Sergio I. Magalini

Vasopressor effect of synthetic 5-hydroxytryptamine creatinine sulfate in man.

Summary 1. Intravenous injection of 0.3 γ/min. 5-hydroxytryptamine creatinine sulfate (5-HT) caused transitory elevation of local venous pressure; higher doses induced more marked elevation of local venous pressure and, when administered in short period of time, of arterial pressure. Elevation of systemic venous pressure was not obtained even with extremely high doses of 5-HT. 2. Intraarterial administration of 5-HT induced sustained elevation of pressure in the homolateral veins (30 minutes or longer). 3. Elevation of arterial pressure and generalized flushing followed injection into a patient with septal venous-arterial shunt of a dose of 5-HT unable to cause such effect in normal subjects. 4. It is postulated that injected 5-HT is quickly removed from the circulation, perhaps by platelets or by other cellular elements retained in capillary beds and released slowly at a later time.

Failure of Synthetic 5-Hydroxytryptamine Creatinine Sulfate to Enhance Clot Retraction of Platelet-Poor Human Plasma.

Summary Synthetic 5-hydroxy-tryptamine creatinine sulfate failed to enhance clot retraction and prothrombin utilization during clotting of platelet-free human plasma. These results are at variance with recently reported findings.

Studies on Platelets. XVI. Glutamic Oxaloacetic Transaminase Activity of Human Platelets.

Summary 1) Platelets are a source of glutamic oxaloacetic transaminase in human blood. 2) The enzyme is an intimate constituent of platelets, being found principally in a water soluble fraction of platelets after separation of lipoids by ethyl ether.

Platelets XVIII. Relationship of Platelets to Activity of 5-hydroxytryptamine Creatinine Sulfate.∗

Summary 1. 5-hydroxytryptamine cre-atinine sulfate (5-HT) administered intravenously causes significant elevation of the local venous pressure at doses as small as 0.3 γ/min. This effect is not affected by short-time incubation with fresh serum, platelet-rich and platelet-poor plasma. Incubation for 16 hours causes destruction of 5-HT activity. 2. Activity of 5-HT also disappears after incubation for 16 hours with suspensions of washed platelets. Some of the activity, however, can be recovered after total disruption of thrombocytes. Also a protein solution from human platelets exhibits significant venopres-sor activity, while intact platelets are inactive. 3. These findings suggest: (a) presence of natural 5-HT or of substances with veno-pressor effect in human platelets; (b) absorption of 5-HT by platelets upon incubation; (c) strong bondage between 5-HT and platelet constituents.

Cholesterol in seromucoid fraction of normal and pathologic sera.

Summary 1. A fairly fixed amount of free cholesterol and cholesterol esters is found in the perchloric acid soluble (seromucoid) fraction of human serum. Phenomena of co-precipitation or of adsorption are probably responsible for this finding. 2. Seromucoid fraction, total serum cholesterol, cholesterol found in the seromucoid fraction were studied quantitatively in pathologic sera obtained from patients with lymphoma, disseminated malignancies, acute leukemia and from selected patients with liver disease. Seromucoid fraction was elevated in all diseases. Cholesterol found in the seromucoid fraction was relatively increased in sera of patients with lymphomas and metastatic carcinomas; relatively or absolutely decreased in acute leukemias and liver disease. 3. The significance of these findings consisted in the indication of possible effects of perchloric acid on cholesterol-containing components of serum. Such effects seemed to vary from normal to pathologic conditions, thus suggesting the possible future value of this study in the investigation of abnormalities of cholesterol metabolism in disease.