Cholinesterase in normal and abnormal human skeletal muscle.

The original theory of neurqmuscular transmission involving acetylcholine led to the necessity to postulate an enzyme which hydrolysed it. This was done by Dale in 1914. It was not until 1932, however, that Stedman, Stedman, and Easson were able to prepare from horse serum an enzyme which could actually do this and which was called cholinesterase. The enzyme was then found to be present in a wide variety of tissues and in muscle it was observed that more cholinesterase was present at the motor points than in other parts of the tissue (Marnay and Nachmansohn, 1937; Feng and Ting, 1938). Couteaux and Nachmansohn (1938, 1940) showed that after denervation a certain amount of cholinesterase remained in muscle homogenates, a finding which suggested that some part of the cholinesterase was located in the muscle itself and that the enzyme was not restricted entirely to the nervous elements in this tissue. The precise region of localization of the enzyme had to await the development of a suitable histochemical technique. Such a technique was first described by Koelle and Friedenwald (1949). It was subsequently modified by Koelle (1951) to eliminate diffusion artefacts, and by Couteaux and Taxi (1952), Coers (1953b), Gerebtzoff (1953), Gomori (1952), and others. Some of these latter authors introduced formalin fixation and the use of buffers at a lower pH. With these technical aids it became possible not only to study the finer distribution of cholinesterase in the motor end-plate subneural apparatus but also to study the morphology of the apparatus. The motor end-plate was first described by Doy&ere in 1840 and was so named by Ktihne (1886). Subsequent studies were made on it largely with the aid of silver and gold techniques by Tello (1917), Cuajunco (1942), Couteaux (1938, 1941), and Coers (1955) among others. The author who contributed most to the study of the morphology of the subneural apparatus was Couteaux (1947) who, using stains such as dahlia violet and Janus green, demonstrated that this part of the end-plate was made up FIG. 1.-" Classical " motor end-plates (as described by Koelle) in rat muscle. Technique used to demonstrate cholinesterase employed before formalin fixation, so that a clear morphological picture was obtained.