Preadipocytes were thawed and expanded in T-75 flasks. When needed, the cells were lifted off with 10 % trypsin solution and suspended in DMEM + 10 % FBS for counting. Hemacytometers (both chambers) were loaded and counted by four trained people. Four squares were counted in each chamber, and the results were averaged. The number of cells/mL was calculated, and this number was noted as the cell count for that person. The results were recorded, and the coefficient of variation was calculated for each sample. The Coulter Counter was calibrated using CC Size Standards, settings were programmed, a background was run before each counting session, and duplicate samples of control beads were counted. Four Acuvettes were filled with 20 mL Isoton® solution. The cell suspension was carefully inverted several times, and 200 μL was removed with a micropipette and carefully added to the Isoton® in the Acuvette. Each Acuvette was then gently inverted for 30 s to mix the sample. Prior to counting with the Coulter Counter, each sample was inverted twice to ensure a good cell suspension. Each sample was counted twice, and the counts were averaged to determine the actual count for that sample. The results of both the hemacytometer and Coulter Counter counts, as well as the calculated coefficient of variation for each sample counted, are summarized in Table 19.2. Although the coefficient of variation (C _v) between the two methods of counting was significant (P<0.05), of the six samples counted, the differences between the hemacytometer count and the Coulter Counter count of five samples were not significant (P>0.05). There was a significant difference between the two counting methods on one count (number 5; P<0.05).