Nuclear pores regulate the passage of substances into and out of the nucleus. Antibodies such as mab414 have been used to inhibit the movement of substances through the nuclear pores of rat liver cells. Scientists cultured rat liver cells (eukaryotic) and bacteria cells (prokaryotic) in separate dishes with radioactively labeled amino acids. A specific gene in both cell types was engineered to synthesize identical polypeptide chains, and translation of this gene was measured. The procedure was repeated with mab414 (the inhibitor) added to each of the two cell cultures, and translation was monitored again.