Human meningeal leukemia in the nude rat: Survival curve. Fourteen nude rats were injected intrathecally with an HPB-ALL cell suspension and died at a median of 36.0 days and mean of 38.7 days postinjection (SEM, 8.6 days). Note that death occurred between 30 and 39 days postinjection (ie, within a range of 10 days) in 77% of the animals (arrows).