Inverse relationship between megakaryocyte buoyant density and maturity

Abstract

We examined the relationship between rat megakaryocyte buoyant density and maturation stage in continuous Percoll density gradients. An average of 88% of megakaryocytes had buoyant densities less than 1.054 g/ml. There was an inverse relationship between megakaryocyte buoyant density and maturation. Morphologically mature forms comprised 90% of the megakaryocytes with buoyant densities of 1.030-1.033 g/ml. In contrast, immature morphology was present in three-quarters of megakaryocytes with buoyant densities of 1.042-1.046 g/ml. These morphological findings were confirmed by [3H]thymidine labelling studies. Cell viability assessed by trypan blue exclusion was highest among more dense megakaryocytes of which the majority were immature. The lowest trypan blue exclusion was found in the less dense, predominantly mature megakaryocytes indicating that these cells are more susceptible to membrane damage during marrow suspension. Megakaryocyte DNA content distributions and platelet antigen levels, determined by two-colour flow cytometry, were also related to megakaryocyte density; the more dense megakaryocytes showed an approximately two-fold higher proportion of 8N cells and less platelet antibody binding than did less dense megakaryocytes. These studies suggest that megakaryocytes can be fractionated according to their buoyant densities into immature and mature populations suitable for molecular studies of differentiation.

Cell State-Specific Cytoplasmic Material Properties Control Spindle Architecture and Scaling

“…Both changes are thought to maintain diffusivity through the heterogenous metaphase cytoplasm. Although differentiation-mediated changes in cytoplasmic properties have been observed [34][35][36][37][38][39][40] , we do not know how these changes directly affect spindle assembly and scaling.…”

“…Differentiation-induced changes in cell function have been correlated with reductions in cellular mass density in a variety of cellular systems [34][35][36][37][38][39] . To test whether in our system cells change their dry mass density (defined as dry mass/volume, see Methods) 29 during differentiation, we measured subcellular distributions of refractive indices using correlative fluorescence and optical diffraction tomography 69 .…”

“…We propose that changes in cellular dry mass density explain the cell state-specific scaling phenotypes in a differentiating system (Figure 7). Indeed, a relationship between decreasing mass density and progressing differentiation has been proposed in many systems, including chondrocytes, keratinocytes, myeloid precursors, and neurons [34][35][36][37][38][39] . Still, it is not immediately evident why and how neurally-differentiating cells would change their mass density, in particular before terminal differentiation.…”

Increased GPIIB/IIIA expression and altered DNA‐ploidy pattern in megakaryocytes of diabetic BB‐rats

“…Bone marrow cells were washed out from both tibiae and femura by flushing 5 ml CATCH-medium through the central cavity of the bone (23)(24)(25)(26)(27). Cells were suspended and isolated by several gently pipetting steps and then filtered through a 100 um steel mesh into a sterile plastic tube (Falcon no.…”