A 49-year-old man presents with jaundice, nausea, and vomiting. He has a history of chronic alcoholism, and is currently drinking over one bottle of red wine a day. On physical examination, he is jaundiced and pale with a large tender liver. Laboratory data include hemoglobin of 9 g/dL, WBC of 4200/mL, and platelet count of 80,000/mL. His liver enzymes and bilirubin are also elevated. Ultrasound of the abdomen reveals liver enlargement with no bile duct obstruction, a normal size spleen, and no ascites. Which of the following is the most likely toxic effect of alcohol on the bone marrow?