Fig. 2.

The percentage change of lineage-labeled ciliated cells fits to a first-order exponential decay function. A–C: the data points are the mean percentage of lineage-labeled ciliated cells ± SE. Exponential decay functions (curves) were fitted to these data by regression analysis. Half-life of the ciliated cells was estimated from the fitted equations to be 6 mo in the trachea (A), 17 mo in the bronchioles (B), and 14 mo in the terminal bronchioles (C). D: plotting the natural log of the percentage of lineage-labeled ciliated cells against time converts the exponential curves to straight lines.