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J. R. REDDAN, C. V. HARDING, N. J. UNAKAR, R. M. BELL; Electron Microscopy of Cultured Mammalian Lenses I. Initial Changes Which Precede and Accompany the Stimulation of DNA Synthesis and Mitosis. Invest. Ophthalmol. Vis. Sci. 1970;9(7):496-515.
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The changes in tissue organization which precede and accompany DNA synthesis and mitosis in rabbit lenses maintained in organ culture were characterized at the ultrastructural level. Lenses were cultured in media which are known to trigger cell division and compare with lenses cultured in media which retain the central epithelium in a state of nonproliferation. Since DNA synthesis and mitosis follow a specific spatiotemporal pattern, specific regions of the epithelium were evaluated at various times of culture. At 1 hour the basal region of the epithelial cells was devoid of the intercellular spaces which typified the 0 hour preparations. Sections from the peripheral region at 3 hours showed extensive and pronounced infoldings of the cell membrane. At 7 hours there was an increase in the number of free ribosomes. After 15 hours intercellular spaces similar to those at 0 hours were observed, the peripheral epithelium was multilayered, and the cells were noticeably elongated. These changes precede DNA synthesis and mitosis which commcence at 22 and 35 hours, respectively. Several of the changes in tissue organization were first noted in the periphery of the lens and subsequently in the central region, and they suggest a relationship between the spatiotemporal pattern of DNA synthesis and mitosis and prior ultrastructural modulations. These changes and additional findings at 22, 31, and 48 hours are correlated with recent observations on the pattern of macromolecular synthesis in the cultured lens. The role of tissue organization and modifications in cell-to-cell relationships in the control of mitosis is discussed.
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