J. Karl Armstrong

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The effects of nonionic polymers on human red blood cell (RBC) aggregation were investigated. The hydrodynamic radius (Rh) of individual samples of dextran, polyvinylpyrrolidone, and polyoxyethylene over a range of molecular weights (1,500-2,000,000) were calculated from their intrinsic viscosities using the Einstein viscosity relation and directly measured(More)
BACKGROUND Rapid clearance of poly(ethylene glycol)-asparaginase (PEG-ASNase) has been reported for up to one-third of patients treated for acute lymphoblastic leukemia (ALL), potentially rendering their treatment ineffective. A 25% occurrence of an antibody against PEG (anti-PEG) was previously reported in healthy blood donors. The objective of the study(More)
The change in long-chain fatty acid composition in maternal liver was studied during pregnancy and lactation in the rat. Maternal liver triglycerides and phospholipids transiently accumulated and were depleted of long-chain fatty acids during pregnancy and lactation. During pregnancy, maternal liver accumulated triglyceride, but triglyceride fatty acid(More)
Despite many years of research, the physiologic or possible pathologic significance of RBC aggregation remains to be clearly determined. As a new approach to address an old question, we have recently developed a technique to vary the aggregation tendency of RBCs in a predictable and reproducible fashion by the covalent attachment of nonionic polymers to the(More)
BACKGROUND Recurrent deep vein thrombosis (DVT) risk factors include a first idiopathic DVT, strongly suggesting the existence of undiagnosed and/or unidentified prothrombotic abnormalities. OBJECTIVES To evaluate the impact of locally increased red blood cell (RBC) aggregation on DVT pathogenesis in a rabbit model. METHODS DVT presence, flow and(More)
BACKGROUND Guidelines for transfusion in sickle cell disease usually define an upper hematocrit (Hct) limit of 0.30 to 0.35 to avoid blood hyperviscosity. In vitro viscosity studies of normal (AA) and sickle (SS) red blood cell (RBC) mixtures in buffer appear to confirm that this Hct limit is optimal for oxygen delivery to vascular beds as judged by the(More)
OBJECTIVE Intraoperative bone hemostasis can be accomplished using surgical beeswax (bone wax). However, bone wax locally interferes with osteogenesis, and its use is avoided when bone fusion is critical. We describe the use of a Pluronic copolymer blend as a biocompatible, absorbable, hemostatic agent. METHODS A rat femur defect model and a femur gap(More)
The present study was prompted by prior reports suggesting that small polymers can affect RBC aggregation induced by large macromolecules. Human RBC were washed and re-suspended in isotonic buffer solutions containing 72.5 kDa dextran (DEX 70, 2 g/dl) or 35.0 kDa poly(ethylene glycol) (PEG 35, 0.35 g/dl), then tested for aggregation in these solutions with(More)
In contrast to the accepted general assumption that polyethylene glycol (PEG) is non-immunogenic and non-antigenic, animal studies clearly showed that uricase, ovalbumin and some other PEGylated agents can elicit antibody formation against PEG (anti-PEG). In humans, anti-PEG may limit therapeutic efficacy and/or reduce tolerance of PEG-asparaginase(More)
The effects of enhanced red blood cell (RBC) aggregation on nitric oxide (NO)-dependent vascular control mechanisms have been investigated in a rat exchange transfusion model. RBC aggregation for cells in native plasma was increased via a novel method using RBCs covalently coated with a 13-kDa poloxamer copolymer (Pluronic F-98); control experiments used(More)