Electron microscope radioautography as a quantitative tool in enzyme cytochemistry. II. The distribution of DFP-reactive sties at motor endplates of a vertebrate twitch muscle.
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-(3)H. Most of the sensitive sites were located in the subneural apparatus at a concentration of 90,000 sites per micro(3) of cleft tissue or 12,000 sites per micro(2) 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.
D000110:Acetylcholinesterase / Q000032:analysis*; D000818:Animals; D001345:Autoradiography; D001369:Axons / Q000201:enzymology; D001665:Binding Sites; D006651:Histocytochemistry; D007531:Isoflurophate; D008407:Mast Cells / Q000201:enzymology; D008566:Membranes / Q000201:enzymology; D008722:Methods; D051379:Mice; D008854:Microscopy, Electron; D009132:Muscles / Q000201:enzymology; D009469:Neuromuscular Junction / Q000166:cytology / Q000201:enzymology*; D014316:Tritium
D014316:Tritium; D007531:Isoflurophate; D000110:Acetylcholinesterase