Frogs, retina

By comparing the BAT absorbance in a frog retina with that in a suspension of rod outer segments, Yoshizawa and co-workers concluded that the angle between the retinal transition moment of bathorhodopsin and the disk membrane plane is considerably smaller than that of rhodopsin (0° vs 18° respectively) (327,328). Such a change in geometry is consistent with an all-trans structure in BAT, but not with a simple proton translocation. 

Rodriguez de Turco EB, Gordon WC, Bazan NG. Rapid and selective uptake, metabohsm and cellular distribution of docosahexaenoic acid among rod and cone photoreceptor cells in the frog retina. J Neurosci 1991 lll(l) 3667-3678. 

Wetts, R. and Fraser, S.E. (1988) Multipotent precursors can give rise to all major cell types of the frog retina. Science 239 1142-1145. 

Two recent OCT studies measured slow scattering changes in the dissociated vertebrate retina, in which intrinsic signals had been measured by other techniques (2d). In one study, functional changes from light-activated frog retina in vitro (27) were recorded. In another, increases in scattering at particular depths were reported in rabbit retina 28). 

Goldstein EB (1970) Cone pigment regeneration in the isolated frog retina. Vision Res 10 1943-1951 Bunt-Milan AH, Saari JC (1983) Inununocytochemical localization of two retinoid-binding proteins in vertebrate retina. J Cell Biol 97 703-712... 

The only two cases where a repetitive pattern was shown by X-ray diffraction concerned the chloroplast membrane (von Kreutz and Mencke, 1962 von Kreutz, 1964) and the photoreceptor membranes of the frog retina (Blasie et al., 1969). In both cases the observed patterns concerned protein units these, in the first case, measured 35 A and formed a planar array (see Fig. 10a) at the surface of a lipid layer. In the second case, the units were cylindrical molecules of rho-dopsin the evidence clearly excluded the possibility for these particles to be spherical lipoproteins or lipid micelles since their cross-sectional electron density was not characteristic of these phases, but definitely that of protein. 

Baumann, C., The equilibrium between metarhodopsin 1 and metarhodopsin 11 in the isolated frog retina, /. Physiol, 279, 71,1978. 

Gedney, C., Ward, J., and Ostroy, S.E., Isolation and study of rhodopsin and cone responses in the frog retina. Am. /. Physiol, 221,1754,1971. 

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