Schreck R E, Bowers R R
Department of Biology, California State University, Los Angeles 90032.
Pigment Cell Res. 1989 May-Jun;2(3):191-201. doi: 10.1111/j.1600-0749.1989.tb00185.x.
Pigment cells of the iris, pecten, retinal pigment epithelium, and choroid of the wild-type jungle fowl (JF) and the barred Plymouth rock (BPR) breeds of adult chickens were studied at both light and electron microscopic levels. BPR choroidal tissues had 2.8 times fewer melanophores than the JF choroid, and BPR melanophores also contained 2.4 times fewer melanosomes, which tended to clump together in variously sized clusters. The melanosomes were often irregular in shape, smaller in diameter, and less mature (stage III) than those granules in the JF. The retinal pigment epithelium of both JF and BPR breeds contained a single epithelial layer of columnar cells. Rod-shaped melanosomes were present in the more apical regions of this cell type in both breeds. Both JF and BPR irides contained a multilayered posterior pigmented epithelium of columnar shaped cells that were densely filled with large spherical granules. Intercellular spaces with interdigitating cytoplasmic projections were present between pigment cells of both breeds. The pecten melanophores of both breeds were dendritic with melanosomes that were larger and fewer in numbers than those pigment cells of the iris and choroid. Intercellular spaces were present between cells in both breeds, with numerous villous-like pigment cell extensions. Choroid melanophores contained very little, if any, acid phosphatase activity. Approximately one-half of the retinal pigment epithelial cells observed contained small amounts of diffuse acid phosphatase activity in both breeds. The iris and pecten melanophores of both breeds contained profuse acid phosphatase activity scattered throughout their cytoplasms. Sparse tyrosinase activity was seen in iris and pecten pigment cells, whereas no tyrosine activity was observed in choroid melanophores or in retinal pigment epithelial cells in the two breeds, indicating that little new melanogenesis occurs in adult pigmented eye tissues. The results show that the barring gene reduces the number and melanin content of the choroidal melanophores in homozygous male BPR chickens as compared to the wild-type JF chickens. Whether this gene prevents the initial migration of embryonic neural crest cells (future melanophores) to the choroid or whether some of the choroidal melanophores prematurely degenerate in the embryo of young birds is yet to be determined. If the latter is the case, this choroid system may serve as a model for a genetic hypomelanotic disease such as vitiligo.
在光学显微镜和电子显微镜水平下，对成年野生型原鸡（JF）和横斑洛克鸡（BPR）品种的虹膜、栉膜、视网膜色素上皮和脉络膜的色素细胞进行了研究。BPR脉络膜组织中的黑素细胞比JF脉络膜中的少2.8倍，并且BPR黑素细胞中的黑素体也少2.4倍，这些黑素体倾向于聚集成大小各异的簇。与JF中的黑素体颗粒相比，这些黑素体的形状通常不规则，直径较小，且成熟度较低（III期）。JF和BPR品种的视网膜色素上皮均包含单层柱状细胞上皮。在这两个品种中，这种细胞类型的更顶端区域存在杆状黑素体。JF和BPR的虹膜均包含多层柱状细胞的后色素上皮，这些细胞密集地充满了大的球形颗粒。两个品种的色素细胞之间均存在具有相互交错的细胞质突起的细胞间隙。两个品种的栉膜黑素细胞呈树突状，其黑素体比虹膜和脉络膜的色素细胞更大且数量更少。两个品种的细胞之间均存在细胞间隙，有许多绒毛状的色素细胞延伸。脉络膜黑素细胞即使有酸性磷酸酶活性也非常少。在两个品种中，观察到的约一半视网膜色素上皮细胞含有少量弥漫性酸性磷酸酶活性。两个品种的虹膜和栉膜黑素细胞在其细胞质中均含有大量分散的酸性磷酸酶活性。在虹膜和栉膜色素细胞中可见稀疏的酪氨酸酶活性，而在这两个品种的脉络膜黑素细胞或视网膜色素上皮细胞中未观察到酪氨酸活性，这表明成年色素化眼组织中几乎没有新的黑素生成。结果表明，与野生型JF鸡相比，横斑基因减少了纯合雄性BPR鸡脉络膜黑素细胞的数量和黑色素含量。该基因是阻止胚胎神经嵴细胞（未来的黑素细胞）最初迁移到脉络膜，还是一些脉络膜黑素细胞在幼鸟胚胎中过早退化，尚待确定。如果是后者，这种脉络膜系统可能作为一种遗传性色素减退疾病（如白癜风）的模型。
