Amplification plot of TPO mRNA (A) and GAPDH mRNA (B) of BM stromal cells in real time by TaqMan RT-PCR method. Total cellular RNA (800 ng, •; 400 ng, ○; 200 ng, ▴; 100 ng, ▵; 50 ng, ▪) extracted from normal human stromal cells was subjected to TaqMan PCR to detect a specific RT-PCR product of TPO mRNA and GAPDH mRNA in real time. The arrows indicated the threshold ▵Rn value obtained by multiplying the standard deviation of Rn- (no template controls) by 6.965. In inserted figures of (A) and (B), mean CT (cycles at threshold) of triplicate (bars represent one SD) was plotted against applied RNA amount.