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Gah-Jone Won, Dougle S Fudge, Vivian Choh; The reversibility of lens-softening actomyosin inhibitors. Invest. Ophthalmol. Vis. Sci. 2014;55(13):750.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work shows that disruption of the hexagonal actomyosin lattice that exists at the posterior surface of the avian crystalline lens leads to softening of the lens. In the present study, the reversibilty of inhibitors on lens stiffness was investigated.
Lenses of 7-day-old White Leghorn chickens (Gallus gallus domesticus) were treated (15 min) with 10 µM of either an inhibitor or vehicle (dimethyl sulfoxide). The inhibitors used were: an actin inhibitor (n=5), a myosin II inhibitor (n=5), and a myosin light chain kinase (MLCK) inhibitor (n=5). After treatment, lenses were placed into a force-compression tester containing Tyrode’s solution, and stiffness was was measured at 1 min, 2 min, 4 min, 8 min, 16 min, 30 min, 1 hr, 2 hr, 4 hr, 8 hr, 16 hr, 32 hr. The resulting graphs of lenticular stiffness as a function over time were fitted to a series of sigmoidal curves that changed in parameter numbers and the information derived from the coefficients, as well as r2, were examined to determine which regression equation best modelled the data.
The effects of all three inhibitors were reversible, with lenses recovering from disruption to actin, myosin and MLCK after 4 hours, 1 hour, and 8 minutes, respectively. Data from compression trials were determined to be best-modelled by 4-parameter sigmoidal regressions (f = y0 + a/(1+e-(x-x0)/b); r2 = 0.73, 0.77, and 0.98, respectively). Actin-inhibited lenses recovered with a slope (b-coefficient) of 572.27, denoting a shallow slope and therefore longer recovery time, as well as total recovery of 2.77 mN/mm (a-coefficient) Myosin-inhibited lenses recovered with a slope of 64.58, and a total recovery of 2.11mN/mm, while ML-7-treated lenses recovered with a slope of 15.28 with a total recovery of 2.07 mN/mm.
For response curves involving the measurement of lens stiffness, the optimal regression is the 4-parameter sigmoid model. Using this model, it is possible to obtain a moderate to high r2 value, in addition to the slope and asymptote coefficients holding true. The 4-parameter sigmoid model reveals that actin-inhibited lenses became the softest and recovered the slowest, while MLCK-inhibited lenses softened and recovered the quickest. Myosin-inhibited lenses were intermediate in both recovery amount and time.
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