Table 4.

Volume fraction of cell types in 33 islet preparations determined by EM and the theoretical number of cells in an islet equivalent (IE).^*

Parameter	Definition	Mean ± SEM	Range	COV
Average Cell Volume (μm3)
Islet (ν̅IC)	VIC/nIC	805 ± 9	632 – 895	0.07
Non-islet (ν̅NIC)	VNIC/nNIC	679 ± 19	490 – 873	0.16
Total (ν̅TC)	VTC/nTC	745 ± 12	547 – 878	0.09
Size Ratio (ν̅IC/ν̅TC)		1.09 ± 0.01	0.97 – 1.22	0.07
β-Cells in Islets
Cell Volume Fraction (φβIC)	Vβ/VIC	0.865 ± 0.011	0.635 – 0.956	0.07
Islet Volume Fraction (ΦβI)	Vβ/VI	0.612 ± 0.008	0.449 – 0.676	0.07
Islet Cells and Islets
Islet Cells in All Cells (φIC)	VIC/VTC	0.522 ± 0.029	0.195 – 0.892	0.31
Islet in All Tissue (ΦI)EM	VI/(VI + VNI)	0.551 ± 0.029	0.216 – 0.904	0.29
Number of Cells per IE
Number of Total Cells (nIE)		1560 ± 20	1430 – 1980	0.07
Number of β-Cells (nβIE)		1140 ± 15	837 – 1260	0.07
Islet Volume Fraction by DTZ
Islet Tissue in All Tissue (ΦI)DTZ		0.68 ± 0.03	0.30 – 0.95	0.26

^*Symbols are defined in the Appendix.