal and disease-controls with several antibodies known to react with the hyperphosphorylated tau of AD-PHFs. Those included SMI-31, SMI-310, PHF-1, and AT8. In both s- and h-IBM, virtually all vacuolated muscle fibers had strongly immunoreactive inclusions with SMI-31, and by immuno-electronmicroscopy SMI-31 was exclusively localized to PHFs. Approximately 40 to 50% of both s- and h-IBM vacuolated muscle fibers were also immunoreactive with AT8 antibody. To the contrary, in h-IBM, there was no immunoreactivity with SMI-310 and PHF-1 antibodies, whereas in s-IBM the vacuolated muscle fibers had strong immunoreactivity with those two antibodies. By immunoelectronmicorscopy, SMI-310 and PHF-1 also were localized to PHFs. Within s-IBM muscle fibers, the structures immunoreactive with SMI-310 were congophilic, whereas h-IBM muscle fibers did not have congophilia. Our studies: (a) demonstrate a distinct difference between s-IBM and the h-IBMs in regard to expression of immunoreactive phosphorylated tau and congophilia; (b) demonstrate a new "diagnostic duo" combination of SMI-31 and SMI-310 antibodies for identifying and distinguishing s-IBM and the h-IBMs; and (c) provide another close similarity of pathologic phenotypes between s-IBM muscle and AD brain, suggesting that similar cellular pathogenic mechanisms may be active in both diseases.

Adult↗
PubMed1995

Human muscle macrophages express beta-amyloid precursor and prion proteins and their mRNAs.

Well-characterized antibodies against beta-amyloid precursor protein (beta APP) and prion protein (PrP), and specific cRNA probes, were used to localize beta APP and PrP and their mRNAs in human muscle macrophages. Macrophages present in muscle biopsies of 51 patients with various neuromuscular disorders showed accumulation of beta APP and PrP, and strongly expressed beta APP and PrP mRNAs. These were present in all muscle macrophages unrelated to their localization within the muscle tissue or diagnosis. Our study provides the first demonstration that human muscle resident macrophages synthesize and accumulate beta APP and PrP. We suggest that those proteins play a role in biology of muscle macrophages, including their participation in inflammatory and immune responses.

Adolescent↗
PubMed1995

New advances in the understanding of sporadic inclusion-body myositis and hereditary inclusion-body myopathies.

This review emphasizes new advances in seeking the pathogenic mechanisms of sporadic inclusion-body myositis and hereditary inclusion-body myopathy syndromes. Clinical and pathologic similarities and differences between sporadic and hereditary forms are described. Hypotheses are presented regarding the possible causes and consequences of abnormally accumulated intramyofiber beta-amyloid precursor protein (beta APP) (including beta-amyloid protein and C- and N-terminal epitopes), hyperphosphorylated tau, alpha 1-antichymotrypsin, apolipoprotein E, prion protein, ubiquitin, nicotinic acetylcholine receptor and its 43-kD associated protein, fibroblast growth factor, and transforming growth factor-beta. Also increased are beta APP mRNA and prion protein mRNA. Striking similarities between the pathology of muscle specimens from sporadic inclusion-body myositis and samples from the brains of patients with Alzheimer's disease in regard to Congo red positivity and accumulations of several proteins are discussed. Because most of the proteins that pathologically accumulate throughout the abnormal muscle fibers also accumulate focally at normal human neuromuscular junctions, the possible "junctionalization" of nonjunctional nuclei as a pathogenic mechanism in the muscle fiber is discussed.

Diagnosis, Differential↗
PubMed1994

Single-fiber electromyography in neuromuscular disorders: correlation of muscle histochemistry, single-fiber electromyography, and clinical findings.

