Fig. 1. Astrocyte cultures transfected with a retrovirus encoding  bcl-x ^Lexpress higher levels of  bcl-x ^Lthan do control astrocytes transfected with a retrovirus encoding β-galactosidase or mock-transfected cells. Cultures were transfected with the indicated retroviral vectors or sham washed, subjected to selection with G418 to eliminate untransfected cells, and allowed to grow to confluence. Sham-transfected cells were not exposed to G418. Cell extracts were prepared from each culture and 30 μg protein was loaded in each lane. (  A ) The result of probing with anti–  bcl-x antibody shows an immunopositive band just under 30 kDa. (  B ) The result of stripping the same membrane and then probing for actin (approximate weight 42 kDa) to verify that the lanes had equal amounts of protein loaded.