Particular RNA fragments as promoters of leukocyte and platelet formation in rabbits.

Under well-defined conditions, ribosomal RNA from Escherichia coli is fragmented by pancreatic ribonuclease, leading to the appearance of particular RNA fragments. Some of these fragments act as primers for in vitro replication of DNA extracted from blood-cell and platelet-forming tissues. In experimental rabbits they restore in a rapid and harmless way normal circulating leukocyte and platelet levels when these have been drastically decreased by various chemotherapeutic agents mainly used in anticancer therapy. Imbalance between polynuclear and lymphocyte count provoked in rabbits by cyclophosphamide can be rapidly corrected by treating the animal with active RNA fragments.