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Biomedical subjects

S H Appel

Publications and source records attributed to S H Appel.

At least 199 records · Page 11Linked to original sources
PubMed1976

Cholinergic sites in skeletal muscle. II. Interaction of an agonist and two antagonists with the acetylcholine site.

The equilibrium interactions of alpha-bungarotoxin, d-tubocurarine, and carbamylcholine with junctional and extrajunctional skeletal muscle acetylcholine receptors were examined. d-Tubocurarine is a competitive inhibitor of the bindings of alpha-bungarotoxin to the acetylcholine receptor. No substantive difference was observed in the association of d-tubocurarine with the junctional and extrajunctional receptors. In contrast, the carbamylcholine inhibition of toxin binding is not competitive. The data indicate that either the single set of alpha-bungarotoxin and d-tubocurarine bindings sites contains two subsets of carbamylcholine sites or that the carbamylcholine binds in a cooperative manner to a single set of sites. In addition, the affinity of carbamylcholine for extrajunctional receptors may be higher than the affinity for junctional receptors.

Acetylcholine↗
PubMed1976

Carrier detection in Duchenne muscular dystrophy.

We measured endogenous phosphorylation of peak II (apparent molecular weight of 220,000 daltons) of the erythrocyte membrane in 21 mothers of patients with Duchenne muscular dystrophy. The mean values of mothers with affected sons were significantly increased over those of matched controls (77.0 and 55.8 pmoles per milligram of 15-minute incubation; P less than 0.01). Detailed testing of mothers of affected sons revealed proximal muscle weakness. Seven mothers of isolated patients who had normal levels of creatine phosphokinase and no daughters with elevated levels were identified as carriers, because their mean value of peak II phosphorylation was increased (75.9 pmoles per milligram per 15 minutes) and equivalent to the level demonstrated in the 14 acknowledged carriers. Our results suggest that cases of Duchenne muscular dystrophy previously considered to be new mutations are much less common than estimated.

Adenosine Triphosphate↗
PubMed1976

Scanning electron microscopy studies in muscular dystrophy.

Scanning electron microscopy of unmanipulated erythrocytes from patients with myotonic dystrophy or Duchenne dystrophy and patients who were Duchenne carriers showed a large increase in the number of stomatocytes over the number in normal controls. No specific morhologic changes that would differentiate any of the dystrophic patients from one another were seen. Adverse conditions such as washing before fixation or extreme pH produced a greater change in erythrocytes from these patients than in those from normal controls.

Cell Count↗
PubMed1976

Erythrocyte spectrin peak II phosphorylation in Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a rapidly progressive crippling disease of young boys that is inherited as an X-linked recessive trait. Previous studies have demonstrated the usefulness of erythrocyte studies in exploring membrane abnormalities in inheritied muscular dystrophy. Erythrocyte spectrin peak II protein (m.w. equivalent to 220,000) was more highly phosphorylated under initial rate conditions in DMD than in controls. The extent of peak II phosphorylation was greater in DMD erythrocytes and a Na+ stimulated peak II phosphorylation effect (Avruch and Fairbanks 1974) was not found to account for the differences between DMD and controls. The phosphorylated state of spectrin proteins in the membrane was evaluated and no differences in DMD could be measured. The maximal transfer of phosphate from differences in DMD could be measured. The maximal transfer of phosphate from [gamma-32P]ATP to spectrin peak II accounts for approximately 5-10% of the total phosphate content of spectrin.

Adenosine Triphosphate↗
PubMed1976

Increased phosphorylated components of erythrocyte membrane spectrin band II with reference to Duchenne muscular dystrophy.

Increased erythrocyte band II phosphorylation has been demonstrated in patients with Duchenne muscular dystrophy (DMD). Band II has been purified by preparative sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Isoelectric focusing of purified band II from which SDS has been removed reveals heterogeneity. Band II migrates as multiple bands on isoelectric focusing gels and as a single band on SDS-polyacrylamide gels. The increased phosphorylation in DMD does not occur uniformly in all components of band II. Highly phosphorylated components of band II are present in DMD in which only minimal phosphorylation occurs in controls. These results suggest the presence of an abnormal band II substrate in erythrocyte membranes from DMD patients.

Adult↗
PubMed1975

Interaction of myasthenic serum globulin with the acetylcholine receptor.

