Murray R L, Dubin M W
J Cell Biol. 1975 Mar;64(3):705-10. doi: 10.1083/jcb.64.3.705.
In the retina of the frog and certain other animals, melanin pigment granules move in response to light so as to shield photoreceptor outer segments. The granules are contained within the cells of the pigment epithelium (PE) which lie as a continuous sheet between the neural retina and the choroid. Moderate illumination of the eye causes the melanin granules to move from a region within a PE cell body into numerous fingerlike extensions of the cell which interdigitate with the receptor outer segments. This migration takes many minutes and is reversed when the light falling on the eye increases in intensity. Several reviews are concerned with the early descriptions of this phenomenon (6,30) and with more recent experiments (1,5,19). The mechanism of the pigment granule motion is undetermined although there are studies concerning PE ultrastructure (8, 23, 31), scanning electron microscopy of the fingerlike extensions of the PE cells (27), the role of the PE in photoreceptor phagocytosis (32), the nature of the pigment granules (19), and the action spectrum of the light which induces the migration (16). This study reports the presence of a system of microfilaments associated with the pigment granules in the fingerlike extensions processes of the PE cells. We demonstrate by heavy meromyosin (HMM) labeling that the filaments are actinlike in character and suggest that these filaments could be responsible for the migration of the melanin pigment granules.
在青蛙和某些其他动物的视网膜中，黑色素颗粒会根据光线移动，从而保护光感受器的外段。这些颗粒包含在色素上皮（PE）细胞内，色素上皮细胞呈连续的一层，位于神经视网膜和脉络膜之间。对眼睛进行适度照明会使黑色素颗粒从PE细胞体内的一个区域移动到细胞的许多指状延伸部分，这些延伸部分与感受器外段相互交错。这种迁移需要几分钟时间，当照射到眼睛的光线强度增加时，迁移过程会逆转。有几篇综述涉及对这一现象的早期描述（6,30）以及最近的实验（1,5,19）。尽管有关于PE超微结构（8, 23, 31）、PE细胞指状延伸部分的扫描电子显微镜观察（27）、PE在光感受器吞噬作用中的作用（32）、色素颗粒的性质（19）以及诱导迁移的光的作用光谱（16）的研究，但色素颗粒运动的机制仍未确定。本研究报告了在PE细胞的指状延伸过程中存在与色素颗粒相关的微丝系统。我们通过重酶解肌球蛋白（HMM）标记证明这些细丝具有肌动蛋白样的特征，并表明这些细丝可能是黑色素颗粒迁移的原因。
