EFFECTS OF ENVIRONMENTAL TEMPERATURE ON HAEMOPOIETIC STEM CELLS IN THE TAILS OF MICE

Using the endogenous spleen colony assay method of Till & McCulloch (1963), the numbers of haemopoietic stem cells present in the bone marrow in the tails of mice were estimated under different environmental temperatures. Compared to animals kept at 22–26°C, mice transferred to and kept at 36.5°C showed a doubling of colony-forming units in the tail in 1–4 weeks. Exposing them to 8°C caused a significant depopulation to approximately one-third in 3–4 weeks. By transferring the mice from one temperature extreme to another these changes could be reversed. Tail marrow depleted of viable stem cells by X-irradiation was repopulated within approximately 3 weeks in animals kept at room temperature or above but this process was inhibited in the cold.