Abstract
Two calves received 48 hours of extracorporeal irradiation of the circulating blood (ECIB) immediately prior to cannulation of the thoracic duct and administration of a single intravenous injection of 3H-thymidine. Lymph samples were then removed at short time intervals during 24 hours and smears from sedimented cells were processed for autoradiography. For different groups of mitotic figures classified according to size, cytoplasmic-nuclear ratio and degree of cytoplasmic basophilia, the variation of the mitotic labeling index (MLI) and of the mean grain count per labeled mitotic figure (MGC/LMF), as a function of time after a single injection of 3H-thymidine, was analyzed. Based on the pooled data obtained from the two animals, it was found that tinctorial properties of the cytoplasm permit differentiation into at least two populations of lymphoid cells in the thoracic duct of the calf: one of more basophilic cells with a mean DNA synthesis time of 4 hours and a mean generation time of 5½ to 6 hours and one or more populations of less basophilic cells with longer DNA synthesis and generation times.
