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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 56, Iss. 1 — Jan. 1, 1966
  • pp: 116–123

Validation of an Indicator of Mammalian Retinal Receptor Response: Density of Stain as a Function of Stimulus Magnitude

JAY M. ENOCH  »View Author Affiliations

JOSA, Vol. 56, Issue 1, pp. 116-123 (1966)

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A bipartite field (retinal irradiance ratio 2:1 on the two sides) was imaged on the retina of an albino rat. Following exposure to the visual stimulus, the retina was dissected from the eye and placed in an incubation medium which selectively stains the ellipsoid portion of photoreceptors which have been exposed to light. In this study, the optical density of stain was measured as a function of stimulus magnitude. It was shown that the density of stain increased with increasing retinal irradiance over the range of values tested. The indicator system tended to underestimate differences in stimulus magnitude, and showed evidence of approaching an asymptote at higher stimulus levels. Many technical problems encountered in this experiment made this a difficult exercise.

JAY M. ENOCH, "Validation of an Indicator of Mammalian Retinal Receptor Response: Density of Stain as a Function of Stimulus Magnitude," J. Opt. Soc. Am. 56, 116-123 (1966)

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  1. J. M. Enoch, Invest. Ophthalmol. 2, 16 (1963).
  2. Somewhat similar incubation media are used to localize the sites of activity of the enzyme, succinic dehydrogenase. When succinate, the substrate, is present (in the medium in which the tissue is incubated), the nitro-blue tetrazolium is reduced at some point in the succinoxidose system, and a blue-violet insoluble pigment (dinitro-formazan) is deposited, most probably at the point where the reaction occurs.
  3. J. M. Enoch, J. Opt. Soc. Am. 54, 368 (1964).
  4. J. M. Enoch, J. Opt. Soc. Am. 54, 1027 (1964).
  5. W. Sickel (Johns Hopkins University) writes that he has detected the reaction in frogs.
  6. J. M. Enoch, Am. J. Optom. 42, 63 (1965).
  7. W. L. Fowlks, Proc. Soc. Exp. Biol. Med. 118, 491 (1965).
  8. W. L. Fowlks, Invest. Ophthalmol. 3, 550 (1964).
  9. I. Osipova and S. Shukoljukov, Cytologia 6, 626 (1964), in Russian.
  10. B. Commoner and D. Lipkin, Science 110, 41 (1949).
  11. This medium was employed because it has been shown that it provides lower stain thresholds, and results obtained seem more sharply delineated than those evoked when we used the second medium we developed.4 We have obtained quantitative stability using the Sigma product. In the past, we have found it necessary to keep our NBT cold, dark, and dry. We divide a lot into several dark bottles because we find that after a sample has been used some unspecified number of times the NBT rather rapidly loses potency. A stored, second unopened bottle of the same lot has approximately original potency. (The first few mixtures made from a new bottle have an apparent increased potency over that usually measured.) We usually are able to make at least sixty valid determinations per bottle. Potency is defined in terms of threshold stimulus magnitude required to produce a stained image in our preparations.
  12. A. Pearse, Histochemistry, Theoretical and Applied (Little, Brown and Company, Boston, 1961), p. 543.
  13. R. Cone, J. Gen. Physiol. 46, 1267 (1963). See comments on this paper in Ref. 3. The reader is referred to Cone's paper for an error analysis concerning each of the factors employed. In recent conversations with Dr. Cone, he has pointed out that he has reproduced the experiment by Lewis mentioned in Ref. 13 [D. Lewis, J. Physiol. (London) 136, 615 (1957)], and found Lewis's values to be valid. Lewis suggested that 0.50 of the energy incident at the retina was absorbed by the rhodopsin at λ = 500 nm. The value employed in Table II (0.23) was taken from measurements made by Paul Brown (Harvard University) for Dr. Cone. Brown used excised retinas, Lewis used whole excised eyes. In dead and dying retina there is increased scatter, swelling, and reduced transmittance of light.6 The orientation of the photosensitive pigment molecules may be altered. The rod receptors are physically separated, and part of the energy transmitted in a wave-guide is carried outside of the cell. Lewis's data are more subject to stray-light effects because of the integrating-sphere-like action of the rat eye. In that experiment, bleaching in an image per se cannot be distinguished from that produced by stray light on the remaining retina. I believe that the value provided by Brown may be somewhat more applicable to the measurements made here. Hence, Brown's estimate is retained in this analysis. Obviously, this is a weak point in the treatment and it needs to be better defined.
  14. J. Dowling, J. Gen. Physiol. 46, 1287 (1963).
  15. The stray light caused by the more intensely stimulated side of the image would have a slightly greater effect upon the less stimulated side than vice versa.
  16. K. Patau, Chromosoma 5, 341 (1952).
  17. L. Ornstein, Lab. Invest. 1, 250 (1952).
  18. W. Marks, W. Dobelle, and E. MacNichol, Science 143, 1181 (1964).
  19. P. Brown and G. Wald, Science 144, 45 (1964).

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