Frank B. Ablondi

Comparison of certain properties of human plasminogen and proactivator.

Summary Human plasma and highly purified soluble human plasminogen contain the same proactivator: plasminogen ratio. The difference in apparent stability of plasminogen and proactivator was traced to the difference in solubility as effected by the pH of the respective assays. During the autocatalytic conversion of plasminogen to plasmin, proactivator content diminishes as plasmin is formed. A discussion of these observations is presented, wherein it is proposed that human plasminogen and the proactivator of bovine plasminogen in human plasminogen are the same factor.

Mechanism of clot lysis by streptokinase and effects of epsilon-aminocaproic acid.

Summary The effects of ‡-ACA, a potent inhibitor of plasminogen activation, on in vitro pre-formed clot lysis and plasma plasminogen activation by SK have been studied. Complete inhibition of plasma plasminogen activation by ‡-ACA has been demonstrated to occur with little concomitant effect on the dissolution of a clot immersed in plasma. Rate of clot dissolution by SK is shown to be a function of clot plasminogen concentration. Potential clinical applications are discussed.

Studies on Specificity of Streptokinase.

Summary 1. Ability of SK to activate the fibrinolytic system in plasma or euglobulin fractions of various animal species has been studied. 2. Human, cat, dog and rabbit plasminogens were readily activated by SK. Pig, horse and cow plasminogens were much less readily activated. Sheep, guinea pig and goat plasminogens were not activatable by concentrations of SK employed. 3. When SK is able to induce formation of a fibrinolytic system on addition to a given species of plasma or euglobulin fraction, that particular mixture gains ability to activate plasminogen of an animal species not activatable by SK alone. 4. Mixtures of SK and a species of plasminogen in which fibrinolysis or LEEase activity does not occur are incapable of activating plasminogens refractory to SK activation. 5. Addition of plasma from all animal species studied partially inhibits the LEEase activity of a spontaneous plasmin preparation. 6. Possible implications of these findings are briefly discussed.

Use of Copper-Amino Acid Gomplexing for Determining Amino Acid Esterase Activity.

Summary 1. The determination of lysine by reaction with copper phosphate has been described. 2. Within the range of concentrations studied the reproducibility of the method was found to be ± 3.5%. 3. The rate of hydrolysis of lysine ethyl ester by trypsin was determined by measurement of liberated lysine. 4. Application of the method to studies with lysine ethyl esterases and other amino-acid esterases was briefly discussed.