Induction of M-Ras expression by ConA stimulation of freshly isolated spleen cells. Spleen cells were cultured for 24 hours with or without ConA (5 μg/mL). Total RNA was extracted and RT-PCR amplification was performed as described for Fig 2. Samples where the reverse transcriptase (RT) was omitted were used as negative controls for each condition. The post-PCR products were analyzed in ethidium bromide–stained 1.5% agarose gel.