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Karen M Pastos

Publications and source records attributed to Karen M Pastos.

3 recordsLinked to original sources
PubMed2006

Differential effects of recombinant thrombopoietin and bone marrow stromal-conditioned media on neonatal versus adult megakaryocytes.

Umbilical cord blood (CB) is a valuable source of stem cells for transplantation, but CB transplantations are frequently complicated by delayed platelet engraftment. The reasons underlying this are unclear. We hypothesized that CB- and peripheral-blood (PB)-derived megakaryocytes (MKs) respond differently to the adult hematopoietic microenvironment and to thrombopoietin (Tpo). To test this, we cultured CB- and PB-CD34(+) cells in adult bone marrow stromal conditioned media (CM) or unconditioned media (UCM) with increasing concentrations of recombinant Tpo and compared the effects of these conditions on CB-versus PB-MKs. PB-MKs reached highest ploidy in response to UCM + 100 ng/mL rTpo, and the addition of CM inhibited their maturation. In contrast, CB-MKs reached highest ploidy in CM without rTpo, and high rTpo concentrations (> 0.1 ng/mL) inhibited their maturation. This is the first evidence that human neonatal and adult MKs have substantially different biologic responses to Tpo and potentially to other cytokines.

Adult↗
PubMed2004

Reticulated platelet percentages in term and preterm neonates.

OBJECTIVES: The authors aimed to determine whether their reticulated platelet percentage (RP%) analysis technique was suitable for use in term and preterm neonates and to characterize RP% values among nonthrombocytopenic neonates. METHODS: The authors modified a whole blood method that uses dual-color CD41 staining for platelet gating and thiazole orange for RNA content, combined with RNase treatment of half the sample to subtract non-RNA fluorescence. The RP% was measured in samples from 10 healthy adults and then a longitudinal study was performed in 15 nonthrombocytopenic preterm neonates on days of life 0 to 1, 2 to 5, 6 to 10, and then weekly until day 28. The authors also performed a cross-sectional study of RP% in 22 nonthrombocytopenic neonates of different gestational age (GA) and postconceptional age (PCA). RESULTS: Overall, neonates had a higher RP% (2.7 +/- 1.6%) than adults (1.1 +/- 0.5%; P < 0.01). In preterm neonates, an increase in the RP% occurred between days 0 and 1 (3.3 +/- 1.3%) and days 2 and 5 (5.1 +/- 1.8%; P = 0.003). By days 6 to 10, the RP% decreased to 3.2 +/- 1.1% and remained unchanged throughout the rest of the study period. In neonates less than 7 days old, an inverse relationship was observed between RP% and GA (n = 20, r = -0.70; P = 0.0005). A correlation between RP% and PCA was not seen in neonates 7 days of age or older. CONCLUSIONS: This method for determining RP% is suitable for use in term and preterm neonates. In preterm infants, the RP% significantly increases over the first 2 to 5 days of life and then decreases to a stable level over the first 28 days. RP% is generally higher in neonates than in adults. Among preterm infants in the first week of life, the RP% is inversely related to GA.

Adult↗