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  • Title: Light scattering and morphology of cataract formation in transgenic mice containing the HIV-1 protease linked to the lens alpha A-crystallin promoter.
    Author: Bettelheim FA, Churchill AC, Siew EL, Tumminia SJ, Russell P.
    Journal: Exp Eye Res; 1997 May; 64(5):667-74. PubMed ID: 9245895.
    Abstract:
    Two constructs of transgenic mice, TG61 and TG72, containing the HIV-1 protease linked to the lens alpha A-crystallin promoter develop cataract. The TG61 construct develop cataract in utero, while the TG72 construct exhibit frank opacities on the 24th day (homozygotes) and 26th day (hemizygotes) post natum. Polarized light scattering measurements were performed on cortical and nuclear sections of TG72 lenses from day 19 to day 26 as a function of scattering angle. The parallel components of the scattered light intensity increase gradually during opacification, the perpendicular components show very low values from day 19 to day 22 after which they increase exponentially. Analysis of the scattered light intensities yielded parameters describing the size of the protein aggregates, the size of the domains exhibiting optical anisotropy/birefringence, the difference in refractive index between (a) the protein aggregates and their surroundings and (b) the birefringent units and their surroundings. The last parameter accounts for the major portion of the increase in lens turbidity. The TG72 construct shows normal lens development on day 16. By day 21 the posterior cortex shows some disintegration, while the lens is still clear. By day 26 the lens nucleus migrates toward the posterior pole and there is a major alteration in the cortical fibers. Scanning electron microscopic studies reveal normal fiber cell organizations in control animals. In the TG72 construct the fiber cells are well organized at 16 days after birth but already develop some slight separation in the posterior cortical part of the lens. By post-natal day 21, the nucleus and the anterior cortex still exhibit well aligned fiber cell organization, but the posterior cortex shows disalignment. By day 26 in the TG72 construct, all areas of the lens show complete disintegration of the fiber cells and amorphous masses are present throughout. The light scattering parameters describing changes on the nanometer scale can be correlated with the changes in lens morphology during cataractogenesis that occur on the micrometer scale. In comparison, the light and scanning electron microscopic examinations of the postnatal TG61 construct show that the lens is severely disrupted and contains completely disintegrated fiber cell remnants at an early age.
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