. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 154 T. A. WEBB l-:i I/. Figure 5. LIV light reverses the effect of demecolcine on tubulin poh men/ation. The eggs shown in (A). (C). and (E) were neither treated with demecolcine nor irradiated with UV light: those shown in (Bl. (D). and (F) were Healed with demecolcine and irradiated with UV light ( X 10" quanta s~' ^nr:) either iv; //•/;/ and en /</ic irradiation ga\e identical results in all three regions ol the egg. Scale har, 10 ^m. moved beyond the edge of the UV-irradiated region, sug- gesting that
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 154 T. A. WEBB l-:i I/. Figure 5. LIV light reverses the effect of demecolcine on tubulin poh men/ation. The eggs shown in (A). (C). and (E) were neither treated with demecolcine nor irradiated with UV light: those shown in (Bl. (D). and (F) were Healed with demecolcine and irradiated with UV light ( X 10" quanta s~' ^nr:) either iv; //•/;/ and en /</ic irradiation ga\e identical results in all three regions ol the egg. Scale har, 10 ^m. moved beyond the edge of the UV-irradiated region, sug- gesting that microtubules that formed in the irradiated region subsequently extended beyond this region. Irra- diation of the egg 01 lace likely photolyzed demecolcine in the ooplasm on both the near side of the egg and its antipode as well as in the portion of the yolk vacuole that is in the light path. As molecules of demecolcine were inactivated within the irradiated region and the product diffused away from it. molecules of demecolcine in ad- jacent, unirradiated regions diffused into the irradiated region. In other words, the irradiated region acted as a demecolcine sink, and eventually the concentration of demecolcine decreased throughout the egg. The spatio- temporal pattern of the change in demecolcine concen- tration in an irradiated egg presumably depends on at least three variables: (a) the initial concentration of de- mecolcine in the egg. (b) the intensity of the UV light, and (c) the volume of the irradiated region. Our results demonstrate that all three variables affected the extent to which UV irradiation reversed the effects of demecolcine on oil droplet movement, cleavage, and subsequent de- velopment. Irradiation of control medaka eggs with UV light (360 nm) at intensities adequate to regenerate microtu- bules and normal movement of oil droplets in poisoned eggs had no apparent effect on ooplasmic segregation. These results are consistent with those of other studies in
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
