Experimental production of perfect cyclopia by removal of the telencephalon and reversal of bilateralization in somite‐stage chicks

Publisher Website
Google Scholar
Abstract
The telencephalon was removed with iridectomy scissors in stages from 1 to 20 somites, with the vast majority of operated chicks being at 5 to 10 somites. The most chance of successfully producing cyclopia appears to be at 6 to 7 somites. Twelve cyclopean embryos, with operated stages ranging from 5 to 10 somites, were produced among the first 271 operations. Subsequently, 398 operations, concentrated on 9‐ to 10‐somite embryos, proved that cyclopia is very much less apt to follow this sort of operation at these stages than at the very slightly younger stages.Serial sections of the cyclopean embryos were stained with a modification of the Bodian protargol stain. An oral hypophysis is usually present in these embryos, making them in this respect similar to the majority of cyclopean embryos for which this point is reported in the literature, but making them different from experimentally produced cyclopean amphibian embryos reported in the literature. The sequence of fusion of extrinsic ocular muscle components and the patterns of their nerves, as the cyclopean defect becomes more severe, indicates that the reversal of bilateralization is a ventralization.Coupled with biochemical work on the chick and the more recent of the biochemical work of others on amphibia, the results allow one to suggest that experimental stimuli resulting in the cyclopean mode of development may act either on prechordal substrate or on neural tissue of telencephalon and diencephalon, or on both substrate and neural tissue, and that they may be effective over a considerable period of time, up to and including the period of actual bilateralization of the optic primordia.

This publication has 35 references indexed in Scilit: