Quirks of dye nomenclature. 10. Eosin Y and its close relatives

The long history of eosin Y, eosin B and the methyl and ethyl eosins is recounted as well as their synthesis, the variety of their molecular species and some of the myriad applications of these dyes. Chromatographic techniques are described that reveal the purity or lack of it in commercial samples. Toxicological studies are discussed that suggest that the eosins are virtually non toxic, but efforts to remove them from the environment imply that there may be some risk.     

Alterations in the apparent tissue factor (thromboplastin) expression in HeLa cells by a cellular factor Xa inhibitor

HeLa cells have undetectable tissue factor (thromboplastin) activity when measured by a one-stage coagulation assay. In contrast, these cells accelerated the factor VII-catalyzed cleavage of factor X. The two assays gave similar results after either heating the samples to 100°C for 2 min or exposure to thrombin. Neither of these treatments altered the tissue factor activity of human foreskin fibroblasts, a cell type with high tissue factor activity. HeLa cells contain an inhibitors(s) directed against factor X_a but not thrombin. The inhibitor(s) was inactivated by exposure to thrombin or by heat treatment. Inhibition of factor X_a-catalyzed cleavage of a synthetic peptide was blocked by ethyleneglycol bis(β-maminoethyl ether)-N,N′-tetraacetic acid (EGTA) so the inhibition was apparently dependent on divalent cations. Inhibition was not accelerated by heparin. The inhibitor(s) was not protein C or other serine proteases since it was not inactivated by diisopropylfuorophosphate. The factor X_a inhibitors(s) has been isolated from HeLa cells with an approximate 500-fold increase in specific activity. After SDS-polyacrylamide gel electrophoresis factor X_a-inhibitory activity was recovered from a region corresponding to the major Coomassie-staining band at 43 kDa and in lesser amounts from regions corresponding to 26 and 17 kDa. Cellular inhibitors of coagulation may partially explain the low apparent tissue factor observed in some in vitro cells and may serve a regulatory role in limiting the expression of tissue factor.