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Biomedical subjects

A G Engel

Publications and source records attributed to A G Engel.

At least 127 records · Page 7Linked to original sources
PubMed1990

Microvascular changes in early and advanced dermatomyositis: a quantitative study.

In adult dermatomyositis 10 muscle specimens with no or minimal histological alterations were compared with 7 that showed typical alterations. Five specimens from patients with inclusion body myositis, 5 from patients with polymyositis, and 8 from normal subjects served as controls. Vascular endothelium, visualized with the lectin Ulex europaeus agglutinin I, and complement membrane attack complex were demonstrated in the same cryostat sections by paired immunofluorescence. Large randomly selected fields were analyzed to determine the number of capillaries per square millimeter of fiber area (capillary density), per 1,000-microns 2 area of each muscle fiber (capillary index), and in 100 x 100-microns grid squares. In dermatomyositis specimens with minimal structural alterations there was focal capillary depletion, the capillary density was significantly reduced, and the frequency distributions of the capillary index and grid count were shifted to the left. In advanced dermatomyositis specimens, the findings were similar but more severe. In both kinds of specimens, clusters of capillaries reacted for complement membrane attack complex. The 2 patients with the highest proportion of vessels positive for membrane attack complex had a fulminant and fatal course. In polymyositis and inclusion body myositis specimens, the capillaries had a normal overall density and none reacted for membrane attack complex. The findings imply that the capillaries are an early and specific target of the disease process in dermatomyositis.

Adult↗
PubMed1990

Adult phosphorylase b kinase deficiency.

Phosphorylase b kinase deficiency affecting muscle has been observed infrequently in children with weakness and hepatomegaly, and in 2 adults with cramps on exertion. We observed 2 additional adults with phosphorylase b kinase deficiency: Patient 1, aged 58, had progressive, predominantly distal weakness since age 46 but no cramps on exertion; Patient 2, aged 26, had cramps on exertion since age 6 but no weakness. Lactate production on ischemic exercise was impaired only in Patient 1. The serum creatine kinase level was elevated in both. Muscle specimens showed focal glycogen excess in both, and a necrotizing myopathy and mild denervation atrophy in Patient 1. Muscle phosphorylase b kinase activity was 0.5% and 8.9% of the lowest control value in Patients 1 and 2, respectively; erythrocyte phosphorylase b kinase activity was normal in both; liver phosphorylase b kinase activity, measured in Patient 1, was also normal. Other glycolytic enzymes in muscle were preserved in both.

Adult↗
PubMed1990

Neuromuscular transmission in the mdx mouse.

In both disorders, the muscle fiber plasma membrane is rendered selectively vulnerable by dystrophin deficiency. In both disorders there are also ultrastructural abnormalities involving the postsynaptic membrane of the neuromuscular junction. The object of this electrophysiologic study was to determine whether the observed ultrastructural abnormalities at the mdx neuromuscular junction are associated with an abnormality of neuromuscular transmission. In comparison with age-matched control mice, the mdx mice show an abnormal, age-dependent decrease of the amplitude of the miniature end-plate potential and a concomitant increase in the quantal content of the end-plate potential. Consequently, the safety margin of neuromuscular transmission is not impaired.

Animals↗
PubMed1990

Lysis of myotubes by alloreactive cytotoxic T cells and natural killer cells. Relevance to myoblast transplantation.

The aim of this study was to investigate the susceptibility of human myotubes to lysis by the two major types of cytotoxic effector cells, CD3+CD8+ cytotoxic T cells (CTL) and CD16+CD56+ natural killer (NK) cells. The myoblasts preparations used as target cells were greater than 90% pure as assessed by immunostaining with the Leu19 monoclonal antibody (MAb) that cross-reacts with the neural cell adhesion molecule N-CAM. Allospecific CTL lines were generated from mixed lymphocyte cultures, and freshly isolated allogeneic and autologous peripheral blood cells were used as a source of NK cells. The cytotoxicity was observed under phase optics and by immunoelectron microscopy, and was quantitated with a chromium release assay. Myotubes were efficiently killed by allospecific CTL and by autologous and allogeneic NK cells. The killing by CTL was inhibited with an anti-class I HLA MAb, and the killing by NK cells was inhibited by depleting peripheral blood cells of CD16+ cells with anti-CD16 MAb and complement. The results have important implications for myoblast transplantation, an experimental therapy of muscular dystrophy.

