Changes of the phenotype of erythroid progenitor cells (BFU-E, CFU-E) and their progenies during early steps of differentiation

Early differentiation processes of human erythroid progenitor cells (BFU-e, CFU-e) have been studied during in vitro proliferation using a panel of monoclonal antibodies with known reactivity on different levels of the erythroid cell line. Two antibodies recognizing structures on BFU-e (VIP-2b, BMA 021), two antibodies reactive with CFU-e and nucleated red cells (5F1, CLB-Ery-3) and one antibody directed against glycophorin A (VIE-G4) were used for this study. Normal human bone marrow cells were induced to proliferation in an erythroid progenitor cell assay and, after different periods of incubation, agar cultures were treated with these antibodies and complement. Thereafter, the remaining erythroid cells were incubated again to continue their proliferation with the same stimulators as before. The changes of the phenotype of BFU-e and CFU-e progenies during in vitro proliferation were determined by the reduction of colony formation in comparison with untreated control cultures. Our results indicate that the loss of HLA-DR antigens and the p45 structure is accompanied by the acquisition of structures recognized by the antibodies 5F1 and CLB-Ery-3. After 5-7 d of incubation BFU-e derived progenies exhibit the same antigenic structure as has been found for CFU-e. Glycophorin A expression could only be demonstrated at a late differentiation stage of the erythroid cell lineage.     

Effects on the buoyant density of rabbit platelets of ADP and agents that increase the concentration of cyclic AMP

Rabbit platelets were aggregated by adenosine diphosphate (ADP), allowed to deaggregate and then separated into density subpopulations by centrifugation through discontinuous Stractan density gradients. Although ADP causes little or no release of the contents of the amine storage granules of rabbit platelets, ADP caused a decrease in platelet density as compared with control platelets subjected to the same procedures except for exposure to ADP. The density change persisted for at least four hours. The apparent size of platelets stimulated with ADP increased initially, but returned to control values during a one-hour period. A similar decrease in platelet density was observed with an albumin density gradient. Under conditions in which aggregation did not occur in response to ADP with ethylenediaminetetraacetic acid (EDTA) in the medium, little or no decrease in platelet density was observed. Agglutination with polylysine did not change platelet density. Thus, not only agents such as thrombin and plasmin that cause the release of the contents of the platelet granules decrease platelet density, but ADP also has this effect. Platelets would be exposed to all of these stimuli during thromboembolic processes, and their effect on platelets may account for the decrease in platelet density observed previously in experiments with rabbits with indwelling aortic catheters. Agents that increase the concentration of cyclic AMP (cAMP) in platelets (PGE1, adenosine, dibutyryl cAMP, forskolin, and papaverine) also decreased platelet density. This effect persisted when the platelets were washed and resuspended in fresh medium and was also demonstrable in plasma. Platelet size was gradually increased by prostaglandin E1 (PGE1) which maintains platelets in a disc shape and does not cause the release of granule contents, indicating that the decrease in platelet density caused by PGE1 may be attributable to platelet swelling.     

Involvement of guanine nucleotide binding proteins in neutrophil activation and priming by GM-CSF

Pre-incubation of human neutrophils with pertussis toxin significantly inhibited the neutrophil-directed biologic actions of granulocyte- macrophage colony-stimulating factor (GM-CSF) in three separate assays: the induction of c-fos mRNA, the enhancement of both platelet- activating factor-induced mobilization of intracellular calcium, and stimulation of leukotriene synthesis by the calcium ionophore A23187. Cholera toxin did not have an effect on the latter two assays. Pre- treatment of human neutrophils with pertussis toxin did not affect the binding of GM-CSF to its surface receptor. These results provide the first evidence that a pertussis toxin substrate plays an important mediatory role in the mechanism of action of GM-CSF.     

Aggregation of mammalian cells expressing the platelet glycoprotein (GP) Ib-IX complex and the requirement for tyrosine sulfation of GP Ib alpha

The glycoprotein (GP) Ib-IX complex mediates platelet aggregation in response to high shear forces by binding von Willebrand factor (vWF) in the plasma. We investigated the possibility that the complex could mediate a similar phenomenon if expressed in nonhematopoietic cells. When agitated on a tabletop shaker, CHO and L cells expressing the full complex formed large aggregates in the presence of vWF and the modulator ristocetin. When the rate of agitation was increased, aggregation occurred without added ristocetin and appeared to require only the application of a physical force. The aggregation was homophilic and temperature-dependent and required a functional ligand- binding subunit of the GP Ib-IX complex, GP Ib alpha. Posttranslational tyrosine sulfation of GP Ib alpha was required for aggregate formation and stability. Thus, aggregation of cells expressing the GP Ib-IX complex is a unique example of a ligand-receptor interaction induced by mechanical forces and demonstrates an important biological role for sulfation of tyrosine residues.     

Oral High-Dose Vitamin D Dissolved in Oil Raised Serum 25-Hydroxy-Vitamin D to Physiological Levels in Obese Patients After Sleeve Gastrectomy—A Double-Blind,Randomized, and Placebo-Controlled Trial

Background

Osteomalacia and cardiometabolic disorders are favored in morbidly obese patients due to an inadequate vitamin D (VD) status. Former trials supplementing orally VD (20–50 μg/day) in crystalline form after sleeve gastrectomy (SG) could not stabilize serum 25-hydroxycholecalciferol levels at predefined concentrations (≥50 nmol/l). We hypothesized that VD in an oily suspension would increase its bioavailability resulting in normal serum VD levels minimizing markers of cardiometabolic risk.

Methods

Morbidly obese patients (n?=?94, BMI 51.8?±?11.5 kg/m²) received orally 80 μg/day VD₃ dissolved in oil or placebo (pure oil) in a randomized, double-blind, parallel-group study for 12 weeks after SG. 25-hydroxycholecalciferol, parathyroid hormone, albumin, alkaline phosphatase, phosphate, magnesium, calcium, creatinine, C-reactive protein, lipids, glucose, and glycated hemoglobin were determined in serum/plasma before surgery and after 4 and 12 weeks of supplementation. Intake of energy, fat, and VD were monitored using a 3-day food record.

Results

Seventy-nine patients were included in statistical analysis. Preoperatively, 77.2 and 40.5 % presented 25-hydroxycholecalciferol levels <75 and <50 nmol/l, respectively. After 12 weeks of supplementation, significantly more patients in the VD group exhibited levels >50 nmol/l (92 %) and >75 nmol/l (68 %) compared to the placebo group (54 and 22 %, respectively). Parameters of mineral metabolism and cardiometabolic risk were not modulated by intervention.

Conclusion

Supplementation of 80 μg/day VD₃ by oil is an effective and safe measure to prevent VD deficiency and to treat a preexisting undersupply in patients after SG. Cardiometabolic risk factors were, however, not affected; probably, higher VD doses might be necessary.

Clinical Trial Registration

This trial was registered retrospectively on November 14, 2014, at the German Clinical Trials Register as DRKS00007143.