Work is completed and papers being prepared on aspects of human vision: (a) The retinas of women heterozygous for colorblindness (i.e., with colorblind fathers) are a patchwork of normal and colorblind areas, the latter displaying the colorblindness of the father. (b) Measurements of human visual sensitivity in the spectrum down to 310 nm in the ultraviolet were made in normal and aphakic (lensless) subjects. Comparison yields estimates of the absorption of the human lens in situ. They show the absorption to pass over a peak at 340 - 366 nm, depending upon age. The yellow pigmentation seems to be made up largely of three respiratory co-factors: vitamin C, nicotinamide and riboflavine nucleotides, all mainly in the reduced condition. A paper is also being prepared on skin photoreceptors in frogs. An extension of this work is planned, to look into the possibility that certain "eye-spots" on the groins of South American species of Pleurodema are in fact photosensitive, concentrations of such skin photoreceptors as we have studied in northern species, and hence may represent intermediate stages in the evolution of eyes. Measurements are continuing on the regeneration of visual pigments in vertebrate rods and cones and in insect eyes. In the latter regeneration may occur only with resynthesis of microvillar membranes in the photoreceptors. These processes are being followed microspectrophotometrically, and simultaneously with transmission and scanning EM and freeze-etching techniques.
NIH ExPorter
NIH ExPorter