In vivo study of apoptosis as a creative agent of embryonic development of the primary nasal duct in rats.

INTRODUCTION: The first embryonic part of the nasal cavity is the primary nasal duct, beginning with the olfactory placode and ending with the oronasal membrane. Aim of this study was to investigate the cellular processes (apoptosis, proliferation) being responsible for development and opening of the primary nasal duct. MATERIAL AND METHODS: In this study developmental processes in at least three regions of the primary nasal duct (opening, middle, end) were examined by sectioning 38 rat fetuses on day 13.5 after conception. Apoptotic cells were detected by active caspase-3 antibodies and proliferating cells were examined by Ki-67 antibodies. RESULTS: Multiple apoptotic events were diagnosed on the basis and proliferative cells on the top of this duct. CONCLUSION: Apoptosis and proliferation play an important role in the process of opening the bottom of the primary nasal duct and for development of the nasal septum, philtrum as well as the primary palate. Mesenchymal proliferation seems to play a minor role in the process of opening the primary nasal duct.

Apoptosis as a creative agent of embryonic development of bucca, mentum and nasolacrimal duct. An in vivo study in rats.

INTRODUCTION: For embryonal facial development several fusion processes between different facial prominences are necessary. If fusion fails to appear, various facial clefts may occur, known as median (e.g. lower median cleft lip), oblique (e.g. open nasolacrimal duct) or lateral facial clefts (macrostomia, lateral cleft). MATERIAL AND METHODS: The development of 3 different facial regions (bucca, mentum, and nasolacrimal duct) was examined in rats using serial histological sections on day 13.5 after conception. Common procedures were used (staining for active caspase-3 and for Ki-67) for histological assessment about the role of apoptotic and proliferative processes in the fusion zones of buccal, mental and nasolacrimal areas. RESULTS: Multiple apoptotic events were detected in epithelial cells of the respective regions, the proliferative centers were located in the mesenchymal surroundings of fusion zones. CONCLUSION: A substantial precondition for fusion of facial prominences are proliferative and apoptotic processes in epithelial and mesenchymal cells. Apoptosis contributes to the development of bucca, mentum and the nasolacrimal duct. Absence of apoptoses may be responsible for facial clefts.

Initial findings on teratological and developmental relationships and differences between neural tube defects and facial clefting. First experimental results.

Unless genetically caused, the occurrence of neural tube defects and clefts of the lip, alveolus and palate are not associated. These malformations do, however, share some common causes, one of which is folic acid deficiency. Nevertheless, it is not known why a neural tube defect resulting from folic acid deficiency does not occur in combination with facial clefts. Based on animal experiments and a review of the literature, it is assumed that other factors--such as vitamin B6 deficiency--though clinically not diagnosed, can more often cause malformations.