We performed single-fiber electromyography (SFEMG) and correlated the results with muscle-biopsy histochemistry in 56 patients with various neuromuscular diseases. Increased muscle-fiber density, delineated by SFEMG, was most prominent in diseases of ordinary denervation, namely motor neuron disorders and peripheral neuropathies, and it correlated with histochemical fiber type grouping. Both phenomena reflect denervation followed by reinnervation. In patients with central core disease and rod disease, fiber density was not increased despite massive type I fiber predominance. The normal distribution of type I fiber subtypes in those patients indicated tht their fiber predominance was not due to sprouting and reinnervation, but probably to paucity of the type II fibers. In type I fiber hypotrophy with central nuclei, fiber density was increased, perhaps attributable to the small diameter and consequent denser packing of the type I fibers. Fiber density was slightly increased in the majority of patients with acid-maltase deficiency, limb-girdle dystrophy, and polymyositis, in nearly half with mitochondrial myopathy, and in 1 older Duchenne dystrophy patient. In these myopathic disorders, myogenous deinnervation (followed by reinnervation) is one possible explanation. Normal fiber density was present in all patients with muscle phosphorylase deficiency, myotonia congenita, and in the hypokalemic periodic paralysis patients under age 40.

Adult↗
PubMed1994

Alpha 1-antichymotrypsin is strongly immunolocalized at normal human and rat neuromuscular junctions.

alpha 1-Antichymotrypsin (alpha 1-ACT) is an early-stage acute-phase plasma protein and a serpin that preferentially inactivates chymotrypsin, cathepsin G, and chymase. Using immunofluorescence with four rabbit polyclonal and two monoclonal specific antibodies against human alpha 1-ACT, we have localized alpha 1-ACT at human and rat neuromuscular junctions (NMJs). Strong alpha 1-ACT immunoreactivity (IR) was present at all NMJs identified by bound alpha-bungarotoxin (alpha-BT). alpha 1-ACT immunoreactivity typically extended slightly deeper into the muscle fiber than alpha-BT, and it closely co-localized with immunoreactivities of post-synaptic desmin, beta-amyloid precursor protein, and dystrophin at the same double- or triple-labeled NMJs. Topography of alpha 1-ACT-IR was the same at human and rat NMJs. The muscle non-junctional sarcolemma was either not immunoreactive or was only very slightly so. When the primary antibody was omitted, absorbed, or replaced by a non-immune serum, there was no immunostaining. Thus, alpha 1-ACT is a novel component of the NMJ. Although its role in the postsynaptic domain of the NMJ is unknown, it might be involved in the interaction between the presynaptic and postsynaptic components and/or inhibit excessive or unwanted serine proteases that may exist in the region of the NMJ.

Animals↗
PubMed1994

Expression of beta-amyloid precursor protein gene is developmentally regulated in human muscle fibers in vivo and in vitro.

Regenerating muscle fibers in 25 human muscle biopsies, obtained from patients with a variety of neuromuscular diseases, manifested increased mRNA for the beta-amyloid precursor protein (beta APP) that contains the Kunitz-type protease inhibitor (KPI) motif, whereas adult human muscle fibers were negative in their vast non-extrajunctional region. Aneurally cultured normal human muscle fibers also expressed strong KPI-beta APP mRNA signal, which became significantly down-regulated during muscle differentiation. Our study demonstrates that in human muscle KPI-beta APP mRNA is developmentally regulated, and it suggests that beta APP may play a role in human muscle development.

Adolescent↗
PubMed1994

Idiopathic inflammatory myopathies: inclusion-body myositis, polymyositis, and dermatomyositis.

In this review, the main emphasis is on new advances concerning sporadic inclusion-body myositis and hereditary inclusion-body myopathy. Polymyositis and dermatomyositis are reviewed briefly. Hypotheses are presented regarding the possible cause and significance of abnormally accumulated beta-amyloid protein, two other epitopes of beta-amyloid precursor protein, hyperphosphorylated tau, alpha 1-antichymotrypsin, ubiquitin, and prion protein in sporadic inclusion-body myositis and hereditary inclusion-body myopathy. Because most of those proteins are also accumulated at the neuromuscular junction, "junctionalization" of other muscle fiber nuclei is a possibility. Attention is given to the fact that vacuolated muscle fibers in hereditary inclusion-body myopathy may represent early changes because they are virtually free of congophilic amyloid deposit but, like sporadic inclusion-body myositis, contain large accumulations of beta-amyloid protein and prion.

