Khan K M, Marovitz W F
Anat Rec. 1982 Apr;202(4):501-9. doi: 10.1002/ar.1092020409.
The rat inner ear is ectodermally derived from a region adjacent to the developing hindbrain. Beginning on day 8 of a 22-day gestational period, This zone of ectoderm first forms the otic placode, then the otocyst, and ultimately the definitive membranous labyrinth. This report provides an estimation of total DNA content of the developing inner ear, and hence an estimation of the total number of cells that comprise the inner ear at each developmental stage. The incorporation of 3H-thymidine indicates that most cells of the inner ear undergo DNA synthetic activity during gestational days 13 to 15. Radioautographic observations indicate a zone of DNA synthetic activity at the base of the outpocketing cochlear duct during early development. At the later stages of development, DNA synthesis is restricted to the cristae ampullares of the semicircular canals and the maculae of the utricle and the saccule. In contradistinction to the findings of other investigators, the statoacoustic ganglion complex undergoes terminal mitosis during gestational days 17 and 18. The gestational period between days 13 and 15 may prove to be a critical stage in normal otic development. The normal values of total DNA content and the number of cells that comprise the inner ear during development, established by these methods, can be compared with pathologic inner ears to provide quantitative means of assessing the damage in malformed inner ears. These values also form the baseline for future experimental studies of inner ear development.
大鼠内耳由外胚层发育而来，起源于与发育中的后脑相邻的区域。在22天妊娠期的第8天开始，这个外胚层区域首先形成耳基板，然后形成耳囊，最终形成定型的膜迷路。本报告提供了发育中内耳总DNA含量的估计值，从而估计了每个发育阶段构成内耳的细胞总数。3H-胸腺嘧啶核苷的掺入表明，内耳的大多数细胞在妊娠第13至15天进行DNA合成活动。放射自显影观察表明，在早期发育过程中，耳蜗管突出部底部存在一个DNA合成活动区。在发育后期，DNA合成仅限于半规管的壶腹嵴以及椭圆囊和球囊的斑。与其他研究者的发现相反，听神经节复合体在妊娠第17和18天进行终末有丝分裂。妊娠第13至15天可能是正常耳发育的关键阶段。通过这些方法确定的发育过程中内耳总DNA含量和构成内耳的细胞数量的正常值，可以与病理性内耳进行比较，以提供评估畸形内耳损伤的定量方法。这些值也为未来内耳发育的实验研究奠定了基础。
