Immunohistochemical staining against neuronal and astrocytic markers (NeuN, GFAP) in brains of rats that died spontaneously from tumor showed no qualitative decrease in signal among the brains treated with BCNU-containing membranes in comparison to the untreated controls, indicating further evidence that direct toxicity of the membranes was not a major factor in their deaths (Fig. 8). The gene discussed is GFAP; the disease is neoplasm.