Microscopic detection of GFP expression in the liver. Expression of GFP in the liver following portal vein injection of either wtGP64, Sendai-GP64/wtGP64, or Sendai-spGP64/wtGP64 lentiviral vectors. Sections from the livers of (A) control (B) wild type GP64, (C) Sendai-GP64/wtGP64, (D) Sendai-spGP64/wtGP64 transduced mice. Low magnification (10×) fields are shown to give a representative view. White arrows indicate hepatocytes and yellow arrows indicate nonparenchymal liver cells. In wild type GP64 injected mice most GFP positive cells are nonparenchymal, in Sendai-GP64/wtGP64 injected mice the proportion of GFP positive nonparenchymal cells is much lower.