[Experimental study on early development of rat ear in vitro using whole embryo culture]

Rat embryos were explanted on late 11 day of gestation and cultured for 24 hours in rotating bottles with the yolk sac opened. Rat serum was used as culture medium and culture bottles were filled with 5% CO2 + 95% O2 gas mixture as gas phase. At the time of explantation and the end of the culture period, differentiation and growth of the embryos were monitored by counting somites and measuring crown rump length. About part of the embryos, protein determinations were made to measure growth. These data were compared with values found for 12 and 13 day embryos. The results for cultured embryos showed slight retardation in their differentiation and slight depression in the growth. At the same time to study early inner ear development in vitro, 9 of the other cultured embryos were serially sectioned and observed by light microscopy. In the cultured embryos endolymphatic duct elongated and acoustico-facial ganglion enlarged remarkably. Otocysts became flattened and elongated ventrally. Vestibular and cochlear portion were identifiable in the otocysts. Nerves arose from the ganglion reached to brain centrally and wall of pharynx peripherally. There was no significant difference in inner ear development between 13 day and the cultured embryos. This culture system should prove useful for studies on early inner ear development of mammalian embryos.