ISSN:
1432-0568
Keywords:
Nasal development
;
Epithelial fusion
;
Nasal fin regression
;
DNA synthesis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Fusion between the epithelial linings of the medial and lateral nasal swellings transforms the nasal groove into a primitive nasal cavity and forms an epithelial seam, the nasal fin, in the line of contact. Epithelial contact occurs between a restricted group of opposing epithelial cells; adjacent eithelial cells do not fuse but form the linings of the nasal and oral cavities. After its formation, the epithelial nasal fin regresses and is replaced by mesenchymal cells, except for a small posterior portion which remains as the bucconasal membrane. DNA synthesis at 3 different periods (20, 10 and 5 h) before contact on day 11 3/4 was examined in the fusing epithelia and adjacent non-fusing epithelia. DNA synthetic activity decreased in both regions at successive stages of development. Howerer, the decrease in the presumptive fusing epithelia at 10 and 5 h before contact was noteworthy in that it was significantly greater than in the non-fusing epithelia. In the fusing epithelia this decrease of DNA synthetic activity occurred not only in prospective degenerating cells, but was a general phenomenon involving viable cells also. To analyze the regression of the nasal fin, it was studied in serial sections. The majority of the cells were viable and only few degenerating cells were seen, suggesting that not all cells of the nasal fin undergo necrosis. Since the epithelial cells of the nasal fin always appeared to be separated from the surrounding mesenchymal cells, the transformation of surviving cells into mesenchymal cells appears unlikely. It is postulated that surviving epithelial cells are incorporated into the adjacent epithelia of the primitive oral and nasal cavities.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00299258
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