Cells, Cultured↗
PubMed1990

Electron transfer flavoprotein: ubiquinone oxidoreductase (ETF:QO) deficiency in an adult.

A 19-year-old woman with mild myopathic symptoms from age 6 and fasting intolerance presented with a Reye-like syndrome and a myopathy. Investigations disclosed a lipid storage myopathy, type II glutaric acidemia, and carnitine deficiency in skeletal muscle. Riboflavin and carnitine treatment corrected the metabolic abnormalities and she improved clinically. She later died from pulmonary complications secondary to aspiration. Subsequent studies established electron transfer flavoprotein: ubiquinone oxidoreductase (ETF:QO) deficiency (fibroblast ETF:QO activity was 2.9 mU/mg, normal range is 14.1 +/- 3.8 mU/mg) as the cause of her illness. This is the first documented case of ETF:QO diagnosed in an adult.

Acidosis↗
PubMed1990

Induction of HLA-DR expression on human myoblasts with interferon-gamma.

Myoblast transplantation is an experimental therapy that may be useful in hereditary muscle diseases. One obstacle to this approach is immune rejection. We evaluated human myoblasts and myotubes for surface expression of HLA class I and II histocompatibility antigens. The myoblast preparations, cultured from muscle biopsy specimens, were more than 95% pure as assessed by immunostaining with the Leu19 monoclonal antibody that reacts with human myoblasts and regenerating muscle fibers. Myoblasts and myotubes constitutively expressed HLA-class I but not HLA-class II molecules. However, HLA-class II expression was induced on mononucleated myoblasts after culture for 5 days in the presence of recombinant human interferon-gamma. The results indicate that transplanted myoblasts can be rejected because of histoincompatibility at the HLA-class I and HLA class II locus. Furthermore, an aberrant expression of HLA-class II antigen on myoblasts in vivo may play a role in the pathogenesis of autoimmune muscle disorders.

Autoimmune Diseases↗
PubMed1990

Immune effector mechanisms in inflammatory myopathies.

PM, IBM, and DM represent the commonly occurring inflammatory myopathies. In DM, the effector response appears to be predominantly humoral and directed against intramuscular blood vessels; a local humoral response may occur in muscle itself. Capillary lysis precedes other pathologic changes, suggesting that the capillary endothelium is an early and possibly primary target of the immune response. Questions remain about the role of immune complexes versus circulating antibodies, whether the muscle fiber injury can be explained by ischemia alone, and the possible role of endomysial CD8+ T cells. In PM and IBM, there is evidence for T-cell mediated cytotoxicity against the muscle fibers; however, muscle fiber destruction also could result from antibody-dependent complement-mediated lysis of the sarcolemma. Questions remain about the identity of the muscle fiber surface antigen(s) recognized by T cells and the molecular mechanisms of T-cell-mediated muscle fiber destruction.

Antigen-Antibody Complex↗
PubMed1989

Inclusion body myositis: the mumps virus hypothesis.

The resemblance of the filamentous inclusions in inclusion body myositis (IBM) to mumps virus nucleoproteins and the report of immunoreactivity of the inclusions for mumps virus antigens have implicated the mumps virus in the etiology of IBM. We tested the mumps virus hypothesis by in-situ hybridization with a cDNA probe specific for the mumps virus nucleocapsid gene, and immunocytochemically with antibodies against "soluble" and "viral" mumps antigens. The tests were performed on muscle specimens (IBM, 20; acid maltase deficiency, 4; chloroquine myopathy, 2; nonweak control subjects, 5) and mumps virus-infected and uninfected HEp-2 cells. The in-situ hybridization study showed a strong specific signal in the infected HEp-2 cells but no specific signal in IBM, other myopathies, or nonweak control subjects. The immunocytochemical study showed specific binding of the antimumps antibodies to the infected HEp-2 cells but demonstrated only nonspecific binding of these antibodies around rimmed vacuoles in IBM, acid maltase deficiency, and chloroquine myopathy. These studies cast doubt on the mumps hypothesis of IBM.

Biopsy↗
PubMed1989

Early ultrastructural alterations in adult dermatomyositis. Capillary abnormalities precede other structural changes in muscle.

