Aquaporin 0 (AQP0), a lens-specific protein that is a member of the aquaporin family, comprises more than 60% of the lens fiber cell membrane protein. It has been reported that AQP0 permeates water much slower than other members of the aquaporin family, and that it has the function of cell-to-cell adhesion. The results of this study show that AQP0 permeated ascorbic acid in both in vivo and in vitro experiments, and that there was a difference of permeability between the import and export of ascorbic acid via this channel. These findings suggest that AQP0 in the lens plays an important role in controlling the ascorbic acid permeation, and that this function may be responsible for maintaining the transparency of the lens.

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The degradation of mRNA during the differentiation of epithelial cells into fiber cells in the lens was studied and the lifespan of mRNA in lens fiber cells was estimated. Total RNA extracted from epithelial cells of the lens, fiber cells of the shallow cortex of the lens, and fiber cells of the deep cortex of the lens were used. RNA was more degraded in fiber cells of the deep cortex than in those of the shallow cortex. The expression of about 180 genes was more than 3-fold higher in fiber cells than in epithelial cells. Most mRNAs that were present at high levels in epithelial cells were also present at high levels in fiber cells of the shallow and deep cortex. Genes encoding crystallins and ribosomal proteins were highly expressed in epithelial cells and fiber cells. In addition, RT-PCR revealed that several genes were expressed with whole size even in the deep cortex. Electron microscopy detected ribosomes in differentiated fiber cells, which contained few membrane organelles. These results suggest that some mRNAs are protected from degradation in fiber cells of the lens and that these mRNAs persist for a long time and continue to be translated into proteins.

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Purpose : To study the nucleocytoplasmic ratio of lens epithelial cells from the central portion to the incision edge of the anterior capsule fragment of the lens. Subjects and methods : The study examined 254 cataractous eyes of 234 patients without diabetes (age range, 44-91 years). Extension specimens were made of anterior capsule fragments with adherent epithelial cells obtained from anterior capsulotomy. Specimens were divided into 10 equal sections from the central portion to the incision edge. Nucleocytoplasmic ratio was measured in each section. Results : No significant differences in nucleocytoplasmic ratio were evident between age groups or sections. Conclusion : Nucleocytoplasmic ratio did not differ by either age groups or lens region. This suggests that when cell density is high, the area of both cytoplasm and nucleus is small, whereas the opposite is true when density is low.

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Purpose : To predict corrected visual acuity (VA) and contrast VA in 25% daylight from cataract type and grade. Subjects and Methods : Of the Kanazawa Medical University Hospital patients' and Monzen Eye Study participants' eyes with cataracts, 1,083 eyes of 895 subjects (mean age : 72.2 ± 8.1 years) were randomly divided into two groups [1) developing inferential formula (DIF) and 2) verifying inferential formula (VIF)] and evaluated. Results : In the DIF group eyes, partial regression coefficients were significant (p < 0.05) between cortical, nuclear, posterior subcapsular, and retrodot opacities, and both corrected and contrast VA. As for predictive accuracy in the VIF group eyes, differences between the measured and estimated values were less than ± 0.15 logarithm of the minimum angle of resolution in about 50% of corrected and contrast VA, and actual measurements for corrected VA were highly accurate in the 0.5-0.9-decimal VA group. Conclusion : The findings of this study show that corrected VA and contrast VA can be predicted from cataract type and grade.

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