Sedimentation velocity characterisation of the cell cycle of granulocytic progenitor cells in monkey hemopoietic tissue

Buoyant density analysis of myeloid colony-forming cells in germfree and conventional mice

Granulocyte-macrophage colony-forming cells (CFUc), in the bone marrow of germfree and conventioal CBA mice, were compared quantitatively and qualitatively. Cells were separated on the basis of their buoyant density by equilibrium centrifugation in continuous albumin density gradients. CFUc in the density subpopulations were detected by culture in agar containing three different types of colony stimulating factor (CSF). The sources of the CSF were post-endotoxin mouse serum (CSFES), mouse lung conditioned medium (CSFMLCM) and human urine (CSFHU). Mice were removed from the germfree environment and the buoyant density status of their CFUc was examined 1, 4 and 8 weeks later. No difference was found between germfree and conventional mice in the number of nucleated cells per femur or in their modal density. Neither was the number of CFUc per femur different. The cell cycle status of CFUc, as determined by the thymidine suicide technique was not significantly different. Functional heterogeneity was found among the density subpopulations for both groups of mice. This depended on the type of CSF. The density distribution of CFUc was significantly different in germfree mice. There were proportionately more low density CFUc. The mean modal density of CFUc under CSFES stimulation was less by 0.0045 g/cm3 in germfree mice. The removal of mice from the germfree environment resulted in a shift of the distribution to higher densities. The trend was towards the conventional situation. The significance of the buoyant density status of CFUc is discussed.

Characterization of functionally distinct lymphoid and myeloid cells from human blood and bone marrow. II. Separation by velocity sedimentation

Velocity sedimentation in a zonal rotor using gradients of uniform osmolarity was used to separate leukocyte subpopulations from human blood and bone marrow. The separations were performed at high sedimentation rates having the advantage of rapidity over conventional unit gravity separations. Myeloid stem cells (CFU-C) and cells reactive with phytohemagglutinin (PHA), Concanavalin A (Con A), and in mixed leukocyte culture (MLC) were separated and their sedimentation profiles obtained. CFU-C sedimented ahead of lymphoid cells and behind mature myeloid elements. Two distinct marrow subpopulations separated by velocity sedimentation were consistently stimulated by Con A, and variably stimulated by PHA and MLC reactions. Both large cells (predominantly myeloid) and small cells (predominantly lymphoid) from bone marrow were stimulated by Con A in [3H]thymidine incorporation assays. When separated subpopulations showing stimulation by Con A were mixed, inhibition of [3H]thymidine incorporation resulted.

Steroids and hematopoiesis. II. The effect of steroids on in vitro erythroid colony growth: evidence for different target cells for different classes of steroids

Androgenic steroids and their non-androgenic 5beta-H metabolites enhance the number of colonies of hemoglobin synthesizing cells grown from rat bone marrow in response to a standard (0.25 unit/ml) concentration of erythropoietin. The target cells for two steroids were found to be different. Cells influenced by the androgen, fluoxymesterone (fluoxy), resembled cells responding to erythropoietin in their cycle characteristics, as measured by tritiated thymidine suicide, and in their physical characteristics, as determined by velocity sedimentation gradient separation. Cells responding to etiocholanolone (etio) had a much lower tritiated thymidine suicide rate and different sedimentation velocities. Preincubation of marrow cells with etio for two hours was sufficient to enhance erythroid colony growth by 84%, whereas a similar incubation with fluoxy produced no increment. These studies demonstrate that different classes of steroids may influence in vitro erythropoiesis by acting on distinct populations of marrow cells. Fluoxymesterone appears to act through cells already committed to respond to erythropoietin, while etiocholanolone appears to act on a separate, perhaps more primitive population of marrow cells.

Heterogeneity of in vitro colony- and cluster-forming cells in the mouse marrow: segregation by velocity sedimentation

C57BL bone marrow cells were separated on the basis of their sedimentation velocity at unit gravity and cell fractions cultured in agar using three types of colony stimulating factor (CSF). Colony-forming cells separated as a single peak (s equal 4.4 mm/hr) in cultures stimulated by mouse lung conditioned medium (CSFMLCM) or endotoxin serum (CSFES). Cluster-forming cells were separable into two peaks and the majority were larger than colony-forming cells (s equal 5.7 mm/hr). Partial segregation of colony-forming cells was observed according to the morphological types of colonies generated, large cells tending to generate macrophage colonies and small cells, granulocytic colonies. Large colony-forming cells were more responsive to stimulation by CSF than small cells. Human urine (CSFHU) appeared unable to proliferation of most small colony-forming cells. Colony-forming cells appear to be a highly heterogeneous population with intrinsic differences in responsiveness to CSF and with differing capacities to generate colonies whose cells differentiate to granulocytes of macrophages.