Hai Won Chang

Monoclonal IgM with unique specificity to gangliosides GM1 and GD1b and to lacto‐N ‐tetraose associated with human motor neuron disease

IgM lambda monoclonal antibodies in two patients with motor neuron disease showed the same unique antigenic specificity. They bound to gangliosides GM1 and GD1b and to lacto-N-tetraose-BSA. By immunofluorescence microscopy they bound to central and peripheral nerve tissue and to motor end-plates at the neuromuscular junction. Sera from control subjects did not contain antibodies of similar specificity. Monoclonal IgMs with the same unique specificity could be responsible for motor neuron disease in some patients with monoclonal gammopathies.

Penicillamine‐induced myasthenia gravis: Effects of penicillamine on acetylcholine receptor

Autoimmune diseases, including myasthenia gravis, occur in patients treated with D-penicillamine. Because D-penicillamine might induce autoantibodies by the mechanism of antigenic alteration, we studied the reaction of D-penicillamine with purified acetylcholine receptor from Torpedo californica. We found that brief exposure to D-penicillamine resulted in its covalent attachment to two receptor subunits, alpha (40,000 daltons) and gamma (59,000 Daltons), presumably by reduction and formation of mixed disulfides. Furthermore, D-penicillamine treatment resulted in a dramatic modification of the equilibrium acetylcholine binding properties of both purified receptor and receptor-rich membrane fragments.

Partial dystrophin deficiency in monozygous twin carriers of the Duchenne gene discordant for clinical myopathy

We studied monozygous twin women, age 63. One, asymptomatic, had a serum creatine kinase (CK) level of 191 units (normal, 1 to 50); her son died of typical Duchenne muscular dystrophy (DMD) at age 18. Her twin sister had symptomatic limb weakness from about age 40. Her serum CK was 495 units. EMG and muscle biopsy were compatible with myopathy. In the asymptomatic twin, the peripheral blood lymphocyte karyotype was 46,XX. In the affected twin, 18% of cells were 45,X, and the others 46,XX, without X/autosome translocation. DNA analysis did not reveal a deletion at the DMD locus. Immunologic studies of dystrophin showed a partial deficiency of the protein that was more severe in the symptomatic twin. The clinical discordance and the different severity of dystrophin deficiency may have resulted from the effects of lyonization.

Dystrophinopathy in two young boys with exercise-induced cramps and myoglobinuria

Two young boys were referred for evaluation of metabolic myopathy because of elevated serum levels of creatine kinase, cramps and pigmenturia. Immunohistochemical studies of dystrophin in muscle biopsies showed reduced intensity of the stain with a patchy and discontinous pattern in most fibers. In both patients dystrophin was undetectable by immunoblotting. DNA analysis of the dystrophin gene was not informative in one patient; in the other it revealed an in-frame deletion comprising exons 3–6. These observations suggest that the two patients are affected with an unusual phenotype of Becker muscular dystrophy. Dystrophin analysis should be included in the evaluation of patients with childhood-onset of recurrent myoglobinuria.

Dystrophin deficiency in young girls with sporadic myopathy and normal karyotype

We studied dystrophin in three young girls with a sporadic myopathy of early onset, manifested by mild to severe limb weakness, calf hypertrophy, high serum creatine kinase, normal karyotype, and morphologic features in muscle consistent with muscular dystrophy. DNA analysis did not reveal a deletion of the dystrophin gene. Immunohistochemical studies of dystrophin in muscle biopsies showed a mosaic of fibers with and without dystrophin, and immunoblot analysis showed partial dystrophin deficiency in all three patients, more severe in the patient with the highest proportion of dystrophin-deficient fibers. These observations suggest that the patients are Duchenne muscular dystrophy carriers. The data also support the concept that uneven lyonization in muscle is responsible for the clinical myopathy in these patients. We suggest that any girl with sporadic proximal limb weakness should be evaluated as a possible Duchenne carrier by dystrophin studies.

Spectrophotometric determination of reaction stoichiometry and equilibrium constants of metallochromic indicators: III. Antipyrylazo III complexing with Ca2+ and acetylcholine receptor protein

Stoichiometries, equilibrium constants and optical extinction coefficients of calcium-antipyrylazo III (An) complexing are determined with the analytical method described in article I of this series. Spectrophotometric Ca titrations of An at the wavelengths 595 and 710 nm indicate overall dissociation equilibrium constants for the complexes CaAn, CaAn2 and Ca2An to be 4.5 x 10(-4) M, 1.1 x 10(-8) M2 and 1.5 x 10(-6) M2, respectively, extrapolated to zero ionic strength. Ca titrations of solutions containing An plus acetylcholine receptor protein give clear evidence that An binds to the protein to a large extent in the presence of Ca2+; furthermore, addition of acetylcholine results in release of protein-bound Ca and An. This is the first reported indication that antipyrylazo III binds to biological material and questions the usefulness of this dye as a Ca indicator in biological systems.

Electrophysiological studies of thymectomized and nonthymectomized acetylcholine receptor-immunized animal models of myasthenia gravis

Abstract White New Zealand rabbits were immunized with acetylcholine receptor (AChR) purified from the electric organs of either the Electrophorous electricus (eel) or Torpedo californica (torpedo). Approximately 4 days after a second injection of 100 μg AChR in complete Freunds adjuvant, the immunized animals developed weakness of the peripheral muscles which was aggravated by repetitive activity and was partially alleviated by anticholinesterases such as edrophonium or pyridostigmine. Electromyograms taken from the anterior tibialis muscle demonstrated a decrement of the compound action potentials at a stimulation frequency of 5 Hz which was reversed by the intravenous administration of 1 mg pyridostigmine. If the animals were not treated with anticholinesterases they died within a couple of days. Biopsies of the intercostal muscle were done under Nembutal anesthesia, and intracellular recordings revealed subliminal end-plate potentials (EPPs) and miniature end-plate potentials (MEPPs) of greatly diminished amplitudes. At some neuromuscular junctions no MEPPs were detected, and in other junctions MEPPs were seen but no EPP was evoked upon nerve stimulation. Muscles from two immunized rabbits showed spontaneous muscle action potentials occurring at 1 to 2 Hz. Serum from the rabbits immunized with torpedo or eel AChR, when applied to in vitro preparations of the eel electroplaque or frog cutaneous pectoris muscle, caused a decrease in postjunctional membrane sensitivity to carbamylcholine and reduced the MEPP and EPP amplitudes even after heat inactivation of the serum complement (56°C for 30 min). In addition to a decrease in chemosensitivity, an enhancement of receptor desensitization occurred in the neuromuscular junctions of serum-treated frog muscles. Thymectomies on adult rabbits prior to the immunization had the effect of delaying the onset of myasthenia in two of six rabbits, and in three of six rabbits only mild myasthenia occurred. The blood antibody titers to AChR were similar in both the thymectomized and nonthymectomized rabbits.