Xenbase Image ID: 122278

Figure 2. . Intensity–response curves of larval and adult Xenopus rod photoreceptors. (A) Responses are plotted as a function of flash intensity for tadpoles (black circles, n = 6) and froglets (gray triangles, n = 8). The amplitude of the responses of froglet rods were three times larger than the responses of tadpole rods, similar to the saturating currents. The gray circles represent the scaled (i.e., multiplied by three) responses of tadpole rods. (B) The squared value of the mean responses (black) was compared with the ensemble variance (gray) for young tadpole and froglet rods (16–25 flash repetitions). Flash intensity was 0.32 hυ/μm2. Applying Poisson statistics to these examples, the estimated mean number of photoisomerizations per flash (R*) was 1.1 for the tadpole rod, and 2.5 for the froglet rod. The estimated values of the collecting areas were 3.8 and 8.6 μm2 for the tadpole and froglet rods, respectively. (C) Tadpole and froglet rod collecting areas plotted as a function of ROS length. On average, the collecting areas grew in proportion to ROS length and triple in value, indicating that the optical density per unit of ROS length (pigment density) does not vary with stage of development. (D) Peak responses from A plotted as a function of photoisomerizations per flash (R*). On average, the response of both tadpole and froglet rods to single photoisomerizations (arrow) did not differ (∼0.6 pA). At low light intensities (0–10 R*), the responses from tadpole and froglet rods were the same. Image published in: Solessio E et al. (2004) Copyright © 2004, The Rockefeller University Press. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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