title: Non-circadian rhythm in proliferation of haematopoietic stem cells.
abstract: The proportion of haematopoietic stem cells (CFU-s) engaged in DNA synthesis was determined by means of the [3H]-thymidine [( 3H]TdR) suicide technique during recovery of bone marrow from the damage caused by a sublethal total body irradiation. In contrast with previous reports the [3H]TdR suicide rate was not permanently increased. It was observed that CFU-s passed through S phase in synchronous waves, following a dose of irradiation of 1.5 Gy. After a dose of 2.6 Gy, there was only one initial wave of increased CFU-s sensitivity to the action of [3H]TdR. Following the depression occurring 26 hr after the irradiation with 2.6 Gy, the proportion of CFU-s killed by the [3H]TdR was permanently increased until 5-6 days after irradiation. Thereafter large differences in the [3H]TdR suicide data were observed among individual mice. Evidence was obtained that individual mice, which had been irradiated by a dose of 2.6 Gy 8-9 days before, had identical values of the CFU-s [3H]TdR suicide rate in the bone marrow from different bones of the lower extremities. The recurrence of the synchronous waves in CFU-s passage through the cell cycle was recorded when the CFU-s population regenerated to only about 10% of its normal value. These waves were obviously not related to a particular time of the day and, consequently, they did not represent the circadian rhythm. It is concluded that the synchronous waves in which CFU-s proliferation occurred reflected the action of the control mechanism on CFU-s proliferation. This mechanism should be endowed with an important systemic component besides locally operating factors.
authors.affiliation: Department of Pathophysiology, Faculty of Medicine, Charles University, Prague, Czechoslovakia.
authors.forename: E
authors.initials: E
authors.lastname: Necas
authors.forename: V
authors.initials: V
authors.lastname: Znojil
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000528:radiation effects; D001854:Bone Marrow Cells; D002455:Cell Division; D002470:Cell Survival / Q000187:drug effects; D003114:Colony-Forming Units Assay; D004247:DNA / Q000096:biosynthesis; D005260:Female; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D010507:Periodicity; D013936:Thymidine / Q000494:pharmacology
chemical_list: D004247:DNA; D013936:Thymidine