Cytokinetics of secondary neurulation in chick embryos: Hamburger and Hamilton stages 16-45

Abstract

OBJECTIVES: In an attempt to understand the events in the secondary neurulation in embryonic stage, we investigated cytokinetic changes in the tail bud of normal developing chick embryos. MATERIALS AND METHODS: We investigated chick embryos of Hamburger and Hamilton stages 16-45 by staining for proliferating cell nuclear antigen (PCNA) and applying the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) method. RESULTS AND CONCLUSIONS: The cytokinetics of secondary neurulation have several distinctive properties: a general chronological delay compared to primary neurulation; absence of ventrodorsal differences; larger rostrocaudal differences; and degeneration of the distal end of the spinal cord in the later stages of development. These differences in morphogenetic and cytokinetic behavior between primary and secondary neurulation may help to improve our understanding of anomalies originating during secondary neurulation.