Proliferation kinetics of mouse tongue epithelium under normal conditions and following single dose irradiation.
Epithelial proliferation in the ventral surface of mouse tongue follows a pronounced circadian rhythm with a peak in mitotic activity at 10.00 a.m., preceded by a wave of DNA synthesis 8 h earlier. Nearly all cells (85%) pass through G2 and mitosis immediately after the S-phase; they subsequently divide again, usually after 2 or 3 days, indicating cohorts of cells with different G1-duration. The fraction of all nucleated cells comprised in one daily proliferation wave is about 20%, indicating a turnover time of the nucleated cell compartment of about 5 days. Cytotoxic injury by a single radiation dose of 20 Gy causes a steep decrease in cell counts, leading to complete denudation after 9-13 days. The difference between the latent period before ulceration and the tissue turnover time is explained by a marked proliferative activity of the doomed cells. The mitotic index increases steeply after day 1 to three times the control level, but most mitotic figures display gross abnormalities such as multipolar spindles or chromosome clumping. As a consequence cells with abnormal or multiple nuclei appear in the basal layers 3 days post irradiation and subsequently migrate to the upper layers. After denudation the epithelium rapidly becomes restored, with a phase of transient hyperplasia on days 13-14. Normal architecture is regained by day 15. Over the whole healing period the mitotic index remains at a high level, with most of the mitoses appearing histologically normal.
GSF--Institut für Strahlenbiologie, Neuherberg, Federal Republic of Germany.
W
W
Dörr
J
J
Kummermehr
D000818:Animals; D002453:Cell Cycle / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D002465:Cell Movement; D002940:Circadian Rhythm; D004261:DNA Replication / Q000528:radiation effects; D004848:Epithelium / Q000473:pathology / Q000528:radiation effects; D005260:Female; D006965:Hyperplasia; D051379:Mice; D008809:Mice, Inbred C3H; D008940:Mitotic Index / Q000528:radiation effects; D011833:Radiation Injuries, Experimental / Q000473:pathology*; D013280:Stomatitis / Q000209:etiology / Q000473:pathology*; D014059:Tongue / Q000473:pathology / Q000528:radiation effects*