Wikler K C, Perez G, Finlay B L
Department of Psychology, Cornell University, Ithaca, New York 14853.
J Comp Neurol. 1989 Jul 8;285(2):157-76. doi: 10.1002/cne.902850202.
The Mongolian gerbil (Meriones unguiculatus) has a prolonged period of development relative to other muroid rodents. We have explored the consequences of this relatively long period of maturation on retinal cell number and topography by comparing the duration and topography of neurogenesis in the gerbil retina with that of a closely related species which develops rapidly, the Syrian hamster (Mesocricetus auratus) (Sengelaub et al.: J. Comp. Neurol. 246:527-543, 1986). An analysis of thymidine-labeled retinas indicate that cells destined for the gerbil retinal ganglion cell layer are generated for at least 12 embryonic days, twice the duration in the hamster. The period of cell loss in the gerbil retinal ganglion cell layer extends for at least 14 postnatal days, more than twice as long as in the hamster. The gerbil retina is generated in a center-to-periphery gradient for both retinal ganglion cells and displaced amacrine cells, while no such gradients are evident in the hamster retina. We conclude that the longer developmental period of the gerbil is associated with 1) a longer period of neurogenesis resulting in greater retinal cell number, 2) the expression of spatial gradients in neurogenesis, and 3) a larger eye at maturity. The last two factors, in part, may be related to the development of a highly differentiated area centralis and visual streak in the retina of this rodent. Unrelated to duration of growth, early differences in retinal shape between these two species contributes to the development of retinal topography. The gerbil, but not the hamster retina, is initially asymmetric, longer in its nasotemporal than its dorsoventral dimension. The gerbil retina then grows asymmetrically, producing a spherical retina, and coincident in time, a nasotemporally extended visual streak.
与其他鼠科啮齿动物相比，蒙古沙鼠（长爪沙鼠）的发育周期较长。我们通过比较长爪沙鼠视网膜神经发生的持续时间和拓扑结构与发育迅速的近缘物种叙利亚仓鼠（金仓鼠）的相应情况，探讨了这种相对较长的成熟期对视网膜细胞数量和拓扑结构的影响（森盖劳布等人：《比较神经学杂志》246:527 - 543，1986年）。对用胸苷标记的视网膜进行分析表明，注定要进入长爪沙鼠视网膜神经节细胞层的细胞至少在胚胎期产生12天，这一持续时间是仓鼠的两倍。长爪沙鼠视网膜神经节细胞层的细胞丢失期至少持续出生后14天，比仓鼠的时间长两倍多。长爪沙鼠的视网膜在视网膜神经节细胞和移位无长突细胞方面都是从中心到周边呈梯度生成的，而在仓鼠视网膜中则没有这种梯度。我们得出结论，长爪沙鼠较长的发育期与以下因素有关：1）较长的神经发生期导致视网膜细胞数量增多；2）神经发生中空间梯度的表达；3）成熟时眼睛更大。后两个因素部分可能与这种啮齿动物视网膜中高度分化的中央凹和视条纹的发育有关。与生长持续时间无关，这两个物种视网膜形状的早期差异有助于视网膜拓扑结构的发育。长爪沙鼠的视网膜最初是不对称的，鼻颞侧比背腹侧长，而仓鼠视网膜则不是。然后长爪沙鼠的视网膜不对称生长，形成球形视网膜，并同时形成鼻颞侧延伸的视条纹。
