Abstract
Using new methods which perform 3H-thymidine autoradiography and AChE histochemistry on the same sections, the interrelationship among loss of proliferating ability, morphological development and increase of AChE activity during the course of differentiation of the neural tube cells were investigated in early chick embryos. The neural tube wall consisted of four kinds of cells: (1) AChE negative spindle shaped cells, (2) weakly positive spindle shaped cells showing AChE activity in the cisternae of the nuclear envelope and in a few short profiles of r-ER, (3) moderately positive spindle shaped cells showing AChE activity in the cisternae of the nuclear envelope and in a moderate number of r-ER profiles and (4) intensely positive large round cells showing AChE activity in the cisternae of the nuclear envelope and in a large number of r-ER profiles. Nuclei of the former three kinds of cells slet located in the ependymal layer, while the AChE intensely positive cells were in the mantle layer. The AChE negative and weakly positive cells were capable of proliferation and were regarded as undifferentiated neuroepithelial cells. The AChE moderately positive and intensely positive cells were, in contrast, no longer capable of proliferation and were regarded as neurons, especially the former as newly formed neurons. These findings indicate that the r-ER increases rapidly in number and in volume in newly formed neurons, soon after their final cell division, and that AChE activity increases in the neurons parallel to the development of the r-ER.
