Cataract is a medical problem that largely affects the aging population. Irrespectively of the origin of the various pathological processes, diabetes, exposure to steroids, ionizing radiation etc., the basic physical causes of the turbidity are well understood. Opacity of the lens is due to fluctuations in the refractive index, density and/or orientation fluctuations, on the scale of the wavelength of the light. The density fluctuations, due to aggregation, phase separation or syneresis, received the main attention in the literature. The present proposal tries to elucidate the processes that give rise to orientation fluctuations: supramolecular organization in the lens fibers that can provide optical anisotropy and their disorganization in aging and cataractogenesis. The proposal will study model binary and more complex systems of cytoskeleton-crystallin interaction, individual lens fibers or monolayer fiber cell aggregates and finally thin lens section of animal lenses maintained in organ culture. The optical anisotropy of the systems under investigation will be studied by birefringence, dichroism and polarized light scattering techniques. The interactions that may exist among the different fiber cell constituents will be studied by elastic light scattering, the results of which can be used to evaluate second virial coefficients and subsequently enthalpy and entropy of the interactions. A second way to probe the specific interactions among fiber cell constituents will be the study of constrained swelling ability in confining gels. The proposal aims to give answer what cellular components will contribute to the optical anisotropy and how do orientation fluctuations arise and to what degree they play roles in different cataract formations.
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