EMBRYOLOGY OF THE INNER EAR - A series of organ culture experiments were performed with explanted embryonic mouse inner ears. Two model systems were used, one for normal development (CBA/C57) and one for abnormal development (kreisler), which results in a congenital malformation of the inner ear. The neural inductive interaction that occurs between the brain and the otocyst at early developmental stages was investigated by employing a transfilter interaction apparatus. The critical period for neural induction of this otocyst has been partially defined and this study is continuing. The in vitro interaction of normal/abnormal otocyst, brain tissues suggest that normal tissue may effect abnormal development and vice versa. Chondrogenesis of the otic capsule is being studied in vitro using mesenchyme that is fated under the normal course of development to become otic capsule and extracts from various gestational age otocysts. Biochemical disruption of normal otic capsule chondrogenesis is being studied in vitro observing the effects of the L-Proline analogue, L-Azetodine-2-carboxylic acid or the otocyst being cultured. A model for congenital malformation of the otic capsule is being established and defined through in vitro studies of the homozygotic kreisler inner ears. A fate map of the otocyst of the congenitally malformed homozygotic kreisler otocyst is being completed and compared to the normal (CBA/C57) otocyst fate map. The interrelationship between the ventral mesenchyme, the developing cochlear duct and the coiling mechanisms of the mammalian cochlear duct has been studied. It was concluded that a relationship between cochlear coiling and an intact otic capsule does exist. The role of the developing endolymphatic duct and sac anlage was studied in 12 and 13 day otocysts. This study did not demonstrate an active role of this embryonic anlage of the endolymphatic duct and sac in organogenesis other than the forming of the endolymphatic duct and sac. A developmental anatomical series to study the dreher congenital malformation has been completed and is being analyzed.