Kinetics of the initiation of proliferation of transplanted LSKCD34⁻ hematopoietic cells. (A) One, 2, 3, 5, and 7 days after transplantation of 1000 LSKCD34⁻ GFP⁺ or CFSE-labeled cells, videos of the hematopoietic reconstitution were performed in the femurs of 3 different mice. Pictures acquired from videos of the femoral head show one of the few frames that contain single GFP⁺ or CFSE-labeled cells 1 and 2 days after transplantation, a frame that contains 2 CFSE-labeled cells with different fluorescent intensities 3 days after transplantation and frames that contain the numerous single GFP⁺ cells 5 days after transplantation or clusters of GFP⁺ cells 7 days after transplantation cells. Scale bar represents 50 μm. White, blue, and red arrows, respectively, indicate cells with fluorescence intensities more than 100, approximately 80, and more than 150. The fluorescence intensity (relative fluorescence units) of some single CFSE⁺ labeled cells is shown. (B) Relative fluorescence units of individual cells were quantified in all frames (150) of the femoral head 1, 2, 3, 5, and 7 days after transplantation for CFSE-labeled cells and in all the frames (150) of the femoral head 1, 2, and 3 days after transplantation or in an average of 25 frames that are representative of all the frames collected in the femoral head 5 and 7 days after transplantation for GFP⁺ cells. **P < .05; ***P < .001. Graphics show the distribution of relative fluorescent units of each cell present in the analyzed frames and the means of these individual relative fluorescent units. These values, together with the cell number detected and the mean fluorescence above background (which is 60, as shown in Figure 1B), are shown below graphics. For GFP⁺ hematopoietic cells, the indicated cell number corresponds to the number of cells detected in the 25 frames analyzed at day 5 multiplied by 6 as 150 frames were analyzed at days 1, 2, and 3. At day 7, the relative fluorescent units were determined in individual GFP⁺ cells from 25 frames. N.D. indicates that clustering of cells impairs the determination of the total cell number at day 7. The data are representative of those obtained with 3 different mice. Statistical analysis was performed with the 1-way analysis of variance test.