Regulation of streptokinase-human plasmin complex by the plasma proteinase inhibitors alpha 2-antiplasmin and alpha 2-macroglobulin is species specific and temperature dependent

Streptokinase-plasmin complex (SkPl) was prepared with human plasminogen. Regulation of SkPl and plasmin by the plasma proteinase inhibitors, alpha 2-antiplasmin (alpha 2AP) and alpha 2-macroglobulin (alpha 2M), was studied as a function of temperature in plasminogen- depleted human plasma, mouse plasma, and solutions of purified proteins. The reaction of plasmin with proteinase inhibitors in human plasma was complete. alpha 2AP was the predominant inhibitor. The fraction of alpha 2M-plasmin recovered was not affected significantly by incubation temperature. In contrast, the reaction of SkPl with human proteinase inhibitors was markedly temperature dependent. The apparent second-order rate constant for the reaction of SkPl with purified alpha 2AP at 37 degrees C (1.5 x 10(2) mol/L-1 s-1) was greater than 150-fold higher than the constant derived at 4 degrees C. In human plasma and in solutions containing mixtures of purified human proteins, alpha 2AP was the principal inhibitor of SkPl. Elevating the temperature enhanced the reaction of SkPl with alpha 2AP and alpha 2M comparably. Equivalent results were obtained when incubations were performed in platelet-rich plasma (PRP) or whole blood. In murine plasma, SkPl reacted readily with the proteinase inhibitors. The principal inhibitor of SkPl was alpha 2M. Maximum reaction between SkPl and murine alpha 2M was observed at 37 degrees C; however, significant reaction also occurred at 4 degrees C. alpha 2 AP was the predominant inhibitor of plasmin in mouse plasma. Reaction of alpha 2AP with SkPl in murine plasma was significant only after the alpha 2M was inactivated with methylamine. These results were not affected by platelets or whole blood cells. We conclude that the thrombolytic efficacy of streptokinase reflects not only the nature of the plasminogen activator complex but also the function of the proteinase inhibitors.     

Malignant fibrous histiocytomas of salivary glands

The light microscopic, immunohistological and ultrastructural findings in two cases of malignant fibrous histiocytoma arising in salivary glands are presented and the features of seven previously reported cases are reviewed. This neoplasm is extremely rare in this site and may pose problems in diagnosis. It has to be distinguished from other spindled cell tumours, in particular from epithelial tumours of predominantly spindled cell pattern; immunohistological markers for histiocytic cells may be of value. The histogenesis of this neoplasm is controversial but our electron microscopic findings support an origin from mesenchymal cells which differentiate along a broad fibrohistiocytic spectrum.     

Total anomalous pulmonary venous connection (TAPVC): A familial cluster of 3 siblings

Total anomalous pulmonary venous connection (TAPVC) is a rare form of cyanotic congenital heart disease (CHD) that occurs when the pulmonary veins drain into a site other than the morphologic left atrium. As with other forms of CHD, TAPVC has been shown to cluster in families and is known to have genetic association. We report on a case series of familial TAPVC in three consecutive siblings. A combination of fetal echocardiography, transthoracic echocardiography, as well as cross‐sectional imaging was utilized in the diagnosis as well as management of each sibling. The third sibling was subsequently found to have a partial deletion in chromosome 15q13.3, which has been rarely associated with other forms of congenital heart disease.     

A Review of Interspecies Toxicity Extrapolation in Birds and Mammals and a Proposal for Long-term Toxicity Data

Terrestrial risk assessments for pesticide exposure is generally based on a limited number of toxicity data. The protection target for these assessments requires an extrapolation from species for which toxicity data are available to other species with unknown sensitivity to be able to protect these as well. Our ability to extrapolate toxicity endpoints between species is a major source of uncertainty in risk assessment. Most analyses of interspecies extrapolation in avian risk assessments have dealt with acute toxicity data. It was suggested that, in the absence of a strong rationale to the contrary, we should assume that reproductive data is at least as variable as acute data and that strategies developed for acute data could be applied to long term toxicity data as well. Considering only the two main bird test species for which reproduction data are available (Mallard and Northern Bobwhite), a comparison of the interspecies standard deviation for both acute and reproduction data suggests that the two are equally variable. Analysis of a very limited data set also suggests that this conclusion holds regardless of which endpoint is triggered in the reproduction study. However, the relative sensitivity of the two species established from acute test data appears to be reversed in the case of reproductive data. In addition there seems to be no reason to believe that bodyweight is a factor in helping birds cope with the rigours of chronic dosing, which is in contrast with the acute dosing situation. This suggests that the best extrapolation technique for reproduction test data should be independent of phylogeny and independent of bodyweight scaling. The simplest such method is the one that was proposed by Luttik and Aldenberg (1995, 1997) for both birds and mammals.     

Vesiculation of sickle erythrocytes during thermal stress

Since it is not known why sickle RBCs tend to undergo microvesiculation, we have investigated their susceptibility to thermal stress. While normal RBCs start to vesiculate at 49.0 +/- 0 degrees C (n = 14), sickle RBCs begin to vesiculate at 47.9 +/- 0.5 degrees C, with a range of 46.5 to 48.5 degrees C (n = 14). This abnormality is reproduced by treating normal RBCs with phenazine methosulfate (PMS), which stimulates the excess intracellular generation of superoxide characteristic of sickle RBCs. For PMS-treated RBCs, there is a strong correlation between membrane protein thiol oxidation and vesiculation temperature (r = .977, P less than .001). The abnormal vesiculation temperature of both unmanipulated sickle RBCs and PMS-treated RBCs is significantly improved by treatment of the RBCs with dithiothreitol. The most dense sickle RBCs are most prone to vesiculation during thermal stress, and they are the subpopulation having the greatest amount of thiol oxidation. We conclude that the tendency of sickle RBCs to vesiculate during thermal stress is further evidence for functional abnormality of the RBC cytoskeleton due to thiol oxidation.