The distribution of diisopropylfluorophosphate (DFP)-sensitive enzyme sites at the neuromuscular junction was determined quantitatively by electron microscope radioautography after incubation of muscle fragments in DFP-3H. Most of the sensitive sites were located in the subneural apparatus at a concentration of 90,000 sites per µ3 of cleft tissue or 12,000 sites per µ2 of postjunctional membrane surface area. A considerable concentration is also present in the teloglial cap. It has previously been demonstrated (Rogers et al., 1966) that one-third of the DFP-sensitive sites at the endplate can be reactivated by pyridine-2-aldoxime methiodide (2-PAM)—a compound which selectively reactivates phosphorylated acetylcholinesterase. In the present study, it was found that this ratio of 1:2 holds also on a fine-structural level. Muscle mast cells were found to have a heavy concentration of bound DFP.
ELECTRON MICROSCOPE RADIOAUTOGRAPHY AS A QUANTITATIVE TOOL IN ENZYME CYTOCHEMISTRY : II. The Distribution of DFP-Reactive Sites at Motor Endplates of A Vertebrate Twitch Muscle
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M. M. Salpeter; ELECTRON MICROSCOPE RADIOAUTOGRAPHY AS A QUANTITATIVE TOOL IN ENZYME CYTOCHEMISTRY : II. The Distribution of DFP-Reactive Sites at Motor Endplates of A Vertebrate Twitch Muscle . J Cell Biol 1 July 1969; 42 (1): 122–134. doi: https://doi.org/10.1083/jcb.42.1.122
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