In 6 adults with dermatomyositis, minimally weak or nonweak muscles that showed inconclusive light-microscopic alterations were examined by electron microscopy. In all 6 specimens, this revealed pathologic changes in endomysial capillaries. The endothelial cells harbored microtubular inclusions and microvacuoles in all cases; pale swollen endothelial cells were observed in 3 specimens. There were no significant ultrastructural changes in the muscle fibers. In all cases, a small proportion of muscle capillaries were immunoreactive for complement membrane attack complex neoantigens. The findings imply that in adult dermatomyositis capillary injury precedes muscle fiber damage and infiltration by inflammatory cells, and that the microvasculature is an early and specific target of the disease process in muscle.

Adult↗
PubMed1989

Major histocompatibility complex class I antigen expression, immunolocalization of interferon subtypes, and T cell-mediated cytotoxicity in myopathies.

Major histocompatibility complex class I (MHC-I) expression on target cells is a prerequisite for antigen-specific T cell-mediated cytotoxicity (TCMC). Enhanced MHC-I expression has been attributed to interferons (IFNs) released from inflammatory cells. In previous studies, we found evidence of TCMC (invasion of non-necrotic muscle fibers by cytotoxic T cells) in polymyositis (PM) and in inclusion body myositis (IBM). We occasionally found evidence of TCMC in Duchenne dystrophy (DD) but not in dermatomyositis (DM). This study examines the relationships between TCMC, MHC-I expression, and IFN immunoreactivity in these diseases and normal controls. In controls, reactivity for MHC-I was confined to blood vessels. In all diseases, regenerating fibers expressed MHC-I. In IBM, PM and DD, all nonnecrotic muscle fibers invaded by CD8+ cells and some adjacent fibers expressed MHC-I. In DM, myriad muscle fibers expressed MHC-I but none were invaded by CD8+ cells. In all diseases, only a few mononuclear cells and no muscle fiber surfaces were immunoreactive for IFNs. We conclude that MHC-I expression on muscle fibers is necessary but not sufficient for TCMC in myopathy; that the biological significance of increased MHC-I expression in DM remains undefined; and that currently available and appropriately controlled immunocytochemical methods show no relationship between increased MHC-I expression on muscle fibers and local IFN synthesis by mononuclear cells.

Alkaline Phosphatase↗
PubMed1989

Muscle coenzyme Q deficiency in familial mitochondrial encephalomyopathy.

The electron transport system of muscle mitochondria was examined in a familial syndrome of lactacidemia, mitochondrial myopathy, and encephalopathy. The propositus, a 14-year-old female, and her 12-year-old sister had suffered from progressive muscle weakness, abnormal fatigability, and central nervous system dysfunction since early childhood. In the propositus, the state 3 respiratory rate of muscle mitochondria with NADH-linked substrates and with succinate was markedly reduced. The levels of cytochromes a + a3, b, and c + c1 were normal. The activities of complexes I, II, III, and IV of the electron transport chain were normal or increased. By contrast, the activities of complex I-III and of complex II-III, both of which need coenzyme Q10 (CoQ10), were abnormally low. On direct measurement, the mitochondrial CoQ10 content was 3.7% of the mean value observed in 10 controls. Serum and cultured fibroblasts of the propositus had normal CoQ10 contents. In the younger sister, the respiratory activities and CoQ10 level of muscle mitochondria were similar to those observed in the propositus. The findings establish CoQ10 deficiency as a cause of a familial mitochondrial cytopathy and suggest that the disease results from a tissue-specific defect of CoQ10 biosynthesis.

Adolescent↗
PubMed1989

Inclusion body myositis. Observations in 40 patients.

