Ulshafer R J, Allen C, Dawson W W, Wolf E D
Exp Eye Res. 1984 Aug;39(2):125-35. doi: 10.1016/0014-4835(84)90003-4.
Hereditary blindness in Rhode Island Red chickens was analyzed at various post-hatching stages by light microscopy and electrophysiological recordings. At the time of hatching the retina of affected chicks appeared morphologically normal and identical to that of control, non-affected chicks. Whereas the electroretinographic (ERG) response to light stimulus in normal chicks was near the adult level at the time of hatching, no ERG either under light- or dark-adapted conditions was measurable in affected chicks at any stage examined. Photoreceptor cells of affected animals were seen to undergo degenerative changes after about one week post-hatching. Decrease in number of outer segments, spaces between inner segments and large spaces in the outer nuclear layer were apparent by Day 10. By Day 21, most of the photoreceptor inner segments appeared swollen, and the decrease in number of outer segments and photoreceptor nuclei was noteworthy. By the end of the second month no outer segments were seen and the majority of identifiable inner segments were from cones, a larger proportion than normally present being double cones. By six months, very few photoreceptor inner segments and nuclei remained; most inner segments were deformed and diminutive but usually contained a clearstaining oil droplet characteristic of the principal member of the double cone. In all stages after one week of age, pycnotic nuclei and thinning of inner retinal layers accompanied photoreceptor degeneration. In all specimens examined, degeneration of retinal cells was more pronounced in the superior central retina than in the periphery. Pathological changes were frequently also noted in the pigment epithelium overlying degenerating retina. Because the chick retina is well developed at birth, contains a fovea and a significant cone population and because cones (particularly one specific type) survive rods, we believe that this congenitally-blind chicken may be a useful model for studies on human hereditary retinal degenerations.
通过光学显微镜和电生理记录，在孵化后的不同阶段对罗德岛红鸡的遗传性失明进行了分析。在孵化时，患病雏鸡的视网膜在形态上看起来正常，与对照的未患病雏鸡的视网膜相同。正常雏鸡在孵化时对光刺激的视网膜电图（ERG）反应接近成年水平，而在任何检查阶段，患病雏鸡在明适应或暗适应条件下均未检测到ERG。患病动物的光感受器细胞在孵化后约一周开始出现退行性变化。到第10天时，外段数量减少、内段之间出现间隙以及外核层出现大间隙的情况明显可见。到第21天时，大多数光感受器内段出现肿胀，外段数量和光感受器细胞核数量的减少值得注意。到第二个月末，未见外段，大多数可识别的内段来自视锥细胞，其中双视锥细胞的比例高于正常水平。到六个月时，仅残留极少的光感受器内段和细胞核；大多数内段变形且微小，但通常含有双视锥主要成分特有的清晰染色的油滴。在一周龄后的所有阶段，固缩核和视网膜内层变薄伴随着光感受器变性。在所有检查的标本中，视网膜细胞的变性在视网膜中央上半部分比周边更明显。在退化视网膜上方的色素上皮中也经常观察到病理变化。由于雏鸡视网膜在出生时发育良好，包含中央凹和大量视锥细胞，并且由于视锥细胞（特别是一种特定类型）比视杆细胞存活时间长，我们认为这种先天性失明的鸡可能是研究人类遗传性视网膜变性的有用模型。