Aged↗
PubMed1994

Abnormal accumulation of prion protein mRNA in muscle fibers of patients with sporadic inclusion-body myositis and hereditary inclusion-body myopathy.

Sporadic inclusion-body myositis is the most common progressive muscle disease of older patients. 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 brain, and Congo-red positivity. Hereditary inclusion-body myopathy designates patients cytopathologically similar but without inflammation. In both muscle diseases, prion, and several proteins characteristic of Alzheimer brain--eg, beta-amyloid protein and hyperphosphorylated tau (which normally are expressed mainly in neurons), and apolipoprotein E--are abnormally accumulated in vacuolated muscle fibers, by unknown mechanisms. We now demonstrate in both muscle diseases that prion mRNA is strongly expressed in the vacuolated muscle fibers, which suggests that their accumulated prion protein results, at least partly, from increased gene expression. This, to our knowledge, is the first demonstration of abnormally increased prion mRNA in human disease. Another novel finding is the increased prion mRNA in human muscle macrophages, and both increased prion protein and prion mRNA in regenerating muscle fibers. The latter indicates that prion may play a role in human muscle development.

Adult↗
PubMed1994

Twisted tubulofilaments of inclusion body myositis muscle resemble paired helical filaments of Alzheimer brain and contain hyperphosphorylated tau.

We immunostained muscle biopsies of 8 patients with sporadic inclusion body myositis (S-IBM), 7 patients with autosomal recessive hereditary inclusion body myopathy (H-IBM) (both diseases being characterized by similar muscle fiber vacuoles containing inclusions), and 11 normal and disease controls. We used the following well-characterized antibodies against tau protein: Tau-1, Alz-50, and anti-paired helical filament (PHF) antiserum. By light microscopy, in all S-IBM muscle biopsies virtually all vacuoles immunoreactive for ubiquitin and beta-amyloid protein also contained inclusions immunoreactive with Alz-50 and anti-PHF antiserum. With tau-1 antibody, strong immunoreactivity in the vacuoles was obtained only after dephosphorylation of muscle sections. By electronmicroscopy, all three antibodies immunodecorated exclusively cytoplasmic twisted tubulofilaments (TTFs). In H-IBM, virtually all ubiquitin and beta-amyloid-positive muscle fiber vacuoles contained inclusions immunoreactive with anti-PHF antiserum, but in only 40% of those fibers were the inclusions immunoreactive with Alz-50. In six H-IBM patients there were no tau-1 immunoreactive inclusions in any of their vacuolated muscle fibers; in one patient, 24% of the vacuolated fibers had tau-1 immunoreactivity. By demonstrating that hyperphosphorylated tau, which is characteristic of Alzheimer brain PHFs, is a component of S-IBM-muscle TTFs (which are also ultrastructurally similar to PHFs), our study: 1) provides the first demonstration of abnormally accumulated tau in nonneural tissue and 2) suggests that the cytopathogenesis in Alzheimer brain and S-IBM muscle may share some similar mechanisms. Whether the difference in tau immunoreactivity between S-IBM and most of the H-IBM patients reflects a difference in genetically determined transcriptional or posttranslational modifications of tau protein or other factors remains to be determined.

Adult↗
PubMed1993

Prion protein is abnormally accumulated in inclusion-body myositis.

In muscle biopsies of 8 sporadic inclusion-body myositis (S-IBM) and 4 hereditary inclusion-body myopathy (H-IBM) patients, vacuolated muscle fibers contained within their vacuoles strongly immunoreactive inclusions with 2 polyclonal and 1 monoclonal antibodies against prion protein (PrP). By light-microscopy, PrP deposits co-localized with beta-amyloid protein (A beta) and ubiquitin (Ub). By immuno-electronmicroscopy, both PrP and A beta were present on amorphous material and on 6-10 nm amyloid-like fibrils; and PrP and Ub co-localized on cytoplasmic twisted tubulofilaments (TTFs) and on amorphous material. Our study provides the first demonstration of abnormally accumulated PrP in pathological tissue other than brain, and it suggests that PrP may play a role in the pathogenesis of IBM.

