The cytological localization of intracellular neuronal acetylcholinesterase

Sections of cat ciliary ganglia were stained for acetylcholinesterase activity by several modifications of the acetylthiocholine method in order to achieve optimal accuracy of cytological localization of the enzyme. These were compared by ordinary light and phase contrast microscopy with similar sections stained by standard techniques for Nissl substance, the Golgi apparatus, and the neurofibrillae, and by intravital methylene blue. The pattern of cytoplasmic distribution of acetylcholinesterase corresponded most closely with that of the Nissl substance. Following total inactivation of the ganglionic acetylcholinesterase by intravenously administered di-isopropyl fluorophosphate, the reappearance of the enzyme in vivo occurred at the same cytoplasmic sites prior to its reappearance at the cell membrane or preganglionic axonal terminations. These observations, and reports cited from the literature, provide support for the hypothesis that acetylcholinesterase is synthesized within the endoplasmic reticulum, then transported via its canaliculi to the surface of the cell and its processes, where its functional sites are oriented externally to the lipoidal membrane.

The characterization and localization of frog skin cholinesterase

Frog skin cholinesterase is largely of the serum (pseudocholinesterase) type. For whole skin, the activity at 10(-1) AcChCl is 4.9 microl./mg. N/hr. Tela subcutanea isolated by dissection exhibits an activity of 65 microl./mg. N/hr. at 10(-1) AcChCl. Since about one-tenth of the nitrogen of the skin is located in the tela subcutanea, it is estimated that more than 90 per cent of the enzyme is associated with this tissue layer.

Hydrolysis of neostigmine by plasma cholinesterase

Incubation of neostigmine with normal human plasma in vitro results in the formation of two quaternary nitrogen compounds, one of which has been identified as m-hydroxyphenyltrimethylammonium. This hydrolysis is prevented by prior addition of dyflos to plasma in concentrations sufficient to inhibit plasma cholinesterase activity. The significance of these findings is discussed in relation to the occurrence of the same metabolic products in the urine of patients with myasthenia gravis treated with oral neostigmine. No equivalent findings are available for normal subjects since it was not considered justifiable to treat them with neostigmine.