title: The influence of rate of cell entry to S phase on the labelling index of human buccal epithelium.
abstract: The physiological basis of the circadian rhythm in cell kinetics in human epithelia remains unclear. A 24-h periodicity in the labelling index (LI) of human buccal epithelium has been demonstrated previously. A double-labelling technique in vitro using tritiated deoxythymidine was used here to examine fluctuations in the time spent in S phase (Ts) and the rate of cell entry to S phase (S influx). While the range in Ts values was limited (5.1-6.9 h), influx to S phase ranged from 0 to 1.26% per hour at six different time periods. An increase in the S influx was apparent around 18:00 h leading to a peak LI 4 h later. These preliminary data indicate that the most likely kinetic mechanism related to circadian variations in LI is a variable G1-S influx at this site.
authors.affiliation: Department of Oral Sciences, Glasgow Dental Hospital and School, Scotland.
authors.forename: K A
authors.initials: KA
authors.lastname: Warnakulasuriya
authors.forename: D G
authors.initials: DG
authors.lastname: MacDonald
mesh_terms: D000328:Adult; D001345:Autoradiography; D002453:Cell Cycle; D002467:Cell Nucleus / Q000648:ultrastructure; D002940:Circadian Rhythm; D004847:Epithelial Cells; D006801:Humans; D015603:Keratinocytes / Q000166:cytology; D008297:Male; D009061:Mouth Mucosa / Q000166:cytology*; D016196:S Phase; D013936:Thymidine; D013997:Time Factors; D014316:Tritium
chemical_list: D014316:Tritium; D013936:Thymidine