A new myasthenic syndrome with end-plate acetylcholinesterase deficiency, small nerve terminals, and reduced acetylcholine release.

Andrew G Engel, E. H. Lambert, M. R. Gomez

Research output: Contribution to journalArticle

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Abstract

A new myasthenic syndrome is described in a patient whose symptoms began soon after birth and included generalized weakness increased by exertion, easy fatigability, hyporeflexia, and refractoriness to anticholinesterase drugs. Electromyography showed a decremental response at all frequencies of stimulation and a repetitive response to single nerve stimulation. Miniature end-plate potentials (mepps) were of normal amplitude but of decreased frequency. The mepp duration and half-decay time were prolonged, and prostigmine was without any addtitional effect. The quantum content of the end-plate potential was decreased due to a reduced store of quanta immediately available for release, but the probability of release was normal. Quantitative electron microscopy demonstrated a 3-fold to 4-fold decrease of nerve terminal size and reduced postsynaptic membrane density. The postsynaptic folds showed focal degeneration, and many were distended by labyrinthine membranous networks that communicated with the synaptic space. Degenerating nuclei were found in the junctional sarcoplasm. The ultrastructural localization of the acetylcholine receptor protein was normal. Acetylcholinesterase (AChE) was absent from the motor end-plates by histochemical and electron cytochemical criteria. Biochemical studies indicated total absence of the end-plate-specific 16 S species of AChE and marked decrease in total muscle AChE. A congenital defect in the molecular assembly of AChE or in its attachment to the postsynaptic membrane might represent the basic abnormality and condition the morphological and physiological alterations.

Original languageEnglish (US)
Pages (from-to)315-330
Number of pages16
JournalAnnals of Neurology
Volume1
Issue number4
StatePublished - Apr 1977

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Muscle Weakness
Acetylcholinesterase
Acetylcholine
Miniature Postsynaptic Potentials
Motor Endplate
Post-Synaptic Density
Neostigmine
Abnormal Reflexes
Membranes
Excitatory Postsynaptic Potentials
Cholinesterase Inhibitors
Electromyography
Cholinergic Receptors
Electron Microscopy
Parturition
Electrons
Muscles
Proteins

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

A new myasthenic syndrome with end-plate acetylcholinesterase deficiency, small nerve terminals, and reduced acetylcholine release. / Engel, Andrew G; Lambert, E. H.; Gomez, M. R.

In: Annals of Neurology, Vol. 1, No. 4, 04.1977, p. 315-330.

Research output: Contribution to journalArticle

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