The Kinetics of Haematopoiesis in the Calf: I. An Autoradiographical Study of Myelopoiesis in Normal, Anaemic and Endotoxin Treated Calves

The mean times of production of labelled marrow segmented granulocytes from calves given tritiated thymidine were 5·77 ± 1·43 days for 3 normal calves, 5·68 ± 1·37 days from calves given endotoxin, and 5·75 ± 1·20 days from calves made anaemic by bleeditig. labelled myeloid mitoses first appeared at 1-5 hr. after tritiated thymidine injection and virtually 100% of myeloid mitoses were labelled by 8 hr. metamyelocytes were labelled in all calves during the period of time (G2) before labelled myeloid mitoses appeared. The mean % of labelled metamyelocytes, during the first hour after tritiated thymidine injection, ranged from 15·5 to 3·5. the mean times of arrival of labelled peripheral blood granulocytes was 7·01 days from 3 normal calves, 6·91 days from 3 calves given endotoxin, and 6·19 days from 3 anaemic calves. The granulocyte arrival time of anaemic calves was found to be significantly shorter than that of normal calves at the 95 but not the 99% confidence level. The peripheral lifespan of the segmented neutrophil from normal calves was found to be 5 hr.