THE PHOTORECEPTOR PROCESS IN VISION 



691 



local failure in the supply or effective utilization of 

 vitamin A (9, 81, 82). The lesions at one stage of 

 vitamin A deficiency resemble somewhat those in 

 retinitis pigmentosa. The layer of rods and cones is 

 the first to deteriorate in vitamin A deficiency, and 

 such deterioration is characteristic of the disease. 

 In more advanced vitamin A deficiency, however, 

 the inner retinal layers also succumb, while remaining 

 apparently intact in retinitis pigmentosa. It is con- 

 ceivable that these symptoms are due to a local 

 failure in vitamin A metabolism which is not ap- 

 parent elsewhere in the eye tissues. 



The participation of vitamin A in the processes 

 of visual excitation therefore introduces a whole 

 series of special relationships. It renders vision de- 

 pendent upon an ecological factor, the nutrition, 

 and upon the entire network of internal arrangements 



that govern the absorption, metabolism and trans- 

 port of vitamin A throughout the body. 



.\ icotinamide 



A second \itamhi plays a basic role in the \isual 

 processes: nicotinamide, the anti-pellagra factor of 

 the \itamin B complex and the active principle of 

 DPN, which is the coenzyme of the alcohol dehy- 

 drogenase system. Without this factor vitamin A 

 presumably cannot be oxidized to retinene, a neces- 

 sary step in the synthesis of rhodopsin and iodopsin. 



Are there visual symptoms in pellagra? Is there, 

 for example, some disturbance of dark adaptation 

 in this disease? None has been reported; but it might 

 be well to examine carefully the visual beha\ior of 

 pellagrins with these considerations in mind. 



REFERENCES 



1. Albrecht, G. S. J. Biol. Chem. In press. 



2. AUERBACH, E. AND G. Wald. Am. J. Ophlli. 39: 24, 1955. 



3. Ball, S., T. W. Goodwin and R. .\. Morton. Biochem. 

 J. 42: 516, 1948. 



4. Bliss, A. F. Arch. Biochem. & Biophys. 31: 197, 1951. 



5. Boll, F. Arch. Anal. & Physiol.: 4, 1877. 



6. BouMAN, M. A. and H. A. van der Velden. J. Opt. Soc. 

 Am. 37:908, 1947. 



7. Broda, E. E. and E. Victor. Biochem. J. 34: 1501, 1940. 



8. Campbell, F. W. and W. A. H. Rushton. J. Physiol. 



■30: '3'. '955- 



9. CocAN, D. G. Tr. Am. Acad. Ophlh.: 629, July-.'\ug. 1950. 

 ga. Denton, E. J. .\'at. Phys. Lab. A. K. Proc. Symp. 8. In press. 



10. Dieterle, J. M. AND C. D. Robeson. Science 120: 219, 



■954- 



11. DoNNER, K. O. J. Physiol. 122: 524, 1953. 



12. DoNNER, K. O. AND R. Gr.\nit. Ada physiol. scandinav. 

 17: 161, 1949. 



laa.DowLiNG, J. E. and G. W'ald. Proc. .\al. Acad. Sc, H'ash- 

 ington 44: 648, 1958. 



13. Farrar, K. R., J. C. Hamlet, H. B. Henbest and E. R. 

 H. Jones. Chem. & Indust.: 49, 1951. 



14. Glover, J., T. W. Goodwin and R. A. Morton. Biochem. 

 J. Proc, 41 : xiv, 1947. 



15. Granit, R. .Ada physiol. scandinav. i : 386, 1941. 



16. Granit, R. .Ada physiol . scandinav. ■2: 334, 1941- 



17. Granit, R. .icia physiol. scandinav. 3: 137, 1942. 



18. Granit, R. Acta physiol. scandinav. 3: 318, 1942. 



19. Granit, R. Acta physiol. scandinav. 4: 118, 1942. 



20. Granit, R. Ada physiol. scandinav. 5: 108, 1943. 



21. Granit, R. Ada physiol. scandinav. 5; 219, 1943. 



22. Granit, R. Sensory .Mechanisms of the Retina. London: 

 0.\ford, 1947, p. 292. 



23. Granit, R., T. Holmberg and M. Zewi. J. Physiol. 94: 

 430, 1938. 



24. Granit, R., A. Munsterhjelm and M. Zewi. J. Physiol. 



96: 31. '939- 



25. Greaves, J. D. and C. I. A. Schmidt. Am. J. Physiol. 

 111:492, 1935. 



26. Haig, C, S. Hecht and \. J. Patek, Jr. Science 87; 534, 

 >938- 



27. Hecht, S. and J. Mandelbaum. Science 88: 219, 1938. 



28. Hecht, S. and J. Mandelbaum. Am. J. Physiol. 130; 

 651, 1940, 



29. Hecht, S., S. Shlaer and M. H. Pirenne. J. Gen. Physiol. 

 25: 819, i94>-42- 



30. Hubbard, R. J. Gen. Physiol. 37: 381, 1953-54. 



31. Hubbard, R. J. Gen. Physiol. 39: 935, 1955-56. 

 31a. Hubbard, R. Nature, London 181: 1126, 1958. 



32. Hubbard, R., R. I. Gregerman and G. \V.\ld. J. Gen. 

 Physiol. 36: 415, 1952-53. 



33. Hubb.ard, R. .\nd G. Wald. Proc. .\at. Acad. Sc, Wash- 

 ington 37:69, 1 95 1. 



34. Hubbard, R. and G. Wald. J. Gen. Physiol. 36: 269, 



■95^-53- 



35. Hume, E. M. and H. .•\. Krebs. Vitamin A Requirements of 

 Human Adults (Medical Res. Council, Special Report 

 Series No. 264). London: His Majesty's Stat. Off., 1949. 



36. Johnson, M. L. A.M. A. Arch. Ophth. 29: 793, 1943. 



37. Krinskv, N. I. J. Biol. Chem. In press. 



38. KiJHNE, \V. In: Handbuch der Physiologic, edited by L. 

 Hermann. Leipzig: Vogel, 1879, vol. 3, pt. i, p. 312. 



39. Oroshnik, W. J. -tm. Chem. Soc. 78: 2651, 1956. 



40. Oroshnik, \V., P. K. Brown, R. Hubbard .\nd G. Wald. 

 Proc. Nat. Acad. Sc, Washington 42: 578, 1956. 



41. Patek, A. J. and C. Haig. J. Clin. Invest. 18: 609, 1939. 



42. Pauling, L. Fortschr. Chem. org. Naturstoffe 3: 203, 1939. 



43. Pauling, L. Helvet. ckim. acta 32: 2241, 1949. 



44. Pirenne, M. H. Brit. .M. Bull. 9: 61, 1953. 



45. Radding, C. M. and G. Wald. J. Gen. Physiol. 39: 909, 



'955-56- 



46. R.\DDING, C. M. and G. Wald. J. Gen. Physiol. 39: 923, 



1955-56- 



47. Robeson, C. D. and J. G. Baxter. J. Am. Chem. Soc. 



69: 136, 1947- 



48. Robeson, C. D., W. P. Blum, J. M. Dieterle, J. D. 



