Autoradiographic evaluation of circadian periodicity in cell proliferation in the periodontal ligament of the young mouse

• Published in: Archives of oral biology Vol. 32; no. 5; pp. 377 - 379
• Main Authors: Singh, I.J., Sandhu, H.S., Tonna, E.A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 1987
• Subjects: Animals; Autoradiography; Cell Division; Circadian Rhythm; Dentistry; Male; Mice; Mice, Inbred Strains; Periodontal Ligament - cytology
• ISSN: 0003-9969; 1879-1506
• DOI: 10.1016/0003-9969(87)90095-1

Five-week-old BNL male mice were maintained on a 12-h light/dark cycle, subcutaneously injected with [ 3H]-thymidine 1 h before death and killed every 3 h for 24 h. Autoradiographs were made from demineralized, paraffin-wax embedded sagittal sections of maxillae. The labelling index was calculated for fibroblast-like cells of the periodontal ligament mesial to the first molar. A bimodal distribution of labelled cells was seen. Labelling index was highest at 0900 h (light period); a second, lower, peak was seen at 2400 h (dark period). Cell proliferation was significantly increased during the light period. The increased activity during the dark period may represent a superimposed secondary, ultradian, rhythm, differences in periodontal cell subtypes or may be related to the feeding and activity cycle of the mouse. Thus there is a 24-h cyclic rhythmicity in the proliferation of periodontal-ligament cells in the mouse.