Acetylcholine receptors and cholinesterase in developing chick skeletal muscle fibers.
The developmental changes in the distribution of acetylcholine receptors (AChRs) and cholinesterase (ChE) were investigated in the posterior latissimus dorsi (PLD) muscle of chick embryos by double staining with rhodamine-labeled erabutoxin b (TMR-Eb) for AChRs and Karnovsky's method for ChE. During the development, the TMR-Eb and ChE positive areas changed in their shapes and sizes. In early stages, the TMR-Eb positive areas appeared as fine fluorescent dots of about 0.3 micrometer in diameter or small aggregates of such dots. These areas then became enlarged and exhibited the following sequential changes in their configuration: spindle-, round-, ring-, C- and finally tree-shaped. The transformation in the configuration of the areas appeared to be caused by the changes of the fluorescent dots in their number and distribution. Simultaneous staining with ChE revealed that at early stages the TMR-Eb positive areas were not stained with ChE, but then they were stained later. The ChE deposits usually accumulated at the borders of the TMR-Eb positive areas and thereby outlined them. Electron microscopy using horseradish peroxidase-labeled erabutoxin b revealed that the fluorescent dots represent the discrete regions of high AChR concentration at the muscle membrane.
D000818:Animals; D002642:Chick Embryo; D002802:Cholinesterases / Q000378:metabolism*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009132:Muscles / Q000196:embryology* / Q000201:enzymology / Q000648:ultrastructure; D011950:Receptors, Cholinergic / Q000378:metabolism*
D011950:Receptors, Cholinergic; D002802:Cholinesterases