title: Analysis of time dependent changes of lymphopoietic activity in organ cultures of embryonic chicken thymus.
abstract: The time dependent development of lymphocytes in organ cultures of the thymus obtained from 10-day-old chick embryos was characterized by an initial phase of exponential increase of the number of lymphocytes per thymus followed by a plateau phase with no further increase in cell number. The proportion of cells in DNA synthesis dropped rapidly during the first 10 days of culture. Simultaneously the lymphocytes turned progressively smaller, as evidenced by both cell diameter and dry mass and constituted a homogeneous population of small cells at the end of the culture period. Thymic anlagen partially depleted of lymphoid precursor cells by a short hot pulse with 3H-TdR showed a prolonged exponential phase and reached normal plateau cell numbers 2-4 days later than usual. Furthermore, at least in the first part of the plateau phase, a reduction in the number of lymphoid cells per thymus resulted in a recovery in terms of the cell number which was associateed with increased DNA synthesis. These results are compatible with the regulation of thymic lymphopoiesis in organ culture through a mechanism operating via cell density.
mesh_terms: D000818:Animals; D002455:Cell Division; D002642:Chick Embryo; D004247:DNA / Q000096:biosynthesis; D006410:Hematopoiesis; D007065:Idoxuridine / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D007958:Leukocyte Count; D008214:Lymphocytes; D009924:Organ Culture Techniques; D013936:Thymidine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D013950:Thymus Gland / Q000378:metabolism / Q000502:physiology*; D014316:Tritium
chemical_list: D007457:Iodine Radioisotopes; D014316:Tritium; D004247:DNA; D007065:Idoxuridine; D013936:Thymidine