The elastic constants and ultrastructure organization of regenerated basement membrane (lens capsule)

The regenerated basement membrane of the crystalline lens of the rat has been found to have the following elastic constants: a Young's modulus of elasticity of 0.6 +/- 0.48 X 10(6) N m-2 at low stress and 7.8 +/- 2.0 X 10(6) N m-2 at rupture, an ultimate stress of 19.7 +/- 7.0 X 10(5) N m-2, and a maximum percentage elongation of 33.7 +/- 6.1%. Electron microscopic observations of ultrasonicated fragments of the entire membrane show long filaments in parallel arrays and sheets. The filaments show a periodicity of 3.4 nm and a spacing of 3.2 nm. Electron microscopic observations of regenerated membrane treated with collagenase show a poorly staining matrix with separate short thin and thick non-periodic filaments, their diameters being 1.4 nm and 2.5 nm respectively. In addition, strands project from the ends of filaments with a diameter between 0.5 and 1.0 nm. The reduced ultimate strength and Young's modulus of elasticity at rupture in regenerated membrane as compared with normal membrane is considered to be due to the preponderance of thinner filaments in the former. Normal membrane contains not more than 33% of thin filaments whereas regenerated membrane contains at least 78% of such filaments. A comparison of the diameters of thin and thick filaments indicates that thick filaments are probably composed of five strands while thin ones contain three strands.