Hoa Teuschler

Specific Regulation of Procoagulant Activity on Monocytes INTRINSIC PATHWAY INHIBITION BY CHONDROITIN 4,6-DISULFATE

Hypercoagulability of blood, monocytic infiltration, and changes in pericellular and extracellular matrix glycosaminoglycans (GAGs) are observed in atherosclerosis, inflammation, and neoplasia. In the present studies, monocyte procoagulants and different GAGs including chondroitin sulfate (CS) A, CSB, CSC, CSD, CSE, and heparan sulfate, were tested either in clotting assays with whole plasma or in chromogenic assays with purified coagulation proteases. Procoagulant activity in plasma was inhibited by three of the seven GAGs, including heparan sulfate, CSE, and CSB. In contrast, activity of purified coagulation protease was inhibited only by CSE, and the inhibition was observed with intrinsic (factor VIIIa/IXa) but not extrinsic (tissue factor/factor VII) components. Reciprocal titration experiments with enzyme and substrate and Scatchard type analyses were consistent with concentration-dependent inhibitory interactions between CSE and sites on both factor VIIIa and IXa. On purified phospholipids, CSE concentration resulting in half-maximal inhibition (K) was 5 ng/ml for interaction with factor IXa and >500 ng/ml for interaction with factor VIIIa. The K values were lower for reactions on purified lipid than for reactions on monocyte surfaces and for reactions on resting than on endotoxin-stimulated monocytes. Experiments with CSE oligosaccharides of defined size indicated that the smallest CSE fragment capable of inhibitory activity was composed of 12-18 monosaccharide units. Collectively, these results indicate that factor X-activating reactions are inhibited by GAGs expressed on monocyte membranes. Inhibition is specific with respect to the structure of both the GAG and the activating protease. Lack of inhibition by added CSA, CSB, and CSC in contrast to CSE strongly suggests a direct role of 4,6-di-O-sulfated N-acetylgalactosamine GAG structures in the inhibition of intrinsic pathway protease. These findings also suggest potential pharmacologic use of CSE as specific anticoagulant in the management of prothrombotic states mediated by intrinsic pathway coagulation reactions.

Electrostatic interactions during activation of coagulation factor IX via the tissue factor pathway: effect of univalent salts

Interaction between the Gla-domain of coagulation proteins and negatively charged phospholipid membranes is essential for blood coagulation reactions. The interaction is calcium-dependent and mediated both by electrostatic and hydrophobic forces. This report focuses on the electrostatic component of factor IX activation via the extrinsic pathway. Effective charges during the reaction are measured by ionic titration of activity, according to the Debye-Huckel and Gouy-Chapman models. Rates of activation decrease with ionic strength independently of the type of monovalent salt used to control ionic strength. Moreover, the effect of ionic strength decreases at concentrations of charged phospholipid approaching saturation levels, indicating that membrane charges participate directly in the ionic interaction measured. The effective charge on calcium-bound factor IX during activation on phospholipid membranes is 0.95+/-0.1. Possible sites mediating contacts between the Gla-domain and membranes are selected by geometrical criteria in several metal-bound Gla-domain structures. A pocket with a solvent opening-pore of area 24-38 A2 is found in the Gla-domain of factors IX, VII, and prothrombin. The pocket contains atoms with negative partial charges, including carboxylate oxygens from Gla residues, and has a volume of 57-114 A3, sufficient to accommodate additional calcium atoms. These studies demonstrate that electrostatic forces modify the activity coefficient of factor IX during functional interactions and suggest a conserved pocket motif as the contact site between the calcium-bound Gla-domain and charged membranes.

A Medicare cost comparison of minor cutaneous procedures by surgical setting

BACKGROUND Regulations that cause minor cutaneous procedures to be moved from the physicians office to an ambulatory surgery center (ASC) or hospital may have the potential to unnecessarily increase the costs of these procedures from the Medicare perspective. OBJECTIVE To investigate whether minor cutaneous procedures that could reasonably be performed in the office are being done in more intense settings (ASCs or hospitals), who is performing these procedures in alternative settings, and the cost of higher intensity settings. METHODS Medicare claims data on a number of minor cutaneous surgery procedures performed by various medical disciplines, the location in which the procedures were performed, and the ratio of minor procedures done in each surgical setting by specialty were obtained using the 1992-2000 Medicare Current Beneficiary Survey (MCBS). We used Medicare reimbursements as a measure of the cost of the procedure. RESULTS When compared by surgical setting, the mean charges for each minor cutaneous procedure were greatest when the procedure was performed in the hospital setting and least when performed in the office setting. Owing to surgical setting, dermatologists were the most cost-effective specialists for the performance of minor cutaneous procedures. CONCLUSIONS Regulations that discourage office-based surgery could significantly increase medical care costs.