LIGHT PATH AND PHOTON CAPTURE IN TURTLE PHOTORECEPTORS
LIGHT PATH AND PHOTON CAPTURE IN TURTLE PHOTORECEPTORS
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DOI：
10.1113/jphysiol.1975.sp010983
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发表时间：
1975-01-01
影响因子：
5.5
通讯作者：
FETTIPLACE, R
中科院分区：
文献类型：
--
作者：
BAYLOR, DA;FETTIPLACE, R
1.在海龟的眼睛中，通过细胞内记录来检查单个视锥细胞的方向选择性。从线性响应的单色光入射在一个细胞上的角度范围内，其长轴上的暗淡的闪光确定敏感性。2.当光接近最佳波长时，一些对红色和绿色敏感的视锥细胞对轴向进入的光表现出高灵敏度，而对倾斜进入的光表现出较低的灵敏度。相比之下，其他细胞具有较低的峰值灵敏度和较不明显的方向选择性。在红色受体中观察到的最高轴向灵敏度约为320 μ V光子（-1）μ 2;在这些细胞中，在视网膜中测量时，对偏离轴6-9度的射线的灵敏度下降到一半。绿色受体具有较低的轴向灵敏度和较宽的角度分布。3.假设所有角度的射线都独立地影响整体灵敏度，则可以根据窄束射线确定的角度选择性成功预测细胞对大锥射线的灵敏度。对细胞轴上和轴外传递的微弱刺激的小反应的形状是不变的，这意味着锥体发出吸收光子数量的信号，而不是它们的入射角。4.短波长先前已被证明是由存在于海龟锥油滴过滤掉。在短波长下，角度曲线显示轴向灵敏度降低，与该过滤作用一致。5.在红色、绿色和蓝色敏感视锥中测量内节、油滴和外节的直径，因为这些尺寸预计会影响视锥的角度接受度和收集光的能力。对于每种类型的受体，结构的直径的比例大致相同，但发现直径的绝对值与最大灵敏度的波长相关。6.光学测定的效率与轴向光线集中的红色受体给出了一个平均值为55%。7.发现整个眼睛的组织切片中的受体的方向是其长轴大致指向瞳孔。8.观察到的方向选择性和收集效率与Winston和以诺（1971）在几何光学处理上开发的模型视网膜锥的行为很好地一致。9.推导出红色、绿色和蓝色敏感视锥细胞的有效收集面积;这些允许将观察到的闪光敏感性转换为视觉色素分子异构化产生的平均峰值超极化。所获得的数字对于红色敏感的视锥细胞为约25 μ V，对于绿色敏感的视锥细胞为21 μ V。
1. The directional selectivity of individual cones was examined by intracellular recording in the eye of the turtle. Sensitivites were determined from linear responses to dim flashes of monochromatic light incident on a cell over a range of angles to its long axis. 2. With light near the optimum wave‐length, some red‐ and green‐sensitive cones showed a high sensitivity for light entering axially and lower sensitivities for light entering obliquely. In contrast, other cells had lower peak sensitivities and less pronounced directional selectivities. The highest axial sensitivities observed in red receptors were about 320 muV photon(−1) mu2; in these cells, the sensitivity declined to half for rays 6–9 degrees off the axis as measured in the retina. Green receptors had lower axial sensitivities and broader angular profiles. 3. On the assumption that rays at all angles contribute independently to the over‐all sensitivity, the sensitivity of a cell to large cones of rays was successfully predicted from the angular selectivity determined with a narrow pencil of rays. The shape of small responses to dim stimuli delivered on and off the axis of the cell was invariant, implying that a cone signals the number of photons absorbed but not their angle of incidence. 4. Short wave‐lengths have previously been shown to be filtered out by the oil droplets present in turtle cones. At short wave‐lengths, the angular profiles showed a depression in axial sensitivity consistent with this filtering action. 5. Diameters of inner segments, oil droplets, and outer segments were measured in red‐, green‐, and blue‐sensitive cones, since these dimensions are expected to influence the cones' angular acceptances and ability to collect light. The diameters of the structure were in approximately the same proportions for each type of receptor, but the absolute values of the diameters were found to be scaled in relation to the wave‐length of maximum sensitivity. 6. Optical determinations of the efficiency with which axial rays are concentrated by red receptors gave a mean value of 55%. 7. Receptors in histological sections of the whole eye were found to be oriented with their long axes directed approximately toward the pupil. 8. The observed directional selectivities and collecting efficiencies agree well with the behaviour of a model retinal cone developed by Winston & Enoch (1971) on a geometrical optical treatment. 9. Effective collecting areas are derived for red‐, green‐ and blue‐sensitive cones; these permit conversion of observed flash sensitivities into the mean peak hyperpolarization produced by isomerization of a visual pigment molecule. The figure obtained is about 25 muV for red‐sensitive cones and 21muV for green‐sensitive cones.