Comparison of young and mature thrombocytes. (A)Measurement of receptor densities of young and mature thrombocytes. (i) From left to right, this panel shows a representative bright field image, TO fluorescence (green), and TRITC fluorescence (corresponding to expression of GPIb) of a young thrombocyte (shown by black arrow). A mature thrombocyte is shown by a red arrow. Bar graph shows the relative levels of GPIb (TRITC fluorescence) on the TO-positive young and TO-negative mature thrombocytes (data collected from 20 different thrombocytes from multiple images shown as n = 20). (ii) From left to right, this panel shows a representative bright field image, DiI fluorescence (red), and FITC fluorescence (corresponding to expression of GPIIb) of a young thrombocyte (shown by arrow). Bar graph shows the relative levels of GPIIb (FITC fluorescence) on the DiI-labeled young thrombocytes and mature (non-DiI) thrombocytes (data collected from 18 different thrombocytes from multiple images shown as n = 18). (B) Measurement of functional activity of young and mature thrombocytes by annexin V binding and P-selectin levels. (i) From left to right, this panel shows a bright field image, green annexin FITC fluorescence (corresponding to expression of phosphatidyl serine), and DiI fluorescence of a young thrombocyte (shown by black arrow). Orange fluorescence in the annexin-FITC image is due to dual labeling of the young thrombocyte by FITC and DiI. Bar graph shows the relative levels of phosphatidyl serine (FITC fluorescence) on the DiI-labeled young thrombocytes and mature (non-DiI) thrombocytes. Mature thrombocytes are shown by red arrows. (ii) From left to right, this panel shows a bright field image, TO fluorescence (green), and TRITC fluorescence (corresponding to expression of P-selectin) of a young thrombocyte (shown by black arrow). Bar graph shows the relative levels of P-selectin (TRITC fluorescence) on the TO-positive young and TO-negative mature thrombocytes. A mature thrombocyte is shown by a red arrow.