Cyclic Hematopoiesis in Grey Collie Dogs: A Stem-Cell Problem

Studies were made to ascertain the possible basis of cyclic hematopoiesis in thegrey collie. The results of ³H-thymidineand ⁵⁹Fe labeling in conjunction with othermarrow parameters and peripheral countssuggest that the regular periodicity ofblood neutrophil and reticulocyte levelsis caused by a defect at the stem-cell—marrow interface. It is postulatedthat the ebb and flow of hemic cellproduction in the grey collie reflects competition for a limiting number of pluripotential stem cells with the alternatingcompetitive pressure provided by activation and deactivation of a neutrophil feedback circuit from periphery to stem cell.This mechanism can account for the characteristic 12-day periodicity and contributes to the phase difference in thecycling pattern of neutrophils relative toreticulocytes.

Submitted on January 26, 1973 Revised on June 15, 1973 Accepted on June 16, 1973