Guillery R W, Jeffery G, Saunders N
Department of Anatomy, University of Wisconsin, Madison 53706, USA.
J Comp Neurol. 1999 Jan 5;403(1):33-8.
Abnormally reduced uncrossed retinofugal pathways and abnormally low retinal cell densities have been described in albinos of a number of species of eutherian mammal, but have not been studied in marsupials. The optic chiasm of marsupials differs from that of the eutherian brains that have been studied, with uncrossed fibres segregating from crossed fibres prechiasmatically in the marsupials, but not in the eutherians. We have examined the optic chiasm and the retina in albino and normally pigmented wallabies (Macropus rufogriseus) to determine whether the abnormalities found in eutherian albinos are also present in this marsupial. The uncrossed pathway of the albino wallaby is smaller than that of the pigmented animals and the cell density in the retinal ganglion cell layer is reduced at the area centralis. We conclude that the characteristic albino abnormalities are present in both groups of mammals in spite of the other known differences in the visual pathways. The albino mutation acts at the chiasm in a similar manner in both groups even though the determinants of the chiasmatic pathway differ.
在一些真兽类哺乳动物的白化个体中，已发现其未交叉的视网膜神经纤维通路异常减少，视网膜细胞密度异常降低，但有袋类动物尚未有相关研究。有袋类动物的视交叉与已研究的真兽类大脑的视交叉不同，在有袋类动物中，未交叉的纤维在视交叉前就与交叉的纤维分离，而在真兽类动物中并非如此。我们检查了白化和正常有色素的沙袋鼠（赤褐大袋鼠）的视交叉和视网膜，以确定真兽类白化动物中发现的异常是否也存在于这种有袋类动物中。白化沙袋鼠的未交叉通路比有色素动物的小，视网膜中央凹处视网膜神经节细胞层的细胞密度降低。我们得出结论，尽管视觉通路存在其他已知差异，但这两类哺乳动物都存在白化动物特有的异常。白化突变在两类动物的视交叉处作用方式相似，尽管视交叉通路的决定因素不同。
