Circadian rhythm of DNA synthesis and mitotic activity in tongue keratinocytes |
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Authors: | García M N Barbeito C G Andrini L A Badrán A F |
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Affiliation: | Instituto de Embriología, Biología e Histología, Fac. de Cs. Médicas (60 y 120), U.N.L.P., La Plata, Argentina. carmar@netverk.com.ar |
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Abstract: | Tongue keratinocytes have a high mitotic index (MI) with an evident circadian variation. Our study set out to compare and contrast two phases of the cell cycle: DNA synthesis (S-phase), with inmunocytochemical detection by bromodeoxyuridine (BrdU), and mitosis (M-phase), by the colchicine-arrest of metaphase method, exploring both the dorsal and ventral surfaces of the mouse tongue throughout a circadian period. Adult male mice standardized for light periodicity used for MI experiment were injected intraperitoneally with colchicine. Other animals were injected intraperitoneally with 5-BrdU for S-phase determination. Animals given both treatments were divided into six groups and killed at 4 h intervals until 20:00 h. Tongue samples were processed for histology and immuno-histochemistry. S and M indices were expressed as labelled nuclei or colchicine metaphases, respectively, per 1000 nuclei. Peak MI occurred at 12:00, with the minimum value at 20:00 on dorsal and ventral tongue surfaces. Peak S-phase was at 04:00, whereas the minimum value was at 16:00 for both surfaces. These results show that the proliferative activity of the tongue epithelium is of similar intensity and temporal distribution on both surfaces. |
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Keywords: | circadian rhythms DNA synthesis mitotic activity tongue keratinocytes |
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