A serum factor from patients with myasthenia gravis which inhibited the binding of 125I-labeled alpha-bungarotoxin to acetylcholine receptor extracted with Triton X-100 from rat muscle has been studied in detail. The inhibitory activity was localized to the IgG fraction based upon the fractionations by sodium sulfate precipitation and DEAE chromatography as well as reaction with anti-IgG globulin. The myasthenic globulin inhibited toxin binding to receptors extracted from degenerated muscle but did not inhibit toxin binding to normal junctional receptors. At saturation levels of myasthenic globulin, the number of denervated acetylcholine receptors available for toxin binding was reduced approx. 50 percent. The myastehnic globulin was found to bind to denervated acetylcholine receptors but not to normal acetylcholine receptors by a radioimmunoassay technique in which myasthenic globulin incubated with 125I-labeled alpha bungarotoxin-receptor complexes was precipitated by anti-IgG serum. The globulin binding was saturable over the same range as inhibition of toxin binding. The data suggest that the myasthenic IgC binds to a site on the receptor complex juxtaposed to the acetylcholine receptor site. The myasthenic globulin appears to be a useful probe for investigation differences between acetylcholine receptors extracted from normal and denervated muscle and for investigating the pathogenesis of myasthenia gravis.

Acetylcholine↗
PubMed1975

Macromolecular characterization of muscle membranes. Endogenous membrane kinase and phosphorylated protein substrate from normal and denervated muscle.

Light density membranes derived from the "microsomal" fraction of rat skeletal muscle contained an endogenous protein kinase which catalyzed the phosphorylation of an endogenous membrane substrate. No other membrane fraction contained any significant protein kinase activity. The optimal specific activity of the enzyme in these membranes was 350 pmol/mg/min. The endogenous muscle membrane protein kinase required magnesium, was stimulated by micromolar concentrations of calcium, had a pH optimum between 7.0 and 7.5, and demonstrated a K-m for ATP of 2.6 times 10 minus 5 M. The enzyme was markedly heat labile and demonstrated a linear Arrhenius plot with an apparent energy of activation of 12,100 cal/mol. There was no stimulation by cyclic nucleotides; and neither monovalent cations nor various neurotransmitters exerted any effect. It is presently unclear where the membranes exhibiting protein phosphorylation are localized within the muscle fiber. Enzyme markers suggest that these membranes are not derived from sarcolemma or sarcoplasmic reticulum but may originate in transverse tubules. The membrane phosphorylation was largely confined to a polypeptide with an apparent molecular weight of 28,000. Phosphorylation could also be detected in a lower molecular weight substrate as well as two polypeptides with apparent molecular weights of 95,000 and 56,000. The M-r-28,000 endogenous protein kinase substrate was isolated by preparative gel electrophoresis in sodium dodecyl sulfate. High voltage electrophoresis of a partial acid hydrolysate of the phosphorylated M-r-28,000 substrate identified the phosphate bond to be that of phosphoserine. The amino acid composition of the substrate was neither strongly acidic nor basic. It had a high content of glycine, glutamic acid, serine, and lysine. Hydrophobic residues constituted only 45% of the total composition. Following muscle denervation for 10 days, there was a significant decrease in the amount of the M-r-28,000 polypeptide as well as the extent of phosphorylation.

Animals↗
PubMed1975

Phenytoin and membrane fluidity in myotonic dystrophy.

Electron spin resonance spectroscopy was used to substantiate the presence of a membrane defect in myotonic erythrocytes. There was increased membrane fluidity and decreased polarity in myotonic membranes. Phenytoin (formerly diphenylhydantoin) "normalizes" fluidity differences in spectra derived from myotonic erythrocytes but has no significant effect on normal spectra. These experiments demonstrate the applicability of biophysical methods to human erythrocyte membranes and support the concept of a membrane defect in myotonic dystrophy that does not have a primary myopathic, neuropathic, or vascular cause.

Cell Membrane↗
PubMed1975

Phosphorylation of component a of the human erythrocyte membrane in myotonic muscular dystrophy.

Endogenous membrane protein kinase activity in fresh erythrocyte ghosts is altered in myotonic muscular dystrophy. Phosphorylation of erythrocyte Component a, which migrates with an apparent molecular weight of 90,000 to 100,000, is significantly reduced compared to age- and sex-matched controls. The difference in endogenous membrane protein kinase activity in fresh RBC membranes lends confirmation to the suggestion that myotonic dystrophy is a disease of widespread membrane alterations.

Adenosine Triphosphatases↗