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In Spain, 2175 patients with skin disease were studied for eye color; 425 had skin cancer and 1750 had other skin conditions. Of the skin cancer patients, 359 had light-colored eyes (blue, green, gray or light brown). Of the others, 60% had dark-colored eyes (black or dark brown).
Kynurenine-H3 transport and conversion to 3-hydroxykynurenine were studied in organ culture using the Malpighian tubules and developing eyes from wild type and the eye color mutants w, st, ltd, ca, and cn of Drosophila melanogaster. Malpighian tubules from wild type have the ability to concentrate kynurenine and convert it to 3-hydroxykynurenine. The tubules from w, st, ltd, and ca are deficient in the ability to transport kynurenine, as are the eyes of the mutants w, st, and ltd. This defect in kynurenine transport provides a physiological explanation for the phenotypic properties of the mutants. The relationship of these measurements to previous observations on these eye color mutants is discussed and the transport defect hypothesis is consistently supported. We have concluded that several of the eye color mutants in Drosophila are transport mutants.
Uptakes of guanine into Malpighian tubules of wild-type Drosophila and the eye color mutants white (w), brown (bw), and pink-peach (pp) have been compared. Tubules for each of these mutants are unable to concentrate guanine intracellularly. The transport of xanthine and riboflavin is also deficient in w tubules. The transport of guanosine, adenine, hypoxanthine, and guanosine monophosphate is similar in wild-type and white Malpighian tubules. These data and other information about these mutants make it likely that these pteridine-deficient eye color mutants do not produce pigments because of the inability to transport a pteridine precursor. This view supports the hypothesis that mutants which lack both pteridine and ommochromes do so because precursors to both classes of pigments share a common transport system.
47 university students provided judgments of the aesthetic value of polygon and histogram shapes that were either symmetric or asymmetric. A sigificant over-all preference to symmetric shapes was evident (p less than .05), and judgments were significantly more positive for brown-eyed subjects. Furthermore, the aesthetic values assigned to shapes showed a systematic interaction with eye color such that brown-eyed subjects produced higher aesthetic ratings for symmetric shapes than blue-eyed subjects, while no such differences appeared for asymmetric shapes.
Recent research had demonstrated that dark-eyed individuals are more reactive than light-eyed people. The present paper investigated one area of reactivity, ease of emotional arousal. The hypothesis that dark-eyed male subjects (n equals 40) would show greater ease of arousal than light-eyed male subjects (n equals 40) was tested using color and form responses on the Rorschach as dependent measures. The predicted interaction was significant; light-eyed subjects gave relatively more form responses, but dark-eyed subjects gave relatively more color responses. Implications for future research and application were discussed.
Several points of biochemical similarity between white and scarlet mutants suggest that both are defective in the transport of xanthommatin precursors. In both, accumulation of 3-hydroxykynurenine is negligible during larval life and occurs at only a slow rate during adult development. Larvae of both mutants also excrete 3H-3-hydroxykynurenine and 3H-kynurenine rapidly, which probably accounts for the normal levels of kynurenine during larval life. 3-Hydroxykynurenine levels are abnormal in all white mutants which were studied, although in two alleles which are strongly pigmented (w(sat) and w(col)) accumulation is enhanced rather than diminished. In w(a), larval accumulation is normal but accumulation during adult development is greatly diminished, suggesting that this mutation has a tissue-specific effect. Similar levels were found in zeste females. Of the 11 other eye color mutants tested, abnormal levels of 3-hydroxykynurenine were found in eight. In four of these (claret, light, lightoid, and pink), larval accumulation is negligible, suggesting that these have defects in the kynurenine transport system like scarlet and white. In three others, however (brown, karmoisin, and rosy), accumulation during larval life is enhanced. In cardinal accumulation is normal during larval life but is excessive during adult development. This evidence supports the suggestion that the cd mutation blocks the final step of xanthommatin synthesis.
Two mutants are described the affect eye pigment in the Culex tarsalis mosquito. The data indicate that carmine eye car, and black eye ble, are each linked to one of the two autosomes. The expression of the two pigment in individuals homozygous for both mutants is unique in that larvae and pupae have car eyes and young adults show both the car and ble phenotypes.
The hypothesis was advanced that dark-eyed subjects are more responsive to arousing stimuli than light-eyed subjects. 40 subjects listened to neutral and arousing auditory stimuli and viewed scenes which were neutral, violent, or sexual in nature. The dependent measure of arousal was a score derived from a combination of physiological responses recorded on a polygraph. Scores were significantly higher for dark-eyed than light-eyed subjects. Significant sex differences were also found, females having higher scores than males. Implications for future research and application were discussed.
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Response latencies to a visual stimulus were determined for 44 male and 82 female Caucasians. Those with dark eyes had significantly shorter simple (one stimulus) reaction times. Complex (one of four stimuli) reaction times showed a similar, but nonsignificant, trend. Data from an additional 206 male Caucasians on a one-trial non-practiced reaction task followed the same nonsignificant trend. Darker iris pigmentation apparently correlates with shorter reaction times but more strongly on practiced tasks and on those which do not involve accuracy.
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