Circadian rhythm of DNA synthesis and mitotic activity in tongue keratinocytes.
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.
Instituto de Embriología, Biología e Histología, Fac. de Cs. Médicas (60 y 120), U.N.L.P., La Plata, Argentina. carmar@netverk.com.ar
M N
MN
García
C G
CG
Barbeito
L A
LA
Andrini
A F
AF
Badrán
D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002940:Circadian Rhythm; D004247:DNA / Q000096:biosynthesis*; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008938:Mitosis; D008940:Mitotic Index; D016196:S Phase; D014059:Tongue / Q000166:cytology* / Q000378:metabolism*
D004247:DNA; D001973:Bromodeoxyuridine