Volume Phase Transition of Bovine Vitreous Body in Vitro and Determination of Its Dynamics

摘要

The phase equilibrium property and structural and dynamical properties of bovine vitreous body was studied by macroscopic observation of swelling behavior and dynamic light scattering under various conditions.It was found that the vitreous body collapses into a compact state isotropically or anisotropically depending on the external conditions.The vitreous body collapses while maintaining the shape when the pH(< 4)and the concentration of calcium ions(< 1 mol/L)are changed,whereas it collapses along the orbital axis in a mixed solvent of methanol and water.From observations of the dynamics of light scattered by the vitreous body,intensity autocorrelation functions that revealed two independent diffusion coefficients,D(fast)= 7.8 ± 1.5 x 10 ~ 8 cm~2/s and D)(slow)= 3.8 ± 0.60 x 10 ~(-1)cm~2/s,were obtained.The diffusion coefficients were found to be statistically independent of position within a focal depth range of 1-1.5 mm.Divergent behavior in the measured total scattered light intensities and diffusion coefficients was observed as the concentration of calcium ion approached the critical threshold,1 mol/L.Namely,a slowing down of the dynamic modes accompanied by increased "static" scattered intensities was observed.The divergent behavior in the scattered light intensities and diffusion coefficients was reversible.This is indicative of the occurrence of a phase transition upon calcium ion concentration.