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S. R. Topgi, D. K. Williams, K. J. Al-Ghoul; The Terminal Web-Like Structure of Lens Fibers: An Interspecies Analysis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4375.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the interspecies variability of the terminal web-like F-actin structure at the ends of fully elongated, maturing fibers as a function of increasing complexity in lens sutural anatomy.
Lenses with umbilical (chicken), line (rabbit), Y (pig), and developing star (guinea pig) suture patterns were utilized. All lenses were fixed, Vibratome-sectioned, labeled with phalloidin-FITC, and then visualized using confocal microscopy. Both anterior and posterior polar sections were examined to facilitate intra- and interspecies comparisons.
Phalloidin-FITC labeling demonstrated the presence of F-actin at the sutures of all lenses. Chicken lenses (umbilical sutures) showed no defined terminal web-like actin apparatus at either anterior or posterior fiber ends. However, an apparent concentration of actin existed approaching the poles. In contrast, rabbit lenses, which have line sutures, showed a prominent web-like actin structure at posterior but not anterior fiber ends. Pig lenses (Y sutures) displayed a well-defined ‘terminal web’ at both anterior and posterior fiber ends. Guinea pig lenses, which featured developing star sutures having three to five branches, exhibited accumulations of actin at posterior fiber ends. Additionally, some evidence of a web-like apparatus was noted at all fiber ends, however, the excessively convoluted actin profiles of fiber end segments did not allow for differentiation between apparent actin concentrations and the ‘terminal web.’
A terminal web-like actin structure is present in fiber ends adjacent to lens sutures of rabbits, pigs, and guinea pigs, all of which have a very limited accommodative range, but not in chicken lenses which possess a comparatively large accommodative range. Because the ‘terminal web’ in rat lenses functions to stabilize fiber end organization during fiber maturation, it is likely to fulfill a similar role in the above lenses. The data is consistent with the hypothesis that the web-like actin apparatus restricts fiber end movement, thereby contributing to the limited accommodative ability in non-primate, mammalian lenses.
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