Kaplan M W, Deffebach M E
Biophys J. 1978 Jul;23(1):59-70. doi: 10.1016/S0006-3495(78)85432-0.
The birefringence (deltan) of Rana pipiens rod outer segments (ROS) reveals microstructure inhomogeneities not seen with other techniques. In the basal 20-30-micron length of the ROS there is a nearly linear axial gradient in deltan of approximately equal to -2 x 10(-5)/micron. No consistent deltan gradients are found in the distal 20-30 micron of the ROS. Using glycerol imbibition to separate the intrinsic and form birefringence components, we found that the basal deltan gradient was principally due to a gradient of the intrinsic birefringence component. The disk membrane volume fraction decreases uniformly from the basal end to the distal end, while the disk membrane refractive index increases. The contributions of these changes to the form birefringence approximately cancel, so that the form component is fairly uniform along the ROS axis. Because its axial distance from the inner segment is a measure of the time since a disk membrane was formed, these gradients may reflect a disk membrane aging process. Occasionally a highly birefringent, 2-micron-wide band is seen at the basal end ot the ROS, possibly where the envelope membrane folds to form new disk membranes.
牛蛙视杆细胞外段（ROS）的双折射（δn）揭示了用其他技术无法看到的微观结构不均匀性。在ROS基部20 - 30微米长度范围内，δn存在近似线性的轴向梯度，约为 -2×10⁻⁵/微米。在ROS远端20 - 30微米范围内未发现一致的δn梯度。通过甘油浸润分离固有双折射和形态双折射成分，我们发现基部δn梯度主要归因于固有双折射成分的梯度。盘膜体积分数从基部末端到远端均匀降低，而盘膜折射率增加。这些变化对形态双折射的贡献大致抵消，因此形态成分沿ROS轴相当均匀。由于其距内段的轴向距离是盘膜形成后时间的一种度量，这些梯度可能反映了盘膜老化过程。偶尔在ROS基部末端可见一条高度双折射、宽2微米的带，可能是包膜膜折叠形成新盘膜的位置。