Inclusion body myositis (IBM) was suspected on light microscopic grounds in 48 of 170 consecutive patients with inflammatory myopathies. One or more vacuoles containing membranous material, groups of atrophic fibres, and an autoaggressive endomysial inflammatory exudate occurred in 100, 96 and 92% of the muscle specimens. All three of these features were present in 88% of the specimens. Electron microscopy confirmed the presence of filamentous inclusions in 40 of 43 patients. The inclusions are typically near vacuoles and a minimum of three vacuolated fibres must be scrutinized to detect them with confidence. There is no electromyographic pattern that can reliably distinguish IBM from other inflammatory myopathies. The typical clinical features in the patients diagnosed by histological criteria as IBM were: insidious onset after age 50 yrs with painless, proximal lower extremity weakness; slow but relentless progression with selectively severe involvement of quadriceps, iliopsoas, tibialis anterior, biceps and triceps muscles; relatively early depression of the knee reflexes; and a normal or mildly elevated serum creatine kinase level. The male: female ratio was 3:1. Distal weakness occurred in about 50%, but only in 35% was it as great or greater than proximal weakness. Significant associated illnesses include other autoimmune disorders (15%), diabetes mellitus (20%), and diffuse peripheral neuropathy (18%). Prednisone treatment at dose levels frequently effective in polymyositis failed to prevent disease progression in those patients observed for 2 or more years. Our findings support the notion that IBM is a distinct entity in which a set of pathological features is associated with a constellation of clinical findings.

Adult↗
PubMed1988

Monoclonal antibody analysis of mononuclear cells in myopathies. IV: Cell-mediated cytotoxicity and muscle fiber necrosis.

Cell-mediated muscle fiber injury occurs in inclusion body myositis (IBM), polymyositis (PM), and even in Duchenne dystrophy (DD). Most of the autoaggressive cells are T cells and macrophages, but some are killer/natural killer (K/NK) cells. We here compare the frequencies per 1,000 muscle fibers of endomysial K/NK cells of varying cytotoxicity with those of T cells and macrophages in 8 cases each of IBM, PM, and DD. Two-micrometer serial cryostat sections were analyzed. The Leu-4 marker, present on all T cells and some K/NK cells, and the Leu-7 and Leu-11 markers, present on K/NK cells, were localized by paired immunofluorescence. Macrophages were demonstrated by the acid phosphatase reaction. In IBM, PM and DD, the respective average cell counts per 1,000 muscle fibers were: Leu-4+7- cells (T cells not expressing a K/NK marker)--710, 530, and 59; Leu-4+7+ cells (K/NK cells of low K/NK cytotoxicity)--294, 163, and 13; Leu-4-7+ cells (K/NK cells of intermediate cytotoxicity)--32, 10, and 2; and macrophages--292, 251, and 38. Leu-11+ K/NK cells that have the highest killing activity were virtually absent in all cases. The data suggest a limited role for antigen and major histocompatibility complex unrestricted K/NK cells, as compared with antigen-specific and major histocompatibility complex-restricted T cells, in IBM and PM. Further, the findings cast doubt on the significance of either T cells or K/NK cells in mature muscle in DD.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1988

Monoclonal antibody analysis of mononuclear cells in myopathies. V: Identification and quantitation of T8+ cytotoxic and T8+ suppressor cells.

In polymyositis (PM) and inclusion body myositis (IBM), but not in dermatomyositis there is evidence of cell-mediated cytotoxicity: T8+ cells accompanied by macrophages focally surround, invade, and destroy nonnecrotic muscle fibers. However, the T8 marker appears on both cytotoxic (Tc) and suppressor (Ts) cells. The Leu-15 marker appears on Ts but not on Tc cells, but it also appears on macrophages and on some killer/natural killer cells. To obviate this problem, the T8, Leu-15, and Leu-7 markers were demonstrated by sequential paired immunofluorescence in single cryostat sections. Using this approach, we reliably differentiated for the first time between Tc and Ts cells in tissue sections. Six cell phenotypes were identified: T8+ Leu-15-Leu7- Tc cells, T8+ Leu-15+ Leu-7- Ts cells, three types of Leu-7+ killer/natural killer cells, and T8-Leu-15+ Leu-7- macrophages. Muscle specimens from 5 patients with PM and 5 with IBM were studied. In each case, 6 nonnecrotic muscle fibers focally surrounded and invaded by mononuclear cells were selected randomly. A total of 2,022 mononuclear cells were analyzed, 870 from patients with PM and 1,152 from those with IBM. When counts of the identified cell phenotypes in individual patients were pooled, there were four times as many T8+ Leu-15- Leu-7- Tc cells as T8+ Leu-15+ Leu-7- Ts cells in either PM or IBM samples. However, when the relative frequencies of the Tc and Ts cells were examined in individual patients, the Tc cells tended to become more abundant, and the Ts cells correspondingly less abundant, with the duration of symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