Figure 5.

β cell mass in WT and cyclin D2^–/– mice during postnatal development. (A) The β cell mass per pancreas was estimated as the product of the relative cross-sectional area of β cells (determined by quantification of the cross-sectional area occupied by β cells divided by the cross-sectional area of total tissue) and the weight of the pancreas. β cell mass was measured at a postnatal age as indicated. Data are mean values ± SEM of four mice per genotype. In WT mice, β cell mass measurement showed a 4-fold increase by P14. In contrast, cyclin D2^–/– littermates did not show any significant increase in β cell mass in the same period. (B) Body weights of cyclin D2 litters were measured to correspond to the β cell mass measurements during the postnatal period. The cyclin D2^–/– mice weights do not differ from their littermates. (C) The relative β cell mass is calculated as a ratio of the β cell mass to body weight. Data are mean values ± SEM of ten mice per genotype.