August 1990
Volume 31, Issue 8
Free
Articles  |   August 1990
Distribution of carbonic anhydrase among human photoreceptors.
Author Affiliations
  • T M Nork
    Department of Ophthalmology, West Virginia University Health Sciences Center, Morgantown 26506.
  • S A McCormick
    Department of Ophthalmology, West Virginia University Health Sciences Center, Morgantown 26506.
  • G M Chao
    Department of Ophthalmology, West Virginia University Health Sciences Center, Morgantown 26506.
  • J V Odom
    Department of Ophthalmology, West Virginia University Health Sciences Center, Morgantown 26506.
Investigative Ophthalmology & Visual Science August 1990, Vol.31, 1451-1458. doi:
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      T M Nork, S A McCormick, G M Chao, J V Odom; Distribution of carbonic anhydrase among human photoreceptors.. Invest. Ophthalmol. Vis. Sci. 1990;31(8):1451-1458.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The distribution of carbonic anhydrase (CA) among human photoreceptors has been a topic of dispute. In our experiments, by modifying an established enzyme histochemical technique, reproducible staining was observed. Of the cones in the peripheral retina, 91% were positive for CA. The CA-negative (CA-) cones were absent within approximately 8 arc min of the foveal center and their density peaked at 2 arc deg. No CA activity was found in the rods. Morphologic differences were noted between the CA-positive (CA+) and CA- cones. Compared to the CA+ cones, the CA- cones had longer and more nearly columnar inner segments, more nearly spherical nuclei, and more generous amounts of perikaryal cytoplasm. In the peripheral retina, the distance between CA+ to CA+ nearest neighbors were larger compared to CA- to CA+ nearest neighbors (P less than 0.0001). The frequency distribution and morphology of the CA- cones suggest that they are the blue-sensitive cones. As such, this study demonstrates a biochemical similarity between blue cones and rods that may provide insight into the function and phylogeny of the blue cones.

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