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Evaluation of neural fold fusion and coincident initiation of spinal cord occlusion in the chick embryo
Author(s) -
Desmond Mary E.,
Field Marcia C.
Publication year - 1992
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903190205
Subject(s) - neurulation , neural fold , biology , neural tube , anatomy , embryo , spinal cord , neural plate , neuroepithelial cell , microbiology and biotechnology , neuroscience , embryogenesis , embryonic stem cell , genetics , gastrulation , gene
Although it is known that rapid expansion of the vertebrate brain begins near the time that the spinal neurocoel is occluded, it still remains unknown when occlusion occurs in relation to neurulation. Since both morphogenetic events are critical for normal brain growth, it is important to decipher the temporal relationship between the two processes. This study assessed the temporal relationship of the two events with the rationale that if it could be demonstrated that occlusion occurs coincident with the completion of neurulation, then it could be argued that factors shown to direct neurulation could also initiate occlusion. Nearly 600 chick embryos (stages 9− through 12+) were cultured atop egg‐agar, the caudal extent of neurulation determined, the cranial five pairs of somites removed and the neurocoels assessed for occlusion. In stage 9− through 10− chicks, neurulation of the spinal cord is incomplete. Stages 10 through 12+ exhibit neurulation and occlusion from the 8th to 19th somites. When lateral tissues were removed in embryos 8 through 10−, the neural folds became dysraphic whereas in embryos stage 10 and older, the folds remained fused dorsomedially and occluded. The only surgical manipulation that was found to prevent occlusion was elimination of the lateral tissues responsible for elevation and closure of the neural folds. Analysis of particular components of the lateral tissues essential for convergence, by treating embryos (n = 75) with chemicals known to degrade tissue‐tissue bonds or specific components of the perineural matrix, indicated that more than 75% of the embryos treated with EDTA, EDTA plus Ca 2+ , trypsin, collagenase, or hyaluronidase exhibited little or no effect on convergence, dorsomedial fusion, and concomitant occlusion. © 1992 Wiley‐Liss, Inc.