Neural differentiation of caudal cell mass (secondary neurulation) in chick embryos: Hamburger and Hamilton Stages 16-45.
In an attempt to understand the events in the secondary neurulation in embryonic stage, we investigated morphological changes in the tail bud of normal developing chick embryos. Hamburger and Hamilton stage 16-45 embryos were harvested and processed for light microscopic studies. The secondary neural tube is formed by aggregation of the caudal cell mass. Cells are arranged into a cord-like mass (medullary cord), which is continuous with the primary neural tube. Multiple small cavities develop in the medullary cord, and these cavities coalesce into one single lumen. The process of coalescence is completed by stage 35, and the whole neural tube is transformed into one tube with a single continuous lumen. At this stage, the terminal portion of the neural tube is bulged dorsally. Thereafter, the caudal portion of the neural tube regresses, and the proximal portion develops into normal spinal cord. Transient occlusion of the central canal was observed at stage 40 in one sample. The sequence of events elucidated in this study can be used as base-line data for experiments concerning congenital malformations involving secondary neurulation.
Yang
Hee-Jin
HJ
Division of Pediatric Neurosurgery, Seoul National University Children's Hospital, 28 Yongon-dong, Chongno-gu, Seoul 110-744, South Korea.
Wang
Kyu-Chang
KC
Chi
Je G
JG
Lee
Myung-Sook
MS
Lee
Yun-Jin
YJ
Kim
Seung-Ki
SK
Cho
Byung-Kyu
BK
D000818:Animals; D002454:Cell Differentiation; D002490:Central Nervous System / Q000166:cytology / Q000196:embryology*; D002642:Chick Embryo; D005314:Embryonic and Fetal Development; D009672:Notochord / Q000166:cytology / Q000196:embryology; D013623:Tail / Q000166:cytology / Q000196:embryology