Effect of hyperthermia on murine myeloid precursors

Murine bone marrow was exposed to hyperthermia temperatures of 41.5 to 45.5 degrees C. The proliferation capacity of myeloid progenitor and committed precursors was assayed in vivo utilizing spleen colony formation and diffusion chamber (DC) techniques. The survival of both pluripotential (CFU-S) and committed myeloid (CFU-DG) stem cells decreased exponentially with an increase in the heating period. Progression from CFU-S to CFU-DG significantly altered thermal sensitivity in the temperature range examined. Proliferation of mature granulocyte-monocytes (G-M) in DC is more thermostable than their stem cell precursors. Heat inactivation energies (enthalpies) of CFU-S and CFU-DG were derived from the slope of the heating time survival curves. Enthalpy of CFU-S is 300 kcal/mole below 43 degrees and 105 kcal/mole above 43 degrees. The enthalpy of CFU-DG is 250 and 145 kcal/mole below and above 43 degrees, respectively.