ACHE ACTIVITY IN THE SPINAL GANGLIA OF THE CHICK EMBRYO DURING DEVELOPMENT

Abstract

The Koelle reaction for AChE in the spinal ganglia of the chick embryo is weakly positive beginning at the 4th incubation day; here it occurs later than in the motor area of the spinal cord and the myotomes, where it appears intense about the 60th hour and the 72nd hour of incubation respectively. In the following days a rise in intensity takes place in the ganglia, earlier in the cranial than in the more caudal ones. Two groups of cells may be precociously identified by the Cajal-De Castro method within the ganglion, according to their different developmental degree and location. The AChE appearance first occurs in the large type cells located in the lateral portion of the ganglion, then in the dorso-medially located group of small cells: it is strictly correlated, chronologically at least, with the neurofibrillary differentiation. In the last days of incubation and after hatching, the segregation of the 2 cell groups is less evident. In both the antero-lateral and dorso-medial groups some cells grow quite conspicuous while others remain small, so that a homogeneous distribution is reached. As regards the Koelle reaction, some cells appear intensely positive, while others are more or less weakly so; no relationship occurs between the intensity degree of the reaction and either the cell volume or location. Beyond doubt AChE activity appears at an early stage in the ganglion and increases in intensity in association with the maturation of the cell. The significance of the final enzyme distribution occurring in cells of any volume and location, in the adult, is still far from clear.