RESUMO
Cleft lip with or without associated cleft palate [CL(P)], one of the most common human malformations, is believed to be caused by a combination of genetic and environmental factors. To study the morphological manifestations of genetic factors in this interaction, we compared the embryonic development of the CL/Fr mouse strain (with a mean incidence of 36% spontaneous CL(P) in our colony) with that of the C57B1/6J mouse strain (with no CL(P) in our colony). Results from our scanning electron microscopic study demonstrated that, when compared with C57B1/6J embryos, CL/Fr embryos have several developmental differences including: 1) altered facial geometry, 2) depressed ability of the surface epithelium of primary-palate primordia to participate in the fusion process, and 3) variable hypoplasia of the lateral nasal prominences. We suggest that all of these alterations may contribute to the pathogenesis of CL(P) in the CL/Fr mouse strain.
Assuntos
Fenda Labial/embriologia , Fissura Palatina/embriologia , Camundongos/embriologia , Animais , Epitélio/embriologia , Face/embriologia , Camundongos Endogâmicos C57BL , Microscopia Eletrônica de VarreduraAssuntos
Anormalidades Múltiplas/embriologia , Megacolo/embriologia , Crista Neural/fisiologia , Neoplasias da Glândula Tireoide/embriologia , Síndrome de Waardenburg/embriologia , Animais , Carcinoma/embriologia , Movimento Celular , Embrião de Galinha , Modelos Animais de Doenças , Face/anormalidades , Humanos , Crista Neural/ultraestrutura , RatosRESUMO
High incidences of cleft lip and palate (CLP) produced by maternal intraperitoneal administration of 75 mg/kg phenytoin on gestational day 10 to A/J mice are associated with a severe size reduction in the lateral nasal process. Scanning and transmission EM analyses of this region demonstrate a marked change in the morphology of the mesenchymal cells underlying the surface epithelium in treated versus control day 11 (7-tail somite) embryos: long, branching cellular processes, which form a dense meshwork that appears to interact with the epithelial basement lamina in control embryos are undeveloped or absent in phenytoin-treated embryos. The ultrastructural morphology of these cell processes is described and their possible importance in normal development is discussed. Scanning EM observations of incomplete clefts of the lip which frequently result from phenytoin treatment indicate that Simonart's bands form from fusion of the lateral and medial nasal processes in association with a lack of fusion of the maxillary process with the medial nasal process.