Adult↗
PubMed1993

Prion protein is strongly immunolocalized at the postsynaptic domain of human normal neuromuscular junctions.

Using three well-characterized polyclonal and monoclonal antibodies against prion protein (PrP), we demonstrated a strong concentration of PrP at human neuromuscular junctions (NMJs). Applying double and triple fluorescence-labeling, we found that PrP immunoreactivity exactly co-localized with alpha-bungarotoxin (alpha-BT) identified acetylcholine receptors, as well as with the high junctional concentrations of beta-amyloid precursor protein, beta-amyloid protein, desmin, ubiquitin and dystrophin. Therefore, PrP was considered to be located on the postsynaptic muscle membrane. At all NMJs identified by bound alpha-BT, strong PrP immunoreactivity was obtained with all PrP antibodies. This appears to be the first demonstration of PrP concentrated at human NMJs.

Antibodies, Monoclonal↗
PubMed1993

beta-Amyloid precursor epitopes in muscle fibers of inclusion body myositis.

Sporadic inclusion body myositis (IBM) and hereditary inclusion body myopathy (hIBM) are severe and progressive muscle diseases, characterized pathologically by vacuolated muscle fibers that contain 15- to 21-nm cytoplasmic tubulofilaments (CTFs). Those vacuolated muscle fibers also contain abnormally accumulated ubiquitin and beta-amyloid protein (A beta), and they contain amyloid in beta-pleated sheets as indicated by Congo red and crystal violet positivity. Using several well-characterized antibodies, we have now demonstrated that, in addition to A beta, two other epitopes, N-terminal and C-terminal, of the beta-amyloid precursor protein (beta PP) are abnormally accumulated in IBM vacuolated muscle fibers and similarly in hIBM. At the light microscopy level, immunoreactivities of N- and C-epitopes of beta PP closely colocalized with A beta and ubiquitin immunoreactivities. However, by immunogold electronmicroscopy, even though N-, C-, and A beta epitopes of beta PP and ubiquitin colocalized at the amorphous and dense floccular structures, only A beta was localized to the 6- to 10-nm amyloid-like fibrils and only ubiquitin was localized to CTFs. beta PP immunoreactive structures were often in proximity to CTFs, but CTFs themselves never contained beta PP immunoreactivities. The fact that A beta but not C- or N-terminal epitopes of beta PP localized to the 6- to 10-nm amyloid-like fibrils suggests that free A beta might be generated during beta PP processing and, after aggregation, may be responsible for the amyloid present within IBM muscle fibers. Our study demonstrates that three epitopes of beta PP accumulate abnormally in diseased human muscle, and therefore this phenomenon is not unique to Alzheimer's disease, Down's syndrome brain, and Dutch-type cerebrovascular amyloidosis.

Adolescent↗
PubMed1993

Tropomodulin is highly concentrated at the postsynaptic domain of human and rat neuromuscular junctions.

Tropomodulin is expressed in skeletal muscle and recent studies suggest that tropomodulin is associated with synaptic membranes. Therefore, we have examined neuromuscular junctions by immunofluorescence analysis for tropomodulin localization. Anti-tropomodulin antibodies generated against either the whole protein or a 15-amino acid peptide fragment label human neuromuscular junctions as demonstrated by colocalization with alpha-bungarotoxin label. Tropomodulin labeling also colocalizes with desmin and beta-amyloid proteins which are concentrated in the postsynaptic region. Comparable results are found with immunostaining of neuromuscular junctions in rat diaphragm muscle. These immunofluorescence results suggest that tropomodulin is an integral component of the cytoskeletal lattice associated with the postsynaptic region of neuromuscular junctions.

Animals↗