The expression patterns of cyclin D3 and cyclin B1 differ in PB- and CB-derived MKs.

Immunofluorescence analysis by confocal laser microscopy revealed up-regulation of cyclin D3 in PB-derived MKs (green, right panels) from day 5 to the end of the culture. In CB-derived culture (green, left panels) cyclin D3 was evident at day 9 in only 5% of the cells and reaching not more than 50% at day 12. Cyclin B1 immunofluorescence expression at nuclear level decreased at late endomitotic stage (from day 9) in PB culture (red, right panels), whereas its expression was constant in whole CB cultures (red, left panels). A total of 300 cells per slide were enumerated. These expression patterns were confirmed in 2 other experiments. (Bar = 10 μm.)