SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The amount of platelet factor 3 (PF3) activity expressed in stored platelet concentrates (PC) was measured in conjunction with extracellular LDH levels. Standard manual techniques for preparation of PC resulted in PF3 and LDH levels remarkably higher than those observed in PC prepared by apheresis or special manual plateletpheresis. During storage of PC, PF3 activity rose 2- to 10-fold, while LDH levels rose less than 2-fold over starting values. Loss of LDH and appearance of PF3 expressed as a percent of total per platelet were significantly correlated only in standard, manual PC. Approximately half of the PF3 activity observed in any type of PC remained in the supernatant plasma after centrifugation. Upon gel filtration, the supernatant PF3 activity eluted in a high molecular weight peak containing phosphate and light-scattering material. Our findings indicate that platelets in standard, citrated PC express PF3 in amounts that approach that of frozen-thawed (lysed) platelets; however, the manner in which the PF3 activity appears suggests that stored platelets undergo a combination of activation and damage processes.
Explore the source record for details and available documents.
Platelet activating factor (PAF) derived from antigen-stimulated, IgE-sensitized rabbit basophils acts on platelets to induce aggregation and secretion of their content of granule-bound vasoactive amines. Despite this, PAF did not activate platelet factor 3. In contrast, collagen induced aggregation, secretion and PF3 activation in the washed platelets. Other stimuli (ADP, C3b, thrombin) also initiated both secretion and PF3 activation. A wide dose range of PAC, including those giving maximal secretion and aggregation, were ineffictive in making PF3 available and the possibility that PAF inhibited PF3, or its generation, was also excluded. It is concluded that PAF is a unique stimulus for platelets and that secretion and aggregation are not necessarily accompanied by PF3 generation.
Intact human platelets isolated by gel filtration have been treated with purified phospholipase C. The effect of the enzyme on available and total platelet factor 3 has been tested. The available procoagulant platelet factor 3 was very low. A further small reduction was observed after incubation with phospholipase C when the enzyme was washed away before testing. External attack on platelets by phospholipase C led to a marked inactivation of total platelet factor 3.
Explore the source record for details and available documents.
Lipid-protein particles with platelet factor 3 measured by the Stypven clotting-time test [Hardisty & Hutton (1966) Br. J. Haematol. 12, 764-776] have been isolated from platelet-release supernatant. Starting material was washed platelets, which were released by treatment with collagen. Purification of the particles from other components in the release material was accomplished by gel filtration on Sepharose CL-4B followed by affinity chromatography on poly-L-lysine-Sepharose CL-4B gel. Chemical characterization showed that the particles were composed of 40% protein, 42% phospholipids, 13% cholesterol and 5% triacylglycerols. The phospholipid composition was 38% phosphatidylcholine, 25% phosphatidylethanolamine, 9% phosphatidylserine, 2% phosphatidic acid and 26% sphingomyelin. No carbohydrate was detected. Electron-microscopic studies revealed the presence of membranous particles with diameters between 70 and 170 nm.
Platelet factor 3 assay was used to detect antiplatelet antibodies in thrombocytopenic patients with platelet count less than 100,000/cu.mm. A total of 121 specimens was tested. The results gave a positive rate of 83% (61/74) for idiopathic (immune) thrombocytopenic purpura (ITP), 67% for systemic lupus erythematosus (SLE) and 54% (15/28) for others with & 13% (2/16) without history of blood components therapy. The sera from SLE without thrombocytopenic were also checked for the antibody, and a 14% positive rate was obtained. Patients with ITP with complete remission and normal platelet count were 40% positive. Antiplatelet antibody determination by platelet factor 3 assay is a sensitive and reproducible method. It can be performed in most laboratories and requires no specific equipment.
Platelet factor 3 activity is usually determined by the Stypven method in which factor Xa generation is measured indirectly. The determination is dependent on factors I, II, V, X in the test sample. A coagulation assay for platelet factor 3, which measures the thrombin generation promoted by platelet factor 3, is presented. The test depends on platelet factor 3 only, because factors II, Xa, V, fibrinogen and Ca++ are added in excess. The usability of the new method is shown by platelet factor 3 determinations in patients with various platelet diseases, after ingestion of aspirin and in samples of platelet concentrates before and after storage.
The ratio of kaolin recalcification time in platelet-poor plasma to kaolin recalcification time in platelet-rich plasma appears to provide a more accurate estimate of platelet factor 3 activity than measurement of kaolin recalcification time in platelet-rich plasma alone. This ratio is termed the "platelet activity ratio." Over a fairly wide range the platelet activity ratio appears to follow a linear log-log relationship to platelet count (platelet counts of 12,500 to 200,000). The use of diluted platelet substitute as artificial standard greatly simplifies preparation of (1) standard curves and (2) quality control plasmas. If platelet activity ratio is expressed as a percentage of normal platelet factor 3 activity, the normal range for "total" platelet factor 3 (PF3t) is 60 to 175% and normal range for "available" platelet factor 3 (PF3a) is 14 to 47%.
Anti-platelet antibody determinations by a recently introduced platelet factor 3 assay (Pf-3 assay) were evaluated in 159 specimens from 95 patients who had low platelet counts. As a standard procedure, the 51Cr lysis test (51Cr test) was used. The 51Cr test and Pf-3 assay had an excellent correlation (results agreed for 80.5% of 159 specimens tested). Overall positive results for the 159 specimens were 27.7% by the 51Cr test and 22.0% by the Pf-3 assay. A significantly high incidence of anti-platelet antibodies (71.4%) was found in patients who had received more than 10 units of blood transfusions, in contrast to a non-transfused group, which had an incidence of 6.3%. The difference between transfused and non-transfused groups was significant (x2 = 11.854, p less than 0.001). The Pf-3 assay is easy to perform in most laboratories and yet sensitive enough to detect anti-platelet antibodies that were detectable by the 51Cr test.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The influence of blood platelets on the recalcification time under hirudin was investigated. Contrary to the investigations of whole-blood which reveal a pathological prolongation of the hirudin tolerance test only at platelet numbers under 30,000/mug, a change of the recalcification time under hirudin could also be found in the plasma at higher platelet numbers. The recalcification time increased inversely proportionally with falling platelet number. The shortening of time in platelets rich plasma attributed to the activity of platelet factor 3. Differences in the examinations of whole-blood may be attributed to an erythrocyte activity similar to factor 3. The application of hirudin for determining platelet factor 3 is recommended as a sensible method easily to be performed in practice.
Certain samples of stored platelet concentrates exhibited marked platelet factor 3 activity. This activity was associated almost completely with platelet fragments formed during storage. Platelet concentrates containing high levels of these fragments and hence high platelet factor 3 activity were characterized after storage by alkaline plasma pH values, high levels of extracellular lactate dehydrogenase activity and relatively low cell counts.
Preincubation of human platelet rich plasma with PGI2 in a concentration preventing collagen induced platelet aggregation abolished also platelet factor 3 availability brought about by collagen. Following PGI2 pretreatment no second wave aggregation could be elicited by ristocetin. However, primary aggregation as well as platelet factor 3 activity were only partially inhibited in this case and the inhibitory action of PGI2 was not increased by raising its concentration. Similarly, marked but not complete inhibition of platelet factor 3 availability was obtained when kaolin was used as activating agent.