Impaired recovery of Rs1 mice after acute hematopoietic injury. Nine-week-old control (Ctrl) and ColI(2.3)⁺/Rs1⁺ (Rs1) mice (n = 6 per group) were used to start these experiments. (A) Hematopoietic recovery after a single injection (150 mg/kg) of 5-FU. Blood was sampled and analyzed by automated complete blood count for the indicated populations. Plt indicates platelets; and myeloid subsets, eosinophil/basophil/neutrophil/monocyte. (B) Forty days after the first 5-FU injection, mice were injected every 7 days with escalating doses of 5-FU (ranging from 180 mg/kg to 250 mg/kg, as indicated) and followed for survival. Data are mean ± SD. *P ≤ .05. **P ≤ .01. ***P ≤ .001.