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LA MORPHOGENESE PRIMORDIALE DU GANGLION STATO-ACOUSTIQUE ET DE L'OREILLE INTERNE CHEZ L'EMBRYON DE SOURIS. I. ANALYSE DE LA MORPHOGENESE PRECOCE CHEZ LES EMBRYONS DE 9, 9 1/2 ET 10 JOURS

par Bretos Alarcon-Moraga, Marta
Référence Archives de biologie, 90, 2, page (195-224)
Publication Publié, 1979

Article révisé par les pairs

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Résumé :

The distribution of RNA, polysaccharides, alkaline and acid phosphatases at successive developmental stages have been analysed in serial transverse sections of the otic region. Sections submitted to the Unna-Brachet method have permitted the study of the morphological evolution of embryonic primordia, and of the programmed cellular death sites. Certain aspects of nerve fiber development have been elucidated through observations of sections treated for alkaline phosphatase enzymatic reaction. Acid and alkaline phosphatase tests have revealed the evolution of the primitive sensory areas. Otocyst dissections have allowed a better understanding of the morphological changes which the primitive otic vesicle undergoes during this period. Several transitory histochemical and morphological features suggest the successive contribution of two different inductors in the primary morphogenesis of the normal auditory placode: the parachordal mesoderm and the rhombencephalon. In addition, the histochemical properties of the invaginating otic pit wall testify the acquisition of a double antero-posterior and dorsoventral polarization. The presumptive sensory area for the future anterior and lateral ampullae and for the utricular macula is easily localized owing to its selective alkaline phosphatase activity. This area is the first to arise from the macula communis. The first primordium of the stato-acoustic ganglion arises from cells migrating from the rostro-ventral wall of the primary auditory vesicle. In this early primordium, we found two portions, one medial and the other lateral. The latter is characterized by its alkaline phosphatase reaction and by its location dorsal to the geniculate ganglion primordium. These two primitive portions do not correspond to the future vestibular and cochlear ganglia. The central sensitive nerve fibers of the ganglionic complex appear very early, before the constitution of the different ganglionic groups. Later on, the motor fibers of the facial nerve become evident. Among the peripheric nerve connections, the anterior ramus fibers become visible earlier.