Deoxyribonucleic acid content of cell nuclei in the neural tube of the chick embryo: Evidence for intermitotic migration of nuclei

Abstract

This work aimed to test F. C. Sauer's migration concept as the explanation for the familiar appearance of mitotic figures confined to the margin of the lumen in the early neural tube. If the nuclei actually do migrate between divisions from lumen to periphery, then back (through the early prophase nucleus deep in the wall) to the mitotic figures at the lumen, nuclei with increased DNA (early prophases) should occur deep in the wall. The amount of DNA in various nuclei in the neural tube of a three day chick embryo was measured in Feulgen-stained sections by the two wave length method of microspectrophotometry. In the outer two-thirds of the wall the larger nuclei contained the larger amounts of DNA. Nuclei in this location gave a mean DNA value approximately halfway between the previously established 2 n and 4 n values. The difference between this intermediate value and the mean 2 n DNA value, determined from half telophases at the lumen, is statistically significant at the 0.1 per cent level. The increased DNA in nuclei deep in the wall indicates that the doubling of DNA that precedes cell division takes place in the depth of the wall at some distance from the central canal. The data confirm the concept of intermitotic migration of embryonic epithelial nuclei.