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Biomedical subjects

J Levin

Publications and source records attributed to J Levin.

At least 361 records · Page 20Linked to original sources
PubMed1970

Detection of thrombopoietic activity in plasma by stimulation of suppressed thrombopoiesis.

Rabbits in which thrombocytosis had been produced by five daily transfusions of platelet concentrates had suppressed endogenous thrombopoiesis, as reflected by decreased incorporation of selenomethionine-(75)Se ((75)SeM) into the circulating platelet mass. Rabbits in which endogenous thrombopoiesis had been suppressed by transfusion-induced thrombocytosis were used to detect thrombopoietic activity in rabbit plasma. Thrombopoietic activity was demonstrated in the plasma of both normal and thrombocytopenic donor rabbits. A dose response relationship was observed between the incorporation of (75)SeM into platelets and the dose of plasma administered. Infusion of 20-150 ml of plasma from thrombocytopenic donors increased the incorporation of (75)SeM into platelets from 52 to 107% above control values. A dose response effect also was seen after infusion of normal plasma, but normal plasma produced less effect than comparable doses of plasma from thrombocytopenic donors. Rabbits with transfusion-induced thrombocytosis appear to be more sensitive assay animals for the detection of thrombopoietic activity than animals with normal platelet counts. Changes in the rate of appearance and levels of (75)SeM may primarily indicate changes in platelet protein or platelet size and are apparently more sensitive indicators of the state of thrombopoiesis than are alterations in the numbers of circulating platelets. The results strongly support the concept of a humoral agent, i.e. thrombopoietin, that acts on megakaryocytes to regulate platelet production.

Animals↗
PubMed1969

Thrombocytopenia with absent radius (TAR).

Forty examples (27 from the literature and 13 new cases) of a syndrome of hypomegakaryocytic thrombocytopenia with bilateral absence of the radius have been analyzed. This syndrome is designated in this paper as "thrombocytopenia with absent radius (TAR)". The onset of hematologic complications usually occurs at birth or during early infancy. Thrombocytopenia may be episodic and sometimes is accompanied by leukemoid reactions and eosinophilia. Bone marrow examination reveals decreased and/or abnormal megakaryocytes, with normal myeloid and erythroid precursors. Congenital skeletal deformities include bilateral absence of radius, shortening and deformity of the ulnae, and occasionally absence of all the long bones in the arm. The fingers and thumbs are always present. Other skeletal anomalies are frequent. Cardiac anomalies, particularly the tetralogy of Fallot and atrial septal defects, may be present. Other non-skeletal congenital abnormalities are rare. The prognosis is good if the patient survives to one year of age. The syndrome has been compared to Fanconi's anemia, thalidomide embryopathy, limb-cardiovascular syndrome, and a syndrome of multiple congenital malformations, from which it can be distinguished.

Abnormalities, Multiple↗
PubMed1969

Measurement of thrombopoiesis in rabbits using 75selenomethionine.

Incorporation of (75)selenomethionine ((75)SeM) has been used to study platelet production in rabbits. Radioactivity of platelets was low after the intravenous administration of (75)SeM and rose to a maximum approximately 3 days after administration. Platelet radioactivity was independent of concurrent plasma levels. The life span of rabbit platelets, as estimated with this technique, was 4-5 days. In vivo reutilization of (75)SeM previously incorporated into plasma proteins was not detected. In vitro incorporation of (75)SeM by platelets in platelet-rich plasma was not demonstrated. Acute hemorrhage 24 hr before administration of (75)SeM increased the incorporation of (75)SeM into platelets. Transfusion-induced thrombocytosis reduced the incorporation of (75)SeM to approximately 30% of that observed in control animals. Suppression of bone marrow function with nitrogen mustard resulted in decreased numbers of platelets in the circulation, and a decrease in incorporation of (75)SeM. Delayed appearance of (75)SeM was observed in circulating platelets during recovery from marrow suppression. Injection of 75-225 ml of plasma from thrombocytopenic donors into normal rabbits increased incorporation of (75)SeM into platelets while normal plasma did not have this effect. The rate of appearance of (75)SeM in circulating platelets appears to provide a sensitive and specific method for the study of production of platelets by megakaryocytes. The data suggest more rapid entry of platelets into the circulation, and a sustained increase in incorporation of (75)SeM into platelet protein after stimulation of platelet production. The results are consistent with the concept of a humoral agent (thrombopoietin) that acts on megakaryocytes to regulate platelet production.

Animals↗