Analysis of relative retroviral receptor expression. RT-PCR was performed on RNA from heart, different hematopoietic cell lines, and hematopoietic CD34 cells and CD34⁺ CD38⁻ cells in humans and CD34⁺ cells in baboons. Samples were electrophoresed on nondenaturing gels and either stained with ethidium bromide (A) or exposed to x-ray film (B) and analyzed by densitometry. The predicted DNA fragment for the amphotropic receptor is 182 bp and for GALV receptor, it is 149 bp.