Autophosphorylation and autoactivation of spleen protein tyrosine kinase.

Incubation of a highly purified bovine spleen protein tyrosine kinase with [gamma-32P]ATP and Mg2+ resulted in a gradual radioactive labeling of the protein kinase (50 kDa) with no change in the protein kinase activity toward angiotensin II. On the other hand, treatment of the protein tyrosine kinase with an immobilized alkaline phosphatase caused essentially complete loss in the kinase activity, which could be restored by incubation of the enzyme with ATP and Mg2+. By using the alkaline phosphatase-treated kinase, time courses of the protein phosphorylation and the enzyme activation were demonstrated to correlate closely. These results indicate that this protein tyrosine kinase relies on autophosphorylation for activity and that the purified enzyme usually exists in a fully phosphorylated state. The radioactive labeling of the purified kinase during incubation with [gamma-32P]ATP resulted from a phosphate exchange reaction: the exchange of [gamma-32P]phosphate of ATP with the protein bound phosphate as previously suggested (Kong, S.K., and Wang, J.H. (1987) J. Biol. Chem. 262, 2597-2603). It could be shown that the autophosphorylation of phosphatase-treated tyrosine kinase was strongly inhibited by the substrate angiotensin II, whereas the exchange reaction carried out with untreated tyrosine kinase was not. Autophosphorylation is suggested to be an intermolecular reaction since its initial rate is proportional to the square of the protein concentration.

Piretanide: a new synthetic fibrinolytic and anti-platelet agent.

Piretanide, 4-phenoxy-3-(1-pyrrolidinyl)-5-sulfamoyl benzoic acid, a potent diuretic, enhances endogenous plasma fibrinolytic activity after a single dose of 6 mg administered orally. Acceleration of fibrinolytic activity becomes manifest within 1 h, reaches its peak in 3 h and is associated with little change in fibrinogen, however, it is accompanied with diminished urokinase excretion initially. Piretanide does not cause lysis of fibrin in vitro in any concentration. Primary platelet aggregation, induced by adenosine-diphosphate, is inhibited by piretanide, in vivo. In in vitro experiments piretanide leads to effective inhibition of ADP-induced platelet aggregation with complete inhibition at 5 mM concentration. Piretanide, after ingestion of a single dose of 6 mg, causes highly significant decrease of platelet factor-4 release.

Influence of yoga on blood coagulation.

Yoga is known to induce beneficial effects on physiological, biochemical and mental functions in man. Its effects on blood coagulation are not known. A study was conducted in seven previously untrained male adults who underwent a combination of yogic exercises, daily for one hour, over a period of four months. Parameters of blood coagulation were estimated before and after the end of yoga training. The following changes were observed: Fibrinolytic activity increased significantly with a concomitant fall in fibrinogen; activated partial thromboplastin time and platelet aggregation time were prolonged; blood and plasma platelets showed a rise; and both haemoglobin and heamatocrit were raised at the end of the training. These findings suggest that yoga induces a state of blood hypocoagulability. The impact of yoga on prevention of cardiovascular and thrombotic disorders is obvious.

Influence of noise on blood coagulation.

A study conducted in rats exposed to a continuous noise of 110 decibels over a period of 3 weeks revealed development of significantly prolonged bleeding time, higher plasma fibrinogen content, and progressively shorter activated partial thromboplastin time in test animals. These changes suggest a coagulopathy induced by noise stress.

Effect of furosemide on plasma fibrinolytic activity and urokinase excretion.

Plasma fibrinolytic activity, as measured by the fibrin-plate method, is enhanced after a single intravenous administration of 40 mg of furosemide. This effect becomes evident within 30 min and a peak response is attained 6 h after i.v. administration. On successive administration of furosemide, the fibrinolytic effect persists and the second peak becomes manifest again after 6 h. Following the parenteral administration of furosemide there is an initial decrease of urinary urokinase excretion which returns to a normal level after 3 to 6 h. Possible mechanisms which may explain the enhanced fibrinolytic activity after furosemide administration are discussed.

Sodium acetate buffer: a diluent of choice in the clot lysis time technique.

Sodium acetate buffer, 0.12 M, pH 7.4 as a diluent in the low temperature technique of dilute clot lysis time, is more effective in accelerating the velocity of lysis than phosphate buffer of similar pH and molarity. A uniform shape of the clot is maintained throughout the digestion in sodium acetate buffer and the end point of lysis is characteristically marked by an abrupt and sharply defined disintegration. Sodium acetate buffer can be employed advantageously in this technique not only to improve the observation but also to shorten the lysis times.

Fibrinolytic activity at high altitude and sodium acetate buffer.

At high altitude there is a tendency for fibrinolytic activity to be enhanced depending, perhaps, on the duration of exposure and this seems to be a protective mechanism against the development of high altitude pulmonary oedema which is associated with diminished fibrinolytic activity. The fibrinolytic response at high altitude seems to be fluctuated during the process of acclimatisation though being maintained at a plateau higher than that in the plains. It apparently results from hypoxic stress but more likely reflects the physiological response to the hypercoagulable state at high altitude. As clot lysis times in high altitude pulmonary oedema are unusually prolonged an attempt at shortening their observation in the test system is desirable. Sodium acetate, 0.12 M solution with pH 7.4 as a diluent in the low temperature technique of dilute clot lysis time is potentially effective to accelerate the lysis time by approximately 33% compared to phosphate buffer solution of similar pH and molarity. Also the end point of disintegration of clot is more abrupt and sharply defined. Sodium acetate buffer can advantageously replace phosphate buffer as a diluent in this technique.