Photoreceptor thresholds and visual pigment levels in normal and vitamin A-deprived Xenopus tadpoles.
Photoreceptor thresholds and visual pigment levels in normal and vitamin A-deprived Xenopus tadpoles.
复制标题
正常和缺乏维生素 A 的非洲爪蟾蝌蚪的光感受器阈值和视色素水平。
DOI：
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发表时间：
1976
影响因子：
2.5
通讯作者：
C. Bridges
中科院分区：
文献类型：
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作者：
P. Witkovsky;E. Gallin;J. Hollyfield;H. Ripps;C. Bridges
1.测量的视网膜电图（ERG）的磷酸盐分离的PIII组分被用来估计光感受器阈值在黑暗中适应蝌蚪的爪蟾，非洲爪蟾提出了一个正常的饮食。光谱灵敏度函数建立了杆机构管理的绝对暗阈值从第40阶段到结束的premetamorphic发展。2.杆外节尺寸和视色素水平的平行测量表明：a）视色素浓度在所有蝌蚪阶段保持恒定，和B）在premetamorphic发展过程中的阈值下降完全取决于量子吸收的概率增加，伴随着杆外节的增长。3.当蝌蚪获得维生素A缺乏的女性和随后提出的维生素A-免费的饮食，第一次出现的ERG延迟，其绝对阈值提高，相对于控制。4.维生素A剥夺视网膜的组织学检查表明，杆外段保留其结构的完整性，尽管高达75%的视觉色素损失。5.阈值上升，伴随着视觉色素水平下降，无论是由饮食不足或漂白的影响，是大于可以归因于量子吸收的概率减少。
1. Measurements of the aspartate-isolated PIII component of the electroretinogram (ERG) were used to estimate photoreceptor threshold in dark-adapted tadpoles of the clawed toad, Xenopus laevis raised on a normal diet. Spectral sensitivity functions established that the rod mechanism governed absolute dark thresholds from stage 40 to the end of premetamorphic development. 2. Parallel measures of rod outer-segment dimensions and visual pigment levels demonstrated a) that visual pigment concentration remained constant at all tadpole stages, and b) that the fall in threshold over the course of premetamorphic development depended exclusively on the increased probability of quantal absorption that accompanied the growth of the rod outer segments. 3. When tadpoles were obtained from vitamin A-deficient females and raised subsequently on a vitamin A-free diet, the first appearance of the ERG was delayed and its absolute threshold raised, with respect to controls. 4. Histological examination of vitamin A-deprived retinas indicated that rod outer segments retained their structural integrity in spite of up to a 75% loss of visual pigment. 5. The threshold rise which accompanied a fall in visual pigment levels, whether effected by dietary deficiency or by bleaching, was greater than could be attributed solely to a reduction in the probability of quantal absorption.