Photoreceptor inner segments in monkey and human retina: Mitochondrial density, optics, and regional variation
Photoreceptor inner segments in monkey and human retina: Mitochondrial density, optics, and regional variation
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DOI：
10.1017/s0952523802194028
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发表时间：
2002-07-01
影响因子：
1.9
通讯作者：
Curcio, CA
中科院分区：
文献类型：
--
作者：
Hoang, QV;Linsenmeier, RA;Curcio, CA
目前的工作量化了与线粒体、内部节段尺寸和光学特性相关的光感受器结构的各个方面，作为进一步理解视杆细胞和视锥细胞功能的基础。对一只短尾猕猴（Macaca arctoides）的视网膜进行电子显微镜分析，以获得椭圆体线粒体密度以及外节和内节的大小和形状的体视测量。此外，还利用电子显微镜和诺马斯基微分干涉对比（NDIC）成像检查了线粒体的分布和人类中心凹锥体的光学特性。在猕猴中，线粒体由 74-85% 的视锥椭球体和 54-66% 的视杆椭球体组成。当偏心率达到 12.75 mm 时，椭球体体积随偏心率增加，对于杆而言增加 2.4 倍，对于锥体则增加超过 6 倍，而对于杆和锥体来说，由椭球体支撑的外部段的体积基本恒定。每单位体积的外节中，视锥细胞含有的线粒体数量是视杆细胞的十倍。在人类中央凹中，与视网膜的其余部分一样，大多数视锥细胞线粒体位于远端内段。然而，在中心凹中心，肌样中以及靠近外界膜 (ELM) 的外纤维中也有线粒体。对人类中心凹锥体的光学孔径（其折射率与感受器外空间的折射率明显不同的点）的分析表明，它与线粒体的位置密切相关，但在中心凹中心除外，其中孔径出现在 ELM 附近。虽然线粒体具有重要的代谢功能，但我们认为杆状体和锥状体之间线粒体含量的显着差异不太可能仅由代谢需求决定。大量的视锥细胞线粒体可以增强视锥细胞的波导特性，特别是在外围。
The present work quantifies aspects of photoreceptor structure related to mitochondria, inner segment dimensions, and optical properties, as a basis for furthering our understanding of rod and cone function. Electron-microscopic analyses were performed on the retina of one stumptail macaque (Macaca arctoides) to obtain stereological measurements of ellipsoid mitochondrial density, and sizes and shapes of outer and inner segments. In addition, the distribution of mitochondria and the optical properties of human foveal cones were examined with electron microscopy and Nomarski differential interference contrast (NDIC) imaging. Mitochondria comprised 74-85% of cone ellipsoids and 54-66% of rod ellipsoids in macaque. Ellipsoid volume increased with eccentricity by 2.4-fold for rods and more than 6-fold for cones over eccentricities to 12.75 mm, while the volume of the outer segment supported by the ellipsoid was essentially constant for both rods and cones. Per unit volume of outer segment, cones contained ten times as much mitochondria as rods. In human fovea, as in the rest of the retina, most cone mitochondria were located in the distal inner segment. In the foveal center, however, there are also mitochondria in the myoid, as well as in the outer fiber, proximal to the external limiting membrane (ELM). Analyses of the optical aperture of human foveal cones, the point at which their refractive index clearly differs from the extrareceptoral space, showed that it correlated well with the location of mitochondria, except in the foveal center, where the aperture appeared proximal to the ELM. While mitochondria have an important metabolic function, we suggest that the striking differences between rods and cones in mitochondrial content are unlikely to be determined by metabolic demand alone. The numerous cone mitochondria may enhance the waveguide properties of cones, particularly in the periphery.