The Bleeding Time Is Inversely Related to Megakaryocyte Nuclear DNA Content and Size in Man

Abstract

SummaryThe relation between the bleeding time and the megakaryocyte nuclear DNA content and size was evaluated in eleven consecutive patients with normal steady state thrombopoiesis undergoing thoracotomy. A statistically significant inverse correlation was found between the bleeding time and both megakaryocyte DNA content (r = −0.71, p <0.05), megakaryocyte total size (r = ‒0.58, p <0.05), megakaryocyte cytoplasmic size (r = −0.64, p <0.05) and megakaryocyte nuclear size (r = −0.58, p <0.05). The megakaryocyte total size and the megakaryocyte cytoplasmic size were statistically significantly larger in men than women (p <0.02 and p <0.03 respectively). Changes in the megakaryocytes in the bone marrow are associated with changes in primary haemostasis in normal individuals.

Ectopic expression of cyclin E allows non-endomitotic megakaryoblastic K562 cells to establish re-replication cycles

“…Although the biological signi®cance of polyploidization is not yet fully understood, circumstancial evidence in human thrombocytopoenia (Kristensen et al, 1988;Hegyi et al, 1991) and studies in animals (Kuter and Rosenberg, 1990) suggest that the process by which megakaryocytes increase their nuclear DNA must be regulated in order to e ciently maintain blood platelet counts. In this paper, we have examined the role of the factors that govern the G1/S transition in the establishment of the peculiar cell cycle that results in the re-replication of nuclear DNA without an intervening complete mitosis in megakaryoblastic cells.…”

Megakaryocytes and atherosclerosis

“…Patients with ongoing acute myocardial infarction have a shortened bleeding time [30,311 and an increased platelet volume [32-351 and density [32]. The bleeding time, a measurement of platelet behaviour irz vivo, has been shown to be inversely correlated with megakaryocyte DNA content and size in man [36]. In a study where bone marrow biopsies were taken from patients approximately 18 days after myocardial infarction, it was found that megakaryocyte DNA content and size were increased in these patients when compared with patients admitted with chest pain and no myocardial infarction [37].…”

The origin of platelets enabled the evolution of eutherian placentation

“…MK/P was a quantitative haemostatic advance as small size gave a large increase both in cellular surface area and speed of granule secretion. A further, qualitative, advantage over 2 N thrombocytes is that in response to bleeding megakaryocytes can increase their DNA content rapidly, up to 128 N, producing even more active platelets with increased receptor density, more organelles per unit cellular volume and increased capacity to produce prothrombotic proteins and to reduce bleeding time [41][42][43][44][45][46][47][48][49]. Platelet granules contain about a hundred cargo proteins produced by the megakaryocyte.…”