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Biomedical subjects

A Takada

Publications and source records attributed to A Takada.

At least 451 records · Page 25Linked to original sources
PubMed1981

Use of chromogenic substrate S-2251 for determination of plasminogen activator in rat ovaries.

A simple specific and reproducible method for determination of plasminogen activator activity in rat ovaries has been developed by using the chromogenic substrate S-2251. The two steps of enzymatic reactions, i.e. activation of plasminogen and subsequent hydrolysis of the substrate was performed in one step incubation. A linear relationship was observed between the amount of chromogen produced and activator activity in the range of the optical density form 0.05 to 1.20 for 30 min's incubation. Endogenous activity of non-specific proteases, plasmin or plasmin inhibitors which might be contained in rat ovaries turned out not to interfere with the specificity of a standardized assay procedure. Reproducibility was firmly established with coefficient of variation not exceeding 10%. Using this method, a marked increase followed by a drastic decrease in the activator activity was shown with rat ovaries around the time of ovulation after the injection of human chorionic gonadotropin.

Animals↗
PubMed1981

Influence of omega-aminoacids on the activation of the first component of complement at low ionic strength.

Cl, is the first component of human complement, was activated to Cls by diluting human plasma in a solution of low ionic strength. The addition of lysine and its related aminoacids to plasma resulted in inhibition of Cl activation, alpha, omega-diaminoacids such as lysine and ornithine were most effective and omega-aminoacids such as 6 aminohexanoic acid were far less effective. Tranexamic acid which is most potent in inhibition of fibrinolysis among those aminoacids was least effective in the inhibition of Cl activation. omega-aminoacids or their analogues hardly inhibited Cls which had already been activated.

Amino Acids↗
PubMed1980

Interaction of plasmin with tranexamic acid and alpha 2 plasmin inhibitor in the plasma and clot.

Interaction of urokinase (UK) activated plasmin with tranexamic acid and alpha 2 plasmin inhibitor (alpha 2PI) was studied by using a chromogenic substrate (S-2251) and immunoelectrophoresis. Plasma was activated by UK (P + U) in the presence of tranexamic acid (P + U + t) or in the presence of thrombin (P + U + thr) and thrombin plus tranexamic acid (P + U + thr + t). These mixtures were incubated for 10, 20, and 30 min at 37 degrees C, then an aliquot of each mixture was added to S-2251, and incubated for 3 or 10 min at 37 degrees C. Hydrolysis of S-2251 after 3 min incubation was significant in the presence of tranexamic acid or clot formation, thus the presence of tranexamic acid or clot formation enhancing the UK activation of plasminogen in both plasma and clot. Hydrolysis of S-2251 after 10 min incubation was higher in the presence of tranexamic acid than in its absence or clot formation without tranexamic acid. Tranexamic acid seems to be more effective in enhancement of activation of plasminogen by UK than clot formation. Plasmin formed by UK was coexistent with alpha 2PI in the plasma in contrast to a purified system in which alpha 2PI formed a complex with plasmin instantaneously. In an even purified system, clot formation and the presence of tranexamic acid protected plasmin from its inactivation by alpha 2PI to some extent.

Blood Coagulation↗
PubMed1979

Influence of coagulation on the activation of plasminogen by streptokinase and urokinase.

Human plasma was mixed with Ca++ or thrombin, and urokinase (UK) or streptokinase (SK) and a chromogenic substrate (S-2251: H-D-Val-Leu-Lys-pNA) specific to plasmin. The hydrolysis of S-2251 was higher when clot was formed by the addition of Ca++ or thrombin than in the absence of clot. The hydrolysis of S-2251 by euglobulin in the presence of UK was also higher when clot was formed, thus, inhibitors may not be related to the better activation of plasminogen, in the presence of fibrin clot. It may be suggested that plasminogen was better activated by activators (UK and SK) in the clot than in its absence.

Blood Coagulation↗